Our solutions
Atlas Copco Rental
Solutions
Udlejningsflåde
Atlas Copco Rental
Nitrogen generatorer
Udlejningsflåde
Oliefrie luftkompressorer
Udlejningsflåde
Oliefrie luftkompressorer
Oliefrie luftkompressorer
Oliesmurte luftkompressorer
Udlejningsflåde
Oliesmurte luftkompressorer
Oliesmurte luftkompressorer
Tilbehør
Udlejningsflåde
Brancher, der anvender vores løsninger
Atlas Copco Rental
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Compressors
Solutions
Produkter
Compressors
Process Gas and Air Equipment
Stort udvalg af kondensatbehandlingsløsninger til industrielle formål
Produkter
Stort udvalg af kondensatbehandlingsløsninger til industrielle formål
Stort udvalg af kondensatbehandlingsløsninger til industrielle formål
Stort udvalg af kondensatbehandlingsløsninger til industrielle formål
Stort udvalg af kondensatbehandlingsløsninger til industrielle formål
Service og reservedele
Compressors
Maksimer din effektivitet
Service og reservedele
Maksimer din effektivitet
Maksimer din effektivitet
Maksimer din effektivitet
Maksimer din effektivitet
Trykluftkompressordele
Service og reservedele
Trykluftkompressordele
Trykluftkompressordele
Trykluftkompressordele
Industriværktøj og systemløsninger
Solutions
Brancher, der anvender vores løsninger
Industriværktøj og systemløsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Brancher, der anvender vores løsninger
Produkter
Industriværktøj og systemløsninger
Bearbejdende værktøjer
Produkter
Bearbejdende værktøjer
Bearbejdende værktøjer
Bearbejdende værktøjer
Bearbejdende værktøjer
Bearbejdende værktøjer
Bearbejdende værktøjer
Trykluftmotorer
Trykluftstilbehør
Produkter
Trykluftstilbehør
Trykluftstilbehør
Industriværktøj og systemløsninger
Vacuum solutions

Gas Flow Through Pipes and Throttling

Thermodynamics Basic Theory Compressed Air Wiki Physics of Air Compressors

One very interesting branch of physics is thermodynamics, especially for getting insight in air compressors. In this article we are talking about gas flow and throttling, following up on our introduction to thermodynamics.

The Reynolds number

formula reynolds number, calculation

The Reynolds number is a dimensionless ratio between inertia and friction in a flowing medium.
It is defined as:

What are the different types of flow in a pipe?

gas flowing through pipe

In principal, there are two types of flow in a pipe. With Re <2000 the viscous forces dominate in the medium and the flow becomes laminar. This means that different layers of the medium move in relation to each other in the proper order. The velocity distribution across the laminar layers is usually parabolic shaped.

With Re≥4000 the inertia forces dominate the behavior of the flowing medium and the flow becomes turbulent, with particles moving randomly across the flow. The velocity distribution across a layer with turbulent flow becomes diffuse.

In the critical area, between Re≤2000 and Re≥4000, the flow conditions are undetermined, either laminar, turbulent or a mixture of the both. The conditions are governed by factors such as the surface smoothness of the pipe or the presence of other disturbances. To start a flow in a pipe requires a specific pressure difference to overcome the friction in the pipe and the couplings. The amount of pressure difference depends on the diameter of the pipe, its length and form as well as the surface smoothness and Reynolds number.

What is the Joule Thomson effect?

When an ideal gas flows through a restrictor with a constant pressure before and after the restrictor, the temperature remains constant. However, a pressure drop occurs across the restrictor, through the inner energy being transformed into kinetic energy. This is the reason for which the temperature falls. For real gases, this temperature change becomes permanent, even though the energy content of the gas remains constant. This is called the Joule-Thomson effect. The temperature change is equal to the pressure change across the throttling multiplied by the Joule-Thomson coefficient.


If the flowing medium has a sufficiently low temperature (≤+329°C for air), a temperature drop occurs with the throttling across the restrictor, but if the flow medium is hotter, a temperature increase occurs instead. This condition is used in several technical applications, for example, in refrigeration technology and in separation of gases.


Related articles

an illustration about a basic theory article in the atlas copco air wiki

How is Heat Transferred?

To understand the workings of compressed air, a basic introduction to physics can come a long way. Learn more about thermodynamics and how they are vital in understanding how air compressors work.

an illustration about a basic theory article in the atlas copco air wiki

Changes in State for Gases

To understand the workings of compressed air, a basic introduction to physics can come a long way. Learn more about thermodynamics and how they are vital in understanding how air compressors work.