Study Of Contack Melting Of The Phase Change Materials Inside Inclination Rectangular Capsule

Phase change materials(PCMs),especially organic phase change material as a storage material exist major disadvantage is low thermal conductivity.In response to the shortcomings of low thermal conductivity,a lot of improvements,such as embedding a metal model,adding high conductivity particles,and increasing the surface area,to be used to solve the problem.In the phase change melting process the main way to release the heat by contact melting.With gravity the heat surface and the solid phase change material contact together,a liquid film form between the solid phase change material and heat surface,then high heating rate is obtained in a closed container filled with phase change material.On this basis,faster melting rate can be obtained through tilting the rectangular cavity.Plexiglass is used for container and the melting process can be recorded by camera.The liquid fraction and solid-liquid interface would be obtained through post-image processing.The relationship between the inclined angle and the total melt time can be found through the visualization experiment and the image is processed by digital processing technology.The critical angle which leads the highest effectiveness storage unit can be found.The mathematics solution of the phase change material melt process is nonlinear mathematical model which means a few analytical solutions can be gotten;most of the finite volume approximation problem would be solved by the approximate analytical solution and numerical simulation.Non-inclined rectangular cavity approximate analytical solution is adapted to match the experimental date and the result is in a good agreement,which prove the digital processing technology is feasibility.Inclined rectangular cavity model is developed in this paper,and the approximate analytical solution is obtained.The experiment date has a good agreement with the model that proved the contact melt is the main heat transfer.The phase change materials melt process can be divided five stages through the numerical model.In the first stage the solid PCMs begin to melt.In the second stage the bottom liquid film steadily forms.With the liquid PCMs increase the liquid film between the right heat surface and the solid PCMs steadily forms in the third stage.In the fourth stage the solid PCMs sink under the action of gravity.In the fifth stage is about the inclined angle between the 45 degree and 60 degree which is affected by the convection heat transfer obviously.By comparing the solutions with the approximate analysis,the contact melt are main heat transfer in the initial stage and the convection heat transfer become not be ignored in the latter.