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With the spread of sustainability concepts, due to the global energy crisis and the unrestrained consumption of natural resources, the importance of rational use and reduction of energy consumption has been intensified, albeit in short steps. This concern has taken up bioclimatic concepts in buildings, especially housing buildings for low-income people, aiming at improving the quality of housing production in terms of its habitability. The objective of this research is to theoretically and experimentally study the natural ventilation in a housing building, which fits into the low-cost pattern. The use of Computational Fluid Dynamics to predict natural ventilation was adopted as a tool to perform these analyses. Experiments were carried out by visiting the study area to collect data on air velocity, temperature, and relative humidity in all rooms of the residence in order to carry out the intended analyses. Computer simulation of natural ventilation considering the building with the doors and windows open and with fixed geometry was performed. Results proved that the proposed mathematical model was able to reproduce, with rich details and physical coherence, the internal and external air flow inside the building, indicating better internal ventilation performance in environments that have door and window openings, with recesses, revealing the importance of cross ventilation to reduce the internal temperature and consequent improvement in thermal comfort. The idea is to help civil engineers and specialists in the economically viable design of low-cost buildings from the economic, social, and thermal comfort points of view. [ABSTRACT FROM AUTHOR]

The airflow distribution characterised by different large- and small-scale eddies in the aircraft cabin is the most important factor to maintain passengers' thermal comfort and to remove contaminants. The airflow distributions in narrow-body aircraft cabins are based on the principle of mixing ventilation. Opposing jets from air diffusers can cause stream deflection and oscillation, which results in the asymmetry of large-scale instantaneous airflow structures. This dynamic airflow structure is very important for analysing time series parameters. Therefore, this study applied numerical simulation to examine the oscillation and asymmetry of instantaneous airflow field structures and phase space reconstruction and used spectrum analysis to evaluate the oscillation amplitude and period of dynamic airflow structure. We also studied the factors that influence the dynamic airflow structure, such as air supply speeds, air supply angles and the strength of the thermal plume. The results showed that as the air supply speed increased, the swing amplitude of the instantaneous airflow structure increased, while the period decreased. The air supply angle affected the jet attachment and collision angle, which in turn affected the swing amplitude and period. The thermal plume restrained the formation of large-scale swings and contributed to the appearance of small-scale structures. [ABSTRACT FROM AUTHOR]

The mining in seams with a high methane content by means of a longwall system, under conditions of high extraction concentration, results in exceeding methane concentrations allowed by the regulations at workings of the longwall environment, with the effect of mining machines' standstill periods. The paper is a part of a study supporting the development of a system for shearing cutting speed control at the longwall, which should substantially reduce the production standstills due to exceeded limits and switching off the supply of electric equipment. Such a control system may be appropriate for longwalls ventilated using "Y" and "short Y" methods. Efficient Computer simulations of the 3D airflow and methane propagation may assist the design and initial evaluation of the control system performance. First chapters present studies that are necessary for a proper formulation of the properties of the longwall model. Synthetic analysis of production during the period of longwall operation allowed one to choose the input assumptions to carry out ventilation-methane computations in a CFD numerical model of longwall Z-11. This study is followed by a description of the model that is used for a case study, considering three variants of the shearer position. Finally, initial simulation results and directions of further studies are discussed. [ABSTRACT FROM AUTHOR]

Flat air solar collectors are used for heat transfer between the absorber and the heat transfer fluid, to improve this transfer there are several methods. Among these methods, the exchange surface lengthening and the creation of turbulence. In this work is done to give a comparison between two types of solar collectors, so we have made an improvement of Ben Slama Romdhane's solar collector by creating two air flow passages to increase heat transfer. We made a 3D simulation of a flat air solar collector with transverse baffles which causes turbulence and increases the exchange surface; we use the ANSYS calculation code to make the simulation and gives results with a brief time and minimal cost. [ABSTRACT FROM AUTHOR]

