Heat Transfer (3151909) MCQs

MCQs of Convection

Showing 11 to 20 out of 51 Questions
11.

Grashoff number is useful in 

(a)

Free Convection

(b)

Forced Convection

(c)

Both

(d)

None of these

Answer:

Option (a)

12.

In the case of fluid flowing over a circular pipe, the fluid properties should be considered at 

(a)

Mean Bulk Temperature

(b)

Mean Film Temperature

(c)

Free Stream Temperature

(d)

None of these

Answer:

Option (b)

13.

Air at 20°C and at a pressure of 1 bar is flowing over a flat plate at a velocity of 3m/sec. If the plate is 280 mm wide and at 56°C, calculate the hydrodynamic boundary layer thickness at x = 280 mm. 

(a)

0.6m

(b)

6.26m

(c)

0.00626 m

(d)

none of these

Answer:

Option (c)

14.

Air at 20°C and at a pressure of 1 bar is flowing over a flat plate of 280mm x 280mm at a velocity of 3m/sec. If the plate is at 56°C, calculate the heat transfer rate from the plate. Take average heat transfer coeficient as 12.86 W/m2K.

(a)

0.36W

(b)

3.6W

(c)

36.3W

(d)

363W

Answer:

Option (c)

15.

The dimensional formula of convective heat transfer coefficient is

(a)

[M T-3θ-1

(b)

[M LT-3θ-1

(c)

[ L2T -2θ-1]

(d)

none of these

Answer:

Option (a)

16.

Which of the following heat flow situations pertains to free or natural convection?

(a)

cooling of internal combustion engines

(b)

flow of water inside the condenser tubes

(c)

cooling of billets in atmosphere

(d)

air-conditioning installations and nuclear reactors

Answer:

Option (c)

17.

The dimensionless parameter l3 ρ2 βgTμ2 is referred to as

(a)

Stanton Number

(b)

Schmidt Number

(c)

Grashoff Number

(d)

Peclet Number

Answer:

Option (c)

18.

Mark the system where heat transfer is by forced convection

(a)

chilling effect of cold wind on warm body 

(b)

fluid passing through the tubes of a condenser and other heat exchange equipment

(c)

heat flow from a hot pavement to surrounding atmosphere

(d)

heat exchange on the outside of cold and warm pipes

Answer:

Option (b)

19.

Forced convection in a liquid bath is caused by  

(a)

density difference brought about by temperature gradients 

(b)

molecular energy interaction 

(c)

flow of electrons in a random fashion

(d)

intense stirring by an external agency

Answer:

Option (d)

20.

A finned tube hot water radiator with a fan blowing air over it is kept in rooms during winter. The major portion of the heat transfer from the radiator is due to

(a)

better conduction 

(b)

convection to the air

(c)

radiation to the surroundings 

(d)

combined conduction and radiation

Answer:

Option (b)

Showing 11 to 20 out of 51 Questions