1) Nitrogen gas flows into a convergent nozzle at a pressure of 225kPa, a temper

Question

1) Nitrogen gas flows into a convergent nozzle at a pressure of 225kPa, a temperature of 440K and with a very low inlet velocity which may be assumed to be zero. The flow is accelerated and exits the nozzle at a pressure of 100kPa and a temperature of 330K.

Assuming the nozzle is insulated, with no change in height between inlet and exit,

a) What is the change in specific enthalpy of the Nitrogen ?(kJ/kg)

b) What is the velocity of the Nitrogen at the exit of the nozzle ? (m/s)

Assume a constant specific heat of N2 at constant pressure, CpN2 = 1042 J/kg K

2)

What is the thermal efficiency of a Carnot cycle heat engine operating between a hot reservoir at 350oC and a cold reservoir at 18oC ? (%) answer in percentage

3)

Explanation / Answer

1a)change in specific enthalpy=h1-h2=cp(T1-T2)=1042(440-330)=114620j/kg

b)h1-h2=v2^2/2

v2=478.79m/s

2)effeciency=1-(T2/T1)=(1-291/623)=0.5329=53.29%

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