Definition of Leak Rate (LR)
Leak Rate according to DIN EN 1330-08
Leak rate is the throughput of p·V per unit of time of a certain fluid thru a leak under specified conditions:
 |
| qL: |
leak rate |
| p: |
pressure |
| V: |
volume |
| t: |
time |
|
| SI-unit: Pa · m3/s |
| typical unit: mbar · l/s |
| 1 Pa · 1 m3/s = 10 mbar · l/s |
| |
|
The specification of the following conditions is absolutely necessary!!!
| pi: |
pressure inside (absolute) |
| pa: |
pressure outside (absolute) |
| Fluid: |
air, He (100%), water, … |
| T: |
temperature |
Why this definition?
The relation between volume and mass (number of molecules) for incompressible fluids (liquids) is clearly given by the density:
 |
| V: |
volume |
| m: |
mass |
| ρ: |
density |
|
For compressible fluids (gases) the volume is strongly depending on the pressure and the temperature by constant mass (number of molecules). Therefore a definition using the mass or the number of molecules is required. Using the gas equation this results in:
oder
 |
| p: |
pressure |
| V: |
volume |
| N: |
number of molecules |
| kB: |
Boltzmann-constant |
| m: |
mass of molecule |
| R: |
gas constant |
| T: |
temperature |
|
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