Study On Flow And Heat Transfer Characteristics Of Flat Tube-Bank-Fin Heat Exchanger With Sine Wave Fin Based On POD Reduced-Order Model

The optimization of structural design for flat tube-bank-fin heat exchanger often requires numerical simulation of complex calculation conditions that change multiple parameters at the same time.However,numerical simulation,as the main technical in flow and heat transfer research field,still exists a series of drawbacks such as large calculation load,low efficiency and inconsistency with actual production requirements,which affect the design optimization efficiency of the flat tube-bank-fin heat exchanger.The POD(Proper orthogonal decomposition)reduced-order model can greatly improve the numerical calculation efficiency by advantage of its reduced-order solution and mesh-free advantages,but the existing research using POD method mainly focuses on the idealized model.the POD analysis about the flow and heat transfer characteristics of the sine wave fin flat tube-bank-fin heat exchanger with more complicated physical structure and mathematical description has not been reported.The application,improvement and promotion of POD reduced-order model have important engineering practical significance.Compared with previous studies,this paper established a POD reduced-order model with higher applicability to various types of sine wave fin flat tube-bank-fin heat exchangers for the first time,and the application,POD reduced-order model to complex flow and heat transfer models,was compared and analyzed.The reliability and economy of the POD,and the practical significance of the POD reduced-order model is further discussed.The main tasks are:(1)The alculation results using the FVM(Finite volume method)as the high-order sample data of the POD reduced-order model,and using the average Nusselt number on the wall,the air side pressure drop and the enhanced heat transfer enhancement JF factor as the evaluation indicators,quantitative analysis of the flow and heat transfer characteristics of with different fin types and structural optimization design;(2)Based on the theory of body-fitted coordinate transformation,the body-fitted coordinate,suitable for various forms of sine wave fin flat tube-bank-fin,is established.Use SVD(Singular value decomposition)decomposition to obtain a higher average energy mode to obtain the basis function of the POD reduced-order model,and the spectrum coefficients of the POD reduced-order model are obtained respectively through the linear interpolation method of one element,two elements and three elements;(3)Based on the obtained POD reduced-order model basis functions and spectrum coefficients,three different parameter changes(single parameter,double parameter and three parameter changes)are constructed separately.The the relative deviation and calculation efficiency of numerical results is compared between the POD reconstruction physical field and the FVM,and the reliability of POD reduced-order model is further examined.The study shows: the prediction accuracy of the POD reduced-order model for the physical field distribution,using the same method to obtain the spectral coefficients and basis functions,shows a downward trend as the air-side Reynolds number increase.The relative deviation between the POD reconstruction temperature field and the FVM calculation result is mainly in the surface area of the sine wave fin when single parameter and dual parameter change,and shows a significant decreasing trend along the mainstream direction(positive x direction);The difference of the velocity distribution obtained by the two methods is mainly concentrated in the mainstream area.Compared with the other two parameter changes,the POD reduced-order model is applied to the flow and heat transfer characteristics of flat tube-bank-fin heat exchanger with sine wave fin heat exchanger with lower prediction accuracy when the three parameters change.Applying the POD reduced-order model to the performance optimization design calculation of the flat tube-bank-fin heat exchanger heat exchanger with sine wave fin can greatly improve the calculation efficiency and reduce the calculation cost.The calculation efficiency is lower than single-parameter and double-parameter when the three parameters change,but its calculation time is still far lower than the FVM.Based on the POD reduced-order model,this paper studies the flow and heat transfer characteristics of various types of sine wave fin flat tube-bank-fin heat exchangers,which has important guiding significance for improving the calculation efficiency in industrial production.Expanded the application range of the POD reduced-order model.Since this research strictly controls the number and value range of variable parameters,the conclusions obtained have certain limitations,it is also necessary to make breakthroughs in the development of key POD technologies,the generation of body-fitted mesh generation and the establishment of reduced-order models for the construction of reduced-order models with more complex structures and mathematical descriptions.