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)]. 

Duhring lines, system sodium hydroxide—water. After McCabef)... 

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. 

Figure 8.4-2. Duhring lines for aqueous solutions of sodium hydroxide.

From the known outlet concentration and pressure in the last effect, determine the boiling point in the last effect. (If a boiling-point rise is present, this can be determined from a Duhring line plot.)... 

It is also possible to get straight-line correlations with Duhring plots, which are plots of the temperature at which a substance has a certain vapor pressure versus the temperature at which a reference substance has the same vapor pressure. The principles of the preparation and use of these charts are identical to those of the Cox chart. 

Duhring s rule. Relates the vapor pressure of similar substances at different temperatures. A straight or nearly straight line results if the temperature at which a liquid exerts a particular pressure is plotted on a graph against the temperature at which some similar reference liquid exerts the same vapor pressure. Water is most frequently used as a reference liquid since its vapor pressure at various temperatures is well known. 

Figure 3.10. Duhring-type plot showing constant super saturation lines range S = 0 to 1.8) for aqueous solutions of sucrose. After Holven, 1942)...

Experimental Methods of Thermophoresis in Liquids, Fig. 6 Particle size dependence of the thermal diffusion coefficient Dt for very dilnle pofystyrene beads. FD represents the fluorescence detectirai method, and BD denotes the beam deflectimi method. Data obtained using the flutnescence detectiim method are by Duhr and Braun [2], and using the beam deflection method are by Braibanti et af. [10]. As particfe size inraeases, a finear refationship devefops betweai Dx and particfe size as shown by the solid lines... 

---