Monday, February 10, 2014

Thermodynamics Help.

Thermodynamics


Air enters an adiabatic nozzle steadily at 300 kPa, 200 degreescelcius and 30 m/s
Air leaves at 100 kPa and 173 m/s
The inlet area of the nozzle is 95 cm^2
Determine the following:
(a) the mass flow rate through the nozzle.
(b) the exit temperature of the air.
(c) the exit area of the nozzle.

The gas constant of air is

The specific heat of air at the anticipated average temperature of450 K is
a) There is only one inlet and one exit, and thus
Using the ideal gas relation, the specific volume and the mass flowrate of air are determined to be





b) We take nozzle as the system, which is a control volume sincemass crosses the boundary. The energy balance for this steady-flowsystem can be expressed in the rate form as:

Rate of net energy transfer by heat, work, and mass = = Rate of change in internal, kinetic,potential, etc. energies (which come to 0 at steady state ) =



( Here no Q, W because potential energy = 0)

 0 =

 0 =

 0 = 1.02( ( Here we need to covert m/s tokJ/kg)

0 =

C

c) The specific volume of air at the nozzle exit is :



   0.63 =



Or alternative question:

Air enters an adiabatic nozzle steadily at 300kPa, 200Degrees Celsius, and 30m/s and leaves at 100kPa and 180m/s. The inlet area of the nozzle 80cm^2. Determine the mass flow rate through the nozzle, and the exit area of the nozzle. 

Use the following steps above just substitute 80cm^2 for area one in step A. Then use that mass to determine the exit area of the nozzle. 









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