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.
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 °C when using a circular valve placed in the external wall below the window and 2.6 °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.
•Performance of two air terminal devices used for heating application was examined.•Various boundary conditions were applied.•Both air terminals could provide satisfactory thermal environment.
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.
•The study evaluated the cooling capacity of the diffuse ceiling ventilation system.•The impact of heat load distribution in the room was analyzed.•The impact of active diffuse panel distribution in the ceiling was analyzed.•The impact of relative location of heat load and active diffuse panel was analyzed.•The parametric study is based on numerical CFD analysis and full-scale experiments.
Thermal comfort conditions profoundly affect the occupants' health and productivity. A diffuse ceiling ventilation system is an air distribution system in which the air is supplied to the occupied ...zone with relatively a low velocity through the perforated panels installed in the ceiling. The current study evaluated the impact of diffuse ceiling design parameters, i.e. diffuse panel configurations and heat load distributions, on the thermal comfort condition of the occupants. In this regard, the computational fluid dynamics technique was used to evaluate thermal comfort conditions in a waiting room, meeting room and office. The central and dispersal configuration of active diffuse panels was considered. The PMV-PPD model was applied to evaluate the overall occupants' comfort, while the draft rate was considered to assess local thermal comfort. The model validation was performed by comparing the collected laboratory measurement data. Overall, the results indicated that the central active diffuse panel configuration had a better thermal comfort than the dispersed one. The evaluation of dispersed configuration in realist scenarios, including office and waiting room, had the highest dissatisfaction, with a PPD value of 9%. Local thermal comfort assessment revealed that dispersed configuration had the highest draft rate of 14% in the office.
Operating room (OR) ventilation plays an important role in mitigating the spread of bacteria-carrying particles (BCPs) and preventing the incidence of surgical site infections (SSIs). The use of ...surgical lamps in ORs is critical for patient safety and staff comfort. However, the surgical lamp serves as an obstruction in the ventilation airflow and also as a source of heat generation, which often creates a stagnant area under the lamp. Such a stagnant area is normally poorly ventilated, where a significant amount of BCPs can accumulate. As the lamp is usually positioned above the patient to illuminate the wound, the accumulation of airborne BCPs under the lamp leads to a high risk of infections and constitutes a threat to patient safety. Therefore, we proposed an innovative design of the surgical lamp, that is, the fan-mounted surgical lamp. The performance of this new design of lamp was compared with the conventional closed-shape lamp under two ventilation strategies: mixing and unidirectional airflow (UDF) ventilation. To account for different working conditions, both the horizontal and 45° orientations were applied to the lamps. We employed numerical simulations to predict the BCPs contamination in the proximity of the surgical site, as it is directly related to the risk of SSIs. The results showed that the fan-mounted lamp considerably reduced the level of contamination under both ventilation strategies. Results also suggested that the contamination level cannot be effectively reduced by only adjusting the orientation of the closed-shape lamp under unidirectional airflow ventilation.
•Performance of UDF and mixing ventilation system investigated in operating room .•Results of applying closed-shape and fan-mounted surgical lamps were compared .•Impact of surgical lamps' inclination on airflow and contamination level considered .•Reduction in contamination level using fan-mounted surgical lamp for both ventilations .
Several research studies have ranked indoor pollution among the top environmental risks to public health in recent years. Good indoor air quality is an essential component of a healthy indoor ...environment and significantly affects human health and well-being. Poor air quality in such environments may cause respiratory disease for millions of pupils around the globe and, in the current pandemic-dominated era, require ever more urgent actions to tackle the burden of its impacts.
The poor indoor quality in such environments could result from poor management, operation, maintenance, and cleaning. Pupils are a different segment of the population from adults in many ways, and they are more exposed to the poor indoor environment: They breathe in more air per unit weight and are more sensitive to heat/cold and moisture. Thus, their vulnerability is higher than adults, and poor conditions may affect proper development.
However, a healthy learning environment can reduce the absence rate, improves test scores, and enhances pupil/teacher learning/teaching productivity. In this article, we analyzed recent literature on indoor air quality and health in schools, with the primary focus on ventilation, thermal comfort, productivity, and exposure risk. This study conducts a comprehensive review to summarizes the existing knowledge to highlight the latest research and solutions and proposes a roadmap for the future school environment. In conclusion, we summarize the critical limitations of the existing studies, reveal insights for future research directions, and propose a roadmap for further improvements in school air quality. More parameters and specific data should be obtained from in-site measurements to get a more in-depth understanding at contaminant characteristics. Meanwhile, site-specific strategies for different school locations, such as proximity to transportation routes and industrial areas, should be developed to suit the characteristics of schools in different regions. The socio-economic consequences of health and performance effects on children in classrooms should be considered. There is a great need for more comprehensive studies with larger sample sizes to study on environmental health exposure, student performance, and indoor satisfaction. More complex mitigation measures should be evaluated by considering energy efficiency, IAQ and health effects.
•Most schools worldwide have basic natural ventilation systems; typically, inadequate for meeting the needs of pupils.•Exposure to various air pollutants in school buildings risks severe damage to pupils' health.•Pupils tend to feel comfortable in indoor climates that are cooler than environments where adults feel thermally neutral.•Studies show that reduced classroom air quality will cause a reduction in cognitive performance of pupils.•There is limited insight demonstrating detailed energy use profiles in school buildings.
