In plain tubes, fluid flow is essentially laminar, and skin friction retards the flow of fluid in
contact with the tube wall. At the same time this outer fluid cools faster and becomes more
viscous, further retarding the flow. The result is a build-up of concentric fluid layers, with
the hot fast-flowing inner fluid surrounded by cooler, slower flowing outer fluid. These outer
layers-boundary layers-insulate the hotter fluid from the cool tube wall resulting in a very
low heat transfer rate.
Wire loop inserts eliminate boundary layers by completely disrupting laminar flow.
The insert is made from a continuous wire which is formed into loops. The loops are spirally
wound around a small diameter rod and solder bonded in place.When installed in a tube the wire
loops keep the fluid in a constant state of turbulence, preventing the formation of thick
boundary layers and continually presenting hot fluids to the cool tube wall.
Even with the viscous fluids at low velocities the wire loop insert provides extremely
efficient mixing giving vastly improved heat transfer. Any pressure loss experienced is
more than compensated for by the increased heat transfer rate.
These wire loop inserts can be solder bonded into any externally finned tube with a variety
of geometries and densities to suit particular heat transfer and pressure loss requirements.