Defrost system

Abstract

To provide a defrost system capable of preferable defrosting and prevention of generation of icicles on a casing without installing a brine circuit. A defrost system includes a thermosiphon defrost circuit that is provided by being branched from a circulation line, in which, at the time of defrosting, a CO 2 refrigerant staying inside a fin-tube heat exchanger repeats a two-phase change of a gaseous form and reliquefaction, and which forms a CO 2 circulation path together with the fin-tube heat exchanger; electromagnetic opening/closing valves and that are closed at the time of defrosting and set the CO 2 circulation path to a closed circuit; and a first electric heater arranged above the thermosiphon defrost circuit so as to be adjacent to the thermosiphon defrost circuit, and naturally circulates the CO 2 refrigerant in the closed circuit at the time of defrosting.

1 . A defrost system for a refrigeration apparatus in which a cooler having a casing, a fin-tube heat exchanger provided inside the casing, and a drain pan provided below the fin-tube heat exchanger is provided inside a cold storage room, comprising:
 a circulation line that is connected to the fin-tube heat exchanger of the cooler and circulates a CO2 refrigerant having a low temperature at a time of cooling; and   a refrigeration cycle that cools and reliquefies the CO2 refrigerant in a gaseous form with a refrigerant that circulates inside,   the defrost system including:   a thermosiphon defrost circuit that is provided by being branched from the circulation line, in which, at a time of defrosting, the CO2 refrigerant staying inside the fin-tube heat exchanger repeats a two-phase change of a gaseous form and reliquefaction, and which forms a CO2 circulation path together with the fin-tube heat exchanger;   an opening/closing valve that is closed at the time of defrosting and sets the CO2 circulation path to a closed circuit; and   a first electric heater arranged above the thermosiphon defrost circuit so as to be adjacent to the thermosiphon defrost circuit, and   naturally circulating the CO2 refrigerant in the closed circuit at the time of defrosting.   
     
     
         2 . The defrost system for the refrigeration apparatus according to  claim 1 , comprising:
 a pressure sensor that measures a pressure of the CO2 circulation path at the time of defrosting; and   a control portion that controls the first electric heater so that the pressure of the CO2 circulation path decreases when a measurement value measured by the pressure sensor is higher than a predetermined pressure.   
     
     
         3 . The defrost system for the refrigeration apparatus according to  claim 1 , further comprising a lower electric heater arranged at a lower part inside the casing. 
     
     
         4 . The defrost system for the refrigeration apparatus according to  claim 1 , wherein
 the thermosiphon defrost circuit includes:   a first line branched from the circulation line of the CO2 refrigerant;   a first header to which an end of the first line is connected;   a plurality of second lines that extends from the first header,   a second header to which the plurality of second lines is connected and which is provided at a position higher than the first header; and   a third line that extends from the second header and is connected to the circulation line, and   the plurality of second lines at least includes a line connecting most distant parts of the first header and the second header in a meander shape, and a line connecting closest parts of the first header and the second header in a meander shape.   
     
     
         5 . The defrost system for the refrigeration apparatus according to  claim 1 , further comprising a branch circuit provided by being branched from the circulation line, wherein
 on the branch circuit, a pressure adjusting valve that reduces a pressure when the pressure in the circulation line is higher than a predetermined pressure is arranged.