Study On Phase Change Heat Transfer Characteristics Of Energy Storage Materials With Porous Framework

Under the background of energy crisis which fossil fuels as the traditional energy are confronted with non-renewable consumption,people began to consider new energy development and utilization,therefore,building energy conservation has become a widespread attention topic,phase change energy storage technology arises at the historic moment.By installing phase change energy storage material which as heat storage equipment indoor,or joining phase change heat storage material in the walls,doors,windows and the floor.It can reduce building indoor temperature fluctuation and improve the comfortableness by using the characteristics of the heat storage and release in the process of phase change to effectively.The application of solid-liquid phase change energy storage materials has been widely discussed,and the research on the characteristics of solid-liquid phase change process has become an important direction in the field of building energy conservation.This article studied the heat transfer mechanism in the combination of the experiment and numerical simulation which paraffin wax as the research object.Firstly testing the phase temperature of paraffin,phase change latent heat value,the coefficient of thermal conductivity and specific heat capacity by DSC and Hotdisk technology.The solid-liquid phase change experimental platform was built based on it.Experimental study on the melting process and properties of porous paraffin wax.The phase change process was observed by a CCD camera and focus on the formation and migration of the phase interface.In order to study the phase change process of paraffin wax under different heating power,the temperature distribution was measured by the micro thermocouple embedded in the porous framework.The experimental results demonstrate that the heat storage of paraffin is conducted in a temperature range.Isotherm is the most populous,and the temperaturegradient is large at the border and the solid-liquid interface in the process of heat storage.Temperature gradually decreases along the direction of heat flow,and eventually converges with the regenerative process.Temperature has the roughly same change trend along the height direction,and increases with the height increases,eventually levels with the reformative process.Phase change heat transfer process of heat storage material can accelerate by increasing the heat flow density and the response time is not proportional to it.The property of heat storage material affects the process of phase change heat transfer,and specific heat capacity influences its heating rate before liquefied,The smaller the specific heat capacity,the greater the heating rate.Phase change latent heat affect the heating rate in the melt phase,the greater the latent heat,the more smoothly temperature change.In order to verify with the experimental results and relevant conclusions of this experiment are not measured,such as the distribution of the velocity field and liquid fraction changes,further study on the mechanism of heat transfer with phase change materials.In this paper,a numerical simulation model is established,which is made of two kinds of metal aluminum and nylon to study the effect of porous framework with different physical properties on the heat transfer and flow in a heat storage material.The results show that the thermal conductivity of paraffin metal containing aluminum frame is better than others.The change of speed and temperature is the most uniform.The cavity with metal aluminum skeleton makes phase change materials in the direction of the temperature changes more ease,skeleton strengthen heat conduction,natural convection heat transfer.The streamline of phase change process is most thickset in the boundary of the cavity and the solid-liquid interface,due to the interactions of the temperature field and the velocity field changes the evolution and development of solid liquid interface.The solid-liquid interface of paraffin wax in the cavity which include nylon skeleton presented the ladder-like due to its low thermal conductivity,paraffin appeared as a single medium smooth curve,The interface of paraffin wax in the cavity which include metal skeleton near to a sloping straight line.The results of the simulation and the experiment are anastomotic by comparing.