Air Circulation A method for natural or forced motion of air
Air Conditioning The simultaneous control of all, or at least the first three, of the following factors affecting the physical and chemical conditions of the atmosphere within a structure: temperature, humidity, motion, distribution, filtration and purification, most of which affect in greater or lesser degrees human health or comfort
Air Conditioning Unit A piece of equipment designed as a specific air treating combination, consisting of means for ventilation, air circulation, air cleaning and heat transfer with control means for maintaining temperature and humidity within prescribed limits
Ambient Temperature The temperature of the medium surrounding an object. In a domestic or commercial system having an air-cooled condenser, it is the temperature of the air entering this condenser
Automatic Self-acting; operation by its own mechanical or electrical mechanism
Baffle A partition used to divert a flow of liquid or vapour
C.O.P. Co-efficient of Power
Capacitor A device made with two conductive plates separated by an insulator or dielectric
Circuit Breaker A device designed to open under an abnormal amount of current flow. The device is not damaged and may be used repeatedly
Compressor That part of refrigerating system which receives the refrigerant vapour at low pressure and compresses it into a lower volume at higher pressure
Condenser A heat transfer device which receives high pressure vapour at temperature above that of the cooling medium, such as air or water, to which the condenser passes latent heat from the refrigerant, causing the refrigerant vapour to liquefy
Condensing unit That part of the refrigerating equipment which operates to return vaporised refrigerant to liquid by condensation
Cycle of Refrigeration A complete course of operation of a refrigerant back to the starting point, measured in thermodynamic terms; also used in general for any repeated process for any system
Dew Point (of air) The temperature at which a specified sample of air, with no moisture added or removed, would be completely saturated. The temperature below which air on being cooled gives up moisture or dew
E.E.R. Energy Efficiency Ratio Efficiency, Mechanical The ratio of output of a machine to the input in equivalent units
Evaporation The change of state from liquid to vapour
Evaporator A device in which refrigerant evaporates while absorbing heat
Heat Exchanger A device used to transfer heat from warm or hot surfaces to colder surfaces. Used to cool liquid going to the evaporator by passing heat to cold vapour leaving the evaporator. Evaporators and condenser are also heat exchangers in fact, if not in name
Heat Pump A system that uses refrigerant to supply both heating and cooling
Humidity, Relative The ratio of water vapour pressure of air compared with the vapour pressure it would have if saturated at its dry-bulb temperature. Very nearly, the ratio of the amount of moisture contained in the air compared with what it could hold at the existing temperature
Liquid Line The tube or pipe which carries the refrigerant liquid from the condenser or receiver of a refrigerating system to a pressure-reducing device
Load Required rate of heat removal
Power The rate of doing work, measured in watts, or kilowatts
Power Factor A comparison of the true power (watts) to the apparent power (volt amps) in an a.c. circuit
Printed Circuit A board on which a predetermined pattern of printed connections has been made
Refrigerating System A combination of parts in which a refrigerant is circulated for the purpose of extracting heat
Short Cycling The starting and stopping of a compressor in rapid succession
Static Pressure Pressure against walls of tube, pipe or duct
Wet-Bulb Temperature The temperature of air as measured by a thermometer with the bulb covered with a water-saturated wick. Equilibrium temperature of water evaporating into air when the latent heat is supplied by the sensible heat of the air