캐스케이드 히트펌프의 냉매유로별 공기난방 및 급탕 성능 비교 분석

Abstract

This study aims to perform a comparative analysis of a cascade heat pump system performance according to therefrigerant flow settings in two operation modes. The hot-water-only heating mode was set as a reference mode. The airand water heating mode was the proposed operation mode. The manufactured heat pump system was installed in the basementof the experimental building at the Korea Institute of Energy Research in Daejeon, Korea. The refrigerants R410A and R134awere applied in low-cycle and high-cycle, respectively. A geothermal source was used to conduct the experiment. Five levelsof the by-pass valve opening rate was selected: 0%, 25%, 50%, 75%, and 100%. Results showed that the supply air temperaturehad a positive correlation with the by-pass valve opening rate. The maximum indoor supply air temperature was 28.86°C.Meanwhile, there was no clear correlation with the hot water temperature. The energy consumption showed that the proposedmode consumed 6.13 kW, whereas the reference mode consumed 6.64 kW at 100% opening rate. The total heating rateof the indoor air and water was 17.25 kW and 17.62 kW in the reference mode and proposed mode, respectively. Therefore,the total system coefficient of performance of the proposed mode was 6%-16% higher than that of the reference mode atdifference opening rates. This was because the compression ratio of the proposed mode was 19% lower than that of thereference mode in the low-cycle heat pump.