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Improving the performance of heat valve ventilation system: A study on the provided thermal environment
Aalborg Univ, Danish Bldg Res Inst, AC Meyers Vaenge 15, DK-2450 Copenhagen SV, Denmark..
Aalborg Univ, Danish Bldg Res Inst, AC Meyers Vaenge 15, DK-2450 Copenhagen SV, Denmark..
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.ORCID iD: 0000-0001-7032-3049
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
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2019 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 164, article id UNSP 106338Article in journal (Refereed) Published
Abstract [en]

The current study presents and evaluates the performance of two types of supply air terminal devices applied in a heat valve ventilation (HVV) system with regard to the provided thermal environment in a room heated and ventilated by the HVV system. To that end, air temperature and air velocity patterns and local thermal discomfort due to draught were studied both experimentally and numerically. Using numerical simulations, parametric analysis was carried out for investigating the provided indoor thermal environment for a wider range of boundary conditions. The considered parameters included the influence of cold vertical surfaces, supply airflow rate and temperature, and room heating energy demand. The results showed that both of the applied air terminal devices could avoid temperature stratification within the occupied zone. The maximum air temperature difference between 0.1 and 1.8 m above the floor was 2.1 degrees C when using a circular valve placed in the external wall below the window and 2.6 degrees C in the case when the air was supplied through three nozzles located in the wall opposite to the window in the upper part of the room. In general, placing the air terminal device below the window provided more uniform air temperature distribution and contributed to the prevention of downdraught caused by a cold window surface. The outcomes of this study are relevant to selecting and designing ventilation and air heating systems for low-energy buildings.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD , 2019. Vol. 164, article id UNSP 106338
Keywords [en]
Air heating, Air terminal device, Thermal environment, Air distribution, Temperature stratification, Draught rate
National Category
Building Technologies
Research subject
Civil and Architectural Engineering, Building Service and Energy Systems
Identifiers
URN: urn:nbn:se:kth:diva-260993DOI: 10.1016/j.buildenv.2019.106338ISI: 000484515300016Scopus ID: 2-s2.0-85070748376OAI: oai:DiVA.org:kth-260993DiVA, id: diva2:1359763
Note

QC 20191010

Available from: 2019-10-10 Created: 2019-10-10 Last updated: 2019-11-26Bibliographically approved
In thesis
1. Ventilation Performance in Operating Rooms: A Numerical Assessment
Open this publication in new window or tab >>Ventilation Performance in Operating Rooms: A Numerical Assessment
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Surgical site infections (SSIs) remain one of the most challenging postoperative complicationsof healthcare and threaten the lives of millions of patients each year. Current evidence hasshown a positive relationship between the airborne concentration of bacteria-carryingparticles (BCPs) in the operating room (OR) and the rate of infections. The OR ventilation iscrucial for mitigating the dispersion of airborne bacterial contaminants and thus controllingthe risk of SSIs. A variety of ventilation schemes have been developed for OR use. Each haspros and cons and may be better suited than another for operations under certain conditions.The proper functioning of OR ventilation is also affected by external and internal disruptions.By applying Computational Fluid Dynamics (CFD), the present study investigates the airflowand contaminant distribution in ORs under different conditions.The airflow distribution is of critical importance in removing or diluting airbornecontaminants. The conventional mixing ventilation is not able to reliably create an ultracleanenvironment. The usage of mixing ventilation in infection-prone surgery should be limited,especially when a large surgical team is involved. Laminar airflow (LAF) ventilation demandsa sufficient airflow rate to achieve desired performance. Temperature-controlled airflow(TAF) ventilation represents an effective ventilation scheme that can serve as an energyefficientalternative to LAF.Door openings have a detrimental impact on the microbiological cleanliness of the OR. Thetemperature in the OR and adjacent space should be well controlled to minimize the interzonalcontaminant transfer. Temporarily reducing the OR exhaust flow during door operationforms a directional airflow towards the adjacent space, which is found to be an effectivesolution to ensure the isolation.Surgical lamps serve as physical obstructions in the airflow path and significantly deterioratethe performance of LAF ventilation. It is highly recommended to improve the shape anddesign of the lamps in the LAF ventilation. TAF is found to be less sensitive to the presenceof surgical lamps in the airflow path. The buoyancy-driven airflow used by TAF is morecapable of circumventing obstacles than the inertia-driven flow used by LAF. Thermal plumesdeveloped from the surgical equipment in the OR have the potential to distort the buoyancydrivenairflow in TAF.The thesis conducts a comprehensive literature review of important topics in OR ventilation.The present study enhances the understanding of the strengths and limitations of differentventilation schemes and increases the knowledge of the design and usage of OR ventilation.

