Energy and Heat Transfer

Energy is applied in the form of heat, light or sound.

If energy, in the form of heat, is applied to a solid, the molecules become excited enough to “loosen” — particles moving faster in more space — effect is the entering of the liquid phase.  Continued application of heat energy will result in a gas or vapour phase.

It is a fact that at the solid-liquid phase boundary, heat energy seems to be absorbed without a rise in temperature for quite a while.  This occurs again at the liquid-vapour phase boundary.

Energy can be transferred by conduction, convection or radiation.

Heating something which creates a rise on a thermometer is known as “sensible heating” (there is no change of moisture content in air).

Heating something, creating an increase of internal energy — but no temperature rise on the thermometer is called “latent heating

Enthalpy (h) is the sum of the sensible heat and the latent heat.

Enthalpy is therefore sometimes known as “total heat“.

Latent heat is the amount of heat necessary to change a quantity of water to water vapour without changing either the temperature or pressure of the air.

When water is evaporated and passes into the air, the latent heat of evaporation passes into the air with the vapour.

Latent heat is removed when water vapour is condensed.

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