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Ploskic, A., Wang, Q. & Sadrizadeh, S. (2018). Mapping Relevant Parameters for Efficient Operation of Low-Temperature Heating Systems in Nordic Single-Family Dwellings. Applied Sciences, 8(10), Article ID 1973.
Open this publication in new window or tab >>Mapping Relevant Parameters for Efficient Operation of Low-Temperature Heating Systems in Nordic Single-Family Dwellings
2018 (English)In: Applied Sciences, E-ISSN 2076-3417, Vol. 8, no 10, article id 1973Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to map the parameters that have the greatest impact on the environmental impact of heating systems usually used in Nordic single-family dwellings. The study focused on mapping the technical requirements for efficient operation of heating systems in a broader context. The results suggest that the ability of a heating system to be operated with a low-temperature water supply depends to a large extent on the heating demand of a building. It was shown that an increase in the water flow rate in hydronic circuits would significantly increase the thermal efficiency from analyzed heating systems. This increase would not increase the pumping power need, nor would it create noise problems in distribution network if the distribution pipes and thermostatic valves were properly selected. However, this increase in water flow rate improved the efficiency of considered closed-loop heat pump. It was further shown that the efficiency of the heat pump could be additionally improved by halving the energy needs for the domestic hot-water and circulators. The main conclusion from this study is that exergy usage, CO2 emission and thereby environmental impact are significantly lower for heating systems that are operated with small temperature drops.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
low-temperature heating, energy efficiency, CO2 emissions, heat pump, hydraulic losses, system analysis
National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-239111 (URN)10.3390/app8101973 (DOI)000448653700268 ()2-s2.0-85055107835 (Scopus ID)
Note

QC 20181120

Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2019-08-20Bibliographically approved
Wang, C., Holmberg, S. & Sadrizadeh, S. (2018). Numerical study of temperature-controlled airflow in comparison with turbulent mixing and laminar airflow for operating room ventilation. Building and Environment, 144, 45-56
Open this publication in new window or tab >>Numerical study of temperature-controlled airflow in comparison with turbulent mixing and laminar airflow for operating room ventilation
2018 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 144, p. 45-56Article in journal (Refereed) Published
Abstract [en]

Operating room (OR) ventilation is crucial for reducing airborne bacteria-carrying particles (BCPs) concentration and thus preventing post-operative infections. A variety of ventilation schemes have been introduced to ORs. This study explores the effectiveness of a newly developed ventilation scheme, temperature-controlled airflow (TAF), with respect to reducing BCPs distribution and sedimentation in an OR. Comparisons are made with the conventional turbulent mixing and laminar airflow (LAF) ventilation. The study is conducted using Computational Fluid Dynamics (CFD) and Lagrangian particle tracking (LPT), with numerical models validated against literature data. The results reveal that TAF represents reliable and effective ventilation and can serve as an energy-efficient alternative to the LAF systems. The results also show that increasing ventilation rates alone will not always result in better control of BCPs distribution. Airflow patterns play an important role in removing and diluting airborne BCPs, so a specific analysis is necessary to each design of OR ventilation.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
Operating room ventilation, Bacteria-carrying particles, Temperature-controlled airflow, Laminar airflow, Turbulent mixing ventilation
National Category
Construction Management
Identifiers
urn:nbn:se:kth:diva-238119 (URN)10.1016/j.buildenv.2018.08.010 (DOI)000447484300005 ()2-s2.0-85051404343 (Scopus ID)
Note

QC 20181205

Available from: 2018-12-05 Created: 2018-12-05 Last updated: 2018-12-05Bibliographically approved
Alsved, M., Civilis, A., Ekolind, P., Tammelin, A., Andersson, A. E., Jakobsson, J., . . . Londahl, J. (2018). Temperature-controlled airflow ventilation in operating rooms compared with laminar airflow and turbulent mixed airflow. Journal of Hospital Infection, 98(2), 181-190
Open this publication in new window or tab >>Temperature-controlled airflow ventilation in operating rooms compared with laminar airflow and turbulent mixed airflow
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2018 (English)In: Journal of Hospital Infection, ISSN 0195-6701, E-ISSN 1532-2939, Vol. 98, no 2, p. 181-190Article in journal (Refereed) Published
Abstract [en]

