Free Convection Heat Transfer Characteristics in a Melt Water Layer

Abstract

An experimental study was conducted on the formation of a water layer containing a maximum density, its effect on the onset of convection, and the heat transfer characteristics of such a system. This water layer was formed by one-dimensional melting (either from below or above) of a cylinder of bubble-free ice. For melting from above, with a melting rate measurement, the warm plate temperature Th varied from 4.16 to 13.09°C with initial ice temperatures T0 of −6.5 and −13°C, respectively. For experiments with a measurement of temperature profile, Th varied from 11.75 to 39.90°C with T0 at −12 and −15°C. For melting from below with a melting rate measurement, Th ranged from 7.70 to 25.50°C with four T0’s from −4.8 to −22°C. The layer depth at the onset of convection was determined by locating the inflection point on the water layer depth versus time curve, and was compared with layer depth calculated from a linear stability analysis of an identical problem. The results were compared with the analytical work of Veronis and were found to be in excellent agreement. Formation of a constant temperature layer was observed by measuring the water temperature distribution as melting progressed. The constant temperature was found to be dependent on Th for melting from below but was a constant for melting from above. The heat flux to the melting surface increased linearly with Th for melting from below, but had a weaker dependence for melting from above. Non-dimensional mean temperature profiles of the water layer were found to be in good agreement with those by Adrian for melting from above. In the case of melting from below, the mean temperature profile also fell into a single line with a somewhat higher value in the convection layer.