A jacketed reactor, also known as a double-walled reactor, consists of an inner vessel (core) that holds the chemical reactants and a surrounding outer shell (jacket) that circulates a heating or cooling fluid. The purpose of the jacket is to regulate the temperature of the reaction inside the core vessel. The reactor itself is typically made of glass, stainless steel, or metal (depending on if the experiment is taking place in a laboratory, pilot plant, etc.) with an inner vessel that holds the reactants and an outer jacket that circulates a heat transfer fluid, such as water or oil. This set-up allows the temperature of the reactants to be controlled by regulating the temperature of the heat transfer fluid.

A jacketed reactor works by using the jacket to control the temperature of the reaction taking place inside the reactor vessel. The jacket is typically filled with a heating or cooling medium, such as water or oil, which is circulated through the jacket using a pump. By controlling the temperature of the medium in the jacket, the temperature of the reaction inside the reactor can be precisely controlled.

The jacket also provides a secondary layer of insulation around the reactor vessel, which helps to keep the reaction at a consistent temperature and prevents heat loss or gain. This is important because many chemical reactions require specific temperature ranges to proceed efficiently with a high yield. Stirring, dosing, and sampling are also critical components in the operation of jacketed lab reactors, as they help to ensure that the reactions within the reactor are efficient, effective, and safe.