C6.1.11/0718-0619/E
7
2.6.4 Pressure levels of CO
2
vs. other refrigerants
Figure 5
below compares the evaporating pressures of R744 to those encountered with R410A and
R404A. It can be observed that R744 systems will require to operate at much higher pressures than
conventional systems.
Note that below a pressure of 5.2 bar, solid and gaseous R744 phases may co-exist at low
temperature. This behaviour is totally different from that observed with traditional refrigerants, and
will have important consequences on the operation, servicing and maintenance of a system working
with R744.
Gaseous R744 is 1.5 times heavier than air. Therefore, when released to the air it will concentrate
at low elevations.
R744 will form "dry ice" at -56.6°C. One kg of dry ice has the cooling capacity of 2 kg of ordinary ice.
Gaseous or liquid R744 stored under pressure will form dry ice through an auto-refrigeration process
if rapidly depressurized.
Figure 5: Pressure levels of CO
2
Figure 6
shows the thermodynamic properties (p-h-diagram) of R744. Compared to other fluids
traditionally used as refrigerants, its critical point at 31°C is very low and its critical pressure at about
73.6 bar is high.
Figure 6: Pressure/enthalpy diagram CO
2
Summary of Contents for Copeland EazyCool OME-4MTL-09X
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