On capillary-driven flow and phase-change heat transfer in a porous structure heated by a finned surface: measurements and modeling

Characteristics of capillary-driven flow and phase-change heat transfer in a porous structure heated with a permeable heating source at the top were s tudied experimentally and theoretically in this paper. The experiments show that for small and moderate heat fluxes, the whole porous structure was fu lly saturated with liquid except adjacent to the horizontal heated surface where evaporation took place uniformly. For higher heat fluxes, a two-phase zone developed in the upper portion of the porous structure while the lowe r portion of the porous structure was saturated with subcooled liquid. When the imposed heat flux was further increased, a vapor blanket formed below the heated surface and the corresponding critical heat flux was reached. Th e heat transfer coefficient was modeled by simultaneously solving the probl em of evaporating capillary meniscus in the pore level and the problem of f luid flow through a porous medium. The model is in good agreement with the experimental data, predicting the variations of the heat transfer coefficie nt with the increasing heating load. (C) 1999 Elsevier Science Ltd. All rig hts reserved.