A water-cooled combined air dryer is a system used to remove moisture from compressed air, which is necessary for various industrial processes that require dry, clean air. The principle behind this type of dryer is that it uses a combination of cooling and adsorption to remove moisture from the compressed air.

Firstly, the compressed air is cooled to a temperature below the dew point, causing the moisture in the air to condense into liquid form. The liquid is then separated from the compressed air and drained away. This cooling process is achieved by passing the compressed air through a heat exchanger, where it is cooled by water.

Next, the cooled compressed air is passed through an adsorbent material, typically activated alumina or silica gel, which has a high affinity for moisture. The adsorbent material traps the remaining moisture in the air, leaving behind dry, clean air.

Finally, the dried compressed air is reheated to the desired temperature and released for use in industrial processes.

The water-cooled combined air dryer is an effective and efficient method of removing moisture from compressed air, and it is commonly used in industries such as food and beverage, pharmaceuticals, and electronics manufacturing.