Finned heat exchangers

Compact brazed aluminum plate-fin heat exchangers can be used in most cryogenic hydrogen purification apphcations. The use of these relatively low cost heat exchangers, combined with low separation energy requirements, results in a highly economical process for hydrogen purification. 

Table 10-40 provides a suggested range of overall heat transfer coefficients, Uq, for actual finned heat exchangers. 

Estimating Overall Heat Transfer Rates, Uq, for Longitudinal Finned Heat Exchangers... 

Siegel, R. and Howell, J. R. Thermal Radiation Heat Transfer, 2nd edn (McGraw-Hill, New York, 1981) Sparrow, E. M. and Cess, R. D. Radiation Heat Transfer (Hemisphere Publishing, New York, 1978) Taylor, M. (ed.). Plate-fin Heat Exchangers Guide to their Specification and Use (HTFS, Harwell, 1987). Tohloukian, Y. S. Thermophvsical Properties of High Temperature Solid Materials (Macmillan, New York. 1967)... 

Lowe, R. E. (1987) Chem. Eng., NY 94 (Aug. 17th) 131. Plate-and-fin heat exchangers for cryogenic service. 

Plate-fin heat exchangers. Another type of plate heat exchanger is the plate-fin heat exchanger. This is illustrated in Figure 15.17. The plate-fin heat exchanger consists of a series of flat plates, between which is a matrix formed... 

The essential features of the earlier commercial models were that the two piston engines were vertically arranged inside the large finned heat exchanger in a static atmosphere of helium with LHe from the Joule-Thomson expansion collecting in the bottom of the dewar. This liquid could be either used in situ or transferred to all external storage dewar. The energy of expansion was absorbed in a crosshead on top of the dewar assembly. 

Plate design, in a reciprocating-plate column, 70 779 Plate diffusers, 26 163 Plate-fin heat exchangers, 73 263 Plate-frame heat exchangers, 73 263 Plate glass, elastic properties, 5 614t Plate heat exchangers, 70 157 73 263-265, 267... 

Fig. 9. Plate heat exchangers (a) plate—frame heat exchanger when hot fluid from the heat source enters the heat exchanger through connections in the stationary frame plate and is channeled over one side of each plate. Cold fluid enters through different frame plate connections and flows on the other side of each plate in a direction opposite to the hot fluid direction. Courtesy of Bell Gosset. (b) Limco model 6502 plate—fin heat exchanger having compact plate—fin aluminum brazed liquid-to-aii construction. The brazed plate—fin construction provides the most efficient heat-exchanger system in terms of size,...

Analysis of Large Dry Cooling Towers with Spine-Fin Heat Exchange Elements... 

Figure 7 The spiral-wound heat exchanger (in front) to be built for the Snohvit LNG processing plant. The cold box measures 15x17 meter (footprint) having a height of 40 meter. The Statoil/Linde heat exchanger is the same type as the heat exchanger used in the Mossel-bay LNG plant in South Africa [17]. The lower tower (right) contains a plate fin heat exchanger for pre-cooling.

Figure 12 Components of a brazed aluminum plate-fin heat exchanger. (From Ref. 12.)...

Figure 13 Plate-fin heat exchangers. (Courtesy of Nordon Cryogenie.)... 

For higher-temperature applications or when aluminum is not acceptable, stainless steel (temperatures up to 700°C) or copper materials can be used. For very high temperatures (gas turbine heat recovery T > 1200°C), a ceramic plate-fin heat exchanger has also been developed (17) (Figure 16). 

In plate-fin heat exchangers, the flow structure depends on the fin geometry. Continuous fins can be assimilated to rectangular channels and the flow is almost identical to pipe flows. For offset strip fins or louvered fins, there is a high degree of mixing (40), and the flow becomes turbulent even at low Reynolds number (Figure 25). 

For plate-fin heat exchangers in single-phase flow, the heat transfer coefficients are related to the developed heat transfer surface, and the area ratio must be taken into account. As related to the projected surface, the overall heat transfer coefficient is very high. Heat transfer and pressure drop can be estimated from correlations (43 44), but these correlations give only an estimate of the performance, because local modification of the fin geometry will affect heat transfer and pressure drop. 

Figure 25 Flow structure in plate-fin heat exchangers.

Vaporization is the most common unit operation to be found in the process industry the use of compact heat exchangers as evaporators began 40 years ago for the concentration of sugar or salt solutions. Nowadays, compact heat exchangers are used in several industrial processes, and this is particularly true for plate-fin heat exchangers, which are closely integrated in distillation and separation processes of natural and industrial gases. In most cases, evaporation takes place in an upward... 

Concerning plate-fin heat exchangers, the design of such units is much more complicated because up to 12 different fluids can flow in the heat exchangers. 

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