Heat Transfer (3151909) MCQs

MCQs of Transient Heat Conduction

Showing 1 to 10 out of 13 Questions
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1.

According to lumped system analysis, solid possesses thermal conductivity that is

(a)

Infinitely large
(b)

Infinitely small
(c)

Moderate
(d)

50% small
Answer:

Option (a)

2.

Glass spheres of 2 mm radius and at 500 degree Celsius is to be cooled by exposing them to an air stream at 25 degree Celsius. Find the minimum time required for cooling to a temperature of 60 degree Celsius. Assume the following property values
Density = 2250 kg/m3
Specific heat = 850 J/kg K
Conductivity = 1.5 W/m K

(a)

13.78 seconds
(b)

14.78 seconds
(c)

15.78 seconds
(d)

16.78 seconds
Answer:

Option (b)

3.

Which is true regarding lumped system analysis?
(i) Conductive resistance = 0
(ii) Convective resistance = 0
(iii) Thermal conductivity = 0
(iv) Thermal conductivity = infinity
Identify the correct statements

(a)

i and ii
(b)

 i, ii and iv
(c)

i and iv
(d)

 ii and iv
Answer:

Option (c)

4.

What is the value of characteristics length for the cylinder?

(a)

R/5
(b)

R/4
(c)

R/3
(d)

R/2
Answer:

Option (d)

5.

What is the criterion for the applicability of lump system analysis?

(a)

Mean length
(b)

Normal length
(c)

Characteristics length
(d)

Mass no
Answer:

Option (c)

6.

 What is the value of characteristics length for the sphere?

(a)

R/2
(b)

R/3
(c)

R/4
(d)

R/5
Answer:

Option (b)

7.

Which of the following dimensionless number gives an indication of the ratio of internal (conduction) resistance to the surface (convective) resistance?

(a)

Biot number
(b)

 Fourier number
(c)

Stanton number
(d)

Nusselt number
Answer:

Option (a)

8.

 Lumped parameter analysis for transient heat conduction is essentially valid for

(a)

Bi < 0.1
(b)

1 < Bi< 10
(c)

0.1 < Bi < 0.5
(d)

It tends to infinity
Answer:

Option (a)

9.

In the non-dimensional Biot number, the characteristics length is the ratio of

(a)

Perimeter to the surface area of solid
(b)

Surface area to perimeter of solid
(c)

Surface area to volume of solid
(d)

Volume of solid to its surface area
Answer:

Option (d)

10.

The quantity hLC/k is known as

(a)

Biot number
(b)

Fourier number
(c)

Stanton number
(d)

Nusselt number
Answer:

Option (a)

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