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Q1. (a) Explain the term choked flow with reference to a convergent nozzle. (4)

(b) Air leaks from a large pressure vessel to the surroundings which are at a pressure of 1.00 bar. The passage through which the air leaks may be considered as a convergent nozzle with exit area 0.5 mm², and the flow within the passage may be assumed isentropic. The temperature in the vessel may be assumed constant at 28°C.

Determine the mass flow rate when the pressure in the vessel is:

(i) 2.5 bar; (6)

(ii) 1.5 bar. (6)

Note: For air, g = 1.4 and R = 0.287 kJ/kg K

p_c = p_o × [2/(γ + 1)]^γ/γ-1; a = √γRT