| As an important component of an automotive air conditioning system,the heat transfer efficiency of the heat exchanger has an important impact on the performance of the automotive air conditioning system.The parallel flow heat exchanger is widely used in automotive air conditioning systems because of its small structure,light weight and high heat transfer efficiency.There are many factors affecting the heat transfer performance of the heat exchanger,of which the louvered fin structure is an important factor affecting the heat transfer performance of the heat exchanger.This paper takes the louvered fins in the parallel flow heat exchanger as the research object,analyses the heat transfer performance and air flow characteristics of the air side of the louvered fins through numerical simulation,establishes a Z-shaped louvered fin on the basis of the common louvered fin structure,and conducts numerical simulation study and structural parameter optimization design,the main research contents are as follows:(1)Taking ordinary louver fins as the research object,a numerical model was established and numerically simulated.The simulation results were fitted and verified with the Chang and Wang empirical correlation and the M.H.Kim empirical correlation.After verification,the maximum error of the heat transfer factor j with the Chang and Wang correlation was 9.59%,the maximum error of the friction factor f was 5.46%,and the maximum error of the heat transfer factor j with the M.H.Kim correlation was 7.35%,and the maximum error of the friction factor f was 7.49%,All are within the acceptable range of error,which can verify the feasibility of the established louver fin model.(2)Numerical simulation of common louvered fins under different working conditions,through the simulation results of the velocity field,temperature field,pressure field cloud analysis found that when the inlet velocity increases the amount of air entering the heat exchanger becomes larger,in increasing the heat transfer effect will also increase airflow disturbance,resulting in increased pressure drop in the import and export,in the optimization process of the louvered fins to be considered in improving the heat transfer performance while reducing the In the process of optimising the louvre fins,consideration should be given to reducing the pressure drop while improving the heat transfer performance.(3)On the basis of the common louver fins,a Z-type louver fin was established,and the simulation results were compared and analysed with those of the common louver fins,and it was concluded that compared with the common louver fins,the heat transfer factor j of the Z-type louver fins increased by 8.60%～11.95%,the friction factor f increased by4.36%～9.33%,and the comprehensive evaluation factor EJF increased by 9.03%～11.17%,the comprehensive analysis verifies that the comprehensive heat transfer performance of the Z-shaped louvered fins is better than that of the ordinary louvered fins.A number of segmented louvre fins were extended on the basis of the Z-shaped louvre fins,and a comparative analysis with the Z-shaped louvre fins revealed that the Z-shaped louvre fins had the best overall performance,verifying the reliability of the Z-shaped louvre fin structure.The structural parameters of the Z-shaped louver fins were optimised and the effects of five structural parameters on the Z-shaped louver fins were analysed:fin thicknessδ,louver spacing L_p,straight and curved section length ratio,window fin angleθand bending angleθ_z.Numerical simulations were carried out under six operating conditions in the inlet speed range of 1.5m/s-4m/s.The results show that the overall heat transfer performance of the Z-shaped louvre fins is best when the fin thicknessδis 0.1mm,the louvre spacing L_pis 1.1mm,the straight and curved section length ratio is 0.8mm/0.4mm,the window fin angle is 30°and the bending angleθ_zis 25°. |
PDF Full Text Request