Rotating Surfaces

In the EASTMET process iron oxide fines (minus 0.1 mm), pulverized coal, and binder are mixed together and pehetized. The green pehets are heated in a dryer to remove moisture and fed to a rotary hearth furnace, where the pehets are placed on a flat rotating surface (hearth) in an even layer one to two pehets deep. As the hearth rotates the pehets are heated to 1250—1350°C, and the iron oxide is reduced to metallic iron in 6 to 10 minutes. 

Rotary wheels (see Fig. 14-87 ) Liquid is fed to a rotating surface The velocity that determines drop Mechanical complexity of rotating... 

Effect of Fluid Viscosity and Inertia The dynamic effect of viscosity on a rotating liquid slurry as found in a sedimenting centrifuge is confined in veiy thin fluid layers, known as Ekman layers. These layers are adjacent to rotating surfaces which are perpendicular to the axis of rotation, such as bowl heads, flanges, and conveyor blades, etc. The thickness of the Ekman layer 6 is of the order... 

Magneto-Optic Kerr Rotation Surface Magneto-Optic Kerr Rotation... 

Fig. 3. Pentagon-heptagon transformation (a) five-fold rotational surface of C , (b) negatively curved surface created by pentagon-heptagon transformation (c) a part of the remaining surface in creating the torus.

A guarded machine is an open machine in which all openings giving direct access to live metal or rotating parts (except smooth rotating surfaces) are limited in size by the structural parts or by screens, baffles, grilles, expanded metal, or other means to prevent accidental contact with hazardous parts. 

Contrary to RPBRs, in SDRs, intensified heat transfer presents the most important advantage. Liquid reactant(s) are fed on the surface of a fast rotating disk near its center and flow outward. Temperature control takes place via a cooling medium fed under the reaction surface. The rotating surface of the disc enables to generate a highly sheared liquid film. The film fiow over the surface is intrinsically unstable and an array of spiral ripples is formed. This provides an additional improvement in the mass and heat transfer performance of the device. 

The pumping action is due to a high-speed rotating surface that transfers momentum to the gas molecules (see Fig. 1.16). 

We first consider the case of conformational isomerism of 1,3-butadiene, the simplest 4 N pi electron molecule. We will discuss the relative stabilities of three important points on the rotational surface the cis isomer (6 = 0°),thegauche isomer (6 = 45°) and the trans isomer (6 = 180°). We shall focus our attention entirely on the effect of pi interactions on conformational preference. 

Heat transfer characteristics on rotating surfaces Introduction... 

JACHUCK, R. J. J. and Ramshaw, C. Heat Recovery Systems CHP 14 (5) (1994) 475. Process intensification heat transfer characteristics of tailored rotating surfaces. 

Inclusion of the circumferential-momentum equation demands two new boundary conditions on the scaled circumferential velocity W = w/r. At the rotating surface z = 0, W = 2, where Q is the rotation rate (rad/s). Usually the outer flow is considered to have no circumferential velocity, W = 0. In general, there can be a swirl component in the outer flow. However, as discussed in Section 6.7.3, an inlet-swirl velocity can destabilize the flow. For the pure rotating disk situation with a semi-infinite outer environment the pressure-curvature eigenvalue will vanish. However, the eigenvalue is retained in the analysis because it will be needed for the analysis of fixed-gap rotating-disk situations. 

Fig. 6.16 Nondimensional velocity and temperature profiles in a finite gap with a rotating surface. In all cases the Prandtl number is 0.7 and the forced-flow Reynolds number is Rey = 100. The profiles are illustrated for four values of the rotation Reynolds number Re = G1L2/v. The viscous boundary layers are close to the surface. With the exception of the axial velocity, the plots show the range 0 < z < 0.2, with the small insets illustrating the entire gap 0 < z < 1.

A rotating disk acts as a pump, demanding a certain flow rate for a given rotation rate. With a semi-infinite space above the rotating surface, the draw rate as required by the similarity solution is established naturally as... 

The mathematical similarity of the equations is not broken by the starved flow, but there is a physical and mathematical problem. Since the fluid flows radially outward near the rotating surface and flows radially inward further away from the surface, there is a problem in assigning physically meaningful boundary conditions. Where is the radially inward flow coming from and what is its temperature and composition Similarity requires that the velocities, temperature, and composition be functions of z alone. Thus it would be physically hard (probably impossible) to set up the stratified reservoir of fluid required by the similarity. 

The objectives of this phase of the program were to determine the maximum heat transfer coefficient that may be expected with a rotating surface and to devise an inexpensive method of packing such surfaces into a vapor compression still. The model available for this study was the No. 4 Badger-Hickman still, shown in diagrammatic elevation in Figure 5, as received and before various modifications were made. 

This is the Coriolis acceleration, which is imposed on particles moving in a rotating reference frame—e.g., liquids on a rotating surface or winds in the earth s atmosphere. The resultant acceleration experienced by a particle is a combination of the radial and tangential components, making an angle to the radius,... 

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