In this work, a computational fluid dynamic approach is employed to investigate the flow and mixing characteristics of the fuel jet released from the trailing edge of the lobe strut at the supersonic free stream. Hydrogen is injected at sonic velocity while the supersonic freestream moves parallelly over the strut. The lobe shape of the strut is selected to generate strong streamwise vortices and consequently to boost the air/hydrogen mixing. The size and strength of the vortices are visualized through the 3-D contour of the mixing zone to reveal the chief effective terms on the fuel distribution inside the combustor. RANS equations with the SST turbulence model are used for the computational simulation of the supersonic air-stream over lobe strut. The impacts of free-stream Mach number and pressure of jet on fuel mixing are also examined. Moreover, the vertical and horizontal injection models are compared to reveal the mixing mechanism in the downstream of the lobe strut. Our results indicate that the vertical edge is more effective than the horizontal edge on the efficiency of the mixing zone. According to our findings, raising the free stream velocity increases the strength of the vortices and consequently, fuel mixing enhances in the downstream of the injector. Image 1 • Hydrogen fuel mixing of lobe strut injector at supersonic cross flow is studied. • The mixing efficiency of downstream vortex is fully investigated. • Jet pressure effects on fuel distribution are visualized. • CFD method is applied for the simulation of the high supersonic air flow over strut. [ABSTRACT FROM AUTHOR]

Abstract Invelox is a patented structure designed to capture the incident wind from every direction, guide the collected wind to the ground level and increase its velocity. Previous numerical studies have revealed that a considerable portion of the collected wind escapes the structure from the opposite side of the wind entering Invelox. In the present study, three possible curtain designs are proposed to reduce or fully-eliminate this escaping air. The improved capability of Invelox to augment the wind velocity using these curtain systems is evaluated via numerical simulations. The results show that the best configuration can fully eliminate the escaping air and it will not disturb the air flow uniformity inside the Venturi section. On average, the best design can lead to a 25% increase in the average wind velocity inside the Venturi for the wind velocities of 3–12 m/s. The results also show that although it has been claimed that Invelox accepts wind from all directions, it can only be efficient at the incident wind directions of −90 to 90°. Increasing the turbulent intensity of the upcoming wind from 0 to 20%, however, has no considerable effects on the Invelox speed ratio. Highlights • Three curtain designs are proposed to improve the speed ratio of Invelox. • The proposed modifications are studied numerically. • The best modification eliminated all the escaping air from Invelox. • On average, a 25% increase in the wind velocity inside the Venturi section is achieved. • Invelox works efficiently for the incident wind direction of −90 to 90°. [ABSTRACT FROM AUTHOR]

The influences of throughput and operating parameters on internal airflow and cleaning performance for the air-and-screen cleaning unit were investigated. The throughput experiment showed that, the airflow velocities above the vibrating screen decreased by 1.3–15.5% for every 1.0 kg s −1 increase of throughput and which below the vibrating screen decreased by 2.7–8.1%. As a result, the cleaning performance has declined. Then, the airflow velocity measurement and cleaning performance tests were taken under 4.0 kg s −1 throughput with single factor experiment in which fan speed, airflow deflector angle and sieve opening were as factors. And, the Computed Fluid Dynamic (CFD) numerical simulations were carried out to analyze the movement trend of internal airflow as an auxiliary analysis method. The following viewpoints were obtained, the fan speed has a large effect on cleaning performance by affecting the overall airflow velocities in the cleaning unit. And, the airflow velocities above the vibrating screen increased from 0.2 m s −1 to 0.4 m s −1 for every 150 r min −1 increase of fan speed, which below the vibrating screen increased from 0.4 m s −1 to 1.1 m s −1 ; The highest airflow velocities area above the vibrating screen moved forward to the central position in the longitudinal direction as the airflow deflector angle increased; With the reduction for each 4 mm of chaffer opening, the airflow velocities above the vibrating screen increased by 0.2–0.4 m s −1 . At last, making mathematical relations between each operating parameter and the cleaning performance, and proposing the method of adjusting the single operating parameter under rated condition according to the throughput. They provide a basis for real-time automatic adjustment of the operating parameters in the air-and-screen cleaning unit. [ABSTRACT FROM AUTHOR]

ABSTRACT Lee, K.H. and Kim, T.G., 2018. Three-dimensional Numerical Simulation of Airflow in Oscillating Water Column Device. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1346–1350. Coconut Creek (Florida), ISSN 0749-0208. An Oscillating Water Column (OWC) is a wave energy converting technology that uses the compressed and decompressed airflow induced by the vertical oscillations of water column inside the chamber as a driving force of an airflow turbine. In this study, three-dimensional numerical simulations of a bottom-fixed OWC are performed to understand the interaction of an OWC device with regular waves. The open-source CFD model REEF3D is used, which is able to consider immiscible two-phases (air and water) using the Reynolds-averaged Navier-Stokes equations. The simulation capability of REEF3D is validated by comparison with experimental data for wave deformations caused by the OWC and air-flow fields and the airflow velocity in the chamber. The numerical results revealed that the CFD numerical tool REEF3D can successfully simulate wave deformations caused by wave-OWC interactions, and directly estimate an air velocity inside the chamber. In addition, it was found that a phase difference occurs between time series of free surface evolution and air velocity evolution. [ABSTRACT FROM AUTHOR]

