Quality grade

The quality grade  ν ( gr.ny ) is a measure of the internal losses of a machine and indicates how close a real thermodynamic process is to the theoretical ideal comparison process (e.g. Carnot process , Joule process ) of a machine:

${\displaystyle \nu ={\frac {\eta _{\mathrm {real} }}{\eta _{\mathrm {ideal} }}}={\frac {\frac {P_{\mathrm {ab,real} }}{P_{\mathrm {zu} }}}{\frac {P_{\mathrm {ab,ideal} }}{P_{\mathrm {zu} }}}}={\frac {P_{\mathrm {ab,real} }}{P_{\mathrm {ab,ideal} }}}\leq 1}$

With

• the efficiency ${\displaystyle \eta }$
• the power  P ( : removed,: supplied). ${\displaystyle _{\mathrm {ab} }}$ ${\displaystyle _{\mathrm {zu} }}$

The quality grade is often confused with the efficiency. The difference is that (see formula above):

• an efficiency indicates the ratio of the used (removed) to used (supplied) power or energy ;
  Efficiencies can be formed for the real and for the ideal process;
• the quality level indicates the ratio of actually used to ideally used power;
  the quality grade therefore relates the two efficiencies of the real and ideal process.

The real efficiency is therefore the product of the quality level and the best possible efficiency of the theoretical comparison process:

${\displaystyle \Leftrightarrow \eta _{real}=\nu \cdot \eta _{ideal}}$

For example, the overall quality of today's internal combustion engines is in the range of 80%, while the (real) efficiency is around 45%. He is differentiated in more detail in the grades of combustion, combustion curve, the heat curve and the charge cycle .

In contrast to degrees of efficiency, some degrees of quality can in reality also reach the value 1 for isentropic processes (see also: degree of quality of adiabatic machines ).

Other meanings

Furthermore, the ratio of actual to best possible performance is generally referred to as quality level, e.g. B.

• the quality of braking force and lateral force distribution in automotive technology
• for the assessment of heat exchangers in physics
• as a measure of machine capability or
• the ratio of net to gross fixed assets in business administration.

Individual evidence

1. ↑ ^{a b} Uwe Todsen: Internal combustion engines . Carl Hanser Verlag, 2017, ISBN 978-3-446-45227-5 , pp. 30 ( limited preview in Google Book search).
2. ↑ Otto Kraemer: Construction and calculation of internal combustion engines . Springer-Verlag, 1941, ISBN 978-3-662-37051-3 , p. 12 ( limited preview in Google Book search).
3. ↑ Bert Breuer, Karlheinz H. Bill: Brake manual basics, components, systems, driving dynamics . Springer-Verlag, 2013, ISBN 978-3-322-99535-3 , pp. 14 ( limited preview in Google Book search).
4. ↑ Michael Trzesniowski: Basics of racing car technology, construction, components, systems . Springer-Verlag, 2010, ISBN 978-3-8348-0857-8 , pp. 264 ( limited preview in Google Book search).
5. ↑ F. Bosnjakovic, Karl F. Knoche: Technical Thermodynamics . Springer-Verlag, 2013, ISBN 978-3-642-61496-5 , pp. 171 ( limited preview in Google Book search).
6. ^ Matthias Strunz: Maintenance basics - strategies - workshops . Springer-Verlag, 2012, ISBN 978-3-642-27390-2 , p. 214 ( limited preview in Google Book search).
7. ↑ GERMAN INSTITUTE FOR ECONOMIC RESEARCH (INSTITUTE FOR ECONOMIC RESEARCH). DIW - CONTRIBUTIONS TO STRUCTURAL RESEARCH. Fixed investments and fixed assets in Berlin (West) 1950 to 1965. S. 39 ( limited preview in Google Book search).