Performance evaluation of a water-to-water heat pump with a floor panel heating system

The performance of heat pump is severely degraded as the temperature of the heat source is decreased. For air source heat pumps, this results in a serious mismatch of heat pump output and space heating demand. Although the outdoor temperature is below 0°C, the use of a water-to-water heat pump with a floor panel heating system can operate for extended periods of time without frost-defrost cycling and therefore at a high seasonal efficiency. This paper focuses on the performance of a water-to-water heat pump that uses well water as a heat source and a floor panel heating system as a sink. Field tests of a water-to-water heat pump combined with the floor panel heating system in a heavily insulated miniature test house were conducted to obtain its cyclic performance as well as the seasonal performance. The test house, which had a floor area of 27.5 m², consisted of three rooms that were equipped with panel heating coils under floor surface. The heating capacity of the water-to-water heat pump was 3.95 kW with double tube heat exchangers. The averaged COP of the water-to-water heat pump system was measured for every cycle throughout the intermediate season and analyzed as a function of outdoor temperature. The cyclic performance such as part load factor, cyclic operation performance, and degradation coefficient degraded as the outdoor temperature increased, because of relatively increasing off-cycle duration in the cycle as well as lengthening of the cycle duration.