Methods of Heat Transfer

Question 1

What is conduction?

Answer 1

Conduction occurs when two objects of different temperatures are in direct contact(touching).

Heat is transferred from one particle to another when those particles collide.

Question 2

Natural Convection:

Answer 2

Natural convection describes the motion of a fluid (liquid or gas) that is caused by natural forces within it.

Hotter parts are less dense so they rise up and colder are more dense so they sink. They continue this cycle forming natural convection.

Question 3

Forced Convection:

Answer 3

Forced convection describes the motion of a fluid that is caused by forces outside of it. These forces often move the fluid faster than or in a different direction to natural convection.

Question 4

Radiation:

Answer 4

Radiation consist of electromagnetic waves which transmit energy from a source to an absorber.

This is the only form of heat transfer that does not involve the movement of particles.

The higher the temperature the emitter, the greater the amount of radiation it emits.

Question 5

Radiation(surroudings)

Answer 5

Objects can radiate and absorb electromagnetic radiation at the same time.

Objects with temperatures higher than their surroundings radiate more energy than they absorb, so they cool down.

Objects with temperatures lower than their surroundings absorb more energy than they radiate so they warm up.

Question 6

Properties of Objects - Radiation

Answer 6

Smooth surfaces don’t radiate or absorb much radiation as rough surfaces do.

Reflective or white surfaces don’t radiate or absorb much, rather dark/black surfaces do.

Question 7

Conductors + insulators

Answer 7

A thermal conductor is any material through which thermal energy flows quickly.

A thermal insulator is any material through which thermal energy flows slowly.