Understanding NEMA Type 4-4X Panel Coolers for Cabinet Enclosures and the right time to utilize them.
NEMA Type 4 enclosures, equivalent to IP 66 in Europe, resist water sprays and are dust-proof. The 4X version also resists corrosion. Electrical enclosures in corrosive or weathered environments need this standard. NEMA Type 4 or 4-4X rated enclosures require equivalent cooling systems.
Some NEMA Type 4 coolers use an aluminum cover and a stainless steel vortex tube. Others use different metals. Frequent wash downs can corrode the large cover, especially if not anodized. This corrosion comes from residual water. NEMA type 4X units, often made of stainless steel, are more reliable long-term.
NEMA Type 4-4X Requirements
A NEMA Type 4-4X cooler is waterproof, but you shouldn’t submerge it. It must resist heavy water sprays without water entry. UL and ULC rigorously test this for certification. Ensure the cooler has proper approval.
NEMA type 4X coolers undergo rigorous corrosion tests. They face 1200 hours in moist air with carbon dioxide and sulfur dioxide. They also endure 800 hours of salt spray tests. These vortex operated cabinet enclosure coolers, must be dust proof and ice-damage resistant. Often, manufacturers use stainless steel for these devices. Stainless steel best resists corrosion and weathering for the NEMA rating.
Applications for NEMA 4X Enclosures
The range of applications for NEMA Type 4X coolers are many, environments with aggressive conditions to the ability to retain their cosmetic look and maintain functionality under all conditions to which they may be subject. The resistance to corrosion, water sprays and adverse weathering represent three important applications for NEMA Type 4X enclosures.
Corrosive Substances in the Atmosphere
When corrosive gases and vapors are present, NEMA Type 4X enclosures protect electrical equipment and internal devices from contamination and harm. Vortex-operated coolers in particular keep control panels at a slightly positive pressure to keep out contaminated air. Industry examples include wastewater facilities, and factories handling corrosive chemicals.
Corrosion tests may only include certain conditions. Therefore the resistance of seals and the enclosure cooler materials of construction to particularly aggressive chemicals should be verified before using. A NEMA Type 4X enclosure is not suitable for use in hazardous areas where explosive vapors may exist. Such units are of a different design.
Wash Down and Heavy Splashing Areas
A NEMA Type 4X enclosure is ideal in food processing operations when equipment is subject to being washed down with either water or chemical solutions to maintain hygiene standards. It’s also applicable to other facilities that use water sprays like dairies and vehicle cleaning services, and anywhere high-pressure cleaning equipment may be utilized.
In some manufacturing areas, if there is a risk of accidental splashing and contamination of equipment from fluids used during processing, such coolers are ideal. One example is for the pulp preparation locations in paper mills. NEMA Type 4X vortex-tube-operated coolers are especially suitable for use in marine environments where equipment may be exposed to salt water. In marine environments, 316 or 316L stainless steel should be the main construction of Panel Coolers.
All-Weather Outdoor Locations
NEMA Type 4 Panel Coolers are weatherproof and fit for outdoors. However, NEMA Type 3R versions are often cheaper and also outdoor-approved. Specifically, stainless steel NEMA Type 3R or 4X enclosures work well in dusty, wind-abrasive areas. They’re also ideal in hot, humid places like coasts where mild steel corrodes quickly. Using 316L stainless steel designates it as a NEMA Type 4X unit.
Nex Flow manufactures all of their Panel Coolers in stainless steel to offer the best durability for any NEMA Type application: NEMA Type 12 (IP 54), NEMA Type 3R (IP 14) and NEMA Type 4-4x (IP 66).
In modern industrial plants, electronic equipment is used for motor control, and most of not all machines are controlled by PLC’s. The high heat dissipation from electronic equipment exposes control systems to elevated temperatures that make them susceptible to malfunction if too hot, creating unpredictable behavior or failure that could lead to a plant shut-down.
Electrical enclosure temperatures are should be kept well below 106 ºF (41 ºC) to limit the possibility of severe damage to equipment. The heat load from electronic equipment limits the practical use of natural ventilation to cool the electrical enclosures resulting in the adoption of alternate methods.
Fans with Filters
The simplest and often lowest cost solution is to use fans to remove waste heat by circulating ambient air throughout the enclosure. This works provided the ambient air temperature is moderate if the enclosures are well shaded, and when the internal heat generated is low. Filters must be used to keep out dust and debris from the factory atmosphere and need to be cleaned and/or replaced regularly depending on the nature of the plant environment. Normally the cooler air is blown into the bottom of the enclosure, and exits “hot” at the highest point of the control panel. Fans must be sized to provide sufficient airflow to remove the heat generated by the electrical controls.
Again, the use is limited to electrical enclosures with relatively low heat loads, in shaded areas, and where the ambient temperatures are moderate. If the environment is very dusty and even if it contains a lot of oily mist, the replacement of filters can become quite a time-consuming and costly endeavor. This often results in filter neglect, which can create heat removal problems finally resulting in potential damage to the enclosure controls and downtime.
Air-to-Air Heat Exchangers
In difficult factory environments, with moisture, heavy dust is present, and oil or chemical vapor, the cabinet or panel enclosures must be sealed. One method is the use of closed-loop heat pipes. A heat pipe absorbs the heat inside the enclosure and transfers it to the outside using a thermally conductive, phase-changing liquid under a partial vacuum. Heat pipes are used extensively in laptops to remove heat from processors for example. Inside the enclosure, the liquid in the heat pipe absorbs heat and converts it to vapor. This vapor moves to the other end of the heat pipe which is outside of the enclosure, transfers the heat to the outside, and changes back to a liquid. The cycle repeats continuously with no moving parts, which makes air to air heat exchangers a relatively low-maintenance solution. The only components that require electricity are two small fans outside of the enclosure to cool the hot ends of the heat pipes to begin the cooling cycle again.
Although relatively low cost and simple, the cooling application is again limited by the outside ambient temperature in the factory as you cannot cool to a temperature below ambient. Fans involved in cooling the heat pipes still require filters to prevent them from clogging and damage and again, if not replaced, can stop working causing the cooling system to fail.
Air-to-Water Heat Exchangers
If a chilled water supply is available, Air-to-Water Heat Exchangers can offer sub-ambient cooling. The internal components of Air-to-Water Heat Exchangers are normally completely encased within a sealed enclosure, thus providing maintenance-free closed-loop cooling. These systems are ideal for the dirtiest industrial environments where oil mist, dust, and dirt would quickly clog the filters of the earlier mentioned systems. Metal grinding and stamping, automotive brake plants, flour milling, and mining operations are all examples of very nasty environments where the applications for Air-to-Water Heat Exchangers can be applied. Similarly, food processing, especially meat and poultry processing plants where frequent wash-downs are normal, are ideal industries for their use.
A major issue is the quality of the water used. Scale buildup can be detrimental if water treatment is poor or nonexistent rendering such systems unable to remove the heat adequately. With zero discharge regulations in many jurisdictions, water itself is not low-cost anymore and downtime for descaling is a cost that needs to be considered. However, there are some excellent environmentally friendly, and safe descalers on the market such as Alpha Descaler for not only maintenance but also for regular treatment to prevent scale formation.
Air Conditioning the Enclosure
In harsh environments that are also hot and humid and where the enclosure heat loads are high the only workable option is an industrial-grade air conditioner. Traditional air conditioners using chemical refrigerant coolant are designed to work with sealed cabinets and prevent the drawing in of moisture, dirt, or other vapor from the environment. Capacities vary from 1,000 BTU to 20,000 BTU and models are available for standard NEMA 12 enclosures or NEMA 4 and 4X enclosures for harsh and corrosive environments. Options to prevent corrosion in corrosive environments and for outside use in rain and/or snow protection can be used. Due to increasing environmental regulations, new refrigerants have been developed and introduced which have increased the costs of traditional air conditioners along with their development. Costs increase also due to the changing of certain materials such as seals as old seals may be negatively affected by the new refrigerants. Some of these new refrigerants have flammability issues which can be addressed by design changes (again more costly) but have caused concern for their use in some facilities. And, they still have the issue of filter cleaning and/or replacement which – if not done, can cause damage to the air conditioner.
Increasing in use are vortex-tube operated air conditioners. While they require compressed air for use, they use no chemical refrigerant, are simple in design, have no condensate produced, are vibration resistant, keep out the harsh factory environment by slightly pressuring the control panel, and are virtually maintenance-free. There are no external filters as there are no fans to worry about and as long as the compressed air supply is kept clean with proper filtration for the compressed air, these types of air conditioners can work for many years with virtually no maintenance. They are also much more environmentally friendly with no refrigerants and have zero flammability issues. One interesting factor is that in very high-temperature ambient, you can utilize a smaller capacity vortex cooler than you would a traditional air conditioner because a vortex tube operated panel cooler performance is independent of ambient air temperature, unlike a traditional air conditioner. It only depends on the temperature of the compressed air itself. Many vortex coolers like the Nex Flow® Panel Cooler are available for NEMA 12, NEMA 3R (outside use) and NEMA 4-4X enclosures. Nex Flow® has also developed and continues to develop increasingly efficient cooling systems utilizing vortex tube technology and special systems can be made. This type of air conditioner is the most environmentally friendly and user friendly of any air conditioning method.
