Refrigerated Dryers
The Refrigerated Dryers are designed for installations where pipeline temperatures are not expected to go below 35°F. These dryers cool compressed air by mechanical refrigeration, removing the moisture and assuring that none condenses downstream, unless the air is exposed to lower temperatures.
Function
Refrigeration dryers employ two heat exchangers, one for air-to-air and one for air to refrigeration. However, there is also a single 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. As of the year 2000, most manufacturers started producing energy saving dryers that do not make use of a hot-gas by pass. These dryers can save up to 40% in total energy and can consume only 10% of the max power when idle. They employ digital control and sometimes variable speed compressors. 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.
Classification
There are several types of Refrigerated Dryers exist in the global market. These are:
- Cycling Regrigerated Air Dryers
- Non-Cycling Refrigerated Air Dryers
- High Inlet Temperature Refrigerated Air Dryers
Cycling Regrigerated Air Dryers
It will increase or decrease the refrigeration compressor load depending on the compressed air demands. These dryers will help save money by reducing power consumption while constantly providing consistent dew points.
Non-Cycling Refrigerated Air Dryers
These are extremely reliable. Non-Cycling dryers can be sized for any application, and will always provide consistent dew points. They also have very low maintenance costs.
High Inlet Temperature Refrigerated Air Dryers
These are used in situations where extra refrigeration is needed to remove any water vapor from the air. These dryers are very similar to the non-cycling dryers, but they are oversized to ensure consistent dew points.
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