Tracer gas measurements have Jong been used to quantify the performance of ventilation systems by exploring such scales as the air exchange efficiency, the local mean age of the air, the residence time distribution and so on. The present work deals with a numerical reexamination and calibration of some relations previously derived from tracer gas analysis.
Ventilation is increasingly a subject of concern due to its relation with health and energy loss. Environmental pollution and global warming demands energy conservation and a Airtight structures are being built to reduce the energy losses due to infiltration. Reduced air change rates may lead to accumulation of C02 and other toxic pollutants to undesirable levels. In view of such concerns tests are carried out here to study the influence of ventilation on indoor air quality and thermal conditions in a naturally ventilated building.
With the purpose of evaluating validity of the application of CFO on the problems of cross-ventilation, numerical simulation was performed, using standard k- E model and two types of modified k-E models which improve evaluation accuracy in production term of turbulence energy, and also using LES, and the results were compared with those of the corresponding wind tunnel experiment. As a result, it was found that the defects of the model characteristic to the standard k- E model could be improved to a certain extent by application of the modified models.
Solar energy air-collectors installed on the sun-oriented building facades can be used for improving natural ventilation of adjacent rooms. The basis of the physical process is an unbalanced buoyancy force arising from the temperature difference between ambient and the air inside the room. Although difficult to control due to the variability of the climatic conditions, these devices can be used as means of reducing the need for conventional energy to provide indoor air conditions within acceptable limits required by health and comfort considerations.
For the academy Mont Cenis in Herne, Germany, a large microclimatic glass envelope (72m x 1.80m x 15m) with separate buildings inside the envelope, a concept for the natural ventilation was put up and a program for the control of the motor driven windows in the facades and in the roof was developed. To comprise the influence of wind speed, wind direction and the temperature difference between the envelope and the environment, numerous CFD-calculations were carried out on the base of a wind tunnel test and dynamic thermal calculations.
Natural cross ventilation to take advantage of air velocity in getting comfort, and solar protection, are the main design criteria traditionally proposed for warm humid climate. Usually, priority is given to natural ventilation related to design decisions such as orientation and windows (size, location and type). However, the wind is the most variable climatic factor, also affected by the urban context, the architectural shape and even, opening and closing windows and doors.
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