Spiral discs

Figure 3.10 The structure of the spinning disc heat transfer surface. Overall heat transfer coefficient of 10 kW/m K for low viscosity process fluids and water or glycol as heat/cool fluid. A 0.5 m dia disc with deltaT 20K will transfer 39kW, thanks to patented double spiral disc design, copper construction (with chrome plating for corrosion resistance).

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. 

An unknown event disturbed the equilibrium of the interstellar cloud, and it collapsed. This process may have been caused by shock waves from a supernova explosion, or by a density wave of a spiral arm of the galaxy. The gas molecules and the particles were compressed, and with increasing compression, both temperature and pressure increased. It is possible that the centrifugal forces due to the rotation of the system prevented a spherical contraction. The result was a relatively flat, rotating disc of matter, in the centre of which was the primeval sun. Analogues of the early solar system, i.e., protoplanetary discs, have been identified from the radiation emitted by T Tauri stars (Koerner, 1997). 

The molecules being pumped are dragged along the surface, hence the term molecular drag pump. These surfaces can take the form of a rotating spiralled drum (Holweck) or slotted rotor discs (Gaede). 

After filling, the ends of the tubes are closed and moisture is applied in order to soften the said tubes which are then passed between rollers and partially flattened. Each tube is wound into the well known spiral configuration around a wooden or cardboard disc before placing it in a frame so that the firework can be glued without uncoiling and then being allowed to dry. 

A blue touch-paper is applied to the end of the spiral and the central disc drilled to accept a nail or a pin. It is important that anything used to pin the wheel to a post is a good fit in the pivot hole because a tight fit will inhibit rotation, whereas a loose fit will allow the wheel to tip forwards and perhaps catch on the post. 

Even when great care was taken to ensure that the liquid feed was introduced to the disc in an axisymmetric manner with the minimum disturbance, the smooth inner him always broke down into an array of spiral ripples, as shown in Figures 5 and 6. These spiral structures then broke down further until the wave pattern became utterly chaotic, provided that the disc was big enough. It is known that liquid him how over a surface is intrinsically unstable, and the phenomenon has been studied by several workers (3-7). It appears to be qualitatively equivalent to the breakdown of a smoke plume rising from a lighted cigarette, where a chaotic zone is generated about 20 cm above the source. The behavior can also be observed when a liquid him hows over a stationary surface such as a windowpane or a dam spillway. 

In many cases, the solid disc indeed dissolves in a liquid uniformly over the entire surface, as in Fig. 5.2a.309 Sometimes, however, spiral etch patterns reproducing the lines of laminar flow of the liquid299 300 304 are seen on the surface of the disc after its dissolution in the liquid phase. An example is shown in Fig. 5.2b.309 This takes place when the velocity of movement of the solid-liquid interface relative to its initial position exceeds a certain limiting value. 

In the case of kneading elements, the basic module is not axially moved in a spiral, but forms a cylindrical body with parallel axes, a kneading disc. Several kneading discs connected in series form a kneading element. Similar parameters can be defined for these elements ... 

The preferred method for cutting the helical baffles is to use a milling machine with an indexing head and a 1/8" thick disc cutter. The tangent table angle is set to 87 for proper cutter clearance. Depth of cut is set to. 4375". Spiral pitch is. 25" (one turn in. 25"). Gear change (velocity ratio) is 1/40 for machines with a standard pitch of 10 inches. For other machines, use the fol-... 

The objective in membrane design is to pack as much permeation surface area into as small a space as possible to minimize operation requirements. Depending on the application, various membrane designs are used, such as flat sheet, disc tube, hollow fiber, spiral wound, and ceramic (17). Module design has a measurable effect on the hydrodynamic performance of the cross-flow membrane device. The advantages and disadvantages of different membrane modules are summarized in Table 1. 

Spiral or worm stirrers are suitable for agitating the contents of test-tubes and boiling tubes. A large sphere of molten glass is pressed into a thin disc by the method described for type (b). A rod is then attached to the disc and the disc heated in a soft flame and stretched and twisted to the spiral form shown in Fig. 8.5i. The first attempt to make such a spiral may not succeed, but repeated efforts will soon produce surprisingly long and regular worm stirrers. 

In order to carry out this determination, a volume of 1-5 litres of the gas mixture to be examined is passed through a bubbler containing water saturated with aniline. With gas mixtures containing more than 2% phosgene it is necessary to use a second bubbler to absorb any slight traces of phosgene which may escape the first. The precipitate which forms is collected on a small disc of filter paper supported on a spiral of platinum wire in the neck of a funnel. It is washed four or five times with the smallest possible amount of water in order to remove the aniline and then dried in an oven at 50° to 60° C. for 2 hours so that the last traces of aniline are removed. 

Three forces act on the product to produce a fluidization pattern best described as a spiraling helix. The rotation of the disc moves the substrate outward by centrifugal force. The fluidization air accelerates the product up the walls of the product container. Finally, gravity (and possibly turbulent air eddies) causes the particles to tumble inward toward the center of the disc. Typically the nozzle is immersed low in the product bed in a region of high substrate density and speed, and the liquid is sprayed concurrently with the flow of product, though at least one vendor locates the nozzle above the bed, spraying downward onto its surface,... 

For industrial purposes, resistance thermometers are made usually either of platinum or of nickel, the latter material being fairly satisfactory for temperatures below 300 C. In the form of platinum thermometer made by Leeds Northrup Co. about 40 cm. of fine wire is wound upon a mica frame into a spiral coil about 4 cm. in length and 0.7 cm. in diameter. The length of the wire is so adjusted that the resistance of the coil is about 8.3 ohms at 0°C. The frame is made of crossed strips of thin mica notched at the edges to hold the wire in place. From the ends of this coil lead wires of platinum or gold are carried to the terminal head of the thermometer. The lead wires are insulated and held apart by mica discs through which the wires are threaded. 

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