Experimental investigation of vortex tube and vortex nozzle for applications in air-conditioning, refrigeration, and heat pump systems

The Ranque-Hilsch vortex tube can separate an incoming high pressure fluid stream into two low pressure fluid streams with different temperatures. In this project, the applicability of expansion work recovery through vortex tube in heating and cooling cycles has been examined. Vortex tube thermal separation performance for air, R134a and carbon dioxide is provided. It has been found that when using single-phase vapor as the working fluid the vortex tube cold end temperature can always be lower than the isenthalpic expansion temperature, and whether the hot end temperature is higher than the inlet temperature depends on whether the fluid shows ideal gas behavior. Suitable vortex tube operating conditions are identified. Vortex tube cold-side isentropic efficiencies are measured to be higher than 20% for different fluids. Based on this knowledge, cooling and heating cycles with vortex tube have been proposed and their performance is calculated. Expansion work recovery by two-phase ejector is known to be beneficial to vapor compression cycle performance. However, one of the biggest challenges with ejector vapor compression cycle is that the ejector cycle performance is sensitive to working condition changes which are common in real world applications. Different working conditions require different ejector geometries to achieve maximum performance. Slightly different geometries may result in substantially different COPs under the same conditions. The ejector motive nozzle throat diameter (motive nozzle restrictiveness) is one of the key parameters that can significantly affect COP. This thesis presents a new two-phase nozzle restrictiveness control mechanism which is possibly applicable to two-phase ejectors used in vapor compression cycles. This new control mechanism has the advantages of being simple and potentially less costly. It can also possibly avoid the additional frictional losses of previously proposed ejector control mechanisms using adjustable needle. An adjustable nozzle based on this new control mechanism is designed and manufactured for experiments with R134a. The experimental results show that, without changing the nozzle geometry, the nozzle restrictiveness on the two-phase flow can be adjusted over a wide range. Under the same inlet and outlet conditions, the mass flow rate through the nozzle can be reduced by 36% of the full load. This feature could be very useful for the future application of ejectors in mobile or stationary systems under changing working conditions