The existing experimental methods and numerical models were difficult to get accurate aerodynamic characteristics of the anti-torque system of a NOTAR under rotor wake. To solve this problem, a new three-dimensional aerodynamic model with momentum source based on finite volume method was proposed in this paper. By means of time domain equalization and spatial interpolation, the complicated dynamic meshes on blade were replaced by the nonblade fixed rotor domain with momentum source. And the model was calculated by steady, compressible and three-dimensional Reynolds averaged N-S equation. In this paper, a typical NOTAR was took for research, the aerodynamic characteristics including flow field and variation regularity of lateral force with momentum coefficient of anti-torque system during hover condition was obtained by applying the above computational model, and the accuracy of which was verified by corresponding experimental data. In addition, the model was also used to analyze the key factors that influence working condition of the tail boom, including length of tail boom, area of nozzle and fan pressurization. And the curves of variation regularity were given. The model and work in this paper could provide reference for further research and design on anti-torque system for NOTAR. [ABSTRACT FROM AUTHOR]

The development of robust mathematical models could provide the necessary tools for a more rapid, efficient, and reliable spouted bed technology development. Computer simulations can be very useful to aid this design and scale-up process: firstly, they can contribute to obtain a fundamental insight into their complex dynamic behavior by understanding the elementary physical principles such as drag, friction, dissipation etc.; secondly, the simulations can be used as a design tool where the ultimate goal is to have a numerical model with predictive capabilities for gas-particle flows at engineering scale. Clearly, one single simulation method will not be able to achieve this goal, but a hierarchy of methods modelling phenomena on different length and time scales can achieve this. The most fruitful approach will be when they are simultaneously followed, so that they can mutually benefit from each other. In this sense, this paper presents a review of the current state of the art of modelling on spouted and spout-fluid beds through an analysis of recent literature following a multiscale approach (molecular and particle, lab, plant and industrial scale). The main features of the different scales together with their current limits are discussed and specific topics are highlighted as paths that still need to be explored. In summary, the paper aims to define the theoretical setline and the basis of improvement that would lead to a robust multiscale model with solid links between micro and macroscopic phenomena. If done with the correct balance between accuracy and computational costs it will gear SB towards their reliable and successful implementation. [ABSTRACT FROM AUTHOR]

In this paper, three-dimensional wind flow patterns over a star dune under a longitudinal (W, 270°) and transverse airflow (ENE, 70°) were examined using computational fluid dynamics (CFD) simulations. New surveying techniques of airborne LiDAR and DGPS allow for establishment of the realistic digital model of the star dune. Simulation results were then validated by field measurement using three-dimensional (3D) ultrasonic anemometers combined with arrays of HOBO cup anemometers. Results show that incident flow conditions (longitudinal or transverse airflow) controlled by the angle between incident flow and dune crestline exert great impact on wind flow patterns over the star dune. In periods of longitudinal airflow, a marked feature of wind flow pattern was flow deflection. Wind erosion occurs on both sides of WNW and S sides during W wind and its main effect was to prolong the star dune longitudinally. However, leeside flow separation and reversal were obvious under transverse airflow. The main effect of ENE wind was to promote the upward growth of the star dune. The CFD simulation of 3D wind flows over complex dune system presents great potential for geomorphological research, enabling new insights into complex dune geomorphology and dynamics. [ABSTRACT FROM AUTHOR]

