Study On Heat Transfer Characteristics Of Aluminum-Ammonia Axially Grooved Heat Pipe

Heat pipe is an important part of aerospace efficient cooling system.It mainly uses liquid evaporation and condensation cycle to complete the heat transfer at both cold and hot ends.Its effective heat transfer performance is significantly affected by the liquid filling rate,the geometry of condensation and evaporation section and the external gravity environment.In this paper,we study the "Ω" groove heat pipe,shows more excellent performance and reliability than traditional heat pipe,but the technology basic monopoly and a few countries of Europe and America.There are few researches on its heat transfer mechan ism in China,especially on the gas-liquid distribution and flow change in heat pipes under different gravity conditions.According to the actual experimental conditions,the physical model of aluminium-ammonia channel heat pipe is established.VOF(Volume of Fluid))model and Lee model were used to establish the numerical model of phase change flow and heat transfer of aluminum ammonia heat pipe,and the accuracy of the model was verified by comparing with experimental data.To explore the heat transfer characteristics of heat pipes under different liquid filling rate,structure parameters,thermal load and varying gravity conditions.Firstly,numerical simulation was carried out for the heat pipe under different gravity fields.The distribution,flow and heat transfer characteristics of liquid and gas working medium in the heat pipe under the power of 35 w heat source were studied.The results showed that when G=1g,the liquid and gas of the heat pipe were layered up and down.Nuclear boiling in the evaporation section during operation.The heat pipe circulation mainly depended on the reflux of the bottom working medium.When G=0g,the liquid in the heat pipe is mainly concentrated in the channel and small round hole.But some of the working mass will go into the steam chamber as it evaporates.The liquid phase distribution in the evaporation stage is not continuous.Then,on the basis of 30% liquid filling rate,the influence of 10% change of liquid filling rate on heat pipe performance was analyzed.The relati onship curve of influence of change of working quality on heat transfer performance was given.The results showed that the heat pipe had the best heat transfer performance under the basis liquid filling rate.When G=1g.The thermal resistance decreases with the increase of the power of the heat source.when G=0g,the thermal resistance changes in the opposite way.Finally,the influence of geometric structure parameters on heat transfer performance is studied.The length ratio,narrow slit width,channel diam eter and steam chamber diameter of the heat pipe were changed respectively.The performance curves of various structural parameters are given.The optimal geometry of the heat pipe with or without gravity is calculated.The calculation results show that the heat pipe structure on the law of the unity of the influence of thermal performance and no,mainly because of the part of the structural parameters of existence conditions restrict each other.At the same time,with or without gravity affect the performance of heat pipe under the condition of the trend.It provides technical support and theoretical guidance for the stable operation and performance optimization design of aluminum ammonia heat pipe.