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 5 of 8

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Q41.
How does the body temperature falls or rises with time?

a.

Logarithmic

b.

Parabolic

c.

Linear

d.

Exponentially

Discuss
Answer: (d).Exponentially
Q42.
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
Q43.
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
ฮฑ = 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
ฮฑ = 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
Q44.
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
Q45.
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¯โท m²/s

a.

43.07 hours

b.

53.07 hours

c.

63.07 hours

d.

73.07 hours

Discuss
Answer: (a).43.07 hours
Q46.
Glass spheres of 2 mm radius and at 500 degree Celsius are to be cooled by exposing them to an air stream at 25 degree Celsius. Find maximum value of convective coefficient that is permissible. Assume the following property values
Density = 2250 kg/m³
Specific heat = 850 J/kg K
Conductivity = 1.5 W/m K

a.

245 W/m²K

b.

235 W/m²K

c.

225 W/m²K

d.

215 W/m²K

Discuss
Answer: (c).225 W/m²K
Q47.
The transient response of a solid can be determined by the equation. (Where, P is density, V is volume, c is specific heat and A is area)

a.

โ€“ 4 p V c = h A (t โ€“ t0)

b.

โ€“ 3 p V c = h A (t โ€“ t0)

c.

โ€“ 2 p V c = h A (t โ€“ t0)

d.

โ€“ p V c = h A (t โ€“ t0)

Discuss
Answer: (d).โ€“ p V c = h A (t โ€“ t0)
Q48.
A 2 cm thick steel slab heated to 525 degree Celsius is held in air stream having a mean temperature of 25 degree Celsius. Estimate the time interval when the slab temperature would not depart from the mean value of 25 degree Celsius by more than 0.5 degree Celsius at any point in the slab. The steel plate has the following thermal physical properties
Density = 7950 kg/m³
C P = 455 J/kg K
K = 46 W/m K

a.

6548 s

b.

6941 s

c.

4876 s

d.

8760 s

Discuss
Answer: (b).6941 s
Q49.
An average convective heat transfer coefficient for flow of air over a sphere has been measured by observing the temperature-time history of a 12 mm diameter copper sphere (density = 9000 kg/m³ and c = 0.4 k J/kg K) exposed to air at 30 degree Celsius. The temperature of the sphere was measured by two thermocouples one located at the center and the other near the surface. The initial temperature of the ball was 75 degree Celsius and it decreased by 10 degree Celsius in 1.2 minutes. Find the heat transfer coefficient

a.

27.46 W/m² K

b.

21.76 W/m² K

c.

29.37 W/m² K

d.

25.13 W/m² K

Discuss
Answer: (d).25.13 W/m² K
Q50.
Transient condition means

a.

Conduction when temperature at a point varies with time

b.

Very little heat transfer

c.

Heat transfer with a very little temperature difference

d.

Heat transfer for a short time

Discuss
Answer: (a).Conduction when temperature at a point varies with time
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