Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : June 14, 2017 - June 15, 2017
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 demonstrated that pool boiling CHF using a honeycomb porous plate (HPP) was enhanced by more than twice (2.5 MW/m2) 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. On the other hand, there is no significant CHF enhancement when the thickness of the HPP is about the same thickness as macrolayer formed under coalesced bubble. As a result of the dry out is occurred inside the porous medium during the hovering period of coalesced bubble, hence CHF is reached. In addition, the effects of the formation of coalesced bubble on CHF is far greater in the case of the downward-facing heated surfaces than the upward-facing heated surfaces. In this study, we report the effect of the heater surface orientation using two layers structured HPP on CHF enhancement in a saturated pool boiling. First layer, an alumina HPP is installed just on the heated surface, has very fine pores to supply water toward the heated surface by strong capillary force. Second layer, A metal HPP is placed just on the alumina HPP stated above, is structured to hold a sufficient amount of water in order to prevent the drying out completely inside the metal HPP during hovering period of a coalescent bubble.
