Novel hybrid structures to improve performance of miniature flat evaporator loop heat pipes for electronics cooling

Abstract

• Two novel hybrid structures have been proposed to improve performance of miniature LHPs. • A new and simple fabrication process has been proposed for fabrication of hybrid structures. • Hybrid structures have high bond strength, over 100 kPa. • The maximum heat flux is around 7 times higher than that of other polymer heat pipes. Two miniature loop heat pipes (LHPs) with novel hybrid structures of evaporators are developed to cool electronic devices. These structures ensure good heat conduction between evaporators and heat sources and low heat leak from evaporators to compensation chambers through these cases. LHP 1 uses a polymer-glass hybrid structure while LHP 2 uses a polymer-stainless steel hybrid structure. Hydrophilic polytetrafluoroethylene membranes are used as wicks and the working fluid is pure water. The bond strength of these hybrid structures was evaluated quantitatively. Then the effect of hybrid structures on the LHP thermal performance was investigated by measuring temperature at each point. The maximum heat transfer capacity reached 9 W (4.5 W / c m 2 ) and 14 W (7.0 W / c m 2 ) while the thermal resistances were 4.8 K / W and 2.1 K / W for LHP 1 and LHP 2 respectively. Using the polymer-stainless steel structure, the maximum heat flux is around 7 times higher while the thermal resistance is smaller than the corresponding values of other polymer heat pipes.