3.Freeman Valve can also configure the following valves with electric/pneumatic actuators to achieve automated operation of the valves.

What is carbon dioxide (CO2) refrigerant?

Carbon dioxide (CO2) refrigerant, often called R-744 when used as a refrigerant, is a natural refrigerant. Carbon dioxide (CO2) has been used as a natural refrigerant for about a century. But it was quickly abandoned due to its technical complexity. It has excellent thermophysical properties, despite difficulties due to its low critical temperature value (30.978°C) and high pressure (140 Bar).

What promotes the large-scale application of natural refrigerants?

Nearly 200 countries reach groundbreaking climate deal at Dubai Climate Summit 2023, calling for transition away from fossil fuels in an unprecedented deal. The agreement is bound to further promote the large-scale application of natural refrigerants.

The advantages of carbon dioxide (CO2/R744) as a refrigerant:

1.Carbon dioxide is environmentally benign, non-toxic and non-explosive.

2.Carbon dioxide refrigerant is far less expensive than synthetic refrigerants (HFC/HCFC).

3.Dry carbon dioxide is non-corrosive with most materials and has good miscibility with compressor lubricants for oil return.

4.Carbon dioxide is a very dense refrigerant with a high volumetric efficiency and hence allows the pipe size and compressor swept volume to be much smaller than an equivalent HFC system.

5.The effect of pipeline pressure drop is less noticeable with carbon dioxide than HFC refrigerants.

Carbon dioxide has a much higher heat transfer efficiency, therefore heat exchangers can be smaller, or operate at a lower TD, than an equivalent HFC unit.

6.Trans-critical carbon dioxide packs are designed at higher pressures and supplied with pressure relief valves that do not discharge when the power is turned off, or the equipment shuts down for any reason.

7.Trans-critical carbon dioxide packs run with a very high discharge temperature therefore the opportunity to offer efficient heat reclaim is far better than for an equivalent HFC system.

8.Carbon dioxide is a stable molecule leading to a low potential for decomposition within the refrigeration system.

The disadvantages of carbon dioxide (CO2/R744) as a refrigerant:

1.Carbon dioxide operates at a far higher pressure than typical HFC refrigerants, therefore the leak potential increases and the component cost becomes higher (carbon dioxide (CO2/R744) refrigerant up to 140 Bar).

2.Carbon dioxide packs and condensing units need special components, more controls and safety features than an equivalent HFC unit, therefore the component and equipment cost becomes higher.

3.Carbon dioxide can change from a gas directly to a solid (triple point) at 4.2bar therefore the commissioning engineer must take more care when charging the system with refrigerant. Also the design of PRV vent lines must allow for the possible freezing of carbon dioxide as it approaches atmospheric pressure.

4.Carbon dioxide is very sensitive to water contamination and can form unusual compounds when there is a leak in a water heat exchanger. It is also important to ensure that no moisture is allowed into the system when charging refrigerant or oil.

5.When the requirement for gas leak detection is considered we need to compare the room volume with the refrigerant “practical limit” value to establish the maximum gas charge of the system. Carbon dioxide has a “practical limit” of approx 25% when compared to other HFC refrigerants, which means that leak detection equipment is 4 times more likely to be required.

What valves/fittings does Freeman Valve produce for use with carbon dioxide (CO2/R744) refrigerants?

1.Freeman Valve manufactures ball valves and globe valves for pressures up to 150 Bar.

2. For ball valves with sizes DN65 DN80 and DN100, Freeman Valve Company can also provide ball valves with pressures up to 150 Bar.