Methods of Heat Transfer

Question 1

Name the 4 modes of heat transfer

Answer 1

• Conduction
• Natural Convection
• Forced Convection
• Radiation

Question 2

Conduction:

Answer 2

Conduction occurs when two different temperature objects are in contact, heat is travelled from one particle to another through collisions.

Question 3

Natural Convection:

Answer 3

Describes the motion of a fluid that is caused by natural forces within it.
- E.x. Buoyancy: Hotter fluid ( less dense) flow to the top, while colder fluid (more dense) sink to the floor. This causes a convection current.

Question 4

Forced Convection:

Answer 4

Describes the motion of a fluid caused by forces outside of it. These forces allow the movement of fluid in an unnatural way to accomodate an individuals needs.

Question 5

Radiation:

Answer 5

Consist of electromagnetic waves which transmit energy from a source to an absorber.
- Does not involve movement of particles.
- Higher the temperature of emitter, the greater the amount of energy it emits
- Higher temp means faster cool down, more energy emits
- Lower temp means warm up, because absorbs more energy.
*Objects can radiate and absorb electromagnetic radiation at the same time.

Question 6

Factors that affect radiation absorption/emission?

Answer 6

Surface area - smooth surface area doesnt absorb or radiate as much as rough surfaces.
Surface colour - light/reflective surfaces dont absorb/radiate much; dark/black surfaces do.

Question 7

What are thermal conductors?

Answer 7

Thermal conductors are materials that readily absorb and allow for the flow of thermal energy.
- Metals are good

Question 8

What are thermal insulators?

Answer 8

A thermal insulator is any material through which thermal energy flows slowly.
- Non-metallic are good