Research On Heat Transfer Characteristics And Optimization Of Phase Change Heat Storage Device

The phase change heat storage device can effectively improve the utilization of energy because of its large heat storage density and high thermal storage efficiency.However,it is an important problem to evaluate the performance of the phase change heat storage device because of the uncertainty of the parameters of the phase change heat storage device and the complexity of the application environment.It is different from the traditional heat transfer research of phase change heat storage device.In this paper,the idea of uncertain heat transfer is introduced to study the heat transfer of the phase change heat storage device,and the analysis method of phase change heat transfer is expected to be given in the uncertain heat transfer analysis.In this paper,the heat transfer characteristics and optimization Research of phase change thermal storage device include the following aspects.(1)In this paper,a solar energy direct heating phase change thermal storage device is taken as an example,and its experimental research method and computational heat transfer analysis method are given.(2)Based on the uncertainty heat transfer analysis method,the influence of different factors on the heat transfer characteristics of phase change heat storage device is analyzed.The uncertainty of thermal conductivity,phase change temperature,convection heat transfer coefficient,heat transfer fluid flow and the spacing of fluid tube on the temperature and heat storage of the heat storage and release process are systematically calculated and analyzed in different range of deviation.(3)Numerical simulation is used to optimize the thermal conductivity,convection heat transfer coefficient,heat transfer fluid flow and heat transfer fluid tube spacing.Through the study,we can get the following conclusions:(1)the study on the research method of heat transfer characteristics shows that by comparing the experimental results with the simulation results under the same working conditions,it can be seen that the temperature change trend is approximately the same and the maximum deviation rate is within 10%,so the accuracy of the mathematical model can be explained.(2)The study of the range of parameter deviation shows that:At the relative deviation of ±20%,The absolute deviation of process temperature increases with the increase of thermal conductivity.The process temperature decreases with the increase of convective heat transfer coefficient and heat transfer fluid flow.There is no linear relationship between phase change temperature and tube spacing on absolute deviation of process temperature.Under the circumstances of different relative deviations:As the absolute value of deviation increases,the absolute deviation of process temperature increases for thermal conductivity,tube spacing,convective heat transfer coefficient and flow rate.There is no uniform linear relationship between absolute deviation of process temperature and absolute deviation of phase change temperature.When different thermal conductivity,different convective heat transfer coefficients and different flow deviations are in the range of-30%?+30%,The heat of storage or release increases with the increase of deviation.When the deviation of different tube spacing is within the range of-30%-+30%,The discharge of heat decreases with the increase of the deviation degree.There is no uniform linear relationship between heat storage capacity and deviation degree.(3)The optimization study shows that:Under the condition that other experimental conditions are not changed,the optimum value of the comprehensive thermal conductivity of the phase change material in the device is 8W/(m·K),the optimal value of the flow rate is 0.0008kg/s,and the optimal value of the convection heat transfer coefficient is 600W/(m2·K).With the increase of tube spacing,the effective utilization time of the device is also increasing.The effective utilization time of the device is almost no longer changed when the filling thickness of the intertube phase change material is up to 0.1 m.With the increase of tube spacing,the storage and heat release efficiency of the device decreases.