The Numerical Simulation And Experimental Study Of Latent Heat Storage Problem Around Tube And Inside Sphere

The latent heat storage problems of shell-and-tube latent heat storage device and packaging phase change material inside a sphere are the research focus of the latent heat storage technology. But in recent years, the phase change heat transfer problem around a horizontal tube considering the convection is rarely reported, and the performance and efficiency study of latent heat storage system is less in other papers, and the law of phase change heat transfer process inside a sphere is not enough to thoroughly grasp. Therefore, the issues of latent heat storage around tube and inside sphere have been studied numerically and experimentally in this dissertation.The mathematical model for phase change heat transfer around a horizontal tube in a rectangular groove, which is validated by experimental data, and its boundary conditions have been developed. The changes of temperature field around the tube and solid-liquid interface with time, as well as the effect of wall temperature are presented. In order to obtain universal results, dimensionless analyses on the effects of wall temperature and initial temperature of phase change material on the melting and solidification processes are carried out. The results show the effect of wall temperature is gradually decreased with its increasing on the melting process, and is decreased with its decreasing on the solidification process.The thermal behaviors of the latent thermal energy storage unit with paraffin as the phase change material and air or water as the heat transfer fluid are studied. The effects of working conditions, geometric parameters, material properties on the operation and efficiency of the latent heat storage system with water as heat transfer fluid are studied. The results show obviously different behaviors of the shell-and-tube latent heat storage unit when air and water are as the heat transfer fluid. Increasing the thermal capacity of phase change material is the most effective method to improve the overall performance of the shell-and-tube latent heat storage system.An experimental study is performed. The phase change process of paraffin inside a sphere capsule and the effect of bath temperature and paraffin initial temperature on the melting and solidification processes are analyzed. The influence of aluminum is compared with the pure paraffin by adding different amounts of aluminum powder to the sphere capsule. The effects of various factors on the paraffin melting rate inside the sphere capsule are studied using numerical method. The results indicate that the melting time of the sphere capsule decrease 50% and 23%, respectively, when the bath temperature increases from 55℃to 60℃and the initial temperature of paraffin increases from 15℃to 30℃. A weak influence of the initial temperature of paraffin on the solidification process can be expected. By adding 1% and 2% quality amounts of aluminum powder, the melting time is shortened 22% and 34%, and the solidification time is shortened 36%. Adding aluminum is an effective measure to improve the performance of phase change material inside a sphere capsule.Finally, this dissertation designs a cluster-type fin-tube latent heat storage unit. The effect of different flow rates of heat transfer fluid on the behaviors of heat storage and releasing is studied experimentally. The cluster-type fin-tube latent heat storage unit is applied to a demonstration project in Tianjin, and the problem of volatile temperature in water tank is found to be relieved.