Laminar support

The area of catalyst immobilization has received considerable attention as can be judged from the available literature reviews.[1 30] Immobilization of oxidation catalysts shows intrinsic advantages over other catalysts as the tendency for selfoxidation will decrease. Moreover, complexes with generally low solubility, such as heme-type transition metal complexes, can be dispersed molecularly on supports. It is the aim of the present work to overview the state of knowledge on the immobilization of transition metal complexes using microporous supports, such as zeolites and laminar supports like clays. The wealth of information available for complexes immobilized on LDHs or tethered to the mesopore walls in hierarchically organized oxides will not be dealt with. 

The water evaporation takes place below the evaporator in a substantial laminar flow. Because the entire phenomenon is driven by the heat transfer rate, in order to preserve the quality of the end product it is of the utmost importance to avoid any buildup of product on the wall of the evaporator this action is assured by the internal mechanical features of the evaporator, consisting of a rotating shaft holding a series of movable blades supported by appropriate frames. These rotating blades provide for a strong eddy effect on the fed prod-... 

A link between laminar and turbulent lifted flames has been demonstrated based on the observation of a continuous transition from laminar to turbulent lifted flames, as shown in Figure 4.3.13 [56]. The flame attached to the nozzle lifted off in the laminar regime, experienced the transition by the jet breakup characteristics, and became turbulent lifted flames as the nozzle flow became turbulent. Subsequently, the liftoff height increased linearly and finally blowout (BO) occurred. This continuous transition suggested that tribrachial flames observed in laminar lifted flames could play an important role in the stabilization of turbulent lifted flames. Recent measurements supported the existence of tribrachial structure at turbulent lifted edges [57], with the OH zone indicating that the diffusion reaction zone is surrounded by the rich and lean reaction zones. 

The results reproduced from Ref. [28] and presented in Figure 7.1.9 show that the internal structure of the "flamelets" within the studied flames displays strong departures from both unstretched laminar flamelet and stretched counterflow flamelets. Figure 7.1.9 supports the picture of the perturbed flamelet model recently introduced in Ref. [29]. In this model, depending on the local value of the ratio of laminar flame thickness and... 

Kam, L. and Boxer, S. G. (2003) Spatially selective manipulation of supported lipid bilayers by laminar fiow steps toward biomembrane microfiuidics. Langmuir,... 

To support the institutional pharmacist in preparing IV admixtures (which typically involves adding one or more drugs to large-volume parenteral fluids), equipment manufacturers have designed laminar flow units, electromechanical compounding units, transfer devices, and filters specifically adaptable to a variety of hospital programs. 

To describe the velocity profile in laminar flow, let us consider a hemisphere of radius a, which is mounted on a cylindrical support as shown in Fig. 2 and is rotating in an otherwise undisturbed fluid about its symmetric axis. The fluid domain around the hemisphere may be specified by a set of spherical polar coordinates, r, 8, , where r is the radial distance from the center of the hemisphere, 0 is the meridional angle measured from the axis of rotation, and (j> is the azimuthal angle. The velocity components along the r, 8, and (j> directions, are designated by Vr, V9, and V. It is assumed that the fluid is incompressible with constant properties and the Reynolds number is sufficiently high to permit the application of boundary layer approximation [54], Under these conditions, the laminar boundary layer equations describing the steady-state axisymmetric fluid motion near the spherical surface may be written as ... 

In turbulent flow, the edge effect due to the shape of the support rod is quite significant as shown in Fig. 6. The data obtained with a support rod of equal radius agree with the theoretical prediction of Eq. (52). The point of transition with this geometry occurs at Re = 40000. However, the use of a larger radius support rod arbitrarily introduces an outflowing radial stream at the equator. The radial stream reduces the stability of the boundary layer, and the transition from laminar to turbulent flow occurs earlier at Re = 15000. Thus, the turbulent mass transfer data with the larger radius support rod deviate considerably from the theoretical prediction of Eq. (52) a least square fit of the data results in a 0.092 Re0 67 dependence for... 

Results of the model for two parameters, i.e., the spatial temperature profile and the mass flux into the reaction zone as a function of gas mass flux are presented in Fig. 8.7. The temperature profile of the solid fuel flame (Fig. 8.7, left) is similar to that of a premixed laminar flame it consists of a preheat zone and a reaction zone. (The spatial profile of the reaction source term, which is not depicted here, further supports this conclusion.) The temperature in the burnt region (i.e., for large x) increases with the gas mass flux. The solid mass flux (Fig. 8.7, right) initially increases with an increase of the air flow, until a maximum is reached. For higher air flows, it decreases again until the flame is extinguished. 

The cordierite extruded monoliths, having 400 square cellsAn, were similar to those used in automobile catalytic converters. However, instead of using an alumina washcoat as in the catalytic converter, these catalyst supports were loaded directly with 12 to 14 wt.% Pt in the same manner as the foam monoliths. Because these extruded monoliths consist of several straight, parallel channels, the flow in these monoliths is laminar (with entrance effects) at the flow rates studied. 

The large fluctuations in temperature and composition likely to be encountered in turbulence (B6) opens the possibility that the influence of these coupling effects may be even more pronounced than under the steady conditions rather close to equilibrium where Eq. (56) is strictly applicable. For this reason there exists the possibility that outside the laminar boundary layer the mutual interaction of material and thermal transfer upon the over-all transport behavior may be somewhat different from that indicated in Eq. (56). The foregoing thoughts are primarily suppositions but appear to be supported by some as yet unpublished experimental work on thermal diffusion in turbulent flow. Jeener and Thomaes (J3) have recently made some measurements on thermal diffusion in liquids. Drickamer and co-workers (G2, R4, R5, T2) studied such behavior in gases and in the critical region. 

As filtration proceeds, a porous cake of solid particles is built up on a porous medium, usually a supported cloth. Because of the fineness of the pores the flow of liquid is laminar so it is represented by the equation... 

The classical view is that a turbulent flame is equivalent to a distorted and wrinkled laminar flame. The turbulent flame brush is thus supposed to be an integrated picture of a rapidly fluctuating surface, and instantaneous schlieren pictures seem to support this interpretation 50). Grumer, however, has shown that schlieren snapshots of turbulent hot gas issuing from a Bunsen burner look very much like the flame pictures (34) the implication is that one sees, not the instantaneous flame surface, but the boundary of the hot gas. 

Changing the initial mixture temperature affects stability. U0 for blow-off from burners increases with approximately the square of the absolute temperature, whether the flow is laminar or turbulent (17). The exact dependence on temperature is a function of fuel type and concentration, and may also be affected by wall temperature. The flash-back velocity is even more sensitive to temperature (17), so that raising the temperature may actually decrease the relative range of flow velocities that will permit stable flames on burners. As to supported flames, the correlations in Table IV show that blow-off in such systems is less dependent on initial temperature than is blow-off from burners (38) the exponent on 7 > is only 1.2, as compared with 2.0. 

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