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 3 of 8

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Q21.
The temperature distribution in case of fin insulated at the tip is given by

a.

t – t₀/t₀ – t a = cos h m (3 – x)/cos ml

b.

t – t₀/t₀ – t a = cos h m (2 – x)/sin h ml

c.

t – t₀/t₀ – t a = cos h m (l – x)/cos h ml

d.

t – t₀/t₀ – t a = cos m (l – x)/sin ml

Discuss
Answer: (c).t – t₀/t₀ – t a = cos h m (l – x)/cos h ml
Q22.
The rate of heat transfer from the fin in case of fin insulated at the tip is

a.

(h P k A)^1/2 (t₀ – t a) tan h ml

b.

(h k A)^1/2 (t₀ – t a) tan h ml

c.

(h P A)^1/2 (t₀ – t a) tan h ml

d.

(h P k)^1/2 (t₀ – t a) tan h ml

Discuss
Answer: (a).(h P k A)^1/2 (t₀ – t a) tan h ml
Q23.
“Fin is insulated at the tip”. What does that mean?

a.

Less heat is transferred from the tip

b.

Heat will transferred from tip only

c.

More heat is transferred from the tip

d.

No heat is transferred from the tip

Discuss
Answer: (d).No heat is transferred from the tip
Q24.
Find the heat transfer rate from a hot surface for 6 fins of 10 cm length? The base temperature of the fin is maintained at 200 degree Celsius and the film is exposed to a convection environment at 15 degree Celsius with convective coefficient 25W/square m K. Each fin has cross-sectional area 2.5 square centimeter and is made of a material having thermal conductivity 250W/m K

a.

120.34W

b.

130.18W

c.

145.46W

d.

165.43W

Discuss
Answer: (b).130.18W
Q25.
An electronic semiconductor device generates 0.16 k J/hr of heat. To keep the surface temperature at the upper safe limit of 75 degree Celsius, it is desired that the heat generated should be dissipated to the surrounding environment which is at 30 degree Celsius. The task is accomplished by attaching aluminum fins, 0.5 square mm and 10 mm to the surface. Work out the number of fins if thermal conductivity of fin material is 690W/m K and the heat transfer coefficient is 45k J/square m hr K. Neglect the heat loss from the tip of the fin

a.

4

b.

3

c.

2

d.

1

Discuss
Answer: (a).4
Q26.
A rod of 10 mm diameter and 80 mm length with thermal conductivity 16W/ m K protrudes from a surface at 160 degree Celsius. The rod is exposed to air at 30 degree Celsius with a convective coefficient of 25W/square m K. How does the heat flow from this rod get affected if the same material volume is used for two fins of the same length? Assume short fin with insulated end

a.

12.25 %

b.

25.6 %

c.

23.4 %

d.

21.2 %

Discuss
Answer: (d).21.2 %
Q27.
Two rods A and B of the same length and diameter protrude from a surface at 120 degree Celsius and are exposed at air at 25 degree Celsius. The temperatures measured at the end of the rods are 50 degree Celsius and 75 degree Celsius. If thermal conductivity of material A is 20W/ m K, calculate it for B.

a.

31.13W/m K

b.

41.13W/m K

c.

51.13W/m K

d.

61.13W/m K

Discuss
Answer: (c).51.13W/m K
Q28.
An centrifugal pump which circulates a hot liquid metal at 500 degree Celsius is driven by a 3600 rpm electric motor. The motor is coupled to the pump impeller by a horizontal steel shaft of dia 25 mm. Let us assume the motor temperature as 60 degree Celsius with the ambient air at 25 degree Celsius, what length of shaft should be specified between the motor and the pump? It may be presumed that the thermal conductivity of the shaft material is 35W/m K, and that the convective film coefficient between the steel shaft and the ambient air is 15.7W/square m K

a.

38.96 cm

b.

54.76 cm

c.

23.76 cm

d.

87.43 cm

Discuss
Answer: (a).38.96 cm
Q29.
The utility of fin in dissipating a given quantity of heat is generally assessed on the basic of how many parameters?

a.

1

b.

2

c.

3

d.

4

Discuss
Answer: (b).2
Q30.
A copper steel rod (k = 55 W/m degree) has been attached to a plane wall which is maintained at a temperature of 350 degree Celsius. The rod is 8 cm long and has the cross-section of an equilateral triangle with each side 5 mm. Determine the heat dissipation from the rod if it is exposed to a convection environment at 25 degree Celsius with unit surface conductance 100 W/m² degree. Consider end surface loss to be negligible

a.

10.26 W

b.

9.26 W

c.

8.26 W

d.

7.26 W

Discuss
Answer: (b).9.26 W
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