The Thermal Performance of Graphite Heat Spreaders in Radiant Panel Applications

Abstract

Hydronic radiant floor heating systems are recognized as an efficient means of heating residential and commercial buildings. These systems utilize water flowing in tubes to move thermal energy from a heat source to a radiant panel located beneath the floor of the room being heated. The efficiency of such systems depends on many factors but a major concern is the ability of the radiant panel to remove heat from the water tubes and spread it effectively across the floor. Conventional radiant panels use aluminum heat spreaders to do this. Much work has been done to determine the overall performance of rooms heated by radiant panels, but little work has been done to measure the thermal performance of heat spreaders in these panels. This paper describes the development of a test method, using thermal imaging of test panels, to measure the performance of these heat spreaders. This method is used to determine the thermal performance of commercially available aluminum heat spreaders and of advanced heat spreaders made from flexible graphite. Graphite heat spreaders have found wide acceptance in a variety of electronic applications including plasma and LED displays, laptop computers and cell phones. This paper also examines the thermal properties of graphite that make it attractive as a radiant panel heat spreader. The development of high thermal conductivity, flexible graphite spreaders for various radiant panel applications is described. These graphite heat spreaders improve the performance of radiant panel systems and allow the use of high efficiency, low temperature heat sources.