Capillary configurations

Hollow-tiber membranes are subjected lo extensile studies lor gaseous separation (e.g.. CO-. 11-. CL. Ny. 1LS. CO. CH4). where the capillary configuration has an advantage over the spiral-wound fiat Hint and plate und-lramc devices. Another significant area of development and commercialization is pervaporation. These membranes are dense, rather than porous. structures. Generally asymmetric composite constructions arc employed with the ulirathin membranes on an open support. 

Figure 11.7 X-ray diffraction equipment in capillary configuration showing from left to right Cu x-ray tube, monochromator to select Cu K-alpha radiation, sample mounted in capillary tube, beam tunnel, and X celerator position sensitive detector. The tube and the detector are scanned through a range of angles (theta) by the goniometer (the device in the background on which they are both mounted), and the XRPD is recorded and stored on a computer for subsequent analysis and processing.

Note that for 9 > 90°, ze is positive i.e., it corresponds to a depression for 9 < 90°, ze is negative and corresponds to a capillary rise. Equation (1.55) can also be derived by a mechanical approach, considering the hydrostatic pressure APh = pgz and the capillary pressure APC. Applying the Laplace equation (1.20) to the capillary configuration with R] = R2 = -r/cos0 (see Figure 1.37), APcis ... 

The capillary membrane module, which is shown schematically in Figure 1.33 (e), consists of a large number of membrane capillaries with an inner diameter of 0.2 to 3 mm arranged in parallel as a bundle in a shell tube. The feed solution is passed down the center of the membrane capillary and the filtrate, which permeates the capillary wall, is collected in the shell tube. The capillary membrane module requires as basic material membranes in a self-supporting capillary configuration, which, when asymmetrically structured, carry the selective... 

In this junction, the central channel delivering the fluid to be dispersed ends upstream of an orifice. From the two sides of the central channel (or the annulus around the central capillary in the case of coaxial glass capillaries configuration, additional streams deliver the continuous fluid. 

A silicon capillary has some advantages over a drawn-glass capillary such as the ability to construct very complex capillary configurations and integrate the structure with total microfabricated systems In addition, a glass capillary cannot have a T-intersection, while this is easily formed in a silicon capillary Manz has fabricated an intersection which possessed a several-nanoliter injection mechanism [3]... 

The measurement of the drop size is compared for different process conditions and capillary configurations. For low gas-Weber number, the drop size increases slightly in all cases. The curves for the completely filled capillaries proceed nearly horizontally up to Weg = 2.3. Afterward, the drop size of fi = 0.9 and F = 1.5 increases and the drop size for fi = 0.33 and V = 3 stays constant. Higher dimensionless viscosities promote the increasing drop size. In case of the threads emerging from open channel flow, a similar trend is identified as the plots in Fig. 22.10 indicate. When comparing drop sizes from completely filled capillaries and open channel flow at similar process condition, it became obvious that the gas-Weber number of sudden drop size growth is considerably lower in case of open channel flow. 

The fluctuations of the local interfacial position increase the effective area. This increase in area is associated with an increase of free energy Wwhich is proportional to the interfacial tension y. The free energy of a specific interface configuration u(r,) can be described by the capillary wave Hamiltonian ... 

Where parameter c is known as the Kozeny constant, which is interpreted as a shape factor that is assigned different values depending on the configuration of the capillary (as a point of reference, c = 0.5 for a circular capillary). S is the specific surface area of the chaimels. For other than circular capillaries, a shape factor is included ... 

The chip micro reactor ([R 6]) was only one part of a complex serial-screening apparatus [20]. This automated system consists of an autosampler (CTC-HTS Pal system) which introduces the reactant solutions in the chip via capillaries. A pumping system (p-HPLC-CEC System) serves for fluid motion by hydro dynamic-driven flow. A dilution system [Jasco PU-15(5)] is used for slug dilution on-chip. The detection system was a Jasco UV-1575 and analysis was carried out by LC/MS (Agilent 1100 series capLC-Waters Micromass ZQ). All components were on-line and self-configured. 

Cross-flow is the usual case where cake compressibility is a problem. Cross-flow microfiltration is much the same as cross-flow ultrafiltration in principle. In practice, the devices are often different. As with UF, spiral-wound membranes provide the most economical configuration for many large-scale installations. However, capillary devices and cassettes are widely employed, especially at smaller scale. A detailed description of cross-flow microfiltration had been given by Murkes and Carlsson [Crossflow Filtration, Wiley, New York (1988)]. 

Air Bacfiflush A configuration unique to microfiltration feeds the process stream on the shell side of a capillary module with the permeate exiting the tube side. The device is run as an intermittent deadend filter. Every few minutes, the permeate side is pressurized with air. First displacing the liquid permeate, a blast of air pushed backward through the membrane pushes off the layer of accumulated solids. The membrane skin contacts the process stream, and while being backwashed, the air simultaneously expands the capillary and membrane pores slightly. This momentary expansion facilitates the removal of imbedded particles. 

FIG. 3 (a) Block schematic of the typical instrumentation for SECM with an amperometric UME tip. The tip position may be controlled with various micropositioners, as outlined in the text. The tip potential is applied, with respect to a reference electrode, using a potential programmer, and the current is measured with a simple amplifier device. The tip position may be viewed using a video microscope, (b) Schematic of the submarine UME configuration, which facilitates interfacial electrochemical measurements when the phase containing the UME is more dense than the second phase. In this case, the glass capillary is attached to suitable micropositioners and electrical contact is made via the insulated copper wire shown. 

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