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Publications (10 of 10) Show all publications
Kabanshi, A., Andersson, H., Sundberg, M., Senkic, D. & Sandberg, M. (2024). Assessing airborne infection risk through a model of airflow evacuation and recirculation dynamics.. In: : . Paper presented at RoomVent Conference, April 22-25, Stockholm, Sweden.
Open this publication in new window or tab >>Assessing airborne infection risk through a model of airflow evacuation and recirculation dynamics.
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2024 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In a ventilated room, the indoor airflows are complicated but can generally be defined by an internal recirculating airflow generated by flooding of ventilation air. This concept categorizes the internal room flow (air and contaminants) as consist of two populations: One leaving the room and the other recirculating. The one recirculating is spreading the contaminants while the one leaving is evacuating the contaminants, which are quantified by the transfer probability between the source and other locations in the room and by purging flow rate, respectively. This concept accounts for spatial and temporal aspects in risk of airborne infection transmission. The current paper proposes and discusses a revised risk infection model based on this concept and has demonstrated applicability of the model with a test measurement setup with both mixing and displacement ventilation systems. The results emphasize the importance of considering both spatial and temporal factors in assessing airborne infection risks. It underscores the need for dynamic models like the proposed revised Wells-Riley model to provide a more accurate representation of infection risks in various indoor environments. Additionally, it discusses the necessity for longer measurement periods to fully understand the evolving nature of these risks. 

Keywords
Infectious respiratory disease, Airborne infection risk, Air recirculation, purging flowrate, Contaminant flooding
National Category
Building Technologies Mechanical Engineering
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-44122 (URN)
Conference
RoomVent Conference, April 22-25, Stockholm, Sweden
Available from: 2024-04-26 Created: 2024-04-26 Last updated: 2024-04-29Bibliographically approved
Andersson, H., Sundberg, M., Senkic, D., Sandberg, M. & Kabanshi, A. (2024). FAST-AIR: Fast analytic systems for tracer-gas assessment in indoor research: Development and testing of CO2 tracer-gas system.. In: : . Paper presented at RoomVent Conference, 22nd - 25th April, Stockholm Sweden.
Open this publication in new window or tab >>FAST-AIR: Fast analytic systems for tracer-gas assessment in indoor research: Development and testing of CO2 tracer-gas system.
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2024 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The time constant of ventilation of rooms in buildings is between 15 minutes (in office spaces) to 2 hours (in residential buildings). Currently, most of the tracer gas system analyzers on the market have a minute-based time constant and depending on the channels a cycle of sampling and analysis may take up to 6 minutes, E.g., 6 channel system. Essentially, only mean values are recorded with most present tracer gas analyzers. This is a hindrance for detailed temporal analysis of conditions in the room and consequently is does not capture the resolution of the influence of the internal flow on air and contaminant distribution. The current paper presents work on the development and testing of a fast response CO2 tracer-gas system with a time constant of 1 second. In contrast to the present analyzers, not only the mean values but also the whole statistical distribution of variables can be recorded, and pulse responses can be analyzed. This makes the system viable for measurement and analysis of not only spatial but also temporal distribution of contaminants. For example, recirculating airflow in the room generated by flooding of ventilation air is possible to be measured and thus making it easy to extend the analyses of the process of ventilation far beyond the possibilities with current systems.

Keywords
Tracer-gas Analyzer, fast response, temporal distribution, contaminant transport, indoor measurements
National Category
Mechanical Engineering Building Technologies
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-44121 (URN)
Conference
RoomVent Conference, 22nd - 25th April, Stockholm Sweden
Funder
Swedish Research Council Formas, Dnr: 2021-01606
Available from: 2024-04-26 Created: 2024-04-26 Last updated: 2024-05-02Bibliographically approved
Andersson, H., Cehlin, M. & Moshfegh, B. (2023). An Investigation Concerning Optimal Design of Confluent Jets Ventilation with Variable Air Volume. The International Journal of Ventilation
Open this publication in new window or tab >>An Investigation Concerning Optimal Design of Confluent Jets Ventilation with Variable Air Volume
2023 (English)In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044Article in journal (Refereed) Epub ahead of print
Abstract [en]

