Vortex tube without compressed air

Question

I am looking for an apparatus to cool/heat air without moving parts and using only a pressure source. From this, I came to a "vortex tube". However, all practical implementations are based on compressed gas used at the inlet tube.

Now my question is:

Would the "vortex tube" also work by applying an underpressure (using a vacuum pump) at one of the "outlets"? In addition, one of the "outlets" and the "inlet" would then be at athmospheric pressure.

The goal I would like to reach is to apply an underpressure at one side of an apparatus and thereby heating/cooling the air. Thermodynamically this should be possible since energy is put into the system via the applied underpressure, however I cannot think of any other apparatus other than the vortex tube.

Maybe there are other possibilities that I am unaware of? Thanks!

(Additional detail: an underpressure of 1 to 6 kPa is applied)

Answer 1

Relying on underpressure will only work if you make both outlets at low pressure. This would then be symmetric with the compressed air case.

The vortex tube works because the conical nozzle at the end permits only the outer ring of gas (which is the hottest part). The rest is forced to escape out the other end, with the counter vortex.

Were you to simply apply underpressure to one outlet, the result would simply pull air from both the inlet and the other outlet. The result would smoothly pull all air out, not just the outer ring.

It's also worth noting that there will be a limit on the efficiency of this device, even if you manage to get it working (such as by applying underpressure to both outlets). Most vortex tubes are run at 100psi, but a vacuum is limited to pulling 14 psi (atmospheric pressure).

Answer 2

the easiest way to get cooling from a pressure source is by using compressed air as both the working fluid and the ventilation source. This is how it is done in commercial aircraft: compressed air is bled off the compressor section of the engine, run through a heat exchanger to cool it, and run through a throttling orifice to drop it down to cabin pressure. If you have a good heat exchanger, the air exiting the throttling valve will be very cold. This is (sometimes) called an open-cycle air chiller. The unit that accomplishes this in an airplane is called an AC Pack.