Radiation and Free Convection Shield for Passive Thermal Control

Abstract

A radiation and free convection shield (RFS), when used with a thermal storage wall, can enhance the thermal performance of the storage wall and provide passive thermal control. In order to optimize the performance of the RFS, it is desirable to know how the impedance provided by the use of an RFS varies with the thermophysical properties of materials used to construct it. A numerical nodal thermal model was constructed to evaluate the impedance as a function of the thermophysical properties of the RFS. Two RFS thermophysical properties are identified as the most important in controlling the impedance from the storage wall to the room: thermal conductivity and total surface emissivity. A decrease in the RFS surface-to-surface thermal conductance, a decrease in the RFS total surface emissivity, or both, substantially increases the impedance from the storage wall to the room.