Bubble Point Calculation : Bubble point of a system is the temperature at which liquid mixture begins to vaporize. Step 1 Obtain process parameters Get liquid mixture molar composition ( Xi ) and Pressure (P) of the system. Obtain equilibrium ratios ( Ki ) for the components. Ki can be calculated from Antoine equation. Yi = Ki * Xi Ki (T) = ( e A - B / (T + C) ) / P where, Yi : Vapor phase molar composition in equilibrium with liquid A, B, C : Antoine equation constants Step 2 Calculate Bubble Point At Bubble Point temperature summation of vapor phase molar fraction should be 1. Σ Ki(T).Xi = 1 Above equation can be solved iteratively using Newton Raphson method. An intial temperature T is assumed. Function F(T) is calculated as following. F(T) = Σ Ki(T).Xi - 1 Deriavative of F(T) is calculated as following. F(T) = Σ ( B.Ki(T) / (T+C)² ).Xi New estimate of temperature is calculated as following. T New = T - F(T)/F(T) Function F(T) and F(T) are calcualted based on new temperature and this process is repeated till there is negligible difference in between T and TNew. Bubble point temperature thus obtained is then used to calculate vapor phase composition based on above equations.
Posted on: Sun, 05 Oct 2014 21:35:52 +0000