Simulation-based comparative seasonal performance evaluation of single-stage heat pump and modulated two-stage injection heat pump using rotary compressors with various cylinder volume ratios

In this study, the comparative seasonal performance evaluations of single-stage heat pump, two-stage injection heat pump, and modulated two-stage injection heat pump using rotary compressors are conducted using a heat pump simulation model. The heat pump simulation and optimization models are developed and validated. The operating parameters are optimized by genetic algorithm to achieve the maximum energy efficiency ratio (EER) and coefficient of performance (COP) at a given outdoor temperature. Moreover, the optimal lower compressor volume and cylinder volume ratio are determined to maximize the seasonal EER (SEER) and seasonal COP (SCOP) at the given weather conditions. The EER and COP of the two-stage injection heat pump are improved substantially at high cooling and heating load conditions, respectively. However, since the two-stage injection heat pump is not effective to improve the SEER owing to the lower performance at the low cooling load conditions, the modulated two-stage injection heat pump is introduced. Consequently, the SEER and SCOP of the modulated two-stage injection heat pump are 6.0% and 1.4%, respectively, higher than those of the single-stage heat pump at the cooling and average heating conditions.