An Experimental Study of a Multi-port Vapor Injected Scroll Compressor

Previous research indicates that a scroll compressor with multiple vapor injection ports has the potential to significantly improve the energy efficiency and maintain high heating capacity of vapor compression heat pumps, particularly at low outdoor temperatures. Based on a tradeoff between cost and benefit, a dual-port vapor injected compressor prototype was chosen for testing to provide the experimental results. The overall performance of the heat pump system employing the compressor prototype is analyzed. Coupling the compressor testing results into a three-stage expansion vapor injection flash tank cycle model, the operating injection pressure can be determined under a certain working condition. The results showed that both lower and higher injection pressures and the corresponding injected mass flow rates decreased with an increase of pressure ratio of discharge pressure to suction pressure. Comparing the COP of the vapor injection cycle with the one of a baseline cycle, the improvement in COP increased with an increase of the pressure ratio and goes up to 19% at a pressure ratio of 8 and a condensing temperature of 43.3°C. In addition, the proposed technology leads to higher energy efficiency and less degradation in heating capacity at low ambient temperatures. For Minneapolis, the seasonal efficiency (heating) of the vapor injection cycle was 13% higher than that of the standard vapor compression cycle.