Air dryer refrigerant types and performance differences: key factors affecting equipment operation

In modern industrial production and daily life, compressed air is increasingly used. However, untreated compressed air contains a large amount of water vapor and impurities, which can cause serious damage to downstream equipment, pipelines and production processes, such as corrosion, blockage, and affect product quality. In order to solve this problem, air dryers came into being, which can effectively remove moisture from compressed air to ensure the dryness and cleanliness of compressed air.

There are many types of air dryers, among which refrigerated air dryers are widely used in various fields due to their high efficiency, stability and economy. The working principle of refrigerated air dryers is to condense the water vapor in compressed air into liquid water by lowering the temperature of compressed air, thereby achieving the purpose of drying. In this process, refrigerant is the core medium, and its type and performance directly affect the refrigeration efficiency, energy consumption, operating stability and environmental impact of the air dryer.

Therefore, it is of vital importance for users to select suitable air dryers, optimize equipment operation, reduce energy consumption and extend equipment life to have a deep understanding of the common refrigerant types of air dryers, the performance differences of different refrigerant types, and their relationship with air dryer performance. This article will discuss these key points in detail to help you better understand the world of air dryer refrigerants.

✅Common refrigerant types for air dryers

With the development of refrigeration technology and the improvement of environmental awareness, the refrigerants used in air dryers are also evolving. Early air dryers mostly used refrigerants that had a greater impact on the environment, but now they tend to use more environmentally friendly and efficient new refrigerants. At present, the common refrigerant types for air dryers mainly include the following categories:

1.1 Hydrochlorofluorocarbon (HCFCs) refrigerants

HCFCs refrigerants are a type of Freon family, which contain hydrogen, chlorine, fluorine and carbon atoms. This type of refrigerant was widely used in the field of refrigeration and air conditioning in the past, and was highly favored for its good refrigeration effect and stable properties. However, HCFCs refrigerants have a destructive effect on the ozone layer and have a high global warming potential (GWP). According to the provisions of the Montreal Protocol, HCFCs refrigerants are gradually being phased out.

In air dryers, common HCFCs refrigerants include:

R22: R22 is one of the most widely used HCFCs refrigerants, with good thermodynamic properties and low operating costs. However, R22 is destructive to the ozone layer and has a high GWP, and is currently being phased out worldwide. R22 can still be seen in some old air dryers, but it is basically no longer used in new equipment.

1.2 Hydrofluorocarbon (HFCs) refrigerants

HFCs refrigerants are new refrigerants developed to replace HCFCs refrigerants. They do not contain chlorine atoms and have no destructive effect on the ozone layer (ODP is zero). However, HFCs refrigerants still have a high global warming potential (GWP) and have a potential impact on climate change. Therefore, in some countries and regions, the use of HFCs refrigerants is also restricted or phased out.

In air dryers, common HFCs refrigerants include:

Comparison Dimensions	R134a	R404A	R407C	R410A
Chemical Type	Pure (HFC)	Mixed (HFC, R125/R143a/R134a)	Mixed (HFC, R32/R125/R134a)	Mixed (HFC, R32/R125, near azeotropic)
ODP (Ozone Depletion)	0	0	0	0
GWP (Global Warming Potential)	1430	3922 (Higher)	1774	2088
Azeotropic/Slip Status	Pure (No slip)	Near-azeotropic (Slip <0.5℃)	Non-azeotropic (Slip approx. 4-7℃)	Near-azeotropic (Slip <0.2℃)
Typical evaporation temperature range (°C):	-26 ~ +10	-45 ~ -10 (Strong low-temperature capability)	-30 ~ +10	-40 ~ +10
Coefficient of Performance (COP) Relative Value	Medium (baseline approx. 1.0)	High at low temperatures (slightly lower at medium and high temperatures)	Medium	High (approx. 10-15% higher than R134a)
Exhaust Temperature	Medium	Medium	Lower	Higher
System pressure level requirements	Low	Medium-High	Medium-High	High (Requires special components)
Typical Application Scenarios	Small and medium-sized dryers, ambient temperature, export areas with strict environmental regulations	Refrigerated dryers, low-temperature environments, cold storage	Upgrading of old R22 equipment	High-efficiency large-scale dryers, high-temperature and high-humidity areas

