In a preliminary design of a power plant water is chosen as

In a preliminary design of a power plant, water is chosen as the working fluid and it is determined that the turbine inlet temperature may not exceed 520 degrees Celcius. Based on expected cooling water temperatures, the condenser is to operate at a pressure of 0.06 bar. Determine the steam generator pressure required if the isentropic efficiency is 80% and the quality of steam at the turbine exit must be at least 90%.

Solution

Here the temperature required to generate can be found using mollier chart

First since the out let pressure is .06 bar and stream dryness is 90 %

So entrophy at this point is 7.5 kJ/kg K

since entropy is contant at condensation and 80 % efficiency is taken so 80% entropy is

0.8 * 7.5=6 kJ /kg K

for entropy 6 kJ/kg K draw a vertical straight line towards y axis

it will intersect at temperature curve at 520 C

at that point the respective pressure can be obtained

The pressure is 250 Bar