Complex sentence: This occurs due to a decrease in the concentration change due to the smaller fraction of the flow determined by the feed; in the limiting case of total recycling, infinite recycle ratio, the PFR perfectly mimics a CSTR.
Split into simpler sentences: This occurs due to a decrease in the concentration change due to the smaller fraction of the flow determined by the feed. Hence at total recycling, infinite recycle ratio, the PRF perfectly mimics the modelling of a CSTR.