 

1.3 Natural refrigerants

Natural refrigerants refer to substances that exist in nature. They have little impact on the environment, and their ODP and GWP are very low or even zero. With the increasingly stringent environmental regulations, the application of natural refrigerants in the field of refrigeration has received more and more attention and is considered to be an important direction for the development of refrigerants in the future.

In air dryers, potential natural refrigerant applications include:

R290 (propane): Propane is a hydrocarbon with excellent thermodynamic properties and low GWP. It is a potential substitute for R22 and R404A. However, propane is a flammable substance and strict safety measures need to be taken during use and maintenance.

R600a (isobutane): Isobutane is also a hydrocarbon with good thermodynamic properties and extremely low GWP. It is mainly used in small refrigeration equipment, such as household refrigerators. Isobutane may also be considered in some small air dryers. Similar to propane, isobutane is also a flammable substance and requires safety.

R717 (ammonia): Ammonia is a traditional refrigerant with excellent thermodynamic properties and low operating costs. Its ODP and GWP are both zero. However, ammonia is toxic and corrosive, and is flammable and explosive, so its application is mainly limited to large industrial refrigeration systems, which have extremely high safety requirements. In the field of air dryers, the application of ammonia is relatively small, mainly concentrated in some large industrial drying systems.

R744 (carbon dioxide): Carbon dioxide is a substance that exists widely in nature and has an extremely low GWP. It can work efficiently at high temperatures and is a potential high-temperature refrigerant. However, the critical point of carbon dioxide is low, and it needs to operate under supercritical conditions, which requires high pressure resistance of the equipment. At present, the application of carbon dioxide in air dryers is still in the exploratory stage, mainly concentrated in some special application areas.

1.4 Other new refrigerants

In addition to the common refrigerant types mentioned above, some new refrigerants are being developed and tested to meet increasingly stringent environmental protection requirements and higher energy efficiency requirements. These new refrigerants may include:

Low GWP HFCs alternatives: Some companies are developing HFCs alternatives with lower GWP, such as HFOs (hydrofluoroolefins) refrigerants. HFOs have extremely low GWP and are an important direction for replacing high GWP HFCs in the future.

Non-refrigerant technology: In addition to traditional refrigerant cycle refrigeration technology, some non-refrigerant technologies are also being studied and applied in the field of air drying, such as adsorption drying, membrane separation drying, etc. These technologies do not rely on traditional refrigerants and have the potential to be environmentally friendly and energy-saving.

It should be noted that different types of air dryers (such as refrigeration, adsorption, membrane separation, etc.) have different requirements and applicability for refrigerants. This article mainly discusses the refrigerants used in refrigeration air dryers.

✅Performance differences between different types of refrigerants

Different types of refrigerants have significant differences in thermodynamic properties, safety, environmental protection, operating pressure, temperature range, etc. These differences directly affect the design, operating efficiency and cost of air dryers.

2.1 Thermodynamic properties

Thermodynamic properties are important indicators for measuring refrigerant performance, mainly including refrigeration capacity, energy efficiency ratio (COP), evaporation temperature, condensation temperature, pressure, etc.

Refrigeration capacity: refers to the ability of a unit mass or unit volume of refrigerant to absorb heat in the evaporator. Refrigerants with high refrigeration capacity can make the equipment more compact and provide greater refrigeration capacity under the same conditions. For example, the refrigeration capacity of R410A is generally higher than that of R22 and R134a.

Energy efficiency ratio (COP): refers to the ratio of effective refrigeration capacity to input energy in the refrigeration cycle. The higher the COP, the higher the refrigeration efficiency and the lower the energy consumption. The COP of different refrigerants under different working conditions varies greatly. Choosing a refrigerant with a high COP can help reduce the operating cost of the air dryer.

