Temperature distribution in a tungsten electrothermal atomizer

Abstract

Temperature distribution in the tube surface of a tungsten electrothermal atomizer (WETA-82) has been studied both theoretically and experimentally; also, the temperature distribution in the gas inside the atomizer has been studied theoretically. A theoretical model of the temperature distribution in the tube surface and in the gas inside the atomizer is proposed. It is considered that thermal radiation to the surroundings and beat conduction towards the water-cooled electrode supports are the only paths for heat loss, and electrical resistive heating and conduction from adjacent nodes are the only sources of heat gain. The time rate of change in temperature of the atomizer is expressed in the form of a differential equation. A finite-difference form of the differential equation is used in a computer program to calculate the temperature at each time step. Optical pyrometry was used to determine the surface temperature of the tube atomizer. The model predicts that an increase in the heating rate of the tube atomizer will slightly decrease the temperature gradient over the tube circumference; however, unambiguous observation of this decrease could not be made in the sequentially measured temperature difference between two selected point using optical pyrometry. Variation in the hydrogen content of the hydrogen-argon mixture purge gas did not have a significant effect on the temperature gradient of the tungsten tube surface. The results of this study have indicated possible improvements in the atomizer design with a view to making the temperature distribution over the circumference of the tube atomizer more uniform.