Enclosure Cooling and Reliability
Reliability is a huge issue in modern times with supply chain issues, lack of adequate labor, and concern over timely responsiveness when issues occur. The greater use of electronics in addition to higher enclosure packing densities has directed the use of enclosure cooling more toward air conditioners. Opting for systems that are better for the environment, and have minimal maintenance is a definite trend. Additional security in large factories is now provided by the installation of remote alarm systems, or by linking the digital controller to a remote web server that can simultaneously monitor several enclosures. This ensures that maintenance personnel is immediately notified of any malfunction to prevent unplanned incidents from becoming plant outages. In smaller operations, monitoring is still primarily by observation. One simple item to assist in monitoring for any heat problem in a control panel is a Temperature Sensing Label supplied with all Nex Flow Panel Coolers. It is placed outside the panel in one top corner and offers a visual indication of potential heat load issues that a passing employee can easily see and then act upon if necessary.
Thyristors and other solid state devices in variable frequency drives generate a large amount of heat up to as much as 6% in some cases, the average for most about 4.5% of rated horsepower. The amount of heat is directly related to the efficiency of the drive.
These solid state units are typically mounted on heat sinks and cooler air is drawn in from the bottom of the control panel and then discharge the hot air at the top of the enclosure.
The removal of this heat under many situations requires the cooling the electrical enclosure and in most circumstances the only viable method is the use of enclosure air conditioners.
Some of these situations are as follows…..
High Panel Temperatures (Over 105 ºF or 40 ºC)
The internal air temperature of an electrical should not exceed 105 ºF (40 ºC) especially as localized temperatures could actually be significantly higher. In fact, the service life of electronic equipment is practically cut in half for every 18 ºF temperature rise above normal ambient temperature.
Near Other External Heat Sources
In applications such as bakeries and steel production, the electrical control panels may be close to very high external sources of heat. A heat source such as a furnace or oven increases the heat load in the drive cabinet enclosure or panel, since the ambient temperature is also elevated. In these locations, only some air conditioner can be effective for cooling an electrical enclosure.
When Exposed to Direct Sunlight
The temperature inside an electrical enclosure situated in direct sunlight will be much higher when exposed directly to solar radiation. Any control panel that sees direct sunlight could absorb up to 100 watts of heat per square foot of surface depending upon the sun’s angle. Reflective paint can deflect much of this solar heat load but, in most cases the temperature inside the enclosure will end up greater than 105 ºF just from the sunlight, without not even considering the additional heat load from variable frequency drives themselves
Higher Level and Mezzanine Floors in Factories
The ambient temperature on a higher level or mezzanine floor in naturally ventilated industrial buildings is usually elevated because hot air is trapped and stratifies under the factory’s roof. The temperature are elevated normally 10 to 20 ºF above the level found on the ground floor. This adds to the heat load in the drive panels to potentially cause premature failure or incorrect operation of the drive. Again, some air conditioner would be required to keep the drive cabinet temperature below 105 ºF.
Corrosive Atmospheres
Electronic equipment is susceptible to corrosion and corrosive atmospheres such as salt spray in marine environments, corrosive chemicals from some production processes, and even particulate containing chemicals that may be in the surrounding air. Drive panels in such environments should have a dust and moisture proof NEMA 4 rating and be provided with a closed circuit enclosure cooling system or some system to keep out the factory environment.
High Humidity Environments
Most electrical drives have a requirement that they are not used in locations where the humidity is high and especially when condensation can occur. In coastal, hot, or humid environments, condensation will easily happen at temperatures close to ambient. A proper enclosure air conditioner will dry the air inside the cabinet, to avoid condensation. If using traditional air conditioners, installing a heater to prevent condensation overnight or during cold periods may be advisable as humidity may stay high and the heating will help prevent the condensation.
Cabinet Enclosure Air Conditioner Best for Variable Speed Drives
The high heat dissipation requirements of variable speed drive panels eliminates the use of simple enclosure ventilation systems in any of the above situations.
However it is ideal for relatively low cost vortex tube operated coolers such as the Nex Flow® Frigid-X® Panel Coolers. These devices are produced in stainless steel to handle any potentially corrosive environment and with bypass systems for continuous purging to keep out harsh atmospheres, designed for NEMA Type 12 (IP54), NEMA Type 3R (IP14), or NEMA Type 4-4X (IP66) for almost any type of control panel.
The intrinsic operation of these cooling systems keeps the control panel humidity low to prevent condensation.
While they may have an increased energy use since they operate on compressed air, this is typically offset by the fact that they do not produce any condensate which may be a disposal cost otherwise, use zero chemicals which can harm the environment and which require costly downtime and replacement, and they automatically create a slight positive pressure inside the cabinet to keep our any harmful environmental air – all with no moving parts and essentially maintenance free operation.
Another saving is because of near zero maintenance and absolutely zero use of filters that need replacement, filters that are costly in material, time and disposal after use.
Taken in total, added energy costs in these applications are offset by savings in maintenance time, materials, less downtime, less replacement, and zero disposal costs.
Air conditioners of various types utilized in the USA or Canada are required to meet certain safety standards with similar requirements in most other parts of the world. This is extremely important for industrial applications where they are used as enforcement but by authorities and within companies themselves is on an increasing trend.
Legal requirements governing the use of electrical equipment may sometimes appear complex, certain compliance requirements are clear and universally apply to electrical enclosure coolers.
The most important are the following:
OSHA and NEC Standards
The Occupational Safety and Health Administration (OSHA) governs safety and health in the American workplace and are used as a guide in many other countries many which have similar regulations. In 1971 the National Electric Code (NEC) was incorporated within the Construction Safety and Health Standards of OSHA and therefore all electrical equipment must also conforms to both the safety requirements of OSHA and the NEC. Vortex tube operated control panel air conditioners operate with compressed air. However, they often use electrically operated solenoid valves and thermostats, either as individual pieces or packaged together and these items themselves must meet these safety standards. If a solenoid valve for example is modified, it may be breaking a code. An example of this is drilling a hole in a solenoid to allow for some compressed air flow into an enclosure to keep it purged of environment air instead of using a separate air line for a bypass.
Local Authorities Having Jurisdiction
The Authority Having Jurisdiction (AHJ) that operates locally in the USA is responsible for enforcing local building codes and ensuring compliance. Many of the codes in force by the local authorities are based on the NEC, also known as the NFPA 70. However, others may add local addendums or use their own specific codes.
In all cases, before an installation can be energized the installation must be signed off by a local inspector mandated by the AHJ.
Increasing Importance of Nationally Recognized Testing Laboratories
To ensure that electrical equipment conforms to the relevant codes is to have the equipment certified by a Nationally Recognized Testing Laboratory (NRTL). This certification will be accepted by the AHJ. There are more than a dozen NRTLs licensed in the USA but the most well-known are UL (Underwriters Laboratory) and CSA (Canadian Standards Association).
Before selecting enclosure cooling equipment, make sure that the equipment has been certified and carries the NRTL certification mark. These testing laboratories do more than just “test”. They ensure that the materials used in the products meet a certain standard of quality. One issue with vortex cooler “knockoffs” for example is not only potentially poor quality, but also the use of below standard materials and parts that require a certain level of testing and approval. Anything below “standard” is risky with anything electrical or electronic.
Specific Canadian Requirements
Enclosure cooling systems sold in Canada must conform to the Canadian Electrical Code Part 1. The Canadian Standards Association (CSA) and certain other testing laboratories such as UL are accredited. There are some variations in test requirements and levels of acceptance between the USA and Canada to distinguish between American and Canadian certifications. UL for example puts a prefix C next to their mark and refers to both the USA and Canada approval. Sometimes both a C and US prefix and suffix is used to identify that the product is tested to the standards of both jurisdictions. It’s important to understand this difference so as to avoid the possibility of installing equipment with the incorrect certification for your region. CSA is based in Canada and again does the same with prefix or suffix identification to indicate approval for one or both jurisdictions. Nex Flow Panel Coolers have been tested and approved by UL to meet both Canadian and USA standards and bear the appropriate mark.
Hazardous Areas
Equipment designed for use in a hazardous area must also be certified as such. Your enclosure cooler must conform to the specific hazardous area rating applicable and must be compatible with the rating of the enclosure on which it is used. Proper wiring and connections should be particularly checked.
NEMA Type Enclosure Rating for the Enclosure and Area
The enclosure cooling system used must have the same or better NEMA Type enclosure rating than the electrical enclosure itself. These NEMA Type ratings indicate the design level of the enclosure and the cooling system. For example NEMA Type 4 enclosures are suitable for applications and environments where the panel is subject to wash down. The vortex cooler (or whatever cooking is used) needs to be same or better for that wash down environment. Europe uses IP ratings. Various sources can provide the IP rating that is equivalent to the North American NEMA Type rating. Vortex Coolers like the Nex Flow Panel Cooler have versions tested and approved for NEMA 12 (IP 54), NEMA 3R (IP 14) and NEMA 4-4X (IP 66) applications.
In the U.S. and Canada, it is mandatory for certain equipment to carry the mark of an approved testing laboratory, and an enclosure air conditioner is on the list. Verify before you buy and be safe by using properly certified parts and equipment.
When costly electrical and electronic equipment that maintains the operation of a factory go down, production stops. Critical servers and security systems that drive production is of primary importance in a manufacturing operation not only for production but even for employee safety.
Maintaining the right temperature inside electrical and electronic cabinets require a reliable cooling system. Elevated ambient temperatures in a factory environment can cause costly system failure.
1. Reliable Cooling systems enhance the useful life of controls. When temperatures rise above maximum operating levels, electrical component life can be reduced significantly. A reliable cooling system keeps the panel temperature below the manufacturer’s recommended maximum value, something simple fans and a building’s HVAC system cannot guarantee.
2. Employee Efficiency is increased. Any company wants employee time spent on improving the business and the bottom line, and not dealing with unexpected breakdowns. While the unexpected does happen those related to control panel shutdown can be reduced dramatically with a reliable cooling system.
