Compressed air is a tricky technology to deal with because it is a compressible fluid and subject to all sort of things. Yet 70% of all compressed air is still sued for blow off and cooling because it is so versatile. But it can be used more efficiently.
One of those applications that can be much more effective is when using engineered compressed air nozzles. Properly designed engineered nozzles work by entraining surrounding atmospheric air along with the compressed air to convet energy normally lost as pressure drop and noise. But not all air nozzles are engineered. And some engineered nozzles are not very well designed. This may not matter is small applications but when you add up the nozles in a large facility it can be a significant amount of money.
The first thing to decide is if you want to cool a part or clean it. In the first case, flow is more important than force. In the second case, force is more important than flow. Then there is comparing air nozzles. Assuming that manufacturers are honest about their specifications (which is not necessarily the case), you need to look at both force and flow.
This is far more critical when force is required. In this case the force/unit air consumption is the best thing to look at. The most efficient (and effective) nozzle will be the one with the highest force/unit air flow (Force/SCFM ratio). It does not matter so much how force can vary among a variety of nozzles becasue in a proper installation you use a regulator to cut back the pressure to set the force you need, Force above what you need only uses more energy. But in real life here is where it gets tricky….
Lets assume you have an installation with a set of nozzles from one supplier. You find a second brand that give the same force at the same pressure. And the cost for the nozzle is a bit less. You have no regulator on your system. So you just replace a few nozzles. But…. then you find that the actual force is less than specified? Yes according to what you read, it should be the same! What went wrong?
Well, if you then check the specifications further yu find that the replacement nozzles uses only 1 SCFM more than the one you are using. It certainly does not seem much but…. that extra flow going though the piping, which is typically the same size as the nozzle, can actually cause enough extra pressure drop that the effective pressure at the nozzle entrance is just a little less, which also makes less force. That is how sensitive the nozzle effectiveness can be. So if you are replacing any nozzles, check not only the force created at a particular pressure, but also the air consumption at that pressure. The odds are that the pressure at the entrance to the nozzle is NOT the same pressure that you think it is due to pressure drop.
When considering the use of compressed air nozzles consider not only the force it produces, usually specified at a particular pressure, but also the air consumption.
Nex Flow manufacturers products for compressed air blow off, cleaning, drying, moving and cooling and also offers related products for filtration and optimization in addition to consultation in their field.