Pillow-plate heat exchanger

Pillow plates are manufactured by an inflation process, where two thin metal sheets are spot-welded to each other over the entire surface by laser or resistance welding.

Finally, the gap between the thin metal sheets is pressurized by a hydraulic fluid causing a plastic forming of the plates, which eventually leads to their characteristic wavy surface.

The former commonly form the double walls of jacketed vessels, while the latter are assembled to a stack (bank) to manufacture pillow plate heat exchangers.

The application of pillow plates is very extensive, due to their favorable properties such as high geometric flexibility and good adaptivity to almost every process.

Pillow plate banks are typically used in applications involving liquid-liquid, gas-liquid, high viscosity or dirty media, low pressure loss requirements, condensation (e.g. top condensers), falling film evaporation (e.g. paper & pulp industry), reboilers, water chilling, drying of solids, flake ice generation (food industry) and more.

In contrast to more conventional heat exchangers, knowledge of thermohydraulic performance of pillow plates and experience with their design is limited.

[3] The mentioned geometrical parameters were determined using Finite Element Analysis (FEM), which imitates the inflation process during manufacturing of pillow plates.

The complex wavy geometry in pillow plate channels promotes fluid mixing, which leads to favorable heat transfer rates but is also unfavorable for pressure loss (formation of recirculation regions in the wake of welding spots).