Effects of vapor injection techniques on the heating performance of a CO2 heat pump at low ambient temperatures

Abstract The objective of this study is to investigate the effects of vapor injection techniques on the heating performance of a CO2 heat pump. The performances of the flash tank vapor injection (FTVI), sub-cooler vapor injection (SCVI) and FTVI with a suction line heat exchanger (FTSX) cycles were measured and analyzed with variations of the outdoor temperature, compressor frequency, and injection mass flow rate. At the outdoor temperature of −15 °C and compressor frequency of 55 Hz, the heating capacity and COP of the optimized SCVI cycle were 12.1% and 12.7% higher than those of the optimized FTVI cycle, respectively, because the total mass flow rate in the SCVI cycle was higher than that in the FTVI cycle by the large temperature and pressure differences in the sub-cooler of the SCVI cycle. In addition, the optimum injection flow rate ratios in the vapor injection CO2 cycles yielding the maximum COP were determined at various compressor frequencies.

[1]  Jaehyeok Heo,et al.  Optimal control of the gas-cooler pressure of a CO2 heat pump using EEV opening and outdoor fan speed in the cooling mode , 2013 .

[2]  Min-Soo Kim,et al.  Comparison of the heating performance of an inverter-driven heat pump system using R410A vapor-injection into accumulator and compressor. , 2012 .

[3]  Mo Se Kim,et al.  An Experimental Study on the Performance of CO₂ Air-conditioning Cycle Equipped with an Ejector , 2009 .

[4]  Jaehyeok Heo,et al.  Comparison of the heating performance of air-source heat pumps using various types of refrigerant injection , 2011 .

[5]  Honghyun Cho,et al.  Cooling performance of a variable speed CO2 cycle with an electronic expansion valve and internal heat exchanger , 2007 .

[6]  Akio Miyara,et al.  WAYS OF NEXT GENERATION REFRIGERANTS AND HEAT PUMP/REFRIGERATION SYSTEMS , 2012 .

[7]  Jahar Sarkar,et al.  TRANSCRITICAL CO2 REFRIGERATION SYSTEMS: COMPARISON WITH CONVENTIONAL SOLUTIONS AND APPLICATIONS , 2012 .

[8]  Reinhard Radermacher,et al.  PERFORMANCE OF CO2 CYCLES WITH A TWO-STAGE COMPRESSOR , 2004 .

[9]  Guoyuan Ma,et al.  Experimental study of a heat pump system with flash-tank coupled with scroll compressor , 2008 .

[10]  Jaehyeok Heo,et al.  Optimum cycle control of a two-stage injection heat pump with a double expansion sub-cooler , 2012 .

[11]  Jahar Sarkar,et al.  Optimization of two-stage transcritical carbon dioxide heat pump cycles , 2007 .

[12]  Jong Min Choi,et al.  TECHNOLOGY REVIEW OF TWO-STAGE VAPOR COMPRESSION HEAT PUMP SYSTEM , 2013 .