Calculation Methods for Single-Effect Evaporators

The basic equation for solving for the capacity of a single-effect evaporator is Eq. (8.2-1), which can be written as 

Since the vapor V is in equilibrium with the liquid L, the temperatures of vapor and liquid are the same. Also, the pressure Pj is the saturation vapor pressure of the liquid of composition at its boiling point Tj. (This assumes no boiling-point rise.) 

For the material balance since we are at steady state, the rate of mass in = rate of mass out. Then, for a total balance, 

For the heat balance, since the total heat entering = total heat leaving, heat in feed -l- heat in steam 

This assumes no heat lost by radiation or convection. Substituting into Eq. (8.4-5), 

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