3. An Ideal Air Conditioning Systems is Maintenance Free or at Least Minimal. Most cooling systems require regular checks, such as filters on an air conditioned panel. If not changed regularly especially in a dirty environment one of two things can happen: if not changed a dirty filter can cause poor air circulation and overheating or, if the filter is missing, then dirt can get inside an enclosure and coat, and damage controls or at least reduce their lifetime significantly. Too often these things get missed or just ignored due to lack of maintenance time.
4. Prevention is Always Less Costly. Preventative maintenance starts with machines working in a properly controlled environment. Just as people work better in a better environment, so does equipment. Poor temperature control inside electrical and electronic enclosures is damaging both economically and from a safety perspective. The use of an efficient cooling system is both economically more profitable and much safer to personnel.
Let’s go deeper on each of these points.
Reliability is becoming more important as labor costs and even labor shortage increase over time. It is important that ANY product for cooling is reputable both in quality as well for technical support should anything actually go wrong. But it’s more than just the supplier’s reputation. Any product chosen should consider the factory environment in which it is placed. Utilizing a fan to cool the inside of a control panel in a dirty and hot and humid environment without considering the environment in which the panel exists can invite trouble. The manufacturer of the control panel does not always have control or any say in which the panel is placed. If the environment is nasty then that should have a serious impact on the cooling method chosen.
Employee basic responsibility is to keep the plant operating. This means an acceptable preventative maintenance program and not only just responding when a problem occurs. If problems persist, the more thorough investigation should be made. Too often however, the problem is not addressed and much time and cost is spent fixing things over and over. For control panels, if the panel door is consistently “left open” because it’s just too hot inside the enclosure, then it should be addressed. It is not only unsafe to leave electrified enclosures open while operating, it is also in most placed illegal. Addressing these problems expeditiously can only improve the environment overall as well as reduce downtime and other potential problems.
Labor costs are significant in any production operation and labor efficiency is important. Every time an outside service person is brought in, some employee must escort that person in the factory, perhaps spend time while that person goes thru a safety protocol training and of course, there is downtime when maintenance is done. Even if no outside person is needed for service, there is still a downtime cost when maintenance is performed by employees. If labor cost can be optimized by reasonably priced solutions that are relatively maintenance free, it should be done.
Prevention is helped by a properly maintained preventative maintenance program and can be further improved by monitoring. There has been and continued=s to be tremendous advances in monitoring of all sorts of equipment especially rotating equipment such as pumps and motors. But what about control panels? While so much is spent for monitoring other equipment the electrical and electronic enclosure should not be ignored. It is just as important in any production line since it keeps that motor or pump running!
HERE IS A NEX FLOW®SOLUTION especially ideal for hot and dirty environments:
1. Reliable as they do not require electricity to function,
2. Free up Employee Time due to its reliability
3. Essentially Maintenance Free with no filters to change or worry about and even keeps control panels clean by keeping out dirty plant air, and
4. Prevents Downtime due to Overheating by maintaining the proper environment inside a control panel.
Every Panel Cooler comes with a Temperature Indicator sticker that you can put on the outside of a control panel to indicate if the approximate temperature inside the enclosure. Extra stickers can be purchased for other panels. Monitoring does not always need to have a high cost.
Seven Ways to make your Compressed Air Blow off and Cooling More Efficient
The majority of compressed air is used for blow off and cooling despite the push for alternate technologies like blowers simply because it is still the most efficient to use in a given application, either because of inadequate pressure from blowers, space problems or high capital and maintenance costs.
This is the reality and which is why compressed air use continues to grow.
So how can you make your compressed air use more efficient for blow off and cooling?
Look at the compressor room – do you need to address the air supply system efficiency? Can you reduce air compressor unloaded times? A great deal of developments in air compressor technology itself can improve overall supply efficiency which in turn increases end use efficiency. Is it the correct size and type for your factory use? Setting the maximum compressed air pressure to a lower level without harming downstream pressure requirements also reduces costs. Every 10 PSIG pressure reduction saves approximately 5% in energy savings.
Fix leaks- but not just pipe leaks, leaks at worn connectors which should be replaced, stuck auto drains on filters, even unsealed connections to air nozzles, air tools and other compressed air operated equipment. Because leaks also lowers downstream and end use available pressure, just fixing any leaks can help reduce the maximum pressure settings at the air compressors.
Check pressure losses – while your factory main compressed air piping maybe adequately sized to minimize pressure loss to the point of use, all too often the connection from the main line to the point of use utilizes piping or hose that is simply too small causing excess pressure loss. This is also compounded with fittings that are too small for the air requirement aggravating pressure loss. It is too common to measure pressure at the main line of 100 PSIG and only three feet away have losses up to 30% simply because the line size from the main to the application was too small. Always check the air requirement (AND pressure requirement of the air nozzle, air knife, vortex tube, panel cooler or any other end use product and be sure that the connection line is of adequate size.
Proper filtration and dryness – when dealing with compressed air blow off and cooling, devices like engineered air nozzles and vortex tubes require clean and dry compressed air. Any dirt buildup over time and excessive moisture negatively affects performance and can even clog the products. Always use point of use filtration to remove any excess moisture and particulate. Inadequate filtration can not only effect the device, it can also impact the quality of the product where any blow off is used.
Consider on-off control – a huge advantage of compressed air is that it can be stored and used on demand. When not used, it remains stored and energy is not consumed. Utilizing sensors and solenoid valves or a system such as the Nex Flow® PLCFC can take advantage of this storage ability which can yield tremendous energy savings. Many production lines do not need to have the blow off and cooling constantly on.
Consider New Pulsing Technology – pulsing of compressed air not new and solenoid valves have been used for years to do this. The problem with solenoid valves is however the high wear and tear and therefore the cost to maintain them typically offsetting any energy savings. It is also not certain how much energy is saved as other factors come into play when pulsing occurs. However, pulsing provides scrubbing action to help clean surfaces and a “push” to move or loosen a target where necessary. New process valves have, and still are being developed for pulsing to overcome these maintenance costs and offer potential for improved cleaning with engineered nozzles and for energy saving when properly applied. has done some projects with pulsing so has experience needed when using new pulse technology and offers consulting services for this as well as other applications.
Stay informed on new technologies for blow off and cooling but beware of false claims – Nex Flow® and a few other companies do research and development to improve products for blow off, cooling and conveying. Many others just copy, (usually not very well) other’s work and sometimes even claim it as their own. To stay focused, Nex Flow® provides compressed air blow off, cooling and conveying products and stays away from things like spray nozzles. Rather than being a supplier of all things, we specialize and share deep knowledge and experience in what we actually know. This is evidenced by our history of success, continued growth and our unique patents of which there are more to come with ongoing R & D and innovation. Be very careful of product claims that make no sense of product performance, some which even defy the laws of physics. Make sure companies that offer blow off and cooling technology can even afford to get proper approvals where necessary such as for control Panel Cooling to be assured they will stay around to service you (and that the product is even legal!). Reliability, timely response, and quality product and service is always important.
Vortex tubes are ideal for spot cooling and enclosure cooling. Typically one vortex tube is used for one “spot” and for “one” enclosure. But there are some situations where one vortex tube can be split into multiple “spots” as long as one important criteria is kept in mind. Once the compressed air exits the vortex tube it needs to be directed to the area that needs the cooling. When the vortex tube is out in the open, this is achieved by adding a delivery tube, usually flexible tubing to direct the cold air to that spot. When cooling an enclosure, the cold air is sent directly into the enclosure from inside the enclosure. Once the air exits inside the enclosure it can be further distributed around the enclosure thru tubing but all the cold air is input into the enclosure.
Two factors that must be considered when using the cold air produced in a vortex tube: conduction and pressure drop. The general rule it to keep any tubing on an open space vortex tube as short as possible, preferably under 8 inches. One example where a vortex tube has been used in open space for multiple locations is on routing a plastic part. Once Nex Flow Model 50030H vortex tube had the cold air split into two directions and delivered to cool two routers. Rather than using one vortex tube for each router, one larger capacity vortex tube was utilized. If two separate units were used, they could have been smaller capacity units (Model 50015H), each which is ½ the capacity of what was used. What made this work was delivering the air with large (10 mm) tubing to offset pressure drop and keeping the distance as short as possible (under 8 inches to each router). Also, the tubing was insulated to minimize the effect of conducting heat from the surroundings into the tubing, heating up the cold air. There was consideration for using two vortex tubes but there were also space issues with the application.
But this is not a common application. If the distance they had to cool was much longer from the vortex tube, we would have recommended two of the smaller capacity vortex tubes. There is another consideration when considering the use of vortex tubes for multiple location cooling. Let’s take the example above. If the distance from the vortex tube was only a few inches more, to get the same cooling effect at the router, we would have had to use a larger capacity vortex tube, a Model 50040H. That extra 10 SCFM of compressed air use costs energy. That extra energy cost would more than pay for the extra vortex tube in a very short time, and even if used sparingly, certainly in under a year. The increased operating cost, even with minimal use, can easily be equal to or more than the capital cost of one additional unit.
Concerning enclosures, more than once we had to address an issue with cooling when a Nex Flow Panel Cooler, instead of being attached directly to the control panel. Was for some reason mounting off to one side, and a tube was attached to the bottom of the Panel Cooler and then put into the control panel. Needless to say, the unit did not cool as was expected because the cold air heated up several degrees before it reached the control panel. The Panel Cooler has a built in vent to exhaust the displaced hot air inside the cabinet and of course was not used at all when mounted outside. If you are facing any difficulties with installation – please do not hesitate to contact one of our engineers.