Patient warming is an efficient approach to preventing hypothermia during surgeries. Hypothermia increases the risk of postoperative infections, bleeding, transfusion demand, prolonging postoperative ...recovery, drug metabolism duration and vasoconstriction. Although the use of warming blankets addresses the problem of a decrease in a patient's core body temperature, concern remains that the heat emitted by these warming blankets can disturb the supplied clean air by the ventilation system and thus increase the contamination level of airborne particles.
The main purpose of this study is to numerically investigate the impact of using warming blankets on the performance of two common ventilation systems - unidirectional flow and mixing ventilation - in an operating room. The effect of using forced-air and conductive warming blankets on the distribution of bacteria-carrying particles and airflow behaviour were simulated in the operating room. The results showed that applying the forced-air warming blanket considerably increased the average air temperature at the wound area and under the surgical drape. Thus, the forced-air warming blanket can be more effective than the conductive blankets in warming the patient during the surgery. However, using the contaminated forced-air warming blanket resulted in a considerable increase in the contamination concentration at the wound surface.
An increased focus on energy saving has led to a rapid development of energy-efficient buildings. In the residential buildings, space heating, ventilation and air conditioning (HVAC) have the highest ...energy use. The ventilation system is the main tool to provide acceptable indoor air quality and thermal comfort for occupants. This study presents an investigation of the thermal environment in a room served by new developed, combined ventilation and heating system. The focus is on different configurations of the supply air terminal device in the studied system. The main goal is to investigate the influence of different supply air parameters, which in this study are flowrate and temperature, on the airflow behaviour and performance of the mixing ventilation. In this regards, three different supply air conditions with two inlet configurations were considered. This work has been carried out numerically and validated with the laboratory measurements. Computational Fluid Dynamics (CFD) simulation was applied in this study to map the airflow patterns and air temperature distribution. The results showed that decreasing supply air temperature and increasing the flowrate provided a uniform temperature distribution for both inlet configurations. Inlet configuration investigated in case1 has lower vertical temperature differences in comparison with case 2.
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.
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.
Infektioner relaterade till kirurgiskt ingrepp utgör 38 % av rapporterade infektioner efter operation. Dessa infektioner ökar dödligheten och behandlingskostnaderna samt förlänger patienternas sjukhusvistelse. Bakteriebärande partiklar är den främsta orsaken till infektion vid kirurgi. Huvudkällan till dessa partiklar är hudfragment som frigörs från kirurgisk personal under en pågående operation. Genom att tillföra ren luft via ventilationssystemet kan koncentrationen av baktebärande partiklar i operationssalen minskas. Ventilationssystemets förmåga att ventilera salen påverkas av föremål som stör luftströmmen, som exempel medicinsk utrustning, kirurgiska lampor samt av närvarande personal och deras beteende under operationen. Med avancerade numeriska strömningsberäkningar undersöks i denna avhandling luftflöden och fördelningen av föroreningar i operationssalen under inverkan av sådana störningar. Tre olika ventilationssystem inkluderas. Ett för laminärt luftflöde, ett för turbulent omblandning och ett för temperaturreglerad luftströmning. I studien kartläggs ventilationssystemens funktion och relevansen prövas i ett kontinuerligt samarbete med tillverkande industri. Användning av värmefiltar förekommer under större operationer för att hålla patientens kroppstemperatur stabil. Det finns emellertid en stor oro för att dessa filtar stör det tillförda luftflödet och därmed ökar föroreningsnivån. En vanlig typ av värmefilt med forcerad varmluft kan om den är förorenad avsevärt öka koncentrationen av bakteriebärande partiklar i sårområdet. De flesta undersökningar om värmande filtar är kliniska studier och det är fortfarande inte helt klarlagt i vilken mån och hur dessa filtar skall användas. Denna studie visar emellertid att användning av värmefiltar inte påverkar föroreningsnivån i den kirurgiska zonen. Gjorda datorsimuleringar av luftflödesfältet och partikelspårning visar att det laminära ventilationsflödet lättare störs av lokala värmebelastningarna än av generella värmebelastningar i operationssalen. Kirurgiska lampor betraktas som hinder i en planerad luftflödesväg. Lampor kan skapa en stillastående luftmassa ovanför operationsbordet och därmed öka föroreningsnivån. För detta introduceras en ny design av kirurgisk lampa, en fläktmonterad kirurgisk lampa för operationsrum, utrustade med laminärt luftflöde och omblandning. Simulerade resultat visar att denna nya kirurgiska lampa signifikant minskar föroreningsnivån vid operationsbordet. Visualiseringsteknik användes i denna studie för att förbättra förståelsen hos kirurgisk personal om hur förorenade partiklar kan spridas i operationssalen. Med ett virtuellt och förstärkt gränssnitt visualiserades föroreningshalter i rumsluften då olika typer av ventilationssystem användes. Visualiseringen visar också hur kirurgigruppens storlek och arbetsställning under operation påverkar spridningen av föroreningar.
QC 20201103
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