Free and Forced Convection during external flow over Cylinders

Which of the following is the correct definition of convective heat transfer?

• A) Heat transfer by direct contact between two materials.
• B) Heat transfer due to electromagnetic waves.
• C) Heat transfer due to fluid motion.
• D) Heat transfer due to temperature difference within a material.

In which direction does the boundary layer thickness increase during forced convection over a cylinder?

• A) Radially outward from the cylinder surface.
• B) Radially inward towards the cylinder surface.
• C) Axially along the cylinder surface.
• D) None of the above.

A cylinder of radius 0.1 m is exposed to a fluid flow with a velocity of 10 m/s. What is the Reynolds number for this flow? (Assume fluid density of 1 kg/m³ and dynamic viscosity of 0.1 Pa·s.)

• A) 10
• B) 100
• C) 1000
• D) 10000

For natural convection over a cylinder, which of the following factors affect the Nusselt number?

• A) Cylinder diameter.
• B) Cylinder surface roughness.
• C) Cylinder orientation.
• D) All of the above.

A cylinder is subjected to a fluid flow with a velocity of 5 m/s and a temperature of 300 K. The cylinder surface temperature is maintained at 400 K. What is the heat transfer coefficient for this flow if the convective heat transfer rate is 100 W/m²?

• A) 5 W/m²·K
• B) 10 W/m²·K
• C) 20 W/m²·K
• D) 25 W/m²·K

Design an experiment to investigate the effect of fluid velocity on the heat transfer rate during forced convection over a cylinder.

• A) What is the hypothesis for the experiment?
• B) What is the independent variable?
• C) What is the dependent variable?
• D) How will you measure the dependent variable?