Plate-Fin Exchangers

The brazed plate-fin exchanger consists of stacked corrugated sheets (fins) separated by flat plates, forming passages that are closed by bars, with openings for the fluid inlet and outlet (Figures 12 and 13). 

FIGURE 11 Exploded view of one layer of a plate-fin exchanger before brazing. 

Design of the plate-fin exchanger involves selecting a geometry and surface arrangement that will give a product U A of the correct magnitude to satisfy the relation ... 

Plate-fin exchangers provide a very large heat transfer surface per unit volume and are relatively inexpensive per unit area. They are not mechanically cleanable and are ordinarily used only with very clean fluids. This combination of properties fits them very well for a wide variety of cryogenic applications, such as air separation helium separation, purification, and liquefaction liquefied natural gas production and separation of light hydrocarbons. They are also used in higher-temperature gas-to-gas services. 

Types of Heat Exchangers 188 Plate-and-Frame Exchangers 189 Spiral Heat Exchangers 194 Compact (Plate-Fin) Exchangers 194 Air Coolers 194... 

The demethanizer is designed for complete separation of methane from ethylene and heavier components. The demethanizer is normally operated at approximately 7 atm. The demethanizer overhead consists of methane, plus relatively small amounts of hydrogen, carbon monoxide, and traces of ethylene. Brazed aluminum plate-fin exchangers are used for the multipass cryogenic heat-transfer services. Some ethylene plants employ high pressure demethanizers operated at approximately 35 atm. They are generally combined with either a front-end deethanizer or depropanizer. 

Plate-Fin Exchangers. This type of exchanger has corrugated fins (having triangular and rectangular cross sectional shapes most common) sandwiched between parallel plates (referred to as plates or parting sheets), as shown in Fig. 17.10. Sometimes fins are incorpo-... 

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