Thermal Analysis Of A Phase Change Thermal Storage Device With Erythritol

A new heat storage unit which consists of cylindrical U tube is proposed in this paper,and numerical simulations are carried out to study the thermal performance of the heat storage unit in the process of charging and discharging as well.The heat storage unit proposed uses erythritol whose phase change temperature is 120 degrees Celsius,while water is the heat transfer fluid.The complete charging process of the heat storage unit in horizontal positon is simulated first in this paper.In the meantime,several parameters of the charging process are analyzed,which are the laying position of the heat storage unit,the heat conductive enhancement due to the addition of nano-carbon particles in the heat storage material,the heat transfer enhancement owing to integration of fins,the different fluid inlet velocities and different fluid charging temperature,respectively.According to the simulation results,in the charging process of the heat storage unit in horizontal position,the phase change material in the upper part melts down first with the effects of the natural convection,while the phase change material in the bottom melts down last.Based on the data,it is worth noting that the time that the heat storage unit in vertical position spends in a complete charging process is 1.4 times as long as the heat storage unit in horizontal position does.As for the addition of nano-carbon particles,there is no significant increase in the charging rate until the volume ratio is bigger than 1%.When the volume ratio of nano-carbon particles is raised to 2%,the complete melting time of the phase change material with nano-carbon particles decreases by 23%compared to that of the phase change material without nano-carbon particles.When the inlet temperature of the fluid is increased from 413K to 433K,the complete melting time decreases by 48%accordingly.However,the flow rate of the charging fluid has little effect on the complete melting time.For the following research,the simulation about the complete discharging process with the heat storage unit placed horizontally is studied.Meanwhile,several parameters of the discharging process are analyzed,which are the laying position of the heat storage unit,the heat conductive enhancement due to the addition of nano-carbon particles in the heat storage material and the heat transfer enhancement owing to integration of fins respectively.Based on the simulation statistics,in the discharging process,when the heat storage unit is placed horizontally,the global melting rate of the phase change material in the lower part is faster than that of the phase change material in the upper part.Moreover,the addition of the nano-carbon particles contributes to the significant increase of the discharging rate.When the volume ration of the nano-carbon particles is 2%,the complete discharging time of the phase change material with nano-carbon particles decreases by 50%compared to that of the phase change material without nano-carbon particles.Similarly,the integration of some fins can accelerate the discharging process,for example,when the heat storage unit is integrated with eight fins,the discharging time decreases by 40%compared to that of the heat storage unit without any fins.