Another thing to remember when installing a vortex tube or a vortex tube operated device like the Panel Cooler, onto an enclosure that it must be installed at the top, or if space is lacking, near the top using a side mount. The reason is that cold air falls and hot air rises. The reason a distribution tube is used at the end of a Panel Cooler is to distribute the cold air faster to isothermalize the cabinet (even out the temperature) more quickly. If the vortex tube device is mounted too low, the hot air will tend to stratify at the top of the inside of the enclosure.
When considering any vortex tube operated device – cabinet enclosure cooler, tool cooler, spot cooler, mini cooler or the vortex tube itself, it is best to keep any attachment at the cold end as short as possible when the product is in open space. When attached to an enclosure of any type, the cold air should be directed directly into the enclosure, near or at the top.
Spot coolers are self-contained air conditioning systems that have all the components of larger air conditioning systems but are compact and easy to move. Spot cooling for industrial applications are used short term to cool a small area on a part or in an enclosure – such as a cabinet. Spot coolers are ideal for cooling electronics, computer server rooms, and humans in small confined work environments. They are often praised for their portability, ease of use, and installation.
Fans cannot cool below ambient temperature because they cool by moving air and cool a wider area. Compressed air amplifiers cool better than fans because of the higher velocity but they also do not cool below ambient temperatures. Air amplifiers also cool a wider area. This blog discusses the three most popular ways to cool below ambient temperature, namely Vortex Tubes, thermoelectric, and cryogenic gas (CO2 and Nitrogen Gas) cooling systems.
It is important that the spot cooling system chosen is reliable because sudden or frequent break downs can cause costly equipment damage, repair, or replacement. Keeping humans cool in a small work area is important as well for health and safety concerns. All Spot coolers come with accessories that allow you to direct the cooled air where it is needed most. Any condensation that results from the cooling process is drained through a hose or bucket.
Vortex Tube Cooling System
Vortex Tube Cooling systems are powered by compressed air. The vortex action separates the compressed air into extremely cold and hot streams. The cylindrical form causes the compressed air to rotate at a high speed (reaching 1 million rpm). A small portion of the air exits through a needle valve as hot exhaust. The remaining air is forced through the center of the incoming air stream at a slower speed. The action of the slower moving air dissipates any remaining heat into the faster moving air. The super-cooled air flows through the center of the generator and exits the cold air exhaust. Depending on the temperature and pressure of the incoming compressed air, it is possible to achieve cold end temperatures as low as – 40 and even – 50 degrees F. The hot air (end) can be up to 260° F (127° C). The Vortex cooling system, or cold end of the Vortex Tube, is often used for “spot cooling” of cabinets, such as control panels and industrial cameras.
Vortex Tubes normally come with the “hot end” adjustable to control the flow and temperature out the cold end. The more flow out the hot side, the lower the temperature out the cold side. The cooling effect (BTU/hour) is determined by both flow and temperature drop. Therefore, for cooling applications, the cold end should be between 60% – 80%. If the cold temperature is most important, then the flow out the cold end should be under 50%.
Choosing the best Spot Cooler
Factors in selection:
Vortex Tube cooling systems that use compressed air is considered where conventional enclosure cooling by air conditioners or heat exchangers is not possible. Ideally, Vortex Tube cooling systems are used to cool small to medium size enclosures, nonmetallic enclosures, and areas where the size of cooling devices is restricted.
For optimum cooling results when using a Vortex Tube cooling system, the following items are required when installing:
Clean, dry, oil-free compressed air
80 to 100 PSIG / 70 degrees F or below. Lower pressures and higher temperatures will reduce BTU/H ratings.
A 5-micron water and particulate removal
A 5-micron oil removal filter when oil is present
Thermostats or temperature indicator sticker
Valve (optional)
Muffler go minimize exhaust noise
Advantages:
The Vortex Tube cooling system has many advantages. The small, portable, light weight, and compact system creates extremely cold air without refrigerants, included CFCs or HCFCs. It is exceptionally reliable since there are no moving parts and virtually maintenance free. It uses minimal electricity (only for the compressor). Vortex Tube cooling systems are useful in harsh and high temperature environments. Customers can expect a long life from Vortex Tubes because Nex Flow uses only Stainless-Steel with a brass generator. Compressed air is not the only gas that can be used to produce cold air, Nitrogen and other natural gases that can be compressed can be used as well.
Applications:
Vortex Tube cooling systems can be used to cool:
electronic and electrical control instruments
machine operations/tooling
CCTV cameras
Set hot melt adhesives
soldered parts
gas samples
heat seals
environmental chambers
workers wearing protective gear
data centers
plastic machined parts and molded plastics
Electronic components
It is understood that cold and hot gas (bi-product) is generated when using a Vortex Tube cooling system.
Choosing the best Spot Cooler
Thermoelectric Coolers (Peltier Effect)
Thermoelectric cooling (TEC) became a viable option for spot cooling in the late 1950s with the development of semiconductor materials. The thermoelectric cooler (TEC), often called the Peltier module, is named after Jean Peltierwho discovered heating/cooling effect when passing electric current through the junction of two conductors in the early 1800s. It is a semiconductor-based electronic component that functions as a small heat pump.
Using a low-voltage positive DC voltage to a TEC, electrons pass from one element (p-type) to another (n-type), and the cold-side temperature decreases as the electron current absorbs heat, until equilibrium is reached. The cooling is proportional to the current and the number of thermoelectric couples. This heat is transferred to the hot side of the cooler, where it is dissipated into the heat sink and surrounding environment. The result is a quick and large temperature differential.
Factors in Selection:
To use Thermoelectric spot cooling, a DC voltage required. This type of spot cooling is ideal when refrigerants are not desired, and space is limited. It a cost effective, reliable, efficient way to spot cool. Multiple thermoelectric coolers are connected side by side and then placed between two metal plates. It is ideal for intermittent heating and cooling applications because TEC seamlessly switches between heating and cooling.
Advantages:
Thermoelectric spot cooling has come to dominate certain applications because of the following benefits:
Precise temperature control and stabilization to 0.01 degree C
reliable
noise-free operation
vibration-free operation
scalable
compact
Choosing the best Spot Cooler
Applications:
TEC is used for spot cooling for the following applications:
Telecommunication applications:
980nm and 1480nm Pump Lasers
Digital Transmission Lasers
Planar Lightwave Circuits
Optical Channel Monitors
CATV Transmission Lasers
Avalanche Photodiodes
Wavelength Lockers
Medical samples
Cold storage
Electronic cabinets
Self-powered appliances
Small scale refrigeration
Harsh environmental protection for critical components
Computer microprocessors and robotics
Cabinet cooling
Cryogenic Cooling (Carbon Dioxide or Nitrogen gas)
Cryogenics is the scientific study of materials and their behaviors at temperatures well below conventional refrigeration. The word comes from the Greek cryo “cold” and “genic”, which means “producing”. Cryogenic temperature ranges can be reported using any temperature scale, but Kelvin and Rankine scales are most commonly used because they are absolute scales that have only positive numbers. The U.S. National Institute of Standards and Technology (NIST) considers cryogenics to include temperatures below −180 °C (93.15 K; −292.00 °F), which is a temperature above which common refrigerants (e.g., hydrogen sulfide, freon) are gases and below which “permanent gases” (e.g., air, nitrogen, oxygen, neon, hydrogen, helium) are liquids. At 250 F below zero, many gases are liquid. Below is a list of temperatures where these gases boil.
Fluid
Boiling (Celsius)
Boiling (Fahrenheit)
Oxygen
-183°
-297°
Nitrogen
-196°
-320°
Neon
-246°
-411°
Hydrogen
-253°
-423°
Helium
-270°
-452°
Before the fluid’s temperature rise, all the liquid must boil away and turn into a gas. None of these gases exist naturally as a liquid. Each of the gases are cooled to put them into a liquid state. Latent heat absorption during the phase change from solid to liquid or liquid to gas causes cooling in the immediate area. According to the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), liquid CO2 (LCO2), known as Refrigerant R-744, is the most widely used method used during vaporization of a liquid to a gas. When liquid CO2 is introduced to the system through the nozzle of a spray gun or cooling injector tube on a temperature chamber or thermal platform (cold plate), the liquid quickly turns to solid state CO2 or dry ice. As the dry ice warms up or sublimates (direct change from solid to gas), a great release of the latent heat occurs.
Liquid CO2:
Spot-cooling method uses liquid CO2 injected in controlled pulses through tiny capillary tubes inserted into hard-to-cool areas to the same level as the rest of plastic mold cores. This approach is meant to complement conventional water cooling by ensuring uniform mold temperature without hot spots.
When the cooling cycle begins, LCO2 is fed under high pressure (approximately 850 psi (58.6 bar)) through the thin, flexible stainless-steel capillary tubes with solenoid valves to time injections and to the points where cooling is required. The high sublimation energy of the CO2 from solid to gas phase, along with the resulting cold gas, provides a very high local cooling capacity. The CO2 withdraws heat from the steel of the mold and escapes out of the expansion room in gaseous form through an annular gap between the hole and capillary tube.
Liquid Nitrogen:
Under normal atmospheric pressure, Nitrogen can exist as a liquid between the temperatures of 63 K and 77.2 K (-346°F and -320.44°F). Below 63 K, nitrogen freezes and becomes a solid. Above 77.2 K, nitrogen boils and becomes a gas. Since it is obtained from the atmosphere, liquid nitrogen is inexpensive and is rarely refrigerated. It is kept in insulated containers called Dewars and can boil away.
