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Residential buildings in South Korea have equipped an energy recovery ventilation (ERV) system to improve energy efficiency as well as dilute indoor air pollution. While most studies have focused on the efficiency of energy exchange or the ventilation performance of the ERV itself, the ventilation performance can be improved by the proper location of inlet and outlet vents. For the present study, the ventilation performance of the inlet and outlet vents of the ERV was investigated by using CFD simulation. By varying the locations of inlet and outlet vents, the airflow distributions and the age of air were assessed. In addition, the air exchange effectiveness was analyzed by using the mean age of air quantitatively. As a result, a higher age of air was observed when inlet vents were moved to the center of the plan along the wall and an additional inlet or outlet vent was installed in the kitchen. In addition, the highest air exchange effectiveness was obtained when the inlet vents were located in the center of the plan along the wall. Considering the economic perspective, it is recommended to locate the inlet vents in the center to at least improve the ventilation performance. [ABSTRACT FROM AUTHOR]

Residential buildings in South Korea have equipped an energy recovery ventilation (ERV) system to improve energy efficiency as well as dilute indoor air pollution. While most studies have focused on the efficiency of energy exchange or the ventilation performance of the ERV itself, the ventilation performance can be improved by the proper location of inlet and outlet vents. For the present study, the ventilation performance of the inlet and outlet vents of the ERV was investigated by using CFD simulation. By varying the locations of inlet and outlet vents, the airflow distributions and the age of air were assessed. In addition, the air exchange effectiveness was analyzed by using the mean age of air quantitatively. As a result, a higher age of air was observed when inlet vents were moved to the center of the plan along the wall and an additional inlet or outlet vent was installed in the kitchen. In addition, the highest air exchange effectiveness was obtained when the inlet vents were located in the center of the plan along the wall. Considering the economic perspective, it is recommended to locate the inlet vents in the center to at least improve the ventilation performance.

A biosafety level (BSL) laboratory is a set of biocontainment preventative measures used to prevent and isolate hazardous biological agents or their accidental release in a laboratory. It is vital to provide a negative-pressurized environment for disease infection control. The experimental equipment layout may affect the personnel's exposure to infection. However, the equipment layout and exhaust air grilles were in a fixed position in this investigated BSL. Due to retrofitting, the layout arrangement of HEPA as supply air is investigated numerically. Computational Fluid Dynamics (CFD) simulation is conducted to analyze and determine a better design for contamination control. This study proposes three ventilation arrangements as an alternative design, including vertical arrangement, horizontal arrangement, and L-shaped ventilation arrangements (instead of the supply being arranged in a single line). In addition, the airflow distribution, concentration decay, air of age, ventilation, and removal effectiveness are all examined in the study. The numerical simulation results were verified by a field measurement test. The results revealed that the L-shaped ventilation arrangement for supply air diffusers would achieve better ventilation and removal efficiency. The local mean age of air was also identified as the most satisfactory ventilation performance measure, as it shows the level of contaminant control. It also indicated that ventilation could be improved by arranging the supply air layout with less expenditure through CFD-aided simulation in identifying strategies for best practices for the design stage to reduce the running cost at full operation. [ABSTRACT FROM AUTHOR]

Natural ventilation can contribute to a sustainable and healthy built environment, but the flow can be highly dependent on the ventilation configuration and the outdoor turbulent wind conditions. As a result, quantifying natural ventilation flow rates can be a challenging task. Wind tunnel experiments offer one approach for studying natural ventilation, but measurements are often restricted to a few points or planes in the building, and the data can have limitations due to the intrusive nature of measurement techniques or due to challenges with optical access. Large-eddy simulations (LES) can offer an effective alternative for analyzing natural ventilation flow, since they can provide a precise prediction of turbulent flow at any point in the computational domain and enable accurate estimates of different ventilation measures. The objective of this study is to use a validated LES set-up to investigate the effect of the opening size, opening location and wind direction on the ventilation flow through an isolated building. The effects are quantified in terms of time-averaged and instantaneous ventilation flow rates, age of air, and ventilation efficiency. The LES results indicate that, for this isolated building case, the effect of the wind direction is more pronounced than the effect of the size and position of the ventilation openings. Importantly, when ventilation is primarily driven by turbulent fluctuations, e.g. for the 90° wind direction, an accurate estimation of the ventilation rate requires knowledge of the instantaneous velocity field.

Natural ventilation is gaining popularity in response to an increasing demand for a sustainable and healthy built environment, but the design of a naturally ventilated building can be challenging due to the inherent variability in the operating conditions that determine the natural ventilation flow. Large-eddy simulations (LES) have significant potential as an analysis method for natural ventilation flow, since they can provide an accurate prediction of turbulent flow at any location in the computational domain. However, the simulations can be computationally expensive, and few validation and sensitivity studies with respect to simulation parameters such as grid resolution and boundary conditions have been reported. The objectives of this study are to validate LES of wind-driven cross-ventilation and to quantify the sensitivity of the solution to the grid resolution and the inflow boundary conditions. We perform LES for an isolated building with two openings, using three different grid resolutions and two different inflow conditions with varying turbulence intensities. Predictions of the ventilation rate are compared to a reference wind-tunnel experiment available from literature, and we also quantify the age of air and ventilation efficiency. For the cross-ventilation case modeled in this paper, the prediction of the mean ventilation flow rate is very robust, showing negligible sensitivity to the grid resolution or the inflow characteristics with the maximum error of 1.9 and 1.3% for each sensitivity study. However, a sufficiently fine grid resolution is required to obtain accurate predictions of the detailed flow pattern and the age of air as they show comparably larger errors of 10 and 20% in the grid sensitivity study, and the standard deviation of the instantaneous ventilation rate is affected by the turbulence in the inflow condition with showing 44% difference.

