Effects of the Inner Cylinder Diameter on Free Convection Heat Transfer in a Stably Stratified Fluid between Coaxial Cylinders (The Case of the Inner Cylinder Diameter Being Large)

An experimental study is performed on the effects of the inner cylinder diameter on free convection heat transfer in a stable stratified fluid between coaxial cylinders. The stratified layer is formed using a sucrose aqueous solution. and is heated from the outer cylinder (70mm I.D.) at constant heat flux and cooled from the inner cylinder at constant temperature. The experiment is conducted for the inner cylinder of 50.8mm O.D. and the results are compared with those for the inner cylinder of 30mm O.D., which are reported previously by the authors. As a result it is found that the size of the inner cylinder affects the heat transfer in the early stage of heating : the increasing diameter of the inner cylinder leads to a decrease of the distance between the heating and cooling surfaces and thereby reduces both the duration of heat conduction prevailing and the resulting temperature increase of the heating surface in the period. The increasing diameter of the inner cylinder also makes the characteristics of the heat transfer similar to those between vertical plates.