Numerical Analysis On The Heat Transfer And Flow Performance Of Pin Fin Heat Exchanger

Heat exchanger is the key equipment of the solar energy power plant,which has become a research focus.In order to improve the dynamic characteristic of the heat exchanger,to enhance heat transfer capacity per unit of volume,to increase the single unit power,service life and reliability,a new and more advanced heat exchanger structure need to be seek.Volumetric absorber,as a new idea of solar power heat exchanger,is suggested.Using the solar energy volumetric absorber based on pin fin arrays as the research object,we built the mathematical-physical model of its internal flow and heat transfer.The standardκ-εturbulence model is used to describe the turbulent fluid flow,standard wall function is adopted the flow near wall.The heat transfer induced by radiation is dealt with discrete ordinate(DO) radiation model.The radiation heat transfer is considered to be the inner heal source of the energy equation.The results of numerical simulation show flow field distribution, temperature distribution and pressure distribution in different pins height,different streamwise spacing of pins and different Re numbers.The effect of Re number,streamwise spacing of pins and pins height on flow field distribution,temperature distribution and pressure distribution are studied.The result show that,as the Re number increasing,the average outlet temperature decreases,the local heat transfer coefficient of inlet,outlet and pin fins increase,the total heat transfer coefficient increases clearly.At Re = 10~4,the average outlet velocity increases with the streamwise spacing increasing.At Sx/D = 3.0,the total pressure loss is minimum,while maximum at Sx/D = 1.5.The total heat transfer coefficient decreases with the streamwise spacing increasing.And the same,at Re = 10~4,with the pin height increasing,the average outlet velocity decreases,the drag coefficient Cp are respectively:4.54,6.823,8.45. and then the total pressure loss is gradually increases.The total heat has a clear increase,and the total average heat transfer coefficient also increases greatly with the pin height increasing.The effect of radiation on flow field are studied and discussed at Re number of 10~3,10~4 and 10~5.The effect of radiation on velocity distribution is little.In the same Re number,the average drag coefficient with radiation existence is less than that without radiation.The local heat transfer coefficient with radiation existence is greater than that without radiation,and this gap increases as the Re number decreases.The ratio of the radiation heat-transfer rate to total heat-transfer rate decreases with the increase of Re number.The ratio is 44.71%at Re= 10~3,while 28.78%at Re = 10~4,8.45%at Re = 10~5.It is suggested that the radiation heat-transfer plays a significant role in the total heat-transfer when the Re number is smaller.