13
For the following four systems, define a control volume, state if the system is steady or unsteady, open or
closed, constant volume or changing volume, constant fluid density or changing fluid density. Also,
identify all heat transfer, energy flows, a
517 A tank of volume 530 cm3 contains a twophase mixture of R134a at 12oC. The mass of liquid present is
four times the mass of vapor.
a. Find the total mass of R134a in the tank.
b. Find the volume of liquid present.
Approach:
Express quality as a ra
101
Air at 23 C, 100 kPa with a freestream velocity of 100 km/hr flows along a flat plate. How long does the
plate have to be to obtain a boundary layer thickness of 8 mm?
Approach:
For the distance x from the leading edge to where the
boundary layer th
436
Air at 20oC and 101 kPa enters a passage between two printed circuit boards inside a desktop computer.
One board contains 9 chips each dissipating 2 W and 5 chips each dissipating 1.3 W. No heat enters the
passage from the other card. If the exit tem
329
An aluminum wire 2.5 m long conducts 12 A with an imposed voltage of 1.5 V. The wire, which
has a diameter of 2.4 mm, is covered with a layer of insulation 2 mm thick. The thermal
conductivity of the insulation is 0.15 W/moC. Air at 40oC flows over t
337
A novelty drink container is made of plastic in the shape of a sphere. The container has an outside
diameter of 6.5 cm and a wall thickness of 2.5 mm. The container is initially filled with soda and
crushed ice. The ice occupies 30% of the volume of
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3
Density = 1025kg/m
A
F
5.1m
A
CG
P
B
Gate
B
2.2m
3.6m
Bx
By
Hinge
2.85m
Solution:
Sp wt of sea water ( ) = 1025x9.81 = 10055 N/m3
Area (A) = 1.2x3.6 = 4.32 m2
Location of CG ( ) = (5.12.2)+2.2/2 = 4.0m
a) Resultant force on gate (F)
45
At great ocean depths, the hydrostatic pressure is very high. Suppose that seawater density varies with
pressure according to
P = C1 ln + C2
o
where C1 = 2.24 x 109 Pa, C2 = 1 x 105 Pa, and o =1024 kg/m3. Assume this relation holds at any depth, z
432
In a home, air infiltrates from the outside through cracks around doors and windows. Consider a residence
where the total length of cracks is 62 m and the total internal volume is 210 m3. Due to the wind, 9.4 x 105
kg/s of air enters per meter of cr
MAE 24O  Summer 2015
Exam 2
car+ian
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Which of the following relationships between pressure, velocity and temperature accurately
Cescr!bes the
Name:
ANtrrtER t(E"V
ASU ID:
MAE 24A
 Summer 2016
Exam lAGAZ?:A!6
Section
1.
I

Multiple Choice / TrueFalse cfw_40 Points
A polytropic process is one for which PVn = conster$; an example process for which n = 0
would best be described as:
A.
@
C.
D.
66
Steam enters a diffuser at 250oC and 50 kPa and exits at 300oC and 150 kPa. The diameter at the entrance
is 0.25 m and the diameter at the exit is 0.5m. If the mass flow rate is 9.4 kg/s, find the heat transfer to the
surroundings.
Approach:
Use the f