Why is carbon dioxide refrigeration important? What are the advantages and disadvantages of carbon dioxide heat pumps

January 17, 2022

Latest company news about Why is carbon dioxide refrigeration important? What are the advantages and disadvantages of carbon dioxide heat pumps

Carbon dioxide is a substance in nature and a very good refrigeration substance. In fact, carbon dioxide as a refrigerant has a history of a hundred years, and was widely used from the end of the 19th century to the 1930s. With the application of ammonia and freon refrigerants, carbon dioxide refrigerants quickly withdrawn from the stage of history.

In March 2021, Beijing held the China Carbon Peak Carbon Neutral Achievement Release and Seminar, and released China's target plan for achieving carbon peaking by 2030 and carbon neutrality by 2060. The carbon emissions of China's refrigeration industry come from electricity consumption and carbon dioxide emissions in the production process on the one hand, and non-carbon dioxide greenhouse gas emissions such as refrigerants on the other hand. From a global perspective, commercial refrigeration is the main body of refrigeration, and its refrigerant emissions are the largest (calculated by 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 paid more attention to.


1. Advantages and disadvantages of carbon dioxide refrigerant

Carbon dioxide is a natural substance, ODP=0, GWP=1. The use of carbon dioxide as a refrigerant has no detrimental effect on the atmospheric ozone layer, can reduce the global greenhouse effect, and has a wide range of sources and low prices, which can greatly reduce the cost of refrigerant replacement, save energy, and solve the problem of environmental pollution by compounds. sex.


Carbon dioxide is safe, non-toxic, non-flammable, non-explosive, and has good thermal stability. Even at high temperatures, it will not decompose harmful gases, and leakage will not harm the human body, food, and ecology.
Carbon dioxide has thermophysical properties suitable for refrigeration cycles and equipment. The molecular weight is small, the cooling capacity is large, and the unit cooling capacity at 0°C is 5 to 8 times higher than that of conventional refrigerants. Therefore, for the 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 the refrigeration system, which can improve the sealing performance of the open compressor and reduce leakage.


The viscosity of carbon dioxide is small, the kinematic viscosity of carbon dioxide saturated liquid at 0 ℃ is only 5.2% of NH3 and 23.8% of R12, the flow resistance of the fluid is small, and the heat transfer performance is better than that of CFC refrigerants, which can improve the heat dissipation of hermetic refrigeration compressors .


Can not sustain life, if the concentration is too high, it will cause damage to human respiratory organs, or even suffocate death;


It has high critical pressure and 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 the subcritical cycle or the 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.
2. Application of carbon dioxide

The research and application of carbon dioxide mainly focus on three aspects:
On the one hand, in the field of automobile air conditioning, due to the large amount of refrigerant emissions, the harm to the environment is also great;


In the field of heat pump hot water, there is a considerable temperature glide in the heat release of carbon dioxide under supercritical conditions, which is beneficial to heating hot water to a higher temperature (above 90°C) at extremely low ambient temperature.


In the field of cascade refrigeration cycle, carbon dioxide has good low temperature flow performance and heat transfer characteristics, and it is used as a low temperature refrigerant for CO2/NH3 cascade refrigeration cycle.

As mentioned earlier, excessive carbon dioxide concentration can cause damage to people's respiratory organs, or even suffocation. Therefore, leakage monitoring is required. The relevant requirements are as follows:

If the carbon dioxide concentration exceeds the limit value, only trained personnel are allowed to enter;

The alarm must sound and light at the same time, and cover both indoor and outdoor;

The ventilation system and the alarm must not use the same power source;

The alarm must be able to activate the ventilation, preferably the shut-off valve;

Vents and detectors must be installed as low as possible;

The detector must monitor CO2 concentration, not hypoxia.

3. Application of carbon dioxide in cascade refrigeration system

The CO2/NH3 cascade refrigeration cycle is composed of the NH3 high temperature stage refrigeration cycle and the CO2 low temperature stage refrigeration cycle. The two independent refrigeration systems are coupled through the evaporator-condenser (intermediate heat exchanger). Appropriate evaporating temperature when evaporating at lower evaporating temperature, and moderate condensing pressure when condensing at ambient temperature.
Leomon supply various CO2 air source heat pump

CO2 carbon dioxide (R744) heat pump,COP of 4.6,output hot water of 90℃,specification cover 5-200kw, production capacity of 4000 sets/year. We have both air source and water source CO2 heat pumps for customer choose. Usage for hot water and heating system for commercial and domestic, CO2 heat pump is green technology solution to achieve carbon neutrality, carbon emissions is friendly environment, very hot sale in Europe and America


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