Inner cylinder diameter effects on free convection heat transfer in a stable stratified fluid

Abstract

An experimental study was performed to identify the effects of the inner cylinder diameter on free convection heat transfer in a stable stratified fluid between coaxial cylinders. The stratified layer was formed using a sucrose aqueous solution, and was heated from the outer cylinder (70 mm I.D.) at a constant heat flux and cooled from the inner cylinder at a constant temperature. The experiment was conducted for an inner cylinder of 50.8 mm O.D. and the results were compared with those for an inner cylinder of 30 mm O.D., which were previously reported by the authors. The results show that the inner cylinder size affects the heat transfer in the early stage of heating: increasing the diameter of the inner cylinder decreased the distance between the heating and cooling surfaces. It consequently reduced both the duration of heat conduction prevailing and the resulting temperature increase of the heating surface during that period. Increasing the diameter of the inner cylinder also made the heat transfer characteristics similar to those between vertical plates.