Search

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.

The energy consumption of the air-source heat pump operated in cooling mode is affected by the outdoor air condition in summer. It is important to not only install the evaporative cooler in front of the condenser inlet side but also consider the operation strategy of the evaporative cooler under the hot and humid condition. In this study, the energy saving potential of the air-source heat pump with an evaporative cooler was analyzed according to the operation strategy. A three-story office building measuring 100 m2, using an enthalpy recovery ventilator, was used as a model building conditioned by the proposed system for detailed energy simulation. The building thermal load and energy consumption were estimated using simulation tools. The results show that the proposed system reduces 8.87% of energy consumption compared with the conventional air-source heat pump when the evaporative cooler operated under the 72% of relative humidity condition.