Rheometer(redirected from Extensional rheometer)
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an instrument for measuring the flow of a viscous fluid. In the USSR, the term is applied to a type of rate-of-flow meter that measures the volume flow of a gas. The operation of such a rheometer is based on the measurement of the pressure drop across a constriction in the pipe through which the gas flows; the constriction may be in the form of an orifice or capillary tube. The pressure drop is a single-valued function of the flow rate of the gas and is measured by a differential manometer, whose scale is generally marked in units of gas flow, such as cm3/min or liters per hour (l/hr). Such rheometers are used for measuring flow rates of up to 104l/hr in industrial and laboratory installations. For example, they are used in equipment for the chlorination of water and in devices for the quantitative analysis of the composition of gases.