Air Change Research Articles

The Predicted Performance of Natural Ventilation Strategies in Islamic Boarding School Design in Magelang

The importance issue in providing comfortable indoor air quality conflicts with the use of energy for mechanical cooling in tropics region such as Indonesia. Natural ventilation is seen as a potential to provide comfort through the change of air within the inside and outside of the space. Natural ventilation becomes a strategy to achieve building resilience towards climate change because it requires no energy consumption. Therefore, this research aims to justify the design of natural ventilation of low-income Islamic Boarding School in Magelang using steady state simulation. The results indicated that among three ventilation strategies simulated in this study, it can be concluded that stack effect is predicted to produce higher air flow rate which results to comfortable predicted observation on adaptive comfort.

The underpinning factors affecting the classroom air quality, thermal comfort and ventilation in 30 classrooms of primary schools in London

The health and academic performance of children are significantly impacted by air quality in classrooms. However, there is a lack of understanding of the relationship between classroom air pollutants and contextual factors such as physical characteristics of the classroom, ventilation and occupancy. We monitored concentrations of particulate matter (PM), CO2 and thermal comfort (relative humidity and temperature) across five schools in London. Results were compared between occupied and unoccupied hours to assess the impact of occupants and their activities, different floor coverings and the locations of the classrooms. In-classroom CO2 concentrations varied between 500 and 1500 ppm during occupancy; average CO2 (955 ± 365 ppm) during occupancy was ∼150% higher than non-occupancy. Average PM10 (23 ± 15 μgm-3), PM2.5 (10 ± 4 μgm-3) and PM1 (6 ± 3 μg m-3) during the occupancy were 230, 125 and 120% higher than non-occupancy. Average RH (29 ± 6%) was below the 40–60% comfort range in all classrooms. Average temperature (24 ± 2 °C) was >23 °C in 60% of classrooms. Reduction in PM10 concentration (50%) by dual ventilation (mechanical + natural) was higher than for PM2.5 (40%) and PM1 (33%) compared with natural ventilation (door + window). PM10 was higher in classrooms with wooden (33 ± 19 μg m-3) and vinyl (25 ± 20 μgm-3) floors compared with carpet (17 ± 12 μgm-3). Air change rate (ACH) and CO2 did not vary appreciably between the different floor levels and types. PM2.5/PM10 was influenced by different occupancy periods; highest value (∼0.87) was during non-occupancy compared with occupancy (∼0.56). Classrooms located on the ground floor had PM2.5/PM10 > 0.5, indicating an outdoor PM2.5 ingress compared with those located on the first and third floors (<0.5). The large-volume (>300 m3) classroom showed ∼33% lower ACH compared with small-volume (100–200 m3). These findings provide guidance for taking appropriate measures to improve classroom air quality.

CFD modeling of room airflow effects on inactivation of aerosol SARS-CoV-2 by an upper-room ultraviolet germicidal irradiation (UVGI) system

Ultraviolet germicidal irradiation (UVGI) systems inactivate microorganisms indoors. Upper-room UVGI systems use wall- or ceiling-mounted fixtures to create an air disinfection zone above the occupied zone. The performance of upper-room UVGI systems varies with indoor airflow patterns induced by mechanical ventilation and thermal plumes from indoor heat sources. Little information is available on the effects of ventilation strategies on upper-room UVGI system performance for the control of viral aerosols in occupied spaces. This study simulated the effects of ventilation system characteristics in an office space on the ability of an upper-room UVGI system to inactivate viral aerosols with UV-C susceptibility representative of coronaviruses. UVGI reduced viral aerosol concentration by two orders of magnitude relative to the concentration without UVGI. Air change rates and air distribution strategy (mixing vs. displacement) had notable effects on the effectiveness of the UVGI system. For mixing ventilation, as the recirculation airflow rate increased from 0 to 5.3 h−1 for a room volume of 108 m3 with a fixed outdoor air change rate of 0.7 h−1, UVGI inactivation increased by 96.7%. Mixing ventilation with 100% outdoor air of 0.7 h−1 yielded airborne virus inactivation that was double that of displacement ventilation, due to enhanced air mixing.