In this study, a fully unsteady computational fluid dynamics (CFD) model was used and the transient airflow properties during the entire breathing cycle, including inhalation and exhalation in a human nasal cavity, were evaluated. Unsteady particle tracking was performed to find the particle motion and deposition in the nasal airway using a Lagrangian approach. In most of earlier computer simulations, the assumption of quasi-steady or steady airflows averaged over the inhalation cycle were typically used to reduce the computational cost. In the present work particular attention was given to assessing the accuracy of these assumptions and their consequence on particle deposition in a human nasal cavity with paranasal sinuses. The simulation results for the airflow field showed significant differences between the unsteady and quasi-steady cases at low breathing rates near the beginning and end of the inspiration cycle. For breathing under a rest condition with a frequency of 0.25 Hz, the quasi-steady airflow assumption in the nasal cavity was found to be reasonable when the instantaneous Strouhal number was smaller than 0.2. The instantaneous deposition of micro-particles was also studied, and the effects of unsteady accelerating and decelerating flows on the deposition fraction were examined. The simulation results showed that the deposition fractions were affected by the accelerating and decelerating airflows during the inhalation phase. The simulated micro-particle depositions under the cyclic breathing condition were compared with those for steady breathing with an equivalent mean airflow rate. It was found that while the general trend was similar, the steady breathing simulation with the mean airflow rate during inhalation cannot accurately predict the total micro-particle deposition for cyclic breathing, particularly for 1–5 µm particles. Furthermore, the predicted regional depositions by the steady breathing were markedly different from those obtained under cyclic breathing. [ABSTRACT FROM AUTHOR]

The objective of this study is to analyze the solid and fluid flow behaviors inside a rotary drum using computational fluid dynamics (CFD). The CFD model developed was based on an Eulerian–Eulerian multiphase flow approach. The capability of the multiphase CFD model to predict the transverse and axial solid flow patterns, the fluid flow profile, and particle residence time was assessed. The model was used to study the effects of drum rotational speed, filling degree, feed rate, and drum inclination angle. It was verified using experimental results of particle and fluid velocities and residence time. The experiments were conducted on pilot scale rotary drums. As could be proved by measured and simulated results, the particle flow near the bed surface exerted a strong entrainment effect on the transverse air flow in the proximity of the bed surface. The study demonstrated the capability of the multiphase CFD model to predict the particle and fluid flow behaviors inside a rotary drum simultaneously. [ABSTRACT FROM AUTHOR]

In the mechanical ventilation room, human body will block the air flows and change the original airflow organization. In the crowd places, the influence of the crowd may greatly change the indoor air movement and even worsen the environment. So the effect can not be ignored. The paper studied the influence of the human body to the indoor air movement by using the method of Particle Image Velocimetry (PIV) and numerical simulation (CFD). The PIV experiment and numerical simulation contain two conditions. One condition is an empty room and another contains models of human body in the room. The paper compared the result of experiment and numerical simulation. Numerical simulations are demonstrated to be accurate in the two conditions, and the Standard k-ɛ model most accurately predicts the flow in a room contains crowd model. In this study, the numerical simulation and measurements show that the crowds will greatly change the air distribution and the residence time of the flows in the building. Therefore, it is important that crowds be considered in ventilation design. [ABSTRACT FROM AUTHOR]

This paper deals with studying of the aerodynamics characteristics in a residential building with a patio system connecting the inside with the outside. The numerical simulation is based on the resolution of the Navier–Stokes equations in conjunction with the standard k-ε turbulence model. These equations are solved by a finite-volume discretization method. The comparison between our numerical and experimental results developed using a wind tunnel shows a good agreement and confirms the validity of the numerical method. This proposed design presents an outlining environment suitable building in Tunisia. [ABSTRACT FROM AUTHOR]

An accurate prediction of flow and thermal fields around an human body provides valuable information in designing an efficient ventilation system. This study tries to address this issue by investigating the flow structure around an human body subjected to a displacement ventilation system through the computational fluid dynamics (CFD). For this purpose, both the large eddy simulation (LES) and hybrid LES–RANS methods are employed. The RAST one-equation model (OEM) and the dynamic Smagorinsky model (DSM) are utilized as a sub-grid scale (SGS) modeling for the LES while for the hybrid LES–RANS method, the SST–SAS version is applied. Predicted results are compared with available experimental measurements in the literature. Comparisons show that the OEM has a better performance in reproducing the correct level of velocity and temperature fields around the body as well as in other locations of the room while the SST–SAS model fails to predict these quantities accurately, especially around the occupant's body. Above all, the OEM provides a good compromise between accuracy and robustness in predicting the airflow and temperature fields in an indoor environment. [ABSTRACT FROM AUTHOR]

