A Newly Designed Supply Diffuser for Industrial Premises

Janbakhsh, Setareh; Moshfegh, Bahram; Ghahremanian, Shahriar

doi:10.1080/14733315.2010.11683867

Cited by 16 publications

(8 citation statements)

References 3 publications

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“…Shown in Figure 2 is the S11 supply device from Stravent Oy, which consists of a large number of confluent jets located on a cylinder. Research on thermal comfort and ventilation performance using confluent jet ventilation, both in an industrial and office environment, has been conducted by Janbakhsh et al (2010) and Janbakhsh and Moshfegh (2014). Especially the region close to the nozzles, where the jets transform from individual jets to a single combined jet through merging and combining, brings increasing complexity to the turbulent flow field.…”

Section: Ventilation Supply Device Airport Terminal Industrial Chimnmentioning

confidence: 99%

Experimental and Numerical Investigations of Confluent Round Jets

Svensson¹

2015

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Unconfined multiple interacting confluent round jets are interesting from a purely scientific point of view, as interaction between neighboring jets brings additional complexity to the flow field. Unconfined confluent round jets also exist in various engineering applications, such as ventilation supply devices, sewage disposal systems, combustion burners, chemical mixing or chimney stacks. Even so, little scientific attention has been paid to unconfined confluent round jets, and detailed investigations on the complete three-dimensional turbulent flow field of confluent jet configurations issuing into an unconfined stagnant environment are scarce.The present work uses both advanced measurement techniques and computational models to provide deeper understanding of the turbulent flow field development of unconfined confluent round jets. Both Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV) have been used to measure mean velocity and turbulence properties within two setups, consisting of a single row of 1×6 jets and a square in-line array of 6×6 confluent jets. LDA was used for measurements very close to the nozzle inlets and to verify the main findings made with PIV. A comparison between LDA and PIV results showed that the two measurement techniques produced results that are in good agreement with each other.Simulations using Computational Fluid Dynamics (CFD) of the 6×6 setup were conducted using three different Reynolds Averaged Navier-Stokes (RANS) turbulence models: the standard k-ε, the RNG k-ε and the Reynolds Stress Model (RSM). The results from the CFD simulations were compared with the experimental PIV data. The employed RANS turbulence models were all capable of accurately predicting mean velocities and turbulent properties in the investigated confluent jet array. In general the RSM and the standard k-ε model provided smaller deviations between numerical and experimental results than the RNG k-ε model. In terms of mean velocity the second-order closure model (RSM) was not found to be superior to the less complex standard k-ε model.The validated CFD results provide data at all locations in the solution domain and the computational results were used to further analyze the investigated confluent jet array. The validated CFD model was also employed in a parametrical investigation, including five independent variables: inlet velocity, nozzle diameter, nozzle edge-toedge spacing, nozzle height and the number of jets in the array. The parametrical investigations made use of statistical methods in the form of Response Surface Methodology and Box-Behnken Design of Experiments. The derived response surface models provided information on the principal influence and relative importance of the investigated parameters within the design limits.ii The positions of the jets within the array strongly influence both mean velocity and turbulence. In all investigated setups the jets experience merging and combining. Square arrays also include considerable jet convergence, which was not present in th...

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Section: Ventilation Supply Device Airport Terminal Industrial Chimnmentioning

confidence: 99%

Experimental and Numerical Investigations of Confluent Round Jets

Svensson¹

2015

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“…In CJ system, a number of jets issuing from closely spaced slots or circular apertures in the same flow directions merge together a short distance downstream to form a single jet normally close to a room surface such as a wall or floor. The combined jets are then directed toward the floor to create a similar effect to that from an IJ system, thus producing a greater horizontal spread over the floor than a displacement jet system (Cho et al, 2008;Janbakhsh et al, 2009;Ghahremanian and Moshfegh, 2014a,b). The characteristics of CJ are similar to the IJ in terms of being a higher momentum room air supply rather than a buoyancy-driven flow as it is in the case of a DV system.…”

Section: Status Of Mechanical Ventilation and Air Distribution Systemsmentioning

confidence: 99%

Ventilation and Air Distribution Systems in Buildings

Awbi

2015

Front. Mech. Eng.

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“…Grinzato et al (2004) and Janbakhsh et al (2010). It measures infrared radiation being emitted from an object based on its surface temperature, and uses infrared detectors to generate thermal images corresponding to the object surface temperature.…”

Section: Whole-field Measuring Techniquesmentioning

confidence: 99%

Experimental and numerical investigations of a ventilation strategy – impinging jet ventilation for an office environment

Chen¹

2014

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A well-functioning, energy-efficient ventilation system is of vital importance to offices, not only to provide the kind of comfortable, healthy indoor environment necessary for the well-being and productive work performance of occupants, but also to reduce energy use in buildings and the associated impact of CO 2 emissions on the environment. To achieve these goals impinging jet ventilation has been developed as an innovative ventilation concept.In an impinging jet ventilation system, a high momentum of air jet is discharged downwards, strikes the floor and spreads over it, thus distributing the fresh air along the floor in the form of a very thin shear layer. This system retains advantages of mixing and stratification from conventional air distribution methods, while capable of overcoming their shortcomings.The aim of this thesis is to reach a thorough understanding of impinging jet ventilation for providing a good thermal environment for an office, by using Computational Fluid Dynamics (CFD) supported by detailed measurements. The full-field measurements were carried out in two test rooms located in a large enclosure giving relatively stable climate conditions. This study has been divided into three parts where the first focuses on validation of numerical investigations against measurements, the second addresses impacts of a number of design parameters on the impinging jet flow field and thermal comfort level, and the third compares ventilation performance of the impinging jet supply device with other air supply devices intended for mixing, wall confluent jets and displacement ventilation, under specific room conditions. In the first part, velocity and temperature distributions of the impinging jet flow field predicted by different turbulence models are compared with detailed measurements. Results from the non-isothermal validation studies show that the accuracy of the simulation results is to a great extent dependent on the complexity of the turbulence models, due to complicated flow phenomena related to jet impingement, such as recirculation, curvature and instability. The f v  2 turbulence model shows the best performance with measurements, which is slightly better than the SST k-ω model but much better than the RNG k-ε model. The difference is assumed to be essentially related to the magnitude of turbulent kinetic energy predicted in the vicinity of the stagnation region. Results from the isothermal study show that both the SST k-ω and RNG k-ε models predict similar wall jet behaviours of the impinging jet flow. IVIn the second part, three sets of parametric studies were carried out by using validated CFD models. The first parametric study shows that the geometry of the air supply system has the most significant impact on the flow field. The rectangular air supply device, especially the one with larger aspect ratio, provides a longer penetration distance to the room, which is suitable for industrial ventilation. The second study reveals that the interaction effect of cooling ceiling, heat sources ...

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A Newly Designed Supply Diffuser for Industrial Premises

Cited by 16 publications

References 3 publications

Experimental and Numerical Investigations of Confluent Round Jets

Experimental and Numerical Investigations of Confluent Round Jets

Ventilation and Air Distribution Systems in Buildings

Experimental and numerical investigations of a ventilation strategy – impinging jet ventilation for an office environment

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