Inter-room pollutant transmission routes in naturally ventilated street canyon buildings

Airborne transmission of pollutants is a significant concern in urban areas, especially since the recent pandemic. While previous studies have explored inter-room pollutant crossflow in highrise buildings and isolated scenarios, the ventilation characteristics within street canyon configurations have not received enough attention. Understanding ventilation characteristics in this layout will help limit the spread of pollutants along the street. This study investigates the wind-driven transmission characteristics of pollutants between the indoor rooms situated adjacent to a street canyon, subjected to perpendicular approach flow. Numerical simulations were performed using the 3D steady Reynolds-Averaged Navier-Stokes approach and validated against surface pressure measurements inside a wind tunnel. The impacts of seven building ventilation strategies were compared, each representing a window opening combination on the two buildings. Based on the set environmental conditions, the results indicate that the inter-room transmission is dependent on both the ventilation efficiency and the specific location of the room. Increasing the ventilation rate decreases the cross transmission between the rooms, while rooms at the centre of the canyon have an increased susceptibility of being contaminated. For instance, switching from cross to single-sided ventilation decreased the average air change rate from 42.3h-1 to 1.4h-1, coinciding with a rise in pollutant concentration by 114-fold and 12-fold at the canyon's centre and side, respectively. Rooms at the edge of the canyon were more contagious and could contaminate other rooms located further inside the street, albeit in small doses. Our findings present new insights within the domain of indoor-outdoor air interaction, shedding light on the interplay between room location and potential inter-unit pollutant transmission. In addition, the pressure measurement results from the wind tunnel experiment provide a valuable resource for other researchers aiming to validate numerical simulations for building engineering applications.

Ammonia and methane emissions from small herd cattle buildings in a cold climate

Ammonia (NH3) and methane (CH4) emission measurements that reflect local production conditions are required to track progress in national emission policies and verify emission factors. The findings can also be used to better understand key factors influencing emissions. This is especially important in Norway, which has long cold winters, and small cattle herds in mechanically ventilated buildings. However, until now, NH3 and CH4 emissions from Norwegian cattle buildings have not been reported in literature. Moreover, in other cold climates, NH3 and CH4 emissions are often taken from large dairy herds in naturally ventilated buildings, with less focus on suckler cows. The objectives were to assess indoor climate, report NH3 and CH4 emissions and examine the impact of climatic factors on NH3 and CH4 emissions in three small herd dairy and suckler cow buildings over three seasons. Three of the buildings had mechanical ventilation, while one was naturally ventilated. The suckler building had higher relative humidity (RH > 90 %) and NH3 concentrations (> 25 ppm) due to lower minimum air change rate (ACH = 1.2 h−1). The suckler building also had the highest NH3 emissions (2.04 g Livestock Unit (LU)−1 h−1) followed by the mechanically ventilated dairy building (1.92 g LU−1 h−1) with the highest ACH. These two buildings had the lowest stocking densities and floor areas. In contrast, the suckler building had the lowest CH4 emissions (6.8–10.7 g LU−1 h−1). Methane emissions from the dairy building with the supply-exhaust air mixing system (16.4–19.3 g LU−1 h−1) was higher than the other dairy buildings (11.7–13.8 g LU−1 h−1). Temperature influenced NH3 emissions however, the direction of association between temperature and NH3 emissions differed among buildings. Relationship between RH and NH3 emissions was positive, but the correlation coefficient (R2 = 0.67) was strongest in the building with the highest RH.

An industry case study using parametric modelling to facilitate Passive House design

A Passive House’s airtight, well-insulated building envelope can lower operating energy use but also increase the possibility of overheating during the summer. The Passive House Planning Package (PHPP) Excel modelling tool for Passive Houses treats the entire structure as a single thermal zone; this simplification may be in part to blame for the instrument’s poor capacity to forecast the risk of overheating. The current study offers new information on two subjects. First, we compare PHPP’s overheating evaluation method to that of the Chartered Institution of Building Services Engineers’ (CIBSE) ‘TM59’ standard, which involves conducting dynamic energy modelling at the room level. Our results support the idea that PHPP underestimates overheating. In the analysed case, glazing solar heat gain coefficient, and air change rate were some of the most crucial factors affecting compliance. Second, we highlight the usefulness of parametric design for compliance.

