Brazed-plate exchangers
This category covers two completely different types of exchangers, though both are based on what is called thin- plate technology. The first is corrugated plate, which is nearly identical to gasketed plates. The second, plate fin, uses two flat sheets separated by fins arranged roughly perpendicularly to the first two to form each fluid channel.
1.Corrugated-plate type. Made of stainless steel, with either copper or nickel as the brazing materials, corrugated-plate exchangers have successfully penetrated the commercial refrigeration and automotive markets. Generally used in liquid and refrigerant applications, they accommodate a wide range of temperatures, from cryogenic, to more than 200 degrees Celsius.
Because of the brazed construction, the units are not expandable, but get their reputation from their relatively tiny size. Supplied in standard-area sizes, much like the small shell-and-tube exchangers they effectively replace, corrugated plate exchangers range in size from handheld units, to those the size of a suitcase.
2.Plate-fin type. At the other end of the brazed spectrum is the brazed plate-fin exchanger. Constructed of aluminum, the unit can be designed to handle multiple streams, gases, liquids and two-phase systems. The exchanger features low-temperature capabilities that make it suitable for cold boxes in cryogenic service. Use as a compact kettle reboiler is also possible, with thermal and mechanical advantages over shell-and-tube reboilers. However, the upper temperature limit is about 65 degrees Celsius.
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