The use of refrigeration drying for compressed air treatment is tested and proven for many industrial applications. Dewpoints of 1.7°C to 10°C are suitable for many indoor applications where a general removal of bulk water and some vapour is sufficient for the application process.
Refrigeration dryers can be used at low pressures as well as high pressures and use no processed compressed air during the air treatment. Proper sizing factors must be used to determine the correct sized dryer for the application based on actual (or worst-case) flow, operating temperature and operating pressure.
Energy prices are a rising concern and a major cost to manufacturing facilities. Therefore, the refrigeration dryer has undergone many improvements to make them more energy efficient without sacrificing the quality of the air provided.
Refrigeration dryers use a set of heat exchangers or a single heat exchanger (with chambers) first to pre-cool the air; second, to refrigerate the air to condense out moisture vapour; and last, to re-heat the air to prevent pipe sweating downstream. Direct expansion dryers are a type of dryer where the compressed air and the refrigerant come into direct contact via the heat exchanger. While reliable and simple to use, they generally require that the unit continue to run regardless of actual compressed air flow through the dryer. Cycling dryers utilise a thermal mass as the means to absorb the heat from the compressed air. By chilling a thermal mass, a refrigerant compressor may turn off in times of low demand thereby saving energy by shutting off the refrigerant compressor. There is however, an additional heat transfer (the thermal mass), so a small amount of additional cost may or may not offset the amount of money saved by shutting off the compressor.
The use of refrigeration dryers is preferred:
