Abstract
This paper presents the problems encountered and methodsundertaken in the design and construction of equipment formeasuring the particle size and settling velocity of flocs. Thepaper reviews existing settling columns and the development ofan experimental system suitable for such measurements. Theequipment consisted of a rectangular glass column (1.5 m high,1.5 cm deep and 3 cm wide) filled with water, into which flocs were introduced at the top and their size and settling velocitymeasured. This column was housed in a cylindrical aluminiumvessel temperature controlled by air, using a fan-forced heatexchanger which was in turn temperature controlled by a waterbath. Both the air column and all air lines were insulated. Airwas fan forced into the aluminium vessel at the top and bottomto achieve an internal temperature of 25 °C, thus eliminating any convection currents caused by temperaturevariations. The image-capturing equipment consisted of a CCDcamera, with illumination provided by a stroboscope fitted witha polarizing and a red filter to achieve optimum contrast. Allthe equipment was mounted on a heavy aluminium-skirted basefitted with 50 squash balls to eliminate any vibration causingdisturbance to the settling column and associated optics. Thesignal from the CCD camera was fed into a video recorder andanalysed by image analysis software (WiT) on a standardcomputer. The magnification range for the optical system was1300 times, capable of measuring in the range of2-240 µm. The maximum settling velocity that can bemeasured is 0.225 m s-1. The field of view was 240 µm by180 µm.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call