Evaporation temperature and condensation temperature: The evaporation temperature and condensation temperature of a refrigerant are related to its saturation temperature at a specific pressure. The lower the evaporation temperature and the higher the condensation temperature, the greater the temperature difference in the refrigeration cycle and the lower the refrigeration efficiency. The evaporation temperature of the air dryer is usually low, and a refrigerant with good thermodynamic properties at a lower temperature needs to be selected.

Pressure: Different refrigerants have different saturation pressures at the same temperature. High-pressure refrigerants require equipment with a higher pressure rating, and the equipment cost and safety requirements are also higher. For example, the working pressure of R410A is much higher than that of R22.

2.2 Safety

Safety is a key factor that must be considered when selecting a refrigerant, mainly including toxicity, flammability, and explosiveness.

Toxicity: Some refrigerants are toxic to the human body and may cause harm to human health when leaked. For example, ammonia is highly toxic. Most HFCs and HCFCs are less toxic, but long-term contact and inhalation still need to be avoided.

Flammability: Some refrigerants are flammable substances and may burn or explode under certain conditions. For example, propane and isobutane are flammable and explosive refrigerants. Strict explosion-proof measures need to be taken in equipment using these refrigerants.

Explosiveness: Some refrigerants may explode within a certain concentration range after mixing with air.

To ensure safety, international standards classify the safety of refrigerants. When selecting an air dryer, refrigerants with a higher safety rating should be given priority.

2.3 Environmental protection

Environmental protection is an increasingly important factor in the current selection of refrigerants, mainly including ozone depletion potential (ODP) and global warming potential (GWP).

Ozone depletion potential (ODP): refers to the potential impact of refrigerants on the destruction of the earth’s ozone layer. Refrigerants containing chlorine atoms (such as HCFCs and CFCs) have high ODP and have been or are being eliminated.

Global warming potential (GWP): refers to the ratio of the contribution of a unit mass of refrigerant to global warming in a given time scale to the contribution of the same mass of carbon dioxide. The higher the GWP of a refrigerant, the greater the impact on climate change. HFCs refrigerants generally have a high GWP and are the main target of future restrictions on use. Natural refrigerants generally have a low or zero GWP and have significant environmental advantages.

2.4 Operating pressure and temperature range

Different refrigerants have different working pressures and applicable temperature ranges.

Operating pressure: The operating pressure of the refrigerant determines the design pressure of the refrigeration system equipment (such as compressors, condensers, evaporators, etc.). High-pressure refrigerants require more robust equipment, which increases equipment costs.

Temperature range: Each refrigerant has its applicable evaporation temperature and condensation temperature range. It is crucial to select a refrigerant that fits the temperature range required by the air dryer. Air dryers usually need to operate at lower evaporation temperatures to ensure that they can effectively remove moisture from the air.

✅Relationship between refrigerant type and air dryer performance

The type of refrigerant directly or indirectly affects many key performance indicators of the air dryer.

3.1 Drying effect

The drying effect of the air dryer mainly depends on its dew point temperature (Pressure Dew Point, PDP). The lower the dew point temperature, the less moisture is contained in the compressed air, and the better the drying effect.

The evaporation temperature of the refrigerant is a key factor affecting the dew point temperature. A lower evaporation temperature can reduce the compressed air temperature more thoroughly, allowing more water vapor to condense.

Different refrigerants can achieve different minimum evaporation temperatures under the same operating conditions, which determines the minimum dew point temperature that the air dryer can achieve. For example, some low-temperature refrigerants can achieve lower dew point temperatures and are suitable for applications with higher drying requirements.

3.2 Energy consumption

Energy consumption is an important indicator for measuring the operating cost of air dryers. The type and thermodynamic properties of refrigerants directly affect the power consumption of the compressor and the energy efficiency of the entire refrigeration system.

