This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: MEEN 315—Spring 2009, Exam 2 Name I g E ‘ Section Number I. Multiple choice problems worth 2 pts each. Circle the answer that is the most appropriate or
closest (numerically) to your answer. 1. What is the compressibility factor at the critical point? A) o 0.3 C) 0.75 D) Not enough information is given. , T
HQ: 2;!) {#22: ___C__V_Z_’ :4 :> 2*;OL'5' 2. The Van der Waals equation of state, generally speaking, provides a better prediction for the
properties of real gases compared with idea gas law because it considers molecular attraction forces and volume occupied by the molecules themselves B) structure variation of molecules as function of temperature and volume occupied by the
molecules themselves C) structure variation of molecules as function of temperature and molecular attraction forces D) structure variation of molecules as function of temperature and dipole force among
molecules due to the polarization of molecular structures. MEEN 315—Spring 2009, Exam 2 Name Section Number 3. A closed system operates through one complete cycle with all properties returning to their initial
condition, and net work is done on the system. After one cycle, the system A) has net heat gain (3:9 has net heat loss C) is adiabatic D) has net temperature gain 6) Wzaoc— O 5?: W W th‘: Wm?!)
Wml )5 naagthua) We QM [5 MiaQJLIVEJ "—5 A937— 4. The property which Is defined as the energy required to raise the temperature of a unit mass of
a substance by one degree is known as A) enthalpy ‘ B) gas constant © specific heat D) internal energy 5. Estimate the constant pressure specific heat of R134a vapor in Btu/Ibm°F at 90 psia and 90 °F: CiD ..., E? .. I909F~50¢ “1 02565:};
W M
723 =: ?O°l= 6. Select a device from the following list to accelerate a fluid and lower its pressure.
A) Throttle B) Turbine @ Nozzle D) Heat Exchanger MEEN SIS—Spring 2009, Exam 2 Name Section Number 7. What would be the magnitude of the work for the process shown in the pV diagram below? , P
1687.5kJ (“38)
I 150
B) 1125kJ 2
C) 2250kJ
75
o) 750kJ 1
5 20 V(m‘°’)
wngawr lim(\/r)/el=flSOwL'ZSﬁwzowsM (A: W 3
{.3 §\ 33.4 f Kg???” 8. Liquid water flows through a nozzle with an inlet area of 5 cm2 and an inlet velocity of 10 m/s. If
the outlet velocity is 50 m/s, what is the outlet area in cmz? A) 100 C) 10 B) 50 @1 MEEN 315~5pring 2009, Exam 2 Name
Section Number
9. Select the device below where there is a pressure increase from inlet to exit:
A) Throttle @ Diffuser B) Turbine D) Nozzle 10. Which of the following statements for throttling valves is wrong?
A) involves negligible kinetic energy changes
causes temperature decreases for ideal gases
C) causes pressure decrease for incompressible fluid D) causes temperature increase for incompressible fluid MEEN 315—Spring 2009, Exam 2 ' Name Section Number
ll. Four work—out problems valued as noted. 1) A container of volume 2.5 ft3 contains water vapor at at 1120 °F and 2500 psia.
A) Determine the specific volume from the steam tables. (4 pts)
B) Calculate the specific volume treating it as an ideal gas and determine the error in relation to the tabular value. (8 pts)
C) Use the compressibility factor to determine the specific volume and determine the error in
relation to the tabular value 8 pts) C) 712“ 0129+4EODQ': lréé PR: W ; Q,75
Hagen MEEN 315—Spring 2009, Exam 2 Name Section Number 2. A piston cylinder assembly contains 7 kg 03f air which undergoes a polytropic process (n: 1. 4) M2) 2.
from state 1 where P1: 300 kPa and V1 — 2 m3 to state 2 where V2: 0.5 V1. Neglect kinetic and 54
potential energy effects and assume ideal gas behavior Lo/ A) Determine P2 in kPa (5 pts) B) Draw the process on a Pv diagram (5 pts) C) Determine the work (5 pts) D) Determine the heat transfer assuming constant specific heat (5 pts) “4
A) 8%1‘4: fat/1,14 ) J: : Pl<v:)t4= 300k”; (bigR) =(7WZJCIQLl
5);” F We ‘T2. 2: 7“ “a M2 76:6 7
M Q 7I§Q$WQW WA > Cry 0.7a???
‘=. M 2 30£9W2X2LMJ a ZWK MR 7% 024.2 ‘70 104 m3 kﬁK V
 é ._, 5
Q W+MCVCTz7UHr4301c3t7/§072lé—"AW‘Z4 20K =l 055143 MEEN 315—Spring 2009, Exam 2 Name Section Number 3. An adiabatic air compressor is powered by a steam turbine that also drives a generator. Steam
enters the turbine at 10 MPa and 500 °C at a rate of 25 kg/s and exits at 20 kPa and a quality of 0.9.
The turbine loses heat from its surface at the.» rate of 10% of the turbine’s total work output. Air
enters the compressor at 100 kPa and 300 K at a rate of 10 kg/s and exits at
1 MPa and 600 K. Determine A) power in kW required by the compressor. (7 pts) B) power in kW produced by the turbine to drive both the compressor and generator. (8 pts) C) electrical power in kW produced by the generator if the generator is 97% efficient. (5 pts) 1 MPa 10 MPa
@ I 600K 500 °C ﬂ@ l:> Welec ' D ' ° 3 l3 W5 _:
A) [gtw : m (iv/$1): 19§(6©7L~ amzeyﬁ 5065 kW 56 £5 col/K10"
a) mwzmdﬂ)‘, chem/5 com/mmm.) .
o . c W [(—7 1
W‘= 1‘1 k »€ ~ g : I? Mmél : 261.4ﬂ+o.4(2357.5)f =2575— .
M 3 4) 2 A 43 {7 Loki/é, k? g ‘ MEEN SIS—Spring 2009, Exam 2 Name Section Number
4. R134a enters an adiabatic condenser operating at steadystate at 140 psia and 200 °F and is
condensed to saturated liquid at 140 psia on the outside of tubes through which cooling water
flows. The cooling water enters at 80 °F and increases in temperature by 15 °F in the condenser.
The cooling water flows at a rate of 24 gal/min. Determine:
A) mass flow rate of R134a in lbm/min (10 pts)
B) heat transfer rate in Btu/hr from the refrigerant to the water (10 pts) H20 “26)
. z 24 241 35 315¥f 4% ,4, 5 2004434
my” vmn 2544341 @iozeowéf WM 11 ...
View
Full Document
 Spring '07
 RAMUSSEN

Click to edit the document details