Heat Transfer MCQ’s – Boiling
1 - Question
Boiling refers to a change from the
a) Solid to a liquid phase
b) Vapor to a liquid phase
c) Liquid to a solid phase
d) Liquid to a vapor phase
Explanation: Boiling is a convective heat transfer process that is associated with a change in the phase of a fluid.
2 - Question
The boiling process has wide-spread applications in (i) Production of steam in nuclear and steam power plants for generation and for industrial processes and space heating (ii) Absorption of heat in refrigeration and air-conditioning systems (iii) Concentration, dehydration and drying of foods and materials Identify the correct statements
a) i and ii
b) ii and iii
c) i, ii and iii
d) i and iii
Explanation: Boiling constitutes the convective heat transfer process that involves a phase change from liquid to vapor state.
3 - Question
Maximum heat transfer rate in a modern boiler is about
a) 2 * 10 5 W/m2
b) 3 * 10 5 W/m2
c) 4 * 10 5 W/m2
d) 5 * 10 5 W/m2
Explanation: Greater importance has recently been given to the boiling heat transfer.
4 - Question
Which type of boiling occurs in steam boilers employing natural convection?
a) Forced convection
Explanation: The liquid above the hot surface is essentially stagnant and the only motion near the surface is because of free convection.
5 - Question
In which type of boiling the fluid motion is induced by external means?
c) Forced convection
Explanation: The liquid is pumped and forced across the surface in a controlled manner.
6 - Question
The temperature of the liquid is below the saturation temperature and boiling takes place only in vicinity of the heated surface. This type of boiling is known as
Explanation: The vapor bubbles travel a short path and then vanish, apparently they condense in the bulk of the liquid which is at a temperature less than the boiling point.
7 - Question
In which type of boiling the temperature of the liquid exceeds the saturation temperature?
Explanation: The vapor bubbles generated at the solid surface are transported through the liquid by buoyancy effects and eventually escape from the surface.
8 - Question
The phenomenon of stable film boiling is referred to as
a) Nucleate effect
b) Boiling regimes
c) Leiden frost effect
d) Von karma effect
Explanation: This is the region of stable film boiling.
9 - Question
For water evaporating at atmospheric pressure, the burnout occurs at temperature excess slightly above
a) 25 K
b) 55 K
c) 75 K
d) 105 K
Explanation: The burnout point on the boiling curve represents the point of maximum heat flux at which transition occurs from nucleate to film boiling.
10 - Question
The boiling phenomenon is known to occur in how many forms?
Explanation: Pool, forced convection, subcooled and saturated boiling.