The practice of using colours to determine the temperature of a piece of (usually) ferrous metal comes from blacksmithing. Long before thermometers were widely available, it was necessary to know what state the metal was in for heat treating it and the only way to do this was to heat it up to a colour which was known to be best for the work.
According to Chapman's Workshop Technology, the colours which can be observed in steel are: [1]
| Colour | Temperature [°C] | Temperature [°F] | ||
|---|---|---|---|---|
| From | To | From | To | |
| Black red [note 1] | 426 | 593 | 799 | 1,100 |
| Very dark red | 594 | 704 | 1,100 | 1,299 |
| Dark red | 705 | 814 | 1,300 | 1,497 |
| Cherry red | 815 | 870 | 1,498 | 1,598 |
| Light cherry red | 871 | 981 | 1,599 | 1,798 |
| Orange | 982 | 1,092 | 1,799 | 1,998 |
| Yellow | 1,093 | 1,258 | 1,999 | 2,296 |
| Yellow white | 1,259 | 1,314 | 2,297 | 2,397 |
| White | 1,315+ | 2,397+ | ||
In 1905, Stirling Consolidated Boiler Company published a slightly different set of values: [2]
| Colour | Temperature [°C] | Temperature [°F] |
|---|---|---|
| Red: Just visible | 525 | 977 |
| Dull red | 699 | 1,290 |
| Dull cherry red | 800 | 1,470 |
| Full cherry red | 900 | 1,650 |
| Clear cherry red | 1,000 | 1,830 |
| Deep orange | 1,100 | 2,010 |
| Clear orange | 1,200 | 2,190 |
| White heat | 1,300 | 2,370 |
| White bright | 1,400 | 2,550 |
| White dazzling | 1,500 | 2,730 |
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be transformed, by a connecting rod and crank, into rotational force for work. The term "steam engine" is most commonly applied to reciprocating engines as just described, although some authorities have also referred to the steam turbine and devices such as Hero's aeolipile as "steam engines". The essential feature of steam engines is that they are external combustion engines, where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In general usage, the term steam engine can refer to either complete steam plants, such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine.
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A Stirling engine is a heat engine that is operated by the cyclic expansion and contraction of air or other gas by exposing it to different temperatures, resulting in a net conversion of heat energy to mechanical work.
Robert Stirling was a Scottish clergyman and engineer. He invented the Stirling engine and was inducted into the Scottish Engineering Hall of Fame in 2014.
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Energy recycling is the energy recovery process of using energy that would normally be wasted, usually by converting it into electricity or thermal energy. Undertaken at manufacturing facilities, power plants, and large institutions such as hospitals and universities, it significantly increases efficiency, thereby reducing energy costs and greenhouse gas pollution simultaneously. The process is noted for its potential to mitigate global warming profitably. This work is usually done in the form of combined heat and power or waste heat recovery.
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Boiler design is the process of designing boilers used for various purposes. The main function of a boiler is to heat water to generate steam. Steam produced in a boiler can be used for a variety of purposes including space heating, sterilisation, drying, humidification and power generation. The temperature or condition of steam required for these applications is different, so boiler designs vary accordingly.