Yield shortfall of cereals in Ukraine caused by the change in air temperature and precipitation amount

Yield shortfall of cereals in Ukraine caused by the change in air temperature and precipitation amount

Ventilation strategies based on an aerodynamic analysis during a large-scale SARS-CoV-2 outbreak in an acute-care hospital.

This study aimed to investigate ventilation strategies to prevent nosocomial transmission of coronavirus disease 2019 (COVID-19). We conducted a retrospective epidemiological investigation of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in a teaching hospital (February-March 2021). The largest outbreak ward was studied, and measurements were taken to determine the pressure difference and air change per hour (ACH) of the rooms. Airflow dynamics were assessed using an oil droplet generator, indoor air quality sensor, and particle image velocimetry in the index patient's room, corridor, and opposite rooms, by varying the opening and closing of windows and doors. During the outbreak, 283 COVID-19 cases were identified. The SARS-CoV-2 spread occurred sequentially from the index room to the nearest room, especially the opposite. The aerodynamic study demonstrated that droplet-like particles in the index room diffused through the corridor and the opposite room through the opening door. The mean ACH of the rooms was 1.44; the air supply volume was 15.9% larger than the exhaust volume, forming a positive pressure. Closing the door prevented diffusion between adjacent rooms facing each other, and natural ventilation reduced the concentration of particles within the ward and minimised their spread to adjacent rooms. Spread of droplet-like particles between rooms could be attributed to the pressure difference between the rooms and corridor. To prevent spread of SARS-CoV-2 between rooms, increasing the ACH in the room by maximising ventilation and minimising the positive pressure through supply/exhaust control and closing the room door are essential.

Increasing water temperature of the largest freshwater lake on the Mediterranean islands as an indicator of global warming

Global warming has been monitored for many years. The increase in air temperature and changes in the distribution and frequency of high temperatures are recorded continually. Lakes are one of the important water resources for aquatic ecosystems and water supply, which are significantly affected by global warming. The increase in lake water temperature increases the evaporation from the free lake surface, lowering the lake level, and changes the water quality. In the last few decades, analysis of changes in lake water temperature has been increasing. In situ measurements of water temperature in Vrana Lake on Cres island (Croatia), the largest freshwater lake on the Mediterranean islands, were analysed over 43 years. The results showed that the mean annual lake surface water temperature (LSWT) increased by 0.47 °C decade-1 (p < 0.0001). The increase in the mean annual lake summer surface water temperature (July–September) was 0.44 °C decade-1 (p < 0.0001), and the maximum annual LSWT was 0.56 °C decade-1 (p < 0.0001). All these amounts are in accordance with the published data on the increase in water temperature in the investigated European lakes. The number of days with LSWT higher than 25 °C increased by almost 9 d decade-1. An increase in the minimum LSWT (0.17 °C decade-1) corresponding to isothermal conditions was also determined but was not statistically significant. The minimum mean monthly LSWT increased by 0.36 °C decade-1 (p < 0.0001). Because the increase in water temperature can negatively affect the lake's ecosystem, and become a threat to safe water supply; LSWT, thermal stratification and evaporation should be continuously monitored. The impacts of climate warming on the lake stratification and aquatic ecosystems need to be further investigated.

A newly designed BIPV system with enhanced passive cooling and ventilation

Nowadays, the application of renewable energies such as solar energy in the building sector has increased notably considering the adverse impacts of climate change on human life; hence many studies have focused on the application of photovoltaic panels in buildings. In the current study, a 3D computational fluid dynamics (CFD) model has been developed to evaluate the performance of a newly designed building-integrated photovoltaic (BIPV) system. Given the negative influence of overheating on the lifespan and performance of PV panels, their passive air cooling has been studied. Further, the potential of rooftop-mounted solar panels in passive ventilation of buildings by generating natural convective currents has been explored. The developed CFD model takes into consideration the effects of radiation, conduction, and buoyancy-driven natural convective currents generated by solar PV panels which are heated due to the exposure to solar radiation heat flux. The results suggest that applying a high surface emissivity for the part of the roof beneath the PV panels intensifies the natural convective currents which in turn provides better cooling for PV panels with higher cooling effects at higher solar heat fluxes. Up to a 34% increase in the convective mass flow rate and a 3 K decrease in the mean temperature of the panels were attained by modifying the emissivity of roof surface. Such a 3 K decrease in the operating temperature of the PV panels can enhance their efficiency and lifespan by about 1.56% and 21 %, respectively. Based on the operating conditions and system characteristics, the BIPV system yielded an air change rate (ACH) in the range of 3–13 which was considered to be highly prevalent in providing the required passive ventilation for a wide range of applications. It was also observed that the flow dynamics inside the building were affected by both the amount of solar heat load incident on the solar panels and the emissivity of the roof surface behind the panels.

