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An ai r st andar d Ot t o cycl e has t her mal efficiency of 0.5 and the mean effective pressure of the cycle is 1000 kPa. For air, assume specific heat ratio γ = 1.4 and specific gas constant R = 0.287 kJ/kg.K. If the pressure and temperature at the beginning of the compression stroke are 100 kPa and 300 K, respectively, then the specific net work output of the cycle is ___ kJ/ kg
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- 808.77 kJ/kg
- 808.77 kJ/kg
- 709 kJ/kg
- 708.77 kJ/kg
Correct Option: C
| η = 0.5 = 1 - | ||
| (r)γ-1 |
| ∵ r = = compression ratio = | = 1 + | ||
| VC | VC |
∵ Before compression,
| Total volume, VT = | [let m = 1 kg] | |
| P |
| VT = | = | ||
| P | 100 |
VT = 0.861 m³/kg
From equation (1)
⇒ r = 5.656
| ⇒ | = 5.656 | |
| VC |
| VC = | ⇒ | = 0.152m ³/kg | |
| 5.656 |
Swept volume, VS (r – 1).VC
= 4.656 × 0.152
= 0.70877 m³ /kg
Specific net work output of cycle,
W = Pmep × VS
= 1000 × 0.70877
Wnet =708.77 kJ/kg
