## Transcribed Text

1. Which of the following dimensionless numbers would best be described as the ratio of buoyant
forces to Viscous forces in the case of natural convection?
Nu
None of the above
F190;”?
re
m
2. Which of the following dimensionless numbers would best be described as the ratio of the
momentum diffusivity to the mass diffusivity?
A. Re
B. Sc
C. Nu
D. Sh
E. None of the above
3. Which of the following dimensionless numbers would best be described as the ratio of the
convective heat transfer to conductive heat transfer to a surface in a ﬂuid?
A. Re
B. Sc
C. Nu
D. Sh
E. None of the above
4. Which of the following dimensionless numbers would best be described as the ratio of the
inertial forces to viscous forces in a ﬂow situation?
A. Re
B. Sc
C. Nu
D. Sh
E. None of the above
5. The following equation shows a simpliﬁed version of the mechanical energy balance:
2 3 p
L+gzz+ﬁ = V—;—+g2,+'-L]
2 1’1 - Pi
Which of the following IS NOT an assumpti
energy balance? ‘
A. The system being analyze
daries.
B bT‘h‘exfe is no heat exchange across the system boundary.
C. There is no shaft work done on or bythi‘seystem.
D. Viscous dissipation of energy is negligi .
E. None of the above.
on that must be made in deriving this form of the
d only contains one entrance and one exit for ﬂow across its
Mir
For problems 7-10. you are given the pump curve and system curve Sit0\\l‘t on the next pages in
Figure l for the pumping system shown schematically in the ﬁgure below. The air and lake
rcivnperature are 25_ ‘fC and pump sits with its intake submerged at the surface of the lake and
With no_suction piping. droning water directly into the pump. The discharge linc from the
pump climbs up a hill where it empties its water into the open air which subsequently falls into
another holding pond. The dark solid grcy cunt: shows what the head loss in the piping S\ stem
is as a function of ﬂowralc. ‘
6. From the data given on the '
. ‘ pump curve and system curve, how far in elevation above the lak
whe/r: [:13ng sits is the discharge point from the piping system? C
. eet
B. 200 feet
C. 300 feet
D. 350 feet
E. None of the above
7 101 “19111010" POWex line depicted as the dashed 11115 "131'de A 0 l the €113ng l “hat 0101
power does this 1 ne represent ’
A. 300 horsepower
B. 310 horsepower
C. 450 horsepower
D. 700 horsepower
E. None of the above
8, If
wailing: [1:15:51 for the pumv operates at 2000 rpm, What ﬂow rate ofwater will be Pumped
2400 gpm
2550 gpm
2800 gpm
3050 gpm
3300 gpm
noon?
Name: ,7 7/ 7777 't/ d
_ , - . ~ we
Going back to Problem #9, in the case where the inlet velocuy t0 the pump ‘5 10:1 151:; loss
10' assume that ﬂow into the suction inlet to the pump is turbulent, what is the actu -
caused by the water entering the suction port on the pump rounded to the nearest foot?
A. 0 it
B. 1 it
C, 28 h
D. 55 it
E. None of the above
5/18
ii
11. You are processing solid aluminum spheres in which you are czooling them in an oil bat: it the
convective heat transfer coefﬁcient in the oil bath is 20 lW/in K] and the thermal con :c lVl y
of aluminum is 200 [W/m K]. how large must the diameter of the altiminum spsc: '83:;
before you can no longer treat it using the lumped temperature assumption in whic t e in
temperature is assumed to be uniform.
A. 1 m
B. 3 m
C. 6 m
D. 10 m
E. None of the above
two ﬂat plates of the same surface area as shown in
h other centered with one another and suspended
o be black bodies at a temperature off) K.
be considered to be black bodies and are insulated on all Sides
' u from the insulated
except their front faces that View each other so that no heat transfer occ rs
sides One black body plate is heated electrically to a temperature Ti. In the other chamber.
' t ’ ' urev body \\iih an
one plate is heated electrically to a temperature T3 and the other pla e is a g ‘
emissivity e, If T1 = T; at steady-state which of the following would be true about the
temperature of the plates that are not electrically heated?
A. T2
B. T; = T4
C. T; > T4 .
D. Can not be deterinined
12. You have two different chambers in which
the diagrams face each other. They face eac
inside an enclosures whose surfaces can be assumed t
In one chamber, both plates can
Qelectricrty
Qelectricitv
Fool x .305 = mun 30"“ 0'3- N s ' .
m x 25.4 = Minimum .. z ._
cm x .227 . cum mm 2-00 1050 “In“ E 2
GPM x 3.735 = UNIS/MIN“. Y: E
HP x .146 a Kw SINGLE VOLUTE MOUNTING CONFIG; cc. VM. F. VF. EM, vc
5n. 1|.5 M) 6FT. (1.8 Ml
698. FT. (2.! M)
11 Pr. (3.4 M)
.
