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Human health is significantly impacted by the quality of the air in living areas. Numerous factors, such as the kind of particle, clean air delivery rate, room geometry, surface features, and thermal plume produced by people or other equipment, all have an impact on indoor particle movement. This work uses computational fluid dynamics to quantitatively examine the performance of a portable air purifier that is routinely used to improve the indoor air quality of a room. The volumetric flow rate, particle diameter, and placement of the air cleaner device were considered in the assessment of the particle transport characteristics. The temperature, velocity, and age of the air distribution in the room were computed in three-dimensional simulations, and the effectiveness of the air cleaning device (ACD) in eliminating contaminants was then investigated. Clean air delivery rate (CADR), collection efficiency, and particle concentration rate values were also computed for every case that was taken into consideration. It is found that CADR and collection efficiency values for larger particles are about 2–7% better than those for smaller particles. The collection efficiency of ACD with different operating conditions is in the range of 71% to 87%. Better collection performance parameters are observed with higher flow rates. [ABSTRACT FROM AUTHOR]

The ability of the chilled ceiling combined with mixing ventilation and personal ventilation system (CC/MVPV) to provide comfort and protect occupants from negative pollutants in an office room in Iraq City-Hilla climate (hot and dry climate) was studied considering the occupied density. A transient 3D computational fluid dynamics (CFD) model was used to evaluate the mean air life, temperature distribution, carbon dioxide concentration and thermal efficiency with the best flow rate of the proposed system and compared with the mixing ventilation and chilled ceiling (CCMV) by using AIRPAK software. Three tests were conducted for three different cooling load cases treated with (25, 50, and 80%) cooled ceiling with a total cooling load of (14.8, 29.6, 47.4) W/m² of floor area. The chilled ceiling surface temperature ranged between (23, 21.39, 19)°C and the mixing ventilation supply air temperature (19, 21, 23)°C at a constant supply air flow rate (46 L/s) with two PV air flow rate (5 l/s, 7.5 l/s), room air temperature (25°C). It was discovered that by using a (CC/MVPV) system with an air flow rate (7.5 L/sec), the air quality in the breathing area can be improved based on the values of air exchange efficiency (ηa) and air distribution performance index (ADPI), which are (72%, 89.9) respectively, the efficiency of air exchange (ηD) when the visiting person (the person standing) stays in the room for an one hour, one and half hour, two hours by (99%, 96%, 94%), so we notice the longer he stays, the less the air change for the passengers due to the low ventilation rate. [ABSTRACT FROM AUTHOR]

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]

Indoor environmental control has become primordial to minimize inhalation risk of pollutants through the implementation of next-generation ventilation systems. The performance of these ventilation strategies should be evaluated in terms of risk mitigation using a multi-indicator approach to support the realistic outcome of this evaluation. The present study has evaluated five main ventilation strategies (mixing, displacement, underfloor air, impinging jet and stratum ventilation) widely used in current society and four further cases based on occupant position with respect to supply flow. Their performance was assessed through computational fluid dynamics and two interacting virtual manikins with autonomous respiratory functions to calculate age of air, particle dispersion in a room, particles in the local breathing zone, maximum long-term exposure, deposition rate on human tissue and transfer probability. Results showed that well-mixed air in up-supply strategies increase age of air, particle dispersion in the room, transfer probability and deposition in the human body. Down- and mid-supply methods show high local age of air while improving the other indicators but create asymmetric flow in some cases. Overall, displacement ventilation was the optimal solution because it presented the lowest transfer probability although slightly increased age of air. Furthermore, deposited particles were mainly located in the nasal cavity, which might lower adverse health effects. • Large eddy simulation improves accuracy of indoor particle tracking. • Virtual manikins allow exact inhalation dosage through transfer probability. • Displacement ventilation mitigates particle deposition compared to other types. • Particle tract deposition locale affects human body metabolization. [ABSTRACT FROM AUTHOR]

