Numerical Simulation Of Flat Tube Fin Heat Exchanger Based On POD Method

The Proper Orthogonal Decomposition(POD)method is an effective method for analyzing high dimensional data which uses a singular value decomposition(SVD)method to obtain a group of basis functions that satisfy the energy optimal in the least squares procedure,and can reconstruct the high dimensional physics problems by linear superposition a small number of spectral coefficients with this group of basis functions.In this paper,the POD reduced-order model is established and used to analyze the flow and heat transfer process of the flat tube bank fin heat exchanger.The results of the heat transfer of the heat exchanger which considerate by both interpolation and projection methods in POD reduced-order model are compared.The main works are as follows:(1)The finite volume method is used to analyze the heat transfer unit of the flat tube bank fin heat exchanger.The variation parameters in the calculation are: the velocity of airflow in fins and the structural parameters of the heat exchanger.The velocity of the airflow is determined by the actual flow rate which can be achieved by the flat tube bank fin heat exchanger in engineering reality.The change of the structural parameters of the heat exchanger is mainly by changing the fin spacing and transverse tube spacing.The steady-state model results of SIMPLE algorithm are used as the sample of the POD reduced-order model and references that compared with the simulation results of POD method.(2)Coupling calculation of spectral coefficients of univariate and multivariable were calculated by using Newton interpolation,Lagrangian interpolation and spline interpolation.The results of various interpolation methods are compared,the optimal POD interpolation model is selected to reconstruct the temperature field.(3)A reduce dimension projection of energy equation is used to deduce the POD projection equation under the three-dimensional body fitted coordinates,the reduced-order model of POD projection is constructed,and the spectral coefficients of the projection equation are obtained by substituting into the basis function.The temperature field under the condition we want is reconstruct by multiplying the spectral coefficients and the basis function.The results show that the POD interpolation method and the projection method are applicable to the multivariable steady state problem,and the POD method saves a lot of computation time than traditional FVM calculation method.Compared with the simulation results of two kinds of models,the derivation process of POD reduced order model projection is complicated,but this model is more robust and has obvious advantages for the calculation of complex physical problems of geometric boundary.Due to the limitations of different interpolation methods,the simulation accuracy under different interpolation methods are quite different when use the POD interpolation method to reconstruction physical field,and there is an error cannot be ignored between the results of overall interpolation and original physical field,and the results are always robustness.But in general,POD interpolation method is simple to calculate,the calculation principle is clear and easy to understand,while the running time of calculation is lower than the POD projection methodThe heat transfer performance of multi-structure heat exchangers under multiple operating conditions was obtained by changing the air flow velocity,fin spacing and transverse tube spacing of the flat tube bank fin heat exchanger.The three-dimensional POD model of body-fitted coordinates is also provided for the follow-up study.The calculation method in this paper greatly improves the numerical simulation efficiency and broadens the application range of POD method in the field of engineering research.The conclusion provides a theoretical reference for the optimization and structural parameter design of the flat tube bank fin heat exchanger.