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By Fred Meslay, Fluent Europe
Earlier this year, WABCO Automotive UK Ltd., a leading manufacturer of
innovative automotive components, tasked Fluent Europe with comparing
the efficiency of their current air dryer unit against a new design. The
unit is positioned downstream of a commercial vehicle compressor, and
is designed to remove water from the air before it enters the brake system.
The complex geometry and surface grid on the casting walls
The current design includes an inner drying cartridge contained in a
bowl-shaped metal housing, with a complex casting part that feeds the
air to the dryer unit. The dryer is designed to have a condensation effect
when the warm moist intake air comes into contact with the metal outer
bowl of the unit. The new design added additional features on the inner
cartridge that were designed to improve the rate of condensation and thus
the efficiency of the dryer. FLUENT simulations were performed for the
original and new designs, with the objective of comparing the condensation
rates for each on the outer bowl surface. For this purpose, engineers
at Fluent Europe used a user-defined function (UDF) to calculate the condensation
rate on a specified wall.
Pathlines (left) and condensation contours (right) for the original design
Pathlines (left) and condensation contours (right) for the new design
Both designs were meshed with a zonal-hybrid mesh
using Fluent's versatile pre-processor GAMBIT. Hexahedral
and prismatic cells were used in most of the model along
with tetrahedral cells in the more complex casting part.
This allowed good resolution of the finer geometric details.
At the beginning of the project it was not known whether
the casting part would have to be included in the model.
However, the FLUENT results showed that for both designs,
the flow in the air dryer is far from axisymmetric. This
confirmed the need to model the casting geometry without
simplification to make sure the flow profiles into the
actual dryer unit were correctly represented.
The results of the simulations showed that the temperature
in the cartridge of the new design was lower
than in the original design.
The condensation model implemented by Fluent could also be used to study
condensation in many other application areas, including windscreen misting,
throttle valves and air ducts in aircraft engines.
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