The physical reason for draughts is in the first place the convective surface-heat-transfer coefficient. To find out about the influence of turbulence on draughts, it is necessary to carry out measurements of the surface-heat-transfer coefficient in relation to air turbulence. The results of first measurements of this kind are the subject of this paper.
Describes measurements made in a real factory building and comparisons with the scale model tests presented in the previous report. The ventilation system of the factory building is a mechanical one with the necessary rate of ventilation designed to be less than that calculated by the conventional method. The parameters studied included air velocities measured with hotwire anemometers at the inlet openings and the temperatures in the work hall itself measured from a crane.
Shows the results of a study of the effects of turbulence upon ventilation. Controlled fluctuating air flows were directed upon openings in the side of acube simulating a building. The relationship between the turbulent characteristics of the air flow and the ventilation rate in the building modeare examined. Mean windspeed and the turbulent velocity and intensity of the air flow were measured with a thermocoupled anemometer. Resulting ventilation rates were measured by means of tracer gas decay, using CO2 as the tracer and an infra red analyser to monitor the decrease in concentration.
Reviews current methods of ventilation measurement in occupied buildings including tracer methods, pressurisation, and thermography. Gives criteria for good ventilation rate measurement techniques. Also explores new methods of measuring ventilation rates in occupied buildings. These include:< 1. Use of non-toxic tracers, including negative ions, CO2 and odour levels< 2. AC pressurisation< 3. The quantification of thermography< 4. Small-scale detection of local air velocities using hot-wire anemometry.
Discusses difficulties inherent in multiplexity of full-scale trials and the use of EDP simulation in models. Considers the measurement of low air movement velocities using different types of anemometers and field trials in lecture rooms and open-plan offices. Reports on studies into ventilation efficiency and full scale trials. Reviews International Institute of Refrigeration Congress held in Essen September 1981.
An anemometer which was developed for indoor climate research has been modified in order to get the same shape of calibration curve for each anemometer. Experiments in a wind tunnel showed that this was the case for more than 80% of a test series of the modified anemometers. The time constant has increased but is still acceptable. Calibration curves and time constants could be predicted by calculation with reasonable accuracy. Some influence of dust particles on the instrument was noticed.
Describes the development of an anemometer for the measurement of rapidly fluctuating air flows. Describes the B.R.E. shielded hot wire anemometer. Discusses modifications made to this anemometer to improve its response by using different shields and moving sensor wires closer together. Outlines system for processing signals from the anemometer using a micro-computer. Gives results of performance tests. Gives simple applications of theinstrument.
Describes apparatus used to measure full-scale wind loads on a glasshouse. Wind pressure was sensed by a Dines anemometer and the variation in wind velocity with height by a small pressure tube anemometer. Wind loads on the glasshouse were sensed by pressure tapping points connected in sequence to micromanometers. Describes apparatus for the recording and analysis of data. States apparatus has been used for two years and found to be reliable in operation.
Describes a dynamic pressure anemometer which belongs to the group of pressure-tube anemometers (pitot-static tubes) and is intended for measurement of one velocity component in a three dimensional flow field at air velocities of 0.1 to 10 m/s. The usable flow direction is unlimited (0...360 deg.) in three dimensions. The maximum error in the indication of the velocity component is less than 5% (if the actual velocity is put at 100%).
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