Systematic Research on Free Convection Heat Transfer in a Stably Stratified

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The following three issues have been investigated to conduct a systematic research on free convection heat transfer in a stably stratified fluid.1. Effects of the inner cylinder diameter on free convection heat transfer between coaxial cylindersThe stratified layer was formed using a sucrose aqueous solution, and was heated from the outer cylinder (70mm I.D.) at constant heat flux and cooled from the inner cylinder (15mm, 30mm or 50.8mm O.D.) at constant temperature. As a result, it is found that the early stage heat transfer is affected by the size of the inner cylinder, and the convection heat transfer shows similar characteristics of that between vertical plates, when the inner cylinder diameter becomes large. On the other hand, when the inner cylinder diameter being small, the average heat transfer coefficient approaches the steady state value with time but never exceeds it.2. Effects of a distance between heat transfer plates on free convection heat transfer between vertical platesThe stratified layer was formed using a sucrose aqueous solution, and was heated from one side wall at constant heat flux and cooled from the other side wall at constant temperature. The experiments were conducted for the distance between the heat transfer plates l=10mm, 40mm and 60mm, and the results were compared with those for l=20mm which are reported by the authors. As a result, it has been found that the average heat transfer coefficient becomes great, when the cellular layer thickness equals to the distance between the heat transfer plates.3. Numerical analysis on free convection heat transfer in a rectangular cellNumerical analysis has been performed on free convection heat transfer in a rectangular cell for wide rages of aspect ration 0.1-20 and Ra number 10^3-10^7, and correlation equations for the heat transfer coefficient have been developed to construct a theoretical model for analyzing the heat transfer in a stably stratified fluid.