Aim: To evaluate three types of ventilation systems for operating rooms with respect to air cleanliness [in colony-forming units (cfu/m(3))], energy consumption and comfort of working environment (noise and draught) as reported by surgical team members. Methods: Two commonly used ventilation systems, vertical laminar airflow (LAF) and turbulent mixed airflow (TMA), were compared with a newly developed ventilation technique, temperature-controlled airflow (T(c)AF). The cfu concentrations were measured at three locations in an operating room during 45 orthopaedic procedures: close to the wound (<40 cm), at the instrument table and peripherally in the room. The operating team evaluated the comfort of the working environment by answering a questionnaire. Findings: LAF and T(c)AF, but not TMA, resulted in less than 10 cfu/m(3) at all measurement locations in the room during surgery. Median values of cfu/m(3) close to the wound (250 samples) were 0 for LAF, 1 for T(c)AF and 10 for TMA. Peripherally in the room, the cfu concentrations were lowest for T(c)AF. The cfu concentrations did not scale proportionally with airflow rates. Compared with LAF, the power consumption of T(c)AF was 28% lower and there was significantly less disturbance from noise and draught. Conclusion: T(c)AF and LAF remove bacteria more efficiently from the air than TMA, especially close to the wound and at the instrument table. Like LAF, the new T(c)AF ventilation system maintained very low levels of cfu in the air, but T(c)AF used substantially less energy and provided a more comfortable working environment than LAF. This enables energy savings with preserved air quality.

Place, publisher, year, edition, pages
W B SAUNDERS CO LTD, 2018
Keywords
Surgical site infection, BioTrak, Fluorescence, Energy efficiency, Temperature-controlled, ventilation, Air sampling
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-223799 (URN)10.1016/j.jhin.2017.10.013 (DOI)000425104000013 ()29074054 (PubMedID)2-s2.0-85034808911 (Scopus ID)
Funder
Swedish Research Council Formas, 2014-1460Swedish Energy Agency, 2016-004864
Note

QC 20180307

Available from: 2018-03-07 Created: 2018-03-07 Last updated: 2018-03-07Bibliographically approved
Sadrizadeh, S., Nejad Ghafar, A., Halilovic, A. & Håkansson, U. (2017). Numerical, Experimental and Analytical Studies on Fluid Flow through a Marsh Funnel. Journal of Applied Fluid Mechanics, 10(6), 1501-1507
Open this publication in new window or tab >>Numerical, Experimental and Analytical Studies on Fluid Flow through a Marsh Funnel
2017 (English)In: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 10, no 6, p. 1501-1507Article in journal (Refereed) Published
Abstract [en]

This paper presents the application of computational fluid dynamics technique in civil and underground industries to evaluate fluid behaviour in a Marsh funnel. The numerical approach, based on computational fluid dynamics, simulated an incompressible two-phase Newtonian flow by means of the Volume-of-Fluid method. A complementary analytical proposed which provided a quick, field-ready method to assess the fluid field in the Marsh funnel. A supplemental experimental effort evaluated the results obtained from both the analytical calculation and numerical simulation. Results showed that the application of computational fluid dynamics technique gives the desired results in studying fluid flows in civil and underground industries. Proposed analytical solution is also capable of accurately predicting the fluid flow and thus can complement the experimental and numerical approaches. Further, the proposed analytical approach can be an alternative method for faster evaluation of fluid, although it needs to be calibrated with either the numerical or the experimental studies.

Place, publisher, year, edition, pages
ISFAHAN UNIV TECHNOLOGY, 2017
Keywords
Multiphase flow, Marsh funnel, CFD, Analytical solution, Experimental approach, Fluid flow simulation, Discharge coefficient, Cement-based grout
National Category
Applied Mechanics Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-217475 (URN)000413507000001 ()2-s2.0-85030983634 (Scopus ID)
Note

QC 20171117

Available from: 2017-11-17 Created: 2017-11-17 Last updated: 2018-06-19Bibliographically approved
Sadrizadeh, S. & Ekolind, P. (2016). A new principle of ventilation system for operating rooms: Temperature-Controlled Air Flow. In: Proceedings of 12th REHVA world congress, CLIMA Conference. May 22-25, 2016; Aalborg - Denmark: . Paper presented at CLIMA 2016.
Open this publication in new window or tab >>A new principle of ventilation system for operating rooms: Temperature-Controlled Air Flow
2016 (English)In: Proceedings of 12th REHVA world congress, CLIMA Conference. May 22-25, 2016; Aalborg - Denmark, 2016Conference paper, Published paper (Refereed) [Artistic work]
Keywords
Temperature-Controlled Airflow Ventilation system, Operating theatre, Computational fluid dynamics, Infection, Airborne contamination
National Category
Medical Engineering Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-192000 (URN)
External cooperation:
Conference
CLIMA 2016
Note

