Key Concepts and People mentioned in the Science of Efficiency pages
1. Concepts
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.
To condense or condensing
To change 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 or 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 of 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 electromagnetic 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.
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).
2. Some key scientists, physicists and engineers
Joule, James 1818-1889 Worked with Lord Kelvin on the nature of heat and discovered the relationship with temperature resulting in the concept of absolute zero.
Newcomen, Thomas 1663-1702 Atmospheric engine using air to condense steam in cylinder which created a partial vacuum and acted on a piston.
Newton, Sir Isaac 1642-1727 Discovered the laws of gravity and laws of motion
Rankine, William John Macquorn developed the proposal of an organic fluid in a reverse steam cycle (with moderate temperatures), suitable for refrigeration.
Stephenson, (George) 1741-1888 Early pioneer who recognised the importance of super heat and made many other changes to steam locomotives
Thomson, William (Lord Kelvin) 1824-1907 worked on the relationship of heat and work amongst many other interests.
Trevithick, Richard 1771 – 1833 invented and built first steam driven ‘locomotive’
Watt, James 1736 – 1819 Improved on Thomas Newcomen's 1712 beam engine by adding a separate condenser