Another Possible Origin of Temperature and Pressure Gradients across Vane in the Crookes Radiometer

Abstract

In conventional studies on the Crookes radiometer, vane temperature was presumed to be higher at the black side than at the shiny side. In this study, a new hypothesis – vane is isothermal but accommodation coe‹cients are diŠerent at the black side and at the shiny side – has been proposed and examined using heat transfer and Direct Simulation Monte Carlo (DSMC) simulations. The results prove that the vane is indeed isothermal under the sunlight and that gas temperature and pressure at the black side with the perfect accommodation coe‹cient become higher than those at the shiny side with a small accommodation coe‹cient. The pressure gradient across the vane acts as an area force to push the vane from the black side. It is also found the glass bulb temperature strongly aŠects the revolution of the vanes.