Zone Ventilation Research Articles

Evaluation of ventilation and indoor air quality inside bedrooms of an elderly care centre

Ventilation and indoor air quality are important factors that affect the health of the elderly. The purpose of this study was to find effective ventilation design measures for improving ventilation and air quality in typical two-bed bedrooms in elderly care centres (ECCs). Mixing ventilation (MV), displacement ventilation (DV), zone ventilation (ZV) and stratum ventilation (SV) were analysed with twelve scenarios to find the most effective ventilation design solutions including six scenarios with curtains between the beds and six scenarios without curtains between the beds. Airflow distribution, CO2 concentration, ventilation efficiency and health risk assessment were adopted for discussion. SV was found to be an effective method for improving air quality in the ECC bedroom while also taking into account the needs and rights of elderly residents, such as privacy. Comparing scenarios with and without curtains between beds under same types of ventilation, scenarios without curtains showed a slight (≤8%) decrease in CO2 concentration in the pillow area. However, this could increase virus transmission risk and compromise elderly privacy, so it is not recommended. Regarding the scenarios with curtains between the beds, the contaminant removal efficiency (CRE) of scenarios using SV was increased by 2.58, 3.22 and 2.12 times compared to the scenarios using MV, DV, and ZV respectively. Additionally, the health ratio (HR) of SV was reduced by 46.3 %, 53.7 %, and 41.7 %. Hence, it is recommended to install curtains between the beds and apply SV in ECC bedrooms. This study can be used as a guide for systematically designing ventilation systems in ECC bedrooms. Furthermore, collaboration among environmental engineers, designers, policymakers, and the wider community is essential to develop sustainable indoor environments for the elderly.

The effects of desk-partition layout on cough droplet dynamics relating to seasonal influenza

The use of physical dividers as control measures for short-range viral transmission in indoor settings has gained increasing attention. However, the understanding regarding their correct usage under different seating arrangements is incomplete. In this study, we focused on assessing the effectiveness of physical dividers in impeding the transient transmission of cough droplets in three representative layouts using the large-eddy simulation technique with the Eulerian–Lagrangian model. We computationally also investigated the effects of ventilation on viral droplet transmission under three representative desk-divider layouts. The ventilation approach was tested using two different ventilation rates (1.0 and 1.8 m/s). A comparative analysis of the ventilation flow fields, topologies, and particle directions has been studied. The findings indicate that the sitting arrangements, ventilation rates, and partition layouts play a significant role in designing effective control measures for indoor infection under the office setup considered. The protected occupied zone ventilation (POV) worked best in situations of low ventilation (1.0 m/s) for cross-partition in protecting the three healthy persons. In addition, the POV performed well for low (1.0 m/s) and high (1.8 m/s) ventilation rates for face-to-face layout. The side-by-side configuration performed poorly for the POV considered in protecting the healthy person seated directly opposite the infected person. The numerical predictions may be used to validate other experimental studies and educate office workers and engineers on indoor airborne infection control.

Model simplification of geometry and facilities, for energy and indoor environment towards more reliable energy labelling

Reliable building energy and indoor climate performance assessment require adequate and often time-consuming modelling. Currently, energy performance certification (EPC) is carried out in Member States (MS) using simple steady-state tools. These tools simplify not only building geometry but also HVAC systems, boundary conditions, and building loads. These simplifications can cause the so-called “performance gap”, which is the difference between modelled prediction and actual operation. This creates a lack of trust in the EPCs and scepticism. This paper is scouting toward shifting to dynamic models of different detail levels, considering the zoning, heating and ventilation facilitie’s complexity. In the scope of this dynamic thermal simulation study, a residential multi-apartment building located in Denmark is investigated. The thermal zone simplification has 5 levels of complexity, from modelling each room as a thermal zone to the whole staircase as one thermal zone. The heating system was modelled as: i) ideal loads, ii) electrical radiators, iii) water radiators. Ventilation was modelled as i) zone ventilation, and ii) airflow network. Modelling results are evaluated for heat demand, thermal and atmospheric comfort.

