Porous cylinder

The major dasses of antibiotics are secondary metabolic products of micro-organisms. Many were discovered by empirically screening culture filtrates or cell extracts for antimicrobial activity. A range of techniques (examples are methods using, impregnated discs, porous cylinders, cut wells, see Figure 6.2) have been used to carry out such screening. 

Beginning with the innovative work of Tsuji and Yamaoka [409,411], various counter-flow diffusion flames have been used experimentally both to determine extinction limits and flame structure [409]. In the Tsuji burner (see Fig. 17.5) fuel issues from a porous cylinder into an oncoming air stream. Along the stagnation streamline the flow may be modeled as a one-dimensional boundary-value problem with the strain rate specified as a parameter [104], In this formulation complex chemistry and transport is easily incorporated into the model. The chemistry largely takes place within a thin flame zone around the location of the stoichiometric mixture, within the boundary layer that forms around the cylinder. 

Fig. 17.5 Illustration of the Tsuji and Yamaoka diffusion flame in the forward stagnation region of a porous cylinder [410,411].

G. Dixon-Lewis, T. David, P.H. Gaskell, S. Fukutani, H. Jinno, J.A. Miller, R.J. Kee, M.D. Smooke, N. Peters, E. Effelsberg, J. Wamatz, and F. Behrendt. Calculation of the Structure and Extinction Limit of a Methane-Air Counterflow Diffusion Flame in the Forward Region of a Porous Cylinder. Proc. Combust. Inst., 20 1893-1904, 1984. 

H. Tsuji and I. Yamaoka. The Structure of Counterflow Diffusion Flames in the Forward Stagnation Region of a Porous Cylinder. Proc. Combust. Inst., 12 997-1005,1969. 

We analyze, within a linearized second gradient theory, the static infinitesimal deformations of an annular porous cylinder filled with an inviscid fluid and with the inner and the outer surfaces subjected to uniform external pressures pj xt and iff1 respectively. We assume that surface tractions on the inner and the outer surfaces of the cylinder, in the reference configuration, equal -po and postulate that... 

Platinum catalyst was introduced into an alumina-based suspension and then spray-coated. The evaporation was performed using porous cylinders of 7 mm diameter and 1 mm height introduced into each individual plate before performing... 

Consider the double-layer interaction between two parallel porous cylinders 1 and 2 of radii and a2, respectively, separated by a distance R between their axes in an electrolyte solution (or, at separation H = R ai—a2 between their closest distances) [5]. Let the fixed-charge densities of cylinders 1 and 2 be and Pfix2. respectively. As in the case of ion-penetrable membranes and porous spheres, the potential distribution for the system of two interacting parallel porous cylinders is given by the sum of the two unperturbed potentials... 

Note that the following exact expression for the electrostatic interaction energy per unit area VcyniH) between two porous cylinders for the low charge density case has been derived [5,10] (Chapter 13) ... 

The influence of the liquid level above the porous coating is important at h less than approximately 2 mm at low heat fluxes. In this case the heat transfer coefficients were higher than at a high liquid layer above the tested sample. The data obtained on flooded (h = 70, 20 mm) and partially flooded (h= 15, 10, 5 mm) porous cylinder are presented in Figure 4. 

The process inside a sintered powder porous body is similar to the processes inside micro heat pipes (Figure 7) with zone of evaporation and condensation. If the tested sample is placed in liquid pool, we have micro heat pipe closed type (Figure 7, a), for partially flooded porous cylinder we have the surface with micro heat pipe open type (Figure 7, b). 

Awad, M.L, Saleh, M.M., and Ohsaka, T. 2008. Oxygen reduction on rotating porous cylinder of modified reticulated vitreous carbon. Journal of Solid State Electrochemistry 12, 251-258. 

Problem 3-28. Rotating Porous Cylinder. A circular cylinder of radius a rotates at a constant angular velocity il and generates a flow exterior to the cylinder, i.e., in aboundary conditions on the cylinder surface are... 

Note that in [523], a similar plane problem on an arbitrary linear shear flow past a porous cylinder was solved. The flow outside the cylinder was described by using the Stokes equations and the percolation of the outer fluid inside the porous cylinder was assumed to obey Darcy s law (2.2.24). The amount of the fluid penetrating into the cylinder per unit time was determined. 

The Norton filters included an original design (tube) filter element and an improved design (lumen) filter element. Overall dimensions of both filter elements were 2.1 cm diameter by 40.2 cm length. The tube element consisted of a bundle of 28 porous tubes and the lumen element consisted of a porous cylinder with 19 tubular channels or lumens extending the length of the cylinder. The filter membrane comprised of the inner surface of the tubes or lumens and had a smaller pore diameter than the non-membrane portions of the filter. Inside diameter of both tubes and lumens was 2.8 mm resulting in a total membrane area 0.091-m2 (1 ft2) for the tube filter and 0.060-m2 (0.65 ft2)for the lumen filter. Membrane pore diameter was 0.45 (1m for both filters. 

A hollow, porous cylinder 25 mm in OD, 15 mm in ID is fed internally with liquid diethyl ether at 293 K. The ether flows radially outward and evaporates on the outer surface. Pure nitrogen at 373 K and 1 atm flows perpendicular to the cylinder axis at 3 m/s, carrying away the evaporated ether. The ether flow is to be that which will just keep the outer surface of the cylinder wet with liquid. Since mass-transfer rates vary about the periphery, the cylinder will be rotated slowly to keep the surface uniformly wet. Calculate the surface temperature and the rate of ether flow, in kg/h per meter of cylinder length. 

Another novel concept is the Air-Sparged Hydrocyclone developed at the University of Utah. In this device, the slurry fed tangentially through the cyclone header into the porous cylinder to develop a swirl flow pattern intersects with air sparged through the jacketed porous cylinder. The froth product is discharged through the overflow stream. 

Figure 5.24 Cell for simulation of a rotating electrode by rotation of the electrolyte. A special porous cylinder is necessary for the generation of similar streaming conditions, (1) cylinder for regulating the electrolyte flux, (2) disc electrode, (3) magnetic rod, (4) counter electrode, and (5) magnetic stirrer.

Figure 6.18. CVI of silicon carbide from methyl trichlorosilane and hydrogen in a porous substrate. The curves indicate the degree of pore filling after a deposition period (the same period in all cases) (a) Effect of temperature on the amount deposited by CVI in a porous cylinder, (b) Effect of pressure.

TCP and TTCP (porous cylinder) [45 %] Tibia of dogs 10 months TCP resorbed TTCP unchanged 29... 

HAp and P-TCP (ten types of micro and macro porous cylinder) Tibia of rabbits 9 months HAp no resorption TCP more or less degradable 31... 

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