Correlation of Discharge Flow Rate in a Vessel with Pitched Blade Paddle Impeller

Abstract

The discharge flow rate Q_d for both paddle impeller and pitched blade paddle impeller were measured with the flow follower method. The discharge flow rate number obtained for the paddle impeller Nq_d was correlated with the power number Np and the impeller dimensions, based on the correlation form derived from the angular momentum balance between the impeller tip and the vessel wall. The correlation of Nq_d obtained for the paddle impeller was modified with the blade angle θ to give the correlation of Nq_d for the pitched blade paddle impeller. The resultant correlations were

(Nq_d)_NB = 0.14(D/d)^1/2β[(D²H/d³)Np]^1/2(3.3γn_p^0.7bsin^1.6θ/H)^θ/π

for γn_p^0.7bsin^1.6θ/H < 0.3

= 0.14(D/d)^1/2β[(D²H/d³)Np]^1/2

for γn_p^0.7bsin^1.6θ/H > 0.3

for a non-baffled vessel and

(Nq_d)_B = 0.25(n_p^0.7b/d)^–1/4β[(D²H/d³)Np]^1/2(2.5γn_p^0.7bsin^1.6θ/H)^θ/π

for a baffled vessel, respectively. These correlations reproduced not only the present experimental results but also the results measured by other investigators within ±30% experimental error.