Experimental Investigation of Gravity-Driven Two-Phase Cooling for Power Electronics Applications

Passive cooling approaches are ideal for high reliability systems, like most power electronics applications, because they require no moving parts and little maintenance. Two-phase cooling systems have offered these benefits to system designers for decades through capillary-based products like heat pipes. The boiling and condensation process within a two-phase system is very effective at moving heat with minimal temperature gradient. However, capillary-based two-phase systems are not able to handle the high demands of current power electronics applications. Some gravity-based two-phase cooling solutions, like loop thermosyphons, provide a higher performance alternative to current passive cooling solutions. This paper will discuss the recent developments and experimental evaluation of a gravity-driven two-phase cooling solution for medium voltage drive applications. Various performance parameters like fluid charge and working fluid were examined to determine their effect on system flow rate, thermal resistance, local heat transfer coefficient, and maximum power capability.