Final answer:
An air dryer is installed in an air brake system to remove moisture and contaminants, usually placed between the air compressor and the first air tank to prevent brake issues such as freezing or overheating.
Step-by-step explanation:
An air dryer is typically installed in an air brake system to remove moisture and contaminants from the compressed air before it reaches the brake lines. Moisture in the system can lead to a range of issues, such as frozen brake lines in cold weather, which could result in brake failure. To maintain the efficiency and proper operation of the brakes, the air dryer is usually placed between the air compressor and the first air tank, where it can effectively treat the air before it circulates through the rest of the system. The air dryer works to ensure that the braking system performs reliably by producing dry air, thus preventing brake problems like the overheating seen in Figure 14.5, which illustrates the mechanical equivalent of heat via smoking brakes.