What type of cooling and dehumidification system involves an evaporator coil mounted in a duct?

The correct answer is a direct expansion system. This type of cooling and dehumidification system uses an evaporator coil, which is typically mounted in a duct, to cool air as it passes over the coil. As the refrigerant inside the coil evaporates, it absorbs heat from the air, effectively reducing the air temperature and humidity levels.

In this system, the air conditioning process combines cooling and dehumidification, as the cold surface of the evaporator coil can lead to condensation of moisture from the air, thus removing humidity. This makes it ideal for both cooling and maintaining comfortable humidity levels in indoor environments.

Other types of systems, such as chiller systems, involve different mechanisms where chillers cool water that circulates to air handlers or fan coils, rather than directly interacting with the air as a direct expansion system does. Similarly, evaporative cooling systems typically use water evaporation to cool air and do not rely on refrigerants or an evaporator coil in the same way. Multiple-stage systems refer to a configuration involving stages for enhanced efficiency or capacity but are not specifically defined by having a duct-mounted evaporator coil.