Wind-driven single-sided ventilation is present in many existing buildings globally, and its performance can be unreliable and challenging to improve. To address these performance challenges, a ...better understanding of the interconnected relationship between the external and internal flows is required. Therefore, a detailed assessment of this type of natural ventilation is vital. A detailed CFD analysis of wind-dominant single-sided natural ventilation is presented by adopting the Large Eddy Simulation method, validated using previous wind tunnel studies. An isolated cube, representing a three-storey building, was used to investigate four case studies with different opening positions on the building façade. The presence of parallel flow near the building façade and the effect this has, both on the structure of the flow at the opening and the internal secondary flow, is investigated. Results demonstrate that a mixing layer jet of air is the main structure of the flow at the opening. The flow characteristics of this jet are a function of how the external near-façade flow interacts with the building. It can be deflected or attenuated by the near-façade fluctuating pressure and vortex structures close to the opening. Tracer gas decay results show that only 3/5 of the flow at the opening contributes to effective ventilation in this type of natural ventilation. Comparisons between the ventilation rates for openings at different positions on the building façade demonstrate the importance of the pressure role at the opening in single-sided natural ventilation.
•Interconnection relationships between internal and external flows are assessed.•Phenomena in SSV are interpreted by understanding the coupling between the external and internal flow.•The mixing layer is a 3D jet inclined based on the position of the opening relative to the highest-pressure point.•In SSV, 2/5 of the total air at the opening short-circuits (does not contribute to the effective ventilation rate).•Indoor air distribution in SSV depends on the position of the opening on the building facade.
•Smoke spread speed affected by HRR, rather than environmental wind.•At early stage of tunnel fire, downdraught phenomenon will occur.•Plug-holing does not occur under higher wind speed with stronger ...blocking effect.•Strong environmental wind restricts circulating process of smoke through shaft.•Higher wind speed or smaller HRR leads to lower smoke exhaust efficiency.
In order to investigate the effect of strong environmental wind on a tunnel fire under natural ventilation, a series of numerical simulations were conducted using large eddy simulation method in this study. A tunnel model was established by a numerical simulation software, Fire Dynamics Simulator, to investigate the smoke movement under the stack effect induced inside a shaft. Four environmental wind speeds (39 m/s) and three heat release rates (3–20 MW) were considered. The smoke spread velocity inside the tunnel, downdraught phenomenon at the early stage of fire, smoke exhaust characteristics at the steady period of fire, temperature distribution in the tunnel and shaft, and occurrence of plug-holing were studied in detail, based on some typical characteristic parameters, such as mass flow rate, temperature and velocity vector. The results can be considered as a reference for the fire protection design of a tunnel with natural ventilation.
User demand for increased internal thermal comfort conditions have resulted in rising energy costs for space-heating consumption. The present study aims to recover the thermal energy in ventilation ...exhaust air and transfer the energy to the incoming air, to be redistributed using natural ventilation windcatcher. A comprehensive review was carried out to explore heat recovery systems that can potentially be incorporated with natural ventilation wind catchers. A rotary heat recovery device suitable to be incorporated with a roof mounted multi directional windcatcher system was developed. Computational Fluid Dynamics (CFD) modelling and laboratory experimental tests were conducted to investigate the proposed system. In the first phase, a full-scale prototype of the passive rotary thermal wheel device was developed and tested in a crossflow channel to initially assess the concept and performance of the design. Two configurations of the passive heat recovery wheel were tested: 20 and 32 radial blades. The second phase focused on investigating the integration of heat recovery wheel into a windcatcher system. CFD modelling and scaled wind tunnel testing were conducted to assess the airflow and temperature distribution around the multi-directional windcatcher with a passive rotary wheel. The results showed that the addition of the heat recovery wheel rotating at 15 rpm reduced the indoor airflow speed between 14 and 30%, depending on the outdoor wind conditions. The system was able to provide the recommended fresh air rates when the outdoor wind speed was 1.5 m/s and higher. In addition to sufficient ventilation, the heat recovery system had a positive impact on the indoor air temperature, raising the temperature up to 3.7 °C depending on the indoor/outdoor conditions.
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•Passive heat recovery device developed for a roof mounted multi-directional windcatcher.•Comprehensive review conducted to explore heat recovery systems suitable for windcatchers.•Full scale prototype of the 3D printed heat recovery wheel tested using a cross flow channel.•Influence of radial blades design, rotation speed and wind conditions on performance evaluated.•The proposed system was able to provide the recommended fresh air supply rates.
This paper evaluates natural ventilation effectiveness in one fully dependent Air Conditioned-Educational Building in Depok to recommend potential passive cooling approaches toward user thermal ...comfort. This study involves building surveys to measure the temperature and humidity of three selected classrooms, A, B, and C, with varying configurations and capacities. Airflow simulation using Computational Fluid Dynamics (CFD) is done under two conditions: open and closed doors. A set of parameters, which are room configuration, type of window, and ventilation strategy, are set to evaluate natural ventilation aspects. The site survey indicates that only one classroom with an area of 92 sqm facing to the southside is classified as efficiently warm (Room A). The simulation demonstrates that cross-ventilation only occurs when the door is opened. The parameters indicating shape, dimension, type, and area of natural ventilation matter, show that the building’s natural ventilation is ineffective in providing thermal comfort. This study recommends that the building’s natural ventilation be placed according to the direction of the airflow, adding vertical fin elements, and increasing the openings by more than 5% area from the floor area.
