How refrigerated air dryer works - refrigerant dryer working principle

Writer： admin Time：2022-09-21 00:00:00 Browse：288℃

How refrigerated air dryer works? In fact, air compressor refrigerant dryer working principle is simple. Refrigeration dryer uses the compressor cooling function. Use the heat exchange of refrigerant and compressed air. And reduce the pressure dew point to 2~10℃. So the water content tends to to a supersaturated state. Finally reach the purpose of removing moisture.

What is refrigerated air dryer?

Refrigeration dryer is an important compressed air treatment equipment. It belongs to air purification machine in pneumatic system. When the temperature drops, the gaseous moisture will turn into liquid state. The refrigerant dryer rightly uses this working principle. The compressed air flows into the evaporator. Here it is cooled by heat exchange. At the same time, it will cool the water and oil in the gaseous state. They are condensed into liquid form. Finally automatic drain exhaust them out of dryer system. So we obtain clean compressed air.

Why we need refrigerant air dryer?

Many people think that only the food and pharmaceutical industry need dry and clean air. In fact, this is not right. Most industrial industries require the treatment of compressed air. Otherwise, there will be a lot of moisture in it.

The air contains various gases and water vapor. Basically it’s moist air. When compressing air, the water vapor will be condensed into water by pressure. Excessive water molecules can travel with the compressed air in the pipes. It will seriously affect the normal operation of the equipment. Also corrode our machineries. Bring damages to pneumatic components, etc.

In winter, liquid water freezes into ice once the temperature drops below zero. As a result, the compressed air pipeline is blocked by ice. These will seriously affect our production activities. So we need refrigeration dryer to remove water.

Types of air compressor refrigerant air dryer

In fact, there are many types of refrigeration air dryers. For example, it can be divided into normal temperature and high temperature air dryer. Also includes atmospheric pressure and high pressure refrigerant dryer. In addition, it also composes of conventional and explosion-proof refrigerated dryer. Below we mainly distinguish the refrigerant dryer from the working principle and energy saving.

(1) Air-cooled and water-cooled air dryer

Generally, small air dryers are air-cooled. If it exceeds 120m³/min, it is best to use the water-cooled refrigeration dryer. Which of the two is better? They have different condenser cooling methods. The function of the condenser is to cool the vapor refrigerant into a liquid refrigerant.

The air-cooling dryer uses a finned condenser. This is similar to an air conditioner outdoor unit. It does not require cooling water. So it’s suitable for places where the water source is not sufficient. Because of the heat exchange with the air, it is greatly affected by the ambient temperature. Especially in summer, the dryer load will be relatively large. Compressed air quality will have an impact. The dryer installation location needs good ventilation.

But the structure and working principle of water-cooling refrigerant dryer is different. It uses a shell and tube condenser. High temperature refrigerant vapor flows through the shell. Heat exchange with cooling water. The refrigerant vapor releases heat and condenses into a liquid state. Finally, it flows out from under the condenser. The working condition is relatively stable. Not affected by high temperature environment. So the dew point is stable. Of course, there needs a cooling water system. That is, cooling water pump, cooling tower and water. The initial investment is relatively large.

(2) Non-cycling and cycling refrigerated air dryer

In fact, common refrigeration dryers are generally non-cycling type. It means continuous operation with power consumption near full load. But cycling type air dryer is different. It is also called a cold energy storage type refrigeration dryer. How does cycling refrigerated air dryer work?

In cycling refrierant air dryer, there is a water accumulator. Its drain port connects the condenser through piping. This directs the stored condensate to the condenser. Thereby cooling the refrigerant in the dryer condenser. At the same time, use the liquid temperature controller to control the start and stop of the refrigerant compressor. Therefore, it can adapt to load changes to achieve the purpose of energy saving.

The operation time of the refrigerant compressor only accounts for a part. The thermal efficiency of a good cycling air dryer is up to 87%. The temperature difference of refrigerant dryer is only 2%. Compared with non-cycling air dryer, it can save about 40% of the annual electricity bill.

How does refrigerated air dryer work?

