Cryosorption Pumping of Air on Molecular Sieves at 77 K—The Ultimate Achievable Vacuum

Publisher Website
Google Scholar
Abstract
The cryosorption pumping of air and some of its components on Molecular Sieve 5A pellets was studied at 77 K and in the pressure range from atmospheric to about 10−6 Torr. The lowest residual pressures attainable in an enclosure by cryosorption pumping of air was calculated by the graphical method of Turner and Feinleib, using the latest adsorption isotherm data available. This method was also used to evaluate the relative efficiency of single-stage and two-stage cryosorption pumping. In the latter case, it is shown that much lower residual pressures can be reached by isolation of the “non-condensable” air components in the first pumping stage under dynamic conditions than by allowing this stage to reach adsorption equilibrium. The calculations were confirmed experimentally by means of a new type of cryosorption pump. This pump was designed to optimize heat transfer between adsorbent pellets and refrigerant fluid, as well as gas flow at transition range pressures.

This publication has 0 references indexed in Scilit: