Session: 06-05 Thermal Management Applications 2

Paper Number: 97289

97289 - Effects of the Micro-Post Array on the Operating Limit of a Micro Pulsating Heat Pipe 

This study is performed to experimentally investigate effects of the micro-post array (MPA) on the operating characteristic of a micro pulsating heat pipe (MPHP). The MPA has been widely used to prevent the dryout and increase the operating limit because the MPA can supply the liquid to the dryout spot by the capillary flow in the MPA. The MPHPs with and without the MPA are fabricated for the experiments. The overall dimension of the MPHP is 53 × 38 × 1.5 mm³. There exist channels with ten turns in the MPHP, and the width and the height of the channels are 1.5 mm and 0.66mm, respectively. The length of the evaporator section and the condenser section in a channel are 7 mm and 12 mm, respectively. The MPA is placed on bottom surfaces of the channels, and the dimensions of the MPA are determined to maximize the velocity of the capillary flow induced by the capillarity in the MPA: The velocity of the capillary flow is estimated by using the Brinkman-extended Darcy's equation. Also, the MPA is placed in three different arrangements in each three MPHPs: in alternating pairs of channels, in alternating channels, and in all channels, respectively. The experiments are conducted in a horizontal orientation, and the working fluid is determined to be ethanol with the filling ratio of 52%. Experimental results are twofold: if the MPA is placed in alternating pairs of channels or in alternating channels, the operating limit of the MPHP is increased due to the prevention of the dryout by the capillary flow. However, if the MPH is placed in all channels, the MPHP cannot normally operate due to the existence of the pinning forces in all channels. Therefore, for the favorable effect of the MPA to the MPHP, the MPA should be placed in alternating channels or in alternating pairs of channels.

Presenting Author: Young Jong Lee KAIST (Korea Advanced Institute of Science and Technology)