Experimental temperature profiles and biological kill data from dead-ended tubes of various diameters and lengths commonly used in biotechnology applications were compared to those predicted by a finite element model for steam-in-place (SIP) sterilization at 122°C. Diameter was shown experimentally and numerically to have a significant effect with larger diameter tubes exhibiting greater buoyant driven convective flow and more rapid sterilization. The overall Grashof number was shown to be the significant parameter relating magnitude of convective flow to tube diameter and varied as the diameter cubed. Analysis of air/steam mixture flow patterns showed air displacement from 0.4 cm diameter tubes to be due primarily to molecular diffusion, whereas 1.0 and 1.7 cm tubes showed a two-stage convective flow pattern. There exists a critical diameter of 0.4 cm below which SIP sterilization due to buoyancy driven flow does not occur and steam bleeders should be used.
All Science Journal Classification (ASJC) codes
- Applied Microbiology and Biotechnology