Crossflows

Crossflows describe fluid motion where velocity components travel across a boundary or surface rather than along it. In engineering practice the term often refers to configurations in which two streams intersect at right angles or obliquely, creating a crossflow between channels, plates, or tube bundles. The geometry can lead to distinct heat transfer and mass transport characteristics compared with parallel-flow arrangements, and is widely used for compactness and simple fabrication.

In heat exchangers, crossflow denotes a setup where one fluid flows perpendicular to another or perpendicular to a bank of tubes or plates. Common in plate-fin and finned-tube exchangers, crossflow can permit compact, air-side cooling or heating but may require higher surface area or additional fins to achieve equivalent effectiveness to counterflow designs. Performance depends on flow distribution, channel geometry, and the Reynolds number of each stream.

In membrane filtration, crossflow (or tangential flow) filtration maintains fluid motion tangential to the membrane surface while a portion permeates through the membrane. This approach minimizes fouling by sweeping deposited material away from the surface, enabling higher fluxes and longer operation between cleanings. It is widely used in water treatment, dairy processing, biotechnology, and pharmaceutical manufacturing.

Crossflow considerations also arise in aerodynamics and process engineering, where flow direction relative to surfaces influences drag, vortex formation, and mixing. Understanding crossflow behavior is essential for designing efficient exchangers, filtration systems, and flow-control strategies.