Recirculating

Recirculating is the practice of routing part or all of a process stream back into a system rather than discharging it, forming a loop. The purpose is to improve efficiency, control temperature, promote mixing, conserve resources, or enable reuse of signals or materials.

In piping systems, recirculation loops return water from distant outlets to the source, such as hot-water recirculation in homes. A pump or valve maintains flow to reduce wait times and stabilize temperatures. These loops incur energy and piping losses, so controls limit circulation when not needed.

Recirculating air loops in buildings move air from spaces back to the air-handling unit for treatment and redistribution. Filtration, heat exchange, and mixing with outdoor air manage comfort and indoor air quality while attempting to minimize energy use.

Recirculating aquaculture systems reuse water through filtration, disinfection, aeration, and monitoring, returning it to tanks. They reduce water use and allow precise control of water quality, but require careful management to avoid buildup of wastes and pathogens.

In chemical engineering, recirculation loops can extend residence time or enhance mixing in reactors, such as loop or back-mixed reactors.

Common considerations include energy cost, pressure losses, control complexity, and risk of contamination; design aims to balance reuse and efficiency with reliability.