This  parametric study aims to predict the  performance of confluent jets ventilation (CJV) with variable air  volume (VAV) from four  CJV  design parameters. A  combination of  computational fluid dynamics (CFD), and response surface method (RSM) has  been used to  predict the  energy efficiency, thermal comfort and  IAQ  for  the  four  expected vital  design variables, i.e.,  heat load (XH),  number of  nozzles (XN),  airflow rate  (XQ) and  supply temperature (XTS).  The  RSM was  used to  generate a  quad-ratic  equation for  the  response variables exhaust temperature (TE),  sup-ply  temperature (TP),  PMV, DR, eT and  ACE. The  RSM  shows that  the  TE, TP and PMV were independent of the number of nozzles. The proposed equations were used to  generate setpoints optimized for  thermal com-fort  (PMV) for  summer, spring and  winter cases with different CLO  fac-tors  and  different TS under a  scenario where the  heat load varied between 10-30W/m2.  TE was  used as  setpoint to  regulate the  airflow rate  to  keep the  PMV values close to  zero. The  results show that  by adapting the TS to the CLO factor both thermal comfort and the energy efficiency can  be  improved. Further energy reduction can  be  gained by downregulating the airflow rate to keep the TP at a fixed setpoint when the  heat load is  decreased. This  means that  a  CJV  can  effectively be combined with VAV  to  improve environmental performance with good thermal comfort (-0.5<PMV <0.5,  DR <20%), above average IAQ (ACE = 106%) and  with a  higher heat removal efficiency (eT = 110%) than conventional mixing ventilation

Place, publisher, year, edition, pages
Taylor & Francis, 2023
Keywords
Parametric study; numerical investigations; confluent jet ventilation; ventilation efficiency; indoor air quality; energy efficiency
National Category
Energy Engineering
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-43500 (URN)10.1080/14733315.2023.2300231 (DOI)001145948800001 ()2-s2.0-85184734259 (Scopus ID)
Funder
Knowledge Foundation, 20120273
Available from: 2023-12-28 Created: 2023-12-28 Last updated: 2024-04-11Bibliographically approved
Andersson, H., Cehlin, M. & Moshfegh, B. (2022). A numerical and experimental investigation of a confluent jets ventilation supply device in a conference room. Energies, 15(5), Article ID 1630.
Open this publication in new window or tab >>A numerical and experimental investigation of a confluent jets ventilation supply device in a conference room
2022 (English)In: Energies, E-ISSN 1996-1073, Vol. 15, no 5, article id 1630Article in journal (Refereed) Published
Abstract [en]

In this study, confluent jets ventilation (CJV) supply devices with three different nozzle arrays (1 × 19, 2 × 19, 3 × 19) were investigated both numerically and experimentally at two different airflow and supply air temperature set-ups. The performance of the CJV supply devices was investigated concerning thermal comfort, indoor air quality (IAQ), and heat removal effectiveness in a conference room environment. A comparison between the experimental and numerical results showed that the v2−f model had the best agreement out of the investigated turbulence models. The numerical results showed that the size of the array had a great impact both on near-field development and on the conditions in the occupied zone. A larger array with multiple rows and a lower momentum conserved the inlet temperature and the mean age of the air better than a single-row array with a higher momentum. A larger array with multiple rows had a higher IAQ and a greater heat removal effectiveness in the occupied zone because the larger array conserved the mean age of air better and the buoyancy driven flow was slightly better at removing the heat. Because of the lower inlet velocities, they also had lower velocities at ankle level, which decreased the risk of draft and thermal discomfort.

Place, publisher, year, edition, pages
MDPI, 2022
Keywords
experimental investigations; numerical investigations; confluent jet ventilation; ventilation efficiency; indoor air quality
National Category
Energy Systems
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-38004 (URN)10.3390/en15051630 (DOI)000773636000001 ()2-s2.0-85125196328 (Scopus ID)
Funder
Knowledge Foundation, 20120273
Available from: 2022-02-22 Created: 2022-02-22 Last updated: 2024-04-11Bibliographically approved
Andersson, H. (2022). Optimization of confluent jets ventilation with variable airflow. (Doctoral dissertation). Gävle: Gävle University Press
Open this publication in new window or tab >>Optimization of confluent jets ventilation with variable airflow
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In recent years, applications of confluent jets for design of ventilation supply devices have been widely studied. Similarly, numerous studies have been made on the potential and application of variable air volume (VAV) in order to reduce the energy demand of ventilation systems. This study investigates the combination of confluent jets ventilation (CJV) and VAV, both in terms of the near-field flow behavior of the device and the impact on thermal comfort, indoor air quality and energy efficiency in conference room and classroom environments when the airflow rate is varied. For the investigation of CJV with VAV in a classroom environment two experimental studies were performed. One was a field study in a school classroom with a constant supply temperature and four cases with varying heat loads and airflow rates. The other took place in a laboratory environment with five cases, all with varying heat loads, supply temperatures and airflow rates. The two experimental studies measured mean age of air, air speeds and temperatures in the occupied zone. Both studies showed that CJV had higher energy efficiency and indoor air quality than conventional mixing ventilation. The main effects of lower supply temperatures were higher velocities in the occupied zone as well as lower temperatures due to higher energy efficiency . CJV produces mixing ventilation conditions at lower airflow rates (<4.2 ACH) and non-uniform conditions at higher airflow rates. The thermal comfort was similar to that of conventional mixing ventilation and had very small temperature gradients compared to displacement ventilation. For the investigation of CJV with VAV in a conference room environment three combined experimental and numerical studies were performed. One focused on the jet velocity profiles from the CJV supply device, the results of which were used as boundary conditions for the two other studies. The second study measured the conditions in the confluent jet development area and the occupied zone experimentally for six cases with different supply temperatures, airflow rates and nozzle matrix configurations. The results were used for validating the numerical model which was used in the last paper. The final paper was a parametric numerical study which used the response surface method to investigate the impact of four design variables: heat load, number of nozzles, airflow rate and supply temperature on energy efficiency, indoor air quality and thermal comfort. The results show that indoor air quality is increased with higher airflow rates. The energy efficiency has a negative correlation to the heat load but a positive correlation to the airflow rate which results in relatively stable heat removal effectiveness of 110% as heat load is increased and the VAV system compensates with higher airflow rates. The results also show that in a VAV system which aims at providing  uniform temperatures in the occupied zone, the thermal comfort is mostly dependent on a combination of the CLO value and the range of the airflow rates. At low CLO values the range of the airflow rate needs to be increased to create a satisfactory thermal climate.

Abstract [sv]

På senare tid har applikationen av samverkande strålar i ventilationsdesign studerats. Likaså har många studier utförts över potentialen för variabelflödessystem (VAV) för att reducera ventilationssystemets energianvändning. Den här studien utvärderar kombinationen av samverkande strålventilation (CJV) och VAV, både i flödesbeteendet i donets närområde och dess inverkan på den termiska komforten, luftkvaliteten och energieffektiviteten i konferens- och klassrumsmiljöer. För studierna i klassrumsmiljö med CJV och VAV utfördes två experimentella studier, med varierande värmelaster, tilluftstemperaturer och luftflöden. I de två experimentella studierna mättes luftens medelålder, lufthastigheten och temperaturen i vistelsezonen. Båda studierna visar att CJV har högre energieffektivitet och luftkvalitet än konventionell omblandande ventilation. De största effekterna av lägre tilluftstemperaturer är högre lufthastigheter och lägre lufttemperaturer i vistelsezonen p.g.a. högre energieffektivitet. CJV producerar ett jämnt termiskt klimat vid låga flöden (<4.2 omsättningar per timme) och ett stratifierat termiskt klimat vid högre luftflöden. Den termiska komforten var liknande den for konventionell omblandande ventilation och mindre temperaturgradienter än deplacerande ventilation. Undersökningen av CJV med VAV i en konferensrumsmiljö baserades på tre kombinerade experimentella och numeriska studier. Den första fokuserade på hastighetsprofilerna från CJV-donen. Resultaten användes sedan som gränsvillkor i de två andra studierna. Vid den andra studien mättes de sammanfogade strålarnas utveckling i närområdet och luft- respektive temperaturförhållandena i vistelsezonen för sex fall med olika tilluftstemperaturer, flöden och dysmatriskonfigurationer. Resultaten användes för att validera den numeriska modellen, som användes i den sista studien. Den sista studien var en parametrisk numerisk studie som använde response-surfacemetoden för att undersöka effekten av fyra designvariabler: värmelast, antal dysor, flöde och tilluftstemperatur, på responsvariablernas energieffektivitet, luftkvalitet och termiska komfort. Resultaten visar att luftkvaliteten ökar med högre luftflöden. Energieffektiviteten har en negativ korrelation till värmelasten, men en positiv korrelation till luftflödet, vilket leder till en stabil ventilationseffektivitet på 110%, eftersom VAV-systemet ökar luftflödet när värmelasten ökar. Resultaten visar även att om ett VAV-system är inställt för att skapa jämn temperatur i vistelsezonen, är den termiska komforten mest beroende på kombinationen av CLO-värdet och spannet mellan max- och min-luftflödena. Vid låga CLOvärden, behöver spannet på luftflödet ökas för att skapa ett tillfredställande termiskt klimat>(<4.2 omsättningar per timme) och ett stratifierat termiskt klimat vid högre luftflöden. Den termiska komforten var liknande den for konventionell omblandande ventilation och mindre temperaturgradienter än deplacerande ventilation. Undersökningen av CJV med VAV i en konferensrumsmiljö baserades på tre kombinerade experimentella och numeriska studier. Den första fokuserade på hastighetsprofilerna från CJV-donen. Resultaten användes sedan som gränsvillkor i de två andra studierna. Vid den andra studien mättes de sammanfogade strålarnas utveckling i närområdet och luft- respektive temperaturförhållandena i vistelsezonen för sex fall med olika tilluftstemperaturer, flöden och dysmatriskonfigurationer. Resultaten användes för att validera den numeriska modellen, som användes i den sista studien. Den sista studien var en parametrisk numerisk studie som använde response-surfacemetoden för att undersöka effekten av fyra designvariabler: värmelast, antal dysor, flöde och tilluftstemperatur, på responsvariablernas energieffektivitet, luftkvalitet och termiska komfort. Resultaten visar att luftkvaliteten ökar med högre luftflöden. Energieffektiviteten har en negativ korrelation till värmelasten, men en positiv korrelation till luftflödet, vilket leder till en stabil ventilationseffektivitet på 110%, eftersom VAV-systemet ökar luftflödet när värmelasten ökar. Resultaten visar även att om ett VAV-system är inställt för att skapa jämn temperatur i vistelsezonen, är den termiska komforten mest beroende på kombinationen av CLO-värdet och spannet mellan max- och min-luftflödena. Vid låga CLOvärden, behöver spannet på luftflödet ökas för att skapa ett tillfredställande termiskt klimat.

Place, publisher, year, edition, pages
Gävle: Gävle University Press, 2022. p. 91
Series
Doctoral thesis ; 33
Keywords
Confluent jets, Air distribution system, Air supply device, Ventilation performance, Indoor air quality, Thermal comfort, Experimental study, Computational fluid dynamics (CFD), Variable air volume., confluent jets, luftdistributionssystem, tilluftsdon, ventilationsprestanda, inomhusluftkvalitet, termisk komfort, experimentell studie, Computational fluid dynamics (CFD), variabelflödessystem
National Category
Energy Engineering
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-40225 (URN)978-91-88145-98-7 (ISBN)978-91-88145-99-4 (ISBN)
Public defence
2022-12-06, 99:131, Gävle, 09:15 (English)
Opponent
Supervisors
Funder
Knowledge Foundation
Available from: 2022-11-15 Created: 2022-10-10 Last updated: 2024-04-11Bibliographically approved
Andersson, H., Kabanshi, A., Cehlin, M. & Moshfegh, B. (2020). On the ventilation performance of low momentum confluent jets supply device in a classroom. Energies, 13(20), Article ID 5415.
Open this publication in new window or tab >>On the ventilation performance of low momentum confluent jets supply device in a classroom
2020 (English)In: Energies, E-ISSN 1996-1073, Vol. 13, no 20, article id 5415Article in journal (Refereed) Published
Abstract [en]

The performance of three different confluent jets ventilation (CJV) supply devices was evaluated in a classroom environment concerning thermal comfort, indoor air quality (IAQ) and energy efficiency. The CJV supply devices have the acronyms: high-momentum confluent jets (HMCJ), low-momentum confluent jets (LMCJ) and low-momentum confluent jets modified by varying airflow direction (LMCJ-M). A mixing ventilation (MV) slot jet (SJ) supply device was used as a benchmark. Comparisons were made with identical set-up conditions in five cases with different supply temperatures (TS) (16–18 °C), airflow rates (2.2–6.3 ACH) and heat loads (17–47 W/m2). Performances were evaluated based on DR (draft rating), PMV (predicted mean vote), ACE (air change effectiveness) and heat removal effectiveness (HRE). The results show that CJV had higher HRE and IAQ than MV and LMCJ/LMCJ-M had higher ACE than HMCJ. The main effects of lower Ts were higher velocities, DR (HMCJ particularly) and HRE in the occupied zone as well as lower temperatures and PMV-values. HMCJ and LMCJ produce MV conditions at lower airflow rates (<4.2 ACH) and non-uniform conditions at higher airflow rates. LMCJ-M had 7% higher HRE than the other CJV supply devices and produced non-uniform conditions at lower airflow rates (<3.3 ACH). The non-uniform conditions resulted in LMCJ-M having the highest energy efficiency of all devices.

Place, publisher, year, edition, pages
MDPI, 2020
Keywords
experimental investigations, confluent jets ventilation, mixing ventilation, ventilation efficiency, thermal comfort, heat removal effectiveness
National Category
Energy Engineering
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-34142 (URN)10.3390/en13205415 (DOI)000586859800001 ()2-s2.0-85093099946 (Scopus ID)
Funder
Knowledge Foundation, 20120273
Available from: 2020-10-16 Created: 2020-10-16 Last updated: 2024-04-11Bibliographically approved
Andersson, H. (2019). Numerical and experimental study of confluent jets supply device with variable airflow. (Licentiate dissertation). Gävle: Gävle University Press
Open this publication in new window or tab >>Numerical and experimental study of confluent jets supply device with variable airflow
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In recent years, application of confluent jets for design of ventilation supply devices has been studied. Similarly, numerus studies have been made on the potential and application of variable air volume (VAV) in order to reduce the energy demand of ventilation systems. This study investigates the combination of supply devices based on confluent jets and VAV, both in terms of the nearfield flow behavior of the device and the impact on thermal comfort, indoor air quality and energy efficiency on a classroom-level space when the airflow rate is varied.

The method used in this study is an experimental field study where the confluent jets-based supply devices were compared to the previously installed displacement ventilation. The field study evaluated the energy efficiency, thermal comfort and indoor air quality of the two systems. In the case of the confluent jets supply devices, airflow rate was varied in order to see what impact the variation had on the performance of the system for each airflow rate. Furthermore, the confluent jets supply devices were investigated both experimentally and numerically in a well insulated test room to get high resolution data on the particular flow characteristics for this type of supply device when the airflow rate is varied. The results from the field study show nearly uniform distribution of the local mean age of air in the occupied zone, even in the cases of relatively low airflow rates. The airflow rates have no significant effect on the degree of mixing. The thermal comfort in the classroom was increased when the airflow rate was adapted to the heat load compared to the displacement system. The results lead to the conclusion that the combination of supply devices based on confluent jets can reduce energy usage in the school while maintaining indoor air quality and increasing the thermal comfort in the occupied zone.

The results from the experimental and numerical study show that the flow pattern and velocity in each nozzle is directly dependent on the total airflow rate. However, the flow pattern does not vary between the three different airflow rates. The numerical investigation shows that velocity profiles for each nozzle have the same pattern regardless of the airflow rate, but the magnitude of the velocity profile increases as the airflow increases. Thus, a supply device of this kind could be used for variable air volume and produce confluent jets for different airflow rates.

The results from both studies show that the airflow rate does not affect the distribution of the airflow on both near-field and room level. The distribution of air is nearly uniform in the case of the near-field results and the room-level measurement shows a completely uniform degree of mixing and air quality in the occupied zone for each airflow rate. This means that there is potential for combining these two schemes for designing air distribution systems with high energy efficiency and high thermal comfort and indoor air quality.

Abstract [sv]

Under senare tid har applikation av Confluent jets för design av tilluftsdon studerats. Många studier har även utförts över potentialen av att applicera variabelt luftflöde (VAV) för att minska energianvändningen i ventilationssystem. Denna studie undersöker möjligheten att kombinera Confluent jets-don med VAV, både med avseende på den lokala flödesbilden och dess påverkan på termisk komfort, luftkvalitet och energieffektivitet i en klassrumsmiljö där luftflödes varieras.

Denna studie baseras dels på en experimentell fältstudie där tilluftsdon baserade på Confluents jets jämfördes med befintliga deplacerande tilluftsdon. Fältstudien utvärderade energieffektiviteten, den termiska komforten och luftkvaliteten för båda typerna av tillluftsdon. Confluent jets-donen testades under varierat luftflöde för att se påverkan av flödesvariationen på ventilationens prestation under de olika flödena. Utöver fältstudien testades Confluent jets-donen experimentellt och numeriskt i ett välisolerat test-rum för få den detaljerade flödeskarakteristiken för den här typen tilluftsdon vid varierat luftflöde.

Resultaten från fältstudien visar på en jämn fördelning av den lokala luftsmedelåldern i vistelsezonen, även för fallen med relativt låga luftflöden. Luftflöden har ingen signifikant effekt på omblandningen. Den termiska komforten i klassrummet ökade när luftflödet anpassades efter värmelasten jämfört med de deplacerande donen. Slutsatsen från fältstudien är att kombinationen av VAV och Confluent jets-don kan användas för att minska energianvändningen på skolan och bevara luftkvaliteten och den termiska komforten i vistelsezonen.

Resultaten från den experimental och numeriska studien visar luftflödet och lufthastigheten i varje enskild dysa är direkt beroende på det totala luftflödet genom donet. Dock är flödesfördelningen mellan dysorna oberoende av de tre olika luftflödena. Den numeriska undersökningen visar att flödesprofilen för varje dysa är konstant trots att flödet varieras, men amplituden för varje profil ökar med en höjning av luftflödet. Det betyder att tilluftsdon av den här typen kan användas med VAV för att producera Confluent jets för olika luftflöden.

Resultaten från båda studierna visar att luftflöde inte påverkar fördelningen av luften vare sig längs luftdonen eller på rumsnivå. Fördelningen av luften är nästan helt jämn längs donen och på rumsnivå är omblandningen och luftkvalitet den samma för varje luftflöde. Det betyder att det finns potential för att kombinera det här två teknikerna för att designa luftdistribueringssystem med hög energieffektivitet och hög termisk komfort med god luftkvalitet.

Place, publisher, year, edition, pages
Gävle: Gävle University Press, 2019. p. 42
Series
Studies in the Research Profile Built Environment. Licentiate thesis ; 6
Keywords
Confluent jets, Air distribution system, Air supply device, Ventilation performance, Indoor air quality, Thermal comfort, Experimental study, Laser Doppler Anemometry (LDA), Computational fluid dynamics (CFD), Shear stress transport (SST k – ω), confluent jets, luftdistributionssystem, tilluftsdon, ventilationsprestanda, inomhusluftkvalitet, termisk komfort, experimentell studie, Laser-Doppler-anemometri (LDA), Computational fluid dynamics (CFD), turbulens model (SST k – ω)
National Category
Energy Engineering
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-29271 (URN)978-91-88145-36-9 (ISBN)978-91-88145-37-6 (ISBN)
Presentation
2019-05-09, 13:111, Kungsbäcksvägen 47, Gävle, 13:00
Opponent
Supervisors
Available from: 2019-04-09 Created: 2019-02-13 Last updated: 2024-04-11Bibliographically approved
Andersson, H., Cehlin, M. & Moshfegh, B. (2018). Experimental and numerical investigations of a new ventilation supply device based on confluent jets. Building and Environment, 137, 18-33
Open this publication in new window or tab >>Experimental and numerical investigations of a new ventilation supply device based on confluent jets
2018 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 137, p. 18-33Article in journal (Refereed) Published
Abstract [en]

In developed countries, heating, ventilation, air conditioning (HVAC) systems account for more than 10% of national energy use. The primary function of a HVAC system is to create proper indoor environment. A number of ventilation strategies have been developed to minimize HVAC systems’ energy use whilst still maintaining a good indoor environment. Among these strategies are confluent jet ventilation and variable air volume. In this study, an air supply device with a novel nozzle design that uses both of the above-mentioned strategies was investigated both experimentally and numerically at three different airflow rates. The results from the numerical investigation using the SST k - ω turbulence model regarding velocities and flow patterns are validated by experimental data carried out by Laser Doppler Anemometry. The results from both studies show that the flow pattern and velocity in each nozzle is directly dependent on the total airflow rate. However, the flow pattern does not vary between the three different airflow rates. The numerical investigation shows that velocity profiles for each nozzle have the same pattern regardless of the airflow rate, but the magnitude of the velocity profile increases as the airflow increases. Thus, a supply device of this kind could be used for variable air volume and produce confluent jets for the airflow rates investigated.

Keywords
Confluent jets, Laser Doppler anemometry, SST k, Validation study, Ventilation supply device, ω turbulence model
National Category
Energy Engineering
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-26571 (URN)10.1016/j.buildenv.2018.03.038 (DOI)000433649700003 ()2-s2.0-85044917956 (Scopus ID)
Funder
Knowledge Foundation
Note

Funding: University of Gavle, Repus Ventilation AB and the Knowledge Foundation

Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2024-05-20Bibliographically approved
Andersson, H., Cehlin, M. & Moshfegh, B. (2016). Energy-Saving Measures in a Classroom Using Low Pressure Drop Ceiling Supply Device: A Field Study. In: 2016 ASHRAE Winter Conference Papers: . Paper presented at ASHRAE Winter Conference, 23-27 January 2016, Orlando, FL, USA. ASHRAE
Open this publication in new window or tab >>Energy-Saving Measures in a Classroom Using Low Pressure Drop Ceiling Supply Device: A Field Study
2016 (English)In: 2016 ASHRAE Winter Conference Papers, ASHRAE, 2016Conference paper, Published paper (Refereed)
Abstract [en]

Between 1990 and 2006 the energy use by ventilation systems in Swedish schools doubled. This is explained by high airflows in schools because of the high occupant density. Studies show that 87% of Swedish schools use constant air volume (CAV), and it is estimated that a change to variable air volume (VAV) could save 0.12-0.33 TWh (4.1*10(12) - 1.1*10(13) Btu) per year. Therefore the aim of this study is to investigate whether it is possible to replace displacement ventilation (DV) with mixing ventilation (MV) to create a comfortable indoor climate in a typical classroom and at the same time decrease the energy use by using VAV and Low Pressure Drop Ceiling Supply Device (LPDCSD). The study used two LPDCSDs which consist of circular channels with 190/228 round jets placed in an interlocking pattern, with a horizontal one/two-way-direction. The field study was carried out in a school which is intended to be extensively renovated. The school currently has DV and CAV. The study was carried out by installing MV with LPDCSD in one of the typical classrooms. Several different air-flow rates were investigated using tracer-gas technology to measure the local mean age of the air in the occupied zone. Simultaneously, thermal comfort and vertical temperature gradients were measured in the room. The results show nearly uniform distribution of the local mean age of air in the occupied zone, even in the cases of relatively low air-flow rates. Since the mixing of air is more or less the same in the entire occupied zone VAV can be used to reduce air-flow rate based on the desired CO2-level. Because of the number of students in each classroom and the fact that changes in air-flow rates have no significant effect on the degree of mixing, it is possible to reduce the air-flow rates for extended periods of time. Finally, since the LPDCSD has a lower pressure-drop than the currently used supply devices and it is possible to use VAV to lower the airflows in cases with reduced heat loads, it is possible to significantly reduce the energy usage in the school while maintaining the IAQ, increasing the thermal comfort and the available floor area of the occupied zone.

Place, publisher, year, edition, pages
ASHRAE, 2016
Series
ASHRAE Conference Papers, ISSN 2378-2129
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-27424 (URN)000427879200060 ()978-1-939200-13-6 (ISBN)
Conference
ASHRAE Winter Conference, 23-27 January 2016, Orlando, FL, USA
Available from: 2018-06-27 Created: 2018-06-27 Last updated: 2024-04-11Bibliographically approved
Andersson, H.An Investigation Concerning Optimal Design of Confluent Jet Ventilation with Variable Air Volume.
Open this publication in new window or tab >>An Investigation Concerning Optimal Design of Confluent Jet Ventilation with Variable Air Volume
(English)Manuscript (preprint) (Other academic)
National Category
Civil Engineering
Identifiers
urn:nbn:se:hig:diva-40198 (URN)
Funder
Knowledge Foundation
Available from: 2022-10-10 Created: 2022-10-10 Last updated: 2024-04-11Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7926-7378

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