Advanced Capillary Structures for High Performance Heat Pipes

Abstract

High performance heat pipes are widely used for the thermal control of electronic devices. Concerning heat transport limitations, typical wick or capillary structures show advantages in some aspects and disadvantages in others. An advanced capillary structure was developed with high thermal effectiveness, low axial pressure drop, high capillary pressure, and a high boiling limit. It combines open minichannels with open microchannels that are manufactured perpendicular on top of the minichannels. The heat transfer coefficient in the evaporator zone, which is a characteristic value for the thermal effectiveness, was up to 3.3 times higher compared to a similar structure without microchannels. A model that combines micro- and macroscopic phenomena was developed. It predicts the heat transfer coefficient with quite good accuracy as long as the microchannels are at least 300 μm.

Acknowledgments

The authors kindly acknowledge the financial support of the European Space Agency (ESA) and the German Aerospace Center (DLR) within the CIMEX-project (Convection and Interfacial Mass Exchange). The authors thank European Heat Pipes S.A. (EHP, Nivelles, B) for manufacturing the flat re-entrant groove plates.