Effectiveness of sintered porous surface for mist cooling heat transfer

Abstract

This study experimentally examined evaporation of the single droplet deposited on the heated surface where copper fine powders had been sintered. A sintered layer, which was made by Spark Plasma Sintering, ranges in porosity from 0.19 to 0.55, and in a thickness from 70 to 600 μm. Porous surfaces expanded the contact area of deposited droplet, and hence a contact angle was reduced as compared to non-porous surfaces. This area was also enlarged by an increase in pre-impact Weber number. A droplet being placed on the porous surface that had specific porosity, a wetted zone due to permeation instantly surrounded the droplet. Under a constant surface temperature, droplet lifetimes on the porous surfaces where the wetted zone did not appear shortened with increasing Weber number, since enlargement of the contact area and/or a droplet breakup occurs on the surface. For the surface where the zone largely formed, droplet lifetimes were almost independent of Weber number because of the larger evaporation interface that had grown by wicking. Mostly, the porous surfaces enhanced droplet evaporation in low temperature range. © 2012 The Japan Society of Mechanical Engineers.