Experimental and theoretical pore-scale study of thermal field responses to drying of porous surfaces

Tuesday, 15 December 2015
Poster Hall (Moscone South)
Milad Aminzadeh, ETH Zürich, Zurich, Switzerland and Dani Or, ETH Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
The drying of porous surfaces involves pores invasion at a sequence reflecting their respective capillary size (large pores invaded first similar to drainage). The emptying of an evaporating pore is accompanied by changes in the thermal field forming on the surface around the invaded pore that consequently affects surface temperature and energy partitioning over the drying surface. A novel experimental system was designed to systematically evaluate the coupling between surface temperature and evaporative flux from individual and clusters of pores drilled into rough glass surfaces connected to a liquid reservoir. Details of thermal fields around individual evaporating pores were observed for sparse and dense pore spacings including measurements of evaporating flux dynamics and results were compared with PCEB model [Aminzadeh and Or, 2014] predictions. We observed drying-induced pore emptying sequences of sintered glass bead surfaces by visual and thermal imaging using high resolution infrared imager. The links between pore emptying sequence at a drying surface inferred from pore size distribution, and surface temperature dynamics offer a possibility of predicting energy partitioning over drying terrestrial surfaces.