Renz A, Praß J, Riedel J, Nadler O, Becker S (2018)
Publication Language: English
Publication Type: Conference contribution, Conference Contribution
Publication year: 2018
Conference Proceedings Title: FAN 2018
Event location: Darmstadt
URI: https://www.fan2025.org/archives/fan2018/papers/FAN2018-92-RENZ.pdf
In an effort to develop a new and simple concept for a decentralized
ventilation system a cross flow friction ventilator was investigated.
This friction ventilator consists of multiple circular discs which are
driven by a motor and are rotating centrally in between two ducts (inlet
and outlet duct of the ventilation system). The drag between the disc
surfaces and the fluid induces a countercurrent flow in the two ducts
while the discs also act as a heat exchanger between the two air flows.
While the concept of the friction ventilator met the basic requirements
for volume flow, pressure rise and heat recovery, the hydrodynamic
efficiency found from experiments and simulations was lower than
expected. In this study, we used Laser Doppler Anemometry to investigate
the velocity field at different rotor geometries and operating points.
Furthermore, we investigated the secondary currents in the ducts by
means of numerical simulations in order to explain the low efficiencies.
The velocity field was measured in two areas, where on area of
interest was the section between the discs themselves. The measurements
there concentrated on the buildup of the wall boundary layer and its
development along the disc. The other area was the velocity field up-
and downstream of the friction ventilator.
As a result, we found that the wall boundary layer at the disc
surface is thin compared to the distance between the discs and that a
large part of the flow is only mildly affected by the rotating surfaces.
The LDA measurements showed further that even in optimal operating
points the flow field downstream of the friction ventilator was highly
turbulent and could be non-uniform from disc duct to disc duct,
depending on the rotor design. The numerical investigations showed that
in almost unrestricted operation, secondary currents could be determined
at velocities of up to 20% of the mean main flow velocity, with
secondary currents reaching up to 50% in throttled operation. The
investigations contributed to a better understanding of the velocity
field of this kind of ventilator, also to the optimization of the rotor
geometry and to the flow over rotating discs in general. Although the
flow along the discs and the turbulent areas downstream were measured
thoroughly, further investigations need to be made to fully understand
the energy transfer from the disc to the air flow and the hydrodynamic
losses that occur.
APA:
Renz, A., Praß, J., Riedel, J., Nadler, O., & Becker, S. (2018). Numerical and Experimental Investigation of the Velocity Field in Friction Ventilators. In FAN 2018. Darmstadt.
MLA:
Renz, Andreas, et al. "Numerical and Experimental Investigation of the Velocity Field in Friction Ventilators." Proceedings of the International Conference in Fan Noise, Aerodynamics, Applications and Systems, Darmstadt 2018.
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