This paper refers to the use of natural ventilation in Portuguese urban housing stock. In order to assess the goodness of natural ventilation design rules defined in a new Portuguese standard, a research project is being carried out. The results of the measurements of temperature, humidity, flow rate in ducts and weather conditions taken at an apartment in Matosinhos are presented.
Different measurement procedures are available for the experimental assessment of air change rates inside ventilated enclosures. These mainly consist of tracer gas techniques and can usually be applied to steady-state or moderately transient conditions and when a continuous mixing of the indoor air is assured throughout the test. However, due to the relatively slow response of the gas analysers, none of these procedures can usually be applied to fast transient phenomena that last 15 minutes or less.
We consider the overnight evolution of an initial two-layer thermal stratification (a warmupper layer and a cooler lower layer) in an enclosure ventilated via openings at high and low levels.Results of our laboratory experiments show that an efficient displacement flow is not always established and four distinct ventilation flow regimes are observed depending on the ratio R (= at /ab ) of the upper opening area, at , and lower opening area, ab ( > 0). For a given initial stratification, displacement flow is established only if R is sufficiently small (i.e. at
The natural ventilation of a room with a source of uniformly distributed heating at the base andwith vents at multiple heights is investigated both theoretically and experimentally. It is shown that the impact of additional vents can be predicted by determining the height of neutral buoyancy. As a room is heated it heats up to a uniform state and the relative height of neutral buoyancy depends on the ratio of the upper and lower vent areas. When a simple additional intermediate level vent is introduced a unique solution can be used to predict the resulting air flow.
The 40 story high-rise headquarter of the Deutsche Post AG in Bonn features an integratedcomfort and low energy concept. Contrary to common high-rise design, the building does not require a central mechanical ventilation system. Instead it is decentrally ventilated by a double faade, which decreases wind loads and allows for natural ventilation through window openings.The typical floor plan is designed to provide a cross ventilation from the double faade through officerooms to a central atrium serving as exhaust duct.
Using computational fluid dynamics (CFD) techniques to model buoyancy-driven airflows hasalways proved challenging. This work investigates CFD modelling of buoyancy-driven natural ventilation flows in a single-storey space connected to an atrium. The atrium is taller than the ventilated space and when warmed by internal heat gains producing a column of warm air in the atrium and connect space drives a ventilation flow. Results of CFD simulations are compared with predictions of an analytical model and small-scale experiments [1].
The main goal of this work is the modeling of the flow field and temperature distribution in thekitchen of a house where natural ventilation techniques were implemented. The Fluent 6.1 commercial CFD software was used. The k- e turbulence model and the Boussinesq approximation for buoyancy were employed. The heat released from a water heater in continuous operation dictates the temperature distribution in the kitchen. Several simulations were performed by varying the boundary conditions and seeking agreement with the available experimental data.
Evaluating naturally ventilated buildings for performance is a difficult task, often relying oncomputer simulations and modeling to assess thermal comfort and airflow issues. This paper presents the long and short term monitoring procedures and data devised to determine the overall building performance of a naturally ventilated office building in the United Kingdom.
One of the main arguments supporting the application of the natural ventilation is the reduction inenergy consumption and capacity of the HVAC system. Here several tests of the building with different systems are carried to quantify the differences in capacities and energy consumptions of different solutions for the HVAC system. The tests were carried with the simulation program built in Simulink. To validate the model the measurements were done in Test cell at TU Delft as well as in the real office building.
This paper discusses the concept and performance of a naturally ventilated building with a double-skin facade in Tokyo. The building incorporates a hybrid ventilation system (natural ventilation integrated with air-conditioning systems) that makes use of buoyancy forces generated in a vertical airshaft in the center of the building. Field measurements were made in order to evaluate the performance of the double-skin facade during the summer and winter and also the performance of the hybrid ventilation system during the spring and autumn.
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