Energyplus model of double skin façade and diffuse ceiling ventilation

This paper introduces an Energyplus model to combine the double skin façade and diffuse ceiling ventilation systems with weather-adjusted dynamic control for both heating and cooling purposes. The proposed Energyplus model is validated with measurement data for both the heating mode and cooling mode. The double skin façade, diffuse ceiling, and the room are modeled as different thermal zones in Energyplus. The ventilation between the adjacent zones is controlled by zone ventilation and zone mixing. The cooling mode of the double skin façade is modeled by wind and stack. An energy management system (EMS) controls the ventilation modes based on outdoor conditions and indoor air temperature. The geometry of the model is identical to the experiment room in the façade lab facing south, with the same internal load and ventilation mode. The model results are then compared to the experimental data, including both heating mode and cooling mode for 4 thermal zones: The DSF zone, the DSF top zone, the diffuse ceiling zone, and the room zone. For heating mode, the average discrepancy of all 4 thermal zones between the model results and experimental data is 13,75%, while for cooling mode, the average discrepancy is 13.78%. The model performance of the room zone is the highest, which has a discrepancy of 5.31% for the heating mode and 3.67% for the cooling mode compared to the experimental data.

Dispersion of expectorated cough droplets with seasonal influenza in an office

We do not fully grasp viral droplet transmission processes in ventilated interior environments. The core focus of our research is to investigate the effectiveness of the protected occupied zone ventilation (POV) through computational fluid dynamics models in a simplified office setting. The large-eddy simulation technique with the Eulerian–Lagrangian model was implemented to address complicated indoor processes such as turbulence, flow–aerosol interaction, and ventilation impact. We computationally investigated the effects of desk partitions and the POV on cough droplets in an office. The ventilation approach was tested using two distinct exhaust layouts and four different ventilation rates (1.0, 1.2, 1.5, and 1.8 m/s). A comparative analysis of the ventilation flow fields, topologies, and particle directions has been studied. The findings indicate that the plane jet's ventilation rates influence the protected occupied zone ventilation performance. The ventilation rates distributed the virus droplets around the room, but compared to the up-exhaust cases, the down-exhaust cases appeared to have better shielded the healthy person. This pattern could indicate that the placement of the exhaust outlet in ventilation systems significantly influences indoor aerosol dispersion. The results also show that substantial flow streams may carry tiny particles (≤70 μm) throughout their path. Large particles (≥100 μm) could not go far in cough gas clouds. Most viral particles deposit on solid surfaces in various work sites per specific ventilation rates. Office workers need to be very cautious around these hazardous areas.

Zonal modeling of air distribution impact on the long-range airborne transmission risk of SARS-CoV-2

A widely used analytical model to quantitatively assess airborne infection risk is the Wells-Riley model which is limited to complete air mixing in a single zone. However, this assumption tends not to be feasible (or reality) for many situations. This study aimed to extend the Wells-Riley model so that the infection risk can be calculated in spaces where complete mixing is not present. Some more advanced ventilation concepts create either two horizontally divided air zones in spaces as displacement ventilation or the space may be divided into two vertical zones by downward plane jet as in protective-zone ventilation systems. This is done by evaluating the time-dependent distribution of infectious quanta in each zone and by solving the coupled system of differential equations based on the zonal quanta concentrations. This model introduces a novel approach by estimating the interzonal mixing factor based on previous experimental data for three types of ventilation systems: incomplete mixing ventilation, displacement ventilation, and protective zone ventilation. The modeling approach is applied to a room with one infected and one susceptible person present. The results show that using the Wells-Riley model based on the assumption of completely air mixing may considerably overestimate or underestimate the long-range airborne infection risk in rooms where air distribution is different than complete mixing, such as displacement ventilation, protected zone ventilation, warm air supplied from the ceiling, etc. Therefore, in spaces with non-uniform air distribution, a zonal modeling approach should be preferred in analytical models compared to the conventional single-zone Wells-Riley models when assessing long-range airborne transmission risk of infectious respiratory diseases.

