Comparative analysis of sizing procedure for cooling and water heating cascade heat pump applied to a residential building

Abstract

An appropriate design strategy suitable for the purpose of a building should be considered to apply a cascade heat pump system for multiple functions to buildings. The purpose of this study is to propose a sizing process and evaluate a capacity calculation simulation of air-to-air/water cascade heat pump systems applied in residential buildings that supply indoor cooling and hot water. A simulation study was performed by dividing the capacity calculation method suitable for the building conditions into two cases when this multi-functional cascade heat pump system was applied to a residential building. Case 1 was a sizing method that considered a low-cycle heat pump for indoor cooling. The existing heat pump sizing method for the hot-water supply used in the previous study was set to Case 2. The heat pump simulation and heat calculations were conducted based on thermodynamic theoretical equations. A simulation tool capable of dynamic thermal load analysis was used for model building. Detailed building information was entered in accordance with design standards. The results showed that Case 1 completely satisfies both the cooling and hot-water supply performance of the heat pump compared to Case 2. Based on Case 1, when the temperature of the intermediate heat exchanger was 10 °C higher than the outdoor temperature, the air volume of the indoor unit and the outdoor unit was found to be 941 m3/h at an appropriate air volume rate. In addition, the energy consumption was also the lowest at 2.29 kW h, and the maximum system COP of 6.0 was achieved.