| 1. |
- Chen, Shih-Ying, et al.
(författare)
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Transport of Contaminated Agents in Hospital Wards - Exposure Control with a Personalized Healthcare Ventilation System: Numerical Study
- 2021
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Konferensbidrag (refereegranskat)abstract
- Contaminated agents in hospital wards are the source of nosocomial infections known as hospital-acquired infection (HAI) or healthcare-associated infections (HAIs). Ventilation plays an essential role in the spreading and minimizing the transport of airborne infectious diseases such as Covid-19 and SARS in the hospital ward. The goal of this study is to explore elimination strategies for an efficient removal of contaminated agents, targeting the influence of using local air diffuser and exhaust. Computational Fluid Dynamics (CFD) technique was used to model the airflow field and contamination distribution in the ward environment. Simulated results showed that the bacteria spread from a patient confined to his bed was limited and under certain conditions significantly eliminated. Consequently, a relatively high efficiency of particle removal and a moderated transmission were obtained. Thus, this strategy is able to shorten the exposure time of patient and healthcare staff, as a result, mitigating cross-infection risk at the hospital.
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| 2. |
- Lind, M. C., et al.
(författare)
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Minimizing the airborne particle migration to the operating room during door opening
- 2019
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Ingår i: Proceedings 10th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings, IAQVEC. - : Institute of Physics Publishing.
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Konferensbidrag (refereegranskat)abstract
- Airborne bacteria that enter an open wound during surgery can result in post-operative infections, commonly referred to as surgical site infections (SSIs). The level of contaminants is usually lower in the operating rooms (ORs) in contrast to adjacent corridors. Penetration of particles carrying bacteria through the doorway during a door opening gives rise to the OR contaminant level as door-opening and passage may occur every 2.5 minutes during a given surgical activity. The authors had previously conducted a successful research study to reduce the contaminant migration from an anteroom, through the doorway, into an Airborne Infection Isolation Room (AIIR). In contrast to the AIIRs, the ORs are usually over-pressured related to the surrounding environments. However, both ORs and AIIRs share the same interest in avoiding air exchange between the room and the adjacent space. This paper, built upon the previous research achievement, proposes an innovative design solution to reduce the bacteria penetration to the ORs during a door opening and staff passage. Previously achieved results from CFD simulation and laboratory measurement confirmed that installing a ventilation unit that supplies a high air volume into the OR through low-velocity wall diffusers, may significantly reduce the contaminant migration to the OR during door-opening activities.
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| 3. |
- Polak, Joanna, et al.
(författare)
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Improving the performance of heat valve ventilation system : A study on the provided thermal environment
- 2019
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Ingår i: Building and Environment. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-1323 .- 1873-684X. ; 164
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Rahnama, Samira, et al.
(författare)
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Cooling capacity of diffuse ceiling ventilation system and the impact of heat load and diffuse panel distribution
- 2020
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Ingår i: Building and Environment. - : Elsevier. - 0360-1323 .- 1873-684X. ; 185
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Tidskriftsartikel (refereegranskat)abstract
- Diffuse ceiling ventilation system is an air distribution system based on the low-impulse supply of air through the perforated panels installed as the suspended ceiling. A ceiling with diffuse supply typically consists of active and passive panels, where active panels allow airflow. Diffuse ceiling ventilation system has been proven to have a higher cooling capacity compared to conventional air distribution systems, e.g. mixing or displacement ventilation systems. Several parameters have an impact on the cooling capacity of the system though. The present research study evaluates the cooling capacity of the diffuse ceiling ventilation system in connection to two essential parameters, i.e. the distribution of heat load in the room and the distribution of active diffuse panels in the ceiling. The evaluation is based on full-scale experiments performed in a laboratory-controlled environment as well as numerical studies with Computational Fluid Dynamics (CFD) simulations. The cooling capacity of the system in several scenarios with different heat load and active diffuse panel distribution are compared under a certain thermal comfort condition. The results indicate the highest cooling capacity in the scenario with evenly distributed heat load in the room and compact distribution of active diffuse panels in the ceiling, while the active panels cover almost one-third of the suspended ceiling. The system is at its minimum cooling capacity in the scenario with compact heat load distribution in the room and disperse distribution of active diffuse panels in the ceiling.
