Thermodynamics — rankine cycles Essay Example

The step involved in simple cycle are as shown in the figure 1

Thermodynamics - rankine cycles

  1. Ideal simple cycle

At 170 bar and 600Thermodynamics - rankine cycles 1 we have the following results

160 bar, h =3573 s=6.64

180bar h=3556 s=6.57

Calculating h4Thermodynamics - rankine cycles 2

S4=6.64-0.5(0.64-6.57)

Calculating h5

At 0.065bar

Tempe=36.15Thermodynamics - rankine cycles 3 hf=151.5 hg=2567 sf=0.521 sg=8.331

Thermodynamics - rankine cycles 4

Therefore Thermodynamics - rankine cycles 5

Hence Thermodynamics - rankine cycles 6

Now work Thermodynamics - rankine cycles 7

Thermodynamics - rankine cycles 8

Thermodynamics - rankine cycles 9

Thermodynamics - rankine cycles 10

Net work outputThermodynamics - rankine cycles 11

Heat input =Thermodynamics - rankine cycles 12

But Thermodynamics - rankine cycles 13

Thermodynamics - rankine cycles 14

Thermodynamics - rankine cycles 15

Thermodynamics - rankine cycles 16

Thermodynamics - rankine cycles 17

Thermodynamics - rankine cycles 18

Efficiency Thermodynamics - rankine cycles 19

  1. With isentropic efficiency

At 90% turbine efficiencyThermodynamics - rankine cycles 20

At 85% pump efficiency Thermodynamics - rankine cycles 21

Hence net work output=1385.18-19.98

Heat input Thermodynamics - rankine cycles 22

But Thermodynamics - rankine cycles 23

Thermodynamics - rankine cycles 24

New efficiency Thermodynamics - rankine cycles 25

Reheat cycle

The reheat cycle is as shown in figure 2

Thermodynamics - rankine cycles 26

  1. Ideal reheat cycle

Just as in the ideal simple cycle we have

At 170 bar and 600Thermodynamics - rankine cycles 27 we have the following results

160 bar, h =3573 s=6.64

180bar h=3556 s=6.57

Calculating h4Thermodynamics - rankine cycles 28

S4=6.64-0.5(0.64-6.57)

Calculating h5

Tempe=212.4Thermodynamics - rankine cycles 29 hf=908.8 hg=2800 sf=2.447 sg=6.341

Thermodynamics - rankine cycles 30

Hence Thermodynamics - rankine cycles 31

Thermodynamics - rankine cycles 32

As 6 and 5 are on the same isobar of 20 bar

From tables we have h6=3690kj/kg s6=7.702

At P =0.065bar

Tempe=36.15Thermodynamics - rankine cycles 33 hf=151.5 hg=2567 sf=0.521 sg=8.331

S6=s7=7.0702

The quality of steam at 7

Thermodynamics - rankine cycles 34

Hence Thermodynamics - rankine cycles 35

Thermodynamics - rankine cycles 36

Net work output

Thermodynamics - rankine cycles 37

Thermodynamics - rankine cycles 38

Thermodynamics - rankine cycles 39

Heat input =Thermodynamics - rankine cycles 40

Thermodynamics - rankine cycles 41

Thermodynamics - rankine cycles 42

Thermodynamics - rankine cycles 43

Efficiency Thermodynamics - rankine cycles 44

  1. Reheat cycle with isentropic efficiencies

At 90% turbine efficiencyThermodynamics - rankine cycles 45

Thermodynamics - rankine cycles 46

At 85% pump efficiency Thermodynamics - rankine cycles 47

Hence net work output w=742.05+1193.22-19.98=1915.29

Efficiency Thermodynamics - rankine cycles 48