Fundamentals of Convection: Master Heat Transfer Principles

Question 1

Boundary layer theory is primarily used to analyze:

Accepted Answer

Laminar flow over a flat plate

Answer

Turbulent flow in a pipe

Answer

Heat transfer in a gas turbine

Answer

Boiling and condensation processes

Question 2

In a fully developed laminar flow in a pipe, the velocity profile is:

Accepted Answer

Parabolic

Answer

Linear

Answer

Exponential

Answer

Sine-shaped

Question 3

Which of the following is a characteristic of laminar flow?

Accepted Answer

Flow in a circular pipe at a low Reynolds number

Answer

Flow over a flat plate at a high Reynolds number

Answer

Flow in a turbulent boundary layer

Answer

Flow in a fluidized bed

Question 4

In laminar natural convection over a vertical flat plate, which dimensionless group primarily governs the Nusselt number?

Accepted Answer

Rayleigh number

Answer

Prandtl number

Question 5

In natural convection heat transfer, which factor does NOT influence the heat transfer rate?

Accepted Answer

External pressure gradient applied to the fluid

Answer

Temperature difference between the surface and the surrounding fluid

Answer

Fluid properties like density, viscosity, and thermal conductivity

Answer

Surface geometry and orientation

Question 6

What is the main factor that causes natural convection heat transfer to occur?

Accepted Answer

Temperature difference

Answer

Pressure difference

Answer

Velocity difference

Answer

Concentration difference

Question 7

Which of the following is the defining characteristic of natural convection?

Accepted Answer

Heat transfer occurs due to a temperature gradient within the fluid.

Answer

Heat transfer is driven by an external force, such as a fan or pump.

Answer

The fluid flow is laminar and steady.

Answer

The fluid flow is turbulent and unsteady.

Question 8

The Nusselt number is a dimensionless quantity that represents:

Accepted Answer

The ratio of convective heat transfer to conduction heat transfer.

Answer

The ratio of heat transfer by radiation to heat transfer by convection.

Answer

The ratio of the fluid velocity to the thermal conductivity.

Answer

The ratio of the temperature difference to the fluid thickness.

Question 9

In natural convection, the Grashof number is a dimensionless quantity that represents:

Accepted Answer

The ratio of buoyancy forces to viscous forces.

Answer

The ratio of inertial forces to viscous forces.

Answer

The ratio of heat transfer by conduction to heat transfer by convection.

Answer

The ratio of the temperature difference to the fluid thickness.

Question 10

Which of the following is a common application of forced convection heat transfer?

Accepted Answer

Cooling electronic components

Answer

Heating water in a boiler

Answer

Natural ventilation of a room

Answer

Melting ice on a sidewalk

Question 11

In natural convection, the Rayleigh number is a dimensionless quantity that:

Accepted Answer

Combines the Grashof and Prandtl numbers.

Answer

Combines the Nusselt and Reynolds numbers.

Answer

Combines the Fourier and Biot numbers.

Answer

Combines the Stefan-Boltzmann and Kirchhoff numbers.

Question 12

Which of the following is a characteristic of turbulent flow in convection heat transfer?

Accepted Answer

High velocity gradients near the surface

Answer

Low heat transfer coefficients

Answer

Laminar boundary layer

Answer

Steady flow

Question 13

The Prandtl number is a dimensionless quantity that represents:

Accepted Answer

The ratio of momentum diffusivity to thermal diffusivity.

Answer

The ratio of heat transfer by conduction to heat transfer by convection.

Answer

The ratio of the Grashof number to the Nusselt number.

Answer

The ratio of the Rayleigh number to the Péclet number.

Question 14

Which of the following is the primary mechanism of heat transfer in convection?

Accepted Answer

Advection

Answer

Diffusion

Answer

Radiation

Answer

Conduction

Question 15

The dimensionless parameter that characterizes the relative importance of buoyancy forces to viscous forces in natural convection is known as:

Accepted Answer

Grashof number

Answer

Reynolds number

Answer

Nusselt number

Answer

Prandtl number

Question 16

In a boundary layer, the region closest to the surface where the flow is laminar is known as the:

Accepted Answer

Viscous sublayer

Answer

Inviscid layer

Answer

Transition layer

Answer

Turbulent layer

Question 17

The local Nusselt number for convection heat transfer is defined as:

Accepted Answer

Ratio of convective heat flux to conductive heat flux

Answer

Ratio of convective heat transfer to radiative heat transfer

Answer

Ratio of conductive heat transfer to radiative heat transfer

Answer

Ratio of radiative heat transfer to convective heat transfer

Question 18

Which of the following factors does NOT affect the convection heat transfer coefficient?

Accepted Answer

Pressure

Answer

Fluid properties

Answer

Flow velocity

Answer

Surface roughness

Question 19

Which of the following is NOT a type of convection heat transfer?

Accepted Answer

Radiation

Answer

Mixed convection

Answer

Forced convection

Answer

Natural convection

Question 20

Which of the following is a key characteristic of laminar boundary layers?

Accepted Answer

Smooth and orderly fluid flow

Answer

Significant pressure drop

Answer

Large velocity gradients

Answer

High levels of turbulence

Question 21

The Grashof number is a dimensionless parameter used to characterize:

Accepted Answer

The relative importance of buoyancy forces to viscous forces

Answer

The ratio of heat transfer rate to fluid viscosity

Answer

The thickness of the thermal boundary layer

Question 22

The Nusselt number is a dimensionless parameter used to quantify:

Accepted Answer

The ratio of convective heat transfer to conductive heat transfer

Answer

The fluid velocity

Answer

The temperature difference between the fluid and the surface

Question 23

The convective heat transfer coefficient is a parameter that quantifies:

Accepted Answer

The rate of heat transfer per unit area and temperature difference

Answer

The fluid velocity

Answer

The thermal conductivity of the fluid