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Courtesy of ABB Air Preheater, Inc.
Ljüngstrom® rotary regenerative heat exchangers are used in
the power generation industry to recover energy from the exhaust gas and
return it to the cycle. These heat exchangers must operate at a very low
pressure drop in order to make their use economical, and the plate shapes
are selected based on trade-offs between low pressure drop, high heat
transfer, and manufacturing considerations. Traditionally, elaborate testing
has been used to quantify these trade-offs. In order to reduce the time
and expense required to select improved plate designs, ABB has applied
computational fluid dynamics (CFD) simulations to evaluate the performance
of heat exchanger designs.
The flow between a pair of plates was simulated using FLUENT/UNS, and
the heat transfer and pressure loss results were compared to data. Simulations
were done over a range of Reynolds numbers between 2200 and 8200. The
work focused on comparing the accuracy of different grid densities and
turbulence models, especially the near-wall treatment. Based on the comparisons,
the 2 layer k-e model was found to produce the most reliable heat transfer
and pressure loss predictions over the widest range of Reynolds numbers.
Local heat transfer coefficient prediction on the corrugated plate heat
exchanger. The two-layer turbulence model and periodic boundary conditions
in FLUENT/UNS contributed accuracy and efficiency to the simulation.
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