International. Recent research was presented on the evolution of cryogenic solutions for vehicles cooled with liquid CO2 in an open cycle system.
According to experts, unlike cryogenic transport refrigeration systems that spray nitrogen directly into the cargo space, this system uses a fin and tube evaporator, which acts as a heat exchanger in the cargo space, while the CO2 itself remains outside the cargo space.
The liquid CO2 is stored in a vacuum-insulated tank on a bar of 8.5 to around -45°C. A pair of expansion valves of different sizes of holes in the evaporator coil regulate the flow of liquid within the coil, allowing for variable cooling capacity. The CO2 is then transported outwards without being sprayed into the cargo space, providing safety for operators.
According to estimates, the system has comparatively lower carbon emissions (46 tons of CO2 in 10 years) than diesel (166 tons of CO2) or nitrogen systems (143 tons) since nitrogen liquefaction requires about 3 times more energy than CO2. It is also said to be 90% quieter than a standard diesel unit.