Advantages:
Given the purity of LCO2 supplied for this application (typically >99.98%), there is little danger of residue build-up or contamination of the hole as there would be with water cooling. Meanwhile, Liquid Nitrogen is colorless, odorless, and tasteless. It is an Inert element that is noncorrosive and does not support combustion, so it is safe.
Disadvantages:
There are several risks involved in cooling using cryogenic cooling systems. There is always a risk of asphyxiation, frostbite, or burns if not used and handled properly. Cryogenic gas has large expansion ratio for evaporation. For example, if one liter of liquid nitrogen can result in 700 liters of gas. If released in a small room, it can fill a room and make it an oxygen deficient atmosphere. It is also not safe to digest. It is essential that all the liquid nitrogen is evaporated before ingested otherwise it can boil and cause damage to internal organs.
Choosing the best Spot Cooler
Factors in Selection:
Cryogenic spot cooling systems are ideal for specific applications in automotive, medical, aerospace, consumer products, plumbing, and construction. CO2 is the preferred coolant for spot cooling because it is cheap to capture and compress. It is also ideal for large scale applications due to lower volume cost and longer storage times. The cooling requirements should be above -50 C. For repeated cooling, CO2 must be supplied at the right pressure and at the right temperature without gas bubbles. It stores longer than liquid nitrogen gas, which is stored at -190 C.
Liquid Nitrogen cryogenics is colder and has greater heat removing capabilities below -60˚C. Proper supply and control system design is crucial because if too much coolant sublimates to a solid state at once, blockages in the cooling system can occur.
It is highly recommended that oxygen monitoring equipment is used to test for oxygen deficient atmospheres during cryogenic spot cooling. The system must be properly maintained to prevent blockages.
Applications:
Applications of cryogenic spot cooling include:
Cooling of construction mold
Preserve experimental samples
Coolant for computers
Medicine to removed unwanted skin, warts, and pre-cancerous cells
Instantly freeze food and cocktails – creating an impressive cloud of vapor or fog when exposed to air.
Internet searches will find recipes for nitro-caramel popcorn and pumpkin-pie ice-cream
Plastic and rubber deflashing and grinding
Metal treating
Biological sample preservation
Pulverization
Summary
Vortex Tube cooling system is a low-cost choice for industrial applications. Simply adjust the hot end hot air valve to determine the temperature at the cold end. The more air escaping from the hot end reduces the temperature of the cold air flowing from the other end of the Vortex Tube.
It produces cold air instantly for enclosed environments. Since there are no moving parts, there is no spark or explosion hazard. Vortex Tube cooling system have two types of generators that are easily interchangeable. One generator has a cooling effect while the other one restricts the flow of the cold air, which creates extreme cold temperatures such as -40 or -50 F. Apart from special designs, the technology is available in the following configurations:
Packaged Frigid-X® Panel Cooler for cooling control panels
When you need require extreme cold temperatures, Nex Flow recommends using the Frigid-X® 50000C series. Nex flow vortex tub cooling system consists of a stainless-steel body with all metal parts. The cooling system is quiet and instantly creates sub-zero cold air temperatures from an ordinary compressed air supply for spot air cooling applications where precise adjustability of temperatures is important.
Like the Vortex Tube cooling system, Thermoelectric spot cooling is an ideal choice for intermittent cooling/heating applications. The disadvantage is that TEC requires a DC voltage because multiple thermoelectric coolers are connected side by side and then placed between two metal plates. Although equally effective for cooling to extreme temperatures as Vortex Tube or thermoelectric cooling systems for many industrial applications, cryogenic cooling appears to have the highest risks and the greatest need for monitoring equipment for health and safety concerns. Nex Flow specializes in research and development of cooling technology required for industrial fic applications, such as spot cooling. Nex Flow® stays ahead of the competition by finding new applications for this unique technology, and to improve the efficiency of the products which depends on many proprietary factors. Corrosion-resistant, food-grade stainless steel means that all Nex Flow equipment is dependable, and long lasting. All spot cooling equipment is precision machined, assembled, and tested. Manufactured to withstand extreme temperatures and environmental conditions, the Vortex Tube cooling system is produced under strict quality control, which ensures years of reliable maintenance free operation.
Vortex tubes are devices that take compressed air and spins it inside the unit creating a spinning air flow in one direction and spins the air flow back in the opposite direction within the first spinning air flow. Part of the air flow is out one end and gets hot, and the internal spinning flow that is let out the opposite end gets cold. It basically acts like tube in tube heat exchanger.
Air input the vortex tube is normally 80 to 100 PSIG (5.5 to 6.2 bar). The air exiting at each end of the vortex tube goes back to atmospheric or at least to a much lower pressure. In considering what you can or cannot attach to vortex tube, you must first consider these realities:
You need a pressure difference between the inlet air to the unit, and the exit points. If there is no significant difference then the system will not work.
The percentage of the air out the cold end is called the cold fraction. For example, if 80% of the inlet air exits the cold side the cold fraction is 80% and the hot fraction (air out the hot side) is 100-80 = 20%. If you add anything to the cold end, there will be a back pressure. This will affect the cold fraction by pushing more air out the hot side thereby reducing the cold fraction. So there is a practical limit of how much back pressure can be tolerated by attaching anything to the cold end. The ultimate limit is a back pressure that pushes all, or almost all the air out the hot end negating any effectiveness for cooling.
Similarly if you attach something to the hot end there will be back pressure pushing more air out the cold end. The limit would be if all the air is pushed out the cold end – it negates most or all of the cooling effect.
Because compressed air exit at both ends, and at a pressure close to atmospheric pressure, a vortex tube is intrinsically safe from over pressurizing, the ultimate supply pressure limited to material integrity (in the case of Nex FlowTM made products, to 250 PSIG).
So when attaching any other accessory to the vortex tube the concepts above need to be considered. Rarely is any attachment made to the hot air exhaust end except for muffling accessories with minimal back pressure. Even in pre-packaged vortex tubes such as Tool Coolers or Panel Coolers, back pressure is very minimal and typically balanced at the cold end with other attachments such as hose hits or air distribution hose with similar back pressure effects, essentially balancing the system. However, if you examine more closely the cold end attachments, which tend to vary the most, there is a limit there as well. When attaching a hose kit such as locline or similar type of hose, the longer the length the more the back pressure. Locline hose is used extensively with Tool Coolers. The general rule is to limit the locline to 12” and under and to make sure the opening nozzle has at least a 1/8” opening. This keeps the back pressure low. Also, the longer you make this attachment, the air will tend to warm up more because of the conduction of atmospheric temperature through the plastic hose to the inside. So practically, the longer the hose, the higher the temperature (less cold air) exiting. In the case of a control Panel Cooler, there is a hose distribution kit supplied which is basically a long PVC hose with a muffler to attach to the end. Instructions stipulate to create inside this long hose to have at minimum of four (4) holes of 1/8” diameter drilled into the hose to let the air out and blow the cold air from the vortex tube onto the hot parts inside the cabinet. This accelerates the cooling of the inside of a control panel. Again, the minimum number of holes is required to minimize the back pressure (and also to help iso-thermalize the control panel faster). If the holes are not drilled, the cold air will exit only at the exit of hose end and with the added back pressure will restrict the flow, hence negatively affect the overall cooling rate (slows the process of equalizing the cabinet temperature). The hose addition onto a Panel Cooler also acts as a backup in case of a very remote possibility of any moisture getting into the panel in the very rare case that the filter on the inlet air fails. There are instances where a vortex tube has a hose attached to the cold end to deliver cold air at a long distance for other applications. It is important to simply use a larger inside diameter hose, the longer the length to minimize back pressure and if possible insulate the hose from conducting heat into the hose, warming up the cold air travelling inside. Care should be taken that the cold end hose is not fully plugged because while the back pressure will force air back out the hot side, any weakness in the hose may also cause it to split and may be dangerous as a result.
The question frequently arise is if it is possible to attach a vortex tube cold air output to the inlet to a blow-off accessory like air knife or an air amplifier (or any other air amplifying or conveying device). The answer is – it cannot be done simply because of the back pressure requirement of the vortex tube (#3 above). Any air amplifying device requires the air inlet to have high pressure. For a vortex tube to work, the air exit pressure from the vortex tube must be low. So attaching a vortex tube to the air amplifying product will just not work.
But…. the possibility of an alternative approach does come up. There have been a few attempted applications, where the air exiting the cold end of a vortex tube is placed near the air entraining end of an air amplifier such as an air jet or small air amplifier like an FX10, or FX20 or even an FX40. Successful results are rare however, and not confirmed, due to how air amplification technology works. The air drawn in by an air amplifier is depends on the amplifier size. For example, an FX10 will amplify air flow about 6.5 times and consumes 4.9 SCFM at 80 PSG. That means it will draw in a volume of 27 SCFM. (6.5-1 = 5.5 multiplied by 4.9). So if you place a vortex tube cold end “close” to the air entraining end the amplified air can be cooled. Even then, much of that cold air will already be mixed with warmer atmospheric air reducing the cold temperature. And, at the outlet of the amplifier about another 3 times the air is entrained from the warmer atmosphere. Assuming basic adiabatic mixing the cooling effect of the vortex tube supplied air will be greatly reduced. With a larger amplifier, the overwhelming effect of the high volume of entraining atmospheric air overwhelms cooling effect of the small volume of cold air from the vortex tube. This is why mixing the two technologies rarely works.
