Comparison of measured leak rates and calculation values for sealing packages

Abstract

It is often necessary to calculate a leak rate from the size of leak hole and vice versa for testing of sealing packages such as foods, medicines and dangerous goods. These calculations are actually rather complicated because the characteristics of the gas flow through the leak hole change depending on the pressure, the gas species, the temperature and the diameter d and length l of the leak hole. In this study, the air flow rate through 12 flow channels with the inner diameter of 5–50 μm and the l/d ratio of 0.72–260 were measured by a pressure change method and compared with the predictions of the equations governing laminar, turbulent, compressible and molecular flow, as well as those of a developed combined governing equation (modified Knudsen equation). The modified Knudsen equation provided good agreement within 20% over the entire range of experimental conditions, including the transition region between laminar and compressible flow.

Tuning the Internal Energy of Ions Produced by Atmospheric and High-Pressure Electrospray by Modulating the Gas Throughput into the First Vacuum Stage

“…In this case, however, it was found that the gas flow could become turbulent from the calculation of Reynolds number. Therefore, the gas throughput, Q , was calculated by the modified Knudsen equation as shown in eq , which is applicable to the whole flow regime Q = Q VL Q TB ( Q CF − Q normalM / 1.235 ) Q VL 2 Q TB 2 + Q TB 2 ( Q CF − Q normalM / 1.235 ) 2 + ( Q CF − Q normalM / 1.235 ) 2 Q VL 2 + Q M 1 + M italicRT normald p̅ η 1 + 1.235 M italicRT normald p̅ η where Q VL , Q TB , Q CF , and Q M are the gas throughputs calculated by assuming lamina flow, turbulent flow, compressible flow, and molecular flow, respectively.…”

“…Therefore, the gas throughput, Q, was calculated by the modified Knudsen equation as shown in eq 2, which is applicable to the whole flow regime. 24…”

How Low Can You Go? Nanoscale Membranes for Efficient Water Electrolysis

“…To illustrate the importance of eliminating large holes or cracks in a membrane, crossover rates were modeled using a modified Knudsen model that accounts for both diffusion and convection of H 2 through cylindrical, gas-filled pinholes of arbitrary diameter (d p ) as depicted in Figure 5a. 23 In Figure 5b, the %CR was modeled as a function of pinhole density and pinhole diameter at a differential pressure of 13.8 bar (14.8 bar partial pressure H 2 at the cathode) for a hypothetical membrane with thickness t m = 100 nm and intrinsic H 2 permeability P Hd 2 = 5 × 10 −10 cm 2 s −1 . At low pinhole densities, the crossover rate approaches the value predicted by Fick's Law, which is below the crossover target.…”

How Low can you Go? Nanoscale Membranes for Efficient Water Electrolysis

“…To illustrate the importance of eliminating large holes or cracks in a membrane, crossover rates were modeled using a modified Knudsen model that accounts for both diffusion and convection of H2 through cylindrical, gas-filled pinholes of arbitrary diameter (dp) as depicted in Figure 5a. 23 In Figure 5b, the %CR was modeled as a function of pinhole density and pinhole diameter at a differential https://doi.org/10.26434/chemrxiv-2024-qp2rs ORCID: https://orcid.org/0000-0002-0550-801X Content not peer-reviewed by ChemRxiv. License: CC BY-NC-ND 4.0 pressure of 13.8 bar (14.8 bar partial pressure H2 at the cathode) for a hypothetical membrane with thickness tm = 100 nm and intrinsic H2 permeability PH2 = 5x10 -10 cm 2 s -1 .…”