Pacific Equatorial Undercurrent: Mean state, sources, and future changes across models

The Equatorial Undercurrent (EUC) stretches across the Pacific, transporting cool waters rich in oxygen and nutrients eastward to one of the most productive regions in the ocean. As an intricate part of the global climate system, EUC dynamics are essential to understanding future climate change but are poorly represented in global coupled climate models. This study examines EUC representation and future changes in the latest generations of the Coupled Model Intercomparison Project (CMIP6 and CMIP5) and an eddy-permitting ocean model. We also examine historical and projected changes in EUC source waters, including the Mindanao Current (MC), New Guinea Coastal Undercurrent (NGCU), and interior thermocline convergence. The circulation features in the models are broadly consistent with observations and ocean reanalyses, but improvements from CMIP5 to CMIP6 are limited. In the future projections, the EUC is enhanced in the western Pacific, with less prominent changes in CMIP6, but more so in the eddy-permitting model. The western Pacific EUC enhancement is likely associated with a wind-driven redirection of waters south of the equator, in which the NGCU boundary flow increases while the interior thermocline convergence decreases. This is superimposed on an overall weakening of the North Pacific subtropical overturning cell, including the MC, interior thermocline convergence, and Ekman divergence. As EUC heat and nutrient composition is linked to its sources, these projected changes have implications for the EUC's role in air–sea feedbacks, nutrient replenishment, and oxygen minimum zone ventilation in the eastern Pacific.

Ventilation Strategies for Mitigation of Infection Disease Transmission in an Indoor Environment: A Case Study in Office

During the normalization phase of the COVID-19 epidemic, society has gradually reverted to using building space, especially for public buildings, e.g., offices. Prevention of airborne pollutants has emerged as a major challenge. Ventilation strategies can contribute to mitigating the spread of airborne disease in an indoor environment, including increasing supply air rate, modifying ventilation mode, etc. The larger ventilation rate can inevitably lead to high energy consumption, which may be also ineffective in reducing infection risk. As a critical factor affecting the spread of viral contaminant, the potential of ventilation modes for control of COVID-19 should be explored. This study compared several ventilation strategies in the office, including mixing ventilation (MV), zone ventilation (ZV), stratum ventilation (SV) and displacement ventilation (DV), through analyzing ventilation performance and infection risk for the optimal one. By using ANSYS Fluent, the distributions of airflow and pollutant were simulated under various ventilation modes and infected occupants. The SV showed greater performance in mitigating infection disease spread than MV, ZV and DV, with an air distribution performance index (ADPI) of 90.5% and minimum infection risk of 13%. This work can provide a reference for development of ventilation strategies in public space oriented the prevention of COVID-19.

Ventilation and Low-cost Strategies on Mitigating COVID-19 Infection Disease Transmission in Indoor Environment

During the normalization phase of COVID-19 epidemic, it is gradually reverted to use building space, especially for office. Prevention of airborne pollutant has emerged as a major challenge. Ventilation strategies can mitigate the spread of airborne disease in indoor environment, such as increasing ventilation rate, modifying ventilation mode, etc. The larger ventilation rate can lead to higher energy consumption may not effectively reduce infection risk. The potential of ventilation modes for COVID-19 control should be explored. Furthermore, it is necessary to adopt low-cost strategies, such as physical barrier, to increase the prevention efficiency while combining the ventilation system. This study was to investigate the impact of physical barrier on the spread of particles and infection risk in an office with a sufficient ventilation rate, and then compare different ventilation strategies, including mixing ventilation (MV), zone ventilation (ZV), stratum ventilation (SV) and displacement ventilation (DV), for the optimal one. The simulation model was mainly used in this work and validated by the experiment to show a good agreement with the model prediction. The results showed that (1) the SV showed greater performance in mitigating infection disease spread than MV, ZV and DV, with a minimum infection risk of 13%; (2) a barrier height of at least 60 cm above the desk surface is needed to effectively prevent the transmission of viruses with the risk of infection reduced by about 72%. This work can provide a reference for development of ventilation strategies as well as low-cost prevention interventions in public space oriented the prevention of COVID-19.

