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 2 of 8

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Q11.
The response time for different sizes and materials of thermocouple wires usually lie between

a.

0.04 to 2.5 seconds

b.

0.06 to 1.2 seconds

c.

0.02 to 0.04 seconds

d.

2.4 to 9.4 seconds

Discuss
Answer: (a).0.04 to 2.5 seconds
Q12.
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 time required by the thermocouple to reach 197 degree Celsius temperature. 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.

1.094 seconds

b.

2.094 seconds

c.

3.094 seconds

d.

4.094 seconds

Discuss
Answer: (d).4.094 seconds
Q13.
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
Q14.
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¯⁷ m²/s

a.

43.07 hours

b.

53.07 hours

c.

63.07 hours

d.

73.07 hours

Discuss
Answer: (a).43.07 hours
Q15.
An egg with mean diameter of 4 cm and initially at 25 degree Celsius is placed in an open boiling water container for 4 minutes and found to be boiled at a particular level. For how long should a similar egg boil at the same level, when refrigerator temperature is 5 degree Celsius? Use lumped parameter theory and assume following properties of egg

k = 12 W/m K

h = 125 W/m² K

c = 2 k J/kg K

p = 1250 kg/m³

a.

251.49 seconds

b.

261.49 seconds

c.

271.49 seconds

d.

281.49 seconds

Discuss
Answer: (c).271.49 seconds
Q16.
A person is found dead at 5 pm in a room whose temperature is 20 degree Celsius. The temperature of body is measured to be 25 degree Celsius, when found and heat transfer coefficient is estimated to be 8 W/m² K. Modeling the body as a 30 cm diameter, 1.7 cm long cylinder. Estimate the time of death of person.

a.

13.55 seconds

b.

12.55 seconds

c.

11.55 seconds

d.

10.55 seconds

Discuss
Answer: (d).10.55 seconds
Q17.
The following data pertains to the junction of a thermocouple wire used to measure the temperature of the gas stream.

Density = 8500 kg/m³, specific heat = 325 J/kg K, thermal conductivity = 40 W/m K and the heat transfer coefficient between the junction and gas = 215 W/m² K.

If thermocouple junction can be approximated as 1 mm diameter sphere, determine how long it will take for the thermocouple to read 99% of the initial temperature difference.

a.

9.86 seconds

b.

8.86 seconds

c.

7.86 seconds

d.

6.86 seconds

Discuss
Answer: (a).9.86 seconds
Q18.
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
Q19.
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.

– 4 p V c = h A (t – t0)

b.

– 3 p V c = h A (t – t0)

c.

– 2 p V c = h A (t – t0)

d.

– p V c = h A (t – t0)

Discuss
Answer: (d).– p V c = h A (t – t0)
Q20.
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
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