Comparative analysis of heating characteristics of convective-radiant systems using various terminal air source heat pumps

The escalating demand for efficient heating solutions in hot summer and cold winter area has directed substantial attention towards convective-radiant combined systems. These systems offer enhanced comfort while conserving energy. In the context of office buildings, it becomes imperative to consider structural attributes. Under identical operational strategies, disparities in energy consumption and thermal comfort arise from variations in water supply temperature and terminal configurations. Here, we have established a dedicated laboratory to examine convective-radiant heating systems utilizing air source heat pumps. The primary objective is to analyze the impact of distinct heating terminal types and water supply temperatures on indoor thermal comfort, energy consumption, and energy efficiency. By analyzing the dynamics of indoor parameter, and interrelations among air temperature, average radiant temperature, operative temperature, and comfort levels, optimal strategies are determined. Empirical findings demonstrate that independently opening the Fan coil convection system (FC) leads to significant fluctuations in air temperature and creates an unstable heat environment. However, the Radiant floor system (RF) and Convective-radiant combined heating systems (FC+RF) exhibit superior stability in maintaining indoor air temperature. Compared among the three systems, while FC displays the lowest energy consumption upon activation, it compromises comfort levels. Remarkably, there is a strong relationship between operative temperature and Predicted Mean Vote (PMV) for the three systems, with high correlation coefficients of 0.998, 0.999, and 0.997, respectively. Conversely, the association between air temperature and PMV proves weak, with correlation coefficients of only 0.415, 0.469, and 0.841. Consequently, it is advised to prioritize operative temperature as the benchmark for winter air temperature control. For sustained adherence to Level II comfort zone criteria during indoor occupancy, it is recommended to employ (FC+RF) or RF for winter heating. Notably, energy savings of 26.87%, 30.07%, and 32.86% are respectively achieved for (FC+RF), FC, and RF configurations when utilizing a water supply temperature of 35℃ as opposed to 45℃. Hence, the adoption of low-temperature water heating during winter is strongly advocated.