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AAI JE (Technical) Official Paper 2018

Option 3 : 34.1%

ST 2: Strength of materials

2149

15 Questions
15 Marks
15 Mins

__ Concept__:

Indicated thermal efficiency:

\(\eta_{ith} = \frac{Indicated\ Power}{Heat\ added\ per\ second}\)

Heat added per second HA/s = \(Ì‡ m_f\ Ã— \) (C.V.)f, where C.V. = Calorific value of fuel

__Calculation:__

__Given:__

VÌ‡_{f} = 8 lit/hr = \(\frac{8\;Ã—\;10^{-3}}{3600}\)m^{3}/sec, CV = 44000 kJ/kg, SG = 0.75, IP = 25 kW

mÌ‡f = ρVÌ‡f = 0.75 × 1000 × \(\frac{8\;Ã—\;10^{-3}}{3600}\) kg/sec.

\(\eta_{ith} = \frac{Indicated\ Power}{Heat\ added\ per\ second}\)

\(\eta_{ith}= \frac{{25 Ã— 60 Ã— 60}}{{\left( {8 Ã— {{10}^{ - 3}} Ã— 0.75 Ã— 1000} \right) Ã— 44000}} Ã— 100 = 34.1\%\)