Performance Simulation and Analysis of Occupancy-Based Control for Office Buildings with Variable-Air-Volume Systems

Variable-air-volume (VAV) systems are used in many office buildings. The minimum airflow rate setting of VAV terminal boxes has a significant impact on both energy consumption and indoor air quality. Conventional controls usually have the terminal’s minimum airflow rate at a constant (e.g., 30% or more of the terminal design airflow rate), irrespective of the occupancy status, which may cause problems, such as excessive simultaneous heating and cooling, under ventilation, and thermal comfort issues. This paper examines the potential of energy savings from occupancy-based controls (OBCs). The sensed occupancy information, either occupant presence or people count, is used to determine the airflow rate of terminal boxes, the thermostat setpoints, and the lighting control. Using EnergyPlus, a whole-building energy modeling software, the energy savings of OBC strategies are evaluated for representative existing medium office buildings in the U.S. The simulation results show that the conventional OBC, based on occupant presence sensing, can save 8% of whole-building energy use in Miami (hot climate) for systems without air-side economizer and about 13% in both Baltimore (mixed climate) and Chicago (cold climate). Comparatively, the advanced OBC, based on people counting, can save 8% in Miami to 23% in Baltimore for systems with economizers. The outdoor-air fraction of the supply air from air-handling units significantly affects the potential energy savings from the advanced OBC strategy. In addition to energy savings, the advanced OBC satisfies the zone ventilation during all occupied hours over the whole year.

CFD study of the air distribution and occupant draught sensation in a patient ward equipped with protected zone ventilation

Effective ventilation in general hospital wards is important for controlling the transmission of airborne infectious agents that may cause respiratory diseases. Recently, a new ventilation concept called protected occupied zone ventilation (POV) has been shown to have the ability to improve the quality of inhaled air compared to that of traditional ventilation strategies. This study numerically investigates the percentage of people dissatisfied due to draught close to the health-care worker (HCW) and patient in a single-bed isolation room equipped with POV. The CFD validation results showed that out of the three examined turbulence models, the SST k–ω models predicted the velocity and temperature profiles agreeably according to the experimental findings. The SST k–ω model was further used to visualize the airflow distribution in the patient ward and investigate the influence of the supply velocity and temperature on the draught risk. Supply velocities of 1.0, 1.5 and 2.0 m/s did not exceed the suggested comfort criterion of 20% even at lower supply temperatures. The draught risk at ankle level of the sitting patient exceeded the maximum allowed value at supply velocities of 2.5 and 3.0 m/s at both lower and higher supply temperatures.

Local climate zone ventilation and urban land surface temperatures: Towards a performance-based and wind-sensitive planning proposal in megacities

Performance-based planning (PBP) is designed to determine city planning standards based on local activity characteristics; however, there have been few practical applications of this method. This study applied PBP to assess the impact of urban building morphology on local climate surface temperatures under different wind conditions during 2017 in Shanghai, China using multi-source data, such as frontal area density (FAD), local climatic zone classification, land surface temperature (LST) data, and geographic information. The results showed that urban architectural patterns were one of the important drivers of climate change. High-density high-rise buildings can increase surface temperatures, which were evidenced in Local Climate Zone 4 (LCZ4), LCZ7, and LCZ8 in the city center. A correlation between building FAD and local climate surface temperature was 0.44 during the winter. Also, we found that although seasonal differences affected by wind direction were small, the same wind had different effects on the surface of urban buildings in different climate zones. These findings provide a reference for urban architecture planning and can help to develop urban heat island adaptation strategies based on local conditions.