ANALISIS PENGARUH PERUBAHAN IKLIM DAN KUALITAS GETAH KARET TERHADAP PENDAPATAN PETANI KARET

Climate change which includes increasing air and sea surface temperatures and changing precipitation patterns can harm the rubber plantation agricultural sector, by maintaining good rubber latex quality and optimizing rubber production, farmers can increase their income in the face of climate change that can affect agriculture, including rubber plantations. The purpose of this study was to determine the effect of climate change and the quality of rubber latex on the income of rubber farmers. The method used in this research is descriptive quantitative with analysis using Partial Least Square (PLS). This study uses primary data sources from questionnaires regarding climate change and the quality of rubber latex on the income of rubber farmers. This study set a target population of 500 rubber farmers with a sample of 83 rubber farmers. The results of the study prove that partial (1) Climate Change (X1) has a positive and significant effect on the income of Rubber Farmers' Income (Y) the P Values are 0.000 &lt;0.05 so that H1 is accepted; (2) Rubber latex quality (X2) has a positive and significant effect on rubber farmers' income (Y). P values of 0.000 &lt;0.05 H2 are accepted; (3) Climate Change and Rubber Sap Quality at (Y) Rubber Farmer Income 73.9%

Analysis Thermal Behavior of a Locally Heated Solar Chimney

This paper presents the thermal behavior of a partially heated solar chimney under hot-humid climate conditions. The solar chimney (SCH) is 2 m high and 0.8 m wide and consists of an absorber plate and a translucent plate. The SCH allows a cavity thickness variation from 0 to 0.28 m, an inclination angle variation from 0 to 90º, and allows varying the amount of energy absorbed by the absorber plate and translucent plate. These plates were heated by resistors, simulating a solar irradiance range of 225 to 900 W/m2 (absorber plate) and from 12.15 to 50 W/m2 (translucent plate). Twelve tests were conducted with different configurations varying the power supplied to both plates, the thickness of the absorber plate cavity, and the 90º inclination angle. The variables measured were temperature, air velocity at the inlet, and heat flow on the side walls and rear wall. As a result, a maximum air renewal of 51.43 ACH was obtained, equivalent to the air changes used in a paint booth. The results show that the partially heated solar chimney can be used as a passive ventilation system for air renewal.

Perancangan dan Analisis Aliran Udara Sistem Ducting Cloud Kitchen dengan Metode Computational Fluid Dynamics

Cloud Kitchen is a commercial kitchen that serves food for delivery or takeaway without dine-in customers. Because the cloud kitchen consists of many kitchens, good air circulation is needed. The total volume of the 15 kitchen units in the cloud kitchen is 249.8 m3, so to meet commercial kitchen standards that have a minimum Air Change per Hour (ACH) value of 30 ACH, an air change of 4410 m3/h with a ducting system is required. From the simulation results, the air velocity distribution in the ducting ranges from 0 m/s to 92.426 m/s, while the pressure distribution in the ducting ranges from -578.824 Pa to 11639.58 Pa, and the distribution of air temperature in the ducting ranges from 49.8°C to 65.167°C. The chosen exhaust fan is a CKE brand centrifugal fan with type CKE DGB-4.5#-NO and an exhaust capacity of 5712–10562 m3/h.

Evaluation of Actual Ventilation Rates and Efficiency in Research-Scale Pig Houses Based on Ventilation Configurations.

