Thermal Performance And Optimization Of Plastic Aluminum Composite Column Airfoil Radiator

In this paper,two groups of airfoil radiators with plastic-aluminum composite columns were selected to study,whose water-passage pipeline is plastic and heat-transfer components are aluminum alloy.The shape size of specimen one is845mm×660mm×80mm and the shape size of specimen two is 745mm×660mm×80mm.Carry out the following several research work and drawing corresponding conclusion:1)Establishing the mathematical model of isolated fins of plastic-aluminum composite column airfoil radiator,taking the unit-length plastic-aluminum composite column airfoil radiator as the object,the heat transfer principle of circular tube wall and uniform cross-section fins of radiator is calculated theoretically,and the heat conduction differential equation is determined by Fourier law and the first law of thermodynamics.Then,according to the single-value condition of the radiator heat dissipation process determined the governing equation.The theoretical heat dissipation of the plastic-aluminum composite column airfoil radiator under the standard working condition is obtained by considering the convective heat transfer and radiative heat transfer of the radiator.The heat dissipation of the sample 1 is920W,and the heat dissipation of the sample 2 is 828W.2)The thermal performance tests of two groups of airfoil radiators with different sizes of plastic-aluminum composite columns were carried out at low?medium and high temperatures on a radiator test rig.The experimental data of three working conditions were recorded,then,according to the measured results of each working condition,the least square method was used to fit the regression,and the binary linear regression equation method was used to obtain the standard characteristic formula that is to say,the formula and curve for calculating temperature difference and heat dissipation are obtained.The formula of heat dissipation of specimen 1 is Q?28?7.678?t^1.2657,the correction factor is 0.99995,and the heat dissipation under the standard working condition is 937 W.The formula of heat dissipation of specimen2 is^1.2743_Q?28?6.660?t,the correction factor is 0.9996,and the heat dissipation under the standard working condition is 840W.This shows that the formula of heat dissipation of exponential form fitted by this method is credible and can satisfy the requirement of engineering.Comparing the actual heat dissipation of the radiator with the theoretical heat dissipation,the relative errors are 2.6%and 1.3%respectively,which verifies the accuracy of the theoretical calculation formula.This experiment also use the infrared thermal imager to measure the temperature of the radiator to verify the accuracy of the theoretical calculation.3)The physical model of the single-column of specimen 1 was established by ICEM software,and the grid was divided into fluent to set the conditions.The heat dissipation and temperature nephograms of the model were simulated under four working conditions:low,medium,high temperature and standard working conditions.Under the standard working condition,the heat dissipation simulated by Fluent is860W.Comparing the heat dissipation simulated with the actual heat dissipation measured by experiment and the heat dissipation calculated by theory,the relative error between them is less than 10%.It shows that the process of modeling in ICEM software and the control conditions for calculating in Fluent software are accurate.4)Through the above theoretical calculation model of heat dissipation,this article further selects the specimen one for structural optimization.By adjusting the thermal conductivity of plastic pipes?making?=0.2,1,3,9,15W/?m?K??and the shape and size of aluminum alloy fins?making fin a=1-20 mm,fin c=49-91 mm?,the theoretical heat dissipation of the radiator and the metal heat intensity of the aluminum alloy fins are calculated,then finding a divergence which accords with the greater heat dissipation and the larger aluminum alloy metal heat intensity.It is found that the heat dissipation of the radiator increases with the increase of the thermal conductivity of the plastic pipe,but when the thermal conductivity of the plastic pipe is greater than 6W/?m?K?,the increase of the heat dissipation will not be obvious;with the increase of the fin length of the radiator,the heat dissipation of the radiator increases gradually,and the metal thermal strength decreases,and vice versa.By comparison,the better radiator parameters range is:the thermal conductivity of plastic pipe is3W/?m?K?<?<5W/?m?K?,the height range of fin a is 2 mm<a<8mm,and the length range of fin c is 65 mm<c<83 mm.