Numerical Simulation And Experimental Study On Heat Transfer Characteristics Of A Plain Plate Fin-and-tube Oil Cooler

The plain plate fin-and-tube oil cooler is widely used in the lubricating oil cooling of large hydraulic machinery.It is of great significance to carry out research on its heat transfer performance and apply it to actual production.Computational fluid dynamics method is used to numerically simulate the plain plate fin-and-tube oil cooler,and a small test bench for the plain plate fin-and-tube oil cooler is set up,along with a test measurement system to investigate its heat transfer characteristics and pressure drop performance,which provides a basis for the numerical simulation.Numerical simulation is performed on the selected characteristic structure to study the effect of the shell-side flow rate,plate-fin spacing,heat exchange tube arrangement and its material on heat transfer performance.Also,four factors such as plate-fin spacing,outer diameter of the heat exchange tube,shell-side medium flow rate and wall thickness of heat exchange tube together with corresponding levels are subjected to four-factor four-level orthogonal test to analyze the influence of each factor and the degree of primary and secondary.In view of the small spacing and large number of shell-side plate-fins,the porous media model is used to simplify the structure,and the feasibility of the simplified model is confirmed which can be applied to the modeling of the overall equipment.The main results of the article are as follows:(1)As the shell-side flow rate of the plain plate fin-and-tube oil cooler rises,the heat transfer coefficient and the shell-side pressure drop keep increasing,while the rate of change of it gradually decreases and tends to be stable.Therefore,when the cooling water flow rate of the tube side is 1.45m~3/h,the optimal flow rate of the shell side is 1.6m~3/h.(2)When the plate-fin spacing is 4mm,its heat transfer coefficient is 108.7W/(m~2·K),getting the best heat transfer effect.The plate-fins spacing mainly affects the distribution uniformity in the multi-layer small-pitch channels.When the plate-fin spacing is 4mm,the flow distribution is the most uniform.(3)When the heat exchange tubes are arranged in a triangle,the heat transfer effect is better than other arrangements on the one hand due to its ability to increase the contact area between the shell-side fluid and the heat exchange tubes and on the other hand because it can enhance the disturbance of the shell side medium,whose heat transfer coefficient is 113.52 W/(m~2·K).(4)The thermal conductivity of the tube material has a certain effect on the heat transfer coefficient.Feature models is simulated,the exchange tube material of which is BFe10-1-1,C11000,304 and 316L.The correlation between the heat transfer coefficient and the thermal conductivity of the material is fitted based on the empirical formula for heat transfer coefficient of traditional shell-and-tube heat exchanger.(5)The plate-fin spacing is the main factor that affects the heat transfer coefficient of the plain plate fin-and-tube oil cooler.The optimal level combination obtained by the four-factor four-level orthogonal test is the plate-fin spacingσ=4mm,the outer diameter of the heat exchange tube d_o=10mm,the shell-side flow rate L_q=2.5m~3/h,and the heat exchange tube wall thickness s=1.25mm.In this state,the heat transfer effect of the oil cooler achieves the best.On the basis of the results of the orthogonal experiment,the correlation formula of Nu criterion is obtained by fitting to guide its industrial application.(6)Numerical analysis of the optimal combination of the oil coolers is carried out,and the relationship between Nu with Re between channels in a group of fins is studied.The results show that the heat transfer is mainly concentrated near the baffles,and the heat transfer in the middle of the two baffles is relatively stable.(7)The porous medium model is used to simplify the shell side structure of the plain plate fin-and-tube oil cooler.After the simplification,the error of the simulation result is kept within 5%.Then the simplified method is used to simulate the overall model of the oil cooler,and the error is about 10%,which verifies the feasibility of selecting feature models for research.On this basis,a large-scale study of the equipment is carried out to verify the heat transfer coefficient correlation equation obtained by the orthogonal experiment is suitable for a larger diameter range.