GATE 2021 ME (ME2) – Question 30
Consider adiabatic flow of air through a duct. At a given point in the duct, velocity of air is 300 m/s, temperature is 330 K and pressure is 180 kPa. Assume that the air behaves as a perfect gas with constant $c_p=1.005$ kJ/kg.K. The stagnation temperature at this point is _____ K (round off to two decimal places).
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Correct answer: 372.91 to 376.65
Explanation
For adiabatic deceleration without work, stagnation enthalpy is h₀=h+V²/2. With constant cₚ, $T_0=T+V^2/(2c_p)$.
Use cₚ=1005 J/(kg K): $T_0=330+300^2/(2\times1005)=\mathbf{374.78}$ K.