Assignment 2 Solutions 2009

The feedback yields one addit ional relationship

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Unformatted text preview: o affect one variable by manipulat ing another variable, thus providing one addit ional relationship and reducing F to 0. For example, it might be advantageous to control the exit concentration of one o f the species by manipulat ing the velocit y (or the flow through) u . The feedback yields one addit ional relationship between two variables, 0 thus reducing the degrees of freedo m to zero. 2. A binary mixture at the saturation po int is fed to a single­stage flash unit (Figure 1) where the mixture is heated at an unknown rate (Q). The feed flow and feed mo le fractions are known and may vary wit h t ime. Assume that x represents the mo le fract ion of the more volat ile co mponent (e.g. xF is the mo le fract ion of the more volat ile component in the feed stream) and the mo lar heat of vaporizat ion is the same for both components. Flow rate is given in mo les per unit t ime. H represents the mo lar liquid ho ldup. Figure 1: Schemat ic o f a flash unit. The equilibrium relat ionship is given by: x D = K (T , P x B ) Where K is the equilibrium constant a. Derive the modeling equations for this system. State your assumpt ions clearly...
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