Question 5.17: (a) Show that, when critical pressure ratio occurs, the velo...
(a) Show that, when critical pressure ratio occurs, the velocity of a compressible fluid at the exit of a convergent nozzle is given by
C_{2} = \sqrt{ \frac{2}{γ + 1} . a_{1}}where a_{1} is the sonic velocity corresponding to the intial conditions. Assume critical pressure
ratio = (\frac{2}{γ + 1}) ^{\frac{γ }{γ + 1}} , where γ is the adiabatic index.
(b) State the factors on which nozzle efficiency depends.
(c) Determine the throat and exit height of a Delaval nozzle to discharge 27 kg of a perfect gas per minute. The inlet and exit pressures are 480 kPa and 138 kPa respectively. Initial temperature of the gas is 535°C. Nozzle efficiency is 90% and frictional losses occur only after the throat. The molecular weight of the gas is 29 and its adiabatic index = 1.4. Assume square cross-section of the nozzle. (AMIE Summer, 1998)
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