In this study, a simultaneous heating and cooling multi heat pump having four indoor units and an outdoor unit was designed and constructed. The working of the system was R-410A. The operating characteristics and performances of the heat pump system were measured at five operation modes: cooling-only, cooling-main, heating-only, heating-main and entire heat recovery operation. To improve the system efficiency and reliability, the system in the heat recovery operation was optimized by varying the compressor rotation speed and EEV opening. In the simultaneous heating and cooling operation, the system COP increased by using the heat recovery operation with the optimization of control parameters.
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