Convection: Processes and Properties

This quiz contains multiple-choice problems on flow types, convection types, Nusselt number, Reynolds number and the Newton-Rikhman law.

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How many types of convection are there?

4 3 2 1

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 atmosphere

Forced convection in a liquid bath is caused by

Intense stirring by an external agency Molecular energy interactions Density difference brought about by temperature gradients Flow of electrons in a random fashion

In which fluid flow is the motion of fluid particles irregular?

Turbulent

Laminar

One-dimensional

Two-dimensional

How many types of fluid flow are characterized in the realm of fluid mechanics?

The following parameters govern the nature of fluid flow:
(i) Mean flow velocity
(ii) Density of fluid
(iii) Dynamic viscosity of the fluid
Identify the correct statements.

i and iii

i only

i, ii and iii

ii and iii

The following are the characteristics of turbulent flow:
(i) Eddying
(ii) Sinuous
(iii) Rectilinear
Identify the correct option.

ii and iii

i and iii

i, ii and iii

i and ii

The value of air’s convective coefficient in case of free convection is

3-7 W/m^2 K

3-4 W/m^2 K

8-9 W/m^2 K

9-9.5 W/m^2 K

The characteristic dimension d in the relation R{E} = Vdp/δ is the equivalent diameter. How many times is the wetted perimeter defined to divide the cross-sectional flow area?

For a duct of rectangular cross-section with length l and breadth b, the value of d{e} is

l*b/(l + b)

2*l*b

2*l*b/(l + b)

4*l*b/(l + b)

Fluid particles move in flat or curved un-mixing layers or streams and follow a smooth continuous path. This type of flow is known as

Steady flow

Stream flow

Turbulent flow

Laminar flow

In many flow situations, the duct can be
(i) Circular
(ii) Rectangle
(iii) Trapezoidal
(iv) Annulus
Identify the correct option.

i and ii

i, ii, iii and iv

i, ii and iii

iii and iv

If an annulus has an inner diameter d{1} and an outer diameter d{2}, the equivalent diameter is

2*d{2} – d{1}

d{2} – 2*d{1}

d{1} – d{2}

d{2} – d{1}

Mark the system where heat transfer is given by forced convection.

Chilling effect of cold wind on warm body

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

Heat flow from a hot pavement to surrounding atmosphere

Heat exchange on the outside of cold and warm pipes

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

Combined conduction and radiation

Radiation to the surroundings

Better conduction

Convection to the air

Quiz/Test Summary

Title: Convection: Processes and Properties

Questions: 15

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