The effect of liquid supply due to capillary action on a critical heat flux enhancement using a honeycomb porous plate in a saturated pool boiling

Abstract

Pool boiling is used for cooling in numerous thermal energy dissipation systems because of its high heat flux removal capacity. However, the heat removal in a pool boiling is limited by the occurrence of critical heat flux conditions (CHF), the primary concern in the thermal management requiring high heat flux removal is CHF enhancement. For such systems, we have ever proposed a technique to enhance the CHF in saturated pool boiling using a honeycomb porous plate. This cooling technique enhanced the CHF by more than a factor of two (2.5 MW/m²) compared with that of a plain surface. The plausible mechanisms for the CHF enhancement are liquid supply through (1) capillary action and (2) vapor escape channels from the top surface due to gravity. In the present study, in order to quantitatively clarify the effect of the two liquid supply mechanisms on the CHF enhancement, experiments to identify the elementary processes were conducted, and the CHF obtained in the experiments using the honeycomb porous plate was compared with a proposed capillary limit model. Based on the results, the following conclusions were obtained: (1) In the high heat flux region, the liquid supplied through capillary action was shown to be the dominant factor leading to the CHF enhancement in saturated pool boiling, and the results calculated using the proposed model were found to be in good agreement with the experimental results. (2) Liquid supplied through vapor escape channels had a strong effect on the heat transfer coefficient.