To explore the characteristics of pressure pulsation in a twin-screw refrigeration compressor, transient pressures during the suction, compression, and discharge phases were measured, and the pressure pulsation characteristics were subsequently analyzed. The study investigated the effects of operating speed and condensing temperature on pressure pulsation and compared pressure pulsation, noise levels, and the coefficient of performance (COP) in twin-screw refrigeration compressors with slide valve control (SVC) and variable-speed control (VSC) at the same volumetric flow rate. The results indicated that pressure pulsation in a twin-screw refrigeration compressor originates from the periodic fluctuation of pressure and mass flow rate. As the rotation speed increased, pressure pulsation gradually increased from 58.6 kPa at 1380 r/min to 141.0 kPa at 4200 r/min. With an increase in condensing temperature from 34 ℃ to 57 ℃, pressure pulsation also increased from 132.0 kPa to 314.0 kPa. In comparison to SVC, VSC demonstrated significant advantages, featuring more than 54.6% reduction in pressure pulsation, more than 2.9 dB(A) reduction in noise, and more than 5.5% improvement in COP.

The refrigeration industry is advancing towards environmentally friendly, efficient, and safe alternative refrigerants. To analyze compressor performance with various refrigerants, this study proposes a modified semi-empirical model with 13 characteristic parameters. Experiments were conducted with R22, R507, and R744 under variable operating conditions to identify parameters and validate the model. The experimental and simulated results showed strong agreement, with average relative errors of 2.07% for input power and 1.17% for mass flow rate. Using a typical operating condition, the losses and efficiencies of different refrigerants were compared at various frequencies. Results indicate that R744, with the lowest pressure, leakage, and power losses, demonstrated superior performance. While R507 and R22 showed similar efficiencies, the efficiency of R507 declined significantly at frequencies above 50 Hz due to increased pressure losses. This study provides a theoretical basis for optimizing compressor designs for various refrigerants.