From some years there is a lot of talk about “zero environmental impact” thanks the new refrigerant CO2 or R744 used in the industrial refrigeration market.
What is the CO2
CO2 or carbon dioxide is a natural substance, it can be used as refrigerant in several different applications like in heating and cooling area, thanks the high properties of heat Exchange and the high volumetric cooling capacity.
According to industry standards, each refrigerant receives a nomenclature starting with the letter R (for Refrigerant) and a number, which follows an order depending on the "family" the substance belongs to.
- R744 / R-744 is hence the standard nomenclature for CO2 used as a refrigerant
- "7" indicates the natural fluid while "44" refers to the fluid's weight.
- The term R744 is applied when referred to the refrigerant itself.
CO2 and/ or CO2 Technology is used when referring to an application or use.
Carbon dioxide is a very important component of the Earth’s atmosphere; it’s present in the air with a concentration level between 0,03% and 0,06%, together with other greenhouse gas (GHG), it adsorbs the infrared radiations and warm up the planet’s surface.
Thanks this effect the life on the Earth is guaranteed. Nevertheless due the uninterrupted increase of the CO2 concentration in the atmosphere owing to the use of fossil fuels, carbon dioxide is becoming the most dominant green house in our atmosphere. The bad reputation of carbon dioxide is partly owing to the measure of the global warming; it is measured by means of the GWP (Global Warming Potential), which is a scale of CO2 values divided per 100 years.
1kg of current refrigerant (R134a) has GWP as 1.410
1kg of R744 refrigerant has GWP as 1
Carbon dioxide however isn’t the last news in the world of industrial refrigeration.
It was in use during the first half of nineteen Century with a pike during 1920.
Later Carbon dioxide was supplant by natural chlorofluorocarbon (CFCS) which were operate with lower pressure.
Due the aggressive environmental impact of above mentioned natural refrigerants ,Carbon Dioxide was revaluated and studied to work with high pressures.
The main characteristics of Carbon Dioxide are:
- Not toxic
- Not flammable
- Not ozone depleting
- Environmentally friendly, with a Global Warming Potential = 1
Why CO2 ?
Refrigerant R744, as above mentioned, presents particular characteristics of environmental acceptability, as the non inflammability and non-ozone depleting.
Utilizing the carbon dioxide for vapor compressor applications it reduces significantly the green house gases emission quantity in the atmosphere.
Furthermore, in the carbon dioxide plants in several different applications presents a potential much more efficient respect the actual systems and consequently result reduced emissions thanks the reduced use of Greenhouse gases (GHG).
- Reduction of GHG
- High efficiency
- Recovery of Carbon dioxide as industrial waste. Thanks this operation CO2 can be taken from naturals sources, after the use inside plant it’s becomes industrial waste and reused for a new cycle.
Where is used the Carbon dioxide?
R744 can be used in several applications industrial and not industrial, as for example the auto motive air conditioning market (MAC - Mobile Air conditioning). R744 can be applied in most heating and cooling systems such as Mobile Air Conditioning (MAC) in vehicles and buses, vending machines, coolers, commercial cabinets for supermarkets, containers and climate control systems for residences. CO2 Technology (R744) has also shown to be extremely efficient in heating water. This explains the success of the CO2 in Japan.
A R744 plant can work up to 133 Bar, instead a system with Freon’s cannot work over 30 Bar.
In a plant in trans critical conditions doesn’t happen the condensation. The result is the elimination of the condenser and the use of the gas cooler, optimized to repel heat from R744 gases and send to external air. If the plant works with lower pressure levels, does it means it works in subcritical conditions, up to 52 bar.
In this case the CO2 will condense during the heat Exchange, inside the gas cooler, like the R134a inside the condenser.
Operations over the critical point as in the trans critical cycle is very favorable when it is spoken about refrigerant for high temperature cooling respect the heat exchange in a actual plant.
Furthermore the higher energy density in the R744 high pressure plants permits to reduce the dimensions of the tube lines and the dimension of the components.
Will follow, thanks the high energetically efficiency, the high pressure and reduced inner volumes, that pressure drop inside these plants is smaller respect the pressure drop in the Freon’s plants.