Refrigerated Compressed Air Dryer / Refrigerant Air Dryer

It can change low-pressure gas to high-pressure gas. So, it is the heart of the refrigeration system. Firstly, it sucks low-temperature and low-pressure refrigerant gas. Secondly, drive the piston to compress the gas. Finally, discharge the high temperature and pressure refrigerant gas. In short, it powers the refrigeration cycle. The workflow is as follows: compression→condensation→expansion→evaporation.

The condenser cools refrigerant vapor into liquid refrigerant. In addition, it is available in both air-cooled and water-cooled. Therefore, our refrigerant air dryer also includes air-cooled and water-cooled. Among them, the former is a fin structure. It’s similar to the home air conditioner. And the latter is a shell-and-tube structure.

The air condenser does not require cooling water. Thus, it is suitable for applications in areas without water supply. But its cooling effect is a bit worse than water. Therefore, its volume is larger than that of a water condenser of the same specification. Generally, it is only suitable for medium and small refrigerated air dryers. For example, our air-cooled refrigeration dryer can be up to 120m³/min. If it exceeds 120m³/min, only use the water-cooled dryer.

On the contrary, the water condenser adopts high-efficiency heat exchange tubes. So it has high heat exchange efficiency. Compared to ordinary heat exchangers, their performance increases by more than 30%. Therefore, it can ensure long-term efficient and stable operation.

Our refrigerator air dryer is with automatic cooling water adjustment system. So it can stabilize the cooling water volume automatically. Therefore, it can guarantee a stable outlet dew point. At the same time, it can effectively prevent the evaporator from freezing.

The evaporator is the main heat exchange part of the refrigeration air dryer. Its structure is different from that of the pre-heat exchanger. It comprises a shell, red copper tubes, and aluminum foil fins.

Compressed air flows up and down the shell along the baffles in the evaporator. And the refrigerant flows in the tube. So the compressed air is forced to cool. Most water vapor condenses into a liquid state. Eventually, they are discharged out of the dryer. Thereby, it dries the compressed air.

It is not an essential part of refrigerant type air dryers. But it plays a big role during operations. Its main function is to “recover” the cold energy in the evaporator. And use them to cool the temperature initially. Thus, it can reduce the load of the refrigeration system. Finally, it achieves the purpose of saving energy.

On the other hand, it can heat up low-temperature compressed air. Therefore, it can avoid the phenomenon of dew on the exhaust pipe. Because the temperature is too low, dewdrops will form.

The pre-cooler is also for initial cooling. Therefore, it also reduces the load on the refrigerant compressor. Some cheap refrigeration air dryers don’t have a pre-cooler. They are only normal temperature types. Therefore, it cannot be used under harsh working conditions. Especially in high-temperature areas such as the Middle East.

With a pre-cooler, the max inlet air temperature can reach 80 ℃. So this kind of refrigerated air dryer has a wider range of applications.

It mainly contains a capillary tube and an expansion valve. They enable regulation of the supply of refrigerant. When the load changes, the expansion valve can sense the superheat of refrigerant vapor. So it can adjust the valve opening size. Finally, it can control the flow of liquid refrigerant into the evaporator. The capillary structure is simple. Therefore, it is widely used in small refrigeration dryers.

The compressed air is cooled in the evaporator. There will generate a lot of condensation. If the evaporation temperature is too low, the water will freeze. In severe cases, it will block the airflow passage. Eventually, it will paralyze the air supply line. To prevent this, we must control the evaporation temperature. So we can add a hot gas bypass valve between the condenser and the evaporator.

When the evaporation pressure is low enough, the valve opens. The high temp refrigerant vapor enters the evaporator. Therefore, it can increase the evaporation temperature. Finally, it can avoid ice blockage of refrigerated air dryers.

There may be water and solid impurities in the refrigerant. So it will block the throttling device. At the same time, moisture is very harmful to the refrigeration system. So it must install a dry filter before the refrigerant supply pipe.

This is one of the key parts of a refrigerant air dryer. The evaporator cools the hot and humid compressed air. At this time, a large amount of condensed water will be precipitated. This requires the separation of compressed air and condensate. Therefore, the device can achieve true drying purposes.

The refrigerants of our refrigerated air dryer are the following types, such as R22, R410a, R407c, and R134a.

Sometimes users need compressed air with low outlet temperature. Currently, the refrigerant air dryer doesn’t need a heat exchanger. So the cooling energy of the cold air cannot be recycled. Then the evaporator heat load will increase a lot.

Finally, the power of the refrigerant compressor needs to be larger. This is to perform energy compensation. At the same time, it also needs to recalculate other refrigeration components.

For example, our 10~50AC refrigeration air dryer. If the same cooling capacity, the dew point will be slightly worse.

The following three conditions limit the “pressure dew point” of the refrigeration air dryer:

① Firstly, the bottom line of the freezing point of evaporation temperature;

② Secondly, the heat exchange area of the evaporator can’t increase indefinitely;

③ Thirdly, the separation efficiency of the “air-water separator” can’t reach 100%;

It is normal for the final cooling temperature of the compressed air in the evaporator to be 3~5°C higher than the evaporating temperature of the refrigerant. Besides, lowering the evaporation temperature too much will also not help.

In addition, the efficiency of the air-water separator is also limited. It only reaches 99%. Therefore, there is still a minimal amount of condensed water. Eventually, they will evaporate into water vapor.

In summary, it is tough to control the “pressure dew point” of refrigerated air dryers below 2°C.

The pressure dew point of most refrigerant air dryer manufacturers is 2~10℃. Under good operating conditions, it can be lower. For example, it can reach 3~5℃.

In refrigeration air dryers, the evaporating temperature can’t substitute for “pressure dew point.” Because the heat exchange area of the evaporator is limited. Besides, there is a certain temperature difference during the heat exchange process. Sometimes it reaches 4~6℃. So refrigerant evaporation temperature is always lower than the pressure dew point.

The heat transfer effect of the water-cooled refrigerated air dryer is better than that of the air-cooled type. But it will consume a lot of water. Besides, it has the following requirements for water quality:

① Firstly, the water entering the refrigerant air dryer should be below 31°C. Moreover, the water outlet temperature should not exceed 36℃;

② Secondly, the water pressure should be kept above 0.15MPa. To protect the flow of water. Of course not too high;

③ Thirdly, magnesium and calcium ions should not be higher than the general standard of neutral soft water;

④ Finally, there should be no visible solid debris in the water.

We always hope that the higher the exhaust temperature, the better. It is best to be the same as the intake air temperature. At this time, the “waste cooling” is zero.

But in practice, this is not achieved. It is normal for the temperature difference of the refrigerant air dryer to be 15°C. If you have other questions, contact us. As a refrigerated air dryer manufacturer, we can give your professional answers.