Research On Microchannel-Spray Combined Thermal Management Technology And Its Heat Transfer Performance For Engineering Vehicles

As an important part of infrastructure construction equipment and equipment industry,construction machinery plays a decisive role in the process of national construction.As a typical representative of engineering machinery,loaders have the characteristics of complex working conditions,multiple heat sources,harsh working environment,and long continuous working cycles,which puts forward strict requirements on the performance of the vehicle cooling system.The traditional cooling system can no longer meet the development needs of modern construction machinery due to problems such as mismatched heat dissipation capacity,low work efficiency,large space occupation,and uneven heat dissipation.Therefore,the development of new efficient and energy-saving cooling systems is of great significance and practical value for improving the comprehensive performance of construction machinery.In this paper,based on the advantages of high heat exchange coefficient and high surface area-to-volume ratio of microchannel heat dissipation technology and the characteristics of spray cooling technology such as compact structure,low energy consumption,high phase-change thermal efficiency and good temperature uniformity,a microchannel heat dissipation-spray cooling combined thermal management technology for construction machinery was proposed.The working heat source of construction machinery is cooled by the spray cooling system,and the microchannel heat dissipation system is used to dissipate the cold fluid whose temperature rises after heat exchange with the heat source.The temperature control strategy based on Long Short-Term Memory（LSTM）was constructed,and the heat exchange performance of the joint thermal management system was tested and analyzed by combining with the self-developed test rig,which provides an important theoretical basis and application foundation for the development of new cooling system for construction machinery.The main research work of this paper is as follows:（1）The series combined microchannel heat dissipation technology was proposed and the structural optimization design of the microchannel heat dissipation system was carried out.Research on the heat transfer mechanism of microchannel heat sink was carried out,and the experimental platform of series combined microchannel heat dissipation system was developed.Taking the heat transfer power and energy consumption ratio as the evaluation indexes,the influence of different factors such as the number of series combination of microchannel heat sinks,the flow rate of working medium and the mass fraction of nanofluids on the heat transfer performance of the heat dissipation system was clarified.In order to further improve the heat transfer performance of the series combined microchannel heat dissipation system,the structural optimization design of the diffuser and microchannel heat sink was carried out.An internal flow diversion scheme was proposed to improve the uniformity of fluid distribution at the diffuser outlet,and a Y-shaped double air channel expansion structure was developed to improve the combined flow effect of the double fans.A numerical calculation model of the microchannel heat sink was constructed,and the external structural parameters and microchannel morphology of the microchannel heat sink were optimized based on multi-factor orthogonal experiments.On this basis,a microchannel shape parameter optimization design method based on genetic algorithm was proposed.Simulation and experimental results show that the heat transfer performance of the system is significantly improved after optimization.（2）Numerical simulation analysis and multi-factor coupling experimental research on the heat transfer characteristics of spray cooling technology were carried out.Based on the study of heat transfer enhancement mechanism of spray cooling,a numerical calculation model of spray cooling system was constructed.The influence of spray angle,number of spray sources,spray height,heat transfer temperature difference and spray flow rate on the heat transfer performance of spray cooling system was clarified by field synergy principle.A visual experimental device for a spray cooling system based on a microchannel heat sink was developed,and a multi-factor coupling orthogonal experimental design was carried out.The impact of different factors on the heat transfer performance of the system was quantitatively studied through multi-factor sensitivity and significance analysis.In order to achieve real-time adjustment of parameters for different heat dissipation needs,a multiple linear regression model of system heat exchange power,pump power and power consumption ratio was constructed,and the experiment verified the accuracy of the linear regression model.Experimental research on nanofluid heat transfer enhancement technology was carried out,and the results showed that the system heat transfer power of Al₂O₃ nanofluid with a mass fraction of 0.7%increased by 10.76%.（3）A microchannel heat dissipation-spray cooling combined thermal management technology was proposed,and a study on the heat transfer characteristics of the combined thermal management system based on the LSTM temperature control strategy was carried out.Based on the research results on the heat transfer characteristics of series combined microchannel heat dissipation technology and spray cooling technology,the design of a microchannel heat dissipation-spray cooling joint thermal management system was carried out,and the control process of the joint thermal management system was clarified.A temperature control strategy based on the LSTM was proposed.By comparing the values of different evaluation indicators corresponding to the spray flow rate and fan control voltage under the other two modeling methods,the superiority of the LSTM control strategy was verified.A comparative test of the joint thermal management system under typical power modes was carried out,which proved that the proposed joint thermal management system based on the LSTM temperature control strategy has good heat transfer characteristics and economy.