Air amplifiers and even air knives themselves do cool however, and are used extensively (especially air amplifiers) to cool very hot materials such as castings using the wind chill effect. It’s like driving with the window down in your car while driving on a hot day. The high velocity of the amplified air will accelerate the cooling of the hot surface because the high flow and high velocity of the amplified air cuts through the heat boundary layer on the part to remove the heat fast. One example was from an application in Mexico where small, hot aluminum parts which normally cooled in 30 minutes from sitting on a table were cooled in under a minute using a flow amplifier alone.
Vortex tubes are designed to cool enclosures or for spot cooling and not for cooling large areas. In those applications you are best off using air amplifiers. Therefore, combining vortex tubes with air amplifiers however is not a proven method. When using vortex tubes – it is important to understand the above 4 facts governing the operation of the technology.
The Vortex tube is a mechanical device that separates compressed gas into two extreme temperature air currents. It was initially named the Ranque-Hilsch Vortex tube, after the names of the two initial inventors. It is also known by other names including: Ranque tube, Hilsch tube, or Ranque-Hilsch tube. The description of this device was originally described in the US. Patent No. 1952281 by Ranque Georges Joseph. A second US. Patent No. 3173273A was filed by Charles D. Fulton.
According to Charles Fulton US patent – it is defined as an “apparatus for cooling a fluid flowing continuously therethrough comprising a housing body having an opening for admitting a gas, a vortex generator supported in said body and receiving said gas, said generator having a plurality of nozzles and a circular vortex cavity into which said nozzles discharge said gas tangentially, a seal at one end of said vortex cavity, a discharge line communicating with the other end of said vortex cavity, and a smaller line for receiving said fluid to be cooled passing coaxially through said discharge line, vortex cavity and seal.”
Using fluid dynamic principles and compressed air, the Vortex tube generates gas at very cold and very hot temperatures simultaneously. Compressed air is fed into a compact T-shaped tube with pipes attached to each side. With a simple internal generator, the gas emerging from the “hot” end can reach temperatures of 200 °C (392 °F), and the gas emerging from the “cold end” can reach −50 °C (−58 °F). The owners of this device enjoy an extremely long life with very few issues since the compact device has no moving parts. With the simplistic design and parts, the cost to manufacture and maintain the unit is low. There is also no danger of electrocution or fire. The volume of desired gas flow determines the size of the pipe manufactured. It can be used on any type of gas with consistent results. It is the best, simplest, and most direct method to produce hot and cold air.
The exceptional benefit of the Vortex tube is how little gas pressure is required to produce a large temperature difference in the gas streams.
The requirements for the Vortex tube are:
Compressed Dry gas (otherwise condensation and freezing of moisture needs to be considered)
Insulated tube
How Does it Work?
Pressurized gas is injected loosely into a swirl chamber andaccelerated to a high rate of rotation. With the tapered shaped nozzle, only the outer shell of the compressed gas can escape at that end. The remainder of the gas is forced to return in an inner vortex of reduced diameter within the outer vortex.
The Vortex tube was first explained by observing the geometrical shape and design of the tube and air flow (turbulence, acoustic phenomena, pressure fields). The Vortex tube effect of the compressed gas motion results from the law of energy conservation. The main physical phenomenon of the Vortex tube is the temperature separation between the cold vortex core and the warm vortex margin. It is best described in several steps:
The incoming gas is cooled with adiabatic expansion turning any heat into rotational kinetic energy. The total enthalpy is conserved.
Example of adiabatic expansion is when air rises to the atmosphere and expand due to decreased atmospheric pressure allowing the parcel of air to cool.
The peripheral rotating gas moves toward the hot end. Here the heat recuperation effect transfers the heat from the cold slower moving axial flow to the fast moving hot peripheral flow.
The kinetic energy from the rotating air turns into heat by means of viscous dissipation. As total enthalpy increases from the heat recuperation process – the temperature is raised compared to the inlet gas.
ome hot gas is exhausted carrying with it excess heat.
The rest of the gas is funneled toward the cold outlet where more heat is transferred to the peripheric flow. Although the temperature at the axis and at the periphery is about the same everywhere, the rotation is slower at the axis, so the total enthalpy is lower as well.
This lower total enthalpy gas is “cold” and leaves the cold outlet.
The vortex cooling is due to angular propulsion. As the gas moving towards the center gets colder, the marginal gas in the passage is “getting faster”. The more the gas cools by reaching the center, the more rotational energy it delivered to the vortex and thus the vortex rotates even faster.
Compressed gas at room temperature expands to gain speed through a nozzle. It climbs the centrifugal barrier of rotation during which energy is also lost. That energy is delivered to the vortex, which speeds up the rotating air even more. In a Vortex tube, the cylindrical surrounding wall confines the flow at margins and thus forces conversion of kinetic into internal energy, which produces hot air at the hot exit.
The limiting factor for producing the extreme temperatures is high gas pressure to create the extreme temperature changes in the tube.
Who Invented and Improved the Vortex tube?
Georges-Joseph Ranque (7 February 1898 – 15 January 1973) was the inventor of the Ranque-Hilsch Vortex tube. He was born in France in 1898. At a young age, Georges became interested in physics. In Paris, he studied physics at the Ecole Polytechnique. Afterwards, he pursued a postgraduate degree at the Conservatoire des arts-et-métiers. His initial interest in the operation of the Pantone carburetor led him to study vortices. One of the applications he used the vortex effect was a vacuum pump. His intention was to use his invention to remove dust from a steel plant. While studying the flow of air through a pump, he inserted a cone at one end of the tube, where air was flowing in a vortex and discovered that the stream of air could be split: one hot and the other cold. In 1931, he filed the US. Patent No. 1952281.
Ranque described his tube as having a counter flow and a uniflow type. Through his research he determined that the counter flow tube was more efficient. The counter flow Vortex tube consisted of:
A long slender tube with a diaphragm closing at one end of the tube and a small hole in the center of the diaphragm.
One or more tangential nozzles piercing the tube inside the diaphragm
A throttle valve at the far end of the slender tube.
On the other hand, the uni-flow Vortex tube is similar in structure to the counter-flow Vortex tube, the significant difference is that the uni-flow tube has two exit holes in the same end. This tube appears to have lower efficiency than the counter-flow tube because of the mix of cold and hot temperature flows at the same exit. Since Ranque’s discovery, the Vortex tube has been the subject of much research and study by the scientific community. The primary focus of research was to determine the factors that caused the thermal separation and to improve the performance of the tube.
Ranque saw the commercial potential of the tube he called “Vortex tube“, which means “tube tourbillion” in French. Unfortunately, compressed air systems were not reliable at the time of this invention. The initial Vortex tube was a commercial failure and Ranque’s firm closed a few years afterwards. He continued to work on other fields of research and the initial discovery of the Vortex tube slowly faded.
The Vortex tube would have remained forgotten if it was not for Rudolf Hilsch, a German physicist, professor, and manager of the Physics Institute of George August University of Göttingen, who is credited with improving the understanding and performance capabilities of the Vortex tube. The important research reported in his 1947 paper, Die Expansion von Gasen im Zentrifugalfeld als Kälteprozeß, emphasized that considerable cooling can be achieved by using the Vortex tube in various applications including refrigeration and cryogenics. He cited Ranque’s work in the paper but because of a printing error in the footnote, it was difficult for other scientific researchers to locate the previous research. Therefore, the Vortex tube was briefly known as the Hilsch tube. Now, the importance of this paper allowed Hilsch’s name to be included in the name of the tube so that it is now known as the Ranque-Hilsch tube.
In May, 1947 William Taylor of the National Bureau of Standards published Vortex tube experimental results that described another hypothesis of how the tube works. When compressed air passes through the entry nozzle, it speeds up and loses heat. The velocity gained results in a loss of heat energy. This fast, cold air is then slowed as it spirals in the tube. The molecules of gas drop to the center of the tube. Surprisingly, instead of heating up as they lose speed, they pass their energy to the next outer layer and remain cool. The additional cooling effect is caused by the centrifugal force of the whirlpool. The centrifugal force “throws air molecules” out from the center so that there are fewer molecules and lower pressure. When the air molecules move from the high-pressure region of the tube to the lower pressure region in the center of the tube, the gas expands and cools.
In 1961, a General Electric engineer, named Charles Darby Fulton studied the Vortex tube carefully and developed it for commercial applications. Between 1952 and 1962 he obtained the following U.S. Patents related to the development of the Vortex tube:
US2603535A: Liquid spray nozzle Filed July 15, 1952 INVENTER David C. Ipsen, Charles D. Fulton.
US3208229A: VORTEX TUBE Filed Jan. 28, 1965 2 Sheets-Sheet 2 INVENTOR. CHARLES DA FULTON
provide improvements in the Vortex tube so that they emit colder gas and a larger fraction of cold gas with increased efficiency for a greater range of applications
Reduce leaks
Increased ability to utilize high gas pressures efficiently
Reduce the cost of manufacturing
His company, Fulton Cryogenics, manufactured Vortex tubes and became the Vortec Corporation in 1968 to expand and improve the Vortex product line for industrial and commercial applications. The Vortex tube was used to separate gas mixtures, oxygen and nitrogen, carbon dioxide and helium. In 1991, the Illinois Tool Works acquired Vortec Corporation to further study the Vortex tube for technological applications.
Research for nozzles lead to improvements in the Vortex tube design. Merkulov recommended the tip area being 9% of the cross-section of the tube “with the axial width to be twice the radial depth.” He also inserted a cross in the tube and ultimately shortened the length of the Vortex tube and he received a US patent in 1968 (patent number US3522710A – F25B9/04).
The optimum length of the hot end suggested by Merkulov was 8 to 10 Dc (tube diameter). In 1961, Dr. Parulekar published a paper based on a short Vortex tube:
A cylindrical or convergent piece of axial length equal to 6 mm.
