Slurry flowmetering using correlation techniques

Doctoral Thesis


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University of Cape Town

A review of slurry flowmeters leads to the conclusion that most are unsuited for measuring the flowrate of abrasive and corrosive slurries such as are found in the gold mining industry in South Africa. An alternative flowmeter based on cross-correlation techniques is thus proposed. Random signals generated by the flowing fluid are measured at two points a known distance apart in the direction of the flow. Assuming that this distance is not "too" large, the downstream signal is a time-delayed replica of the upstream signal. This delay equals the time it takes flow discontinuities to travel between the two measuring locations and can be obtained by cross-correlating the two flow signals and finding the position of the correlation peak. An analysis to establish a theoretical-basis for the method is performed and an attempt is made to model the flowmeter consisting of the two transducers a known distance apart. A review of transducers for converting time-varying spatial flow patterns into electrical signals is undertaken and leads to ultrasonic transducers being chosen as most suitable for slurry flowrate measurements. Such transducers are non-intrusive and can be of a clamp-on type. The characteristics and requirements of ultrasonic transducers for correlation flowmetering are investigated and a suitable clamp-on design is described.

Bibliography: leaves 235-256.