NATURAL CONVECTION IN A RECTANGULAR CAVITY FILLED WITH WATER

Abstract

Thermal management is one of the most important aspect in industries, which has heat transfer processes, whether the addition or rejection of heat. The enhancement of heating or cooling capacity in an industrial process leads to energy conservation, reduction in process time and the improvement of the life period of the equipment. To transfer the heat in a process, water plays a central role as a carrier fluid from the beginning of the Industrial era.Forced convection has been proved an efficient heat transfer phenomena, but cannot be used for any specific processes such as cooling of electronic devices (chips, transistors), thermosiphon system (solar water heating system), food industries, and so on. where only natural convection can be applied. Due to the absence of any mechanical part, natural convection mainly depends upon the density gradient. Other parameters such as geometry and the inclination angle of the enclosure, heating surface (sides, top or bottom) and aspect ratio also affectsthe natural convection. The objective of this study to investigate the optimal value of the aspect ratio to onset the natural convection and establish a range of the Rayleigh number for the natural convection is influenced by the various aspect ratios AR (=L/Dwherebis the characteristics depth andDis the width of cavity) in the range of 0.25 AR < 2.To do so, an experimental study has been done for natural convection of a heat source embedded in the bottom wall of an enclosure filled with water, top wall is maintained at low temperature and the remaining walls of the enclosure are insulated. Experimental setup is divided into three sections. First, heating section in which a plate heater is planted in the bottom copper plate, which is utilized as a heating surface. Second, cooling section which is consist copper plate as a cooling surface cooled by the constant temperature bath. The third segment is the test section filled with the water where natural convection will be taking place. The temperature of both heating and cooling surfaces and water in the test section is measured by the T-type thermocouples and values are stored by a data acquisition system. Experiments are conducted for the different values of aspect ratios and constant heat flux conditions. Results are portrayed in the dependence of the Rayleigh number on the aspect ratio for different heat flux conditions. The effect of aspect ratio is also examined the heat transfer of water.