INFLUENCE OF LOAD AND STIRRER TYPE ON CURRENT,

Abstract

A mixer was designed and constructed on angle iron frame 450 x400x 950 mm (LxWxH), with  a spiral(A) and non spiral stirrer(B) 350x10.5mm(LxØ) as impeller and  powered by a 2.7kw generating set through 0.374 kw(0.5Hp) a single phase  electric motor with variable speed control .The mixer was  run on equal mass of flour, sand, garri, water and air as load at 5 different loading speeds at one instant ,then the speed kept constant and evaluated on 1 to 5 kg of sand. The revolution per minute /temperature attained in the motor and current developed per each sample were measured by a tachometer, analogue temperature sensor and 266 clamp ammeters. The data on load were regressed against rpm, while a bill of quantity performed on the mixer Result show that the mixer is capable of mixing the materials at various speeds (rpm) of 1280, 1212, 1140, 1035 and 945 for stirrer A and 1302, 1211, 1152, 1046 and 961 for stirrer B, as the load increased from 1-5kg for water /flour mixture. An estimated speed of 1275 rpm for 5kg flour at temperature of 41.4⁰c and current of 11.12amp was recorded. Regression analysis showed a deceleration of -0.966 between loads and speed (rpm) and indicated that for every increase by 1 kg of load, speed (rpm) reduces by 84.5 and 85.5 for A and B stirrers, which fits the linear model. Economically, small scale processor can afford to run these mixers which was estimated to cost twenty eight thousand naira (N28,000) or $150 equivalent.