Cooling load characteristics of indoor spaces conditioned by decoupled radiant cooling unit with low radiant temperature

Decoupled radiant cooling units (DRCUs) are capable of increasing the cooling capacity without increasing condensation risks even using a much lower cooling temperature than conventional radiant cooling units (CRCUs). However, it is unclear whether DRCUs using low radiant cooling temperature will increase the cooling load of the conditioned indoor spaces. In this study, the cooling load characteristics of a thermal chamber conditioned by a DRCU was investigated through developing a steady-state analysis model suitable for both DRCUs and CRCUs. The total/radiative heat flux, as well as the heat exchange with a thermal manikin and walls were analysed under different surface temperatures of DRCUs. The effect of the emissivity of the thermal chamber' external wall on the cooling load was also investigated. Results indicated that the cooling load under the DRCU was slightly smaller than that under the CRCU when the same operative environment was created. Decreasing the infrared emissivity of the exterior wall's inner surface could lead to a significant decrease in the cooling load for both the DRCU and CRCU. By decreasing the wall emissivity from 0.9 to 0.1, the total cooling load of the DRCU can be decreased by 8.4% and the heat gain of the exterior wall decreased by 21.6%. This study serves as a reference for developing the analysis model and understanding the load characteristics when DRCUs are used to create the thermal environment for indoor spaces.