Radial flow pumps for small flows and high heads

In radial flow pumps, a diffuser/volute is generally designed at it outlet to convert the kinetic energy obtained during the pumping process to pressure head. Diffuser is characterized by widening of outlet pipes, leading to the decrease of velocity (by continuity equation) and an increase in pressure head (by Bernoulli's equation). In the case of large flows to be handled by the pumps, large velocity results in formation of significant Coriolis force that tends to deviate the outlet flow from design conditions.  

At the inlet part of the pumps, inlet size is smaller than diameter of the impeller. Thus the velocity of flow associated with a small area is comparatively large and there is less problem of separation in low flow condition. The efficiency of radial flow pumps is high when handling small flows.