What is the difference between a direct expansion system and a chilled water system?

A direct expansion system and a chilled water system are two distinct types of refrigeration and air conditioning systems, and understanding their differences is crucial in the field of refrigeration technology.

A direct expansion (DX) system uses refrigerant, which evaporates in the evaporator coils as it absorbs heat from the air, effectively cooling the space. The cooling effect is produced directly as the refrigerant expands and changes states within the coil. Consequently, the mental image is that air is cooled directly by the refrigerant itself without the intermediary step of using water.

In contrast, a chilled water system operates by circulating chilled water through coils that absorb heat from the air. This chilled water is produced by a chiller, where refrigerant is used to lower the temperature of water before it's delivered to the air handling units. In this scenario, water serves as the medium to transfer heat from the air, making it an effective way to cool larger spaces or buildings.

The correct answer includes the information that a chilled water system uses water to transfer heat, which aligns with its operational principle. It also acknowledges that a direct expansion system does not use water to circulate and cool air, thereby distinguishing these two systems clearly. By identifying that both B and C are accurate statements about these systems, the