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 1 of 8

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Q1.
The time constant of a thermocouple is the time taken to

a.

Minimum time taken to record a temperature reading

b.

Attain 50% of initial temperature difference

c.

Attain the final value to be measured

d.

Attain 63.2% of the value of initial temperature difference

Discuss
Answer: (d).Attain 63.2% of the value of initial temperature difference
Q2.
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.

0.556 mm

b.

0.656 mm

c.

0.756 mm

d.

0.856 mm

Discuss
Answer: (b).0.656 mm
Q3.
A low value of time constant can be achieved for a thermocouple by

(i) Increasing the wire diameter
(ii) Increasing the value heat transfer coefficient
(iii) Use light metals of low density and low specific heat

Identify the correct statements

a.

2 and 3

b.

1 and 3

c.

1 and 2

d.

1, 2 and 3

Discuss
Answer: (a).2 and 3
Q4.
Which of the following has units of time constant?
(Where, P is density, A is area, c is specific heat and V is volume)

a.

p V/h A

b.

p c/h A

c.

p V c/h A

d.

V c/h A

Discuss
Answer: (c).p V c/h A
Q5.
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
Q6.
How does the body temperature falls or rises with time?

a.

Logarithmic

b.

Parabolic

c.

Linear

d.

Exponentially

Discuss
Answer: (d).Exponentially
Q7.
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
Q8.
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
Q9.
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
Q10.
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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