Longitudinal cooling

Indirect. steam-tube dryer This is a bare metal cylinder provided with one or more rows of metal tubes installed longitudinally in the shell. It is suitable for operation up to available steam temperatures or in processes requiring water cooling of the tubes. 

Spray Dryers A spray diyer consists of a large cyhndrical and usu ly vertical chamber into which material to be dried is sprayed in the form of small droplets and into which is fed a large volume of hot gas sufficient to supply the heat necessary to complete evaporation of the liquid. Heat transfer and mass transfer are accomphshed by direct contact of the hot gas with the dispersed droplets. After completion of diying, the cooled gas and solids are separated. This may be accomplished partially at the bottom of the diying chamber by classification and separation of the coarse dried particles. Fine particles are separated from the gas in external cyclones or bag collectors. When only the coarse-particle fraction is desired for fini ed product, fines may be recovered in wet scrubbers the scrubber liquid is concentrated and returned as feed to the diyer. Horizontal spray chambers are manufactured with a longitudinal screw conveyor in the bottom of the diying chamber for continuous removal of settled coarse particles. 

Figure 17.7 Section of longitudinally fractured subterranean cooling water line. Note that the crack runs the entire length of the line.

As discussed later, the enclosure of an IPB may carry induced currents up to 95% of the current through the main conductors. Accordingly, the enclosure is designed to carry longitudinal parasitic currents up to 90-95% of the rated current of the main busbars. The cross-sectional area of the enclosure is therefore maintained almost equal to and even more than the main conductors to account for the dissipation of heat of the main conductors through the enclosure only, unless an additional forced cooling system is also adopted. The outdoors part of the enclosure exposed to atmospheric conditions is also subjected to solar radiation. Provision must be made to dissipate this additional heat, from the enclosure. 

Platinised-titanium installations have now been in use for 30 years for jetties, ships and submarines and for internal protection, particularly of cooling-water systems . For the protection of heat exchangers an extruded anode of approximately 6 mm in diameter (copper-cored titanium-platinum) has shown a reduction in current requirement (together with improved longitudinal current spread) over cantilever anodes of some 30% . This continuous or coaxial anode is usually fitted around the water box periphery a few centimetres away from the tubeplate. 

REP, a rod of metal or alloy, referred to as a consumable electrode, is rotated at high speed about its longitudinal axis. Simultaneously, it is melted gradually at one of its ends by a heat source, such as an arc, a plasma, or an electron beam, etc. A thin film of the molten metal is detached from the rod end and ejected from the periphery of the rod by centrifugal force, forming spherical droplets. The atomization is conducted in an inert atmosphere, usually argon. Helium may be used to increase arc stability and convective cooling efficiency of droplets. 

Fig. 8. Longitudinal section of an experimental waste-heat greenhouse in which temperature control in all seasons is provided by evaporation and heat transfer as air passes through a fiber pad soaked with power station cooling water or by heat transfer as air passes through a finned-tube heat exchanger that carries cooling water. A false ceiling provides for recycle of air through the heat-transfer medium. Reproduced by permission (31).

Figure 15.1—Inductively coupled plasma torch. A radiofrequency current (between 27 and 50 MHz) that induces circulation of the electrons in the inert gas drives the torch. The argon serves as an auxiliary gas, a cooling gas and the nebulisation gas. In the upper right is shown an optic device used to collect emitted light in the longitudinal axis of the plasma. Lower down, plasma generated by microwave.

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