Recently, curved double-skin façades (CDSFs) have been increasingly used in buildings due to the advantages of aesthetics and structure. However, existing studies mainly focus on planar double-skin ...facades (PDSFs) and barely address the thermal and ventilation performance of CDSFs. In this study, the influences of geometric parameters, glass material and solar radiation on the thermal and ventilation performance of the CDSF are studied with a CFD model validated by a reduced-scale experiment. The results show that the optimal cavity gap ranges from 0.75 m to 1 m, and the optimal ellipse aspect ratio is 0.5. Moreover, glass material shows a significant influence on the ventilation performance of the CDSF – an enhancement of 8.20%–21.31% more cavity velocity is found by replacing the clear glass with a low-e glass. Further analysis shows that the ventilation performance is more sensitive to the optical properties of glass material, and a higher absorptivity is more conducive to natural ventilation. Solar radiation – solar radiation intensities and solar incident angles - show predominant impacts on the cavity velocities of CDSFs with non-linear relationships. Because of the surface's non-uniformity distribution of solar radiation, solar radiation shows more impact on the cavity velocities of CDSFs than PDSFs. The influence of solar incident angles is found to be more sensitive, especially in the regions of big solar incident angles - the variation rates of cavity velocities for the CDSF under high solar incident angles (>45°) are much larger than that under low solar incident angles (<45°).
•The thermal and ventilation performance of the CDSF is analyzed.•Optimal cavity gaps and ellipse aspect ratios for the CDSF are obtained.•An improvement of 8.20%–21.31% in cavity velocity when using low-e glass.•The effects of structures on CDSFs appear more apparent compared to PDSFs.•Solar incident angle shows a more drastic effect on the performance of CDSFs than PDSFs.
•Investigate the impacts of window operation on building performance.•Simulate control strategies of window operation in EnergyPlus.•HVAC energy savings of 17–47% was achieved with mixed-mode ...ventilation for summer.
Operable windows provide occupants with the ability to control local environments and satisfy human expectation to access outdoor environments. Operation behaviors or strategies for operable windows have substantial impacts on the indoor environment and building energy consumption. Facility managers complain about operable windows left open in buildings with conventional HVAC systems. However, optimum control strategies of window operation reduce energy consumption for buildings via natural ventilation or mixed-mode ventilation. This study focuses on the investigation of the impacts of window operation on building performance for different types of ventilation systems including natural ventilation, mixed-mode ventilation, and conventional VAV systems in a medium-size reference office building. A building performance simulation tool—EnergyPlus—is used to simulate window operation for each system type. Various control strategies of window operation, simulated using the energy management system feature (EMS) in EnergyPlus, are evaluated based on the criteria of thermal comfort and energy consumption. The investigation included the interaction between conventional VAV systems and window operation as well as control strategies for natural ventilation and mixed-mode ventilation. The results highlighted the impacts of window operation on energy use and comfort and identified HVAC energy savings of 17–47% with mixed-mode ventilation during summer for various climates.
In this study, researchers investigated the efficacy of natural cooling in a residential building employing a horizontal windcatcher alongside a direct evaporative cooling system featuring a ...cross-flow pattern. ANSYS Fluent was used to model the three-dimensional airflow, while MATLAB measured the system's thermal performance. The study assessed thermal comfort and natural ventilation in accordance with the Adaptive Thermal Comfort Standard (ATCS) and ISO/EN7730 Standard. The impact of environmental conditions and window aperture on the hybrid system's functionality was scrutinized, culminating in design guidelines dictating the acceptable range of window openings to ensure compliance with thermal comfort conditions. The passive system demonstrated the capability to maintain thermal comfort within the test building under a maximum cooling load of 12,000 W (ATCS) and 6000 W (ISO/EN7730). Moreover, the natural cooling system decreased hourly electricity consumption during hot seasons in Tehran, Iran, by 0.0155 (kW/m2) compared to split air conditioners and 0.00087 (kW/m2) compared to evaporative coolers. The study also investigated the influence of neighboring buildings positioned at specific distances relative to the test building on the system's performance. Furthermore, adopting the suggested horizontal windcatcher instead of conventional vertical windcatchers resulted in a 50 % reduction in energy consumption.
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•A novel system for natural ventilation and cooling of residential buildings is presented.•A design guideline determining the allowable windows opening range is proposed.•Thermal comfort is obtained for a maximum of 12,000 W cooling load in the test building.•The system can decrease hourly electric energy consumption by about 0.0155 kW h/m2.
•A unique design of ventilated acoustic metamaterial window panels.•Simultaneous noise mitigation at target frequencies and efficient air circulation.•A sound absorption coefficient of more than 0.96 ...at 1000 Hz.•The transmission loss of 18 dB while maintaining the 45 % open area of ventilation.•Proof-of-concept for large-scale metapanels by using a jigsaw puzzle-like assembly.•Potential uses for low-to-mid frequency noise control in small-ventilated spaces.
The conflict between the acoustical performance and ventilation efficiency in conventional noise barriers limits their application potentials in several settings. To address this challenge, we design and experimentally demonstrate a ventilated tunable acoustic metamaterial for noise mitigation at targeted frequencies. Through the structure, a peak normal incidence sound absorption coefficient of more than 0.96 at 1000 Hz and the peak normal incidence sound transmission loss of 18 dB is achieved while maintaining the air circulation with a 45% open area of ventilation. Such a high absorption near the resonant frequency under the ventilation condition originates from high impedance matching between the metastructure and air. Next, we present a proof-of-concept for the fabrication of acoustic metapanels for large scale applications. A simple jigsaw puzzle-like assembly technique is used to interconnect the multiple unit cells, leading to the production of integrated metapanels. The experimental findings validate the potential applications of the proposed metapanels for low-to-mid frequency noise control in a small ventilated spaces.
