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.
Industrial Panel Air Conditioning Options and Trends
The various options for cooling electrical cabinet coolers include, traditional compressor-based air conditioners, air-to-air heat exchangers (with heat pipes), thermoelectric air conditioners, and finally vortex coolers. Each cooling method has its plus’s and minus’s.
Sensitive electronic devices are used increasingly in hostile environments. High temperatures, contaminant-laden air, high humidity and corrosive atmospheres are bound to negatively affect sensitive electrical and electronic equipment. Damage to the controls can result in costly repairs, downtime, and even lost data. Inadequate protection of the controls can cause unwanted heat buildup, which can increase an enclosure’s internal temperature above the manufacturer’s recommended ratings for electronics/electrical equipment installed inside. This heat can come from both internal and external sources.
Internal heat sources come from the very components that needs cooling. These include:
Variable Frequency Drives (VFD’s)/inverters
Battery Pack back-up systems
Communication equipment
PLC systems
Power supplies
Routers & switches
Servers
Transformers
External heat sources come from the factory environment. Including:
Heat from blast furnaces and foundries in heavy steel and metals production
engine rooms
food processing factories with high humidity and heat
industrial ovens from bakeries and paint facilities
hot climates in general
manufacturing plants, especially producers of materials like insulation, carbon black or where other airborne dust and dirt particles are in the factory atmosphere
outdoor solar heat gain if the control are in direct sunlight
uninsulated and/or non-air conditioned buildings that heat up during the day
Although these heat sources may present a problem and potential damage to the systems – there are various methods in keeping the control panel cool. Here are some ways along with their advantages and drawbacks. Traditional Compressor-Based Air Conditioners Pros: High cooling capacity Cons: Higher maintenance, high capital cost, more sensitive to breakdown the worse the environment
Compressor-Based air conditioners rely on chemical refrigerants to remove heat from electronic/electrical enclosures. In addition to refrigerants, these air conditioners also use compressors, evaporators, condensers, and fans to provide cooling. The refrigerants used in the past are being replaced with more environmentally friendly products but the cost of these new refrigerants are sometimes ten times that of the obsolete refrigerants. In addition, some if not most of these new refrigerants are flammable which means there are design changes to insure safety when connected to a control panel with a potential to produce a “spark”. These units produce condensate which must be removed. Fans need filters which must be cleaned or replaced. If mounted on equipment subject to vibration then the refrigerant can leak out prematurely and need costly replacement. This also means more shutdowns affecting production. Depending on the factory environment lifespan of a traditional air conditioner can be anywhere from five to ten years but in very harsh environments, much much less.
Air-to-Air Heat Exchangers Pros: Low maintenance, relatively inexpensive Cons: Cannot cool below ambient so limited by environment.
Efficient, cost-effective cooling can be realized through heat pipe assembly systems. These air-to-air heat exchangers remove waste heat from sealed electrical panels and enclosures to protect sensitive electronic components without exposing them to harsh, dirty environments outside the cabinet, a nice advantage. Simple design means long life as well, although because they use fans, the fans need to have care and maintenance, especially in harsh factory environments. However, the big problem is that you cannot cool below the environment ambient temperature and in many factory environment that temperature is still too high and therefore limiting the use of this technology.