Evaluation of airborne contaminant exposure in a single-bed isolation ward equipped with a protected occupied zone ventilation system

Effective ventilation in general hospital wards is important for controlling the transmission of airborne infectious agents that may cause respiratory diseases. This study investigates the potentia...

Analysis on ventilation pressure of fire area in longitudinal ventilation of underground tunnel

In order to solve the problem of ventilation pressure loss in the fire area under the fire condition, the wind pressure loss model of the fire area is established based on the thermodynamic equilibrium relation. The semi-empirical calculation formula is obtained by using the model experiment and CFD simulation. The validity of the formula is verified. The results show that the ventilation pressure loss in the fire zone is proportional to the convective heat release rate at the critical velocity, which is inversely proportional to the upstream ventilation velocity and the tunnel cross-sectional area. The proposed formula is consistent with the law of the tunnel fire test fitting formula that results are close, in contrast, the advantage lies in a clear theoretical basis and ventilation velocity values. The resistance of road tunnel ventilation system is calculated accurately and reliably, and then an effective emergency ventilation operation program is developed. It is necessary to consider the fire zone ventilation pressure loss. The proposed ventilation pressure loss formula can be used for design calculation after thorough verification.

Experimental study of the transverse diffusion of pollutants through a downward plane jet in a room

ABSTRACTRecently, a new type of ventilation method known as protected zone ventilation has been studied for application to the prevention of indoor contaminants transported from one zone to another. The use of a downward plane jet plays a key role in a protected zone ventilation system. The objective of this study is to examine the transmission of contaminants through a downward plane jet in a room with gaseous contaminants. Experimental measurements were carried out in a full-scale test room under isothermal conditions at Aalto University, Finland. The results showed that the measured concentration profiles may match the calculated profiles when the supplied air velocity is higher than 1.5 m/s, by which the downward plane jet may separate the room into two zones with different concentrations. The results of this study may be used to guide the design and optimisation of protected zone ventilation systems.

Effect of endobronchial valve therapy on pulmonary perfusion and ventilation distribution.

IntroductionEndoscopic lung volume reduction (ELVR) is an emerging therapy for emphysematous COPD. However, any resulting changes in lung perfusion and ventilation remain undetermined. Here, we report ELVR-mediated adaptations in lung perfusion and ventilation, as investigated by means of pulmonary scintigraphy.MethodsIn this observational study, we enrolled 26 patients (64.9±9.4 yrs, 57.7% male) with COPD heterogeneous emphysema undergoing ELVR with endobronchial valves (Zephyr, Pulmonx, Inc.). Mean baseline FEV1 and RV were 32.9% and 253.8% predicted, respectively. Lung scintigraphy was conducted prior to ELVR and eight weeks thereafter. Analyses of perfusion and ventilation shifts were performed and complemented by correlation analyses between paired zones.ResultsAfter ELVR, target zone perfusion showed a mean relative reduction of 43.32% (p<0.001), which was associated with a significant decrease in target zone ventilation (p<0.001). Perfusion of the contralateral untreated zone and of the contralateral total lung exhibited significant increases post-ELVR (p = 0.002 and p = 0.005, respectively); both correlated significantly with the corresponding target zone perfusion adaptations. Likewise, changes in target zone ventilation correlated significantly with ventilatory changes in the contralateral untreated zone and the total contralateral lung (Pearson’s r: −0.42, p = 0.04 and Pearson’s r: −0.42, p = 0.03, respectively). These effects were observed in case of clinical responsiveness to ELVR, as assessed by changes in the six-minute walk test distance.DiscussionELVR induces a relevant decrease in perfusion and ventilation of the treated zone with compensatory perfusional and ventilatory redistribution to the contralateral lung, primarily to the non-concordant, contralateral zone.

Protected zone ventilation and reduced personal exposure to airborne cross-infection.

