Transient three-dimensional CFD modelling of ceiling fans

Babich, Francesco; Cook, Malcolm; Loveday, Dennis L.; Rawal, Rajan; Shukla, Yash

doi:10.1016/j.buildenv.2017.06.039

Cited by 58 publications

(48 citation statements)

References 25 publications

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“…Zhu et al [19] used MRF together with the realizable k-ε model to examine the ceiling fan-driven flow in an environmental chamber. Contrary to these, Babich et al [38] concluded that SST k-ω model is better than the standard k-ε and realizable k-ε models when applying the body force model to ceiling fan simulations. However, the conclusion was drawn when the ceiling fan was simulated by a body force model rather than MRF.…”

Section: Cfd Modelsmentioning

confidence: 96%

“…Because of the complexity of ceiling fan' geometries, it is generally cost-prohibitive to directly model a rotating ceiling fan using the moving mesh method [36,37]. Instead, the body force model (also called momentum method) and multiple reference frame (MRF) method are often applied [36,38]. Bassiouny et al [39] fitted the previous measured data [24] as Dirichlet-type boundary conditions based on the body force model, and predicted the airflow induced by a ceiling fan using the standard k-ε model.…”

Section: Cfd Modelsmentioning

confidence: 99%

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Experimental and numerical investigations of indoor air movement distribution with an office ceiling fan

Chen

Liu

Gao

et al. 2018

Building and Environment

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Ceiling fans provide cooling to indoor occupants and improve their thermal comfort in warm environments at very low energy consumption. Understanding indoor air distribution associated with ceiling fans helps designs when ceiling fans are used. In this study, we systematically investigate the air movement distribution in an unoccupied office room installed with a ceiling fan, as influenced by (1) fan rotational speed, (2) fan blade geometry, (3) ceiling-to-fan depth, and (4) ceiling height. We both measured and simulated air speeds at four heights in the occupied zone according to ANSI/ASHRAE/IES Standard 55 (2013) for seated and standing occupants. CFD predictions were validated by experimental results. In general, numerical results show that for an unoccupied space, the fan blade geometry, ceiling-to-fan depth, and ceiling height only influence air speed profiles within a cylindrical zone directly under a ceiling fan whose diameter is identical to that of the ceiling fan. However, the average speeds within the cylindrical zone at each height are very similar (< 10% in difference) for the different blade shapes studied, indicating a minor influence of blade geometries on occupants' perception of the thermal environment. The results also indicate that the velocity profile remains similar in the main jet zone (the tapered high-velocity zone under the fan blade) for various rotational speeds. The jet impingement on the floor creates radial airflow at the ankle level (0.1 m) across the room, which is not the most effective airflow distribution for cooling occupants.

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Section: Cfd Modelsmentioning

confidence: 96%

Section: Cfd Modelsmentioning

confidence: 99%

Experimental and numerical investigations of indoor air movement distribution with an office ceiling fan

Chen

Liu

Gao

et al. 2018

Building and Environment

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“…Most studies of air speed fields below ceiling fan have performed measurements in a single line with different radial distances starting from the fan center [29,[31][32][33]35]. However, the flow below the fan is highly unsteady-air speed changes in time reflecting highly turbulent flow.…”

Section: Density Of Measurement Pointsmentioning

confidence: 99%

“…There have been quite a few tests of the patterns of air speed around single ceiling fans in empty rooms [12,[28][29][30], but not many data sets are useful for detailed examination or development into design tools. Most of these measurements were performed in a single line of different radial distances starting from the fan center [29,[31][32][33][34], assuming symmetry of the boundary conditions and fan jet distribution. Moreover, all of these studies were characterizing the flow from a single ceiling fan operating in an empty room.…”

Section: Introductionmentioning

confidence: 99%

“…The same simplification is used in the draft of a new ASHRAE Standard on the quantifying the performance of ceiling fans [35]. The airflow induced by a ceiling fan may be simulated in varying levels of complexity with CFD models, and the techniques involved are still topics of research [31][32][33]36]. High flexibility in the use of possible tools for building computational models requires them to be validated with physical measurements.…”

Section: Introductionmentioning

confidence: 99%

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Detailed experimental investigation of air speed field induced by ceiling fans

Liu

Lipczyńska

Schiavon

et al. 2018

Building and Environment

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Comfort cooling by ceiling fans is cost-effective and energy-efficient compared to compressor-based cooling and fans are commonly used in tropical and subtropical countries. There are however limited data and design tools supporting the design of fan systems, especially for situations where there are multiple fans. In this paper, we investigate airflow profiles induced by a single fan and multiple fans using high spatial resolution air speed measurements (5,760 and 20,160 measuring points for the two cases respectively) in a climatic chamber. To authors' knowledge, this is the first time that interaction between multiple fans has been reported. We developed typical airflow patterns from the measurements and further validated them via smoke visualization. The singlefan results are consistent with previous studies of this configuration, providing additional refinements. For the multiple-fan case, both the difference of fan speed levels and the distance between the fans affect the interacting airflow profiles of the fans in complex ways. When fans are close enough, the combined air speed profile cannot be extrapolated from the profile of a single fan. All the measurement results are open sourced: raw data is included in the supplementary materials and can be visualized via an online platform (single fan, multiple fans). The data and the tool can be used to validate CFD models and inform fan layout design.

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Comparison of stationary and transient RANS modelling

et al. 2020

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Vergleich stationärer und transienter RANS‐Modellierung zur Analyse der räumlichen Geschwindigkeitsverteilung unter Anwendung deckenintegrierter Ventilatoren Deckenventilatoren ermöglichen eine Erhöhung der lokalen Luftgeschwindigkeit am menschlichen Körper. Durch die damit verbundene Wärmeabfuhr steigt die Nutzertoleranz gegenüber warmen Umgebungen. In dieser Studie wird die Anwendung statistischer Turbulenzmodelle (RANS) zur Modellierung der durch deckenintegrierte Ventilatoren induzierten Luftströmung dargestellt. Ein besonderer Fokus wird hierbei auf den Vergleich zwischen stationärer und transienter Simulation gesetzt. Die Ergebnisse der CFD‐Simulation (mittels Fluent) werden mit Messergebnissen der horizontalen Geschwindigkeitsverteilung verglichen. Die Studie zeigt, dass die transiente Simulation mittels Realizable k‐ε Modell zwar ein stabiles Konvergenzverhalten sowohl seitens der Residuen, als auch der Zielwerte aufzeigt, im Vergleich zur stationären Berechnung jedoch der mittlere absolute Fehler in 1,4 m Entfernung zum Ventilator größer ist, obwohl die stationäre Modellierung mittels des Multiple Reference Frame (MRF)‐Verfahrens ein nicht physikalisch begründbares Geschwindigkeitsfeld in der unmittelbaren Umgebung des Ventilators hervorruft. Die Ursache dafür, dass die stationäre Lösung mittels MRF nicht konvergiert, ist auf die räumliche Begrenzung der rotierenden Zone zurückzuführen, so wie es bei deckenintegrierten Ventilatoren durch das Ventilatorgehäuse der Fall ist. Demgegenüber bei frei im Raum hängenden Ventilatoren die rotierende Zone entsprechend adaptiert und das Konvergenzverhalten verbessert werden kann.

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Transient three-dimensional CFD modelling of ceiling fans

Cited by 58 publications

References 25 publications

Experimental and numerical investigations of indoor air movement distribution with an office ceiling fan

Experimental and numerical investigations of indoor air movement distribution with an office ceiling fan

Detailed experimental investigation of air speed field induced by ceiling fans

Comparison of stationary and transient RANS modelling

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