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| 5. |
- Sadeghian, Parastoo
(författare)
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A new generation of hospital operating room ventilation
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Surgical site infection is responsible for 38 percent of reported infections after surgery. This infection increases mortality and treatment costs, and prolongs the hospitalization of patients. Bacteria-carrying particles are the main cause of surgical site infection and one of the main sources of these particles is skin fragments released from the surgical personnel during an ongoing surgery. Ventilation systems reduce the concentration of bacteria-carrying particles by supplying clean air in the operating room. The performance of operating room ventilation systems is affected by internal disruptions such as medical equipment, surgical lamps, number of staff and their behaviour during the surgery.Using computational fluid dynamics, this thesis investigates the airflow behaviour and distribution of the contamination in the operating room under the presence of various internal disruptions. In this regard, three common ventilation systems are considered: laminar airflow, turbulent mixing and temperature-controlled airflow ventilations. This study tries to overcome the weaknesses of the ventilation systems by providing sustainable solutions and continuously being in contact with design companies.It is common to use warming blankets to prevent reduction in the core body temperature of the patient during major surgeries. However, there is a major concern that these blankets disrupt the supplied airflow, which results in rising contaminant concentration. Most of the studies about warming blankets are clinical works and it is still not clear whether or not these blankets should be used. The results of the present study show that using warming blankets had no impact on increase of contamination level at the surgical zone. However, one common type of warming blanket – a forced-air warming blanket – can considerably increase the concentration of bacteria-carrying particles at the wound area if it becomes contaminated.The simulated results of the airflow field and particle tracking showed that the laminar airflow ventilation system was disturbed more easily by the local heat loads than overall heat loads in the operating room.Surgical lamps are considered as an obstacle in the supplied airflow path. These lamps create a stagnant area above the operating table and increase the contamination level. In this regard, a novel design of surgical lamp, a fan-mounted surgical lamp, was introduced to operating rooms.This device was used in the operating rooms equipped with laminar airflow and mixing ventilation system. The simulated results revealed that this lamp significantly reduced the contamination level at the operating table.Visualization techniques were adopted to teach and improve the understanding of surgical personnel about transmission of contaminated particles in operating rooms. Here, a virtual and augmented reality interface was used to visualize the impact of differences in ventilation principle, surgical staff constellation and work practice.
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| 6. |
- Sadeghian, Parastoo, et al.
(författare)
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Assessment of diffuse ceiling ventilation performance on transmission of airborne infectious diseases
- 2022
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Konferensbidrag (refereegranskat)abstract
- Ventilation systems have been widely used to satisfy the occupants' indoor air quality and thermally comfort conditions. Various air distribution systems have been developed to supply clean air, including mixing, displacement, and diffuse ceiling ventilation systems. Diffuse ceiling systems are recent air distribution systems that supply cold air to the occupant area using perforated diffuse panels. These systems distribute air with a low velocity, minimizing the draft risk and dissatisfaction in highly dense spaces. The transmission risk of airborne infectious diseases like Covid-19 from the infected patient is high in waiting rooms. Thus, there is a demand to assure a secure environment for medical staff and patients in the waiting rooms. This study aims to numerically investigate the impact of the relative distance of the contamination source and exhaust on the transmission of airborne infectious diseases in the waiting room equipped with the diffuse ceiling ventilation system. In this regard, the release of Covid-19 from 4 different patients was investigated separately using the computational fluid dynamics technique. The distribution of the airborne infectious diseases is simulated by releasing SF6 tracer gas. The simulation result revealed that the contaminated patient located adjacent to the room’s outlet had no contamination risk for other patients and staff in the waiting room.
