The effect of load and addition of MWCNTs on silicone based TIMs on thermal contact heat transfer across Cu/Cu interface

Abstract

In the present work, the effect of thermal interface material (TIM) and load on contact heat transfer between hot and cold cylindrical copper specimens was assessed. Pristine silicone grease and multi walled carbon nanotubes (MWCNT) impregnated silicone grease was used as TIM. Copper specimens with L/D ratios of 1 and 5 were used. For copper specimens with L/D ratio of 1, the interfacial heat transfer was quantified by estimating the peak heat flux and integral heat flow using a lumped heat capacitance approach. An inverse solution to heat conduction equation was adopted for estimating heat flux transients for copper specimens with L/D ratio of 5. As the applied load increased from a no load condition to 5 kg, the peak heat flux and the corresponding integral flow increased significantly. Increasing the load above 5 kg did not result in any significant changes in the peak heat flux and integral heat flow for both sets of specimens. The effect of load on the contact heat transfer was significant in the absence of TIM. The use of 0.1 wt% MWCNT- silicone grease as TIM significantly increased the heat flow for no load condition. At higher loads, the effect of MWCNT was insignificant and caused deterioration in the heat flow parameters. Further, increasing the MWCNT content to 1 wt% in silicone grease decreased the heat flux transients at all loading conditions. The thermal contact resistance (RT) was calculated and it increased exponentially with the peak temperature difference (ΔTmax) between hot and cold specimens irrespective of the L/D ratio.