A divergent truncated cone with axial length equal to 18mm.
Cover, which also forms the third part of the hot side is cylindrical and of axial Length equal to 20mm.
In 2001, Guillaume and Jolly performed a study on a two stage Vortex tube where the cold air from the first tube was injected into a second Vortex tube. They reported that the temperature difference at each stage was greater than would be generated from a single stage Vortex tube.
To optimize the performance of the Vortex tube, multi-stage Vortex tubes have been studied. Dincer in 2011 tried a “three-fold type and six cascade type Vortex tube systems” consisting of three and six Vortex tubes connected in a series. Through this research, the greatest temperature drop occurred when six-cascade Vortex tubes were connected.
The curved Vortex tube, studied by Valipour and Niazi in 2011, proved that an increased in temperature difference was influenced by the curvature of the tube. The maximum refrigeration capacity occurred at 110-degree curvature. The maximum temperature difference was generated by a straight Vortex tube.
Other types of Vortex tubes that have been studied include Vortex tubes in various surroundings, insulated, non-insulted and the types of fluids used – such as water instead of compressed air, oxygen, methane and other gas mixture.
Experimentation Discoveries
Ranque discovered through extensive experiments that when the compressed air enters through the tangential nozzle and expanded cold air discharges through a small hole in the diaphragm. Simultaneously, hot expanded gas is discharged through the valve. The coldest gas is produced only when a small fraction of the gas is released through the small hole. It is recommended that the valve is opened widely for this to occur. The result is the hot gas cools to become warm gas. The hottest gas is achieved by closing the valve. Then, nearly all the gas is released through the small hole and is cool.
The two major inefficiencies of this design are:
Only a small fraction of the gas can be extracted at the lowest temperature
The amount of temperature depression obtained never approaches that of an ideal expansion engine.
Continued research is required to determine the optimum configuration is complicated and challenging. There could be up to fifteen factors that need to be considered when optimizing the design. Here are a few:
kind of gas
gas pressure
temperature
rate of flow
cold fraction to be delivered at a certain lower pressure
The research on Vortex tube also involves the compressible fluid dynamics of turbulent and unsteady flow, thermodynamics, and heat transfer. Westley stated, “Besides its possible importance as a practical device, the Vortex tube presented a new and intriguing phenomenon in fluid dynamics”.
Each of the above factors results in a change in condition for the remaining factors. Research to determine the optimized factors of using a Vortex tube continues because of the fluid and dependent nature of research results.
Applications of the Vortex tube
The Vortex tube invention impacted refrigeration, air conditioning, cryogenics, instrumentation, and controls. The Vortex tube excels in situations such as cooling a worker wearing a protective suite or electronic equipment in extraordinary hot environment. Research is often placed on cold gas because of its greatest importance and number of uses. Vortex tubes are useful where sometime heat and sometimes cooling of persons or work environments are required. When using a Vortex tube, it is understood that when cold gas is generated, hot gas is also a bi-product.
Nex Flow strives for excellence and improvements in the Vortex tube technology and original design to best suite an application. Nex Flow provides three standard sizes of the Frigid-X® Vortex tubes:
Mini size – uses 2, 4 or 8 SCFM
Medium size — uses 10, 15, 25, 30 and 40 SCFM
Large sizes — uses 50, 75, 100 and 150 SCFM.
Depending on the temperature and pressure the compressed air used, it is possible to achieve cold end temperatures as low as – 40 (-40 C) and even – 50 degrees F (-45.56 C). Vortex tubes are used to cool electronics, machine operations, tools, CCTV cameras, soldered parts, gas samples, and heat seals. Contact Nex Flow expert technicians to help you decide the best Frigid-X® Vortex tubes for your application.
Nex Flow compressed air accessories can complement and enhance your compressed air systems. Awareness of the best accessories (based on application) can save energy, extend the lifespan of equipment, and provide a safe environment for workers when using compressed air. This article describes tips that enhance the performance and prolongs the life of compress air accessories.
What are Examples of Compressed Air Accessories?
Compressed air accessories include filters (oil and water), separators (shims), valves, nozzles, tubing, hoses, etc. Nex Flow engineering experts are happy to provide advice when choosing the best compressed air accessories for your application. We are dedicated to reducing the cost of compressed air system operation and extending the life of your products. All products come with a 5-year manufacturing warranty.
Prevent Leaks
Benjamin Franklin once said, “An ounce of prevention is worth a pound of cure.” Be proactive by regularly checking for leaks in filters, fittings, valves, and connectors. Leaks occur especially when your compressed air system is aging. Inspecting your entire system regularly prevents leaking air. Leaks can originate from lines, gaskets, fittings, valves, clamps and connections. They can divert an estimated 25 percent of your compressed air. Leak detectors can be helpful in identifying the issues before they become costly to repair. In addition, solenoid valves can be used to control the flow of liquid and gases.
Check the quality of pipes in your compressed air system. Simply using quality and replacing worn out pipes can save energy and maintenance costs. Pipes that are free of corrosion, clean, and dry are a good indication of quality piping. If the air is not properly filtered, dust appears in the pipes which could lead to inlet filters becoming clogged, causing a decrease in pressure, and the chance of product contamination. If left unattended, wastes will accumulate, and these dust and sludge will corrode piping very quickly and exacerbate leakage. Properly dried and filtered air keeps your pipe system clean and reduces maintenance.
Inspect Equipment Regularly
Strange noises and excessive vibration are indications of problems. Learn to recognize issues as soon as problems occur. Inspect the entire compressed air system regularly including accessories. Keep everything tight because otherwise screws, nuts, and bolts can all loosen. Tighten accessory that has become loose. It is highly recommended to regularly inspect your system, understand and know the acceptable range of the gauges so you can flag if the system is abnormal. This knowledge can prevent major damage to equipment and prevent costly repair. Check the coolant and refill it regularly since the coolant prevents your system from overheating and prolongs the life of your compressed air system.
Cleaning
With the help of expert technicians with years of experience, develop a daily cleaning routine of your system and accessories. Remove filters and blow them clear of dust to extend the life of the pipes, filters, and nozzles. Dust and debris can collect in filters and if they clog, it will impact the effectiveness of your system. Other than dusts, filters should also be drained of any liquid they collect. Remember that any residue may dry and leave a film – this is especially hard to remove if it is an oil residue. So before putting the filters back in use – it is important the filters are properly drained and cleaned to prolong the lifespan of the product.
Seek out moisture in your entire system. Moisture can cause wear and tear on your accessories. Condensation can deteriorate the health of your system and shortens the lifespan of equipment. Ensure that the air compressor is eliminating moisture as expected on a daily basis. Furthermore, check drains and separators to ensure that no moisture is pooling.
Maintenance
It is highly recommended to follow the compressor maintenance schedule. Ignoring maintenance costs more because it leads to costly repair and replacement expenses. It is critically important that the correct lubricant is used on tools and compressed air accessories to promote long life. Incorrect lubricant can damage internal parts. For blow-off or air conditioning systems, it is equally important not to use a lubricant since it could block the nozzle. In situations where the entire air system is lubricated, it is recommended that an oil removal filter is installed upstream.
A compressor runs more efficiently when properly maintained. Proper compressor maintenance cuts energy costs and prevents breakdowns. Maintain oil change schedules and other timely scheduled maintenance on your compressors. Consult your air compressor supplier for advice regarding the most efficient method to run based on the application of use, especially if you own several compressor units.
Vortex tube cooling for cabinet enclosures is essential in very dirty or humid environments. The use of cabinets coolers not only keep the control panel clean but also keep maintenance costs to a minimum. If the equipment become clogged and stops working, the cost of an enclosure is easily recovered compared to stopping work to repair sensitive parts on the control panel.
Pre-packaged Electronic Thermostat
Setting the temperature of when compressed air will be used, will extend the lifespan of your equipment. Thermostats control the temperature setting inside your control panel. The compressed air equipment will only be used when necessary. Also, Nex Flow®Panel Coolers ensures a positive pressure to keep out atmospheric air in control panels. A small amount of air flowing into the control panel is important to maintain a slightly positive pressure. Nex Flow also offers a special temperature-sensitive sticker that is put on the outside of a control panel as a qualitative indicator to show when a panel is overheating.
Proper Filtration Use
Using proper filters based on the application and changing filters regularly will prolong the life of your blow off products. Instead of using cartridge filters, where water and oil removal pose a high maintenance cost, it would be wise to use the following compressed air accessories for longer life:
Oil Removal Filters – an excellent choice for oil removal because it filters up to 0.3 microns.
Liquid Super Separator – removes 99.99% oil and water from a compressed air system. This filter addresses access water problems and extends the life of existing filters.
Use Stainless Steel Shims for longer life
Unlike other manufacturers – Nex Flow® only sells stainless steel shims because we understand that plastic shims will wear out quickly. When required, shim kits and individual sizes are available for spare parts, enlarge the gaps in existing products to increase flow/force, or to replace old shims if necessary.
Conclusion
Having keen knowledge of how your compressed air system works optimally only occurs when a regular maintenance and inspecting schedule is kept. Once you are aware of your compressed air system, issues. Loose or loud components, can be quickly replaced and maintained before expensive repairs are necessary. Knowing the correct compressed air accessory for the application will save operation costs and extend the life of the equipment you have installed. Nex Flow is the company that is most qualified to help you select the most effective compressed air accessories for your application.
