Scale model study of airflow performance in a ceiling slot-ventilated enclosure: Non-isothermal condition

Yu, Hongbin; Liao, Chung‐Min; Liang, Hong-Erh; Chiang, Kuo-Chih

doi:10.1016/j.buildenv.2005.12.004

Cited by 33 publications

(14 citation statements)

References 8 publications

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“…As defined in [6][7], if the relative influence of momentum and buoyancy are used as the critical criteria to classify the flow regions, the nonbuoyancy region refers to the situation in which momentum dominates the jet behavior. Then the jet behaves like a plume rather than a jet with a certain structure.…”

Section: Self Similarity Of the Buoyant Jetmentioning

confidence: 99%

“…However, non-isothermal conditions pose a challenging problem in the prediction of the buoyant attached jet behavior. One of the attached jet applications in rooms is the active chilled beam which enables a plane jet discharging on the ceiling so that the highvelocity region is restricted to the ceiling, thus possibly freeing the occupied zone from draught [5][6]. Under normal design conditions, the jet stays attached to the ceiling until the opposite wall is reached, when it is then deflected downwards into the wall-floor zone.…”

Section: Introductionmentioning

confidence: 99%

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Experimental investigation and modelling of a buoyant attached plane jet in a room

Cao¹,

Kurnitski²,

Ruponen³

et al. 2009

Applied Thermal Engineering

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Buoyant attached jets are widely used in various types of supply air devices especially in office buildings. This study focuses on a two-dimensional cooled attached jet characteristic, including mean flow field structure, specification of the jet regions and maximum velocity decay. A new superimposing model is derived to predict the maximum velocity decay and validated by measurement results. The measurement results demonstrate that the intermediate region of a buoyant jet does exist when an inner layer extends downstream of the jet slot. In addition, by assuming that the buoyant force is the main extra force on the jet flow in the acceleration process, the superimposing model predicted the maximum velocity decay with precise accuracy in a Reynolds number range of 667-4000, based on slot heights of 20 and 30 mm and slot velocities of 0.50, 1.00 and 2.00 m/s. At a distance of 1000 mm from the slot, the velocity profile displays a self similarity character like an isothermal turbulent jet. In the final region, where the buoyancy flux completely dominates the jet, the jet behaved like a plume with an unstable flow field.

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Section: Self Similarity Of the Buoyant Jetmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental investigation and modelling of a buoyant attached plane jet in a room

Cao¹,

Kurnitski²,

Ruponen³

et al. 2009

Applied Thermal Engineering

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“…The diffuser throw was found to be linearly related to the Archimedes number, which represents the ratio of buoyancy to inertial force exerted on the fluid. Yu et al (2007) studied airflow in a ceiling slot-ventilated enclosure in a 1:3 scale model. They measured the velocity and temperature profiles, temperature decays, and thermal boundary layers.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Air Mixing and Thermal Comfort From High Sidewall Supply Air Jets

Ridouane

2011

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NOTICEThis report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. AcknowledgmentsThe author thanks Ren Anderson for his guidance and for his valuable contributions to this report.iv Executive SummaryEffective mixing of conditioned air with room air is an essential factor for providing uniform comfort in homes. The higher the supply air flow rates, the easier it is to reach good mixing within the space. In high performance homes, however, the flow rates required to meet the small remaining thermal loads may not be large enough to maintain uniform mixing in the space.The objective of this study is to evaluate operating conditions required to maintain uniform mixing, within high performance homes, under both heating and cooling conditions. This can be achieved by creating proper combination of temperature and air motion in the occupied zone of the conditioned space. Lack of uniform conditions in the space or excessive fluctuation of conditions produces discomfort. Discomfort can be caused by excessive air motion (draft), excessive room air temperature variations, or failure to deliver or distribute air according to load requirements.To address this question we used computational fluid dynamics modeling to evaluate the performance of high sidewall air supply for residential applications in heating and cooling modes. Parameters that were varied in the study include the supply velocity, supply temperature, and inlet dimensions. The model provided high resolution velocity and temperature distributions in the room, which were used to determine the effective draft temperature. The latter is then used to calculate the Air Diffusion Performance Index (ADPI). This parameter was used to evaluate the air distribution and thermal comfort in the occupied zone. ADPI is the percentage of locations where the effective draft temperature and air speed meet comfort specifications. The higher the ADPI value is, the more comfortable the space will be for most occupants.The results provide information to guide the selection of high sidewall air supply inlets to maintain proper room mixing for heating and cooling of high performance homes. It is demonstrated that these systems can achieve good mixing and provide acceptable comfort levels....

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“…For avoiding perturbations in the flow two pressure regulators in the inlet and outlet were set. Laser Doppler anemometry (LDA) method and particle image velocity (PIV) were used to register fluid flow movements A 1/3 scale model of a prototype building was used to study airflow performance in a confined enclosure [258]. The dimensions of the scale model were 1.8 m × 2.4 m × 0.9 m.…”

Section: Ventilation For Buildings Using Scale Modelsmentioning

confidence: 99%

A review on experimental research using scale models for buildings: Application and methodologies

Lirola

Castañeda

Lauret

et al. 2017

Energy and Buildings

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a b s t r a c tA complete review on scale model testing for buildings, considering a wide range of methodologies and new manufacturing techniques, in areas such as statics and dynamics, acoustics, lighting, aerodynamics and thermodynamics for energy efficiency is presented. On the one hand, scale model testing for buildings require different considerations and techniques and are usually focused on one specific physical field contributing to the information scattering. On the other hand, they are sometimes too general, theoretical or unpractical. Although commercial computer simulations are first option among professionals, they necessarily simplify complex phenomena and ignore, among other aspects, size effects and latest findings in fractals. The potential of complementary experiments using new manufactured scale models for buildings is raising, however, it is still missing a practical overview through different physical fields specifically for buildings with these considerations. This review gives a wide perspective and unified scope on uses and possibilities of scale model testing for buildings, from the traditional configurations of Leon Battiste Alberti to new possibilities applying complex physics and new techniques of 3D-modelling.

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Scale model study of airflow performance in a ceiling slot-ventilated enclosure: Non-isothermal condition

Cited by 33 publications

References 8 publications

Experimental investigation and modelling of a buoyant attached plane jet in a room

Experimental investigation and modelling of a buoyant attached plane jet in a room

Evaluation of Air Mixing and Thermal Comfort From High Sidewall Supply Air Jets

A review on experimental research using scale models for buildings: Application and methodologies

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