Method and meter for the measurement of gas flux in short closed ducts of large cross section area, particularly in boiler air/flue gas and ventilation circuits

摘要

The method according to the invention consists in that the velocity profile in a flow duct is normalised to a flat profile of average velocity value and that in any chosen point of the known flow area the value of the average velocity is measured by means of a point velocity meter, e.g. a Prandtl tube or a thermoanemometer. The gas flux meter according to the invention is characterised in that it is installed in a short closed duct 1 of rectangular cross section. The normaliser 2 of the flowmeter comprises two reflectively symmetrical walls integrated into the rectangular duct 1 . These walls form a constriction in duct 1 , that constriction having the shape of a convergent section 3 gradually changing along its length into a duct of only slightly variable cross section 4 and finally into a divergent section 5 , said walls being confined by two planar walls 10 of the duct. In one of the planar walls 10 a stub 6 is installed with a position locking means 7 for securing in its operating position a movable point sensor of gas flowmeter 8 , e.g. a Prandtl tube or a thermoanemometer, coupled via a signal conveying means to a flow transducer 9 . The gas flux meter may also be used in a short pipe of circular cross section upon installing inside the pipe an axially symmetrical venturi - gas velocity normaliser.