COOLING OF A GAS WITH A TEMPERATURE-DEPENDENT THERMAL-CONDUCTIVITY

The question of how the temperature dependence of the thermal conducti vity of a gas affects its cooling rate is addressed by considering the thermal evolution of a hot gas brought into sudden contact with cold walls. It is shown that if the thermal conductivity coefficient increa ses with decreasing temperature, as it is the case for the cross-held heat transport in a strongly magnetised plasma, the whole scenario of the cooling process can be completely changed, resulting in a substant ial reduction of the gas cooling time. Besides demonstrating these unu sual cases of heat conduction, the paper also aims to illustrate how ' 'physical'' approaches to nontrivial problems allow to tackle them ana lytically by quite simple mathematical means.