Immersion chillers work by circulating a

cooling fluid A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corrosio ...

(usually tap water from a garden hose or faucet) through a copper/stainless steel coil that is placed directly in the hot wort. As the cooling fluid runs through the coil it absorbs and carries away heat until the wort has cooled to the desired temperature. Th
advantage of using a copper or stainless steel immersion chiller
is the lower risk of contamination versus other methods when used in an amateur/homebrewing environment. The clean chiller is placed directly in the still boiling wort and thus sanitized before the cooling process begins.

References

Thermodynamic systems Fluid dynamics {{thermodynamics-stub

See also

References