Enhancement of Natural Ventilation using Solar Chimney: A Numerical Investigation

Rural areas have shortage of electricity, so natural ventilation becomes necessary. Ventilation through solar chimney harnesses solar energy as energy source and can be installed in rural buildings for improvement of air circulation. Rate of ventilation of a solar chimney for natural ventilation was investigated for both Horizontal type and Vertical type. Ventilation rate greatly depends on the temperature gradient of the room. The current work presents the comparative analysis of a room apartment with solar chimney of both types attached to them. In this study, a reduced scale Chimney of Horizontal and Vertical design is modelled through CFD to investigate the improvement of Natural Ventilation. Two different parameters have been considered for current study viz. Outlet Velocity and Temperature of Absorber plate

Use of fabric membrane topology as an intermediate environment modifier

This paper describes the pattern of airflow around membrane structures, and how they along with the form of the structure itself affect the ventilation rates within their enclosures or their immediate vicinity. Examples that have successfully used membrane skins in the built environment will be reviewed. The possible use of tensile membrane structures topology and orientation to enhance ventilation rates and natural cooling within the semi-enclosed spaces will be discussed. The use of the indigenous fabric skin to tackle key climatic concerns in a simple, elegant manner is discussed along with the review of the wind tunnel experimental visualisation and measurements carried out by the author. These structures go beyond simply providing shading to illustrate innovative, environmentally friendly fabric Architecture, but if properly understood the fabric’s form and topology can play an effective role in the ventilation and natural cooling of spaces in their immediate vicinity

Currnent and likely future performance of advanced natural ventilation

Advanced natural ventilation (ANV), often characterised by the use of dedicated ventilation stacks, shafts and other architecture features such as atria, light wells, has gained popularity for natural ventilation design in recent decades. In this research, a prototype ANV system is proposed, and the likely thermal performance in a range of UK climatic conditions predicted using dynamic thermal simulation. The simulations showed that ANV has greater resilience to future climatic conditions in the north of the UK than in the south-east and that, for the assumed internal heat gains, the design studied is unlikely to maintain comfortable conditions in the southeast of England beyond the middle of this century

Optimization of Window Positions for Wind-Driven Natural Ventilation Performance

This paper optimizes opening positions on building facades to maximize the natural ventilation’s potential for ventilation and cooling purposes. The paper demonstrates how to apply computational fluid dynamics (CFD) simulation results to architectural design processes, and how the CFD-driven decisions impact ventilation and cooling: (1) background: A CFD helps predict the natural ventilation’s potential, the integration of CFD results into design decision-making has not been actively practiced; (2) methods: Pressure data on building facades were obtained from CFD simulations and mapped into the 3D modeling environment, which were then used to identify optimal positions of two openings of a zone. The effect of the selected opening positions was validated with building energy simulations; (3) results: The cross-comparison study of different window positions based on different geographical locations quantified the impact on natural ventilation effectiveness; and (4) conclusions: The optimized window positions were shown to be effective, and some optimal solutions contradicted the typical cross-ventilation strategy

Effective natural ventilation in modern apartment buildings

This paper addresses the challenge of evaluating for natural ventilation in modern apartment buildings. A number of natural ventilation design rules of thumb from published literature are listed. Their incorporation into one code for Australia (the Residential Flat Design Code, or RFDC) and India (the National Building Code, or NBC), in relation to apartment buildings is examined. Practical limitations to converting these rules of thumb into effective natural ventilation systems for apartment building designs are discussed. Apartment designs in the moderate locations of Sydney, Australia and Bengaluru, India are also reviewed to assess their effectiveness for natural ventilation. Simulation analysis presented indicate large energy savings are possible if apartments are retrofitted/designed to the proposed code requirements and designs compliant with thumb rules are capable of delivering effective natural ventilation if users choose to operate the apartment in “free running mode” during times when the outside dry bulb temperatures lie in an appropriate band. The paper also discusses how sub-optimal design solutions, affluence and adaptation to more stringent thermal conditions can negate the potential for natural ventilation and calls for proactive efforts to maintain climate responsive design standards and education/policy to encourage the benefits of natural ventilation over airconditioning

Study of natural ventilation for a modular façade system in wind tunnel tests

Wind tunnel tests are a reliable tool to determine the effect of natural ventilation on buildings. This paper presents results of wind tunnel tests conducted to evaluate the influence of ventilation modules positioning on a façade system. Modules positioning was modified, resulting in different façade configurations. The tests were carried out with the use of a model, varying the position of the ventilation modules in the façade configuration. The cases tested were six ventilation modules positioned below the window-sill (ventilated window-sill), and three ventilation modules positioned above and below the façade. The façade system proposed was movable and interchangeable so that the same basic model could be used to test the possibilities for ventilation. Wind speed measurements were taken inside and outside the model for the different façades configurations to evaluate the best performance in relation to natural ventilation. Singleâ sided and Cross ventilation were considered for wind speed measurements. Results show the use of six ventilation modules positioned below the window-sill, forming "a ventilated window-sill" is the best solution in terms of natural ventilation

CFD modelling of buoyancy-driven natural ventilation opposed by wind

This paper presents CFD simulations of natural displacement ventilation airflows in which the buoyancy force produced by a heat source is opposed by a wind force. Cases investigated focus on windbuoyancy force relationships for which a two-layer stratification is maintained. CFD predictions of the position of the interface separating the two layers and the change in reduced gravity (temperature difference) between them are compared with the analytical work and salt-bath measurements of Hunt and Linden (2000, 2005). Comparisons are good with only minor discrepancies in the interface position and a small under-prediction of the upper layer reduced gravity

Increased Natural Ventilation Flow Rates through Ventilation Shafts

Buoyancy-driven natural ventilation in ventilation shafts is investigated with a small scale physical experiment within a duct and CFD simulations of an office building. For a fixed exhaust opening, smaller shafts lead to higher flow rates in upper floors of a multi-storey building with a shared ventilation shaft. These higher flow rates are caused by increased vertical momentum within the smaller shafts that induce flow through upper floors, an effect referred to as the “ejector effect”. In the small scale duct, a 0.5 m by 0.5 m shaft leads to a slight reverse flow of 0.0029 m[superscript 3]/s through the upper floor. Holding all other parameters constant and reducing the shaft to 0.25 m by 0.5 m leads to a positive flow rate of 0.012 m[superscript 3]/s through the upper floor. In the CFD simulations of a three storey office building, this same pattern is observed. A 3 m by 2 m shaft leads to a flow rate of 0.0168 m[superscript 3]/s through the third floor, while the reduced shaft of 2 m by 2 m leads to a flow rate of 0.766 m[superscript 3]/s through the same floor. This increased airflow rate from the ejector effect can allow natural ventilation to be used in buildings where it may otherwise have been deemed inappropriate. Most airflow network models neglect air momentum and fail to account for the ejector effect. To improve these models, an empirical model is incorporated into the airflow network model CoolVent in a manner easily transferable to most airflow network models.Hulic Co., Ltd