air movement

In many buildings the incoming ventilation air causes recirculating airflow. Diagrams show typical examples. The incoming air stream enters below the ceiling level and carries air from the building with it causing air movement greater than th

The uncertainty of measurement results of air velocities in air-conditioned rooms generally is very high. A considerable part of the measurement errors are caused by the evaluation methods. It is shown that the accuracy of results can be ameliorated by using suitable statistical methods without increasing the effort. In this case binomial distribution gives better results thenGaussian distribution. To optimize the duration of measurements the most favorable reading interval must be determined. This time interval can be defined by the autocorrelation function of air velocity.

Reviews different lightweight structures' abilities to store heat. Shows a cutaway drawing of a single-family dwelling illustrating how stored heat is distributed. Relates heat storage capacity to structural density. Notes the importance of air distribution in attaining efficient heating.

Airflow inside air-conditioned rooms needs to be determined experimentally using test rooms. The test room dimensions vary because a test room must represent a section which is characteristic of the original room dimensions. The flow pattern is made visible; the velocities, and in some cases the gas concentration is measured. The experiments are done under thermal steady-state conditions. Some general results are:

At the HPAC laboratory of the State Research Centre, supply air tests were conducted partly with a supply air window, partly with a porous, 0. 1m thick insulation above the window. The best results were obtained with low supply air velocities allowing the air to flow down close to the outside wall. Thetests with a supply air window of about 1m*1m showed that an upward air-flow between the panes gave better results then down- flow. The air distribution was improved with a guiding vane in front of the air-flow holes in the window frame.

Examines various definitions of ventilation efficiency. When using tracer gas techniques the definition of a ventilation system's efficiency can be based on the slope of the tracer gas curve, or the ratio between concentrations, or the area under the curve. Examines the consequences of these definitions for a simple theoretical model. Presents experimental measurements on a test room which show that sometimes very low ventilation efficiency can occur.

Ventilation efficiency involves two aspects, to preserve thermal comfort, draughts should be avoided and yet one tries to obtain the best "sweeping out" which corresponds with a maximum exhaust of contaminants from the occupied zone for a given flow rate.< Reports study of 75 tests of ventilation efficiency made in a climatic roomrepresenting a heated living room. Thermal comfort was tested by measuring the air velocity both in the ventilation jet and in the occupied zone.

The local ventilation efficiency of a mechanical ventilation system may in general terms be defined as "providing air in those parts of a room where it is required". In this paper different definitions of the local ventilation efficiency and methods for measuring it are discussed. Presents results from measurements of ventilation efficiency. A test room was mechanically ventilated and nitrous oxide used as a tracer gas. A number of sensors were placed in the room with the aim of determining the variations in the air change rates within the room.

Describes a model for calculating air flow in mechanically ventilated high-rise building. Gives simplifying assumptions of model and basic equations of flow for the network of air paths. The second part of the paper gives an example of the calculation for a seventeen-storey apartment building.

Air velocities, air temperatures and dust and fluoride concentrations were measured in a burning shop of a pellet plant. The results show that there is a clear relationship between the air velocities, air temperatures and airpollution concentrations. The air flow pattern consists of an air current which rises above the burning machine as a result of convection and escapes through roof grates. Air is supplied through facade grates. The transport of air and polluting substances, especially in the cross direction of the hallindicates the influence of the wind.