This set of Heat Transfer Multiple Choice Questions & Answers (MCQs) focuses on “Shape Factor”.
1. “All the factors relating to the geometry of the sections are grouped together into a multiple constant called the shape factor”.
a) True
b) False
View Answer
Explanation: They are grouped together into a single constant instead of multiple one.
2. Shape factor for a plane wall is equal to
a) A/δ
b) 2A/δ
c) 3A/δ
d) 4A/δ
View Answer
Explanation: It should be obtained by dividing area with respect to length.
3. For a prescribed temperature difference, bodies with the same shape factor will allow heat conduction proportional to
a) k/2
b) 2k
c) k
d) k/4
View Answer
Explanation: It is proportional to material thermal conductivity irrespective of size and configuration.
4. Shape factor for cylinder is
a) 6 π l/log e (r 2/r 1)
b) 4 π l/log e (r 2/r 1)
c) π l/log e (r 2/r 1)
d) 2 π l/log e (r 2/r 1)
View Answer
Explanation: It is two times the rest of the product.
5. The annealing furnace for continuous bar stock is open at the ends and has interior dimensions of 0.6 m * 0.6 m * 1.5 m long with a wall 0.3 m thick all around. Calculate the shape factor for the furnace?
a) 15.24 m
b) 16.34 m
c) 14.54 m
d) 13.76 m
View Answer
Explanation: Shape factor for 4 walls = 4 (area of wall)/ (thickness) = 4 (1.5) (0.6)/0.3 = 12 m. Shape factor for 4 edges = 4 (0.54) (1.5) = 3.24 m. Total = 15.24 m.
6. Shape factor for sphere is
a) 4 π r 1 r 2
b) 4 π r 1 r 2/r 2 – r 1
c) 4 π /r 2 – r 1
d) r 1 r 2/r 2 – r 1
View Answer
Explanation: In case of sphere it is given in option b. Area of sphere is 4 π r 2.
7. Which is true regarding a complete rectangular furnace?
a) 6 walls, 12 edges and 6 corners
b) 0 walls, 2 edges and 4 corners
c) 6 walls, 12 edges and 8 corners
d) 2 walls, 6 edges and 8 corners
View Answer
Explanation: It has 6 walls, 12 edges and 8 corners.
8. The shape factor for complete rectangular furnace is
Where a, b and c are the inside dimensions and d x is the wall thickness
a) 2/ d x (a b + b c + c a) + 4 (0.64) (a + b +c) + 8 (0.45) d x
b) 2/ d x (a b + b c + c a) + 4 (0.44) (a + b +c) + 8 (0.35) d x
c) 2/ d x (a b + b c + c a) + 4 (0.34) (a + b +c) + 8 (0.25) d x
d) 2/ d x (a b + b c + c a) + 4 (0.54) (a + b +c) + 8 (0.15) d x
View Answer
Explanation: S edge = 0.54 times length of edge. S corner = 0.15 d x.
9. For the same material and same temperature difference, the heat flow in terms of shape factor is given by
a) S k d t
b) k d t/S
c) 2S k/d t
d) 2S/3
View Answer
Explanation: The heat flow is proportional to the shape factor.
10. For the same amount of fabrication material and same inside capacity, the heat loss is lowest in
a) Sphere
b) Cylinder
c) Rectangle
d) Cube
View Answer
Explanation: For cylinder, it is 0.439 i.e. lowest.
Sanfoundry Global Education & Learning Series – Heat Transfer.
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