Abstract
In this study the overall heat transfer coefficient has been evaluated during the concentration of the industrial phosphoric acid from 28% to 54% in P2O5 using a spirally finned exchanger/evaporator. Experiments have been performed on a pilot unit based on a two level factorial plan. The results obtained, show that within the experimental range, the flow rate of diluted phosphoric acid has a negligible effect on the heat transfer coefficient, while the pressure of heating steam has a predominant effect. The effects of the main operating parameters have thus been incorporated into a polynomial model expressing the overall heat transfer coefficient as a function of such parameters.