A Study of Thermal Transpiration for the Development of a New Type of Gas Pump

Abstract

Thermal transpiration, the phenomenon of the flow of gases through porous media under the influence of a temperature gradient, can be utilized as a driving force in a new type of gas pump. A parametric study for determining conditions for the optimum performance of such a pump requires, in addition to the thermal transpiration measurements, appropriate independent measurements for determining the geometric properties of the porous media. Experiments were carried out on five porous ceramics and two Millipore fillers of different geometric properties. It was found that a maximum reduced efficiency of about 1 percent can be achieved with a thermal pump under optimum conditions. Equations based on the methods of nonequilibrium thermodynamics and the dusty-gas theory satisfactorily explain the experimental results and thus allow the prediction of pump performance for given conditions.