Consider a rankine cycle, where steam enters the turbine @ 5 mpa, 500 °c and exits at 12.35 kpa. the cycle produce 10,000 kw of electricity. determine the cycle efficiency and the steam amount needed. (in)

cycle efficiency: 0.11

steam amount needed: 8.327  kg/s

Explanation:

Points 1,2,3 and 4 are depicted in first figure attached. h means enthalpy and s means entropy .

Assumption

Interpolation to get (see second figure)

p (MPa)h (kJ/kg)

4         3445.3  

5        

6         3422.2

(3445.3 - 3422.2)/(4 - 6) = (3445.3 - )/(4 - 5)

In a similar way is computed as 6.9852 kJ/(kg K)

At 12.35 kPa, i. e., 0.1235 bar (see third figure): = 0.6922; = 8.093; = 205.82 ; = 2590.575 (again from interpolation, units omitted)

Quality (x) =

Enthalpy =

In a similar way is computed as 205.83 kJ/kg.

Point 4 is computed as saturated liquid at 5 MPa; then, = 1154.2 kJ/kg (see fourth figure).  

Efficiency is calculated as

Energy balance at turbine gives

diy

explanation:

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explanation: