The phenomenon of slip is known to strongly influence the performance of centrifugal pumps. In the present work, the slip phenomenon at the impeller outlet is studied experimentally for five industrial pumps at different flow rates and the slip factor is estimated for each of these cases. Theoretical slip factors are calculated using several existing methods taking into consideration the main geometric parameters of the impeller. Then the experimental slip factors are compared with the calculated theoret_ical values. It was observed that in the design-point condition of the pumps, the experimental values are in a good agreement with the theoretical values. However, there are significant disagreements between the theo_retical and experimental values at off-design regiments. The difference is more apparent at low flow rates. It is also found that the slip factor depends on the impeller-outlet velocity profile. By defining a flow distortion coefficient, a correlation is derived for evaluating the slip-factor value for off-design conditions. Finally, a slip factor table is provided to calculate the slip factor in centrifugal pumps, using the geom_etry of impeller.
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