The difference between a refrigerated air dryer and a desiccant air dryer

Differences between Refrigerated Air Dryers and Desiccant Dryers:

1. Working Principle: Refrigerated air dryers operate on the principle of refrigeration dehumidification. Through heat exchange with the refrigerant, the saturated compressed air upstream is cooled to a specific dew point temperature. Simultaneously, a large amount of liquid water is condensed and separated by a gas-liquid separator, then automatically discharged from the machine, achieving dehydration and drying. Desiccant dryers operate on the principle of pressure swing adsorption. The saturated compressed air upstream comes into contact with a desiccant under a certain pressure, adsorbing most of the moisture from the desiccant. The dried air then enters the downstream working area for deep drying.

2. Dehydration Effect: Refrigerated air dryers are limited by their inherent operating principle. If the temperature is too low, the machine will freeze and become clogged. Therefore, the dew point temperature of the machine is typically maintained between 2-10℃. Desiccant dryers do not require heat exchange through temperature changes. The desiccant inside the machine can achieve deep drying, and the outlet dew point temperature can reach below -20℃.

3. Energy Consumption: Refrigerated air dryers achieve cooling through refrigerant compression, thus requiring higher power supplies. Desiccant dryers only require valve control via an electrical control box, resulting in lower power consumption and less power loss compared to refrigerated air dryers.

4. Air Volume Loss: Refrigerated dryers remove moisture by changing the temperature, and the moisture generated during operation is discharged through an automatic drain pipe, thus there is no loss of air volume. In contrast, desiccant dryers require regeneration of the desiccant after saturation, resulting in a regeneration gas loss of approximately 12-15%. Refrigerated dryers have three main systems: refrigerant, air, and electrical. These systems are relatively complex and have a higher probability of failure. Desiccant dryers only malfunction when valves are frequently activated. Therefore, generally speaking, refrigerated dryers have a higher failure rate than desiccant dryers.

Advantages and disadvantages of refrigerated air dryers:

Advantages:

1. No compressed air consumption: Most users do not have high requirements for the dew point of compressed air. Compared with desiccant dryers, refrigerated air dryers can save more energy.

2. Simple daily maintenance: As long as the automatic drain filter is cleaned regularly, valve wear will not occur.

3. Low operating noise: The operating noise of refrigerated air dryers is usually inaudible in the air compressor room.

4. Relatively low solid impurity content in the exhaust of refrigerated air dryers: The operating noise of refrigerated air dryers is usually inaudible in the air compressor room.

5. Dehydration effect: The effective air supply of refrigerated air dryers can reach 100%, but due to the limitations of its working principle, the lowest dew point of the supplied air can only reach about 3°C. For every 5°C increase in inlet air temperature, the refrigeration efficiency will decrease by 30%, and the dew point of the supplied air will also increase significantly. This is largely affected by the ambient temperature.

Advantages and disadvantages of desiccant dryers:

Advantages:

Compressed air dew point can reach -70℃

Unaffected by ambient temperature

High filtration efficiency, removes many impurities

Dehydration effect:

It consumes more energy than refrigerated dryers due to the use of compressed air

Requires regular addition and replacement of adsorbent; Valve components wear out, requiring routine maintenance

Desiccant dryers generate noise from the pressure release of the adsorption tower, with an operating noise level of approximately 65 decibels.