Performance Investigation And Optimization Of Energy Storage Thermal Management System Base On Heat Pipe

Along with the continuous development of social economy,the conflict between energy supply and demand is becoming more and more prominent,and the basic national situation of energy resources in China is still in the situation of "poor oil,little gas and relatively rich coal",energy saving has become a key to balance economic growth and sustainable social development.At present,the government is vigorously developing energy saving measures,and thermal energy,as a renewable energy source,plays a very important role in energy technology in terms of transmission and conversion,so there are still unprecedented opportunities and challenges in thermal energy storage.In response to the problem of low energy recovery rate due to the mismatch between energy storage materials and heat exchange methods in medium and low temperature thermal applications and conventional phase change thermal storage systems,we propose a coupled heat pipe energy storage device design(HP-ESTM)with heat pipe technology characteristics(homogeneity,cold and heat source separation,arbitrary exchange heat flow density,etc.)and phase change thermal storage technology to strengthen the energy storage device design.The HP-ESTMS unit is used to explore the melting and solidification characteristics of the phase change material and the thermal management performance of the system under different operating conditions.The thermal management system is characterized by simple and modular structure,good stability and high reliability,and is a thermal management device that also dissipates energy storage,which is an excellent solution to meet the energy saving challenges.The heat pipe based energy storage thermal management system(HP-ESTMS)adopts sintered copper water pipe as heat transfer element,modified paraffin as phase change energy storage material to form energy storage unit,and sheet cooling module for auxiliary cooling and heat dissipation to form an integrated heat management system of heat dissipation and energy storage.In this work,we constructed an experimental platform to study the performance of the thermal management system by placing an electric heating block at the evaporative end of the heat pipe to simulate the heat source heating.Experiments were conducted under different operating conditions including(heat flow density input,cold load size and device placement in horizontal,tilted 45°,vertical,etc.)considering the influence of relevant conditions on the performance of each part of the system.The experimental test results are combined with the analysis of the working performance of the heat pipe and the melting and solidification of the PCM in the energy storage unit and the temperature variation of the heat source,in order to evaluate the thermal management performance of the energy storage system.The test results show that :(1)for the performance of heat pipe,the overall temperature and thermal resistance of heat pipe decrease with the addition of energy storage device,and its thermal conductivity is better.When placed vertically for comparison,the thermal resistance of the heat pipe decreased by 35.5% to 44.5%,and there was a minimum value of 0.05391℃/W at80 W.At the same time,the comparison of thermal resistance trend charts under different places found that there was a minimum thermal resistance range at 80 W input power.In addition,the maximum temperature of the evaporation end can be maintained near 90℃ for a long time.This is a result of the energy storage device to join in the adiabatic section is equivalent to join a cold end heat pipe,plays a thermal buffer effect,make the heat pipe are warm,etc,to guarantee the heat pipe does not dry up because temperature rises early to appear the limit,can make the heat transfer performance of heat pipe is always keep a good state,effectively improve the stability and reliability of the system;(2)The existence of the energy storage device can effectively reduce the evaporation temperature,while the cold load increase,lead to the cooling effect is stronger,but the PCM as to the cold end evaporation absorbs some heat,compared with the single water,can be in whole temperature to maintain higher and more stable range,for some special equipment to run may be more effective,to achieve more economic effect of thermal management;(3)By comparing the melting characteristics of the PCM and the thermal resistance of the internal heat pipe in different placement directions of the thermal management system,it is found that when the system is placed horizontally,the thermal resistance of the heat pipe in the system is the smallest,and at the beginning,part of the PCM in the horizontal placement melts faster and the internal temperature is higher,but due to the influence of various factors(1.When placed horizontally,heat is preferentially transferred from the radial heat pipe to the first cold end,and affected by the thermal conductivity of PCM and gravity,its axial heat transfer is poor,so there is a dead zone in the lower part of the energy storage unit,and PCM cannot completely melt.2.When placed vertically,the heat source is below,and the heat transfer between PCM will form strong natural convection)causes the complete melting faster in the vertical placement,so it is better to choose the vertical placement.After rough calculation,the energy stored in the energy storage unit is 60 KJ and the energy storage efficiency is 6.9%when placed vertically for natural heat dissipation.At the same time when the ambient temperature is 20℃,the system is tested in terms of thermal insulation management and energy saving,and the experimental results show that the system’s energy-saving thermal management effect is feasible and effective.When the overall temperature of the system needs to be controlled above 25℃,the PCM in the energy storage unit acts as the heat source for heat dissipation by the heat pipe,and the whole system can be insulated for 300 minutes regardless of any placement.