TY  - CHAP
A1  - Mesenhöller, Eva
A1  - Jacobs, Steffen
A1  - Vennemann, Peter
A1  - Hussong, Jeanette
T1  - Unsteady Ventilation in a Scaled Room Model with Swirl Ceiling Diffusers
T2  - CLIMA 2022 conference
N2  - Mechanical ventilation of buildings is generally based on steadily operating systems. This field is well known and established. But, an approach based on time-varied supply flow rates might improve indoor air quality, comfort, and energy consumption. Typical time-scales of the variation are in the order of seconds or minutes. Until now, the effects of unsteady ventilation scenarios are not fully described and so, reliable dimensioning rules are missing. Hence, with a better understanding of the flow in unsteady ventilation, systems can be calculated and optimised. To understand the effective mechanisms and derive functional relations between the flow field and variation parameters, full-field optical flow measurements are executed with a particle image velocimetry (PIV) system. Experiments are conducted under isothermal conditions in water in a small-scale room model (1.00 m × 0.67 m × 0.46 m) with two swirl ceiling diffusers, Reynolds-scaling assures similarity. In a series of experiments, the effects of different unsteady ventilation strategies on the flow fields are investigated and compared to steady conditions with the same mean exchange rate. Mean exchange rates, signal types, periods, and amplitudes are varied. Time-averaged normalised velocity fields already indicate notable differences between steady and unsteady cases especially for lower exchange rates: the distribution is more homogeneous in unsteady scenarios compared to steady conditions, and low-velocity areas are reduced while the mean velocity of the room increases. So, unsteady ventilation might be beneficial in terms of improved ventilation and energy savings in partial-load operation. Fast Fourier Transformation (FFT) analyses of the mean velocity for each field over the whole series detect the main frequency of the volume flow variation. By dividing the velocity field into smaller areas, this main frequency is still detected especially in the upper part of the room, but side frequencies play a role in the room as well.
KW  - unsteady ventilation
KW  - PIV
KW  - room airflow
KW  - mixing ventilation
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-151811
UR  - https://proceedings.open.tudelft.nl/clima2022/article/view/200
PB  - TU Delft OPEN
CY  - Delft
ER  - 
TY  - CHAP
A1  - Jacobs, Steffen
A1  - Mesenhöller, Eva
A1  - Jakirlic, Suad
A1  - Vennemann, Peter
ED  - Hanjalic, K.
ED  - Borello, D.
ED  - Suga, K.
ED  - Venturini, P.
T1  - Computational Study of Transient Indoor Airflow with Reference to a Complementary Experiment
T2  - Proceedings of the Tenth International Symposium On Turbulence, Heat and Mass Transfer. K. Hanjalic, D. Borello, K. Suga, P. Venturini (Eds.)
N2  - A novel approach for ventilation systems is a periodically varying supply air flow rate, the so-called unsteady mode of operation. So far, useful effects of this unsteady operating mode have been observed, but the effect mechanisms are still unknown. In this manuscript, simulations using the recently proposed k-ω-ζ - f model implemented in a sensitized RANS computational framework for a cuboid room with swirl diffusers are compared and validated with PIV measurements.
Y1  - 2023
SN  - 978-1-56700-534-9
SN  - 2377-2816
SP  - 681
EP  - 684
PB  - Begell House Inc.
CY  - New York, Wallingford
ER  -