Effects of vapor injection techniques on the heating performance of a CO2 heat pump at low ambient temperatures |
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| Affiliation: | Department of Refrigeration & Cryogenic Engineering, School of Energy and Power Engineering, Xi''an Jiaotong University, Xi''an 710049, China;Department of Chemical Systems Engineering, School of Chemical Engineering, University of Campinas, Av. Albert Einstein, 500, Bloco A, Campinas, São Paulo CEP 13083-852, Brazil |
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| 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. |
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| Keywords: | Compressor frequency Heating performance Injection ratio Two-stage Vapor injection Fréquence du compresseur Performance de chauffage Taux d' injection Biétagé Injection de vapeur |
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