LAL Loftfields Analytical Solutions

Home + About LAL + PDS-6 Pressure Digestion System + Gas Analysis + Gas Flow Regulation + Contact, Impressum

Gasfluss

Gas Flow Regulation

Our technology enables, even at pressure drops of 50 atm, the precise, quick and reliable regulation of extremely low flows (1 ml/min is no problem) with less than 1% deviation. The patented, thermodynamic principle of the regulator uses no moving components.
 


Patent Principle

 The flow channel is a capillary in a plastic polymere (PTFE), which has a quite large coefficient of thermal expansion. This plastic gets a (almost) complete jacket of metal, which has a relatively small coefficient of thermal expansion. When this combination is heated, the expansion of the plastic is directed inwards, thus reducing the diameter of the capillary.

The sensitivity of of flow to the diameter can be appreciated in the Hagen-Poiseuille-law from the 19th century.

Formel


The technical drawing from the patent application shows the principles:

sketch
8 is the capillary
6,7 is the plastic
2 is the metal jacket. The almost
total occlusion of the capillary
is difficult to recognize here!
II is the temperature regulator
or thermostating jacket


The simplicity of the principle is reflected in the unspectacular small number of components!

Ventil
Gas flow regulator


The first set of 4 regulators was develloped for a micro cosmos system at the IBW, Uni Gö (see Gas Analytics). The soil monoliths were given artificial headspaces with different oxygen potentials (0.1%, 0.5%, 1%, 5%).
Although the principle are very simple, the practical application is complicated by factors such as
  • the 4th power of the radius..
  • the Joule-Thompson effect <=> heat <=> coupling.
  • when the valve is almost closed, the remaining open radius in the capillary is extremely sensitive to the slightest further expansion of the plastic. This can only be handled with extremely precise temperature control.
  • the temperature stability of the environment
  • hysteresis when switching from heating to cooling
  • deadtime
The optimal construction concerning isolation, heating, heat loss, preheating and where to control the temperature was quickly obvious. The preemptive software is ingenious! The key is the prediction of a virtual temperature. The combination? Fantastic!

flow regulator
The optimized system in principle

Top of page



Qualities
  • precision: set flowrates can be held over years within 1%.
  • regulation: within 10 minutes from 1 ml/min to 20 ml/min without oscillations or swings.
  • lifetime: your grandchildren will be delighted to inherit it.
  • price: please knock on my door.
And... please excuse my enthusiasm.

Top of page



Performance

 The following graphics demonstrate the preemptive heating software GASDOSI.

Stufen
Stepwise regulated flow of 1, 2, 3, 6, 8, 10 ml/min
and linearly (dV=f(t)) back to 1 ml/min at dP=50 atm.


Detail
A flow change from 1 to 5 ml/min in detail.
Check the heat! Over 4 minutes preemptive!


Top of page



Patent

 The principle of the flow regulator has been patented in Germany (DBP 100 27 379).

Deutschland-Fahne
deutsch 		Home + About LAL + PDS-6 Pressure Digestion System + Gas Analysis + Gas Flow Regulation + Contact, Impressum
Web-Design by Messwert - Sanfte Mess- und Regeltechnik GmbH