Method development for experimental determination οf key fluid-mechanical parameters of haemo-catharsis modules
Haemo-catharsis (HC) modules comprise the cylindrical fiber-bundle section and two flow inlet/outlet headers. Available models ignore the substantial pressure-drop (varying non-linearly with flow-rate) in the headers, while employing linear pressure-drop expressions for the entire module, which lead to erroneous assessment of HC-module performance/characteristics. The novel method reported herein to address this issue, enables reliable determination of key HC-module fluid-mechanical parameters. In specially designed facility, accurate pressure measurements are made (for typical flow-rate ranges) under carefully selected inlet/outlet flow-modes. Fitting a mechanistic model to appropriate pressure-difference versus flow-rate data, allows determination of four parameters ζi associated with pressure-drop in headers (for inlet-/outlet-fluid flow), two friction-coefficients for laminar flow in fiber-lumen and shell-side, plus the hydraulic membrane-permeability. Applying this method to a typical commercial high-flux HC-module, realistic values are obtained of membrane-permeability and friction-coefficients, whereas the magnitude of coefficients ζi manifests the significance of pressure-drop in the headers. Friction-coefficient predictions by a theoretical model applicable to the main HC-section, compared to experimentally-determined values, show weaknesses of the former whereas the latter can reliably account for particular geometric/morphological features of real HC-modules. Further testing of the method is recommended, while its adaptation to a comprehensive model for HC-module performance simulation is in progress.