What is the function of an air dryer in a trailer's air brake system?

The function of an air dryer in a trailer's air brake system is to remove moisture and contaminants from compressed air. This is crucial because the presence of moisture in the air supply can lead to various problems, including corrosion in the air brake components, freezing in cold conditions, and reduced efficiency in brake operation. By ensuring that the air supply is dry and clean, the air dryer helps maintain the reliability and effectiveness of the braking system, contributing to overall safety and performance.

Other options involve functions that are not specific to the role of the air dryer. Increasing air pressure for braking is managed by the compressor and not the air dryer. Enhancing the braking force applied is a result of system pressure and design, not something that the air dryer contributes to directly. Controlling the temperature of brake components falls under brake system design and operation, rather than the function of the air dryer.