Abstract [sv]

Postoperativa infektioner tillhör idag de mest utmanande komplikationerna inom sjukvården. De utsätter årligen miljontals patienter för allvarlig hälsofara. Bevis finns för ett samband mellan luftburen koncentration av bakteriebärande partiklar i operationssalen och infektionsfrekvensen. Ventilationen i operationssalen är avgörande för att minimera spridningen av luftburna bakteriella föroreningar och därmed kontrollera risken för postoperativ infektion. För ventilation i operationsrum har olika luftföringsprinciper utvecklats. Dessa har för- och nackdelar och vissa kan vara bättre lämpade än andra under givna förhållanden. Ventilationens funktion påverkas också av yttre och inre störningar. Med numeriska beräkningsmetoder (CFD) undersöks i denna avhandling luftflöden och föroreningsspridning i operationsrum.

Såväl luftflödets fördelning i rummet som luftflödets volym är av avgörande betydelse för eliminering och utspädning av luftburna föroreningar. Konventionell omblandande ventilation har såväl teoretiska som praktiska begränsningar i detta sammanhang och dess användning bör därför begränsas vid infektionsbenägen operation. Detta gäller särskilt vid stora operationsteam. Ventilation med så kallat laminärt luftflöde (LAF) kräver tillräckligt luftflöde för att uppnå önskat resultat. Ventilation med temperaturstyrt luftflöde (TAF) har befunnits vara ett (energi)effektivt alternativ till LAF.

Dörröppningar till operationssalen har negativ inverkan på den mikrobiologiska renheten i rummet. Temperaturen i operationsrummet och angränsande utrymme bör kontrolleras väl för att minimera överföring av föroreningar mellan zonerna. Genom att tillfälligt reducera frånluftflödet i operationsrummet under dörrdrift bildas ett riktat luftflöde mot intilliggande utrymmen som effektiv visat sig säkerställa isoleringen.

Vissa kirurgiska lampor fungerar som fysiska hinder i luftflödesvägen och försämrar avsevärt funktionen vid LAF-ventilation. Därför rekommenderas starkt att inte förbise lampans form och placering. TAF-ventilation har visat sig vara mindre känslig för kirurgiska lampor i luftflödesvägen. Det termiskt drivna luftflödet vid TAF syns mera kapabelt att klara hinder än tröghetsdrivet flöde vid LAF. Värmeplymer som den kirurgiska utrustningen genererar i operationsrummet kan påverka det termiskt drivna luftflödet vid TAF.

Avhandlingen innehåller en omfattande litteraturstudie inom området. Avhandlingen ökar förståelsen för olika ventilationsprincipers funktion och kunskapen om hur ventilation skall användas i sjukhusmiljöer.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. 79
Series
TRITA-ABE-DLT ; 1939
Keywords
operating room ventilation, bacteria-carrying particles, laminar airflow, mixing ventilation, temperature-controlled airflow, computation fluid dynamics, Lagrangian particle tracking
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering; Civil and Architectural Engineering, Fluid and Climate Theory
Identifiers
urn:nbn:se:kth:diva-263301 (URN)978-91-7873-338-5 (ISBN)
Public defence
2019-11-27, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20191105

Available from: 2019-11-05 Created: 2019-11-05 Last updated: 2019-11-05Bibliographically approved

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Sadeghian, ParastooWang, CongSadrizadeh, Sasan

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