Thermodynamics; Pressure and Temperature at the Nozzle inlet

1. May 7, 2012

Sara1

1. The problem statement, all variables and given/known data
CO2 gas enters a nozzle with an isentropic efficiency of 83% with a low velocity. It exits the nozzle at 110 kpa and 59K and 246m/s. Determine the pressure at the nozzle inlet assuming:

2. Relevant equations
-Constant specific heats at room temperature
-Variable specific heats

3. The attempt at a solution
I first started by using the energy balance equation of a single stream steady flow device, and simplified it to:
Q=m(h2-h1) + 1/2(V2^2)

The isentropic equation is ηNozzle= (T2a-T1)/(T2s-T1)

I am at a loss in finding the inlet temperature and pressure. I am not sure how i should start of solving this question and what method to use.

2. May 7, 2012

rude man

Anyone know what "83% isentropic efficiency" means? That 17% of the heat escapes?

3. May 7, 2012

Sara1

Isentropic Efficiency= Measures the deviation of actual processes from the corresponding isentropic ones.

Thus, for a nozzle:

0.83= Actual Kinetic Energy at Nozzle Exit/ Isentropic KE at Nozzle Exit