Application of Environmentally Friendly Refrigerants in Ultra-low Temperature Refrigeration Systems

The development of refrigerant substitution technology promotes the advancement of refrigeration technology. The refrigerants often used in ultra-low temperature refrigeration systems in the past are R22, R13 and R501, R502, R503 series, of which R22, R13, and R502 are the most widely used.

According to the "Montreal Agreement", the ODP and GWP of refrigerants are two important assessment indicators. Based on this, R13 and R502 were completely eliminated in 2010; R22 is also a working fluid to be eliminated, so we are looking for new environmentally friendly alternative working fluids. It is the development trend of ultra-low temperature refrigeration technology. Fotech specifically introduces the application of environmentally friendly refrigerants in ultra-low temperature refrigeration systems for everyone below.

At present, the HFC environmentally friendly alternative refrigerants commonly used in two-stage or cascade refrigeration systems mainly include R134a, R404A, R507, R116, R508B, and R23.

The boiling points of R23, R116, and R13 are all around -80℃ which are very close to each other. They are the most likely choice for the refrigerant to replacing R13 in HFC substances.

In practical applications, it is found that R23 has problems such as damaging the moving parts of the compressor and decomposing the lubricating oil, and long-term use can also cause the motor coil to short-circuit. In addition, R23, R116, and R508B have high GWP values, so they can only be used as transitional refrigerants.

The experimental researches on R23 and R508B mainly focus on their cyclic performance as a low-temperature loop refrigerant in a cascade system. In the cascade refrigeration system, the refrigerant R717/R508B is substituted for R12/R13, and the simulation operation is carried out. The simulation results show that R717/R508B has better cycle performance in the ultra-low temperature range of -45~-60℃.

The cycle performance of using R23 as a substitute for R13 in the low-temperature loop of the cascade refrigeration system. The mass flow rate in the evaporator of the cascade refrigeration system with the evaporating temperature of -50~-70℃ and the refrigerant of R134a/R508B is 50~70g/min.

With the application and promotion of R134a refrigerant, many scholars have applied it to low-temperature systems; theoretical calculations and experiments have verified that R134a refrigerant can be used in a variety of cascade compression refrigeration systems and as a high-temperature loop refrigerant.

By comparing the single-stage refrigeration system with R134a as the refrigerant and the cascade refrigeration system with R134a/R508B, the analysis shows that the cascade refrigeration system can achieve lower evaporation temperature (-50~-75℃) and higher unit volumetric efficiency.

R404A and R507 are mid-to-long-term alternatives to R502 in ultra-low temperature systems. The operating performance of R404A, R507, and R22 in a two-stage compression refrigeration system is simulated. The simulation results show that the performances of R404A and R507 are relatively close. In addition, the low-temperature range achieved by the two-stage compression system using R404A and R507 is -45~-75℃ is wider than R22.

The design of a cascade system test unit that uses working fluids R404A/R23 instead of R22/R13 has been completed. The test results show that the system using the alternative working fluid R404A/R23 at -45~-60℃ has slightly lower cooling capacity than the original system, but other systems operating parameters are better than the R22/R13 system, and the reliability of the system is greatly improved.

Through experimental research on R507 and R502, it is found that the COP of the two is equivalent under the same low-temperature working condition (evaporating temperature -40℃), but the refrigeration capacity per unit volume of R507 is slightly higher than that of R502.

The ODP of HFC working fluid is 0, but its greenhouse effect is higher than natural working fluid and lower than CFC working fluid. It is still a greenhouse gas stipulated in the Kyoto Agreement; but according to calculations, its emissions account for a very small proportion of global greenhouse gas emissions.

Currently, the biggest problem of HFC-type refrigerant replacement is the problem of ultra-low temperature system lubrication and compressor matching. If these problems can be solved, it is a good choice to choose HFC-type refrigerant as a long-term replacement refrigerant for ultra-low temperature refrigeration systems.

Fotech is committed to contributing to the cause of environmental protection. Therefore, we vigorously research and develop environmentally friendly refrigerants. While ensuring safety and environmental protection, the refrigerant can also give full play to its excellent cooling effect.

FOTECH is a professional manufacturer of refrigerants and fluoropolymers. Our refrigerant gases have outstanding performance in household, industrial and commercial refrigerant systems. Our products have passed various safety certifications, and the quality of the products has also been fully controlled. At the same time, we put the needs of customers first and can provide customers with thoughtful one-stop service. If you are interested in our refrigerants, please contact us immediately!