TRANSIENT NATURAL-CONVECTION OF WATER NEAR ITS DENSITY EXTREMUM IN A RECTANGULAR CAVITY

An experimental and theoretical investigation of transient natural convective heat transfer to water near its maximum density in a rectangular cavity is reported. Different temperatures are imposed on the opposing vertical walls, and the effects of density inversion of water that has its maximum density at about 4-degrees-C are investigated. Initially, the fluid inside the test cell is at a uniform temperature, and then the temperature of one of the cold vertical walls is suddenly lowered and kept at 0-degrees-C. The hot wall is maintained at a constant temperature during the course of each experiment and is equal to the initial temperature of the water that varies from 8 to 20-degrees-C. Solutions of the governing equations are obtained numerically for all experiments discussed. Photographs of flow visualization and predictions of the flow patterns as well as a comparison of measured and calculated temperatures are presented. From the results obtained it is demonstrated that the density inversion of water has a great influence on the natural convection in the cavity, and the flow structure cannot be predicted using the classical natural convection models which employ the Boussinesq approximation.