Accurate ventilation control is crucial for maintaining a healthy and productive environment in research-specialized pig facilities. This study aimed to evaluate actual ventilation rates and ventilation efficiency by investigating different inlet and exhaust configurations. The research was conducted in two pig rooms, namely pig room A and pig room B, in the absence of animals and workers to focus solely on evaluating the ventilation system's performance. Actual ventilation rates were measured using hood-type anemometers, and the local air change per hour was analyzed at various measurement points via tracer gas decay experiments. The results demonstrated that specific inlet and exhaust combinations, such as side inlet/chimney outlet and ceiling inlet/side outlet, exhibited higher ventilation rates. However, the measured ventilation rates were much lower than the manufacturer's specifications. The side exhaust fan closer to the pig activity space demonstrated better ventilation effectiveness for the animals than the chimney exhaust fan. Additionally, the ceiling inlet exhibited superior air distribution and uniformity. Lower ventilation rates and higher infiltration ratios resulted in reduced ventilation efficiency, with the difference between pig and worker activity spaces being pronounced. This study emphasizes the importance of selecting optimal inlet and exhaust configurations to achieve efficient ventilation and create a healthy environment for both pigs and workers.

Camera-based occupant behavior trajectory capture and on-site assessment of spatio-temporal transmission risk of airborne virus in a university office building

Aerosol transmission is a route of contagion. The engineering field predicts risk in indoor environment by simulating the airborne transmission of the virus. However, occupant behavior is one of the main causes for the gap between predicted and actual airborne virus transmission risk. To improve the accuracy of transmission risk assessment, this study presents a framework for real-time assessment of infection risk based on the behavioral trajectory of the occupants captured by cameras. The study focused on analyzing the impact of short-range exposure and long-range exposure of occupants on the infection risk through fine-grained trajectories. On-site measurements were conducted in a university office building to obtain the air change rates (ACH) and occupant contact time respectively. A numerical model for quantifying the exposure risk of the two contact routes was also developed. The results demonstrated that the individual movement is diverse. The infection risk varies with the occupied space, behavioral patterns, and exposure time. The main passages and seats in the room, corridor corners, and room doorways are areas of the high frequency of short-range contact. The fraction of long-range exposure is 57.2%, indicating long-range exposure is the dominant route for the limited scenarios and population in this study. The cumulative risk of infection was 0.021 for teachers; 0.029 for employees; and 0.045 for students, with assumptions of initial infection rates of 5%. It can provide real-time warning for occupants through on-site monitoring and contribute to the transmission control and source tracing of airborne viruses.

Adjustment strategy for supply air volume balance and algorithm for multi-room differential pressure gradient in an air conditioning purifier system

Air change times and differential pressure (DP) gradient are important indicators for measuring the cleanliness of a cleanroom. In the traditional dust-free room, the control requirements of supply air volume (Gs) and DP balance are usually achieved by adjusting fan frequency and angle of the constant air volume valve or variable air volume valve, which wastes remarkable amounts of time, money and cannot achieve accurate regulation. Therefore, based on the analysis of cleanroom model, a Gs balance adjusting strategy (SAVS) and DP adjustment algorithm (DPGA) were proposed. After the influence of a multi-room Gs adjustment sequence was analyzed, the SAVS was found to achieve Gs balance in a multi-room area. Based on constant Gs, a theoretical analysis of differential pressure air volume, and adjustments of the distribution of return air volume and exhaust air volume, the DPGA realized the stability of DP gradient in the multi-room area. In the experimental verification of the model, the relevant errors of total Gs, total fresh air volume, and total exhaust air volume of system were within [–143, 265] m3/h. Compared with the room Gs calculated by the algorithm, the Gs error was maintained within [–1.8%, 5.3%]. Compared with the room DP calculated by the algorithm, the DP error was maintained within [–1.9, 1.3] Pa. Using the SAVS and DPGA, the energy consumption of the cleanroom operation was reduced by 18.58%. The system scheme is provided for cleanroom cleanliness and pressure difference control, and the energy consumption of the system is reduced.

The buffering effect of a paper-based storage enclosure made from functional materials for preventive conservation

Storage enclosures made of paper-based materials are commonly used to store and classify archival documents for their hygrothermal buffering effect. However, there is little information about papermaking and quantitative studies on such an effect. Aiming to assess the feasibility of using the enclosure to buffer temperature and relative humidity fluctuations, without any detrimental effect on the collections, this paper reports four measurements and a feasibility assessment: thermophysical properties of the enclosure material, hygroscopic properties of the material, air change rate of the enclosure, buffering effect in a climate chamber and the assessment of safeguarding collections without causing any detrimental effect. The measurement results show that the enclosure can buffer macro-environmental fluctuations, which was considered sufficient to mitigate temperature and humidity fluctuations from the room environment and to secure a condition inside that is safe for the collections. The paper-based material determines the buffering capacity of the enclosure, and an appropriate air change rate ensures average temperature and relative humidity inside the enclosure at a controllable level and prevents off-gassing accumulation. This work provides assurance that using enclosures is an effective approach to collection storage and establishes a significant basis for further heat–air–moisture simulation and energy-saving optimisation study in the service operation.

