Experimental study on two-phase flow and thermal performance in pulsating heat pipes

Abstract

Pulsating heat pipes have shown great potential in the field of engineering applications, such as the cooling of microelectronic devices. The correlation between the flow characteristics and the thermal performance of the heat pipe still needs to be further explored. In this paper, the operation state and flow patterns inside pulsating heat pipes with two inner diameters of 1 and 2 mm are experimentally visualised and analysed. The effect of the inner diameter on the thermal performance of heat pipes is evaluated. The results indicate that the operating modes, including small pulsations, bulk pulsations and circulation are sequentially obtained in pulsating heat pipes with the increase of the heat input. The decrease of the inner diameter of pulsating heat pipes results in the capillary instability and the increase of the flow frictional resistance. When the filling ratio is 55%, the thermal performance of a pulsating heat pipe with an inner diameter of 2 mm is better than that of a pulsating heat pipe with an inner diameter of 1 mm.