The mass transfer Graetz problem of flat-plate thermal-diffusion columns for heavy water enrichment was investigated. An orthogonal expansion technique was used to solve the laminar counter-current flat-plate thermal-diffusion column separation problems under flow-rate fraction variations and feed position. The present theoretical predictions for the degree of separation were solved based on the separation variable method. Positive and negative eigen-values are needed for the enriching and stripping sections, respectively, during the calculation procedure. The results show that the degree of separation increases with decreasing the feed flow rate and the maximum degree of separation is obtained for feed positions δ=0.5 and feed concentration CF=0.385. Moreover, the theoretical predictions are in better agreement with the experimental results than those predicted using the transport equation in the previous works.
Journal of the Taiwan Institute of Chemical Engineers 42(1), pp.50-57