Carbon dioxide is a kind of substance in nature, and it is also a very good refrigerant, so in many places, people use carbon dioxide to achieve the purpose of refrigeration.
Carbon dioxide refrigeration technology - introduction.
As a natural refrigerant, carbon dioxide has been highly valued in recent 20 years due to its excellent environmental performance and refrigeration performance, and its research and development has made rapid progress.
This article introduces the history and status quo of the carbon dioxide refrigeration technology, thermal physical properties, flow heat transfer characteristics of carbon dioxide, carbon dioxide and oil and carbon dioxide and sealing rubber material interactions, such as all kinds of co2 cycle and its features and performance, carbon dioxide refrigeration system with a compressor, expander, heat exchanger, throttle valve, relief valve and the discharge characteristics, various application of refrigeration system and the characteristics of carbon dioxide and carbon dioxide refrigeration system steady state performance simulation method.
Carbon dioxide refrigeration technology - principle.
CO2 is a gas under normal temperature and pressure, which can be condensed into liquid (or even solid) under constant temperature pressure. After the pressure is removed, it evaporates rapidly (sublimation), and it takes away a lot of heat to achieve the purpose of cooling. The stage USES dry ice to make fog, which USES this principle. Dry ice absorbs heat and cools, condensing water vapor in the air into droplets and forming fog.
CO2 as refrigerant has many benefits: after the freon type of refrigerant is replaced, the biggest of the dangers of the refrigerant is increasing greenhouse effect, it is the effect of CO2 on greenhouse effect of 200 times, so CO2 refrigerant is better than current refrigerant R14 (car refrigerant is r134a)
Carbon dioxide refrigeration technology - currently three applications.
At present the research and application of carbon dioxide mainly focused on three aspects: on the one hand is car air conditioning field, because of the refrigerant emissions is big, too big to the harm of environment, must be with no harm to the environment of refrigerant as soon as possible
The second aspect is the heat pump water heater, which has a considerable temperature slip in the supercritical condition, which helps to heat the hot water to a higher temperature.
The third aspect is to consider the good low temperature flow performance and heat transfer characteristics of carbon dioxide, and it is used as a cryogenic refrigerant for the cascade refrigeration cycle.
In the complex refrigeration system, the carbon dioxide cycle is operated under subcritical conditions. At this time, carbon dioxide is used as a low-pressure grade refrigerant, and the high-pressure stage is used as a refrigerant for NH3.
Compared with other low-pressure refrigerants, even at low temperature, the viscosity of carbon dioxide is very small, and the heat transfer performance is good. Because of the latent heat, its refrigeration capacity is quite large.
At present, in the supermarket in Europe has established several this using carbon dioxide as refrigerant in low temperature cascade refrigeration system, the operation that is technically feasible, the system also applies to the freeze drying process at low temperature
C.W.Bullard of the air conditioning and refrigeration center of the university of Illinois (UIUC) has conducted extensive theoretical and experimental research on the application of carbon dioxide (co2) in household air conditioning and supermarket refrigerator.