:72
' 7t
8
E
2
ul
3:
9
2
<
z
>
1009
2‘
'5
._
8
n
2
§
Head Loss in Piping System (FEET)
§
é
iv o 500 1000 i500 2000 2500 3000 3500 4000
CAPAC|TY us. GALLONS PER MINUTE
1‘” 200 30° 400 500 000 700 800 900
CUBlC METERS FER HOUR
Cornell Pump Company - Portland. Oregon 6NHT819 - VARIOUS RPM
VAS ISLHNQ
W3 7/!"
I For pmblems 13 a 15, you are working in a plant and need to analyze the pressure drop in a pipe
ﬂow application. One of the plant operators has measured the pressure drop in the pipe at several
different ﬂow velocities and at several points down the length of the pipe. You don‘t have access
to your engineering books and need to do a quick back of the envelope calculation to determine
how correlate this pressure drop data with the pipe length and the ﬂow velocity. The variables
involved in the problem are the pressure drop across the length of pipe (AP), the velocity of the
ﬂowmg liquid in the pipe (v), the length of the pipe (L). the diameter of the pipe (0). the dénSiIY 0f
the ﬂuid (p), and the viscosity of the ﬂuid Lu). Recall that the units of viscosity are [Mass/(Length
Time)]. Answer the following questions:
13. How/\mzlmy different dimensionless groups can be formed in this analysis?
B. 2
C. 3
D. 4
E. None of the above
14. If you want to correlate the data on pressure dro ‘ ' ' ‘
_ ‘ . p in the pipe With pipe length and flow
velocuyz which of the variables should you choose as “core variables" that appear in all
of the dimensionless groups?
Pt [1’ D
AP, L, v
4P4» #1
AP, D, v
None of the above
none?
15. If you were to form a dimensionless group involving AP ,pt [1, D, which of the following could
be that dimensionless group? “
A. LB"
F
B. L?”
it
02
C. M p
[1
APDZ
D. ,"
E. None ofthe above
gym Name: ﬁ/ .777 sissﬁ.‘
16. which of the following statements is true about overall heat transfer coefﬁctents for 3. ca
exchanger?
A. The overall heat transfer coefﬁcient based on the outside tube surface area is always
smaller than the overall heat transfer coefﬁcient based on the inside tube surfa.ce area.
B. The overall heat transfer coefficient can simply be complucd as the average 01 the
convective heat transfer coefﬁcients for the ﬂuid inside the tubes and for the ﬂuid
outside the tubes. .
C. If the thermal Conductivity of the tube decreases, the overall heat transfer coefﬁctents
will increase.
D. The overall heat transfer coefﬁcients can be larger than one of the convective heat
transfer coefficients for heat transfer inside or outside of the tubes.
E. None of the above.
17. For a shell and tube heat exchanger which has tubes with an inside diameter of 20 mm and an
outside diameter of 22 mm. The fluid on both the shell and tube side is water such that the
convective heat transfer coefﬁcients on the inside of the tubes and the outside of the tubes are
equal and have a value of 50 [W/m2 K]. If the resistance to heat transfer through the wall is
negligible, which of the following overall heat transfer coefﬁcient values would be used with
the outside tribe surface area to calculate the amount of heat exchanged between the two
streams?
A. 50.0 [W/m2 K]
B. 25.0 [W/mZ K]
c. 23.8 [wmn2 K]
D. Can not be determined without knowing the length of the tubes
E. None of the above
18. You are analyzing heat transfer through a ﬂat thick wall of insulation. The air temperature
outside the wall is 90 ”F and the wall surface temperature on the side exposed to the 90 °F air is
80 ”F at steady-state. The air temperature inside the wall is 72 ”F and the wall surface
temperature on the inside exposed to the 72 °F air is 75 °F at steady-state. Which of the
following statements is TRUE?
A- houtsldl = hillside
3- hoursme > hinsme
C- houtslde < hmnde .
D. No relationship between the two convective heat transfer coefﬁcients can be determined
from the information given
19. You have a packed bed in which the superﬁcial velocity is 10 m/s and the void volume under
these ﬂow conditions is 0.4. Which of the following is the average interstitial ﬂow velocity for
ﬂuid between the particles in the bed?
4 m/s
10 m/s
20 m/s
25 m/s
None of the above
P1909“?
9/13 Name: _I/ T T W W
30, You have a large sand ﬁlter bed that is operated as a ﬂuidized bed. When there is no ﬂow
through the bed. the total depth of the sand in the bed is 10 ft and the bed has a Void “2‘9“0“ 0‘
0.4. The void fraction of the bed at minimum tluidization has been determined to be 0.45.
How deep will the sand in the bed be (rounded to the nearest 0.1 ft) when the bed 15 at
minimum ﬂuidization conditions?
A. 8.9 ft
B. 10ft
C. 10.9 ft
D. 40.0 n
E. None ofthe above
22. You have a heat exchanger in which 20 gpm of cold water enters at 20 6C and exits at 40 °C.
The hot stream flows at a rate of 40 gpm and enters at 90 “C. The overall heat transfer
coefficient is 30 [W/ m2 K] for these conditions. The heat capacity of water is 4.2 [J g °C].
What is the exit temperature of the hot stream?
50 °C
60 °C
70 °C
80 °C
None of the above
neon?
'oiimN

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