The temperature of flue gases flowing through the large stack of a boiler is measured by means of a thermocouple enclosed within a cylindrical tube as shown. The tube axis is oriented normal to the gas flow, and the thermo couple senses a temperature T, corresponding to that of the tube surface. The gas flow rate and temperature are designated as the m g and T g . respectively, and the gas flow may be assumed to be fully developed. The stack is fabricated from sheet metal that is at a uniform temperature T ∞ and is exposed to ambient air at T s , and large surroundings at T s u r . The convection coefficient associated with the outer surface of the duct is designated as h 0 , while those associated with the inner surface of the duct and the tube surface are designated as h i and h t , respectively. The tube and duct surface emissivities are designated as ε t and ε s respectively. (a) Neglecting conduction losses along the thermocouple tube, develop an analysis that could be used topredict the error ( T g − T t ) in the temperature measurement. (b) Assuming the flue gas (o have the properties ofatmospheric air, evaluate the error for T t = 300 ° C , D s = = 0.6 m , D t = 10 mm,mg = 1 kg/s , T ∞ = T s u r = 27 ° C , ε t = ε s = 0.8 , and h 0 = 25 W/m 2 ⋅ K .
The temperature of flue gases flowing through the large stack of a boiler is measured by means of a thermocouple enclosed within a cylindrical tube as shown. The tube axis is oriented normal to the gas flow, and the thermo couple senses a temperature T, corresponding to that of the tube surface. The gas flow rate and temperature are designated as the m g and T g . respectively, and the gas flow may be assumed to be fully developed. The stack is fabricated from sheet metal that is at a uniform temperature T ∞ and is exposed to ambient air at T s , and large surroundings at T s u r . The convection coefficient associated with the outer surface of the duct is designated as h 0 , while those associated with the inner surface of the duct and the tube surface are designated as h i and h t , respectively. The tube and duct surface emissivities are designated as ε t and ε s respectively. (a) Neglecting conduction losses along the thermocouple tube, develop an analysis that could be used topredict the error ( T g − T t ) in the temperature measurement. (b) Assuming the flue gas (o have the properties ofatmospheric air, evaluate the error for T t = 300 ° C , D s = = 0.6 m , D t = 10 mm,mg = 1 kg/s , T ∞ = T s u r = 27 ° C , ε t = ε s = 0.8 , and h 0 = 25 W/m 2 ⋅ K .
Solution Summary: The author explains the error in temperature measurement and the expression for heat convection.
The temperature of flue gases flowing through the large stack of a boiler is measured by means of a thermocouple enclosed within a cylindrical tube as shown. The tube axis is oriented normal to the gas flow, and the thermo couple senses a temperature T, corresponding to that of the tube surface. The gas flow rate and temperature are designated as the
m
g
and
T
g
. respectively, and the gas flow may be assumed to be fully developed. The stack is fabricated from sheet metal that is at a uniform temperature
T
∞
and is exposed to ambient air at
T
s
, and large surroundings at
T
s
u
r
. The convection coefficient associated with the outer surface of the duct is designated as
h
0
, while those associated with the inner surface of the duct and the tube surface are designated as
h
i
and
h
t
, respectively. The tube and duct surface emissivities are designated as
ε
t
and
ε
s
respectively.
(a) Neglecting conduction losses along the thermocouple tube, develop an analysis that could be used topredict the error
(
T
g
−
T
t
)
in the temperature measurement.
(b) Assuming the flue gas (o have the properties ofatmospheric air, evaluate the error for
T
t
=
300
°
C
,
D
s
=
=
0.6
m
,
D
t
=
10
mm,mg
=
1
kg/s
,
T
∞
=
T
s
u
r
=
27
°
C
,
ε
t
=
ε
s
=
0.8
,
and
h
0
=
25
W/m
2
⋅
K
.
Question 2
You are an engineer working in the propulsion team for a supersonic civil transport
aircraft driven by a turbojet engine, where you have oversight of the design for the
engine intake and the exhaust nozzle, indicated in Figure Q2a. The turbojet engine can
operate when provided with air flow in the Mach number range, 0.60 to 0.80. You are
asked to analyse a condition where the aircraft is flying at 472 m/s at an altitude of
14,000 m. For all parts of the question, you can assume that the flow path of air through
the engine has a circular cross section.
(a)
normal
shock
472 m/s
A B
(b)
intake
engine
altitude: 14,000 m
D
exhaust nozzle→
exit to
atmosphere
472 m/s
50 m/s
B
diameter: DE = 0.30 m
EX
diameter: DF = 0.66 m
Figure Q2: Propulsion system for a supersonic aircraft.
F
a) When the aircraft is at an altitude of 14,000 m, use the International Standard
Atmosphere in the Module Data Book to state the local air pressure and tempera-
ture. Thus show that the aircraft speed of…
given below:
A rectangular wing with wing twist yields the spanwise circulation distribution
kbV1
roy) = kbv. (2)
where k is a constant, b is the span length and V. is the free-stream velocity. The wing has an
aspect ratio of 4. For all wing sections, the lift curve slope (ag) is 2 and the zero-lift angle of
attack (a=0) is 0.
a. Derive expressions for the downwash (w) and induced angle of attack a distributions
along the span.
b. Derive an expression for the induced drag coefficient.
c. Calculate the span efficiency factor.
d. Calculate the value of k if the wing has a washout and the difference between the
geometric angles of attack of the root (y = 0) and the tip (y = tb/2) is:
a(y = 0) a(y = ±b/2) = /18
Hint: Use the coordinate transformation y = cos (0)
۳/۱
العنوان
O
не
شكا
+91x PU + 96852
A heavy car plunges into a lake during an accident and lands at the bottom of the lake
on its wheels as shown in figure. The door is 1.2 m high and I m wide, and the top edge of
Deine the hadrostatic force on the
Plot the displacement diagram for a cam with roller follower of diameter 10 mm. The required
motion is as follows;
1- Rising 60 mm in 135° with uniform acceleration and retardation motion.
2- Dwell 90°
3- Falling 60 mm for 135° with Uniform acceleration-retardation motion.
Then design the cam profile to give the above displacement diagram if the minimum circle
diameter of the cam is 50 mm.
=
-20125
750 x2.01
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Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning