Analysis of heat storage performance of large medium-temperature thermocline water storage tank
The large medium-temperature thermocline water storage tank applies the principle of natural stratification of cold and hot water to achieve the purpose of storing hot water and cold water at the same time,and has a good application prospect in the field of mesothermal heat storage.In this paper,the medium-temperature stratosphere water storage tank(30 m high and 4 m diameter)designed in a compressed air energy storage project was taken as the research object.The effects of parameters such as heat storage duration,heat storage flow rate,heat storage temperature difference and fluid external heat exchange coefficient on the thickness of the thermocline,the key parameter of thermocline heat storage,were studied by using Fluent and self-programmed programs,respectively.The Fluent simulation results showed that:(1)Under the design operating conditions and without considering the external heat transfer of the fluid,the thickness of the thermocline gradually stabilized to 1.06 m after 1 000 s and climbed slowly,reaching 1.21 m at 4 000 s.(2)The effect of flow velocity on the thickness of the thermocline was the result of the combined effect of the initial mixing intensity of hot and cold fluids and the mixing time.(3)The temperature range of the thermocline was related to the value of hot and cold water temperature,and the thickness of the thermocline does not change much under different heat storage temperature differences.(4)In the equivalent heat transfer coefficient heq was 0,25,50 W/(m2·K),the thickness of the thermocline at 4 260 s was 1.21,1.33 and 1.39 m,respectively,and the higher the heat transfer coefficient,the greater the thickness of the thermocline.Based on the mechanism of heat conduction,heat convection and external heat transfer in the thermocline,the one-dimensional unsteady numerical method is used to realize the numerical calculation of the dynamic change of the thermocline in the heat storage process.The calculation results are similar to the Fluent simulation results,which has good engineering application accuracy.Through the research,it can provide technical support for the promotion of thermocline heat storage technology in large medium-temperature heat storage scenarios.
medium temperaturethermoclinewater storage tanksheat storageperformance
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