| With the promotion of energy-saving work in heating buildings in the northern regions,the air tightness of buildings has been significantly improved,but the shortage of fresh air in winter has also followed.When designing a fresh air supply system,it is possible to consider the use of electric heating and energy storage solar system mutual assistance means to achieve energy saving and improve indoor air quality.Energy storage device is an important node of this integrated system,and phase change energy storage has better theoretical heat storage capacity than sensible heat storage.So,it is of great significance to study the heat transfer characteristics of air phase change energy storage device and its application in building fresh air system for guaranteeing indoor air quality and reducing building energy consumption.In this paper,a dual-channel air phase change energy storage device is designed,which can preheat the lower temperature fresh air in the fresh air system.The heat storage side and the heat release side of the device can operate independently,and it has the characteristics of simple operation and relatively flexible heat release time.Based on the analysis of phase change material characteristics and equipment requirements,the eutectic with 66%decanoic acid and 34%lauric acid was selected as phase change material,and its physical properties were tested by DSC testing equipment.Through reasonable analysis and conditional assumptions,a simplified mathematical model of the phase change energy storage device is established,and the mathematical expression of the heat transfer process is given.The discrete equation of the simplified heat transfer equation is obtained by calculus,and the internal temperature field of the phase change energy storage module is solved by MATLAB software.The results show that under the working conditions of the phase change energy storage device,the phase change material in the heat storage unit with thickness of 40mm can be fully melted during the heat storage stage.This method can provide a theoretical basis for setting the thickness of the heat storage unit in the design of such phase change energy storage devices.The heat transfer process and heat transfer influencing factors of the dual-channel air phase change energy storage device were simulated by FLUENT software.The results show that during the heat storage process,the temperature and flow rate of hot air have a significant influence on the melting rate of the phase change material within a certain range.During the exothermic process,the lower the fresh air temperature,the greater the heat release of the phase change energy storage device,and the higher the heat release efficiency.During the synchronous convection heat transfer simulation process,the phase change material also releases heat while accumulating heat,so that the liquid phase rate and the average temperature increase rate of the phase change material are relatively low.An experimental platform of dual-channel air phase change energy storage device was built,and its heat storage,heat release and synchronous convection heat transfer process were tested and analyzed.The results show that during the heat storage test,the temperature trends of the four monitoring points are similar,but the phase change materials near the top of the baffle are more difficult to melt.During the exothermic test,the outlet temperature of fresh air after heat transfer by phase change energy storage device is between 4.2?12.5?,and the exothermic heat of 18000s is about 884.5kJ.During the synchronous convection heat transfer test,the fresh air outlet temperature was relatively stable,and the average outlet temperature was 5.6?.The effect of preheating fresh air is obvious.By comparing the experimental values with the simulated values,it is found that the deviation between the two values is small.It can be concluded that the parameter setting and the condition assumption are reasonable in the simulation process.Based on the simulation and experimental results,the structure of phase change energy storage device was optimized.The results show that the optimization scheme of changing the right-angle bend of phase change heat storage unit into arc bend and reducing the number of baffles has more obvious effect on the actual optimization of this type of phase change energy storage device. |
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