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 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
Q13.
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
Q14.
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
Q15.
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)
Q16.
Which one is true for the spine?

a.

A C = ฯ€ d²/4 and P = 4 ฯ€ d

b.

A C = ฯ€ d²/4 and P = 3 ฯ€ d

c.

A C = ฯ€ d²/4 and P = ฯ€ d

d.

A C = ฯ€ d²/4 and P = 2 ฯ€ d

Discuss
Answer: (c).A C = ฯ€ d²/4 and P = ฯ€ d
Q17.
In convection from the tip what is the value of correction length?

a.

L C = A C/P

b.

L C = L + A C

c.

L C = L + P

d.

L C = L + A C/P

Discuss
Answer: (d).L C = L + A C/P
Q18.
Let us assume there are two pieces of copper wire 0.1625 cm in diameter with a device that melts it at 195 degree Celsius. The wires are positioned vertically in air at 24 degree Celsius and the heat transfer coefficient of the wire is 17 W/ square m K. Let us say k = 335W/m K i.e. of wire. Find out the energy input?

a.

1.234W

b.

2.652W

c.

4.562W

d.

9.435W

Discuss
Answer: (b).2.652W
Q19.
The figure shows a 5 cm diameter rod, 90 cm long, which is having its lower face grinded smooth. The remainder of the rod is exposed to 32 degree Celsius room air and a surface coefficient heat transfer equal to 6.8 W/m² degree exists between the rod surface and the room air. The grinder dissipates mechanical energy at the rate of 35 W. If thermal conductivity of rod material is 41.5 W/m degree, find the temperature of the rod at the point where the grinding is taking place

a.

161.45 degree celsius

b.

151.45 degree celsius

c.

141.45 degree celsius

d.

131.45 degree celsius

Discuss
Answer: (b).151.45 degree celsius
Q20.
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
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