In this study, airflow and temperature distributions in the well-known International Energy Agency (IEA) Annex 20 room are predicted numerically to investigate the effects of the inlet turbulence intensity and the length scale on the flow characteristics, while considering the possibility of solution multiplicity related to chaos theory. The flow is considered to be turbulent, steady, incompressible, and two-dimensional. Computations are performed using the standard k – ɛ , RNG k – ɛ , standard k – ω , and shear stress transport k – ω turbulence models with scalable and automatic wall functions, and the results are compared with numerical and experimental results from the literature. The validated turbulence model is then used to investigate the effects of the turbulence intensity and the length scale. At a low inlet turbulence intensity value (Tu = 0.01), the length scale variation has no influence on the flow pattern. However, the length scale affects the flow pattern at a high inlet turbulence intensity value (Tu = 0.4). At constant low and medium length scale values, an increase in the inlet turbulence intensity from 0.01 to 0.4 affects the flow pattern. However, an increase in the turbulence intensity has no influence on the flow pattern at a constant high length scale value. [ABSTRACT FROM AUTHOR]

Abstract: A three-dimensional non-steady state shot peening simulation platform for coverage prediction is developed based on commercial Computational Fluid Dynamics (CFD) ANSYS-FLUENT software. To simulate the air–peen flow, the airflow is treated as a continuum phase governed by the Reynolds-averaged Navier–Stokes conservation equations, while the peen is taken as a discrete phase in which the trajectories of the peens are tracked individually. Two-way air–peen interactions are solved by exchanging mutual momentum during the peening process. User Defined Functions (UDFs) for particle loading distribution in the nozzle, particle dispersion, particle rebound, and nozzle movement are developed and incorporated into ANSYS-FLUENT. A numerical procedure based on the Eulerian–Lagrangian approaches is used in the solution. The air–peen simulation results based on the above model and numerical procedure is found to be in excellent agreement with the literature experimental data. For coverage prediction, both single dimple area and multiple impact coverage models are developed and validated by both experimental data and in-house Finite Element Method (FEM) simulation result. The obtained simulation results for coverage are in good agreement with existing experimental data. In addition, the simulations for two other configurations, that is, round-flat and airfoil NACA0012 specimens, are also performed to demonstrate the capability of the simulation platform. The present work shows that the multiphase shot peening simulation platform developed here can be used to accurately predict air–peen flow and coverage and to further optimize shot peening processes under real operating conditions. [Copyright &y& Elsevier]

Abstract: Numerical simulations using the computational fluid dynamics (CFD) software ANSYS Fluent were undertaken to characterize the airflow and temperature distribution in a natural convection thermal energy storage refrigerator. The model compared the household refrigerator temperature stability with different phase change materials (PCM) incorporated into the storage compartment. Scenarios investigated included the PCM orientation (vertical or horizontal), PCM temperature (use of water or eutectics) and compartment designs (conventional or drawer type appliance). The results suggested that a horizontal PCM configuration produces lower compartment temperatures than a vertical configuration. The temperature distribution with a horizontal PCM was tested experimentally and the results were in agreement with the CFD predictions. Both the simulation and the experimental results suggest that a eutectic with a phase change temperature below 0 °C must be employed to maintain the compartment temperature within acceptable limits. The model indicated that combining horizontal and vertical PCMs in a full height compartment or dividing the same compartment into two drawers with a horizontal PCM configuration for each drawer are feasible design options for the household thermal storage refrigerator. [Copyright &y& Elsevier]

Abstract: When a wind flow approaches a building, a recirculation zone is created on the leeward side of the building. This turbulent zone behind the building increases the air mixing at the leeward openings between entering and leaving air. As a consequence the effective temperature difference is reduced at the opening, counteracting the stack effect. Therefore, the air change rate is lower than that in absence of wind. Some empirical correlations have been set up to assess the airflow rate due to the combination of stack and wind effects. However these correlations do not take into account the reduction of airflow rate in leeward conditions. This paper aims to improve the existing correlations and in particular to confront the issue related to leeward openings. The study is based on CFD simulations and full scale experiments. A comparison of Warren''s correlation with CFD and experimental results shows that this correlation captures well the stack and wind effects in windward conditions but shows poor results in leeward conditions. Thus, a new correlation has been developed by using CFD simulations in leeward conditions. The new correlation is then compared with the full-scale experiments and concords well. [Copyright &y& Elsevier]