Refrigerants with high energy efficiency ratio (COP) mean that the required compressor power consumption is lower when producing the same cooling capacity, thereby reducing the energy consumption of the air dryer.

The working pressure of the refrigerant also affects the power consumption of the compressor. Refrigerants working under high pressure may require higher power compressors.

The heat transfer properties of the refrigerant (such as thermal conductivity) will affect the efficiency of the heat exchanger, and thus affect the energy consumption of the entire system.

3.3 Operation stability

The chemical stability, compatibility with materials, and working pressure range of the refrigerant will affect the operating stability of the air dryer.

Refrigerants with poor chemical stability may decompose during operation, produce harmful substances, corrode equipment or block pipelines, causing equipment failure.

Refrigerants with poor compatibility with materials may corrode pipelines and damage seals, causing refrigerant leakage or system performance degradation.

Refrigerants with working pressures exceeding the pressure range of the equipment may cause equipment damage or even safety accidents.

✅How to choose the right type of refrigerant

Choosing the right type of refrigerant requires a comprehensive consideration of multiple factors to balance performance, cost, safety and environmental protection. Here are some key considerations:

4.1 Dew point requirements

First, it is necessary to clarify the dew point temperature required for the air dryer. Different application scenarios have different requirements for the dryness of compressed air. For example, some industries such as precision instruments, electronic manufacturing, food and medicine have high dew point requirements and may need to reach a dew point of -40℃ or lower. Some ordinary industrial applications may only need to reach a dew point of 2-7℃. The dew point requirement directly determines the required evaporation temperature, which in turn affects the choice of refrigerant. Applications that require low temperature dew points may need to choose refrigerants that can work efficiently at lower temperatures.

4.2 Ambient temperature and operating conditions

The operating ambient temperature and operating conditions of the air dryer will also affect the choice of refrigerant. For example, an air dryer operating in a high temperature environment needs to choose a refrigerant that can still maintain good performance at a higher condensing temperature. At the same time, factors such as humidity and altitude where the equipment is located need to be considered.

4.3 Energy consumption requirements and operating costs

Energy consumption is the main component of the operating cost of air dryers. Selecting a refrigerant with a high energy efficiency ratio (COP) can significantly reduce energy consumption and operating costs. When selecting a refrigerant, the actual operating conditions of the equipment should be combined to compare the energy efficiency performance of different refrigerants under these conditions.

4.4 Safety requirements

Select a refrigerant that meets safety requirements based on the application environment and safety specifications of the equipment. If the equipment is installed in a crowded area or a place with special safety requirements, low-toxic, non-flammable and non-explosive refrigerants should be given priority. If flammable refrigerants are used, strict safety measures must be taken, such as ventilation, leak detection, explosion-proof design, etc.

4.5 Environmental regulations and development trends

Understand the restrictions and elimination plans of local and international environmental regulations on refrigerants, and select a system that meets current and future environmental requirements.With the improvement of environmental awareness, low GWP and natural refrigerants are the future development trend. Choosing these refrigerants can help avoid the risks brought by future regulatory changes.

Summary

The refrigerant type of air dryer is a key factor affecting equipment performance, energy consumption, operational stability, safety and environmental protection. Understanding the performance differences of different refrigerant types and making comprehensive evaluations and selections based on specific application requirements are of vital importance to ensure the optimal operation of air dryers, reduce operating costs, extend equipment life, and comply with environmental regulations.

From traditional HCFCs to transitional HFCs, to future natural refrigerants and new low-GWP refrigerants, the selection of air dryer refrigerants is moving towards a more environmentally friendly and efficient direction. When choosing an air dryer, users should fully consider the various performance indicators of the refrigerant and make wise decisions based on their actual needs. At the same time, with the continuous advancement of technology and the increasingly stringent environmental regulations, paying attention to the latest development trends of refrigerants and choosing refrigerants that meet the future development direction are crucial for the long-term stable operation and sustainable development of equipment.