Spiral plate exchanger advantages and disadvantages

Spiral plate Heat exchanger 

Of all the compact exchangers, the spiral is certainly the most unique. For example, all of the above-mentioned types are based on thin-plate technology, with multiple flow paths created by either corrugation of the plates or the use of a fin structure between the plates. They are also designed for very high efficiencies.

A spiral exchanger is a configuration that, in cross section, resembles a watch spring, using two heavy-gage strips of material to create one flow channel for each fluid. It was developed to handle problem fluids, such as those that have severe fouling tendencies or contain solids in suspension.

A novel feature of the exchanger, when laid on its side, is its hydraulics. Rapid changes in cross-sectional geometry perpendicular to flow counteract the settling of suspended particles. The constantly changing direction of the wall also creates higher turbulence than in shell-and-tube units, and limits the amount and rate of scale deposition. In normal configurations, both fluid channels, while welded off from each other, can be easily accessed for cleaning by removal of the heads, without removal of the internals.

Because flow is countercurrent, the spiral can handle very deep temperature crosses and achieve closer approaches than can shell-and-tube exchangers. Service that would normally require several shells stacked in series, can generally be handled in a single spiral. Typical duties include feed-effluent exchangers, slurry exchangers on coke- or catalyst-containing streams, minerals or fibers, and applications where space is limited.

With modification of its internal design, the spiral can also be used as a condenser. In this service, maximum benefit can be obtained if the unit is mounted atop the column. This arrangement is easy to do because of the small size, and allows for running the reflux back by gravity alone. Also, this setup eliminates the overhead and reflux lines, the drum and pump, and the foundations and space required for a grade-mounted unit. The elimination of the ancillary equipment can potentially return a savings several times the cost of the condenser.

Limitations of the spiral are temperature and pressure, with a maximum pressure of 25 bars and 500 degrees Celsius as the top temperature limit. These limits vary, however, depending on the unit's size and material of construction. Volumetric flowrate may also limit use of the spiral exchanger. Because of its single channel, maximum flow is about 350 m³/h, which is generally less than that of shell-and-tube models.