Carbon dioxide is a substance in nature and a very good refrigeration substance. In fact, carbon dioxide has been used as a refrigerant for hundreds of years and was widely used from the end of the 19th century to the 1930s. As ammonia and Freon refrigerants began to be used, carbon dioxide refrigerants quickly withdrew from the stage of history.
In March 2021, Beijing held a release and seminar on China's carbon peak and carbon neutrality results, and released China's goal plan to peak carbon before 2030 and achieve carbon neutrality before 2060. The carbon emissions of China's refrigeration industry come from carbon dioxide emissions during electricity consumption and production on the one hand, and from the emissions of non-carbon dioxide greenhouse gases such as refrigerants on the other. From a global perspective, commercial refrigeration is the main body of refrigeration, with the largest refrigerant emissions (calculated in terms of CO2 equivalent), accounting for more than 30% of the total refrigerant emissions. If CO2 is used as the refrigerant, the carbon footprint of the commercial refrigeration system can be reduced Reduced to almost zero! This is the main reason why carbon dioxide refrigerants are valued by everyone again.
Advantage:
Carbon dioxide is a natural substance, ODP=0, GWP=1. Using carbon dioxide as a refrigeration working fluid has no destructive effect on the atmospheric ozone layer, can reduce the global greenhouse effect, and is widely sourced and cheap. It can greatly reduce the cost of refrigerant replacement, save energy, and solve the problem of environmental pollution caused by compounds, and has good economic benefits. sex.
Carbon dioxide is safe, non-toxic, non-flammable, non-explosive, and has good thermal stability. It will not decompose into harmful gases even at high temperatures, and leakage will not harm the human body, food, or ecology.
Carbon dioxide has thermophysical properties suitable for refrigeration cycles and equipment. The molecular weight is small and the refrigeration capacity is large. The unit cooling capacity at 0°C is 5 to 8 times higher than that of conventional refrigerants. Therefore, for a refrigeration system with the same cooling load, the size of the compressor can be significantly reduced, the weight is reduced, and the entire system is very compact; Lubrication The conditions are easy to meet, and there is no corrosion to common materials in refrigeration systems. It can improve the sealing performance of open compressors and reduce leakage.
The viscosity of carbon dioxide is small. The kinematic viscosity of carbon dioxide saturated liquid at 0°C is only 5.2% of NH3 and 23.8% of R12. The fluid has small flow resistance and better heat transfer performance than CFC refrigerants, which can improve the heat dissipation of fully enclosed refrigeration compressors. .
Shortcoming:
It cannot sustain life. If the concentration is too high, it will cause damage to human respiratory organs and even death from suffocation;
It has a high critical pressure and a low critical temperature; the critical temperature of CO2 is Tc=31.1℃, the critical pressure is Pc=7.3MPa, the critical temperature of water is 374℃, and the critical pressure is 22MPa.
Regardless of subcritical cycle or transcritical cycle, the operating pressure of the CO2 refrigeration system will be higher than that of the traditional refrigeration and air-conditioning system, which brings many difficulties to the design of the system and components, and the manufacturing cost is relatively high.
November 09, 2023
Carbon dioxide is a substance in nature and a very good refrigeration substance. In fact, carbon dioxide has been used as a refrigerant for hundreds of years and was widely used from the end of the 19th century to the 1930s. As ammonia and Freon refrigerants began to be used, carbon dioxide refrigerants quickly withdrew from the stage of history.
