Heat transfer from small tungsten spheres into an ambient H2 atmosphere

Abstract

The transfer of heat from tungsten spheres into an ambient H2 atmosphere was investigated. The spheres had a radius between 35 and 100 µm and were heated to 1400–2000 K by a laser beam. The H2 pressure ranged from 35 to 1000 mbar. Heat transfer by convection is effective with large spheres and high H2 pressures. With small spheres and low H2 pressures, a pronounced temperature discontinuity at the interface between the tungsten sphere and the ambient gas was observed. The results are relevant to the modelling of gas-phase transport phenomena in laser processing.