TITLE.PM5

662 ENGINEERING THERMODYNAMICS

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The various operations are as follows :
Operation 1-2. The air is compressed isentropically from the lower pressure p 1 to the
upper pressure p 2 , the temperature rising from T 1 to T 2. No heat flow occurs.
Operation 2-3. Heat flows into the system increasing the volume from V 2 to V 3 and tem-
perature from T 2 to T 3 whilst the pressure remains constant at p 2. Heat received = mcp (T 3 – T 2 ).
Operation 3-4. The air is expanded isentropically from p 2 to p 1 , the temperature falling
from T 3 to T 4. No heat flow occurs.
Operation 4-1. Heat is rejected from the system as the volume decreases from V 4 to V 1 and
the temperature from T 4 to T 1 whilst the pressure remains constant at p 1. Heat rejected = mcp
(T 4 – T 1 ).

ηair-standard= Work done

Heat received

= Heat received/cycle Heat rejected/cycle

Heat received/cycle

−

=

mc T T mc T T

mc T T

p p

p

()()

()

32 41

32

−− −

− = 1 –

TT

TT

41

32

−

−

Work

Heater

HE-1

HE-2

CT

Cooler

4

2 3

1

C = Compressor T = Turbine

(a)

(b)

p

V

2 3

14

pV = Cγ

(c)

T

s

p = C

3

4

(^2) p = C
1
Fig. 13.33. Brayton cycle : (a) Basic components of a gas turbine power plant
(b) p-V diagram (c) T-s diagram.