660 ENGINEERING THERMODYNAMICS

dharm
\M-therm\Th13-4.pm5

Adiabatic

Adiabatic

v(m )^3

(^1) 2 (27°C) 1
4
16
p (bar)
4
3
Fig. 13.31
∴ T 3 = T 2 × 1.284 = 300 × 1.284 = 385.2 K or 112.2°C
For constant volume process 3-4,
p
T
p
T
4
4
3
3

T pT
(^4) p
43
3
16 385 2
4
==×. = 1540.8 K or 1267.8°C
For adiabatic expansion process 4-1,
T
T
p
p
4
1
4
1
(^1) 122 1
16 122
1

F
HG
I
KJ
=FHG IKJ
γ− −
γ
= 1.648
or T 1 T^4
1 648
1540 8
1 648

= 934.9 K or 661.9°C.
(i)Work done per kg of gas, W :
Heat supplied = cv (T 4 – T 3 )
= 0.75 (1540.8 – 385.2) = 866.7 kJ/kg
Heat rejected = cp (T 1 – T 2 ) = 0.92(934.9 – 300) = 584.1 kJ/kg
Work done/kg of gas, W = Heat supplied – heat rejected
= 866.7 – 584.1 = 282.6 kJ/kg = 282600 N-m/kg. (Ans.)
(ii)Efficiency of the cycle :
Efficiency, η = Work done
Heat supplied
=282 6
866 7
= 0.326 or 32.6%. (Ans.)

13.9. Ericsson Cycle

It is so named as it was invented by Ericsson. Fig. 13.32 shows p-v diagram of this cycle.