Glossary of Terms

Changes phase

Substances exist in one of three main phases (solid, liquid or gas). When substances change from one phase to another they may freeze, melt, condense, vaporize, or sublime.

Compression

The reduction in volume of a substance using a mechanical force.

Condensation

When a substance changes from a gas or vapour to a liquid.

Condense

To change from a gas or vapour to a liquid.

Condensing

When a substance changes from a gas or vapour to a liquid.

Conduction

A method of heat transfer. Usually through a solid material.

Convection

A method of heat transfer. High temperature particles rise above lower temperature particles in a liquid or gas. The higher temperature particles carry the heat energy with them.

Critical point

The temperature above which a gas cannot be condensed by raising its pressure.

Dissipate

A physical process by which matter becomes dispersed.

Dissipation

A physical process by which matter becomes dispersed.

Energy

The capacity of a physical system to perform work (measured in units called Joules).

Evaporation

When a liquid changes to a gaseous state to form a vapour.

Expansion

Increasing the volume of a substance, usually a gas.

Expansion device

A component that controls the amount of refrigerant released into the evaporator, sometimes called a metering device.

Expansion valve

A component that controls the amount of refrigerant released into the evaporator, sometimes called a metering device

Fluid

A liquid, gas or vapour.

Freezing

Solidification of the water within food by reduction of temperature.

Gravity

Gravity is a natural force by which all things with mass—like apples—are attracted (or gravitate toward) one another – like the earth.

Heat

Heat is a form of energy which is transferred through radiation, convection or conduction.

Insulation

Material which has a low heat conductivity and is used to reduce the transfer of heat.

Latent heat

The heat required to convert a solid into a liquid or vapour, or a liquid into a vapour, without change of temperature.

Phase change

Substances exist in one of three main phases (solid, liquid or gas). When substances change from one phase to another they may freeze, melt, condense, vaporize, or sublime.

Power

The rate of production or creation of energy, usually measured in units of joules/sec, Watts (Btu/h).

Pressure

The physical force exerted on a substance by a fluid in contact with it, usually measured in units Pascal (bar, psi). A force exerted over a specified area.

Pressure, absolute

The physical force exerted on a substance by a fluid in contact with it, usually measured units Pascal (bar abs, psia).

Pressure, gauge

The difference in pressure between that of the substance and standard atmospheric pressure, units bar gauge (psig).

Radiation

Transfer of energy by electromgnetic waves which may tavel through space or a material.

Refrigerant

A substance used in a mechanical circuit to create cooling or heating of a product or space.

Sir Isaac Newton

English scientist (1642-1727).

Sublimation

Sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase.

Temperature

The degree or intensity of heat present in a substance, measured according to a recognised scale, units °C (°F).

Temperature, absolute

The degree or intensity of heat present in a substance, measured from absolute zero, units K.

Thermometer

Instrument for measuring temperature.

Torr gauge

This is a gauge used to measure very low pressures, sometimes called a vacuum gauge.

Vaporise

When a liquid changes to a gaseous state to form a vapour.

Vapour

A substance in the gas phase.

Vapour compression

Vapour compression is the wording used to describe the most commonly used mechanical refrigeration cycle for fridges and air conditioning. The refrigerant vapour is compressed by a motor (or compressor) allowing it to condense at high pressure, and reject heat to a higher temperature.

Volume

The amount of space that a substance or object occupies, units cubic metres (cubic feet).

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