Analysis Of Flow And Heat Transfer Performance Of Flat Tube-Bank-Fin Heat Exchanger With Vortex Generators On Both Sides Of Fin Using POD

In scientific research,in order to explore the flow and heat transfer problems of complex structures,numerical simulation methods such as simple algorithm are often used instead of experiments to solve the problems of conditions and funding constraints.However,these traditional numerical methods have many inevitable disadvantages,such as long running time,large operating load and high requirement for computer configuration,which are difficult to adapt to the rapid development of actual industrial production.To overcome this limitation,the proper orthogonal decomposition?POD?is introduced in this study,which can greatly reduce the number of unknowns,transform the complex high-order model into the low-order model,and simplify the solving process of flow and heat transfer problems.While ensuring the accuracy of calculation,the prediction of physical field outside sample working condition is accelerated.This high-fidelity acceleration technology has been proved to be widely used in the engineering field with simple structure.Based on this background of engineering design and calculation,under the coupled thermal boundary condition,the paper takes the flat tube-bank-fin heat exchanger with vortex generators on two sides of fin as the research object to explore the applicability and reliability of POD low-order model in the analysis of complex flow and heat transfer problems.The details are as follows:?1?When the Reynolds number?Re_a?of air side,the fin spacing?T_p?and the transverse tube spacing?S1?change respectively,the FVM high-order model is used to calculate and analyze the temperature and velocity fields of flat tube-bank-fin heat exchanger with no vortex generator on the surface of fin,vortex generators on one side of fin and vortex generators on both sides of fin.some of these results are used as samples to extract the basis function of POD low-order model,and the other part is used as non-samples for comparison with the physical field reconstructed by POD low-order model.?2?The SVD?single value decision?method is used to extract the basis functions of three kinds of flat tube-bank-fin heat exchanger with different fin structures under the condition of single parameter,two parameters and three parameters change respectively,Then the spectral coefficients are calculated by selecting some basis functions whose eigenvalues and energy contribution rates meet the requirements.?3?When single parameter,two parameters and three parameters change respectively,the physical field reconstructed by POD linear interpolation method for three kinds of flat tube-bank-fin heat exchangers with different fin structures is compared and analyzed with the calculated results of FVM high-order model under the same working condition.The calculation speed is also compared.The results show that:when there is no vortex generator on the surface of fin,the maximum relative deviation of the velocity field calculated by POD method and FVM method is 8.5788%,which is obtained when the two parameters change?Tp=5.25mm S1=40mm Rea=1700?;the maximum relative deviation of the temperature field calculated by POD method and FVM method is 8.8619%,which is obtained when the two parameters change?Tp=5.25 mm S1=40mm Rea=900?.Compared with the FVM method,using POD method the computation speed is increased by at least 1411 times.When vortex generators on one side of fin,the maximum relative deviation of the velocity field calculated by POD method and FVM method is 1.4409%,which is obtained when the three parameters change?T_p=5.75 mm S₁=46mm Re_a=1700?;the maximum relative deviation of the temperature field calculated by POD method and FVM method is 1.3952%,which is obtained when the two parameters change?Tp=5.75 mm S1=42mm Rea=1300?.Compared with the FVM method,using POD method the computation speed is increased by at least 1051 times.When vortex generators on the both sides of fin,the maximum relative deviation of the velocity field calculated by POD method and FVM method is 9.9124%,which is obtained when the three parameters change?T_p=5.75 mm S₁=46mm Re_a=1700?;the maximum relative deviation of the temperature field calculated by POD method and FVM method is2.8560%,which is obtained when the single parameter change?T_p=5.75 mm S₁=42mm Re_a=1300?.Compared with the FVM method,using POD method the computation speed is increased by at least 1049 times.Compared with the case of single parameter change and two parameters change,the prediction accuracy of POD low-order model for complex structure physical field is slightly lower when multiple parameters change,which indicates that the existing POD prediction technology cannot fully adapt to the calculation condition of"multi-parameter change and more complex heat exchanger structure coexist".In a word,under the coupled thermal boundary condition,the POD method can predict the flow and heat transfer process in the flat tube-bank-fin heat exchanger with different structures,and obtain a relatively ideal result for the calculation of a certain number of parameter changes.However,there are still some shortcomings in solving the problem of"more parameters change and more complex structure coexistence",which presents a new challenge for further developing the key technology of POD method to improve the numerical design efficiency of industrial equipment with complex structure and expand its engineering application field.