Assessment of vapour chamber heat spreader implementation for avionic module thermal management

Thermal management of aircraft heat loads is quickly becoming a limiting factor of vehicle performance and reliability. This paper details improvements in forced-convection cooled avionic module heat removal efficiency with the implementation of two-phase high thermal conductivity Vapour Chamber Heat Spreaders (VCHS). A bespoke test rig provides experimental thermal comparisons of an aluminium and embedded VCHS avionic heat exchanger. The experimental results validate a numerical thermal resistance network, which is utilised to simulate more representative avionic chassis geometries. The VCHS dramatically reduces thermal variation in circuit card and avionic heat exchanger exhaust temperatures. Increased isothermalisation of the heat exchanger greatly increases effective heat transfer area in comparison to a traditional aluminium chassis. The VCHS acts as a very effective thermal buffer between the avionic circuit cards and coolant airflow, allowing a more predictable avionic thermal behaviour irrespective of circuit card architecture. The improved heat rejection capability allows either a substantial increase in avionic growth capacity (increased power output for a fixed exhaust temperature) or a substantial reduction in mass flow rate (reduced demand on vehicle thermal management system). An avionic growth capacity of up to 58% is achieved with representative thermal loading conditions.