QC 20160912

Available from: 2016-09-04 Created: 2016-09-04 Last updated: 2016-09-12Bibliographically approved
Sadrizadeh, S. (2016). Application of computational fluid dynamics in hospital operating theatre. In: Proceedings of the 47th R3 NORDIC SYMPOSIUM with EXHIBITION Scandic Sydhavnen, Copenhagen, 5-6 September 2016: . Paper presented at R3Nordic 2016.
Open this publication in new window or tab >>Application of computational fluid dynamics in hospital operating theatre
2016 (English)In: Proceedings of the 47th R3 NORDIC SYMPOSIUM with EXHIBITION Scandic Sydhavnen, Copenhagen, 5-6 September 2016, 2016Conference paper, Published paper (Refereed)
Keywords
Computation Fluid Dynamics, Active/Passive air sampling method, contaminant dispersion, thermal comfort
National Category
Civil Engineering Mechanical Engineering Medical and Health Sciences
Identifiers
urn:nbn:se:kth:diva-192081 (URN)
Conference
R3Nordic 2016
Note

QC 20160912

Available from: 2016-09-05 Created: 2016-09-05 Last updated: 2016-09-16Bibliographically approved
Sadrizadeh, S. (2016). Design of Hospital Operating Room Ventilation using Computational Fluid Dynamics. (Doctoral dissertation). Stockhomlm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Design of Hospital Operating Room Ventilation using Computational Fluid Dynamics
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Utforma operationssalars ventilationssystem med hjälp av beräkningsströmningsmekanik
Abstract [en]

The history of surgery is nearly as old as the human race. Control of wound infection has always been an essential part of any surgical procedure, and is still an important challenge in hospital operating rooms today. For patients undergoing surgery there is always a risk that they will develop some kind of postoperative complication.

It is widely accepted that airborne bacteria reaching a surgical site are mainly staphylococci released from the skin flora of the surgical staff in the operating room and that even a small fraction of those particles can initiate a severe infection at the surgical site.  Wound infections not only impose a tremendous burden on healthcare resources but also pose a major threat to the patient. Hospital-acquired infection ranks amongst the leading causes of death within the surgical patient population. A broad knowledge and understanding of sources and transport mechanisms of infectious particles may provide valuable possibilities to control and minimize postoperative infections.

This thesis contributes to finding solutions, through analysis of such mechanisms for a range of ventilation designs together with investigation of other factors that can influence spread of infection in hospitals, particularly in operating rooms.

The aim of this work is to apply the techniques of computational fluid dynamics in order to provide better understanding of air distribution strategies that may contribute to infection control in operating room and ward environments of hospitals, so that levels of bacteria-carrying particles in the air can be reduced while thermal comfort and air quality are improved.

 A range of airflow ventilation principles including fully mixed, laminar and hybrid strategies were studied. Airflow, particle and tracer gas simulations were performed to examine contaminant removal and air change effectiveness. A number of further influential parameters on the performance of airflow ventilation systems in operating rooms were examined and relevant measures for improvement were identified.

It was found that airflow patterns within operating room environments ranged from laminar to transitional to turbulent flows. Regardless of ventilation system used, a combination of all airflow regimes under transient conditions could exist within the operating room area. This showed that applying a general model to map airflow field and contaminant distribution may result in substantial error and should be avoided.

It was also shown that the amount of bacteria generated in an operating room could be minimized by reducing the number of personnel present. Infection-prone surgeries should be performed with as few personnel as possible. The initial source strength (amount of colony forming units that a person emits per unit time) of staff members can also be substantially reduced, by using clothing systems with high protective capacity.

Results indicated that horizontal laminar airflow could be a good alternative to the frequently used vertical system. The horizontal airflow system is less sensitive to thermal plumes, easy to install and maintain, relatively cost-efficient and does not require modification of existing lighting systems. Above all, horizontal laminar airflow ventilation does not hinder surgeons who need to bend over the surgical site to get a good view of the operative field.

The addition of a mobile ultra-clean exponential laminar airflow screen was also investigated as a complement to the main ventilation system in the operating room. It was concluded that this system could reduce the count of airborne particles carrying microorganisms if proper work practices were maintained by the surgical staff.

A close collaboration and mutual understanding between ventilation experts and surgical staff would be a key factor in reducing infection rates. In addition, effective and frequent evaluation of bacteria levels for both new and existing ventilation systems would also be important.

