Numerical Simulation Method On Design Of Core Structure For Heat Exchanger

With the rapid development of heat exchangers in the direction of high efficiency,compact and lightweight,the optimization of heat transfer and flow performance has been the hot focus in study of the louvered fin heat exchangers.In this paper,the combination method of experiment and numerical simulation was adopted to investigate the heat transfer and flow performance of the louvered fin heat exchanger aiming to provide an efficient and reliable method for the optimal design and performance analysis of the louvered fin heat exchanger.According to the structural characteristics of the louvered fin heat exchanger,a representative characteristic element was selected as the core structure for heat exchanger and its numerical model was established.The independent of the mesh structure can determin the optimum core structure numerical model to ensure calculation precision and to save the computing time-consuming.This paper discussed the variation rules of heat transfer field,heat transfer and flow performance under various boundary conditions,such as the air inlet velocity briefly.This paper carried out the vehicle radiator test on its heat transfer and flow performance based on the wind tunnel experimental platform with consideration of various operating condition,such as air-inlet velocity and cooling flow rate.Through the comparation between experimental data and simulation results,it could be verified that the simulation of the proposed numerical model for core structure had high reliability and rationality.The particular characteristic rules of heat transfer coefficient,wind resistance and water resistance under different operating conditions were concluded and summarized.In the process of numerical simulation for the core structure,this paper provided 5 series of models with different structural parameters,such as fin pitch,fin thickness,louver angle,louver pitch and louver length.Then,this paper analyzed the influence of different structural parameters on the heat transfer and flow performance of the louvered fin heat exchanger,and evaluated the thermo-flow performance of heat exchanger in light of the j/f1/3 factor,which was regarded as the basic characterized coefficient.The results guided the optimal design of the louvered fin heat exchanger and provided a firm basis for the study on extensive method of the core structure.Then,this paper presented a method to design real heat exchangers through the numerical simulation of core structure.Based on the platform of MATLAB,a heat exchanger criterion equation fitting software was coded.On the basis of representing the heat transfer and flow process,this paper fit the heat transfer and resistance criterion equation for specific louvered fin heat exchanger by the least squares method.According to the type of data obtained from simulation,this software could provide a special criterion equation or a general criterion equation.This design method bridged the applied gap between the core structural numerical simulation and real heat exchanger design,and provided a research method for the optimal design and performance analysis of the louvered fin heat exchanger.This paper used the simulation data of numerical model to analyze the accuracy of the heat exchanger criterion equation fitting software.Taking the numerical model of different fin thickness as an example,a corresponding specific criterion equation was obtained through the software.In this paper,the j factor and f factor with different air inlet velocity were calculated with the obtained specific criterion equation and the experimental criterion proposed by Chang and Wang.The results of j factor and f factor by these two assessments fit relatively well with deviation in ± 10%.It could be concluded that the fitting results of the heat exchanger criterion equation fitting software had good reliability and accuracy,and was suitable for the optimal design and performance analysis of the louvered fin heat exchanger.