Slides in this set
HEAT IS TRANSFERRED IN THREE
1) Heat energy can be transferred by radiation, conduction or
2) Heat radiation is the transfer of heat energy by infrared (IR)
3) Conduction and convection involve the transfer of energy by
4) Conduction is the main form of heat transfer in solids.
5) Convection is the main form of heat transfer in liquids and
6) Infrared radiation can be emitted by solids, liquids and gases.
7) Any object can both absorb and emit infrared radiation,
whether or not conduction or convection are taking place.
8) The bigger the temperature differences between a body and
its surroundings, the faster energy is transferred by heating.…read more
INFRARED RADIATION EMISSION OF
1) All objects are continually emitting and absorbing
infrared radiation. Infrared radiation is emitted from
the surface of an object.
2) An object that's hotter than its surroundings emits
more radiation than it absorbs (as it cools down). And
an object that's cooler than its surroundings absorbs
more radiation than it emits (as it warms up).
3) The hotter an object is, the more radiation it radiates
in a given time.
4) You can feel this infrared radiation if you stand near
something hot like a fire or if you put your hand just
above the bonnet of a recently parked car.…read more
RADIATION DEPENDS AS AWFUL LOT
ON SURFACE COLOUR AND TEXTURE
1) Dark, matt surfaces absorb infrared radiation falling on
them much better than light, shiny surfaces such as gloss
white or silver. They also emit much more infrared
radiation (at any given temperature).
2) Light, shiny surfaces reflect a lot of the infrared radiation
falling on them. E.g. vacuum flasks have silver inner
surfaces to keep heat in or out, depending on whether its
storing hot or cold liquid.
3) Solar hot water panels contain water pipes under a black
surface (or black painted pipes under glass).
4) Radiation from the Sun is absorbed by the black surface to
heat the water in the pipes.
5) This water can be used for washing or pumped to
radiators to heat the building.…read more