Research On Planar Near-field Thermal Radiation Coupling Effect In Thermal Contact Resistance Between Solid-solid Interface

Thermal contact phenomena have widely existed in the engineering fields involving energy,microelectronic packaging,aerospace,cryogenics,etc.,while thermal contact resistance(TCR)is one of the important indicators weighing the heat transfer efficiency among the interfaces.The theoretical prediction and experimental measurement for the TCR have always been a bottleneck issue about system thermal management.The mechanism of the TCR is very complex,which is the result of the triple interaction among geometry,mechanics and thermal.In general,there are three heat transfer modes including conduction,convection and radiation at the contact interface.The previous research on the TCR usually neglected the effect of interfacial thermal radiation.With the development of micro-nano technology,it has been pointed out that the heat flux of the micro-nano spacing thermal radiation(near-field thermal radiation)can exceed the black body radiation limit by several orders of magnitude.In this paper,the research on planar near-field thermal radiation coupling effect in thermal contact resistance between solid-solid interface is theoretically investigated considering both the thermal contribution from contact and non-contact regions respectively based on the classical TCR theory and near-field thermal radiation theory.To consider the effect of the near-field thermal radiation on the TCR,the heat transfer of the non-contact regions is simulated as the near-field thermal radiation between the mean planes in contact.The contribution of the thermal conduction and thermal radiation in the contact interface and the coupling synergy are theoretically analyzed.The concrete research comprises two main aspects:1.Investigating the interfacial coupling contact heat transfer between the same materials of several commonly used metals in engineering.The TCR is considered to be a parallel connection of the thermal conduction resistance and the thermal radiation resistance.The conduction resistance of the contact area is calculated using the CMY TCR model.On the other hand,the near-field thermal radiation of the non-contact area is calculated using fluctuational electrodynamics(an ab initio method).The thermal conduction resistance and near-field thermal radiation of aluminum-aluminum,copper-copper,silver-silver,lead-lead are estimated.The TCR of aluminum is further analyzed and discussed to explore the contribution of interfacial heat transfer and whether the near-field thermal radiation needs to be considered in the TCR.2.Investigating the interfacial coupling contact heat transfer between dissimilar typical non-metallic materials(e.g.,silicon,silicon dioxide,silicon carbide)in the field of electronics.The effects of roughness,temperature and near-field thermal radiation on the TCR are investigated.In terms of the contact heat conduction,fractal-like random rough surfaces are artificially constructed and the corresponding surface roughness power spectra are used as input to estimate the heat transfer across real contact regions.The contribution of near-field thermal radiation is considered in the non-contact area and a proximity approximation is used to consider the roughness scattering effects on the radiation.Due to the asymmetric contact on the material and to consider the temperature effect,the study also involves some complex phenomena such as thermal radiation rectification,heat flow direction dependence of TCR that can be observed in the previous studies.Finally,the TCR coupling near-field thermal radiation effect at the interface is explored.