Boyle-Mariotte

The Boyle-Mariotte Law

The Boyle-Mariotte Law, also known as Boyle’s Law, states that the pressure of ideal gases is inversely proportional to their volume at constant temperature and amount of substance. If the pressure on a gas volume is increased, its volume is reduced by the increased pressure. If the pressure is reduced, it expands.

Mathematically, Boyle’s Law is expressed by the formula:
(Approximate formula without considering temperature)

p • V = constant

therefore

p₁ • V₁ = p₂ • V₂

or

p₁/p₂ = V₂/ V₁

where

p₁: initial pressure

V₁: initial volume

p₂: final pressure

V₂: final volume

You can learn how this effect can be used to convert the pressure change in a leak test to the leak rate

Based on the above, the formula for converting flow / pressure change is derived:
(without considering temperature):

p_start • V_start = p_end • V_end + p_leak • V_leak

Since V_start = V_end = V_DUT + V_System = V_Test
and p_leak = 1 bar (ambient pressure), it follows:

V_Test • (p_start – p_end) = V_leak • 1 bar

⇒ V_leak = (V_Test • Δp) / 1 bar

Normalization to flow rate (with test time):

In summary, how this effect can be used to convert the pressure change in a leak test to the leak rate is explained >here<.