Exam 3:
1—Air in a Nozzle (30%)d.cd-p.aih
Air with a mass flow rate of 5 lb/s enters a horizontal nozzle at a steady state at T1=800oR and 50 lbf/in2 with
velocity 10 ft/s(h1=191.81 Btu/lb). The exit T2 = 570oR and velocity 1510 ft/s (h2=136.26 Btu/lb). There is
heat loss from the nozzle walls: Q (Btu/lb). (a) What is the specific volume of air v1 (ft/lb) at the inlet? (b)
find the inlet area (ft2). (c) the velocity heads V12/2 and V22/2 (Btu/lbm) at inlet and outlet. (d) Use the
energy equation to find the heat loss Q (Btu/lbm). Air is an ideal gas.
#2—Steam Turbine (30%)
d.dg-p.aih
Steam enters a turbine operating at steady state with a mass flow 10 kg/min, a specific enthalpy 3100 kJ/kg,
and a velocity of 30 m/s. At the exit, the enthalpy is 2300 kJ/kg, velocity 45 m/s. The elevation of the inlet is
3m higher than the exit. Heat transferred away from the turbine is 1.1 kJ/kg of stream flow. Let g = 9.81
m/s2. Find the velocity and elevation heads (in kJ/kg) V12/2 , V22/2 , and g(z1-z2); and work output Ws from
turbine in kW.
#3—Velocity of Sound (40%)
Venetian atmosphere is composed mostly of CO2 (96.5%). We assume it to be 100% CO2. The pressure P is
93 bar, and temperature T is 740K. CO2 gas obeying the Redlich-Kwong (RK) equation of state
P
RT
a

v b
T v (v  b )
where R = gas constant = 0.08314 m3.bar/(kmol.K), a = 64.43 bar.sqrt(K).(m3/kmol)2, b = 0.02963 m3/kmol.
v = molar volume = 0.654 (m3/kmol). (a) Find the velocity of sound c (m/s) in the Venetian atmosphere
(using RK equation). (b) Find the velocity of sound if the atmosphere were an ideal gas: P v = RT!
2  C  P 

c 2  v  p 
where Cp/Cv = 1.36. CO2 has MW = 44.
C

v
T
 v 