Performance enhancement of a two-phase closed thermosiphon with a thin porous copper coating

In this study, the heat transfer augmentation of a two-phase closed thermosiphon (TPCT) with a thin, porous copper coating is studied and compared with an uncoated TPCT. The inner surface of the TPCT is coated using an electrochemical deposition process. The coated and uncoated TPCTs are filled with deionised water and tested with a heat input of 50 to 250 W. The heat transfer coefficient in the evaporator and condenser is assessed and compared with the thermal resistance of coated and uncoated TPCTs. The effects of the inclination angle, power input and thin copper coating on the performance of the TPCTs are explored. The heat transfer coefficient of the evaporator is found to be enhanced up to 44% at a heat flux of 10 W/m2 for an inclination angle of 45°. TPCTs with an oxide coating are also compared to those with a metallic coating and the metal-coated TPCT was found to perform better than the oxide-coated TPCT. The effect of non-dimensional numbers, such as Bond (Bo), Webber (We), Kutateladze (Ku) and condensation (Co) numbers, with the variation of heat flux, is also investigated.