air flow

Experimental methods have been developed to determine rates of air renewal. Based essentially on the use of a tracer gas, these methods permit the determination of real values on the site of the building itself. The pressurisation method which e

A benchmark study by Geomet Technologies, Inc, is developing data on the air quality effects of weatherizing a home. One effort under this study has bee nhas been an experiment carefully designed to quantify the relationships between the thr

Outlines the principles of air flow in buildings: the driving forces of wind and thermal pressure; laminar and turbulent flow; and the effects of the building geometry. Reviews the existing mathematical models of air flow and provides worked examples for a house and a multi-storey building.

A survey of mathematical models of air flow and of ventilation efficiency. Measuring equipment for laboratory experiments is described and the limitations and potential uses of the models are discussed.

Characteristics of the air velocity were measured at 500 points in the occupied zone of 20 typically ventilated spaces. A relationship between the mean velocity and the standard deviation was found at four heights above the floor. The turbulence intensity varied from 10 to 70% at ankle level (0.1 m) and from 20 to 55% at head level. This is similar to the experimental conditions under which the draught chart by Fanger and Christensen was established.

General principles of air movement around buildings are stated, indicating where windy areas are likely to occur. Case studies are then described in detail, and lessons to be learnt from these are summarised. Descriptions of wind tunnel measurements around simple model buildings are followed by accounts of the use of meteorological wind data and of the effects of wind on people. A method of predicting wind conditions around a building is developed. Some notes on wind tunnel investigations are given.

This article examines a solution procedure which can determine the flow in an air-conditioned room. The method is based on the solution of a group of equations for the flow (four non-linear partial differential equations) by means of a numerical method. Comparison with test results indicates that the method studied is suitable for prediction of air movement in an air-conditioned room when the flow is steady and two-dimensional. The method can be extended to give the required information for the evaluation of thermal comfort in the room.

Measurements reported in this paper demonstrate the increase in heat transfer due to convective air flow that can occur in wood-frame walls containing air-permeable mineral wool insulation with air spaces in contact with both sides. The effect of this air interchange between the air spaces increases with increasing temperature difference, air space height and air permeability of the insulation. Use of mid-height blocking and higher density insulation thus resulted in some reduction in the heat flow through the insulation, although convective effects were still significant.

Theoretical relationships have been developed to describe the heat transfer by combined fluid conduction-convection through air-permeable insulation with vertical air spaces adjacent to both surfaces. The fluid conduction-convection is shown to be a function of fluid properties, air flow coefficient of the insulation, insulation height and thickness, and temperature difference. A correlation in terms of dimensionless groups has been derived. Results of measurements on a 4-ft high insulation specimen over a temperature difference range from 30 to 90F were in agreement with the theory.

Effects of vertical shaft venting on smoke movement in tall buildings are examined in order to obtain conditions for minimum smoke filtration into upper floors, stairways, and elevator shafts during fires. Results show that sufficient bottom venting will nearly eliminate flow of air into shafts, while top venting reduces flow from shafts. Either should reduce smoke transfer between levels. Multiple shaft buildings benefit from top ventingsome and bottom venting others, reducing necessary vent size for sufficient ventilation.