The Nex Flow Panel Cooler is a vortex tube operated air conditioning system used to cool electrical and electronic control cabinets. They have many advantages such as simplicity in installation, near zero maintenance, no condensate and more. But one major advantage for control cabinets in harsh environments is that when operating they keep control cabinets at a slightly positive pressure, therefore keeping out the factory atmosphere. Panel Coolers are utilized especially in environments that are very dirty, dusty, hot and moist, or corrosive. This ability to keep the control panels at a slightly positive pressure becomes very important. However, this is only the case while the Panel Cooler is actually operating.
On-off control
One of the ways to minimize compressed air use with a Panel Cooler or any vortex cooling system is to have some sort of an on-off control system. One method is to use a thermostat coupled with a solenoid valve to turn the compressed air on when the cooling is needed, or turn the air off when it is not required. However, when the Panel Cooler is off, it no longer keeps the control panel at that slight positive pressure. It is at this point where the factory environment can encroach into the control cabinet and possible to have a negative impact on the internal components.
Single VS Multiple Panel Coolers
If there are two or more Panel Coolers on a control cabinet, normally one runs continually and the other one (or ones(s)) cycle on and off as required for cooling. That is enough to keep the control panel, even if very large, at the slightly positive pressure enough to keep out an unfriendly environment. But when only one Panel Cooler is used then some creativity is needed.
One of the tricks of the trade in factories such as highly humid bottling facilities, even with standard air conditioners, is to take a small compressed air line and pipe a very small amount of compressed air constantly into the cabinet to keep out the humidity that could harm the controls. A typical Standard air conditioners go on and off, so the humidity needs to be addressed. Similarly in very corrosive and dirty environments, a tiny amount of compressed air piped into the panel solves the potential expensive repair of the internal parts of an electrical or electronic enclosure.
So what are the options when using a single Panel Cooler? One vortex cooler supplier uses a thermostat and solenoid package for on-off control but they drill a small hole into the solenoid valve so that in the “off” position, a small amount of compressed air continues to flow through the cooling unit. There is not enough flow to effectively cool in the off position but enough flow to keep the cabinet at a higher pressure than the environment.
There are two disadvantages with this method.
First, it may not be legal in some jurisdictions because drilling a hole in the solenoid valve may take away its electrical approval rating. This may result in all sorts of problems from insurance coverage to legal should something go wrong.
Second, there is no control over how much of this air can go into the cabinet. For very large cabinets, it may not be enough air to make any difference in pressure, and for small cabinets there may be too much air flow that it wastes energy.
Overcoming the disadvantages
To overcome the above disadvantages – Nex Flow has designed a special by-pass system.
The by-pass system works with all panel coolers both Nex Flow and non-Nex Flow units. It consists of a control valve that is connected between the compressed air supply (after filtration) at the inlet to the solenoid valve that controls the on-off operation of the vortex cooling system. There is a small tube emanating from the control valve that is connected to a three-way fitting that connects to the outlet of the solenoid valve. One inlet is for the tube, a second inlet connects to the outlet of the solenoid, and the other connection goes to the line that takes the compressed air to the cooling unit.
This overcomes both the previous disadvantages mentioned. The solenoid valve is not tampered with so no electrical approvals are jeopardized and eliminating any potential insurance or legal issues.
The control valve on the inlet side of the solenoid valve has a small knob to set the amount of by-pass compressed air used. It can be set to a very small flow rate for small control panels to save energy and a higher flow rate for larger control panels to insure there is enough air flow to maintain a higher pressure than the environment. Control remains completely in the hands of factory personnel and not with a tampered solenoid valve.
The Panel Cooler by-pass system is also made of all 316 stainless steel so it can be used in all types of environments and with all ranges of Panel Coolers offered by Nex Flow (and their competitors) including NEMA 4X (IP 66) environments. The system is simple to install, easy to use and versatile. In relatively benign factory environments, a by-pass system may not be necessary. Furthermore, if the Panel Coolers operate continuously they are obviously not required. To determine if having a by-pass system would be beneficial, you simply have to access the plant environment. In corrosive atmospheres or highly humid atmospheres the benefit is quite clear cut. However, regardless of the environment, when used, they have been proven as an effective way to keep the internals of a control clean and dry.
If there is more than one Panel Cooler, as mentioned earlier, normally one is always operating. However, if the plant atmosphere is really harsh, it might still be useful to have a By-Pass System on at least one cooling unit assuming the control panel is completely shut down during a plant shutdown.
As with all Panel Cooler installations, it is important to have proper filtration to remove any loose water or oil to keep the system clean and dry.
The biggest criticism against vortex tube-operated air conditioners for control panels is their use of compressed air. Still, in certain situations, it just makes sense to use them depending on the importance of reliability and the nature of the factory environment.
Nex Flow Air Products Corp. manufactures compressed air-operated products for blow-off, moving, and cooling applications to optimize the use of energy with safety and the environment in mind.
Vortex Tube operated cabinet enclosure coolers such as the Nex Flow Frigix-X Panel Coolers operate utilizing compressed air wherein one end gets hot, and the other end gets cold. They find applications in particularly dirty environments and hot and wet factory climates.
Because of the rough environments they are subjected to, construction materials are pretty necessary. Some manufacturers utilize stainless steel with the vortex tube (cold temperature generating portion) and then packaged it in an aluminum housing and assembly, usually not anodized. So after a short time, the appearance of the aluminum, especially if not anodized in such environments, look pretty deteriorated.
But it is mainly in hot and humid environments where the combination of stainless steel with aluminum can be a problem due to the possible effect of galvanic corrosion between these two very dissimilar metals. Due to this corrosion effect, I have personally seen a vortex-style cabinet enclosure cooler with a big gaping hole in its aluminum housing.
So if choosing vortex tube operated cabinet enclosure coolers, it is a good idea to check what they are made off. Nex Flow makes them from stainless steel. The vortex tube, housing, and attachments are stainless to avoid this corrosion issue. Stainless steel will obviously hold up much better than aluminum in a nasty factory environment.
Nex Flow manufacturers specialized compressed air products for blowoff, cooling, and moving c/w quality accessories for controlling, monitoring, and filtering compressed air.
When choosing the means to cool control panels or any electrical and electronic enclosure, you need to consider the control panel rating and factory environment before selecting the best method.
Nex Flow Air Products Corp. manufacturers and markets specialized compressed air technology for cleaning, drying, blow off, moving and cooling including vortex tubes and products that incorporate vortex tube technology.
l and electronic enclosures while Europe and many other countries utilize IP classifications. This often causes some confusion. We found a great chart from Siemon that do IT infrastructure solutions what has a very concise equivalency chart.
for air conditioning control panels anywhere in the world.
Nex Flow Air Products Corp. manufacturers specialized compressed air products for cleaning, drying, blow off, moving and cooling applications. They lead in vortex cooling technology development. A major application for vortex cooing is for electrical and electronic enclosures, especially is very humid, hot and dirty environments where regular air conditioners would entail much higher maintenance costs and shorter life.
Galvanic corrosion occurs when two dissimilar metals come into contact. It is also necessary for there to be moisture, but it is rare to find an environment without moisture. I still remember visiting a factory and seeing a competitor’s Cabinet Enclosure Cooler (using vortex tube technology) with a big hole on the aluminum cover, obviously caused by some form of corrosion. While the unit was still functioning, this gaping hole made dirt buildup inside the system a definite probability of shortening the life of the unit which, if it used proper materials, or at least anodized the aluminum could last 20 years.
Air blow off products such as air knives, and amplifiers use (usually) aluminum or zinc. Air knives in particular are normally made of aluminum with steel, or stainless steel screws. The further apart the different metals that are matched together are, in terms of relative potentials, the greater the possibility of galvanic corrosion in a wet or humid environment. For example, stainless steel in contact with copper is less likely to be a risk than when it is in contact with aluminum or galvanized (zinc coated) steel. Seawater or salt laden moist air is more of a risk than contact with rain water or say water used for wash down in a factory. Vortex tube operated cabinet enclosure coolers are typically assembled using stainless steel vortex tubes since stainless is the most common material used for vortex tubes due to long life and durability. The surprise is that some manufacturers still, after many years, use aluminum for mufflers, sleeves and casings exposed to a potentially wet factory environment with a stainless steel vortex tube. As long as the environment stays dry, it is not a problem but if the environment is wet, or the enclosure cooler is used in a wash down environment such as in a NEMA 4 (IP56) area, then the risk of galvanic corrosion is much higher.
Anodizing the aluminum is one way to help prevent that from happening as it provides insulation to the galvanic action. But some manufactures of these units have not even done that.
Nex Flow Air Products Corp. uses stainless steel vortex tubes and stainless steel muffling, sleeves, etc. – no aluminum in their cabinet enclosure coolers (Panel Coolers) to avoid galvanic corrosion which can occur if the units are subjected to a humid environment or wash down procedures. Their NEMA 4 (IP 56) units are stainless steel for NEMA 4-4X environments.
What also comes into play is the surface area of each material used. For example, if there is a large area of aluminum and a little stainless steel screw, there will not be much of a problem. Aluminum air knives for example can have stainless steel screws and the galvanic action remains minimal. Nex Flow anodizes their aluminum material to be extra cautious. Most compressed air operated air knife producers however do not anodize. (The near term negative effect of a factory environment on non-anodized aluminum is another topic.)
To keep the aluminum/stainless mix acceptable, the stainless part should be small and the aluminum part large, and of course, keep them dry and away from a humid area. Better still, either anodize the aluminum or just do not mix the materials.
Nex Flow Air Products Corp. manufactures compressed air operated products for blow off, drying, cleaning, cooling and moving along with specialized pneumatic technology to reduce noise, energy use, and to improve the compressed air productivity in a factory environment.
