A study on the evaporation heat transfer in the cooling of high power electronics

The cooling of a high power motor controller has been studied for more than two years. The total power dissipation in the controller is estimated to be in the order of 20 kW. We chose to use pool boiling inside a enclosed volume for thermal management. This paper is concerned with the evaporation part of the cooling system. The primary concern has been the cooling of the “hockey puk” GTO´s having an expected power dissipation in the order of 1 kW. To increase the effective area for evaporation heat transfer, the components have been clamped between cooling “blocks”. We found however that a notable part of the heat was transferred directly from the GTO capsule itself into the liquid. This was dependent on the degree of liquid subcooling and the total pressure. The thermal resistance in the cooling blocks contributed significantly to the total temperature loss. The temperature gradients depended heavily upon the local heat transfer from cooling block to liquid. FEM simulations have been used to model the temperature distribution in the cooling blocks as a function of heat transfer coefficients