Experimental and numerical study of influence of air ceiling diffusers on room air flow characteristics

Aziz, M. Ashraf; Gad, Ibrahim; Mohammed, El Shahat F. A.; Mohammed, Ramy H.

doi:10.1016/j.enbuild.2012.09.027

Cited by 73 publications

(24 citation statements)

References 7 publications

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“…In fact, there is a consensus in the literature [1,3,6,10], that high entrainment implies a relatively small K v value. The inconsistency may be due to the inappropriate measurement technique used.…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

“…L represents the horizontal length to which the jet needs to extend. L T is defined as the distance from the diffuser outlet to the point where the jet centerline velocity has decreased to a specified terminal velocity V t [2,6,10]. V t = 0.25 m/s is usually selected, but other values have also been used [7,8,10,19].…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Among radial diffusers available on the market, the multi-cone diffuser [4][5][6][7][8][9] is widely used in commercial and office spaces. Another popular ceiling-mount diffuser is the vortex diffuser [4][5][6][7]10], that produces a jet with a high degree of spin about the axis parallel to its main direction.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Airflow characteristics and thermal comfort generated by a multi-cone ceiling diffuser with and without inserted lobes

Bragança

Sodjavi

Meslem

et al. 2016

Building and Environment

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Mixing ventilation is commonly used to control thermal comfort in a room by means of air jets. In summer conditions, the occupants often complain of thermal discomfort and draft problems, because the cooling airflow penetrates the occupied zone under buoyancy force effect, with high speeds and low temperatures. To reduce these problems, the jet trajectory could be maintained away from the occupant, by means of a radial jet attached to the ceiling.One great limitation of most radial ceiling diffusers is their inability to correctly mix the jet to the ambient air, and the use of the Coanda effect may worsen this issue because it reduces jet induction. The design of the diffuser itself to enhance the jet mixing with the ambient air by means of inserted lobes was recently proposed in an European patent. In this paper, an experimental investigation is made on airflow pattern and thermal comfort generated in a full scale model room by a ceiling diffuser, and its performance is compared with the same diffuser equipped with inserted lobes. The jet flow from the diffuser and its interaction with a heated manikin simulating an occupant were analyzed with the whole-field PIV technique.Thermal dissatisfaction and draft effect were analyzed based on traditional pointwise measuring probes and the standards ISO 7730 and ASHRAE 55. It is revealed that thermal discomfort and draft sensation were substantially reduced using inserted lobes, without significant changes of pressure drop and sound pressure levels.

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Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Section: Accepted Manuscriptmentioning

confidence: 99%

See 1 more Smart Citation

Airflow characteristics and thermal comfort generated by a multi-cone ceiling diffuser with and without inserted lobes

Bragança

Sodjavi

Meslem

et al. 2016

Building and Environment

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show abstract

“…The parameters considered for design improvement are rake angles, root and tip bent angles and positions. Aziz and Shahat et al (2012) experimentally and numerically investigated the behaviour of ceiling fan induced flow field inside a ventilated room and observed the effects of vortices, round and square ceiling diffuser on thermal comfort. Results show that energy saved by square or round diffuser is 1.5 times greater than vortex diffuser.…”

Section: Introductionmentioning

confidence: 99%

Parametric Study and Optimization of Ceiling Fan Blades for Improved Aerodynamic Performance

Adeeb¹,

Maqsood²,

Mushtaq³

et al. 2016

JAFM

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ABSTARCT This paper includes parametric study and optimization of non-linear ceiling fan blades by combining the techniques of Design of Experiments (DOE), Response Surface Methods (RSM) and Computational Fluid Dynamics (CFD). Specifically, the nonlinear (elliptical) planform shape of ceiling fan blade is investigated in conjunction with blade tip width, root and tip angle of attack. Sixteen cases are designed for three blade ceiling fan using two level full factorial model. The flow field is modeled using Reynolds-Averaged-Navier-Stokes approach. The performance variables used to formulate a multi-objective optimization problem are volumetric flow rate, torque and energy efficiency. Response Surface Method is used to generate the optimized design for non-linear ceiling fan blade profile. The results reveal that the interactions between the design variables play a significant role in determining the performance. It is concluded that the nonlinear forward sweep has a moderate effect on response parameters.

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“…In the study heat removal metrics was referred to as thermal energy removal effectiveness [22]. An analogous concept of heat removal as an index of ventilation performance metrics of air distribution system was adopted by Mohammed [23] and Aziz et al [24] where the effectiveness of different air distribution systems was investigated.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Ventilation Efficiency in a Dentistry Surgical Room

et al. 2016

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Abstract.As a response to the need to provide an acceptable thermal comfort and air quality in indoor environments, various ventilation performance indicators were developed over the years. These metrics are mainly geared towards air distribution, heat and pollutant removals. Evidence exists of influencing factors on these indicators as centered on ventilation design and operations. Unlike other indoor environments, health care environment requires better performance of ventilation system to prevent an incidence of nosocomial and other hospital acquired illnesses. This study investigates, using in-situ experiments, the ventilation efficiency in a dentistry surgical room. Thermal and hygric parameters were monitored on the air terminal devices and occupied zone over a period of one week covering both occupied and unoccupied hours. The resulting time-series parameters were used to evaluate the room's ventilation effectiveness. Also, the obtained parameters were benchmarked against ASHRAE 170 (2013) and MS1525 (2014) requirements for ventilation in health care environment and building energy efficiency respectively. The results show that the mean daily operative conditions failed to satisfy the provisions of both standards. Regarding effectiveness, the findings reveal that the surgical room ventilation is ineffective with ventilation efficiency values ranging between 0 and 0.5 indicating air distribution short-circuiting. These results suggest further investigations, through numerical simulation, on the effect of this short-circuiting on thermal comfort, infection risk assessments and possible design improvements, an endeavour that forms our next line of research inquiries.

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Experimental and numerical study of influence of air ceiling diffusers on room air flow characteristics

Cited by 73 publications

References 7 publications

Airflow characteristics and thermal comfort generated by a multi-cone ceiling diffuser with and without inserted lobes

Airflow characteristics and thermal comfort generated by a multi-cone ceiling diffuser with and without inserted lobes

Parametric Study and Optimization of Ceiling Fan Blades for Improved Aerodynamic Performance

Experimental Investigation of Ventilation Efficiency in a Dentistry Surgical Room

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