In a steam power plant operating on the Rankine cycle, steam enters the turbine at 4 MPa, 350ºC and exits at a pressure of 15 kPa. Then it enters the condenser and exits as saturated water. Next, a pump feeds back the water to the boiler. The adiabatic efficiency of the turbine is 90%. The thermodynamic states of water and steam are given in the table. State h(kJ kg-1) s(kJ kg-1K-1) v(m3kg-1) Steam: 4MPa,350°C 3092.5 6.5821 0.06645 Water : 15 kPa hf hg sf sg vf vg 225.94 2599.1 0.7549 8.0085 0.001014 10.02 h is specific enthalpy, s is specific entropy and v the specific volume; subscripts f and g denote saturated liquid state and saturated vapour state.
The net work output (kJ kg-1) of the cycle is
860
Isentropic exit quality is (6.5821−0.7549)/(8.0085−0.7549)≈0.80335. Its enthalpy is about 2132.4 kJ/kg. Actual turbine work is 0.9(3092.5−2132.4)≈864.1 kJ/kg. Subtracting pump work 0.001014(4000−15)=4.04 gives net work about 860 kJ/kg.
Important Questions from Rankine Cycle
In a cross compound steam engine _____.
The concept of regeneration is used in which cycles?
The Rankine cycle will approach to Carnot cycle if
In order to increase the efficiency of Rankine cycle, Which one of the following statement is incorrect?
Which combination of the following statements is correct? The incorporation of a reheater in a steam power plant
(P) Always increase thermal efficiency
(Q) Always increase the dryness fraction at the condensed inlet
(R) Increase the mean temperature of heat addition
(S) Always increases specific work output
