Keywords: passive cooling, power electronics, losses, coupling, CFD, integral method.

The recent progress obtained with silicon carbide on the performance of electronic systems has opened possible improvements on the cooling system. Instead of using forced cooling, the possibility of passive cooling is investigated, which would reduce the size and weight of the cooling system on trains. This study focuses on the unsteady coupling between the flow past a flat plate and the flux input heating the flat plate. This coupling impacts the temperature response at the interface and is of significant interest regarding the cooling of electronic systems on trains. With the use of two driving behaviours corresponding to two classical phases of train in operation, the interaction between the heat flux and the flow is investigated via two methods. These two driving behaviours are simplified versions of a constant speed phase, with constant losses, and an acceleration phase. An integral method is applied for a laminar incompressible flow to get the temperature evolution over time at different locations on the flat plate for these two cases. CFD simulations for a laminar flow are carried out and compared with the results of the first method. For the first driving behaviour, the agreement is good in the first half of the flat plate considered between the two methods. The differences are more important in the second half. This could be explained by the assumptions made on the boundary layer development. Regarding the acceleration phase, the peaks are well captured, and the match is very good in the temperature evolutions in the first half of the plate.

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