Lecture 3 (Quiz) Modes Of Heat Transfer

Question 1

What are the two types of convection? What do they do?

Answer 1

1. Forced convection. With a fan. Like an oven.
2. Natural convection. The natural movement of air.

Question 2

What is the thermal equilibrium and steady state heat transfer. How are the different?

Answer 2

Thermal equilibrium is two surfaces that are the same temperature.
Steady state heat transfer are two surfaces at different temperatures that continue to exchange heat.

Question 3

What is conduction?

Answer 3

The heat transfer of a moving fluid to a surface. If the fluid is not moving, it is considered conduction.

Question 4

What is Fouriers law of heat conduction? What is k?

Answer 4

Fouriers law of heat conduction:

Q conduction = -kA (T2 - T1)/L

K is thermal conductivity

Question 5

Does a surface have volume, mass or energy? Why?

Answer 5

No. A surface does not have volume mass or energy. Since it is 2 dimensional.

Question 6

What is the governing law for heat convection? Hint: someone’s law.

Answer 6

Newtons law of cooling.
Q convection = h x As x (Ts - T alpha)

Question 7

Heat flux is equal to?

Answer 7

Heat flux Vs = Q/A

Question 8

Mass flow rate is equal to density x _________ x __________.

Answer 8

Mass flow rate = density x area x volume

Question 9

What are the two important equations to remember for the fan question?

Answer 9

1. Volume flow rate = mass flow rate / density.
2. Mass flow rate = velocity x area x density.