Experimental Study on Heat Transfer Characteristics of Radiant Cooling and Heating

Abstract

While traditional air conditioning systems serve their purpose, radiation air conditioning systems provide several benefits, including improved comfort, higher energy efficiency, and lower initial costs. Nevertheless, the heat exchange capacity per unit area of the radiation plate in such systems is somewhat restricted, which directly affects their practical engineering applications. To address this, experimental investigations were undertaken to examine the impact of cold/hot water supply temperature, water flow velocity, and surface emissivity of radiant panels on their heat transfer characteristics for both summer cooling and winter heating. The findings highlight the significant influence of water supply temperature, flow rate, and surface emissivity on the heat transfer properties of the radiant plates. It is worth noting that adjustments to the water flow rate and surface emissivity impose limitations on enhancing the radiant plate heat transfer performance. For instance, in summer, the heat transfer coefficient of the roughly machined light alumina plate radiant panel was determined by fitting the experimental heat transfer data against characteristic temperatures. Specifically, during cooling, the total heat transfer coefficient of the radiant plate was calculated as 6.77 W/(m2·K), comprising a thermal coefficient of 5.41 W/(m2·K) and a convective heat transfer coefficient of 4.17 W/(m2·K). Conversely, during winter heating, the total heat transfer coefficient of the radiant plate increased to 8.94 W/(m2·K), with a radiation heat transfer coefficient of 6.13 W/(m2·K) and a convective heat transfer coefficient of 3.79 W/(m2·K).