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!

So, are you ready to put your Transient Heat knowledge to the test? Let's get started with our carefully curated MCQs!

Transient Heat MCQs | Page 4 of 8

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Q31.
β€œThermal radiation suffers no attenuation in a vacuum”. Choose the correct answer

a.

True

b.

False

c.

May be

d.

Can't say

Discuss
Answer: (a).True
Q32.
How does the body temperature falls or rises with time?

a.

Logarithmic

b.

Parabolic

c.

Linear

d.

Exponentially

Discuss
Answer: (d).Exponentially
Q33.
An iron billet (k = 65 W/m K) measuring 20 * 15 * 80 cm is exposed to a convective flow resulting in convection coefficient of 11.5 W/m² K. Determine the Biot number

a.

0.02376

b.

0.008974

c.

0.004563

d.

0.006846

Discuss
Answer: (d).0.006846
Q34.
A mercury thermometer with bulb idealized as a sphere of 1 mm radius is used for measuring the temperature of fluid whose temperature is varying at a fast rate. For mercury

k = 10 W/m K
Ξ± = 0.00005 m²/s
h = 10 W/m² K

If the time for the temperature change of the fluid is 3 second, what should be the radius of thermocouple to read the temperature of the fluid?
For the thermocouple material
k = 100 W/m K
Ξ± = 0.0012 m²/s
h = 18 W/m² K

a.

.864 mm

b.

.764 mm

c.

.664 mm

d.

.564 mm

Discuss
Answer: (a)..864 mm
Q35.
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
Q36.
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
Q37.
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)
Q38.
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
Q39.
A thermocouple junction of spherical form is to be used to measure the temperature of the gas stream. The junction is at 20 degree Celsius and is placed in a gas stream which is at 200 degree Celsius. Make calculations for junction diameter needed for the thermocouple to have thermal time constant of one second. Assume the thermos-physical properties as given below
k = 20 W/ m K
h = 350 W/m² K
c = 0.4 k J/kg K
p = 8000 kg/m³

a.

0.456 mm

b.

0.556 mm

c.

0.656 mm

d.

0.756 mm

Discuss
Answer: (c).0.656 mm
Q40.
A flat wall of fire clay, 50 cm thick and initially at 25 degree Celsius, has one of its faces suddenly exposed to a hot gas at 950 degree Celsius. If the heat transfer coefficient on the hot side is 7.5 W/m² K and the other face of the wall is insulated so that no heat passes out of that face, determine the time necessary to raise the center of the wall to 350 degree Celsius. For fire clay brick
Thermal conductivity = 1.12 W/m K
Thermal diffusivity = 5.16 * 10¯β· m²/s

a.

43.07 hours

b.

53.07 hours

c.

63.07 hours

d.

73.07 hours

Discuss
Answer: (a).43.07 hours
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