Operating Characteristics Of Solar Energy Combination System With Phase Change Heat Storage Tank

In order to improve the efficiency of solar thermal utilization,a new type of phase change heat storage tank is developed and applied to the solar energy combination system.Through experimental research,the effects of the new phase change thermal storage tank on the performance and economics of the solar energy combined system are analyzed.It provides a new idea for the design and application of solar energy combined system.Aiming at improving the vertical temperature stratification inside the water tank,a new type of phase change heat storage tank is developed.Two phase change paraffin waxes with different phase change temperatures are filled according to the thermal temperature range at the end.45?phase change paraffin is placed on the upper layer,and30?phase change paraffin is placed on the lower layer.The phase change material is sealed by stainless steel 304.The shape of the packaging container adopts flat core structure.At the same time,in order to ensure the water supply flow rate of domestic hot water loop and reduce the flow resistance,the design of uniform distribution of four holes is adopted to make the heat transfer more uniform,meanwhile,increase the heat transfer area of phase change material and increase the heat transfer.This paper focuses on the operation characteristics of solar energy combination system under different conditions,such as cloudy,sunny and coupled phase change storage tank.The results show that the solar energy irradiation is low under rainy weather conditions,and the solar energy heating system can not achieve the solar energy heating effect,the system completely depends on the auxiliary heat source to operate stably.The average energy efficiency ratio of the intermittent operation mode of this experimental bench under rainy weather conditions is 0.88,the average energy efficiency ratio of continuous operation mode is 0.87,the intermittent mode is better than the continuous mode.Under sunny conditions,comparing the solar energy guarantee rate with the system energy efficiency ratio when the heat collecting area is 10.44m~2and 20.88m~2,the solar energy guarantee rate changes in direct proportion to the system energy efficiency ratio,and increasing the heat collecting area is conducive to improving the solar energy guarantee rate and the system Energy efficiency ratio.In the solar energy combination system,under the same circumstances,the hourly heat recovery of the heat recovery system when using the phase change heat storage tank is much higher than that of the ordinary heat storage tank,and the average hourly heat recovery of the heat recovery system when using the phase change heat storage tank is 3.7times that of the ordinary heat storage tank.The addition of phase change material can increase the heat storage capacity of the same volume heat storage tank,reduce the high temperature water temperature drop at the top of the night heat storage tank,and increase the temperature difference inside the tank at the same time.During the same test period,the average night temperature drop of high temperature water in the upper part of ordinary heat storage tank was 0.44?per hour,and the average night temperature drop of high temperature water in the upper part of phase change heat storage tank was 0.22?per hour,the temperature drop decreased by 50%.Therefore,the phase change heat storage tank is beneficial to improve the solar energy guarantee rate and system energy efficiency ratio.In the case of similar solar irradiation intensity,the phase change hot water storage phase will increase the solar energy guarantee rate by an average of 72%,and increase the average System Energy Efficiency Ratio(EER)by 26%.Finally,TRNSYS transient simulation software was used to build a solar energy combination system simulation platform,and the effect of phase change on the solar energy combination system was compared.The results show that the dynamic recovery period of the solar energy combination system of this experimental platform is 8 years,and the system after adding the phase change material the dynamic recovery period is 9 years.At the same time,the environmental protection benefits of using a phase change hot water storage tank are superior to ordinary systems.In general,it is advantageous to use a phase change hot water storage tank with solar combined system.