A turbine is operating at steady state in an ideal Rankine v

A turbine is operating at steady state in an ideal Rankine vapor power cycle. Steam enters the turbine at 25 bars and 500 degreeC. Steam leaves the turbine at 0.5 bar. The steam mass flow rate through the turbine is 15 kg/s. Determine the work produced by the turbine. If the thermal efficiency of the cycle is 40%, what would be the heat input to the boiler?

Solution

at 25 bar 500 C

h1 = 3460 kJ/kg

s1 = 7.33 kJ/kgK

at 0.5 bar exit we have s2 = s1 = 7.33 kJ/kgK

from steam stables we get

h2 = 2550 kJ/kg

exit quality = 0.96

Work done by turbine   = mass flow rate * (h1 - h2)

                                  = 15 * ( 3460 - 2550)   = 13.65 MW

Heat Input to boiler = work done by turbine / efficiency

                             = 13.65 / 0.4   = 34.125 MW