Anti-condensation Characteristics of High Permeability Films for Radiation Air Conditioning in Typical Urban Indoor Environments of Different Climate Zones

Radiant cooling air conditioning systems offer energy savings and thermal comfort; however, the dew problem limits their application and popularization. In this study, a method of applying an infrared high-permeability film to a cold plate was proposed to increase the temperature of the contact surface between the infrared high-permeability film and indoor air while ensuring the radiation cooling capacity of the air conditioning system. This reduces the risk of condensation. A heat transfer model of an infrared transmitting film for radiation refrigeration was constructed, and the influence of the infrared transmittance of the highly permeable film on dew point temperature and radiant cooling capacity was calculated. In addition, the minimum transmittance and corresponding maximum cooling capacity of natural ventilation for preventing condensation in typical cities of different climate zones were predicted, and the effect of the infrared transmittance of the high permeability film on human thermal comfort was evaluated. The results show that the radiant heat transfer model can accurately predict the heat transfer process at the membrane surface. Under the premise of ensuring radiation cooling capacity, the transmission film can increase the dew point temperature by 4 ℃-17 ℃. The minimum transmittance required by different cities vary, with Hohhot and Chongqing having the lowest and highest rates of 0.4 and 0.95, respectively. Infrared transmission films can be used as a novel method to prevent condensation on the cold walls of radiant air conditioning systems. This study thus provides a reference for the design and selection of transmission films.