Heat exchangers plate construction

Tonkovich and coworkers [42—47] used packed bed microreactors for the production of hydrogen. The authors constructed a reactor consisting of stacked stainless steel plates for the partial oxidation of methane [42]. The microchannels (which were 254 pm wide, 1500 pm deep, and 35 mm long) were filled with mesoporous silica that was impregnated with rhodium. The reactor plates were sandwiched between two integrated heat exchanger plates. 

Besides microstructured heat exchanger/reactors constructed in the form of plates as shown in Figure 5.1, shell and tube micro heat exchangers are available. An example is shown in Figure 5.6. The heat transfer within the reactor tubes can be estimated with the asymptotic Nu or with Equation 5.12 for short channels. The outer heat transfer coefficient depends on the flow regime, the arrangement of the tubes, and the presence of baffles [8, 13]. For small-scale systems, capillaries submerged in constant temperature baths are commonly used. In this case, the main heat transfer resistance is mostly located at the outer side of the reactor. 

Spiral heat exchangers are constructed by winding two long strip of plate metal around a center to form a spiral body, which then contains two concentric channels. Each channel is welded closed at alternate sides (see Fig. 27.1). Covers are then bolted over each side of the spiral body to complete the unit. When both of these covers are removed, the entire surface area of the exchanger is available for manual cleaning. 

Cowan, C. T, Choosing Materials of Construction for Plate Heat Exchangers, Chem. ng ,June 9 (1975) p. 100. 

When mild steel construction is acceptable and when a closer temperature approach is not required, the tubular heat exchanger will often be the most economic solution since the plate heat exchanger is rarely made in mild steel. 

Figure 1.26 Large-capacity heat exchanger, e g. for use on oil platforms, constructed from diffusion-bonded plate stacks comprising a vast number of millimeter-sized channels. This apparatus was manufactured by Heatric (Poole, UK).

Different from sole combinations of micro devices, this refers to a total system with many functional elements and flow-distribution and, recollecting zones, typically composed of 2-D plate-type architecture. Each of these plates usually has a separate fimction, comprising imit operations and reaction. Frequently, micro mixing and micro heat exchange fimctions and corresponding elements are employed. Often, the system can be composed of different elements resulting in different process flow combinations. Such an approach may be termed a construction kit. 

Figure 7.1-6. Construction details of a high-pressure heat exchanger. Left The connection between shell and the covered plate is not testable right The corrected well testable arrangement [15],...

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,...

Shell Sizes Heat-exchanger shells are generally made from standard-wall steel pipe in sizes up to 305-mm (12-in) diameter from 9.5-mm (%-in) wall pipe in sizes from 356 to 610 mm (14 to 24 in) and from steel plate rolled at discrete intervals in larger sizes. Clearances between the outer tube limit and the shell are discussed elsewhere in connection with the different types of construction. 

The heat recovery heat exchanger is of flat-plate type Fig. 9). This construction was selected because of the low investment costs. Primary flow is moist, nearly saturated exhaust air from the drying silo, The secondary flow is outdoor air, which is used as combustion air and drying air. 

Kumar, H. (1984) Inst Ghent Eng Syni Ser. No. 86, 1275. The plate heat exchanger Construction and design. 

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