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| 7. |
- Sadeghian, Parastoo
(författare)
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Computational fluid dynamics application in indoor air quality and health
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Indoor air quality directly affects the comfort, performance, and well-being of occupants. Indoor pollution can cause immediate or long-term health effects and has been responsible for 4.1% of global deaths in recent decades. In operating rooms, providing a high indoor air quality is especially critical as surgical site infection can occur in patients due to air contamination in operating rooms.Surgical site infections due to antibiotic resistant bacteria may threaten the safety and lives of millions of people each year. To moderate and reduce indoor contamination, it is necessary to select a proper ventilation strategy.Improving ventilation system performance requires a deep understanding of airflow patterns and contamination distribution.This thesis adopted computational fluid dynamics to evaluate airflow patterns and the spread of airborne contaminations in indoor environments. Moreover, we sought to provide an approach to facilitate transferring the obtained knowledge to medical experts and decisionmakers to reduce the infection risk after the surgery.The use of warming blankets has raised the concern about surgical site infections. Warming blankets are used to prevent hypothermia in patients during surgery. However, our results showed that these warming blankets reduce the bacteria-carrying particles level at the wound due to warm upward airflows.Surgical lamps can block the airflow and generate a low-velocity area under the lamp that increases the accumulation of contaminants. The simulation results revealed that a novel fan-mounted surgical lamp reduced the contamination level to an acceptable range for infection-prone surgeries. This novel surgical lamp successfully reduced contamination in the operating room supplied with both turbulent mixing and laminar airflow ventilations.In another study, we implemented a protective curtain and showed that this strategy could significantly reduce the exposure level of the medical team to a patient with infectious respiratory disease. This novel protective curtain is located between the patient’s upper body and the lower part during surgery. We found a 57% reduction in bacteria-carrying particle concentration at the wound by adopting this curtain. Thus, using this protective curtain can reduce the exposure level of both patient and surgical team in the operating room.Besides investigating the performance of ventilation systems in hospitals, we investigated the application of diffuse ceilings ventilations in clinics, especially waiting rooms. Diffuse ceiling ventilation systems are common air distribution systems in offices and schools. Based on simulation results, a diffuse ceiling with a central opening and evenly distributed heat loads resulted in the highest cooling capacity and thermal comfort in clinic waiting rooms.We have visualised the airflow field and airborne particles in operating rooms with the help of virtual reality techniques. We found the virtual reality environment more engaging to understand the airflow field and particle movements in operating rooms.
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| 8. |
- Sadeghian, Parastoo, et al.
(författare)
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Does a fixed temperature-controlled airflow ventilation system reduce airborne infectious disease in clinics? A numerical investigation
- 2021
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Konferensbidrag (refereegranskat)abstract
- HVAC systems play an important role in moderating and controlling both surgical site infections and airborne infectious disease transmission in hospitals and clinics. Designing a proper HVAC system can minimize the airborne particles' concentration and prevent the spread of contaminated agents to the wound area, instruments and implants, and the medical team. Various ventilation system strategies have been developed to reduce the airborne particles in the air during the surgeries. The turbulent mixing, laminar airflow, and temperature-controlled airflowventilations are three common operating room ventilation systems used in rooms where major surgeries are conducted. However, mobile ventilation systems are mostly applied for minor surgeries and dental treatments that mainly supply a mixing airflow with random directions.Several studies revealed that instead using a mobile laminar airflow ventilation system successfully reduced the contamination level; however, the washing effect of such systems is limited to distance and location. In this regard, this research investigates the impact of using a novel fixed ventilation system based on the principle of temperature-controlled airflow on the reduction of both the SSI and cross-contamination risks in patients and medical teams during minor surgeries. The airflow behavior and airborne particle distribution are simulated by using computational fluid dynamics (CFD) techniques.
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| 9. |
- Sadeghian, Parastoo, et al.
(författare)
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Evaluating the cooling capacity of diffuse ceiling ventilation systems for different ratios of perforated area
- 2020
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Konferensbidrag (refereegranskat)abstract
- Diffuse ceiling ventilation system is an air distribution system, in which the outdoor air is supplied to the occupied room through the perforated panels installed in the ceiling. This method has been proven to have a higher cooling capacity compared to the conventional air distribution systems. This study is a part of an ongoing project consists of two phases. In the first phase, the project aimed to experimentally investigate the dependence of the cooling capacity on the location of heat sources in the room and the distribution of diffusive supply areas in the ceiling. The experimental study was carried out in order to calibrate the model of the test room with the perforated panels cover the entire ceiling. The second phase of the project numerically studied the cooling capacity of the system in several scenarios with different ratios of perforated to non-perforated panels in the ceiling, with even distribution of the heat sources. The obtained results showed that decreasing the area of the perforated panels can improve the cooling capacity of the diffuse ceiling system.
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| 10. |
- Sadeghian, Parastoo, et al.
(författare)
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Impact of design parameters of diffuse ceiling ventilation systems on indoor air quality in school classrooms : a numerical assessment
- 2022
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Ingår i: E3S Web of Conferences. - : EDP Sciences. - 2267-1242.
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Konferensbidrag (refereegranskat)abstract
- Indoor air quality directly impacts an individual’s productivity and health condition in office buildings, hospitals, schools, and residential buildings. Diffuse ceiling systems have been used widely in classrooms at schools that have high heat loads. In this regard, this study investigated the role of diffuse ceiling design parameters, including active diffuse panels’ configuration and contamination locations, on indoor air quality in a classroom. The spread of airborne infectious diseases was simulated using computational fluid dynamics techniques. The results revealed that the central configuration of diffuse ceiling panels had the minimum spread of contaminations in the classroom compared to the dispersed configuration.
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