Heat Transfer Flashcards
Where does conduction mainly occur
Solids
Where does Convection mostly occur
Liquids and Gases
Where does Radiation mostly occur
Solids, Liquids and Gases
What type of solid is Conduction faster in and why
Denser ones because they’re closer together so collide more
What is conduction
Where vibrating particles pass on their extra kinetic energy to neighbouring particles
Why are metals good conductors
The have free electrons to move around inside the metal.
What are the 3 types of heat energy transfer
Conduction
Convection
Radiation
An object hotter than its surroundings emits…
More radiation than it absorbs
An object cooler than its surroundings emits..
less radiation than it absorbs
The hotter the object the (more/less) radiation it radiates over a given time
More
What are Black/Dark/Matte surfaces good for?
Absorbing infrared radiation
Emitting more infrared radiation
What are light/shiny surfaces good for?
Reflecting infrared radiation
Why do solar panels use back painted pipes/ black surface
Because radiation from the sun is absorbed by the black surface to hear water in the pipes
What is convection
When more energetic particles move from the hotter region to the colder region taking with them their heat energy
What are convection currents about
Chances in density
What containers is convection most efficient in and why
Roundish/Squarish
They allow the currents to work best
Name 3 things the rate of hear transfer depends on
Volume
Types of Material
Size of surface area
How does type of material affect the rate of heat transfer
Some are good conductors so transfer heat quicker
How does size of SA affect rate of heat transfer
Bigger surface area = more infrared waves being emitted
How does Volume affect rate of heat transfer
Smaller volumes will cool quicker because a higher proportion of object will be in touch with its surroundings
Give 4 ways a vacuum flask is adapted to stop hear loss
- Insulating foam
- Double walled with vacuum between
- Silvered walls
- Plastic stopper
How does silvered walls stop heat loss in a vacuum flask
Keeps heat loss by radiation at a minimum
How does insulating foam affect heat loss in a vacuum flask
Minimises conduction to or from the outer glass bottle
How does a double walled glass bottle affect heat loss in a vacuum flask
Stops conduction and convection through sides
How does a plastic stopper affect heat loss in a vacuum flask
reduces heat conduction through it
