Flexible two-phase thermosyphon for power electronic cooling

A two phase thermosyphon system for power electronic cooling is presented. The designed evaporator can house multiple power electronics modules, it collects the generated vapor to a common flexible tube that drives the vapor to a plate heat exchanger condenser. The system was tested and simulated for a total power loss of 12.5 kW. The condenser was installed at a distance of 3 m from the evaporator enabling flexibility from a customer side concerning location and distance where the heat is finally dumped to ambient. The evaporator is a novel design and it consists of a bottom liquid collector (i.e. it is a pool of liquid constantly feeding the evaporator channels) and a two-phase mixture collector at the top evaporator that collects the discharged two-phase flow and separates the liquid part from the vapor allowing the vapor to travel without liquid to the condenser. The system works with gravity driven circulation. Thermal performances of the system are presented and compared to the simulation results of a dedicated two-phase code developed by ABB. The total power dissipation investigated ranges between 5 and 12.5 kW. This is attained by three power modules Econopack Plus from Infineon. The condensation is provided by means of a water cooled plate heat exchanger. Results will be presented for a cooling water temperature of 38 and 50°C. The working fluid was refrigerant R245fa.