Research On Thermal Contact Resistance Of Solid-solid Interface Based On Fractal Theory

Between the machine parts of the engineering system,the contact surface between solids is everywhere.Due to its inherent roughness,the contact between the engineering surfaces is incomplete,which greatly affects the heat transfer between the components.A key consideration in thermal analysis and design between machine components is the accurate quantification of heat transfer across interfaces.To make accurate aerothermal predictions for computational fluid dynamics and heat transfer models,the thermal contact conductance(TCC)between the interfaces must be known in advance.The reason why the TCC model is used as the input of computational fluid dynamics is that the TCC model is based on the assumption that the size and shape distribution of the surface roughness is too simplistic.The fractal theory can show a large number of details of a rough surface,and can reflect the disorder,randomness,multi-scale and self-affine of the rough surface,and is not affected by the sampling length and resolution of the measuring instrument.Therefore,this paper is based on fractal theory to model and predict the thermal contact conductance between solid contact surfaces.The main research content and summary are as follows:1.In this paper,a fractal contact thermal conductivity model is established by improving the CMY model to realize the prediction of contact thermal conductivity.First,the W-M function is used to construct an isotropic fractal surface,and it is verified by the power spectral density function.Secondly,analyze the three deformation states of the contact point,including elastic deformation,elastic-plastic deformation,and complete plastic deformation.Finally,the integral method is used to obtain the overall shrinkage thermal conductivity,while considering the gas gap conductance.The results show that the WM function can construct an isotropic surface;the contact thermal conductivity increases with the increase of pressure and fractal dimension,and decreases with the increase of roughness;when the pressure is small,the gap gas Thermal conductivity is the main heat transfer method.This model can provide a theoretical basis for the application of heat conduction in electronic equipment and other fields.2.To verify the accuracy of the model,the team built an experimental device that complies with international standards.The contact pairs of aluminum alloy-stainless steel,aluminum alloy-brass,stainless steel-brass,and aluminum alloy-aluminum alloy were carried out in the air under a small pressure.Steady-state experiment.The thermal contact resistance test device is manufactured based on ASTM E1225-09.The main components are pressure devices,vacuum devices,temperature collection devices,test devices,and control panels.Using the steady-state method to measure the TCC of a sample,the key to the test is to create a steady-state one-dimensional heat flux between the two samples.The test sample is between the heating block and the water-cooling block,and the heating block and the water-cooling block respectively generate temperature differences on the surface of the upper and lower samples,so that the two samples have one-dimensional axial heat flow.