Gas Flow Through Cracks

Nitrogen flow through 13 idealized cracks has been measured and compared with theoretical predictions. Gas conditions covered upstream pressure and temperature ranges of between 10 and 50 bars and 277 and 295°K, respectively, exhausting to atmosphere. Hydraulic smooth, convergent and parallel cracks and rough parallel cracks were tested for depths varying from 6 to 810 μm. The effect of area change is adequately predicted from theory if a friction factor Reynolds number relationship is assumed. The remaining data are presented on the basis of a friction factor, Reynolds number, and hydraulic diameter/surface roughness parameter basis. Theoretical predictions are successful where roughness and flow are high enough for the results to be in the completely turbulent regimes. For the hydraulic smooth parallel cracks the flow is lower than predicted for laminar and turbulent flow and this discrepancy will be the subject for further investigations.