A biosafety level (BSL) laboratory is a set of biocontainment preventative measures used to prevent and isolate hazardous biological agents or their accidental release in a laboratory. It is vital to provide a negative-pressurized environment for disease infection control. The experimental equipment layout may affect the personnel’s exposure to infection. However, the equipment layout and exhaust air grilles were in a fixed position in this investigated BSL. Due to retrofitting, the layout arrangement of HEPA as supply air is investigated numerically. Computational Fluid Dynamics (CFD) simulation is conducted to analyze and determine a better design for contamination control. This study proposes three ventilation arrangements as an alternative design, including vertical arrangement, horizontal arrangement, and L-shaped ventilation arrangements (instead of the supply being arranged in a single line). In addition, the airflow distribution, concentration decay, air of age, ventilation, and removal effectiveness are all examined in the study. The numerical simulation results were verified by a field measurement test. The results revealed that the L-shaped ventilation arrangement for supply air diffusers would achieve better ventilation and removal efficiency. The local mean age of air was also identified as the most satisfactory ventilation performance measure, as it shows the level of contaminant control. It also indicated that ventilation could be improved by arranging the supply air layout with less expenditure through CFD-aided simulation in identifying strategies for best practices for the design stage to reduce the running cost at full operation.

In developed countries, presence at home varies between 60% and 90% of the day, sleeping supposes 30%. Therefore, it is essential to ensure good indoor air quality that enhances health and benefits rest and recovery. In this context, it is necessary to achieve a balance between energy efficiency and air distribution parameters; thus, the influence exerted by the furniture of a bedroom on the air exchange efficiency, in the breathing zone during sleep, is assessed in this study. Computational fluid dynamics techniques, experimentally validated by the tracer gas (SF6) concentration decay method, are used to analyze 52 case studies corresponding to the same space, but varying both the number and the arrangement of the furniture inside. It is concluded that, in order to achieve a significant improvement in the air exchange efficiency, the number of elements included in the bedroom is not relevant, but the position of them. The highest increase in the ventilation efficiency in breathing zone is observed when the furniture is located avoiding the airflow obstruction in the area near the inlet and creating an unfilled volume of air in the area close to the outlet. [ABSTRACT FROM AUTHOR]

People spend most of their time indoors; therefore, maintaining a good indoor air quality and meeting the requirements of comfort and energy efficiency are essential. One of the most widespread strategies to achieve this objective is improving ventilation efficiency; therefore, the main aim of this study was to show an optimization of the ventilation efficiency, in a specific room, considering 47 variations (case studies) in the furniture arrangement. For this purpose, a numerical analysis using computational fluid dynamics techniques, validated by the tracer gas decay technique, was used to assess the distribution of the age of air within the space. The concept of “age of air” was implemented in the computational fluid dynamics code through user-defined functions, using the steady-state method based on the resolution of a transport equation for an additional scalar. Variations up to 5.75% in the ventilation efficiency between the cases studied have been achieved. It is concluded that an improvement up to 1.65% can be obtained when the elements of the study are introduced in a way that facilitates the air movement towards the exhaust; therefore, improvement of the ventilation efficiency through specific furniture distributions is possible, although not significant, according to the outcomes. [ABSTRACT FROM AUTHOR]

Cross-ventilation using rooftop wind-catchers is very complex as it is influenced by a wide range of interrelated factors including aerodynamic characteristics of the wind catcher, approach-flow conditions and building geometry. Earlier studies on wind-driven cross-ventilation in buildings have shown the significant impact of the geometry and position of openings on the flow and ventilation performance. However, this has not yet been investigated for cross-ventilation using wind catchers. This paper, therefore, presents a detailed evaluation of the impact of the outlet openings on the ventilation performance of a single-zone isolated building with a wind catcher. The evaluation is based on three ventilation performance indicators: (i) induced airflow rate, (ii) age of air, and (iii) air change efficiency. High-resolution coupled 3D steady RANS CFD simulations of cross-ventilation are performed for different sizes and types of outlet openings. The CFD simulations are validated based on wind-tunnel measurements. The results show that using outlet openings very close to the wind catcher will not increase the induced airflow, while it leads to a considerable reduction in the indoor air quality. A combination of one-sided wind-catcher and window is superior, while the use of two-sided wind-catchers leads to the lowest indoor air quality and air change efficiency. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the implementation of the “mean age of air” (MAA) concept into the computational fluid dynamics (CFD) code Fluent through user-defined functions to assess ventilation efficiency inside forced-ventilation food plants. Two transient methods and a steady-state method based on the resolution of an additional scalar transport equation were implemented and compared with experimental and numerical data obtained by Bartak et al. [Bartak, M., Cermak, M., Clarke, J.A., Denev, J., Drkal, F., Lain, M., Macdonald, I.A., Majer, M., Stankov, P., 2001. Experimental and numerical study of local mean age of air. In: Proceedings of the 7th International Building Performance Simulation Association (IBPSA) Conference, Rio de Janeiro, Brazil; Bartak, M., Beausoleil-Morrison, I., Clarke, J.A., Denev, J., Drkal, F., Lain, M., Macdonald, I.A., Melikov, A., Popiolek, Z., Stankov, P., 2002. Integrating CFD and building simulation. Building and Environment, 37, 865–871] for a 45 m3 test room. As the steady-state method led to the best compromise between accuracy of results and computation time, this method was then used to characterize ventilation efficiency inside a pilot cheese ripening room and two modern sausage dryers of large height. In light of the results presented, local MAA is a better and a more sensitive parameter than mean air velocity for highlighting areas with inadequate ventilation, and thus for assessing ventilation efficiency in industrial food plants. [Copyright &y& Elsevier]