Influence of the main parameters of a parallel-plate dialyser under laminar flow conditions
A mathematical model describing the mass transfer in a parallel-plate dialyser with co-current laminar flow in both channels based on the Navier-Stokes equations and Fick's second law was developed. Numerical solutions are presented for pulse- and stepwise concentration changes of the solute in one of the channels using the Laplace transform technique. By simulation the influence of the main design and operational parameters of the dialyser and the most important physical constants for the mass transfer process were investigated. Conclusions with regard to optimum design and operation were drawn and some possibilities for simplifying the model were established
Numerical Analysis of Mass Transfer in Countercurrently Parallel-Flow Rectangular Dialyzer with Internal Recycle for Improved Performance
The effect of mass transfer in parallel-flow rectangular dialyzers with internal recycle has been investigated. In contrast to the same size device without recycle, considerable improvement in performance is achievable if one of the flow channels, either retentate phase or dialysate phase, is divided into two subchannels of same width (w/2) with one performed as the operating subchannel and the other as the reflux cochannel, which provides the increase in the fluid velocity, resulting in reduction of mass-transfer resistance. The improvement by recycle operation increases both the flow rate of liquid and reflux ratio with negligible amount of hydraulic-dissipated energy.
Influence of the main parameters of single-line flow-injection systems without chemical reaction on the output signal
Abstract Single-line flow-injection systems with valve, hydrodynamic, syringe or delta-function injection of the analyte are considered. Appropriate equations for calculating the Peclet numbers of their main sections (i.e., the fore-section, the injection section, the reactor, the measurement cell, and the after-section) are described. Two types of reactor with different dispersion characteristics (i.e., straight tube and coiled tube reactors) are considered. The detector is assumed to measure one of three concentrations: (1) the mean concentration in the cross-section of the flow situated in the middle of the measurement cell; (2) the average integral concentration in the whole volume of the measurement cell; or (3) the average integral surface concentration at the inner walls of the measurement cell. Equations for calculating the Laplace transform of the surface and the integral surface concentration, and for the mean and the variance of the corresponding concentration curves are derived. The conclusions made can be used to investigate the influence of the main parameters of single-line flow-injection systems on sample throughput by simulation of the mathematical models.