The performance of a ventilation system affects air quality, thermal comfort, and energy consumption in indoor environments. To evaluate the performance of displacement ventilation under various room configurations, steady Reynolds Averaged Navier–Stokes (RANS) Computational Fluid Dynamics (CFD) simulations were used. The CFD model was validated using measurements of a full-scale test room. The age of air concept was used to evaluate the ventilation performance regarding indoor air quality. The PD index was used to control the case studies for draft risk. Twelve cases with different configurations were systematically studied and compared with the reference case. The configurations included plan aspect ratio, exhaust opening position, inlet position and geometry, and internal heat gains. The results showed that the overall ventilation performance of a room is less sensitive to room configurations compared with local ventilation performance around the occupants. However, almost in all cases, the occupants were exposed to better-than-average air quality in most cases. The results also indicated that when internal heat gains are small, displacement ventilation should be used with caution. Practical application: Any HVAC system design is based on assumptions made for ventilation performance. Comprehensive knowledge of the influential factors is critical for an efficient design. Regarding the architecture and interior design, the architects are also involved in the ventilation systems since they have an axial role in decision making for room configuration, including but not limited to room geometry, the position of inlet and outlet air terminals, and heat/pollutant sources. Consequently, the impact of room configuration on ventilation performance is of practical importance in the architecture, engineering, and construction industry. [ABSTRACT FROM AUTHOR]

Since air quality has a great influence on students' health and learning ability, enhancing air quality in classrooms is important. Currently, widely distributed ventilation systems operate by moving airflow horizontally from ventilation inlets and outlets on the ceiling. This method can reduce the average pollution in a space by diluting it through air exchange; however, it is limited regarding homogeneous cleanliness due to air stagnation at some locations. Therefore, in this study, a new ventilation system was devised to improve indoor air quality and spatial homogeneity by installing ventilation inlets on the ceiling and numerous outlets on the floor, creating a vertical airflow in the interior space; this system was then applied to a middle school classroom. Using the age of air as an index, air quality improvement between the existing and newly designed ventilation systems was compared. In the classroom with the existing ventilation system, the age of air was low in the area near the ventilation inlets, while air congestion areas were widely distributed and air age was high near the outlets. Conversely, in the vertical airflow classroom, the average age of air was approximately 15% lower than that with the existing ventilation system, and the deviation of air age for each position in the classroom space was also reduced, showing a uniform air age distribution. Therefore, the vertical airflow ventilation system proposed in this study can be an effective ventilation scheme for enhancing and homogenizing indoor air quality. [ABSTRACT FROM AUTHOR]

Since air quality has a great influence on students’ health and learning ability, enhancing air quality in classrooms is important. Currently, widely distributed ventilation systems operate by moving airflow horizontally from ventilation inlets and outlets on the ceiling. This method can reduce the average pollution in a space by diluting it through air exchange; however, it is limited regarding homogeneous cleanliness due to air stagnation at some locations. Therefore, in this study, a new ventilation system was devised to improve indoor air quality and spatial homogeneity by installing ventilation inlets on the ceiling and numerous outlets on the floor, creating a vertical airflow in the interior space; this system was then applied to a middle school classroom. Using the age of air as an index, air quality improvement between the existing and newly designed ventilation systems was compared. In the classroom with the existing ventilation system, the age of air was low in the area near the ventilation inlets, while air congestion areas were widely distributed and air age was high near the outlets. Conversely, in the vertical airflow classroom, the average age of air was approximately 15% lower than that with the existing ventilation system, and the deviation of air age for each position in the classroom space was also reduced, showing a uniform air age distribution. Therefore, the vertical airflow ventilation system proposed in this study can be an effective ventilation scheme for enhancing and homogenizing indoor air quality.

