Page 143 - DJJ20063- Thermodynamics 1

DJJ20063- Thermodynamics 1

The plant required and the numbers referring to the state points for the Carnot cycle is

shown in Fig. 4.2.1-1 The steam at the inlet to the turbine is dry saturated. The steam

flows round the cycle and each process may be analysed using the steady flow energy

equation where changes in kinetic energy and potential energy may be neglected.

i.e. h1 + Q = h2 + W

In this statement of the equation the subscripts 1 and 2 refer to the initial and final state

points of the process; each process in the cycle can be considered in turn as follows:

Boiler:

h4 + Q41 = h1 + W41

Therefore, since W = 0,

Q451 = h1 – h4 (4.4)

Turbine:

The expansion is adiabatic (i.e. Q = 0), and isentropic (i.e. s1 = s2), and h2 can be

calculated using this latter fact. Then

h1 + Q12 = h2 + W12

 W12 = ( h1 – h2) (4.5)

Condenser:

h2 + Q23 = h3 + W23
Therefore, since W = 0

Q23 = h3 – h2

i.e. Q23 = - ( h2 – h3 )

 Heat rejected in condenser = h2 – h3 (4.6)

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