Condensation centrifugal force

Dehydration. The removal of all (stand-alone) water from a material by one of the following mechanical processes—heating, adsorption, absorption, centrifugal force, condensation, or flash drying. 

Thin-Film Evaporators. There are two types of thin-film evaporators commonly used in industrial appHcations. The first type introduces feed material into the center of a rotating heated conical receiver. Centrifugal force causes the feed to travel to the outer edge of the conical receiver where it is coUected and drawn off as residue. During the process, the heat causes the volatile components to be driven from the feed. These volatile components are condensed on a chilled surface of the evaporator and coUected as distUlate. 

Another advantage of the radial reacrion turbine is that it can be designed to accept condensation in any amount without efficiency deterioration or erosion. This is possible because there are two forces acring on suspended fog particles, the deceleration force and the centrifugal force, and these two forces can be balanced against each other to prevent the droplets from impinging on specially shaped blades. The process is expl ned as follows ... 

In the 1950s Hickman developed a centrifugal vapor compression evaporator for seawater desalination (53). This device consisted of multiple spinning discs. Seawater sprayed on one side of the disc evaporated, while the centrifugal force removed the residue from the plate surface. The vapor was compressed and returned to the opposite side of the plate, where condensation provided the heat for evaporation and the desired freshwater for recovery. Overall heat transfer coefficients of 18 kW/m2-K are about three times higher than those achieved in steam turbine condensers. 

The rate of condensation on a vertical surface is controlled by the force of gravity acting on the condensed liquid film. A consideration of Eq. (11.20) shows for example that for a vertical plate the mean heat transfer rate from the plate with laminar flow in the film is proportional to gw. Attempts have therefore been made to increase condensation rates by using centrifugal forces instead of the gravitational force to drain the condensed liquid film from the cold surface [55], The simplest example of this would be condensation on the upper surface of a cooled circular plate rotating in a horizontal plane. This situation is shown in Fig. 11.23. A Nusselt-type analysis of this situation will be considered in the present section. 

The vaporized glycerine stream passes through the entrainment separator [10] and condenses on the internal U-tube condenser [9]. Droplets of material entrained with the vapor stream impinge on the entrainment separator and flow back to the heated wall through centrifugal force of the rotating assembly. Distillate flows out the distillate outlet [11] and noncondensables flow out through the vacuum outlet [13]. 

Centrifugal evaporators are used on an industrial scale for gentle distillation of temperature-sensitive materials (Fig. 2.49). Here, a thin film is evenly spread on a heated conical plate by centrifugal force. This technique reduces hold-up, contact time and foaming of the liquid on the heated surface considerably. Furthermore, the centrifugal force immediately throws the condensed steam away from the rotor s heating surface (dropwise condensation). This results in a uniformly heated rotor surface with a high overall heat transfer coefficient up to 30,000 kJ/(m h K). This heated evaporation surface is located opposite to a cooled box which results in the distillate removal. 

In order to stimulate condensate motion under zero-G conditions, other forces must replace the gravitational force. This may be done by centrifugal forces, vapor shear forces, surface tension forces, suction forces, and forces created by an electric field. McEver and Hwangbo [133] and Valenzuela et al. [134] describe how surface tension forces may be used to drain a condenser surface in space. Tanasawa [1] reviews electrohydrodynamics (EHD) enhancement of condensation. Bologa et al. [135] showed experimentally that an electric field deforms the liquid-vapor interface, creating local capillary forces that enhance the heat transfer. 

To continue with Laplace s model As the rate of rotation increased to the point where the centrifugal force at the periphery exceeded gravitation, a ring of material separated from the main mass, eventually contracting towards a point. As the process continued, more planets condensed in the outer regions, while the inner region contracted to form the snn. The satelhtes were formed by condensation from the contracting planets. Excess material between the planets turned into comets and meteors. 

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