Heat Transfer From Extended Surfaces MCQs

Welcome to our comprehensive collection of Multiple Choice Questions (MCQs) on Heat Transfer From Extended Surfaces, a fundamental topic in the field of Heat Transfer. Whether you're preparing for competitive exams, honing your problem-solving skills, or simply looking to enhance your abilities in this field, our Heat Transfer From Extended Surfaces MCQs are designed to help you grasp the core concepts and excel in solving problems.

In this section, you'll find a wide range of Heat Transfer From Extended Surfaces mcq questions that explore various aspects of Heat Transfer From Extended Surfaces problems. Each MCQ is crafted to challenge your understanding of Heat Transfer From Extended Surfaces principles, enabling you to refine your problem-solving techniques. Whether you're a student aiming to ace Heat Transfer tests, a job seeker preparing for interviews, or someone simply interested in sharpening their skills, our Heat Transfer From Extended Surfaces MCQs are your pathway to success in mastering this essential Heat Transfer topic.

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Heat Transfer From Extended Surfaces MCQs | Page 2 of 8

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Q11.
If heat conducted into the element at plane x is Q X = โ€“ k A C (d t/d x) X. Then heat conducted out of the element at plane (x + d x) is

a.

โ€“ 2k A C d/d x (t + d t/d x (d x))

b.

โ€“ k A C d/d x (t + d t/d x (d x))

c.

โ€“ 3k A C d/d x (t + d t/d x (d x))

d.

โ€“ 4k A C d/d x (t + d t/d x (d x))

Discuss
Answer: (b).โ€“ k A C d/d x (t + d t/d x (d x))
Q12.
A very long copper rod 20 mm in diameter extends horizontally from a plane heated wall maintained at 100 degree Celsius. The surface of the rod is exposed to an air environment at 20 degree Celsius with convective heat transfer coefficient of 8.5 W/m² degree. Workout the heat loss if the thermal conductivity of copper is 400 W/m degree

a.

10.71 W

b.

20.71 W

c.

30.71 W

d.

40.71 W

Discuss
Answer: (b).20.71 W
Q13.
Common applications of finned surfaces are with

(i) Electrical motors

(ii) Economizers for steam power plant

(iii) Convectors for steam and cold water heating systems

(iv) Cooling coils

Identify the correct option

a.

1, 2 and 4

b.

1, 2 and 3

c.

1, 2, 3 and 4

d.

1 and 2

Discuss
Answer: (a).1, 2 and 4
Q14.
The extended surface used for the enhancement of heat dissipation is

a.

Convective coefficient

b.

Fourier number

c.

Fin

d.

No finned surface

Discuss
Answer: (c).Fin
Q15.
It is said that fins can take a variety of forms

(i) Longitudinal fins of rectangular cross section attached to a wall

(ii) Cylindrical tubes with radial fins

(iii) Conical rod protruding from a wall

Identify the correct statement

a.

1 only

b.

1 and 2

c.

2 and 3

d.

1, 2 and 3

Discuss
Answer: (d).1, 2 and 3
Q16.
A heating unit is made in the form of a vertical tube of 50 mm outside diameter and 1.2 m height. The tube is fitted with 20 steel fins of rectangular section with height 40 mm and thickness 2.5 mm. The temperature at the base of fin is 75 degree Celsius, the surrounding air temperature is 20 degree Celsius and the heat transfer coefficient between the fin as well as the tube surface and the surrounding air is 9.5 W/m² K. If thermal conductivity of the fin material is 55 W/m K, find the amount of heat transferred from the tube without fin

a.

98.44 W

b.

88.44 W

c.

78.44 W

d.

68.44 W

Discuss
Answer: (a).98.44 W
Q17.
For steady flow of heat along a rod, the general equation is
d²ฮฑ/dx² โ€“ m² ฮฑ = 0
The value of constant m is

a.

(h P/k A C)

b.

(h P/k A C)^3/2

c.

(h P/k A C)^1/2

d.

(h P/k A C)^2

Discuss
Answer: (c).(h P/k A C)^1/2
Q18.
In convection from the tip, we introduced a factor known as

a.

Fin length

b.

Correction length

c.

No fin length

d.

Radial length

Discuss
Answer: (b).Correction length
Q19.
Find the value of corrected length for rectangular fin?
Where, b is width and t is length of the fin

a.

L C = L + b t/2 (b + t)

b.

L C = L + b t/ (b + t)

c.

L C = L + 2 (b + t)

d.

L C = L + b t

Discuss
Answer: (a).L C = L + b t/2 (b + t)
Q20.
A steel rod (k = 30 W/m degree) 1 cm in diameter and 5 cm long protrudes from a wall which is maintained at 10 degree Celsius. The rod is insulated at its tip and is exposed to an environment with h = 50 W/m² degree and t a = 30 degree Celsius. Calculate the fin efficiency

a.

56.57%

b.

66.57%

c.

76.57%

d.

86.57%

Discuss
Answer: (b).66.57%
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