This paper presents results of a study where computational fluid dynamics (CFD) was the numerical tool used to analyze the ventilation performance in stations of the Buenos Aires Metro subway system. Both natural and mechanical ventilation options were studied. The study showed that although natural ventilation was sufficient to maintain the temperature criteria, it presented a potential egress problem by letting hot gases leave through the entranceways.
This Update is the first of two that discuss mechanical ventilation systems in houses. It explains why houses need to be mechanically ventilated, and examines the main characteristics of an ideal system from the standpoint of design and installation.
Current approach for design and installation of mechanical ventilation systems in houses is described in the framework of Canadian building codes and standards, which contain requirements about air change rates, air distribution, sound level, interference with other systems or building envelope.
The ventilation performance in 59 terraced houses of similar construction was investigated using a passive tracer gas technique. Some thirty houses were ventilated through the original natural ventilation, while eight were equipped with an additional bathroom fan and 20 were retrofitted with a mechanical supply and exhaust ventilation system. All measurements were made simultaneously in March. The ventilation performance was computed using both single-zone and two zone approaches.
Mechanical ventilation in buildings requires appropriate systems for heating and cooling. The costs of energy demand represent a high percentage of the global costs for climatisation. As a part of a project concerning these subjects the development of a computer code for evaluating energy load due to mechanical ventilation in buildings is in progress. The mathematical model is based on simplified equations to fit dynamically the psychometric curves. Inlet air flow rates are evaluated according to the more recent Italian regulations.
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