Single phase turbulent flow in a tank stirred with two different axial impellers - a pitched blade turbine
(PBT) and a Mixel TT (MTT)- has been studied using Laser Doppler Velocimetry. The effect of the
agitator configuration, i.e. up-pumping, down-pumping and reverse rotation, on the turbulent flow field,
as well as power, circulation and pumping numbers has been investigated. An agitation index for each
configuration was also determined. In the down-pumping mode, the impellers induced one circulation
loop and the upper part of the tank was poorly mixed. When up-pumping, two circulation loops are
formed, the second in the upper vessel. The PBT pumping upwards was observed to have a lower flow
number and to consume more power than when down-pumping, however the agitation index and
circulation efficiencies were notably higher. The MTT has been shown to circulate liquid more efficiently
in the up-pumping configuration than in the other two modes. Only small effects of the MTT
configuration on the power number, flow number and pumping effectiveness have been observed
