Passive Thermal Management of Launch Vehicle Systems using Phase Changing Materials

Electronic systems in expendable launch vehicles and missiles rely on their own thermal inertia to operate for the stipulated time, without overheating, owing to absence of active cooling systems and natural convection at elevated altitude. Traditionally, this inertia is built-into the electronics by increasing its chassis (support structure) mass, proportional to the associated thermal load. For power intensive systems, especially in vehicle upper stages where mass is at premium, this approach results in proportional reduction in payload capability. In the present paper, a heat sink based on Neopentyl Glycol (NPG) with solid-to-solid phase change (crystalline transformation) is explored as a mass effective alternative due to its capability to absorb a significant amount of energy during phase change. However, due to its lower thermal conductivity, a thermal conductivity enhancer (TCE) to maximise heat transfer is essential. The resulting heat sink, utilising TCE for heat distribution and NPG for heat storage can be called hybrid heat sink. A heat sink utilising plate type fins as TCE is realised wherein a mass reduction factor (MRF) of 1.4 is achieved against traditional approach. This is followed by a heat sink with pin type fins as TCE and a MRF of 2.6 is achieved. Effect of thermal cycling and vibration on its performance is also studied.