Abstract: Melt blowing combines extrusion of molten polymer through small orifices with stretching of the hot extrudate by hot air jets to create long, small diameter, fibers. Simulations and experiments were performed to examine: (1) the influence of increasing air pressure inside the melt blowing die (P inlet) on the air jet in a typical melt blowing process and (2) the influence of a Laval nozzle (a converging–diverging nozzle) on the air jet. The baseline case without a nozzle was simulated and examined based on the y-component of the air velocity profile, v y(y), at the centerline as a function of P inlet. As P inlet increases: (1) the air flow goes from subsonic to supersonic and (2) the maximum value of v y(y) increases with increasing P inlet, then starts to oscillate with the formation of compression waves in the supersonic region, P inlet≥15psig. Simulation also showed that a Laval nozzle influences the air flow field by increasing the maximum value of v y(y) and eliminating the compression wave at a predictable value of P inlet. Actual density oscillations in the supersonic flow field exiting a melt blowing die, with and without a Laval nozzle, were captured using a Schlieren visualization technique. In both limits the experimental results are in good agreement with the density oscillation in the supersonic flow field of the air jet anticipated by the simulations. [Copyright &y& Elsevier]

Cotton turf and hotwire measurements were used to experimentally assess the highly swirling flow characteristics in a spray dryer fitted with a rotary disc atomizer. The numerical simulation captured key features of the flow field. Analysis revealed that rapid rotation of an atomizing disc tends to centrifugally split the central inlet jet. The flow field exhibited significant long time-scale transient behaviour. However, this centrifugally split jet resulted in a balanced upward recirculation region in the chamber as expected by the jet-feedback mechanism. Detailed analysis using a 'transient air-steady particle' approach revealed that this approach is applicable for such highly swirling transient flows as well. However, caution should be exercised when interpreting the deposition results, particularly in regions of low particle velocities. This is anticipated be an important consideration in future attempts to simulate the predominantly transient flows in spray dryers. [ABSTRACT FROM AUTHOR]

This paper studies the flow and temperature patterns in an overhead diffuser based data center. In-situ measurements of the data center were carried out to validate a mat hematic model for predicting the effect of different air distribution systems. With the measured data of temperatures and airflow velocities, the mathematic model is constructed using a commercial Computational Fluid Dynamics (CFD) software and experimental data to present a comparison between test results and numerical simulations. The area of the data center is 311 square meters and the heat load of the equipment is 320 ∼ 360 watt per square meter. In-situ temperatures and humidity of the data center were measured with an Automatic Temperature and Humidity measuring instrument, whose error is ±0.5 °C. The discrepancy of the temperature and velocity between the numerical and experimental results were within ±2.3°C and ±1.8 m/s, respectively. In addition, analysis shows that changing the volume flow rate of the cold air delivered to some diffusers can optimize the temperature field and thereby save the energy. [ABSTRACT FROM AUTHOR]

Personalized ventilation (PV) is aimed to improve the quality of inhaled air by delivering clean, humidified and temperature-controlled air directly to occupants' breathing zone. The purpose of this paper is to investigate the effect of PV devices on the concentrations of volatile organic compounds (VOCs) emitted from carpet and the temperature around an occupant in an office. Numerical simulations were conducted using the computational fluid dynamics (CFD) commercial software FLUENT 6.3 for solving the continuity, momentum, energy, turbulence and concentration equations, and the simulation results were validated against the existing experimental data [1]. Personal exposure effectiveness (PEE) and manikin-based equivalent temperature change (ΔT) were used as indices to evaluate the performance of the PV. The results showed that the existence of the PV device greatly influenced the temperature and VOCs distributions around the occupant, but had little effect on those in the other parts of the office. Two evaluation indices increased with an increase of air flow rate. However, PV's airflow rate had larger influence on Manikin-based equivalent temperature change than that on personalized exposure effectiveness. The ventilation strategies had a great influence on the two evaluation indices, and both of them decreased with an increase of ventilation rate. The findings of this research could contribute to the reduction of energy consumption and the improvement of utilization of PV devices. [ABSTRACT FROM AUTHOR]

Abstract: Air distributions in commercial airliner cabins are crucial for creating a thermally comfortable and healthy cabin environment. This paper reviews the methods used in predicting, designing, and analyzing air distributions in the cabins, among which experimental measurements and numerical simulations are the two popular ones. The experimental measurements have usually been seen as more reliable although they are more expensive and time consuming. Most of the numerical simulations use Computational Fluid Dynamics (CFD) that can provide effectively detailed information. Numerous applications using the two methods can be found in the literature for studying air distributions in aircraft cabins, including investigations on more reliable and accurate models. The review in the paper shows that the studies using both experimental measurements and computer simulations are becoming popular. And it is necessary to use a full-scale test rig to obtain reliable and high quality experimental data. What’s more, the hybrid CFD models are found to be rather promising for simulating air distributions in airliner cabins. [Copyright &y& Elsevier]

