Numerical Study On Air Side Heat Transfer And Flow Characteristics Of Heat Exchanger Used On Electric Locomotive Transformer

With the enhancement of the comprehensive national strengthen, railway transport inChina gets rapid development. Especially in the recent10years, the quantities of electriclocomotive and the mileage of railway transport is rising year by year, which put forward higherrequirement of the heat exchangers used for cooling the electric locomotive main transformers.Since1990s, the aluminum plate-fin heat exchangers have begun to use in new type electriclocomotive, with its advanced design, compact structure, good performance and high reliability.Wavy fin as a kind of expansion strengthening heat transfer surface of plate-fin heatexchangers, has won wide application with the advantages of simple processing technology,high heat transfer performance. Using wavy fin structure on the air side of transformer heatexchangers can greatly increase the passing of air dirt particles, reduce the sediment andadhesion on the fins, and solve the problems of easy dirty, short cleaning interval period, bigmaintenance workload. The research on the thermal performance of wavy fin can not onlyimprove the system performance of transformer heat exchangers, but also improve the design ofplate-fin. It has important guiding significance to produce more high efficient andenergy-saving heat exchangers.Three-dimensional numerical simulations of air flow and heat transfer characteristics overthe wavy fin heat exchangers are presented in this paper. The results are compared with theexperimental data by Kays and London. It proofs the feasibility of the CFD technology used onthe study of air flow and heat transfer characteristics over the wavy fin. The heat transfer factor, friction factor and j/f factor as a function of Re are gotten usingthe3D numerical simulation. Calculate and compare the thermal performance of wavy fin fordifferent geometry parameters, which include the waviness amplitude, wavelength, fin spacing,fin height, fin thickness and corner radius. Analysis the different geometry parameters effect onthe heat transfer and resistance performance, by the changing of temperature fields and velocityfields. In additional, the enhancement heat transfer mechanism of wavy fin is explained in viewof field synergy principle. The results can provide theoretical guidance and technical supportfor the optimization of fin structure and improvement of heat transfer performance.