Heat and Mass Transfer of Freezing of Melting Process of Soil Containing Sea Water

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Soil is one of useful materials as a heat source for a heat pump system and as a cold energy strage. For a case that thermal energy including the laten heat is stored in soil containing sea water, it is important to study a freezing or melting process of a porous medium saturated with a NaCl - aqueous solution. In the present report, considering ground water flow or the ebb and flow, effects of natural and forced convection on the freezing around a horizontal cylinder in a porous medium saturated with 3 wt% NaCl aqueous solution was investigated analytically and experimentally. In the experiments a packed bed of glass beads was used as the porous medium. In order to clarify an interaction of natural convection and forced convection, the solution was let to flow upwardor downwared across the cylinder through the porous medium with various flow rates. By cooling the cylinder below the eutectic temperature the freezing around the cylinder was initiated. In order to visualize the interactive flow around the frozen layr, and experiment of freeaing around a cylinder in Hele-Shaw flow was carried out. A numerical analysis, in which heat and mass diffusions and flow in both liquid and mushy regions were taken into account, was carried out. The temperature distributions obtained from the analysis agreed well with the experimental results. Effects of the natural and forced convection on the freezing process --- the temperature distribution, the stream function contour, the shape of frozen region, the volume fraction of liquid phase in the mushy region, and the volume fraction of eutectic solid in the solid region --- were clarified. Effects of Peclet number and the flow direction on Nusselt number and a dimensionless volume of the solid phase were clarified.