In air conditioning systems, what does direct expansion entail?

Direct expansion refers to a cooling method in air conditioning systems where air is cooled directly as it passes over evaporator coils. This process occurs when refrigerant is circulated within the coils, absorbing heat from the air, which results in a reduction in temperature. The efficiency of this method lies in its ability to provide immediate cooling to the air that is circulated throughout the space, making it a common and effective approach in various cooling systems, including residential and commercial air conditioners.

In contrast, methods that involve external water sources, operate without compressors, or rely solely on fan systems do not fall under the direct expansion category. These alternatives might involve different cooling principles or technologies, but they do not utilize the direct interaction of air with evaporator coils and refrigerant for immediate cooling. This distinction highlights why option B accurately defines direct expansion in the context of air conditioning systems.