Abstract: Accurate prediction of frost characteristics has crucial influence on designing effective heat exchangers. In this paper, a new CFD (Computational Fluid Dynamics) model has been proposed to predict the frost behaviour. The initial period of frost formation can be predicted and the influence of surface structure can be considered. The numerical simulations have been carried out to investigate the performance of fin-and-tube heat exchanger under frost condition. The results have been validated by comparison of simulations with the data computed by empirical formulas. The transient local frost formation has been obtained. The average frost thickness, heat exchanger coefficient and pressure drop on air side has been analysed as well. In addition, the influence factors have also been discussed, such as fin pitch, relative humidity, air flow rate and evaporating temperature of refrigerant. [ABSTRACT FROM AUTHOR]

In the framework of the COST 732 action, several teams run models to verify the proposed Best Practice Guideline (Franke et al., 2007). The data set concerns the Mock Urban Setting Test (MUST) experiment, where wind field and dispersion measurements were conducted for an array of obstacles as a full-scale experiment, as well as in a wind tunnel. The pollutant transport research group at the Department of Fluid Mechanics of the BME started simulations of flow within this idealised city using two commercial CFD codes, FLUENT and MISKAM. The paper presents results of the flow simulations in the 0 degree MUST case through velocity profiles, contour plots and validation metrics. [ABSTRACT FROM AUTHOR]

Abstract: Since old churches have had heating installed, more complaints have arisen of organs sounding out of tune. Sound frequency of organ pipes is dependent on air temperature. Old churches tend to have very large volumes, so are typically heated just before and during services in wintertime, in order to reduce energy usage. Warm air plumes rise at radiators and spread out into the room, finally reaching the cold organ casing where they cause a non-uniform temperature distribution within. If pipes standing in different temperature zones are played at the same time the organ sounds out of tune due to clearly audible beats (interference between two slightly different frequencies). The purpose of this study was to design a ventilation system inside the organ casing, able to create a uniform temperature distribution around the pipes. A computational fluid dynamic (CFD) model was developed for the St. Martin church in Oberesslingen, Germany. It was validated by on-site measurements that had been carried out in the organ casing of the church. Four organ divisions containing 300–500 pipes were represented by equivalent porous material zones. Their properties were determined using an auxiliary two-dimensional model of a staggered array consisting of 392 pipes. The effect of different ventilation system settings on the temperature field in the organ casing was examined. Best results were achieved by a system consisting of two ventilation lines together with a thin, synthetic net placed at the open interface between church and organ casing in order to reduce warm air inflow. [ABSTRACT FROM AUTHOR]

Abstract: This work was carried out in order to study heat transfer by natural convection in domestic refrigerators without ventilation. Only the refrigerating compartment was studied for three configurations: empty refrigerator, refrigerator equipped with glass shelves and refrigerator loaded by product. Both experimental and numerical approaches were used. The simulations were carried out using CFD (computational fluid dynamic) software by taking into account or by neglecting radiation heat transfer. The following conditions were assumed: constant evaporator temperature, three-directional laminar air flow. Numerical results show temperature stratification in the refrigerating compartment (warm zone at the top and cold zone on the bottom) for all configurations. A comparison of the calculated air temperature and the experimental values shows good agreement when radiation is taken into account. [Copyright &y& Elsevier]

This paper proposes a simplified system based on a new air supply opening model and a numerical method of solving the discrete algebraic equations to accelerate and simplify the convergence procedure of predicting air distribution in ventilated rooms. The so-called “N-point air supply opening model” is applied to describe boundary conditions of air terminal devices in computational fluid dynamics calculation. It directly and accurately describes inlet boundary conditions and models inlet mass, momentum and buoyancy flows. The new numerical method is called error pre-treatment method, which solves the algebraic equations first on coarse meshes to pre-treat low-frequency error before solving on finer meshes. It is simpler than multi-grid method and effective for SIMPLE algorithm that is commonly used for indoor airflow simulation. A zero-equation turbulence model is adopted to further simplify the simulation. These models and methods constitute the simplified system of indoor airflow simulation. The airflow in a room ventilated by displacement diffuser, square diffuser, and grille diffuser is calculated by the simplified system, respectively. Comparing calculated results to measured data, it is evident that the simplified methodology can predict indoor airflow quickly with satisfactory results for engineering applications. [Copyright &y& Elsevier]

