Energy Exchange between a Hot Tungsten Surface and Cold Gases

Abstract

The exchange of energy between a tungsten filament heated at 1710° to 2500°K and cold helium, neon, argon, nitrogen, and carbon dioxide was studied at gas pressures from 0.1 to 10 μ Hg. The exchange of energy was found to be directly proportional to the gas pressure in the 1- to 10-μ range but essentially independent of the filament temperature. The results are interpreted in terms of a process in which the impinging gas molecules are first physically adsorbed, then heated until they gain sufficient thermal energy to overcome the attractive forces of the tungsten surface. On the average, the gas molecules then desorb at a critical temperature that is independent of the filament temperature. For the gases studied, the critical temperatures lie between 580° and 1070°K. Reaction efficiencies of oxygen and carbon dioxide were calculated from the irreversible change in the rate of power consumption of the filament produced by introduction of these gases.