Applicable design of multi-functional cascade heat pump system for an office building

Abstract

When the cascade heat pump system is applied as a multi-functional system that can be used not only for hot water supply but also for air-conditioning of buildings, the low-stage cycle is responsible for indoor heating and cooling thermal load, and the high-stage cycle is responsible for hot water supply by raising the refrigerant temperature. Unlike the existing cascade heat pump system designed with only one operation mode for hot water supply, the multi-functional cascade heat pump system should be considered with various parameters. This study was proposed a design sequence of the cascade heat pump system for building application, and the energy-saving performance was compared with the existing cascade heat pump system for hot water supply and parallel heat pump system for air-conditioning. The office building was set for the study, and the thermal load of the building was calculated in the TRNSYS program. The systems were calculated using the thermodynamic equation and the model built into EnergyPlus. As a result, the system can be affected by the outdoor air heat source. The energy-saving performance was 25% for the multi-functional cascade heat pump system compared to the simultaneous use of the existing system.