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Document ID (ISN)38666
CIS number 82-1896
Year 1981
Convention or series no.
Health and Safety Laboratories
Title The design of local exhaust ventilation hoods and slots
Bibliographic information Technical Information Leaflet, Environmental Contaminants 11, Enquiry Point, Health and Safety Executive, Baynards House, 1 Chepstow Place, London W2 4TF, United Kingdom, 1981. 2p. Illus. 5 ref. Price: ú0.15.
Abstract Hoods of 9 different aspect ratios between 1:1 and 16:1, with <6 different areas at a given aspect ratio were examined at Health and Safety Laboratories. Air was drawn into the hoods by a centrifugal fan; volume flow rate was regulated by a valve and measured by means of an orifice plate. Average face velocities in the range 2.30m/s were produced. Velocities along the centreline were measured with a constant-temperature hot-wire anemometer. Velocities across the hood face were found to be uniform except close to the hood edges. Centreline velocity is strongly dependent on aspect ratio, which means that the design formulae of Dallavalle (1930) and Silverman (1942) previously used to predict centreline velocities are not valid in general. The velocity induced by suction fell very rapidly with increasing distance from the hood; correct siting of the hood is therefore important if the system is to be effective. Effects of flanges are also considered.
Descriptors (primary) exhaust hoods; ventilation design; aerodynamics; local exhaust
Descriptors (secondary) velocity of flow; toxic gases; mists; applied research; airflow measurement; atmospheric pollution; exhaust ventilation
Document type E - Books, reports, proceedings
Subject(s) Heating, ventilation and climate
Broad subject area(s)
Browse category(ies) Ventilation