Lecture 6

Question 1

List the three forms of heat transfer

Answer 1

Radiation
Conduction
Convection

Question 2

Specify the unit for thermal conductivity, heat transfer coefficient and thermal resistance.

Answer 2

Thermal conductivity [W/mK] lambda
Heat transfer coefficient [W/m2K] h
Thermal resistance [m*K/W] R

Question 3

Explain the concept of fin efficiency

Answer 3

Fin efficiency - The ratio between the heat transfer for the real fin and the heat transfer for an ideal fin

Question 4

Explain what is meant by the thermal efficiency of a heat exchanger.

Answer 4

If the outlet temperature for media 1 is equal to the inlet temperature for media 2, the thermal efficiency is 100%

Question 5

Give two different expressions for the heat exchange in a heat exchanger REVIDERAS