The side-curtain is popular in cattle buildings to regulate indoor climates and ventilation rates by adjusting the opening ratio. It normally had three different adjusting strategies relate to the position of rollers, i.e. central roller (S1), top roller (S2) and bottom roller (S3), which result in different opening behaviors to generate the same opening ratio but different opening positions in the side wall for a full-curtain house. Numerical simulations were conducted using computational fluid dynamics (CFD) to investigate the effects of the eight potential opening behaviors of side curtains on the indoor climates and airflow rates in winter for a typical naturally ventilated dairy house in China when the opening ratio were 8.5% and 17%. Airflow patterns, wind chilled temperature (WCT) and age of air were analyzed in the animal occupied zone (AOZ) by taking reference planes. Openings at the very bottom of side walls had more efficient ventilation due to the younger air age, more effective air disturbing, more uniformly distributed indicators in AOZ. However, it will result in a lower WCT in AOZ although a lower ventilation rate was observed in this case. Openings on the very top of side wall would generate a better thermal comfort in AOZ but with very poor air quality and nonuniformly distributed airflows in the dairy house. S1 was not recommended to the practical application due to the poor indoor climate and the higher cost of the mechanical structure. Based on the comprehensive evaluations of the analytic hierarchy process, the most satisfaction opening positions were at the bottom of the side curtains and the optimized adjusting strategy is S2. [ABSTRACT FROM AUTHOR]

The effect of temperature of the heating system elements is a parameter that could affect the airflow in terms of buoyancy and thermal comfort and that should be studied to ensure the quality of ventilation. This study aimed to assess the air change efficiency and thermal comfort with three thermal conditioning systems (radiators, underfloor heating and radiant ceiling) in winter conditions, varying its position in the interior space. This can be used by architects and engineers when planning the position of the heating systems or refurbishing a room. The experimental analysis was developed in the test chamber of the Laboratory of Ventilation of the University of Valladolid, serving as validation of multiple CFD simulations. The results show that, being the thermal comfort achieved, the mean air change efficiency varied only 2.40% among all cases, which makes this factor not significant. Even so, the trajectory of the airflow in the premise would be affected by the thermal action, due to the convective effect, presenting great differences according to the location of the thermal systems. Thus, the air trajectory could falter when it enters the room or rise towards the ceiling creating areas with lower temperature in its centre. [ABSTRACT FROM AUTHOR]

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]

In this paper, a CFD (computational fluid dynamics) numerical calculation was employed to examine whether the ventilation system of the self-designed smart broiler house meets the requirements of cooling and ventilation for the welfare in poultry breeding. The broiler chamber is powered by two negative pressure fans. The fans are designed with different frequencies for the ventilation system according to the specific air temperature in the broiler chamber. The simulation of ventilation in the empty chamber involved five working conditions in this research. The simulation of ventilation in the broiler chamber and the simulation of the age of air were carried out under three working conditions. According to the measured dimensions of the broiler chamber, a three-dimensional model of the broiler chamber was constructed, and then the model was simplified and meshed in ICEM CFD (integrated computer engineering and manufacturing code for computational fluid dynamics). Two models, i.e., the empty chamber mesh model and the chamber mesh model with block model, were imported in the Fluent software for calculation. In the experiment, 15 measurement points were selected to obtain the simulated and measured values of wind velocity. For the acquired data on wind velocity, the root mean square error (RMSE) was 19.1% and the maximum absolute error was 0.27 m/s, which verified the accuracy of the CFD model in simulating the ventilation system of the broiler chamber. The boundary conditions were further applied to the broiler chamber model to simulate the wind velocity and the age of air. The simulation results show that, when the temperature was between 32 and 34 °C, the average wind velocity on the plane of the corresponding broiler chamber (Y = 0.2 m) was higher than 0.8 m/s, which meets the requirement of comfortable breeding. At the lowest frequency of the fan, the oldest age of air was less than 150 s, which meets the basic requirement for broiler chamber design. An optimization idea is proposed for the age of air analysis under three working conditions to improve the structure of this smart broiler chamber.

Chilled beams provide sensible cooling to an occupied space by using chilled water flowing through modular beams mounted to a room ceiling. Previous studies show that active chilled beam systems can achieve larger sensible cooling than all-air systems. However, most studies have focused on active chilled beams and little information is available for performance of passive chilled beam (PCB) under varied ventilation conditions. The objective of the present study is to investigate ventilation and air conditioning performance of combined PCB and displacement ventilation systems. Using a validated and verified computational fluid dynamics (CFD) model, parametric analyses were performed to examine the ventilation and air conditioning performance depending on five major operating parameters: 1) ventilation strategy, 2) PCB cooling output, 3) supply air temperature, 4) supply diffuser type, and 5) internal heat source arrangement. The results show that thermal comfort and ventilation performance of a combined PCB-DV system notably vary with the PCB cooling output and supply air temperature. When the PCB cooling output increases from 33% to 53% of the total cooling load, air change effectiveness decreases from 1.6 to 1.2 and vertical temperature difference decreases from 4.0 °C to 1.5 °C in the breathing zone. However, spatial heat source distribution has a marginal effect on the air mixing and temperature distribution. The results suggest that a relatively high PCB cooling output (>50% of the total cooling) combined with a low supply air temperature ( e.g. , 17 °C) could disrupt thermal stratification of displacement ventilation and increase draft rate in the occupied zone. [ABSTRACT FROM AUTHOR]

