The Application Of Vortex Tubes to Refrigeration Cycles

The vortex tube is a structurally simple device with no moving parts that is capable of separating a highpressure flow into two lower pressure flows with different energies, usually manifested as a difference in temperatures. The vortex tube is relatively inefficient as a stand-alone cooling device but it may become an important component of a refrigeration system when employed as an alternative to the conventional throttling valve. A cycle augmented with a vortex tube can offer several advantages including: efficient operation above the JouleThomson inversion curve, relative insensitivity to heat exchanger size, and the ability to operate with a lower pressure ratio. The extent to which these advantages are realized depends on the cycle configuration, the fluid properties, the operating conditions, and the behavior of the vortex tube. In this paper, a semi-empirical model of the vortex tube is presented using one hypothesis regarding its underlying physics. Predictions made using this model are found to compare favorably with the limited experimental data that are available. The vortex tube model is integrated into a model of a vapor compression refrigerator and a Joule-Thomson cryogenic refrigerator. The potential for increasing the performance of a refrigeration cycle using the vortex tube is found to be extremely limited for the vapor compression cycle. However, it is shown that the vortex tube may present a significant opportunity to improve the performance of refrigeration systems using the Joule-Thomson cycle and may allow efficient operation at lower pressure ratios, with smaller recuperative heat exchangers, and with less expensive working fluids than are currently used. More complex cycles are discussed in which the vortex tube can be used to simultaneously perform phase and energy separation.