Defrost system which utilizes electric heater for thermosiphon

A refrigeration apparatus comprising:

• a cold storage room;
• a cooler located in the cold storage room, the cooler including a casing and a heat exchanger, the heat exchanger being positioned inside the casing;
• the heat exchanger comprising plural heat exchange tubes through which CO2 refrigerant flows, the plural heat exchange tubes each having a lower end and an upper end, the lower end of each of the plural heat exchange tubes being coupled to a lower header and the upper end of each of the plural heat exchange tubes being coupled to an upper header, the upper header being positioned vertically above the lower header;
• a drain pan located in the cold storage room at a position below the heat exchanger;
• a circulation line connected to the heat exchanger and configured to circulate the CO2 refrigerant;
• a refrigeration cycle that cools and reliquefies the CO2 refrigerant in a gaseous form with a refrigerant that circulates inside the refrigeration cycle;
• a defrost system positioned inside the cold storage room and outside the cooler to melt and remove frost attached to an outer surface of the heat exchanger during defrosting, the defrost system comprising:
• a thermosiphon defrost circuit that forms a CO2 circulation path together with the heat exchanger, the thermosiphon defrost circuit branching from the circulation line so that during the defrosting, the CO2 refrigerant staying inside the heat exchanger repeats a two-phase change of a gaseous form and reliquefaction;
• an opening/closing valve that is closed during the defrosting and that sets the CO2 circulation path to a closed circuit in which the CO2 refrigerant is naturally circulated during the defrosting;
• the thermosiphon defrost circuit including:
• a first line branching from the circulation line of the CO2 refrigerant;
• a first header to which an end of the first line is connected, the first header to which the end of the first line is connected including first and second parts that are spaced apart from one another, the first line providing communication between the first header of the thermosiphon defrost circuit and the lower header of the heat exchanger so that the CO2 refrigerant that has entered the lower header after flowing through the plural heat exchange tubes flows toward the first header;
• a second header provided at a position higher than the first header, the second header including first and second parts that are spaced apart from one another;
• the first part of the first header and the first part of the second header being closest parts of the first and second headers, the second part of the first header and the second part of the second header being most distant parts of the first and second headers, a straight line distance between the closest parts of the first and second headers being less than a straight line distance between the most distant parts of the first and second headers;
• plural second lines that extend between and communicate the first and second headers, the plural second lines including a line connecting the most distant parts of the first header and the second header in a meander shape, and a line connecting the closest parts of the first header and the second header in a meander shape;
• a third line that provides communication between the second header of the thermosiphon defrost circuit and the upper header of the heat exchanger;
• and
• an electric heater positioned inside the cold storage room and outside the casing, the electric heater being positioned above all of the second lines that extend between and communicate the first and second headers, the electric heater being configured to heat and vaporize the CO2 refrigerant liquid in the second lines during the defrosting and without a brine circuit so that the CO2 refrigerant liquid that is vaporized rises in the thermosiphon defrost circuit by the principle of thermosiphon.