Spiral-Plate Exchangers

A spiral-plate exchanger is fabricated from two relatively long strips of plate, which are spaced apart and wound around an open, split center to form a pair of concentric spiral passages. Spacing is maintained uniformly along the length of the spiral by spacer studs welded to the plate. 

Spiral-plate exchangers are fabricated from any material that can be cold worked and welded. Materials commonly used include carbo steel, stainless steel, nickel and nickel alloys, titanium, Hastelloys, and copper alloys. Baked phenolic-resin coatings are sometimes applied. Electrodes can also be wound into the assembly to anodically protect surfaces against corrosion. 

The spiral-plate exchanger usually should not be used when a hard deposit forms during operation, because the spacer studs prevent such deposits from being easily removed by mechanical cleaning. When, as for some pressures, spacer studs can be omitted, this limitation is not present. 

A spiral plate exchanger is illustrated in Figure 9.90 in which two fluids flow through the channels formed between the spiral plates. With this form of construction the velocity may be as high as 2.1 m/s and overall transfer coefficients of 2.8 kW/m2 K are frequently obtained. The size can therefore be kept relatively small and the cost becomes comparable or even less than that of shell and tube units, particularly when they are fabricated from alloy steels. 

Figure 9.90. Spiral plate exchanger (b) with cover removed...

Spiral plate exchangers are usually of two types spiral-plate and spiral-tubes. Very intensive heat transfer can be achieved, with transfer area per unit up to 250 m2. The operation is limited to 20 bars and 400 °C. However, the cost of such devices is high. 

The spiral-plate exchanger is compact 2000 square feet of heat transfer surface can be obtained in a unit 58 inches in diameter with a 72 inch wide plate. 

Pressure drop calculations for more complex geometries of shell and tube exchangers, and for plate and spiral plate exchangers, are given by... 

Spiral-plate exchangers provide high surface densities. The induced secondary flow results in enhanced heat-transfer coefficients, especially for viscous fluids, and reduced sedimentation-type fouling. Spiral-plate exchangers can be easily opened for cleaning by high-velocity water jets. 

Spiral plate exchanger Heat transfer < design stratification caused by faulty... 

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