In a multi-stage flash distillation (MSF) plant which produces fresh water from the sea, the brineeffusing from each flash chamber does not reach the equilibrium state, although it lowers theemperature due to adiabatic pressure drop.
The author defined that the non-equilibrium temperature difference (ΔNTD) was the difference between the temperature of effusing brine (T
B) and the temperature of saturated steam (T
S) plushe boiling point elevation of the brine (ΔBPE) that is ΔNTD=T
B-(T
S+ΔBPE)
Furthermore, the author studied on equations for mass and heat transfer phenomena in a MSF plant, and obtained as the result the equations for the calculation of the optimum performance ratio,ηHOPT and the minimum production cost of fresh water, C
min.
Using the equations and parameters for the plant and the cost shown in Table-1,ηHOPT and C
min were calculated with a computer, and the effects of ΔNTD on ηHOPT and C
min were estimatmted.
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