Different refrigerant dryers have a bit differences in working principles. But basically they are the same. Next, we mainly introduce the working principle of the non-cycling refrigerant dryer.

(1) Working principle of air-cooled refrigerant dryer

The working process of the refrigeration dryer includes two parts. We use red and blue color to represent in the image above. They represent heat exchange system and refrigeration system respectively.

Heat exchange system of refrigerated dryer:

① The air compressor exhaust compressed air. At this time, they are still high in temperature and moisture content. We need to cool them down. Firstly, they enter the precooler from the inlet. Here, it can cool down and remove water to a certain extent.

② Secondly, the air enter the evaporator below. They circulates outside the heat exchange tube. And the low-temperature refrigerant flows inside the heat pipe. There is heat exchange between them. Thereby reducing the air temperature. It will reach to the dew point temperature. At the same time, most of the water vapor will condense into a liquid.

③ Thirdly, they will enter the air-water separator. This separator removes 99.9% of the moisture. Eventually, discharge the water via auto drain.

④ Finally, the dry compressed air remains. They go back to the precooler. Pre-cool the new high temperature humidity. It also raises its own temperature. The air becomes drier. Finally, it leaves from the right side of the precooler for the user to use.

Refrigeration system of compressed air dryer:

① Firstly, the refrigerant leaves from the outlet of the compressor. They are used to cool down.

② Secondly, a small part of the refrigerant flows to the evaporator through the bypass valve. The remaining refrigerant continues to move forward. They will reach the condenser and will be cooled by the fan.

③ Thirdly, the refrigerant reaches the expansion valve. Perform further cooling.

④ Afterwards, the refrigerant enters the heat exchange tube of the evaporator. And it mixes with the relatively hot refrigerant coming directly from the bypass valve. This is to prevent ice blockage.

⑤ The refrigerant flows in the heat exchange tube. They exchange heat with high temperature air. It can cool down the compressed air and remove water. At the same time, it absorbs heat and turns into refrigerant vapor.

⑥ Finally, the refrigerant vapor returns to the compressor. Prepare for the next round of condensation work.

(2) Working principle of water-cooled refrigerant air dryer

In fact, its working principle is similar to air-cooled refrigerant dryer. They are two differences. Firstly, it uses the cooling water to cool the refrigerant vapor. Secondly,it is with cooling water automatic adjustment system. It automatically and constantly controls the cooling water volume according to the compressor discharge pressure and temperature. Therefore, it can guarantee a stable outlet dew point. At the same time, it can effectively prevent the evaporator from freezing.

The functions of refrigerated air dryer parts

①Refrigerant dryer evaporator

The evaporator is a heat exchange device. The refrigerant liquid absorbs heat and vaporizes in the evaporator. During the process, it generates a cooling effect on its surrounding environment.

② Refrigerant compressor

It is the most important part of refrigeration air dryer. The compressor draws refrigerant vapor from the evaporator. Then compress them. At the same time, it plays the role of conveying refrigerant in the refrigeration system.

③ Air compressor dryer condenser

The condenser is also a heat exchange device. The refrigerant condenses inside it and releases heat. This heat is carried away by air or water. So there are two types. That is, air-cooled and water-cooled condenser.

④ Throttling device: expansion valve or capillary

They allow the refrigerant liquid to change from high pressure to low pressure. So it creates conditions for the refrigerant to vaporize at low pressure and low temperature.

⑤ Hot gas bypass valve of refrigerated air dryer

The compressed air is cooled in the evaporator. Sometimes the evaporating temperature of the refrigerant is too low. So the condensed water will freeze in the evaporator. In severe cases, it will block our airflow channels. Then cause ice blockage.

In order to prevent this, we need to control the evaporation temperature of the refrigerant. This simple measure is to add a hot gas bypass valve between the condenser and the evaporator. When the evaporation pressure is low to a certain level, the hot gas bypass valve opens. This increases the evaporation temperature. Therefore, it can avoid the ice block phenomenon. Then this is the working principle of the bypass valve of refrigerant dryer.