Every once in a while the above application for cooling with a Vortex Tube comes to us from a customer looking to cool down a gas sample before it goes into a gas chromatograph for analysis. The sketch above is a very good illustration of how the customer might go about cooling down their gas sample. The “cooler” is essentially a metal tube into which either copper or stainless steel tubing is added in a coiled section. A valve controls the inlet flow of gas from the process. The Vortex Tube purges and cools the space between the inner coil and the outer wall of the housing to provide temperature differential for the thermal transfer to occur. The outlet for the cooled gas is connected to the analyzer and there is a third port for the cold compressed air to escape back out from the housing.
The question from the customer was what size Vortex Tube should they consider for the application. Fortunately from previous experience we know that one of our medium size vortex tubes, model 3225 provides good, all around cooling for these applications. The specific cooling power required depends on a variety of factors including start temperature, finish temperature, cold air temperature and the efficiency of the heat exchanger itself. The volume of flow for both the cooling medium and the vortex tube cold flow also play significant roles.
In many cases, the customer isn’t going to know all of the factors involved and are willing to make a test with their cooling system. In such cases, EXAIR has an experimental Cooling Kit model 3930 that allows the user to change to different flow rates and adjust to different temperatures on the cold flow to increase or decrease cooling power as needed per their test result.
In the past, water was the cooling medium of choice. Water cooled systems are effective and can provide a higher maximum cooling value. But water brings with it a whole different set of challenges that many folks do not want to deal with. Water cooled systems inherently leak which creates additional housekeeping and safety issues. This convenience of not being messy makes vortex tube cooling a very attractive option.
Neal Raker, Application Engineer