Transient Heat MCQs

Welcome to our comprehensive collection of Multiple Choice Questions (MCQs) on Transient Heat, 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 Transient Heat 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 Transient Heat mcq questions that explore various aspects of Transient Heat problems. Each MCQ is crafted to challenge your understanding of Transient Heat 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 Transient Heat MCQs are your pathway to success in mastering this essential Heat Transfer topic.

Note: Each of the following question comes with multiple answer choices. Select the most appropriate option and test your understanding of Transient Heat. You can click on an option to test your knowledge before viewing the solution for a MCQ. Happy learning!

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Transient Heat MCQs | Page 3 of 8

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Q21.
The boundary conditions in case of transient heat conduction in infinite thick solids are

(i) t (x = 0) = t i
(ii) t (0, T) = t a for T greater than zero
(iii) t (infinity, T) = t i for T greater than zero
Identify the correct statements

a.

1 and 2

b.

1 and 3

c.

2 and 3

d.

1, 2 and 3

Discuss
Answer: (d).1, 2 and 3
Q22.
The perturbation time varies as

a.

d²/Ξ±

b.

2d²/Ξ±

c.

3d²/Ξ±

d.

4d²/Ξ±

Discuss
Answer: (a).d²/Ξ±
Q23.
The temperature perturbation at all the surface has penetrated to the depth (Where, T is time constant and Ξ± is thermal diffusivity.)

a.

1.6 (Ξ± T)^1/2

b.

2.6 (Ξ± T)^1/2

c.

3.6 (Ξ± T)^1/2

d.

4.6 (Ξ± T)^1/2

Discuss
Answer: (c).3.6 (Ξ± T)^1/2
Q24.
At the penetration depth d, there will be 1% perturbation at a time given by

a.

4 d²/13 Ξ±

b.

3 d²/13 Ξ±

c.

2 d²/13 Ξ±

d.

d²/13 Ξ±

Discuss
Answer: (d).d²/13 Ξ±
Q25.
A large steel ingot, which has been uniformly heated to 750 degree Celsius, is hardened by quenching it in an oil bath that is maintained at 25 degree Celsius. What length of time is required for the temperature to reach 600 degree Celsius at a depth of 1 cm? Thermal diffusivity for the steel ingot is 1.21 * 10¯β΅ m²/s. The ingot may be approximated as a flat plate

a.

4.55 seconds

b.

3.55 seconds

c.

2.55 seconds

d.

1.55 seconds

Discuss
Answer: (c).2.55 seconds
Q26.
A mild steel plate 5 cm thick and initially at 40 degree Celsius temperature is suddenly exposed on one side to a fluid which causes the surface temperature to increase to and remain at 90 degree Celsius. Calculate maximum time that the slab be treated as a semi-infinitely body
For steel, thermal diffusivity = 1.25 * 10¯β΅ m²/s

a.

100 seconds

b.

200 seconds

c.

300 seconds

d.

400 seconds

Discuss
Answer: (b).200 seconds
Q27.
Water pipes are to be buried underground in a wet soil (thermal diffusivity = 2.78 * 10¯³ m²/s) which is initially at 4.5 degree Celsius. The soil surface temperature suddenly drops to -5 degree Celsius and remains at this value for₁0 hours. Calculate the minimum depth at which the pipe be laid if the surrounding soil temperature is to remain above 0 degree Celsius. The soil may be considered as semi-infinite solid

a.

0.467 m

b.

0.367 m

c.

0.267 m

d.

0.167 m

Discuss
Answer: (d).0.167 m
Q28.
When the surface temperature variation inside a solid are periodic in nature, the profile of temperature variation with time may assume

a.

Triangular

b.

Linear

c.

Parabolic

d.

Hyperbolic

Discuss
Answer: (a).Triangular
Q29.
The surface temperature oscillates about the mean temperature level in accordance with the relation

a.

Ξ± S,T – Ξ± S,A = 2 sin (2 Ο€ n T)

b.

Ξ± S,T – Ξ± S,A = 5 sin (2 Ο€ n T)

c.

Ξ± S,T – Ξ± S,A = sin (2 Ο€ n T)

d.

Ξ± S,T – Ξ± S,A = 3 sin (2 Ο€ n T)

Discuss
Answer: (c).Ξ± S,T – Ξ± S,A = sin (2 Ο€ n T)
Q30.
The temperature variation of a thick brick wall during periodic heating or cooling follows a sinusoidal waveform. During a period of 24 hours, the surface temperature ranges from 25 degree Celsius to 75 degree Celsius. Workout the time lag of the temperature wave corresponding to a point located at 25 cm from the wall surface. Thermo-physical properties of the wall material are; thermal conductivity = 0.62 W/m K; specific heat = 450 J/kg K and density = 1620 kg/m³

a.

3.980 hour

b.

6.245 hour

c.

2.648 hour

d.

3.850 hour

Discuss
Answer: (b).6.245 hour
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