The performance of a closed cavity radiation system with built-in heat exchanger

Radiant ceiling systems have good comfort levels and energy savings. However, traditional radiant air conditioning systems have many problems, such as condensation forming on the cooling surface, insufficient cooling capacity, and complex structure and control. In this paper, a closed cavity radiation system with a built-in finned heat exchanger is proposed and the heat transfer mechanism, heat transfer performance, and operation characteristics of the system are analysed. The results show that the direct-expansion large-temperature-difference heat transfer method, with refrigerant as the working medium, realises the required cold supply through the low-temperature working medium and the required heat supply through the high-temperature working medium. Heat is transferred to or from the ceiling through a multi-stage strength buffer and direction conversion so that the ceiling respectively forms a hot or cold radiant plate with uniform temperature for indoor heat exchange. The heat transfer efficiency is more than 90%, which greatly improves the cooling or heating potential of the heat exchanger, reduces the required heat exchanger area, and simplifies the installation structure. In this study, the installation area of the finned heat exchanger only accounted for 14% of the ceiling. In practical application, the number of finned heat exchanger plates can be determined according to the cooling and heating load demand, providing a reference for new radiant air conditioning system design.