Passive refrigeration system using carbon dioxide snow

A passive refrigeration apparatus for controlled refrigeration of a product, the refrigeration apparatus comprising:

• an insulated container, the container defining a cargo space for receiving a load;
• a cylinder for supplying a flow of liquid carbon dioxide (CO2);
• a control valve, in fluid communication with the cylinder, via a fluid pipe;
• a controller, adapted to activate and deactivate the control valve, to control the flow of liquid CO2;
• a heat transfer assembly, disposed within the container, and in fluid communication with the control valve;
• and
• an exhaust fluid line in fluid communication with the heat transfer assembly;
• wherein the heat transfer assembly comprises;
• an expansion section, in fluid communication with the control valve, and for receiving the flow of liquid CO2;
• and
• an expansion chamber, the expansion chamber bounded by at least one heat transfer surface, the at least one heat transfer surface in thermal contact with the cargo space;
• wherein the expansion section is adapted to allow a vaporization of the liquid CO2 into the expansion chamber in order to create a mixture of carbon dioxide snow and CO2 gas within the expansion chamber, thereby cooling the cargo space via the at least one heat transfer surface, and wherein the CO2 gas may be exhausted through the exhaust fluid line;
• and
• wherein the heat transfer assembly additionally comprises at least one bluff body, disposed within the expansion chamber and proximate to the expansion section, wherein the at least one bluff body facilitates generation of turbulence within the expansion chamber, in order to facilitate creation and accumulation of carbon dioxide snow.