The thermal contact resistance at the interface of a bolted joint was investigated analytically, experimentally and numerically. Consideration was restricted to an ideal two-plate model for which the interface was perfectly flat. The two bolted plates made circular contact under uniform axisymmetric normal loading. The effect of important system parameters such as plate thickness, material property and loading radius were investigated.

In the analytical study, a closed form solution for the thermal contact resistance for a bolted joint was derived. A three-dimensional heat conduction equation was applied to a model which had a circular geometry and isoflux boundary conditions. The model was solved by the method of separation of variables and superposition. The results showed that an isoflux condition at the interface was valid when thermal conductivities and thicknesses of the top and bottom plates were equal or close to each other.

In the experimental study, the temperature drops were measured across a bolted piece with an interface and these were compared with drops across one solid piece without the interface at low air pressure. Only copper was used and all the copper plates had mirror-like surface finishes. The values of thermal contact resistance obtained from the experiment were consistently lower than those from the numerical analysis, due to air pressure in the vacuum chamber.

In the numerical study, isothermal and isoflux boundary conditions were used. The results of this investigation would be useful in the design of cooling for high power electronic devices bolted on heat sinks.

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