Abstract:In Heating Ventilating and Air Conditioning (HVAC) systems, ventilation strategies impact building energy consumption, occupants' thermal comfort and Indoor Air Quality (IAQ). Ventilation strategies such as Mixing Jet Ventilation (MJV), Displacement Ventilation (DV), and Impinging Jet Ventilation (IJV) are operated on the different principals. MJV relies on dilution, while DV and IJV rely on both dilution and stratification. Due to climatic variation, ventilation strategies must be operated under different coo… Show more
“…For all cases, the layouts of inlets and outlets are similar to previous research. 17,25–27 Figure 2.(a) Square ceiling diffuser in the test chamber and (b) nine-point model of square diffuser in CFD simulation.…”
In this study, 12 cases were investigated in an office-layout room using experiments and computational fluid dynamics (CFD) simulations. The heating performances of four ventilation methods (i.e. mixing ventilation (MV), stratum ventilation (SV), deflection ventilation (DeV) and impinging jet ventilation (IJV)) were comprehensively compared by various evaluation indexes (i.e. predicted mean vote (PMV), draught rate (DR), vertical air temperature difference (△T), air diffusion performance index (ADPI), energy utilization coefficient (EUC), air change efficiency (ACE) and contaminant removal efficiency (CRE)). Better thermal comfort was found in rooms heated by SV and DeV. The PMV, DR and △T under SV and DeV complied with Category B of ISO 7730:2005, and the ADPI was in full compliance with the stipulation of ANSI/ASHRAE 113-2022. For the energy-saving characteristic, the targeted-occupied-zone ventilation methods (i.e. SV, DeV and IJV) can effectively deliver warm air to the occupied zone, with the EUC values higher than unity and thus providing a good potential for energy saving. SV and IJV showed slightly higher ACEs in the breathing zone. The contaminant removal effectiveness of SV, DeV and IJV was comparable. Under the combined influence of occupant thermal plumes and locations of exhausts, MV showed a high CRE. However, the CRE under MV decreased significantly when the exhausts were not above occupants. In the case of supply air parameters in this study, the entropy-weight method indicated that DeV and SV had a better overall performance for winter heating, followed by IJV and then MV.
“…For all cases, the layouts of inlets and outlets are similar to previous research. 17,25–27 Figure 2.(a) Square ceiling diffuser in the test chamber and (b) nine-point model of square diffuser in CFD simulation.…”
In this study, 12 cases were investigated in an office-layout room using experiments and computational fluid dynamics (CFD) simulations. The heating performances of four ventilation methods (i.e. mixing ventilation (MV), stratum ventilation (SV), deflection ventilation (DeV) and impinging jet ventilation (IJV)) were comprehensively compared by various evaluation indexes (i.e. predicted mean vote (PMV), draught rate (DR), vertical air temperature difference (△T), air diffusion performance index (ADPI), energy utilization coefficient (EUC), air change efficiency (ACE) and contaminant removal efficiency (CRE)). Better thermal comfort was found in rooms heated by SV and DeV. The PMV, DR and △T under SV and DeV complied with Category B of ISO 7730:2005, and the ADPI was in full compliance with the stipulation of ANSI/ASHRAE 113-2022. For the energy-saving characteristic, the targeted-occupied-zone ventilation methods (i.e. SV, DeV and IJV) can effectively deliver warm air to the occupied zone, with the EUC values higher than unity and thus providing a good potential for energy saving. SV and IJV showed slightly higher ACEs in the breathing zone. The contaminant removal effectiveness of SV, DeV and IJV was comparable. Under the combined influence of occupant thermal plumes and locations of exhausts, MV showed a high CRE. However, the CRE under MV decreased significantly when the exhausts were not above occupants. In the case of supply air parameters in this study, the entropy-weight method indicated that DeV and SV had a better overall performance for winter heating, followed by IJV and then MV.
“…The hybrid geothermal cooling system with heat exchanger (DOE, 2001). Navvab, 2007). The most common practice is mixing jet system where high supply velocity mixes room temperature and pollutants homogeneously.…”
Section: Displacement Ventilation and Under Floor Air Distributionmentioning
confidence: 99%
“…To mitigate this consequence, new systems such as Impinging Jet and Confluent Jet are invented to be the alternatives. Past studies show that both systems allow typical cool supply temperature and, at the same time, stratification is properly maintained (Varodompun & Navvab, 2007;Karimi-panah et al, 2005;Karimipanah & Awbi, 2002). Currently, E&E rating system such as LEED only permit the building with DV system to be scored in IEQ (increased ventilation, thermal comfort controllability) and energy credits (USGBC, 2005).…”
Section: Displacement Ventilation and Under Floor Air Distributionmentioning
Under current energy and environmental concerns, buildings are targeted as problems required immediatesolutions. Generally, buildings consume plenty of resources, produce unwanted wastes, and sometimes demoteIndoor Environmental Quality (IEQ). Given these negative impacts, Green Building was introduced as ananswer to mitigate the current energy and environmental problems. Architects, engineers, and practitionersquickly adopt this green building idea but the direction was both diversified and unclear. At that time, proclaimedgreen building seems to be just promise lacking of solid evidences. Energy & Environmental rating systemwas initially proposed as a campaign attempting to quantify green buildings. Different measures were takenand then weighted for scoring purposes. Using these scores, green buildings are possible to be quantifiedand ranked afterward. In this review article, not only the rating systems, i.e. BREEAM, Green Star, and GreenGlobe, TEEAM, will be overviewed, but also LEED, the most dominating system in US, will be discussedin detail. The simplicity by having six sustainability measures including sustainable site, water efficiency,energy and atmosphere, material and resources, IEQ, and innovation in design, are the key success of LEEDrating system. Moreover, the flexibility of having different compliance methods and scoring options makes manydesigners are in favor of this approach. By using performance-base compliance method, designers can comparetheir design against the base case for winning the higher performances such as energy cost. The score willthen be interpolated and given by exceeding performances. In order to obtain high scores, practices andtechnologies that are acknowledged by rating systems, particularly LEED, should be systematically strategized.Xeriscaping, Green Roof, Geothermal Cooling, Displacement Ventilation, and Demand Control Ventilation, arethe examples of such technologies that greatly promote the scores across multiple categories. By reviewingcompositions, mechanism, practice, and technologies of green building rating systems, this article should bea useful source for practitioners who will or already involve in any green building project and looking forwardto quantify their buildings with any rating system in the near future.
“…Depending on the diffuser type, a distinction can be made between axisymmetric, flat, radial, and vortex airflow. The selection, location, number, and types of supply diffusers are essential to achieve suitable air quality and optimal thermal condition in the ventilated space [4,5].…”
The ventilation system plays a crucial role in every building. Proper design and optimization of its operation increase the comfort of users due to efficient air exchange and at the same time control its velocity in the rooms. The aim of this paper is the analysis of the effect of plenum box entry on the velocity profile concerning the diffuser face panel. This issue may sometimes be ignored at the design stage but can significantly affect the airflow from the diffuser and consequently increase the risk of draft. The results of the PIV experimental measurements and numerical simulations concerning various entries of the plenum box (top and side) were investigated in this study. The measurements were used to develop the mathematical and numerical models, which were then used to assess the effect of localization of the spigot of the plenum box on its operation. The numerical analysis was carried out on plenum boxes with the air diffuser with a face panel composed of square grid perforations. Analyses show that the entries significantly affect both the way of air distribution inside the plenum box and the profile of the airflow and its velocity under the simulated air diffuser.
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