Thermoelectric Air Conditioners Pros: Reliable, relatively low maintenance Cons: Cooling capacity is limited, and must be careful to size accurately, potentially use much more power to operate, extra care needed in installation. Thermoelectric solid-state air conditioners utilizing the Peltier effect were introduced some years ago but only have limited use for a variety of reasons. This effect is harnessed by using two elements of a semiconductor constructed from doped bismuth telluride. Upon application of a direct current (DC) power source, the device transfers heat from one side to the other. The side that heat is taken from becomes cold. They can dissipate loads up to 2,500 BTU/hr. However, there are some issues to consider. Peltier modules release a large amount of heat in the course of operation. They require in the cooler heatsinks and fans capable of efficiently deflecting surplus heat from the cooling modules. Thermoelectric modules are noted for their relatively low efficiency coefficient; when they act as heat pumps, they are powerful sources of heat. Using these modules in cooling devices however, intended to protect the electronic components of the computer, dramatically increases the temperature within the system unit. This sometimes requires additional cooling devices within the controls. If you don’t use additional cooling, the high temperatures can complicate operating conditions — even for the modules. Also, using Peltier modules creates a relatively heavy extra load for the power supply to handle. At the cooling side, the low temperatures produced by the operation of Peltier coolers can be too low and cause moisture from the air to condense inside the cabinet. This is dangerous for electric components. Therefore extra care needs to be taken in choosing the correct unit. When choosing a Peltier module of appropriate cooling power, it is necessary to ensure that the entire surface of its cold and hot sides are used. Otherwise, the parts of the module that do not have contact with the surface of the protected object (such as a processor chip) will only waste power and emit heat, decreasing overall cooling efficiency, possibly quite dramatically. One comment made by an informed user was that “They only become effective when the temperature differential is large enough. In most cases it will just increase the wattage drawn without doing anything that much better than a plain air conditioner.” The cold side gets cold, but then you’ve got an even larger amount of heat to remove from the hot side. So you need an even larger heatsink or some heat removal system on the other side. Hence the extra care in any installation.
Vortex Coolers Pros: Low maintenance, small footprint, low cost, keeps out moisture and dirt, no condensate, not subject to vibration, easy to install. Cons: Require compressed air
Vortex coolers can be a low cost way to cool and purge electronic/electrical enclosures, especially in situations where conventional cooling by enclosure air conditioners is not possible. Applications may include small to medium size equipment enclosures. Vortex coolers use compressed air to provide a cooling air flow. This means they are limited to applications where there is a ready source of clean, compressed air such as in medium to large industrial plants. The positive aspect is that it is these sizes of factories that usually have the cooling issues with their electrical and electronic control panels – hot and humid environment, and dirt and particulate in the atmosphere, have the compressed air.
The primary component in a vortex cooler is a vortex tube, also known as the Ranque-Hilsch vortex tube that creates a swirling effect from the compressed air input and separates it into hot and cold air streams. A vortex cooler is unique in that it has no moving parts. At the end of the hot tube, a small portion of this air exits through a needle valve as hot air exhaust. The cold is pushed into the enclosure which air conditions the cabinet. A properly designed vortex cooler like the Nex Flow panel Cooler has a built-in exhaust so there is no need to vent the enclosure, and has been tested and NEMA (and/or IP) approved to insure no water can get inside a cabinet from the outside. This vortex provides a positive purge on the cabinet, which also helps to keep dirt, dust and debris out of the enclosure. There is no condensate to deal with. Because the compressed air is filtered to be clean and moisture removed (a necessary requirement with vortex coolers), even if the compressed air supply is saturated with moisture before the filter, there will be no moisture inside the cabinet because the compressed air goes back to near atmospheric pressure keeping the relative humidity of the cooling air low. One nice feature about the cooling effect of a vortex tube cooler that is often not noticed is that its cooling effect depends only on the temperature of the compressed air. So even if very hot environments, for example right next to a hot furnace, as long as the compressed air temperature is reasonable, it will cool very effectively. It is very difficult to install a vortex cooler badly. It is simply a matter of putting in a standard knockout hole on the control panel, installing the unit, adding a hose with punched holes (to distribute the cold air around the panel quickly), and then let it operate. An optional thermostat with solenoid can turn the air on and off as needed to conserve energy. A major application is for variable frequency drives (VFD’s) where the cooling is normally needed only on startup only so energy use is actually quite minimal and very cost effective. The harsher the factory environment, the more vortex coolers become economical as they do not break down in such environments nor do they have the extra maintenance the alternatives require.
