Air Dryers

Air dryers Design:

A compressed air dryers is a device for removing water vapor from compressed air. Compressed air dryers are commonly found in a wide range of industrial and commercial facilities.

The process of air compression concentrates atmospheric contaminants, including water vapor. This raises the dew point of the compressed air relative to free atmospheric air and leads to condensation within pipes as the compressed air cools downstream of the compressor.

 Excessive water in compressed air, in either the liquid or vapor phase, can cause a variety of operational problems for users of compressed air. These include freezing of outdoor air lines, corrosion in piping and equipment, malfunctioning of pneumatic process control instruments, fouling of processes and products, and more.

There are various types of compressed air dryers. Their performance characteristics are typically defined by the dew point. Regenerative desiccant dryers, often called “regens” or “twin tower” dryers Refrigerated dryers Deliquescent dryers Membrane dryers

Water vapor is removed from compressed air to prevent condensation from occurring and to prevent moisture from interfering in sensitive industrial processes.

Refrigeration Air Dryers:

Refrigeration dryers employ two heat exchanger, one for air-to-air and one for air-to-refrigeration. However, there is also a single TRISAB heat exchanger that combines both functions. The compressors used in this type of dryer are usually of the hermetic type and the most common gas used is R-134a. The goal of having two heat exchangers is that the cold outgoing air cools down the hot incoming air and reduces the size of compressor required. At the same time the increase in the temperature of outgoing air prevents re-condensation.

Most manufacturers produce “cycling dryers”. These store a cold mass that cools the air when the compressor is OFF. When the refrigeration compressor runs, the large mass takes much longer to cool, so the compressor runs longer, and stays OFF longer. These units operate at lower dew points, typically in the 35–40 °F range. When selected with the optional “cold coalescing filter”, these units can deliver compressed air with lower dew points.

Some manufacturers are marketing compressors with built-in refrigeration dryers, but these have had a mixed acceptance in the market.

Commonly a coalesing prefilter is installed immediately upstream of a refrigerated dryer to remove lubricating oil and other contaminants that have the potential to foul the dryer’s heat exchangers