This study employed two ventilation indexes: local mean age of air and air change rate per hour, to investigate wind-induced natural ventilation of 260 wards of a multi-storey hospital building in suburb of Guangzhou using computational fluid dynamics simulations. Using the surface-grid extrusion technique, high-quality hexahedral grid cells were generated for the coupled outdoor and indoor airflow field. Turbulence was solved by the renormalisation group k-ɛ model validated against experimental data with grid independence studies. Homogeneous tracer gas emission was adopted to predict room age of air. The air change rate of cross ventilation and single-sided ventilation can reach 30–160 h−1 and 0.5–7 h−1, respectively. Due to different locations of room openings on the balconies, natural ventilation of a room can be greatly better than its neighbouring room. The wind-induced cross ventilation highly depends on the distance from the room opening to the stagnation point and on the resulting pressure distribution on the target building surface. Furthermore, it is significantly influenced by the upstream buildings, the bent shape of the target building, and the prevailing wind directions. The coupled computational fluid dynamics methodologies with integrated ventilation indexes are useful for assessing the natural ventilation performance in other complex built environments. [ABSTRACT FROM AUTHOR]

Knowledge of temperature stratification in indoor environments is important for occupant thermal comfort and indoor air quality and for the design and evaluation of displacement ventilation systems. This paper presents a detailed and systematic evaluation of the performance of 3D steady Reynolds-Averaged Navier–Stokes (RANS) CFD simulations to predict the temperature stratification within a room with a heat source and two ventilation openings. The indoor air quality within the room is also investigated by assessing the distribution of the age of air. The evaluation is based on validation with full-scale measurements of air temperature. A sensitivity analysis is performed to investigate the impact of computational grid resolution, turbulence model, discretization schemes and iterative convergence on the predicted temperatures and age of air. The results show that steady RANS with the SST k-ω model can accurately predict the temperature stratification in this particular indoor environment. However, of the five commonly used turbulence models, only the SST k-ω model and the standard k- ω model succeed in reproducing the thermal plume structure and the associated thermal stratification, while the three k-ε models clearly fail in doing so. In addition, the iterative convergence criteria have a major impact on the predicted age of air, where it is shown that very stringent criteria in terms of scaled residuals are required to obtain accurate results. These required criteria are much more stringent than typical default settings. This paper is intended to contribute to improved accuracy and reliability of CFD simulations for displacement ventilation assessment. [ABSTRACT FROM AUTHOR]

Conventional designers typically count on thermal equilibrium and require ventilation rates of a space to design ventilation systems for the space. This design, however, may not provide a conformable and healthy micro-environment for each occupant due to the non-uniformity in airflow, temperature and ventilation effectiveness as well as potential conflicts in thermal comfort, indoor air quality (IAQ) and energy consumption. This study proposes two new design methods: the constraint method and the optimization method, by using advanced simulation techniques-computational fluid dynamics (CFD) based multi-objective genetic algorithm (MOGA). Using predicted mean vote (PMV), percentage dissatisfied of draft (PD) and age of air around occupants as the design goals, the simulations predict the performance curves for the three indices that can thus determine the optimal solutions. A simple 2D office and a 3D aircraft cabin were evaluated, as demonstrations, which reveal both methods have superior performance in system design. The optimization method provides more accurate results while the constraint method needs less computation efforts. [ABSTRACT FROM AUTHOR]

