What is pump recirculation and how do you determine minimum continuous flow?

Pump recirculation occurs at low flows when fluid recirculates within impeller passages, causing suction and discharge recirculation vortices. Suction recirculation causes pre-rotation, cavitation damage, and pressure pulsations. Discharge recirculation creates backflow at impeller discharge, reducing efficiency and causing vibrations. Minimum continuous stable flow (MCSF) is typically 25-50% of BEP flow depending on specific speed and suction energy level. Determination methods: acoustic monitoring for onset of recirculation noise, vibration analysis showing broadband increase, manufacturer's recommendations based on Ns and suction specific speed, thermal considerations (temperature rise = P(1-η)/(ṁCp)). Protection via minimum flow bypass with control valve or orifice.