natural ventilation

This paper presents results of a Large Eddy Simulation (LES) of buoyancy-driven natural ventilation in which two unequal heat sources are used to drive the flow. The aim of this work was to assess the performance of LES in modelling turbulent thermal plumes in a naturally ventilated enclosure and to analyse their interaction with each other. The sub-grid scales of the flow have been resolved by using the Smagorinsky sub-grid scale model. It was found that LES results for the interface height agree well with the theoretical predictions of Linden and Kaye (2006).

A double skin façade (DSF) aims at reducing heating and cooling loads by taking advantage of daylight and utilizing heated air for space heating. To take advantage of a DSF a sophisticated design is required. In this paper a DSF building that has overheating problems was selected to verify the causes and propose remedial solutions. The problem was verified by analyzing the measured solar radiation, inside and outside temperature and air velocity. The results of the measurement analysis showed that airflow congestion caused overheating inside the building.

This paper describes a re-analysis of internal pressure and building ventilation in a single-opening enclosure ventilated by winds. The dynamics of internal pressure is governed by a nonlinear oscillation equation. An alternative semi-nonlinear approach is proposed for obtaining the amplitude and phase shift of the periodic motion, the resonant frequency and resonant amplitude. Our new approach reproduced two of the commonly used existing linearization results.

Natural ventilation of buildings is a design strategy for the passive cooling of buildings that can be considerably efficient if properly undertaken. In Brazil, as in many other developing countries, spontaneous (self build) housing is often of poor quality. Also, each of these dwellings has a negative impact on the neighbouring ones and on the impact on the urban environment. In the city of Campinas, Brazil, with its hot-humid climate, adequate ventilation is essential for thermal comfort.

This paper presents a simplified modelling process by using experimental results to form empirical relationships for a particular novel windcatcher natural ventilation and cooling system developed by Monodraught in the United Kingdom. In particular, the behaviour of this system, which is integrated with a DC fan and PV panel without a backup battery, is modelled for the whole year. The impact of natural and night time ventilation with thermal mass on cooling and mitigating overheating is investigated.

In order to ascertain the relationship between opening conditions and indoor airflow characteristics, case studies were conducted by performing CFD analysis using the domain decomposition technique. Reproducibility of the domain decomposition technique was verified through wind tunnel experiments, and the correspondence was confirmed to be satisfactory. The authors confirmed the validity of a method of evaluating cross-ventilation performance which uses wind velocity ratios and ignores regional and meteorological locality.

Unlike cold climate regions, where natural ventilation is not preferred during winter, natural ventilation is always preferred in Hong Kong for cooling because of the subtropical climate. It also provides better indoor environment quality and energy conservation. Natural ventilation performance of a residential unit is affected by internal as well as external factors. External factors are often subject to constraints beyond the control of site planners and architects.

This paper discusses the potential of passive cooling techniques for Malaysian modern houses with the aim of reducing air-conditioning usage. A full-scale field experiment was carried out to reveal the detailed indoor thermal environment for various ventilation strategies. Night ventilation was found to be better than daytime ventilation, full-day ventilation and no ventilation in terms of air temperature reductions during the day and night. Night ventilation improves thermal comfort more than the other ventilation conditions based on operative temperature.

This paper reviews the application of CFD for designing and parametric studies of wind-induced natural ventilation. The approaches employed in such applications of CFD are whole-domain and domain-decoupled CFD modelling. The domain-decoupled technique separately analyses the external airflow fields outside and internal flows inside a building. In the whole-domain approach, the outdoor and indoor airflow is modelled simultaneously and within the same computational domain.

In contrast to mechanical ventilation, natural ventilation's performance is usually impacted by uncertain factors, including wind fluctuations, outside air temperature variations, and occupants' behaviours. These factors require a stochastic evaluation process for natural ventilation at the design stage such as quantifying the effective ventilation rates and optimising control strategy.