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Experimental Evaluation of Intermittent Air Jet Ventilation Strategy: Cooling effect and the associated energy saving
Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Center for the Built Environment, University of California, Berkeley, Berkeley CA, USA. (Energy Systems)ORCID-id: 0000-0002-2171-3013
Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. (Energy Systems)
2016 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

The potential to reduce building energy demand is high especially on building services like ventilation and air conditioning. This potential lies in identifying ventilation strategies that can provide both the required indoor climate and lower the energy use. One of the strategies is optimizing elevated air movements to enhance human convective and evaporative cooling which, as shown in literature, results in reduced energy use on cooling. This paper evaluates the cooling potential and the resulting energy saving of a novel air supply system called intermittent air jet strategy (IAJS). As shown in this study, IAJS with velocities of 0.4 m/s at the breathing height provides a cooling effect equivalent to reducing the ambient temperature in a mixing ventilation system by up to 1.5 oC to achieve a neutral sensation. This translates to a 13% reduction on the cooling demand. The strategy is also shown to have an energy saving potential of up to 50% on the supply fan. 

sted, utgiver, år, opplag, sider
2016.
Emneord [en]
Convective cooling, Equivalent temperature, Cooling power, Thermal manikin, Energy saving, High occupant density
HSV kategori
Identifikatorer
URN: urn:nbn:se:hig:diva-22179OAI: oai:DiVA.org:hig-22179DiVA, id: diva2:950150
Konferanse
Indoor Air 2016, The 14th International Conference on Indoor Air Quality and Climate, Ghent, Belgium, July 2-9, 2016
Tilgjengelig fra: 2016-07-28 Laget: 2016-07-28 Sist oppdatert: 2018-03-13bibliografisk kontrollert
Inngår i avhandling
1. Experimental study of an intermittent ventilation system in high occupancy spaces
Åpne denne publikasjonen i ny fane eller vindu >>Experimental study of an intermittent ventilation system in high occupancy spaces
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Spaces with high occupancy density like classrooms are challenging to ventilate and use a lot of energy to maintain comfort. Usually, a compromise is made between low energy use and good Indoor Environmental Quality (IEQ), of which poor IEQ has consequences for occupants’ health, productivity and comfort. Alternative strategies that incorporate elevated air speeds can reduce cooling energy demand and provide occupant’s comfort and productivity at higher operative temperatures. A ventilation strategy, Intermittent Air Jet Strategy (IAJS), which optimizes controlled intermittent airflow and creates non-uniform airflow and non-isothermal conditions, critical for sedentary operations at elevated temperatures, is proposed herein.

The primary aim of the work was to investigate the potential of IAJS as a ventilation system in high occupancy spaces. Ventilation parameters such as air distribution, thermal comfort and indoor air quality are evaluated and the system is compared with a traditional system, specifically, mixing ventilation (MV). A 3-part research process was used: (1) Technical (objective) evaluation of IAJS in-comparison to MV and displacement ventilation (DV) systems. (2) An occupant response study to IAJS. (3) Estimation of the cooling effect under IAJS and its implications on energy use. All studies were conducted in controlled chambers.

The results show that while MV and DV creates steady airflow conditions, IAJS has  cyclic airflow profiles which results in a sinusoidal temperature profile around occupants. Air distribution capability of IAJS is similar to MV, both having a generic local air quality index in the occupied zone. On the other hand, the systems overall air change rate was higher than a MV. Thermal comfort results suggest that IAJS generates comfortable thermal climate at higher operative temperatures compared to MV. Occupant responses to IAJS show an improved thermal sensation, air quality perception and acceptability of indoor environment at higher temperatures as compared to MV. A comparative study to estimate the cooling effect of IAJS shows that upper HVAC setpoint can be increased from 2.3 – 4.5 oC for a neutral thermal sensation compared to a MV. This implies a substantial energy saving potential on the ventilation system. In general, IAJS showed a potential for use as a ventilation system in classrooms while promising energy savings.  

Abstract [sv]

Lokaler där många människor vistas, som t.ex. klassrum, är ofta svåra att ventilera. Att upprätthålla en bra termisk komfort kräver en hög energianvändning. Vanligtvis blir det en kompromiss mellan låg energianvändning och bra kvalitet på inomhusmiljön (IEQ). Dålig IEQ får konsekvenser för människors hälsa, produktivitet och komfort. Alternativa ventilationsstrategier, som använder förhöjda lufthastigheter, kan minska kylbehovet och därmed energianvändningen. I denna avhandling utvärderas en ny ventilationsstrategi, Intermittenta luftstrålar (IAJS), där korta perioder med hög lufthastighet genererar en svalkande effekt, när rummets temperatur upplevs som för hög.

Det primära syftet med arbetet var att undersöka potentialen hos IAJS som ett ventilationssystem för klassrum, där den termiska lasten ofta är hög. Strategin jämförs mot traditionella ventilationsprinciper som omblandande ventilation (MV) och deplacerande ventilation (DV). Parametrar som luftdistributionsindex, termisk komfort, luftkvalitet och energibesparing har utvärderats. Alla studier utfördes i klimatkammare.

Resultaten visar att medan MV och DV skapar konstanta luftflödesförhållanden genererar IAJS cykliska hastighetsprofiler samt en sinusformad temperaturvariation i vistelsezonen. IAJS klarar att bibehålla ett bra termiskt klimat vid högre operativa temperaturer jämfört med MV. I en jämförelse med ett traditionellt HVAC-system visar beräkningar  att dess börvärde kan höjas från 2.3 till 4.5 °C med bibehållen termisk komfort. Detta indikerar en avsevärd energibesparingspotential vid användande av IAJS.

sted, utgiver, år, opplag, sider
Gävle: Gävle University Press, 2017. s. 74
Serie
Studies in the Research Profile Built Environment. Doctoral thesis ; 3
Emneord
Intermittent airflow, Indoor air quality, Perceived air quality, Thermal sensation, thermal comfort, Air movement acceptability, Convective cooling, Cooling effect., Intermittent luftflöde, Luftstrålar, Upplevd luftkvalitet, Termisk komfort, Acceptans av luftrörelser, Konvektiv kylning, Kyleffekt.
HSV kategori
Identifikatorer
urn:nbn:se:hig:diva-23754 (URN)978-91-88145-11-6 (ISBN)978-91-88145-12-3 (ISBN)
Disputas
2017-05-18, 12:108, Kungsbäcksvägen 47, Gävle, 10:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2017-04-26 Laget: 2017-03-15 Sist oppdatert: 2019-10-23bibliografisk kontrollert

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