CO2 for transport refrigeration systems

A paper presented during the 10th IIR Gustav Lorentzen Conference held in Delft in 2012 summarizes developments on cryogenic solutions for refrigerated vehicles using liquid CO2 in an open cycle system.
A paper* presented during the 10th IIR Gustav Lorentzen Conference held in Delft in 2012 summarizes developments on cryogenic solutions for refrigerated vehicles using liquid CO2 in an open cycle system.

Unlike cryogenic transport refrigeration systems that spray nitrogen directly into the load space, this system uses a fin-and-tube evaporator which acts as a heat-exchanger in the load space, while the CO2 itself remains outside the load space. Liquid CO2 is stored in a vacuum-insulated tank at 8.5 bar at around -45°C. A pair of expansion valves of different orifice sizes in the evaporator coil regulates the flow of liquid into the coil, allowing for variable refrigeration capacity. The CO2 is then vented outside without being sprayed into the load space which provides safety to the operators.

According to estimates, the system has comparatively lower carbon footprints (46 tons CO2 over 10 years) than diesel (166 tons CO2) or nitrogen systems (143 tons) as nitrogen liquefaction requires about 3 times more energy than CO2’s. It is also said to be 90% quieter than a standard diesel-driven unit.

*Transport refrigeration systems using CO2.  S. Dutta et al. 10th IIR Gustav Lorentzen Conference on Natural Refrigerants, Delft, The Netherlands, 2012

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