Natural ventilation in residential buildings has a great potential for conserving energy and improving the health of occupants. This paper first presents a design strategy for optimizing natural ventilation in high-rise residential buildings in Chongqing, China, a region with unfavorably low wind speed. Through the use of CFD modeling, building orientation and spacing were adjusted, wind paths were created into internal zones, and two windows were constructed in each bedroom. The optimized design reduced the age of air to less than 6 min in 90% of the rooms, as compared to an age of greater than 30 min in 50% of the rooms in a conventional design. Natural ventilation was found to be effective in the Chongqing area with the optimized design. This investigation also measured the local age of air and air change rate in a building with the optimized design using a tracer-gas method. The measurements confirmed the reliability of the CFD results. [ABSTRACT FROM AUTHOR]

Abstract: A ventilation system of sufficient performance is the basic condition for comfort and health risk free environment in enclosed aircraft cabin spaces. The airflow pattern and spreading of fresh air into the cabin space mainly depend on the type of the air distribution system and location of heat sources/sinks. The present study deals with the investigation of the dependency between the type of the air distribution system and indoor air quality in a cabin of a small transport aircraft. The mock-up interior geometry of a small aircraft cabin for nine passengers was adopted for the investigation. Three types of the air distribution system were investigated: a typical mixing ventilation system, a modified mixing ventilation system and an under-aisle displacement ventilation system. The quality of ventilation was assessed based on the local mean age of air using CFD software Star-CCM+. At first, the CFD model of a typical mixing ventilation was validated against the experimental data of airflow in the mock-up of the small aircraft cabin. The validated model was then used for the evaluation of the three distribution systems under cold, mild and hot ambient environment conditions from the point of their performance for several typical aircraft operational conditions. Results of the study show a strong dependence of the air distribution systems performance on the ambient conditions. The most stable air distribution was reached with the modified mixing air distribution system. Other types of ventilation systems failed to provide sufficient ventilation and cooling under hot ambient conditions. [Copyright &y& Elsevier]

Abstract: This paper reports the results of a parametric CFD study on idealized city models to investigate the potential of slope flow in ventilating a city located in a mountainous region when the background synoptic wind is absent. Examples of such a city include Tokyo in Japan, Los Angeles and Phoenix in the US, and Hong Kong. Two types of buoyancy-driven flow are considered, i.e., slope flow from the mountain slope (katabatic wind at night and anabatic wind in the daytime), and wall flow due to heated/cooled urban surfaces. The combined buoyancy-driven flow system can serve the purpose of dispersing the accumulated urban air pollutants when the background wind is weak or absent. The microscopic picture of ventilation performance within the urban structures was evaluated in terms of air change rate (ACH) and age of air. The simulation results reveal that the slope flow plays an important role in ventilating the urban area, especially in calm conditions. Katabatic flow at night is conducive to mitigating the nocturnal urban heat island. In the present parametric study, the mountain slope angle and mountain height are assumed to be constant, and the changing variables are heating/cooling intensity and building height. For a typical mountain of 500 m inclined at an angle of 20° to the horizontal level, the interactive structure is very much dependent on the ratio of heating/cooling intensity as well as building height. When the building is lower than 60 m, the slope wind dominates. When the building is as high as 100 m, the contribution from the urban wall flow cannot be ignored. It is found that katabatic wind can be very beneficial to the thermal environment as well as air quality at the pedestrian level. The air change rate for the pedestrian volume can be as high as 300 ACH. [Copyright &y& Elsevier]

