Heat Transfer Modeling and Analysis of Air-Layer Integrated Radiant Cooling Unit

Air-layer Integrated Radiant Cooling Unit (AIRCU) was proposed in 1963, which was characterized by the use of an infrared-radiation transparent (IRT) membrane to separate the unit's radiant cooling surface from its external air-contact surface. Therefore, the unit's radiant cooling surface temperature can be reduced to increase the cooling capacity, while its external air-contact surface, due to the thermal resistance provided by the air layer and the IRT membrane, can be easily maintained at a high temperature to reduce condensation risks. Current work on AIRCU is focusing on the structure design and the identification of suitable materials using a try-and-error or empirical method, lacking a heat transfer model that can assist in analyzing the influences of the optical, physical and thermal properties of the IRT membrane on the performance of AIRCU. This paper, therefore, proposes to establish such a heat transfer model for AIRCU using a two-flux method, which in return can help the selection or specify criteria for the development of materials for the IRT membrane.