COMPRESOR BASED AIR CONDITIONERS
AIR-TO-AIR HEAT EXCHANGERS
THERMOELECTRIC AIR CONDITONERS
VORTEX COOLERS
INITIAL COST:
High and becoming Higher
Low
Moderate
Low
EASE OF INSTALLATION
Complex
Simple
Can be complex
Simple
ENERGY USE
Moderate
Low
Moderate
High
MAINTENANCE TIME & COST
Moderate to high
Moderate due to fans
Moderate
Low (may offset energy cost)
EASILY HELPS KEEP ENCLOSURE CLEAN
No
Yes
Yes
Yes
EASILY HELPS KEEP ENCLOSURE DRY
No
Yes
No
Yes
ABILITY TO COOL BELOW AMBIENT
Yes
No
Yes
Yes
FRIENDLY TO ENVIRONMENT
No (costly chemicals that eventually go Into environment)
Electrical and electronic control panels are the heart of factory production. Any problems that occur with them can cause minor to major production hiccups, slow downs and potential need for a factory shut down. Just as you would take care of your own heart, it only makes sense that you recognize the heart of production and take good care of it.
But often this does not happen. How many times do you see control panel doors left open because they get “hot” inside. This creates a potential safety hazard and if the environment is not clean, it may cause dirt buildup inside the panels, on the controls – eventually leading to potential costly, premature failure.
As often as not, these control panels that are left open due to heat buildup is because of a lack of maintenance on whatever cooling system they may already have. It could be a simple external fans, external blowers, or traditional panel air conditioners. Even with water cooled systems, maintenance is necessary. External fans need filters, especially in dirty environments and these filters get dirty and require regular cleaning and/or replacement. Similarly with blowers, perhaps even more often. Water cooled systems have small water lines and can scale up, preventing adequate cooling. Traditional air conditions are an even more critical machines for regular maintenance. Not only do filters need to be cleaned and/or changed regularly, especially in dirty environments, if air conditioners are on machines that have vibration the refrigerant inside may leak out the unit. It is important to recognize the cost of the smallest downtime due to a control panel “going down”.
So what can be done? If whatever cooling system is working well and you do not have issues with control panels overheating, then of course nothing. Keep doing what you are doing. But if you have even once have to open a cabinet door to vent out some heat – then you have a problem. Would you ignore a sharp pain in your own heart? Well, that overheating is the panel’s pain.
One solution is to overhaul the maintenance program on the control panels as that can certainly be a source of the problem but that in itself may reveal and create other costs. But it is one option. Another option is to use a Nex Flow Panel Cooler.
Despite the use of compressed air for operation the Nex Flow Panel Cooler is essentially maintenance free. Once installed, it can be left to operate under the worst conditions of a dirty factory environment, with high humidity, high ambient temperature and even on equipment that vibrates. How it works is simple – compressed air enters the Nex Flow Panel Cooler and the vortex tube component separates the compressed air into a hot and cold stream. The hot end is exhausted as waste but the cold air goes inside the control panel to cool and keep the cabinet from overheating. The connection to the cabinet has a built in exhaust to vent out the hot air displaced by the cold air. Since there are no moving parts, and no refrigerant chemical inside the unit, the Panel Cooler can handle equipment vibration. The air entering the cabinet keeps the cabinet at a slightly positive pressure keeping out any humidity and any dirt and particulate in the environment. The effectiveness of the air conditioning depends solely on the temperature of the compressed air and not the environment making Panel Coolers ideal to use in hot and humid locations. There is no condensate produced that needs to be disposed of and you do not have to worry about replacing filters. The only basic requirement is to properly filter the supplied compressed air. To conserve energy, a thermostat and solenoid valve control system can turn the air on and off as required. Alternatively an electronic thermostat system can be used. To keep the cabinet constantly at positive pressure to keep out a very nasty environment, a bypass system can be installed around the solenoid to always have a very small amount of compressed air flowing even when the unit is off.
If maintenance is not adequate or perhaps the environment is just so unfriendly it causes serious and costly issues for whatever the reason for problems with traditional air conditioning or other cooling systems, the Nex Flow Panel Cooler can be a viable option and the extra energy costs often offset by the shorter life span, or damage to controls and other problems created using other systems.
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.
