Abstract:

An experimental investigation into the heat transfer characteristics of flattened sintered micro heat pipes in different thicknesses was conducted,and the filling ratio of the working fluid was optimized for the pipe with a flattening thickness of 5 mm,namely a vacuum cavity thickness of 3 mm. Moreover,the effects of flattening thickness on the axial temperature distribution,the maximum heat transfer rate ( MHTR) ,the temperature difference and the thermal resistance of the micro heat pipe were analyzed at constant filling ratio. The results indicate that the thickness only has a slight effect on the MHTR when the working liquid quantity is a little less than that fully fills the wick ( mc ) ,and that the MHTR reaches 40,50 or 60W when the thickness is 5,4 or 3mm,respectively. On the contrary,when the working liquid quantity is more than mc,the thermal performance of the pipe degrades with the decrease in flattening thickness,the thermal resistance increases from 0. 15℃ /W to 0. 20℃ /W if the thickness decreases from 5mm to 4mm,and the heat pipe fails at a thickness of 3mm. Moreover,by analyzing the causes of the above-mentioned findings,it is concluded that the change of thermal performance of the heat pipe is due to the
thickness change-induced distribution variation of in-pipe working liquid.

Key words: micro heat pipe, heat transfer characteristic, flattening thickness, temperature difference, thermal
resistance