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Definitions: Heat and Temperature 2
The specific latent heat of vaporisation of a substance
is the amount of heat energy needed to change one kilogram of that substance
from a liquid to a gas without a change in temperature (i.e. at its boiling point.)
The unit of specific latent heat of fusion and of vaporisation is the joule per kilogram (J kg-1)
Conduction is the movement of heat energy through a substance
by the passing on of molecular vibration from molecule to molecule.
There is no overall motion of the substance.
The U-value of a structure is the amount of heat energy conducted per second
through square metre of that structure
when a temperature difference of one degree celcius
is maintained between its ends.
Radiation is the transfer of heat energy from one place to another in the form of electromagnetic waves.
The average amount of the Sun's energy falling per second
perpendicularly on one metre squared of the Earth's atmosphere
is the solar constant.
Its value is about 1.35 kW m-2.
Convection is the transfer of heat through a fluid by means of circulating currents caused by the heat.