Cold (technology)
As a refrigerant , in the technology of, in particular in the so addressed sub disciplines cooling and refrigeration, a state with a temperature below the ambient temperature , respectively.
The ambient temperature is of particular importance in cooling technology as a reference and limit temperature, since the natural environment (atmospheric air, water, soil) usually serves as a heat sink for the waste heat from cooling processes . According to the 2nd law of thermodynamics , however , heat does not flow “voluntarily” (without exergy supply ) against a temperature gradient between the heat source and the sink. It is therefore not possible with simple methods of cooling, which are based only on a free heat transfer and thus temperature equalization between source and sink, to cool the temperature of the source (here: the object to be cooled) below that of the sink (here: the environment) . If the temperature is to be lowered further, a cooling process must be interposed to maintain the heat flow. Since energy has to be actively used here, it is often said that the cold has to be "generated".
The methods and processes for generating cold are the subject of refrigeration technology (also called cryotechnology at temperatures below −150 ° C ). Various processes based on different physical effects can be considered as cold processes. Most stationary refrigeration processes use cyclic phase changes of a refrigerant in a refrigeration machine .
term
According to the definition of physics and thermodynamics, there is no cold, only heat. The understanding of “cold” as the opposite / absence of heat has nevertheless found its way into technical jargon. Even in technical terminology, however, the term is mostly used vaguely and inconsistently; it can mean both the amount of heat transferred or the heat flow as well as the cooling temperature or the temperature difference to the environment.
literature
- Joachim Dohmann: Thermodynamics of refrigeration systems and heat pumps . 1st edition. Springer-Verlag, Berlin / Heidelberg 2016, ISBN 978-3-662-49109-6 .
- Dieter Schmidt: Lexicon refrigeration technology . 2nd Edition. VDE-Verlag, 2010, ISBN 978-3-8007-3262-3 .
- Klaus Reisner: Expertise in refrigeration technology . 5th edition. VDE-Verlag, 2013, ISBN 978-3-8007-3389-7 .
- Thomas Maurer: Refrigeration technology for engineers . 1st edition. VDE-Verlag, 2016, ISBN 978-3-8007-3935-6
Individual evidence
- ↑ a b Karl Jousten (ed.): Wutz manual vacuum technology . Vieweg + Teubner, Wiesbaden 2010, ISBN 3-8348-0695-1 .
- ^ Hans Dieter Baehr, Stephan Kabelac: Thermodynamics . Springer, 2012, ISBN 978-3-642-24160-4 , in particular Chapter 9 Thermodynamics of heating and cooling ( limited preview in the Google book search).
- ^ A b Klaus Langeheinecke, Peter Jany, Gerd Thieleke: Thermodynamics for engineers
- ↑ Refrigeration technology - introduction to the basics . Danfoss, Offenbach September 2006 ( danfoss.com [PDF]). danfoss.com ( Memento of the original from September 3, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
