The effect of column number on the enrichment of heavy water from water–isotope mixture in the countercurrent-flow Frazier scheme with total sum of column heights L fixed, has been investigated. The equations, which may be employed to predict the optimal column numbers for maximum performances, have been derived. Considerable improvement in removal rate is obtainable if the scheme is constructed with the optimal column number of thermal diffusion columns, especially for larger flow rate with smaller L, or smaller flow rate with larger L.
