Effect of gravity and intermolecular potential on 3He-4He separative performances of 'cryogenic-wall' thermal diffusion column

The effect of gravity and intermolecular potential on He-3-He-4 separative performances of the thermal diffusion column were analysed by using the two-dimensional rigorous numerical solution of convection-diffusion equations with cold wall temperature T-c, pressure P and temperature difference Delta T between the hot and cold walls being parametrically changed, while the feed flow rate F and the cut theta being a constant 1 cm(3) min(-1) (converted at 288.15 K, 0.1 MPa) and 0.1, respectively. On the moon, the optimum pressure P-opt, where the total separation factor alpha beta takes a maximum, is about root 6 times greater than that of the earth. The way in which the thermal diffusion factor alpha(T) varies with temperature depends on the intermolecular potential model. Therefore, separative performances of the thermal diffusion column vary according to the intermolecular potential with T-c and Delta T being changed. In design analyses, it is important to evaluate the temperature dependence of alpha(T) of helium. (C) 1998 Elsevier Science S.A. All rights reserved.