ABSTRACT

In some cryostats, the primary mode of heat transfer to the low-temperature region is thermal radiation. The primary mode of heat transfer from space-based cryo­ genic systems is generally radiant heat transfer. In this chapter, the phenomena of thermal radiation heat transfer and some of the physical phenomena associated with radiant energy transfer that are encountered primarily at low temperatures will be examined. The phenomenon of free-molecular conduction heat transfer, which is associated with conduction through gases at very low pressures, will also be studied. Although free-molecular conduction does not involve electromagentic waves, as does thermal radiation heat transfer, both radiation and freemolecular conduction are important in thermal design of dewars and cryogenic fluid transfer lines; therefore, both heat transfer modes will be considered in this chapter.