Optimization Research On Heat Transfer Performance Of Heat Pipe Heat Exchanger Based On CFD

With the rapid development of China's economy,energy use has increased year by year.The Energy Consumption and Production Revolution Strategy(2016-2030)sets targets for China's total energy use in the coming period.In order to solve the contradiction between economic development and control of energy consumption,we are required to improve energy efficiency based on existing energy consumption.The waste heat recovery potential of industrial waste is huge,and the residual heat of flue gas accounts for 50%of industrial waste heat resources.The efficient recovery of flue gas waste heat has obvious effect on improving energy utilization.Compared with the recovery of waste heat from medium and high temperature flue gas,the residual heat of medium and low temperature flue gas is easily ignored due to the limitation of concept and traditional waste heat recovery equipment.However,the heat pipe heat exchanger has the characteristics of high heat transfer coefficient,no external power,high reliability,flexible arrangement,etc.It is suitable for the occasion of low-temperature flue gas recovery and utilization,and has been paid more and more attention in the field of low-temperature flue gas waste heat recovery.Design parameters of the heat pipe heat exchanger and the heat pipe structure are optimized,to improve the heat transfer performance of the heat pipe heat exchangerOptimization of design parameters:Under the premise of safe operation of the heat exchanger,reduce the exhaust temperature of the hot fluid,increase the temperature difference between the inlet and outlet of the hot fluid,and make full use of the heat in the hot fluid.The method of determining the design value of the hot fluid outlet temperature by using the calculated value of the P.A.?epoe?? formula is changed,and the temperature of the heat pipe wall is not lower than the dew point temperature of the flue gas as the determination condition,and the temperature at the outlet of the hot fluid is reversed.It is assumed that the hot fluid side flue gas flow is 5000 m3/h and the temperature is 240?,The cold fluid side air flow rate is 4700 m3/h,and the temperature is 20?.The mathematical model of temperature change during the flow of hot fluid is established.The temperature of the heat pipe wall is simulated by the software of CFD fluid mechanics.The research results show that when the temperature of the hot fluid is 90?,condensation does not occur on the wall surface of the heat pipe,and 90?can be used as the design value of the flue gas outlet.Compared with the original design,the heat recovery is increased 25%-40%.Optimization of heat pipe structure:The fins of the heat pipe condensation section have a certain inclination angle,increase the fluid flow around the heat pipe near the wall surface,interrupt the continuous development of the boundary layer,and achieve the purpose of enhancing heat transfer.The structural optimization of the heat pipe was simulated by CFD fluid dynamics software.After the structure is optimized,the outlet temperature of the cold fluid and the heat pipe resistance increase with the increase of the fin inclination angle.The comprehensive performance evaluation index of the heat exchanger was introduced to calculate the comprehensive performance evaluation index values under different fin inclination angles.It is calculated that when the inclination angle of the heat pipe condensation section is 10 degrees,the comprehensive performance evaluation index is the largest,the value is 1.02,which is the optimal structural optimization mode of the heat pipe.Compared with the conventional finned heat pipe,the overall performance is improved by 2%and the heat transfer performance improvement rate is 15.9%.The research results in this paper can be applied to the field of low-temperature flue gas recovery,improve the heat transfer performance of heat pipe heat exchangers,and make heat pipe heat exchangers have wider application prospects.