Abstract: By means of computational fluid dynamic (CFD) simulations, this paper investigated how rural winds transport relatively clean air into high-rise urban areas to dilute airborne pollutants. Two ventilation concepts for indoor environments were applied: the age of air to quantify the time taken by rural young air to reach a given place after it enters an urban area and the air exchange efficiency to evaluate the efficiency of rural winds flushing the entire urban canopy layer. Several square building arrays with street aspect ratios (building height/street width, H/W) ranging from 1.5 to 5.3 and building area densities of 0.25 (medium) or 0.4 (compact) were considered as the approaching wind is parallel to the main street whose length varies from street scales to neighborhood scales (330–510 m to 1.03–1.65 km in full-scale). Results show that considerable young rural air enters windward entries but a major fraction of air is vertically driven out as flowing deeper into such high-rise building arrays. So air exchange efficiencies are less than 50% in street-scale arrays, and smaller in longer (neighborhood-scale) or narrower arrays. For the neighborhood-scale medium arrays, considering the power-law velocity profile in the upstream free flow, a taller array gains a larger inflow rate across its windward entry and experiences younger air and greater air exchange efficiency than a lower one. If all buildings are theoretically open-based in a neighborhood-scale compact array, air becomes much younger everywhere and the air exchange efficiency doubles. In arrays of buildings with different heights, the secondary streets in front of taller buildings get younger air due to the downward flows within them. Although further investigations are still required before providing a practical framework, this paper is one of the first attempts to find ways in improving the ventilation performance in high-rise cities like Hong Kong. [Copyright &y& Elsevier]

[Display omitted] • Experimental and CFD studies were performed to investigate a novel DIV system. • The developed CFD model accurately predicted air quality and airflow in DIV. • Stratified air distributions were created by DIV in both cooling and heating. • The thermal comfort in a room with DIV met ASHRAE requirements. • The novel DIV system effectively remedied limitation of traditional DV. Traditional displacement ventilation (DV) creates high indoor air quality in occupied zone in cooling season due to thermal plume created by heat sources which then effectively purge contaminants out of the breathing zone, but tend to be challenged when high cooling loads are present. In addition, traditional DV, when supplying heated air via its diffusers has low ventilation effectiveness in heating season. This study investigated a novel wall-mounted displacement induction ventilation (DIV) system in comparison to traditional DV system. The investigation used an environmental chamber to mimic a typical classroom and measured the distributions of air velocity, air temperature, and contaminant concentration for validating the subsequent computational fluid dynamics (CFD) model developed across an array of operational modes. Then the CFD model was employed to evaluate the performance of DIV system in terms of ventilation effectiveness, mean age of air and vertical temperature gradient as it relates to thermal comfort. Each DIV unit receives 100% outdoor (or primary) air to its plenum chamber. As the primary air pressurizes the chamber, it exits a series of nozzles, creating a low pressure which then induces room air across the integral hydronic coil. A room is typically supplied with multiple DIV units, which allows for individual control operation during both cooling and heating modes. Results showed that stratified air distribution was achieved in both cooling and heating modes with DIV system, which remedied the current limitation of traditional DV. [ABSTRACT FROM AUTHOR]

In this paper, a CFD (computational fluid dynamics) numerical calculation was employed to examine whether the ventilation system of the self-designed smart broiler house meets the requirements of cooling and ventilation for the welfare in poultry breeding. The broiler chamber is powered by two negative pressure fans. The fans are designed with different frequencies for the ventilation system according to the specific air temperature in the broiler chamber. The simulation of ventilation in the empty chamber involved five working conditions in this research. The simulation of ventilation in the broiler chamber and the simulation of the age of air were carried out under three working conditions. According to the measured dimensions of the broiler chamber, a three-dimensional model of the broiler chamber was constructed, and then the model was simplified and meshed in ICEM CFD (integrated computer engineering and manufacturing code for computational fluid dynamics). Two models, i.e., the empty chamber mesh model and the chamber mesh model with block model, were imported in the Fluent software for calculation. In the experiment, 15 measurement points were selected to obtain the simulated and measured values of wind velocity. For the acquired data on wind velocity, the root mean square error (RMSE) was 19.1% and the maximum absolute error was 0.27 m/s, which verified the accuracy of the CFD model in simulating the ventilation system of the broiler chamber. The boundary conditions were further applied to the broiler chamber model to simulate the wind velocity and the age of air. The simulation results show that, when the temperature was between 32 and 34 °C, the average wind velocity on the plane of the corresponding broiler chamber (Y = 0.2 m) was higher than 0.8 m/s, which meets the requirement of comfortable breeding. At the lowest frequency of the fan, the oldest age of air was less than 150 s, which meets the basic requirement for broiler chamber design. An optimization idea is proposed for the age of air analysis under three working conditions to improve the structure of this smart broiler chamber. [ABSTRACT FROM AUTHOR]