Where necessary, assume air as an ideal gas and consider R = 287J/(kg.K), Cp = 1005 J/(kg.K), Cv = 718 J/(kg.K). A nozzle is a device that is used to increase the velocity of a fluid by varying the cross-sectional area. At the last section of a jet engine (Fig Q1.a, section 5), air with a mass flow rate of 50 kg/s at a pressure of 500 kPa and a temperature of 600 K enters a nozzle with an inlet cross-sectional area of 5 m2. The exit area of the nozzle is 20% of its inlet area. The air leaves the nozzle at a velocity of 300 m/s. The nozzle is not well-insulated and during this process, 5 kJ/kg heat is lost. (i) In analysing this nozzle using the 1st law of thermodynamics, the change in which type of energy is negligible? (ii) Determine the density and velocity of the air entering the nozzle. (iii) Calculate the density of the air as it leaves the nozzle.
Where necessary, assume air as an ideal gas and consider R = 287J/(kg.K), Cp = 1005 J/(kg.K), Cv = 718 J/(kg.K).
A nozzle is a device that is used to increase the velocity of a fluid by varying the cross-sectional area. At the last section of a jet engine (Fig Q1.a, section 5), air with a mass flow rate of 50 kg/s at a pressure of 500 kPa and a temperature of 600 K enters a nozzle with an inlet cross-sectional area of 5 m2. The exit area of the nozzle is 20% of its inlet area. The air leaves the nozzle at a velocity of 300 m/s. The nozzle is not well-insulated and during
this process, 5 kJ/kg heat is lost.
(i) In analysing this nozzle using the 1st law of
the change in which type of energy is negligible?
(ii) Determine the density and velocity of the air entering the
nozzle.
(iii) Calculate the density of the air as it leaves the nozzle.
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