POD Analysis Of Flow And Heat Transfer Performances Of Flat Tube-Bank-Fin Heat Exchangers With Different Wing Vortex Generators

The traditional finite volume method（FVM）has the disadvantages of large storage space and long time consumption in numerically analyzing the flow and heat transfer problems of complex structures.With the rapid development of industrial technology,there is an urgent need to develop a fast and accurate calculation method.The proper orthogonal decomposition（POD）method can reduce the amount of data stored in the description of physical processes,greatly shorten the calculation time and ensure accuracy.However,most of the existing studies on the flow and heat transfer problems using the POD technology are based on a simple physical model and a single thermal boundary condition.These conditions deviate from the actual physics.In this paper,for the flat tube-bank-fin heat exchanger with vortex generators of different structures,a POD reduced-order model based on body-fitted coordinates system under coupled heat transfer boundary conditions was established,and the application of the POD method was analyzed.Main tasks as follows:（1）The calculation area of the physical model of the flat tube-bank-fin heat exchanger equipped with different-structures vortex generators（right-angle triangular wing,isosceles triangular wing and rectangular wing）was discretized in the body-fitted coordinates system.The finite volume method（FVM）not only established a high-order solution model for the flat tube-bank-fin heat exchanger with the different-structures vortex generators,but also performed multi-case simulation calculations of flow and heat transfer performance under coupled boundary conditions,which provided samples for the application of the POD method.（2）Lagrange interpolation,linear interpolation and Newton interpolation were used to solve the spectral coefficients;the SVD（Singular Value Decomposition）method was used to extract basis functions from the FVM higher-order model samples;Combining spectral coefficients and basis functions,the POD reduced-order model suitable for solving the flow and heat transfer problems in the flat tube-bank-fin heat exchanger with vortex generators was established,and the temperature and velocity fields under different conditions were reconstructed.（3）The effects of changes in parameters such as the air-side Reynolds number,fin spacing,and lateral tube spacing on the flow and heat transfer performance were analyzed,and the calculation results of the POD reduced-order model were compared with those of the FVM higher-order model.The research showed that the established POD reduced-order model has high calculation accuracy,and it can substantially predict complex physics problems under coupled boundary conditions.In addition,the calculation time is 1/12472～1/1204 of FVM method.In this research,heat exchange units of three wing types vortex generators flat tube-bank-fin heat exchangers were employed and their reconstruction processes and results using POD reduced-order models were been compared.It was found that the calculation accuracy of POD reduced-order models for velocity field and temperature fields is consistent under coupled boundary conditions.From the point of view of the effect of parameter changes on the physical field,the air-side Reynolds number had the strongest correlation with the temperature field and velocity field of the heat exchange unit,and the influence of the fin spacing and the lateral tube spacing changes was smaller.The accuracy of the physical field reconstructed by different interpolation methods was quite different.Among the three interpolation methods,Lagrange interpolation method had the highest accuracy,and Newton interpolation method had the lowest accuracy.The Lagrange interpolation reconstruction results using isosceles triangular wing（T_p=5.0mm,S₁=40mm,Rea=500）showed that the maximum average relative deviations of the temperature field is 0.0113%and rectangular wing （T_p=5.0mm,S₁=40mm,Re_a=500）showed that the maximum average relative deviations of the velocity field is 0.00168%.Besides,the Newton interpolation reconstruction results using right-angle triangular wing（T_p=5.0mm,S₁=40mm,Re_a=1700）showed that the maximum average relative deviations of the temperature field is 1.1200%and isosceles triangular wing（T_p=5.0mm,S₁=40mm,Re_a=500）showed that the maximum average relative deviations of the velocity field is 1.36125%.In this paper,the POD reduced-order model was employed to compare the flow and heat transfer of three different wing types vortex generators flat tube-bank-fin heat exchangers and was explored in complex structure and complex boundary condition heat exchangers Feasibility and reliability in numerical analysis,which provided a theoretical reference for improving the numerical design efficiency of flat tube-bank-fin heat exchangers with vortex generators and expanding the application field of POD technology.