The main objective of this study was to examine the performance of protected zone ventilation (PZV) and hybrid protected zone ventilation (HPZV) to reduce the direct exposure to exhaled air from others' breathing. Experimental measurements are carried out to test the performance of PZV in a full-scale office room with two breathing thermal manikins. The measurements were performed under three configurations, including two standing manikins at different distances: 0.35, 0.5, and 1.1m. When the supply air velocity is increased to 4m/s in the downward plane jet, the dimensionless concentration is 40% lower than for fully mixed ventilation, which can be considered as a measure of protection from the zoning condition. The measurement results showed that in both the PZV and the HPZV system it is possible to decrease the transmission of tracer gas from one manikin to the opposite manikin; therefore, it probably would reduce the risk of air borne cross-infection between two people at the same relative positions. The results suggest that PZV and HPZV may be used to reduce the exposure of people in a protected zone from indoor pollutants emitted in a source zone.

Modelling and experimental study of performance of the protected occupied zone ventilation

The main objective of this study is to develop theoretical models to predict the performance of a new type of air distribution method known as protected occupied zone ventilation (POV), and to validate the model by conducting experimental measurements. The goal is to find out experimentally the most effective and efficient way of airflow distribution to protect occupants from infection of epidemic respiratory disease. Experimental measurements were performed under three setup conditions, including exhaust at sidewall, exhaust above the protected occupied zone and with partitions in the middle of the room. Two models are developed in this study to predict the transient pollutant concentration in the protected zone and the polluted zone. The protection efficiency of POV is defined in this study as well, which varies from 8% to 50% depending on the exhaust location, supply air velocity and the usage of partitions. The calculated results by using the models agree with the measurement results with a slot Reynolds number of 667, 1000 and 1167. The POV can separate the protected zone from the polluted zone by up to 2800ppm. The capacity of a POV system to separate the room into two zones with different concentration levels of contaminant indicates that the POV may protect people from infection of epidemic respiratory disease via a cross-contaminant inside a room.

Relationship between past airway pathology and current lung function in preschool wheezers

The functional outcome in preschool severe wheezers with eosinophilic airway inflammation and increased reticular basement membrane (RBM) thickness is unknown. We investigated the relationship between airway pathology at age 2 yrs and lung function at age 4-6 yrs in previous severe wheezers. Severe wheezers previously investigated by endobronchial biopsy and healthy children aged 4-6 yrs were recruited. Lung clearance index (LCI), conducting zone ventilation inhomogeneity (S(cond)), acinar ventilation inhomogeneity by multiple-breath washout, plethysmographic-specific airway resistance and exhaled nitric oxide fraction (F(eNO)) were measured. Lung function was compared between wheezers and healthy controls, and in wheezers correlated with past RBM thickness and mucosal eosinophilia (EG2+ cells). 72 healthy controls and 28 previous severe wheezers were tested. Wheezers had significantly higher median LCI (6.8 versus 6.6; p=0.001) and S(cond) (0.046 versus 0.016; p<0.0005) than healthy controls. Past RBM thickness (r=0.474, p=0.047) and EG2+ cells (r=0.552, p=0.041) showed significant correlations with current F(eNO), but no correlations were seen between past RBM thickness and current lung function. RBM thickness and EG2+ cells at age 2 yrs show a significant positive association with F(eNO) at age 5 yrs. Although lung function was abnormal at age 5 yrs in severe wheezers, this did not correlate with past RBM thickness.

Analysis of New Type Air-conditioning for Loom Based on CFD Simulation and Theory of Statistics

Based on theory of statistics, main factors affecting effects of loom workshop’s large and small zone ventilation using the CFD simulation in this paper. Firstly, four factors and three levels of orthogonal experimental table is applied to CFD simulation, the order from major to minor of four factors is obtained, which can provide theoretical basis for design and operation. Then single-factor experiment method is applied to CFD simulation, certain factor changing can be obtained with best levels of other factors. Base on above recommend parameters, CFD software is applied to simulate relative humid and PMV on the loom. Lastly, comparison of simulation results and experiment is used to verify feasibility of simulation results.