A value that describes the ability of a material to conduct heat. The number of BTU that flow through 1 square foot of material, in one hour. It is the reciprocal of the R-Value (U-Value = 1/R-Value).
Coefficient of performance (cop)
A ratio of the work or useful energy output of a system versus the amount of work or energy inputted into the system as determined by using the same energy equivalents for energy in and out. Is used as a measure of the steady state performance or energy efficiency of heating, cooling, and refrigeration appliances. The COP is equal to the Energy Efficiency Ratio (EER) divided by 3.41(2) The higher the COP, the more efficient the device.
Coefficient of utilization (cu)
A term used for lighting appliances; the ratio of lumens received on a flat surface to the light output, in lumens, from a lamp; used to evaluate the effectiveness of luminaries in delivering light.
Coextrusion welding
Welding process that combines both heat and extrusion on materials, which are to be welded through a die.
Coffer
(1) Decorative sunken panel in a vault, dome, ceiling, etc. (2) A chest or strongbox.
Cofferdam
A watertight, temporary structure, for keeping the water from an enclosed area that has been pumped dry so that construction may be done.
Coffered ceiling
Ceiling which has sunken panels in a box-like structure.
Cofiring
The use of two or more different fuels (e.g. wood and coal) simultaneously in the same combustion chamber of a power plant.
Cog
(1) One of a series of teeth on the rim of a wheel, for transmitting or receiving motion by fitting between the teeth of another wheel. (2) A projection on a beam that fits into a corresponding groove or notch in another beam to make a joint.
Cog railway
Railway used on steep inclines which consists of a gearwheel and cogged rail.