COVID-19 STANDARD OPERATING PROCEDURE ADVANCEMENT FOR OFFICE BUILDING USING INDOOR ENVIRONMENTAL QUALITY ELEMENTS

COVID-19 guideline is expected to be part of the 'new norms' for workplace. However, regarding COVID-19 Standard Operating Procedure (SOP) issued by Ministry of Health Malaysia, there is inadequate concentration on Indoor Environmental Quality (IEQ) parameters even it has been proven in various research that COVID-19 transmission spread actively in indoor environment and green elements could mitigate the virus transmission. Therefore, this study aims to enhance existing COVID-19 SOP by discovering sustainable COVID-19 framework for office building. Sets of questionnaires is distributed among employees at Menara Majlis Bandaraya Johor Bahru, Malaysia and analysed using Frequency Analysis and Cross Tabulation Analysis. Overall, result shows that EQ7 Air Change Effectiveness is the most important IEQ parameters that can be selected to improve the current COVID-19 SOP. This study is significant for building manager in workplace to enhance their current SOP by adding green elements which is IEQ parameters to reduce COVID-19 spread in workplace.

Changes in air and liquid permeability properties of loess due to the effect of lead contamination

Heavy metals in landfill leachate are easily adsorbed by soil particles, causing serious threats to human health and surrounding environments. Mining and metallurgy activities are intensive in Northwest China, thereby enlarging threats. The aim of the present study is to enhance our knowledge about the linkage between the microstructural evolution of the loess soil induced by lead contamination and the macro air and liquid permeability properties. A series of air and liquid permeability tests on the uncontaminated and Pb-contaminated loess specimens were conducted. Their air and liquid permeability properties were evaluated on the basis of Darcy’s law and the soil–water retention curves, respectively. The microstructural evolution, when subjected to low and high Pb2+ concentrations, was assessed using scanning electron microscopy (SEM), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and zeta potential tests. The intrusion of Pb2+ decreases the absolute zeta potential ζ, which in turn leads to a more distinct agglomerated structure and higher intrinsic permeability. Moreover, the dedolomitization and associated cerussite (PbCO3) precipitation are deemed as the main cause of micropore clogging, whereas the corrosion of the cement between soil particles by H+ shows a good correspondence to an increase in the number of mesopores. With the concentration of Pb2+ increasing from 0 to 2,000 mg/kg, the proportion of micropores decreases from 37.9% to 15.1%, and the proportion of mesopores increases from 17.3% to 53.3%. In addition, the air entry value decreased from 19.5 to 12.8 kPa, indicating that the water retention behavior decreased. The findings highlight the impacts of lead contamination on the microstructure and macro permeability properties and give some design guideposts to heavy metal-contaminated site remediation.

Investigation of Microclimate Parameter Assurance in Schools with Natural Ventilation Systems

Slow population growth has limited the construction of new schools, leading to the renovation of existing buildings to achieve energy efficiency goals. While improvements are made to thermal insulation, heating and ventilation systems often remain outdated, presenting challenges in maintaining indoor air quality (IAQ) in schools, where children spend a significant amount of time in densely populated classrooms, and whose health is more affected by IAQ than that of adults. Therefore, this study assessed the possibilities to achieve IAQ requirements in schools ventilated by opening the windows by monitoring the carbon dioxide (CO2) concentration, temperature, and relative humidity (RH) fluctuation. The results of the study have shown that it is not feasible to achieve the defined IAQ parameters in classrooms through window opening alone. The measured CO2 concentration during lessons in many cases exceeded the limit value of 1000 ppm and did not decrease to ambient levels when the windows were opened during the break. Additionally, the internal air temperature dropped below the normative when lessons started, and RH was significantly below the recommended minimum value on all days. It was also found that the use of thermal energy decreases evenly because of inefficient air change leaving no direct economic leverage for the installation of efficient ventilation systems.