Evaporation Duhring lines

Single-Effect Evaporators The heat requirements of a singleeffect continuous evaporator can be calculated by the usual methods of stoichiometry. If enthalpy data or specific heat and heat-of-solution data are not available, the heat requirement can be estimated as the sum of the heat needed to raise the feed from feed to product temperature and the heat required to evaporate the water. The latent heat of water is taken at the vapor-head pressure instead of at the product temperature in order to compensate partially for any heat of solution. If sufficient vapor-pressure data are available for the solution, methods are available to calculate the true latent heat from the slope of the Duhring line [Othmer, Ind. Eng. Chem., 32, 841 (1940)]. 

When evaporation-related balance simulation is involved, Duhring lines of the material solntion to acconnt for boiling point rise are reqnired as input in addition to the specific heat of the bone dry material. 

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