A heat exchanger that has a large surface area per unit volume is called a compact heat exchanger. The ratio of the heat transfer surface area to that of a heat exchanger to its volume is called area density 'β'. A heat exchanger with β>700m2/m3 is classified as being compact. Compact heat exchangers constitute a new class of exchangers which emerged as a viable alternative alternate to the conventional shell-and-tube design. As the name implies, a compact heat exchanger accommodates a large heat transfer area in a small volume. Although several types of heat exchangers have been developed, the more important types are the plate-fin heat exchanger and the spiral heat exchangers. The latter includes the spiral-plate and the spiral-tube exchangers.
[...] The heat transfer surface become accessible ( for cleaning or maintenance) when the covers are removed. The spiral plate exchanger has a high thermal efficiency, it operates in truly countercurrent mode. No LMTD correction is required for calculation of effective temperature driving force. No temperature cross occurs. For this reason, a spiral unit can be operated even at a closed temperature approach as low as 20C. A high degree of turbulence is created by ‘secondary flows' and eddies that result from spiral flow path of the fluids. [...]
[...] Both ends of the coils are connected by welding to the manifolds for inlet and outlet liquids. Carbon steel, alloy steel, and alloys of nickel and copper are preferred. The working pressure limit is more than that for the spiral-plate units. Some recent development in plate heat exchangers A number of novel modifications of the PHEs have been made in the recent times. One of these modifications is the welded-plate exchanger in which the filed gasket (the peripheral part of the gasket) is replaced by a welded joint. [...]
[...] APCHE is a super compact heat exchanger. It is built from flat metal plates in which fluid passage are made by the chemical milling technique is similar to that used to prepare an electronic printed circuit board, and hence the name PCHE typically varies from 0.3 to 1.5 mm which is considerably less than that of ordinary PHE. Such a unit offers a heat transfer area ranging from 500 to 2500 m2/cubic m of core volume, which is several times greater than that of gasket PHE, and over an order of magnitude greater than that of shell and tube. [...]
[...] Plate- fin exchanger are about 9 times as compact as conventional as shell- and-tube heat exchangers while providing the same surface area , weigh less than the conventional heat exchangers , and withstand design pressure upto 6MPa for temperatures between 270 to 800°C . Materials Of Construction: The PHEs are considered suitable for virtually all kinds of applications, the limitation being the operating pressure and the acceptable material of construction. The plates are made from thin gauge sheets varying from 0.5 mm to 1 mm in thickness. [...]
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