Abstract [sv]

Tidigt i mänsklighetens utveckling har kirurgin funnits med i bilden. Hantering av infektioner har genom tiderna varit en oundviklig del av alla kirurgiska ingrepp, och finns kvar ännu idag som en viktig utmaning i operationssalar på sjukhus. För patienter som genomgår kirurgi finns alltid en risk att de efter ingreppet utvecklar någon behandlingsrelaterad komplikation.

Allmänt accepterat är att de luftburna bakterier som når operationsområdet huvudsakligen består av stafylokocker frigjorda från hudfloran av operationspersonalen i operationssalen, och att endast en liten del av dessa partiklar behövs för att initiera en allvarlig infektion i det behandlade området. Sårinfektioner innebär inte bara en enorm börda för hälso- och sjukvårdsresurser, utan utgör också en betydande risk för patienten. På sjukhus förvärvad infektion finns bland de främsta dödsorsakerna i kirurgiska patientgrupper.. En bred kunskap och förståelse av spridningsmekanismer och källor till infektionsspridande partiklar kan ge värdefulla möjligheter att kontrollera och minimera postoperativa infektioner. Denna avhandling bidrar till lösningar genom analys av en rad olika ventilationssystem tillsammans med undersökning av andra faktörer som kan påverka infektionsspridningen på sjukhus, främst i operationssalar.

Syftet med arbetet är att med hjälp av CFD-teknik (Computational Fluid Dynamics) få bättre förståelse för olika luftspridningsmekanismers betydelse vid ventilation av operationssalar och vårdinrättningar på sjukhus, så att halten av bacteriebärande partiklar i luften kan minskas samtidigt som termisk komfort och luftkvalité förbättras.

 Flera luftflödesprinciper för ventilation inklusive omblandade strömning, riktad (laminär) strömning och hybridstrategier har studerats. Simuleringar av luft-, partikel- och spårgasflöden gjordes för alla fallstudier för att undersöka partikelevakuering och luftomsättning i rummet. Flera viktiga parametrar som påverkar detta undersöktes och relevanta förbättringar  föreslås i samarbete med industrin.

Av resultaten framgår att mängden genererade bakterier i en operationssal  kan begränsas genom att minska antalet personer i operationsteamet. Infektionsbenägna operationer skall utföras med så lite personal som möjligt.

Den initiala källstyrkan (mängden kolonibildande enheter som en person avger per tidsenhet) från operationsteamet kan avsevärt minskas om högskyddande kläder används.

Av resultaten framgår också att ett horisontellt (laminärt) luftflöde kan vara ett bra alternativ till det ofta använda vertikala luftflödet. Ett horisontellt luftflöde är mindre känsligt för termisk påverkan från omgivningen, enkelt att installera och underhålla, relativt kostnadseffektivt och kräver vanligen ingen förändring av befintlig belysningsarmatur. Framför allt begränsar inte denna ventilationsprincip kirurgernas rörelsemönster. De kan luta kroppen över operationsområdet utan att hindra luftflödet. En flyttbar flexibel skärm för horisontell spridning av ultraren ventilationsluft i tillägg till ordinarie ventilation undersöktes också. Man fann att denna typ av tilläggsventilation kan minska antalet luftburna partiklar som bär mikroorganismer om operationspersonalen följer en strikt arbetsordning.

Bra samarbete och förståelse mellan ventilationsexperter och operationsteamet på sjukhuset är nyckeln till att få ner infektionsfrekvensen. Det är också viktigt med effektiva och frekventa utvarderingar av bakteriehalten i luften, för såväl nya  som befintliga ventilationssystem.

Place, publisher, year, edition, pages
Stockhomlm: KTH Royal Institute of Technology, 2016. p. 74
Series
TRITA-STKL ; 2015:01
Keywords
Computational Fluid Dynamics (CFD), Ventilation System, Hospital Operating Room, Bacteria Carrying Particle, Surgical Site Infection, Colony Forming Unit, Airborne Particle Control, Air Quality, Thermal Comfort, Active-Passive Air Sampling methods, Computational Fluid Dynamics (CFD), ventilationssystem, operationssal på sjukhus, bakteriebärande partikel, infektion i samband med operation, kolonibildande enhet, kontroll av luftburna partiklar, luftkvalitet, termisk komfort, aktiva-passiva provtagningsmetoder för luft
National Category
Mechanical Engineering Environmental Engineering Architecture
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-181053 (URN)978-91-7595-810-1 (ISBN)
Public defence
2016-02-22, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20160129

