A mixed refrigerant gas is a refrigerant that is a mixture of two or more refrigerants in a certain proportion. This refrigerant has unique physical and chemical properties and is suitable for a specific refrigeration system.
Mixed Refrigerant Gas Refrigeration principle
The refrigeration principle of mixed refrigerants mainly involves multiple-cycle processes, including single cycle process, double cycle process and triple cycle process. These processes achieve refrigeration through the circulation process of mixed refrigerant gas between compressors, condensers, throttles and evaporators.
The core of the refrigeration principle of mixed refrigerant gas is to achieve efficient heat transfer and liquefaction processes through the circulation of refrigerants at different pressures and temperatures. These processes are usually used in the fields of natural gas liquefaction, large-scale refrigeration facilities, etc., to achieve efficient energy conversion and storage.
Mixed Refrigerant Gas Types
Mixed refrigerant gas can be divided into two categories: azeotropic mixed refrigerant gas and non-azeotropic mixed refrigerant gas.
Azeotropic mixed refrigerants
When azeotropic mixed refrigerant gas boil at constant pressure, the vapor pressure of each component remains unchanged, so its vapor composition is always consistent with the liquid composition. During the evaporation and condensation process of this refrigerant, the temperature and pressure remain constant, and it is suitable for systems that require precise temperature control. Common azeotropic mixed refrigerant gas include R-502, R-507, etc.
Non-azeotropic mixed refrigerants
During the evaporation and condensation process of non-azeotropic mixed refrigerant gas, the vapor pressure of each component is different, resulting in inconsistency between its vapor composition and liquid composition. The temperature and pressure of this refrigerant will change during the evaporation and condensation process, and it is suitable for systems that require a large temperature glide. Common non-azeotropic mixed refrigerant gas include R-407C, R-410A, etc.
4 Common Mixed Refrigerants
R507 Refrigerant
R507 is an azeotropic mixture of HFC-125 and HFC-143a. Its physical and thermodynamic properties are similar to those of R502. It is mainly used to replace R502 and is used in medium and low-temperature commercial refrigeration systems, such as supermarket display cabinets and ice machines.
R507 is an azeotropic mixture of HFC125 and HPC143a. Its chemical properties are the same as its components. It is stable at room temperature and pressure. It decomposes in the presence of open flames or high temperatures to produce HF and carbonyl fluoride. It reacts with active metals such as alkali metals, alkaline earth metals, and metal powders such as A, Zn, and Be.
R-507 is compatible with the following materials: EPDM, EPDM copolymer, chlorosulfonated polyethylene, chlorinated polyethylene, chloroprene rubber, polysulfide, nylon, PTFEPEEK, polyethylene terephthalate, polysulfone, polyimide, acetal resin, phenolic plastic, epoxy resin. It is incompatible with the following materials: silicone elastomer, polyvinylidene fluoride, hexafluoropropylene and vinylidene fluoride copolymer.
R407C Refrigerant
R407C is a non-azeotropic (near-azeotropic) mixture of HFC32, HFC125, and HFC134a. Its physical and thermodynamic properties are similar to those of HCFC-22 and can be used to replace HCFC-22.
R-407C will decompose and produce toxic and irritating HF when exposed to open flames and high temperatures and will react with alkali metals, alkaline earth metals, and metal powders such as Al, Zn, and Be.
The flammability of R-407C is similar to that of other hydrofluorocarbons. Whether its mixture with air is explosive also depends on the temperature, pressure, and oxygen content of the system.
In refrigeration and air conditioning systems, R-407C/POE is compatible with commonly used metals such as aluminum, steel, and copper.
R-407C has good compatibility with the following rubber materials: Alcryn, styrene-butadiene rubber, butyl rubber, chlorosulfonated polyethylene, EPDM, ethylene-propylene copolymer, Hytre®, natural rubber, nitrile rubber, chloroprene rubber, polysulfide, polyurethane, Santopen@, and silicone elastomer. Among these rubbers, polybutadiene rubber, EPDM rubber, ethylene-propylene copolymer, polyurethane, silicone elastomer and R407C/POE mixture have poor compatibility, and VitonA and Vion®B have poor compatibility with R-407.
The following plastics have good compatibility with R-407: high-density polyethylene, polypropylene, polyvinyl chloride, epoxy resin, acetal resin, polybutylene terephthalate, nylon, polyurethane polyimide, polysulfone. Among them, high-density polyethylene, polypropylene, acetal, and nylon have poor compatibility in R-407C/POE.
XH-6, XH-9, and XH-11 desiccants are compatible with R-407℃.
R410A Refrigerant
R-410A is a mixed refrigerant composed of HFC-32 [50% (mass)] and HFC-125 [50% (mass)].
R-410A decomposes in the presence of open flames and high temperatures to release toxic and irritating HF and reacts with active metals such as alkali metals, alkaline earth metals, powdered wood Al, Zn, Be, etc.
Under normal pressure, it is non-flammable in air up to 100°C, but it is flammable in pressurized, heated, high-concentration air and oxygen-rich atmospheres.
Rubbers with good compatibility with R-410A include Alcryn, butyl rubber, chlorinated polyethylene, EPDM rubber, ethylene-propylene copolymer, Hyire, natural rubber, nitrile rubber, chloroprene rubber, polysulfide, polyurethane, Santoprene siloxane, among which ethylene-propylene copolymer, polyurethane, natural rubber, nitrile rubber, and silicone rubber have poor compatibility in R-410A/POE. Rubbers with poor compatibility include (Viton®A and Viton®B).
Plastics with good compatibility with R-410A include high-density polyethylene, polypropylene, polyvinyl chloride, epoxy resin, polybutylene terephthalate, nylon, polyurethane, and polyimide. Among them, high-density polyethylene, polypropylene, polyvinyl chloride, polybutylene terephthalate, and nylon have poor compatibility in R-410A/POE.
XH-6, XH-9, and XH-11 desiccants can be used in R-410A systems.
R404A Refrigerant
R404A is a mixed refrigerant gas composed of HFC-125, HFC-143a, and HFC-134a, mainly used to replace R-502.
R-404A decomposes in the presence of open flames and high temperatures to produce toxic and irritating HF and reacts with active metals such as alkali metals, alkaline earth metals, powder A, Zn, Be, etc. It is non-flammable in air up to 100°C under normal pressure but is flammable in high-concentration air under pressure and heating and is flammable in an oxygen-rich atmosphere.
R-404A/POE does not react with common metals such as copper, aluminum, and steel.
Mixed Refrigerant gas Application
Mixed refrigerants are widely used in various refrigeration and air-conditioning systems, such as household air conditioners, commercial air conditioners, and refrigeration equipment. They have the characteristics of high efficiency, environmental protection, and safety and can meet the needs of different systems. For example, R-410A, as a non-azeotropic mixed refrigerant gas, is widely used in household and commercial air-conditioning systems to replace traditional R-22 refrigerants due to its environmental protection and high efficiency.
Mixed Refrigerants Advantages and Disadvantages
The advantages of mixed refrigerant gas include high efficiency, environmental protection, and safety, but the disadvantages are high cost and the need to control the mixing ratio to ensure stable performance accurately. In addition, the filling and recycling process of mixed refrigerant gas is relatively complicated and requires professional technology and equipment.
In summary, mixed refrigerant gas plays an important role in refrigeration and air-conditioning systems due to their unique physical and chemical properties. By selecting the appropriate mixing ratio and application scenarios, their advantages of high efficiency, environmental protection and safety can be fully utilized while paying attention to their cost and operational complexity.
