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In a gas turbine, hot combustion products with the specific heats cp = 0.98 kJ/kgK, and cv = 0.7538 kJ/kgK enters the turbine at 20 bar, 1500 K and exits at 1 bar. The isentropic efficiency of the turbine is 0.94. The work developed by the turbine per kg of gas flow is
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- 689.64 kJ/kg
- 794.66 kJ/kg
- 1009.72 kJ/kg
- 1312.00 kJ/kg
Correct Option: A
Given,, c p = 0.98 kJ/kg k.
cp = 0.7538 kJ/kg k
P3 = 20 bar = 20 × 105 N/m2
T3 = 1500 K
P4 = 1 bar = 1 × 105 N/m
hturbine = 0.94
For process, 3 – 4s 
Where,
| q = | = | = 1.3 | ||
| cv | 0.7538 |
⇒ T4s = 751.37 K
Now turbine efficiency,
| ηt = | T3 - T4s |
| ⇒ 0.94 = | 1500 - 751.37 |
∴ T4 = 796.3 K
Now turbine work,
Wt = T3 - T4
= cp (T3 - T4)
= 0.08(1500 – 796.3)
= 698.64 kJ/kg
