Introduction

In vacuum environments on spacecraft, convective heat transfer is absent and conduction becomes a more important heat-transfer mechanism than it is for most terrestrial hardware. The heat generated by piece parts within a spacecraft electronics box must flow, by conduction, to the box surface, where it is either radiated away or conducted to a heat sink. Included in this conductive path are a number of joints where heat must be transferred by contact between surfaces. These joints include screws or Wedglock guides that attach circuit boards to an electronics-box chassis, and bolts used to attach the electronics box to a spacecraft shelf or heat-pipe network. Hence the thermal conductance of contacting surfaces is an important parameter for spacecraft thermal design.

This chapter presents analytical tools for modeling thermal joint resistance (or its inverse, conductance) between contacting surfaces. Many different analytical models have been developed over the last 40 years that take into account the different physical phenomena involved in contact heat transfer. What follows is not a complete survey of these models, but a look at some that can be of practical use in spacecraft thermal design.

Unfortunately, no universal model exists that can enable one to predict the joint resistance between any two surfaces. To determine which of the available analytical models is appropriate for a situation, the thermal engineer must assess the surface conditions, addressing questions such as:...