Available from: 2016-01-29 Created: 2016-01-27 Last updated: 2016-02-17Bibliographically approved
Sadrizadeh, S. & Holmberg, S. (2016). Evaluation of various turbulence models for indoor airflow prediction: a comparison study with experimental data. In: Proceedings of 9th International Conference on Indoor Air Quality Ventilation & Energy Conservation In Buildings. October 23-26, 2016; Seoul, Republic of Korea: . Paper presented at IAQVEC 2016.
Open this publication in new window or tab >>Evaluation of various turbulence models for indoor airflow prediction: a comparison study with experimental data
2016 (English)In: Proceedings of 9th International Conference on Indoor Air Quality Ventilation & Energy Conservation In Buildings. October 23-26, 2016; Seoul, Republic of Korea, 2016Conference paper, Published paper (Refereed) [Artistic work]
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-192001 (URN)
External cooperation:
Conference
IAQVEC 2016
Note

QC 20160912

Available from: 2016-09-04 Created: 2016-09-04 Last updated: 2016-09-12Bibliographically approved
Sadrizadeh, S. & Nielsen, P. V. (2016). Modelling of coughed droplets in a hospital ward. In: Proceedings of 12th REHVA world congress, CLIMA Conference. May 22-25, 2016; Aalborg - Denmark: . Paper presented at CLIMA 2016.
Open this publication in new window or tab >>Modelling of coughed droplets in a hospital ward
2016 (English)In: Proceedings of 12th REHVA world congress, CLIMA Conference. May 22-25, 2016; Aalborg - Denmark, 2016Conference paper, Published paper (Refereed) [Artistic work]
Keywords
Cough, Computational fluid dynamics, ventilation system, hospital ward
National Category
Medical Engineering Environmental Engineering Mechanical Engineering
Research subject
Engineering Mechanics; Applied and Computational Mathematics
Identifiers
urn:nbn:se:kth:diva-191999 (URN)
External cooperation:
Conference
CLIMA 2016
Note

QC 20160912

Available from: 2016-09-04 Created: 2016-09-04 Last updated: 2016-09-12Bibliographically approved
Sadrizadeh, S., Afshari, A., Karimipanah, T., Hakansson, U. & Nielsen, P. V. (2016). Numerical simulation of the impact of surgeon posture on airborne particle distribution in a turbulent mixing operating theatre. Building and Environment, 110, 140-147
Open this publication in new window or tab >>Numerical simulation of the impact of surgeon posture on airborne particle distribution in a turbulent mixing operating theatre
Show others...
2016 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 110, p. 140-147Article in journal (Refereed) Published
Abstract [en]

Airborne particles released from surgical team members are major sources of surgical site infections. To reduce the risk of such infections, ultraclean-zoned ventilation systems have been widely applied, as a complement to the ventilation of the main operating theatre. The function of ventilation in an operating theatre is usually determined without considering the influence of the staff members' posture and movements. The question of whether the surgeon's posture during an on-going operation will influence particle distribution within the surgical area has not yet been explored in depth or well documented. In the present study we analysed data from investigation of two positions (bending and straightened up), which represent the most common surgeon and staff-member postures. The investigation was performed by applying the computational fluid dynamics methodology to solve the governing equations for airflow and airborne particle dispersion. Ultraclean-zoned ventilation systems were examined as an addition to the conventional operating theatre. We examined three distinct source strengths (mean value of pathogens emitted from one person per second) due to the variety of staff clothing systems. In the upright posture, the screen units reduced the mean air counts of bacteria and the mean counts of sedimenting bacteria to a standard level for infection-prone surgeries in the surgical area. However, the performance of this system could be reduced drastically by improper Work experience. Surgical garments with a high protective capacity result in lower source strength and thus reduces the particle concentration within the surgical area. These results are useful for developing best practices to prevent or at least reduce the infection rate during a surgical intervention.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
CFD simulation, Operating theatre, Ventilation system, Bacteria-carrying particles, Clothing system, Colony-forming unit, Mobile ultraclean zonal-laminar airflow screen
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-197758 (URN)10.1016/j.buildenv.2016.10.005 (DOI)000388052500013 ()2-s2.0-84992209616 (Scopus ID)
Note

QC 20170110

Available from: 2017-01-10 Created: 2016-12-08 Last updated: 2017-11-29Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9361-1796

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