Lecture 03

Question 1

What are the three modes of heat transfer?

Answer 1

Conduction, convection, thermal radiation

Question 2

Is heat flow a vector or scalar? Why?

Answer 2

Vector because heat flows in all directions

Question 3

What is the rate equation for conduction?

Answer 3

qsubCOND=kA(deltaT)/L

Question 4

What is the conduction heat flux equation?

Answer 4

q’‘subCOND=k(deltaT)/L or qsubCOND/A

Question 5

What are the units for heat flux?

Answer 5

W/m^2

Question 6

What are the units for the proportional constant in conduction?

Answer 6

W/K*m

Question 7

What is the one important difference between conduction and convection?

Answer 7

Convection does have a bulk motion while conduction does not.

Question 8

What can the medium be for convection?

Answer 8

It must be a fluid

Question 9

What’s an example of convection?

Answer 9

Fan blowing or wind

Question 10

What’s an example of conduction?

Answer 10

Metal spoon entering a hot cup of coffee.

Question 11

What is the formula for convective heat flow rate?

Answer 11

qsubCONV=hA(TsubS-TsubINF)

Question 12

What is the formula for convective heat flux?

Answer 12

q’‘subCONV=h(TsubS-TsubINF) or q’‘subCONV=qsubCONV/A

Question 13

What is thermal radiation?

Answer 13

Energy emitted by matter that is a nonzero temperature

Question 14

What is emissive power?

Answer 14

q’‘subTR=E, aka Thermal Radiation emission rate

Question 15

What’s the formula for emissive power?

Answer 15

E=(epsilon)(sigma)(TsubS)^4; Epsilon is imessivity, no units; Sigma is Boltzmann constant, 5.6710^-8 W/(m^2K^4)