Experimental and optimization study on time and pressure effects in a vortex refrigeration unit

This work focusses on the design, fabrication, experimentation, and optimization of a vortex refrigeration system, emphasizing the effects of inlet pressure, valve position, and operating duration on system performance. The tests were performed by changing the inlet pressure from 3 to 6 bar, with a total test duration of 5 min, and hot-end valve openings of 3, 6, and 9 rotations. The fabricated unit operates on the vortex principle, generating distinct hot and cold streams through inner and outer vortex formations, with the valve position significantly influencing flow behavior. Experimental results revealed an isentropic temperature change of 12.82 °C, an isentropic efficiency of 77%, a higher cold-end temperature drop of 13.2 °C, a hot-end temperature rise of 40 °C, heat transfer rates of 162 W (cold end) and 38 W (hot end), and coefficients of performance (COP) at cold and hot ends equal to 2.25 and 1.15, respectively. The system exhibited optimal performance at six valve rotations, beyond which a marginal decline was observed. Optimization analysis further identified 6 bar as the optimal inlet pressure, yielding a cold-end temperature drop of 16 °C, a COP of 2.25, an isentropic efficiency of 71%, and heat transfer rates of 115 W and 30 W at cold & hot ends, respectively.