| Abstract | This study aims to perform a comparative analysis of a cascade heat pump system performance according to the refrigerant flow settings in two operation modes. The hot-water-only heating mode was set as a reference mode. The air and water heating mode was the proposed operation mode. The manufactured heat pump system was installed in the basement of the experimental building at the Korea Institute of Energy Research in Daejeon, Korea. The refrigerants R410A and R134a were applied in low-cycle and high-cycle, respectively. A geothermal source was used to conduct the experiment. Five levels of the by-pass valve opening rate was selected: 0%, 25%, 50%, 75%, and 100%. Results showed that the supply air temperature had 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 proposed mode consumed 6.13 kW, whereas the reference mode consumed 6.64 kW at 100% opening rate. The total heating rate of 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 at difference opening rates. This was because the compression ratio of the proposed mode was 19% lower than that of the reference mode in the low-cycle heat pump. |
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