Experimental and theoretical study of a vapour chamber based heat spreader for avionics applications

Abstract

Abstract An experimental and theoretical/numerical study is presented on the behaviour of a vertically placed vapour chamber based heat spreader (190 mm × 140 mm × 15 mm) intended for avionics applications. The experiments were performed with the heat spreader inserted in a mock-up avionics box. The volumetric flow of cooling air was in the range of 5–25 m3/h, that represents current aeronautics on-board conditions and projected values for the mid-term future. Natural convection conditions were also studied because they represent a failure mode of the aircraft air supply system that has to be accounted for in actual design. Boiling inside the vapour chamber was enhanced by implementing a mini-evaporator area (35 mm × 35 mm) made up of an array of mini-fin-pins having the dimensions of 1 mm × 1 mm × 1 mm. The study considered different heat spreader geometries, including a metallic heat sink made up of rectangular fins that was assumed to be the reference configuration. It was found that, from the heat transfer standpoint, vapour chamber heat spreaders were always more efficient, although heavier, than their metallic heat sinks counterparts. In particular, for a component surface temperature in the range of 80 °C–100 °C, the maximum dissipated power varied between 95 and 145 W. Another conclusion of the study was that the benefit of using a heat spreader instead of a metallic heat sink was larger in the case of natural convection conditions. The experimental results were also used to calibrate a theoretical and numerical model of the heat spreader behaviour. To illustrate an application of the model, an optimization process was carried out to find the minimum weight heat spreader compatible with a series of design requirements.