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Heat-transfer Questions Set 32:

Quiz Mode

Where is the Stefan-Boltzmann law applicable?

convection

radiation

absorption

emission

Solution:

Find the heat flux if the heat flow rate is 2100 W and the area is 2 m².

1050 W/m²

4200 W/m²

2102 W/m²

2098 W/m²

Solution:

When a surface absorbs a certain fixed percentage of striking radiation, the surface is called a:

Grey Body

Black Body

White Body

Opaque Body

Solution:

Which equation holds true for the thermal conductivity of an isotropic material?

K = Kx + Ky + Kz

K = Kx - Ky - Kz

K = Kx + Ky - Kz

K = Kx = Ky = Kz

Solution:

To find the Reynolds number when the volume and diameter are given, which additional parameter is required?

Dynamic viscosity

Absolute viscosity

Density

Kinematic viscosity

Solution:

The rate of heat transfer through a plane wall of homogeneous material with constant thermal conductivity is given by the formula:

Q = 2kAδx

Q = 2kAx/ δ

Q = 2k/δ x

Q = kA(t₁ - t₂) / δ

Solution:

Why are baffles provided on the shell side in a shell and tube heat exchanger?

To prevent stagnation of shell-side fluid

To improve heat exchanger performance

To provide support for the tubes

All of the above

Solution:

Calculate the heat flux at the surface of the radiator if it behaves as a black body in a domestic heating system that operates at a surface temperature of 60 degrees Celsius.

592.1 W/m²

697.2 W/m²

786.9 W/m²

324.7 W/m²

Solution:

Let Grashof number = Gr, and Reynold number = Re. The relation between them is Gr = a * Re. The value of 'a' is:

Inertial force/Viscous force

Inertial force/Buoyant force

Buoyant force/Viscous force

Inertial force/Buoyant force^2

Solution:

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

Air conditioning installations and nuclear reactors

Flow of water inside the condenser tubes

Cooling of internal combustion engine

Cooling of billets in the atmosphere

Heat-transfer Questions Set 32:

Where is the Stefan-Boltzmann law applicable?

Solution:

Find the heat flux if the heat flow rate is 2100 W and the area is 2 m².

Solution:

When a surface absorbs a certain fixed percentage of striking radiation, the surface is called a:

Solution:

Which equation holds true for the thermal conductivity of an isotropic material?

Solution:

To find the Reynolds number when the volume and diameter are given, which additional parameter is required?

Solution:

The rate of heat transfer through a plane wall of homogeneous material with constant thermal conductivity is given by the formula:

Solution:

Why are baffles provided on the shell side in a shell and tube heat exchanger?

Solution:

Calculate the heat flux at the surface of the radiator if it behaves as a black body in a domestic heating system that operates at a surface temperature of 60 degrees Celsius.

Solution:

Let Grashof number = Gr, and Reynold number = Re. The relation between them is Gr = a * Re. The value of 'a' is:

Solution:

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

Solution:

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