Modeling and test of a thermosyphon loop for the cooling of a megawatt-range power electronics converter

A thermosyphon loop, designed for the thermal management of a large Medium voltage power converter 5 MW overall, corresponding to a 2.4 kW thermal load per cooling unit) is presented. The device is mainly made of an evaporator, a condenser and a reservoir connected with plastic liquid and vapor lines. Novec 649 (3M) has been chosen as the working fluid due to environmental and electrical concerns. A model of the loop is described, and its predictions are compared with experiments. A first comparison yields a maximum mean deviation of 20 % between experimental results and numerical simulation at the maximum coolant temperature. The main sources of errors are identified, and improvements are proposed for better model accuracy.