Refrigerated Air Dryers: Working Principle Overview

Refrigerated air dryers are vital devices used to remove moisture from compressed air, which can otherwise cause corrosion and damage to pneumatic tools. They ensure the efficiency of compressed air systems by providing dry air. Refrigerated dryers work based on the properties of air and water vapor.

There are specific stages in the process of removing moisture from the air. 

1. Compression: Air is compressed, raising its pressure and temperature. This increased pressure and temperature allows the air to hold more moisture, resulting in higher humidity levels.
   
   
2. Cooling: The hot and moist compressed air is passed through a heat exchanger and cooled down. This cooling process causes the water vapor in the air to condense into liquid water, separating it from the compressed air.
   
   
3. Separation: The condensed water droplets are separated from the air stream and collected in a drainage system. Various methods, such as centrifugal separation or moisture traps, can be used for this separation process.
   
   
4. Drying: The cooled and dehumidified air is then reheated to a temperature similar to the initial compressed air inlet temperature before exiting the dryer. This reheating prevents the formation of new condensation as the air travels through the distribution system. In addition, it is precooling the inlet air to save energy of the Air to Refrigerant heat exchanger. 

Refrigerated air dryers are commonly used in industries and businesses because they are dependable and efficient. They help to create and maintain the quality of compressed air. Hankison provides different refrigerated air dryer versions, such as the Flex Series and HDS Series models. These models come with two energy-saving technologies.

Flex Series Technology

The Flex Series refrigerated air dryers work efficiently by using a special material called Phase Change Material (PCM). This material changes between solid and liquid states to remove moisture from compressed air while using very little energy, especially when it’s not very hot ambient conditions or when the air compressor is not working at full capacity.

Here’s how it works: when the refrigeration compressor and condenser fan are running, they cool down the liquid PCM, turning it into a solid. Once the PCM is solid, the compressor and fan stop working.

Even when they’re off, the solid PCM continues to cool the compressed air without using any power. The air also goes through a refrigeration chiller, where any the remaining moisture is condensed and removed. After that, the cold and dry air is warmed up a bit by incoming warm compressed air.

One smart feature of the Flex Series dryers is, that they use cold outgoing air to cool down the incoming air before it reaches the chiller. This reduces the work the refrigerant compressor has to do. This cooling process also gets rid of a lot of the moisture in the incoming air before it even reaches the chiller, making the system even more efficient.

When designing these dryers, worst-case scenarios like really hot weather and full workloads are considered. This ensures the dryers work their best even in tough conditions.

HDS Series Technology

HDS air dryers use advanced digital scroll compressor technology to operate efficiently. This technology adjusts the amount of refrigerant needed by controlling how consistently fast the refrigerant is compressed. This precise control matches the energy used for compression to the amount of compressed air being processed, making it energy-efficient.

Here’s how it works: first, warm and moist compressed air enters the dryer. The incoming air is cooled down by exchanging heat with the cold air leaving the dryer. Then, the air is further cooled by evaporating the refrigerant. A system inside separates water, oil, and particles from the compressed air.

Any water formed during this process is drained out, and the air is warmed up again inside the heat exchanger. When the compressed air leaves the dryer, it’s both dry and warm, about 8°C cooler than when it entered.

The refrigeration system works in a sealed manner. It takes in the evaporated refrigerant, compresses it to a higher pressure, and then liquefies it in the refrigerant condenser. The liquid refrigerant’s pressure is reduced and injected into the refrigerant/air-heat exchanger.

This detailed process ensures the effective removal of moisture, resulting in high-quality compressed air.

When to Use Refrigerated Air Dryers

Both these methods are crucial in situations where it’s vital to stop liquid water from forming in compressed air below 6°C pressure dew point within a pressure range of 4 to 13 bar. They are indispensable when saving energy, using pneumatic tools on and off, ensuring reliability, and handling varying compressor loads are important factors to consider.