The rapid development of data center (DC) construction and its high energy consumption problem has caused widespread concern all over the world. Effective airflow management is considered to be a reliable method to improve the utilization of cooling capacity and energy saving of air conditioning system (ACS) in DC. An innovative method of airflow optimization applying deflector in cold aisle containment (CAC) is proposed to improve the uniformity of airflow distribution in this paper. It is found that, in numerical simulation the application of deflector can improve the cooling efficiency of airflow, and the application of convex deflector with height of 1700 mm can obtain the best thermal environment. Meanwhile, the hotspot area of the rack is greatly eliminated and the uniformity of airflow distribution is improved. Furthermore, the thermal performance of DC is compared between the basic and optimal cases under five rack power (1.8 kW, 2.4 kW, 3 kW, 3.6 kW, and 4.2 kW) and three operating parameters (18 °C, 3.5 m3/s; 20 °C, 4.4 m3/s; 22 °C, 5.4 m3/s), and the accuracy of the numerical simulation is verified by field experiments. It is found that the application of the deflectors can reduce the heat accumulation of the rack in different scenarios, avoid the damage to the servers, improve the utilization of cooling capacity, and improve overall thermal environment. Results show that the deflector with optimal structure has wide applicability. • Strategy of applying deflector in cold aisle containment is proposed. • A convex deflector with a height of 1700 mm is found the best optimization. • The optimized structure has wide applicability under different work conditions. • High temperature and air volume can improve the uniformity of the rack along aisle. [ABSTRACT FROM AUTHOR]

The ventilation system plays a crucial role in every building. Proper design and optimization of its operation increase the comfort of users due to efficient air exchange and at the same time control its velocity in the rooms. The aim of this paper is the analysis of the effect of plenum box entry on the velocity profile concerning the diffuser face panel. This issue may sometimes be ignored at the design stage but can significantly affect the airflow from the diffuser and consequently increase the risk of draft. The results of the PIV experimental measurements and numerical simulations concerning various entries of the plenum box (top and side) were investigated in this study. The measurements were used to develop the mathematical and numerical models, which were then used to assess the effect of localization of the spigot of the plenum box on its operation. The numerical analysis was carried out on plenum boxes with the air diffuser with a face panel composed of square grid perforations. Analyses show that the entries significantly affect both the way of air distribution inside the plenum box and the profile of the airflow and its velocity under the simulated air diffuser. [ABSTRACT FROM AUTHOR]

• The conventional way for the water atomization is to force it at high velocity through a small aperture of atomizer. • Ultrasonic gas atomizers have been studied to obtain fine water fog. • The modern industrial use of ultrasonic is commonly related to Galton's development of moderately high-power ultrasonic whistles. • Through the research, generation of ultrasound by resonance chamber was decided and dimention analysis was performed. • The research results show that frequency of ultrasound generated is 22–24 kHz and mean dimention of water fog formed is 15–50 μm. • These technical characters of ultrasonic gas atomizer were established through numerical simulation by CFD software-ANSYS Fluent and its correctness was proved through the experiment. The water spraying itself is a dynamic course, and it is affected not only by structural style of ultrasonic gas atomizer and compressed air pressure, but also by movement of compressed air flow and so on in the atomizer. Here, the main principle of fine droplet formation in the ultrasonic gas atomizer is that the liquid sheet is disrupted into droplets by the energy of the high velocity air. If the ultrasonic energy is supplied, finer droplets with high sphericity and uniform size distribution can be achieved. But it is difficult to measure the droplet sizes. An ingenious method of droplet measurement was attempted by capturing the droplets on a filter paper and there are subjected to image analysis to obtain the droplet sizes. However, droplet measurement is complicated and the correctness of the droplet sizes is not high. Also advantage of all of the device newly designed is not defined until the experimental measurement are advanced after they are manufactured. As development of an interpretative program, droplet measurement through the numerical simulation was attempted. This paper deals with the water atomization of ultrasonic gas atomizer by numerical simulation with CFD software-ANSYS Fluent. In this paper, generation of ultrasound is decided in the ultrasonic gas atomizer with resonance chamber and ultrasound characters (frequency, pressure level, power level) are decided. These results are proved through the comparison with experiment. The results indicate that ultrasonic gas atomizer is effective to apply to the industrial field such as dust cleaning process. Rational structure parameter and operating parameter are studied in next issue. [ABSTRACT FROM AUTHOR]