Abstract: To address the issue of cooling capacity degradation in household air conditioners under extreme operating conditions (outdoor temperature: 53 ℃, indoor temperature: 35 ℃/26 ℃ as enterprise standards), a high-pressure two-phase injection air conditioning system based on a single-stage vapor compression refrigeration cycle is proposed. First, a theoretical analysis is conducted to evaluate the impact of high-pressure two-phase injection on improving high-temperature cooling performance—specifically, its ability to reduce pressure ratio and discharge temperature at the same compressor frequency. A modified household air conditioner was set up in an enthalpy difference laboratory. With the auxiliary expansion valve opening fixed, key refrigeration system parameters were measured by adjusting compressor frequency and the main valve opening. This allowed analysis of the auxiliary circuit's effect on enhancing system cooling capacity and its influence on compressor operating parameters. Results show that the auxiliary circuit effectively reduces compressor discharge temperature under 53 ℃ conditions, with a maximum reduction of 26 ℃. By increasing frequency, cooling capacity can be improved by 8%, achieving nominal cooling performance. While the auxiliary circuit improves discharge temperature, it may reduce overall system cooling capacity. Therefore, when designing a vapor compression refrigeration system with high-pressure two-phase injection, refrigerant flow distribution between the main and auxiliary circuits must be carefully balanced.

Key words: High-pressure two-phase injection, High temperature cooling, 100% Cooling capacity