What is the name of a refrigeration system that has its entire charge contained in the evaporator?

The correct answer is based on the concept of a critically charged system, which refers to a specific configuration in a refrigeration system where the refrigerant charge is entirely contained within the evaporator. This means that the evaporator is responsible for both absorbing heat and circulating refrigerant through the system without needing additional components, such as a separate condenser or compressor handling the refrigerant charge outside of it.

In this arrangement, the system is designed to operate efficiently by optimizing the use of refrigerant and maximizing heat transfer performance in the evaporator itself.

Other types mentioned, such as indirect systems, involve a secondary medium for heat transfer and do not have the entire refrigerant charge within the evaporator. Direct expansion systems, while they also operate by allowing refrigerant to expand within the evaporator, do not specifically imply that the whole charge is contained solely there. Closed loop systems refer more broadly to any system where the refrigerant circulates continuously within a closed loop, without necessarily indicating that the entire charge is held in the evaporator.