A hollow aluminum sphere. with an electrical heater in the center. is used in tests to determine the thermal conductivity of insulating materials. The inner and outer radii of the sphere are 0.15 and 0.18 m, respectively. and testing is done under steady-state conditions with the inner surface of the aluminum maintained at 250 ° C . In a particular test, a spherical shell of insulation is cast on the outer surface of the sphere to a thickness of 0.12 m. The system is in a room for which the air temperature is 20 ° C and the convection coefficient at the outer surface of the insulation is 30 W/m ⋅ K . If 80 W are dissipated by the heater under steady-state conditions, what is the thermal conductivity of the insulation?
A hollow aluminum sphere. with an electrical heater in the center. is used in tests to determine the thermal conductivity of insulating materials. The inner and outer radii of the sphere are 0.15 and 0.18 m, respectively. and testing is done under steady-state conditions with the inner surface of the aluminum maintained at 250 ° C . In a particular test, a spherical shell of insulation is cast on the outer surface of the sphere to a thickness of 0.12 m. The system is in a room for which the air temperature is 20 ° C and the convection coefficient at the outer surface of the insulation is 30 W/m ⋅ K . If 80 W are dissipated by the heater under steady-state conditions, what is the thermal conductivity of the insulation?
A hollow aluminum sphere. with an electrical heater in the center. is used in tests to determine the thermal conductivity of insulating materials. The inner and outer radii of the sphere are 0.15 and 0.18 m, respectively. and testing is done under steady-state conditions with the inner surface of the aluminum maintained at
250
°
C
.
In a particular test, a spherical shell of insulation is cast on the outer surface of the sphere to a thickness of 0.12 m. The system is in a room for which the air temperature is
20
°
C
and the convection coefficient at the outer surface of the insulation is
30
W/m
⋅
K
.
If 80 W are dissipated by the heater under steady-state conditions, what is the thermal conductivity of the insulation?
Multiple Choice
Circle the best answer to each statement.
1. Which geometry attribute deviation(s) can be limited
with a profile of a surface tolerance?
A. Location
B. Orientation
C.
Form
D.
All of the above
2. A true profile may be defined with:
A.
Basic radii
B. Basic angles
C. Formulas
D. All of the above
3. Which modifier may be applied to the profile tolerance
value?
A
B
C.
D. All of the above
4. The default tolerance zone for a profile tolerance is:
A. Non-uniform
B. Unilateral
C. Bilateral equal distribution
D. Bilateral-unequal distribution
5. An advantage of using a profile tolerance in place of a
coordinate tolerance is:
A. A bonus tolerance is permitted.
B. A datum feature sequence may be specified
C. A profile tolerance always controls size
D. All of the above
6. The shape of the tolerance zone for a profile tolerance is:
A. Two parallel planes
B. The same as the true profile of the toleranced
surface
C. Equal bilateral
D. Cylindrical when the diameter symbol is speci-
fied…
One thousand kg/h of a (50-50 wt%) acetone-in-water solution is to be extracted at 25C in a continuous,
countercurrent system with pure 1,1,2-trichloroethane to obtain a raffinate containing 10 wt% acetone. Using the
following equilibrium data, determine with an equilateral-triangle diagram:
a- the minimum flow rate of solvent;
b- the number of stages required for a solvent rate equal to 1.5 times minimum, and composition of each
streamleaving each stage.
c- Repeat the calculation of (a) and (b) if the solvent used has purity 93wt% (4wr% acetone, 3wt% water
impurities)
acetone water
1,1,2-trichloroethane
Raffinate. Weight
Extract. Weight
0.6
0.13
0.27
Fraction Acetone
Fraction Acetone
0.5
0.04
0.46
0.44
0.56
0.4
0.03
0.57
0.29
0.40
0.3
0.02
0.68
0.12
0.18
0.2
0.015
0.785
0.0
0.0
0.1
0.01
0.89
0.55
0.35
0.1
0.5
0.43
0.07
0.4
0.57
0.03
0.3
0.68
0.02
0.2
0.79
0.01
0.1
0.895
0.005
2500 kg/hr of (20-80) nicotine water solution is to be extracted with benzene containing 0.5% nicotine in
the 1st and 2ed stages while the 3rd stage is free of nicotine. Cross- current operation is used with different amounts
of solvent for each stages 2000kg/hr in the 1st stage, 2300 kg/hr in the 2nd stage, 2600 kg/hr in the 3rd,
determine: -
a- The final raffinate concentration and % extraction.
b-
b- The minimum amount of solvent required for counter-current operation if the minimum concentration
will be reduced to 5% in the outlet raffinate.
Equilibrium data
Wt % Nicotine in water
Wt % Nicotine in benzene
0
4
16
25
0
4
21
30
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