Experimental Study Of Interstitial Gas Film’s Effects On Thermal Contact Resistance Between Solid-Solid Interface Under Multiple Working Conditions

Thermal contact resistance(TCR)is a core parameter that characterizes interface heat transfer rate.It is widely used in various research fields,such as low-temperature physics,nuclear engineering,aerospace manufacturing,nanotechnology,and microelectronics.In particular,TCR is an important consideration that cannot be ignored in high-precision thermal design involving interfacial heat transfer.The influence of interfacial gap gas is critical in improving TCR models’ prediction and experimental measurement accuracy.Due to various factors,such as the small gap distance between extremely precise contacting interfaces;the highest fluid velocity in supersonic aircraft structural components;and the extremely low media density in aerospace vehicles and satellites,the interfacial gap gas is usually in a rarefied state,resulting in the fact that its effect on TCR would be even more complex.Therefore,investigating the influence of interfacial gap gas on TCR under various working conditions is of great significance for improving the experimental measurement accuracy and model calculation accuracy of TCR in engineering applications and scientific research.In this work,a self-developed experimental apparatus is engaged to measure the TCR and gas thermal resistance between solid-solid interfaces under different working conditions.The thermal gas resistance calculation models in different fluid regions are summarized.Based on the experimental results,the influence of multiple experimental parameters on TCR and thermal gas resistance is discussed and reasonable explanations are provided for experimental phenomena.Deducted predictions of the variation trend of TCR and gas thermal resistance versus different experimental parameters are put forward based on the discussion and experimental results.Finally,the experimental results of gas thermal resistance and the model calculation results are brought into comparison,and the correlation is acceptable,demonstrating that the calculation model has a certain practicality and reference value.The main contents of this work are introduced as follow:1、This work involves calculating the characteristic length and molecular mean free paths of the gap gas under different conditions to obtain Knudsen number.Based on the Knudsen number,the gap gas states under different working conditions are divided into three fluid regime: continum regime;transitional regime;free molecular regime.The gap gas is considered as a thin plate with a certain thickness to calculate its thermal resistance.A thermal conductivity correction factor is introduced,and the thermal conductivity of the gas in different fluid regimes is compensated and corrected.The calculation models of the gas thermal resistance in different fluid regions are systematically summarized.2 、 An experimental device for TCR measurement is built up based on the one-dimensional steady-state heat flow method,which complies with international measurement standards,and the device possesses following the advantages: multiple experimental parameter adjustments;complete automation control;independent and intuitive operating users’ interface.The TCR and gas thermal resistance of the solid-solid interface under multiple working conditions are measured.An error analysis over experimental results is performed,showing a maximum error of less than 10%.To verify the stability and reliability of the experimental data,repeated experiments are conducted,showing a maximum error of less than 5%,which is within the numerical range of error analysis.One-dimensional steady-state heat flow verification is also conducted,showing a maximum error of less than 7%,proving that the experimental results have good stability and reliability.3、Based on the experimental results,the effects of interface pressure,heating power,environmental vacuum degree,surface roughness,and thin film thermal interface material on TCR and gas thermal resistance are investigated,and the causes of experimental phenomena are explained in combination with the gas molecular heat transfer mechanism at the micro-level.Combining theoretical analysis,reasonable predictions of the variation trend of contact thermal resistance and thermal gas resistance with relative parameters are proposed.The model calculation results and experimental results are compared,with an average deviation of 23%,indicating that the calculation model for the gap gas thermal resistance summarized in this work has certain practicality and reference value.