Condensation-free radiant cooling with double-skin infrared-transparent membranes

Radiant cooling has been well acknowledged as high-performance space cooling technique owing to the advantages of thermal comfort and energy efficiency. However, there are two problems (viz., condensation risk, and insufficient cooling capacity) which hinders their application in hot and humid climate zones. Herein, a condensation-free radiant cooling was demonstrated by covering cooling source with double-skin infrared-transparent membranes (DIMs). The DIMs' surface instead of the cooling source surface served as the air-contact surface while maintaining infrared radiant transfer from cooling source to cooling load. Therefore, the DIMs’ surface temperature was maintained above the dew point for condensation-free safety while the cooling source temperature could be lower for improving cooling capacity. A heat transfer model was presented to predict the cooling capacity. The calculated results were validated with the measured data on a reduced-scale radiant cooling setup by using commercial polyethylene for the DIMs with an error smaller than 5%. The results indicated that the cooling capacity with DIMs at cooling source temperature of 7 °C was 104.0 W/m², 48% improved compared to conventional radiant cooling. It will be of great guidance for high-performance radiant cooling design without condensation and improved cooling capacity. Concerning size difference of the reduced scale demonstration in this work with real scale application more accurate and detailed investigations (e.g. cooling capacity, air-tightness and mechanical strength) on the condensation-free radiant cooling should be carried out in further work.