What type of system involves the removal of heat using a secondary medium?

The correct choice, the indirect refrigeration system, is a method where heat is removed from the space or substance being cooled by first transferring that heat to a secondary fluid or medium. This secondary medium can be another liquid, often referred to as a refrigerant, which absorbs the heat and carries it away from the area that needs to be cooled.

In an indirect refrigeration system, the secondary fluid then releases the absorbed heat in a location away from the cooling area, typically in a condenser unit. This allows for effective heat removal without directly exposing the system that requires cooling to the refrigerant's properties, enhancing safety and efficiency. The use of a secondary medium enables better control over temperature regulation and the capacity to move heat over longer distances.

In contrast, direct cooling systems do not use a secondary medium; instead, they cool the space or substance directly without an intervening fluid. Automatic control systems refer to mechanisms for regulating temperature or pressure, rather than directly describing the heat removal process. Thermal storage systems involve storing cold or hot energy for later use, but they don't inherently specify the use of a secondary medium for cooling.