empirical models

The heating and cooling loads due to air infiltration may be estimated by a mathematical model that requires knowledge of the leakage characteristics of each component of the envelope. To extend the modelisation to the pitched roofs common in Portugal, characteristics of roofs were determined by a differential pressure method.

Compares wind pressures measured on a 1:25 scale model of a mobile home with results from a full-scale investigation. The modelling technique used exaggerates the surface roughness in order to match the full-scale turbulence intensity at the model height. Shows that there is reasonable agreement of themean and RMS pressure coefficients between model and full scale, when the pressure coefficients are normalized by the local dynamic head at the building height.

Shows the ventilation of electrowinning cell houses and electrorefineries as being a complex problem. Develops a systematic approach to define the important contaminant generation rates including heat, moisture and acid mist. Discusses fluid dynamic scale modelling as a powerful tool for solving a building's flow field and contaminant concentration field. Examines other associated problems, including wintertime fogging in the building and the high costs of make-up building heat. Presents the possibilities for reclaim of low-grade waste heat, and evaluates the economic impact.

Natural ventilation of mill buildings is a process which is complicated by several factors such as external wind pressure and local distribution of heat sources. Describes theoretical and small-scale physical modelling techniques for predicting ventilation rates. The theoretical approach using a computer for the numerical aspects allows rapid and reliable assessment of the ventilation rates for very complicated building designs under any appropriate wind conditions.

Describes results from wind-tunnel tests on models of the Building Research Establishment's experimental building at Aylesbury. The use of several scale models of this building in uniform and in simulated atmospheric boundary-layer flows together with the results from the full-scale experiments allow an assessment of the effect of variations in the ratio of the longitudinal- turbulence integral length scale to body dimension.

Uses a similitude approach to develop predictive graphs for the ventilation rate due to the stack or chimney effect. Uses a half scale model of an open side wall structure with a continuous and restricted open ridge, and finds that:< 1. Ventilation rate is approximately proportional to ridge outlet width< 2. Outlet Reynolds number response ie ventilation rate to changes in Grashof number is a function of the ratio between building height and ridge width.

Briefly reviews ventilation requirements, types of ventilation , driving mechanisms for natural ventilation and infiltration, natural ventilation, infiltration and air leakage, air leakage sources, empirical models and infiltration measurement.

The study concerns the problems and prediction of room flow in air-conditioning. It is shown how difficult it is to form mathematical models, especially of the three-dimensional flow field occurring in practice. After basic definitions, an explanation of the influence of different air flow systems on the structure of room flow is given. The microstructure of the flowis so complex that a precise mathematical model formation seems to be impossible. Measurements on isothermal and models(reduced from the original)supply reliable three-dimensional results.

Presents results of measurements of fluctuating wind pressures on prisms of square and rectangular section mounted on the rooftop of a 4-storied building. Describes models and experimental methods. Finds pressure fluctuations of thewindward side are subject to the influence of wind turbulence. Negative pressure on leeward side is relatively stable exceptwhere strong vortices are being shed Very high negative pressures were observed intermittently along the edges of a top board.

Reports model scale experiments to investigate the validity of digital analogue methods of predicting natural ventilation. Finds calculated ventilation rates up to 30% higher than observed model ventilation rates. Shows differences between observed and computed results caused by operating efficiency of ventilation openings being less than calibrated efficiencies. Corrected ventilation rates, allowing for changes in efficiency due to pressure fluctuations and lateral air flows over model surfaces showed close agreement with observed results.