US20210262721A1 - Defrost system - Google Patents

Defrost system Download PDF

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Publication number
US20210262721A1
US20210262721A1 US16/982,326 US201916982326A US2021262721A1 US 20210262721 A1 US20210262721 A1 US 20210262721A1 US 201916982326 A US201916982326 A US 201916982326A US 2021262721 A1 US2021262721 A1 US 2021262721A1
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United States
Prior art keywords
refrigerant
circuit
defrost
heat exchanger
header
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Abandoned
Application number
US16/982,326
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English (en)
Inventor
Choiku Yoshikawa
Toshio KUTSUNA
Nelson MUGABI
Daiki KAYASHIMA
Nobuo OOSUGA
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Mayekawa Manufacturing Co
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Mayekawa Manufacturing Co
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Assigned to MAYEKAWA MFG. CO., LTD. reassignment MAYEKAWA MFG. CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KAYASHIMA, Daiki, KUTSUNA, Toshio, MUGABI, NELSON, OOSUGA, Nobuo, YOSHIKAWA, CHOIKU
Publication of US20210262721A1 publication Critical patent/US20210262721A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D17/00—Arrangements for circulating cooling fluids; Arrangements for circulating gas, e.g. air, within refrigerated spaces
    • F25D17/02—Arrangements for circulating cooling fluids; Arrangements for circulating gas, e.g. air, within refrigerated spaces for circulating liquids, e.g. brine
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B15/00—Sorption machines, plants or systems, operating continuously, e.g. absorption type
    • F25B15/02—Sorption machines, plants or systems, operating continuously, e.g. absorption type without inert gas
    • F25B15/04—Sorption machines, plants or systems, operating continuously, e.g. absorption type without inert gas the refrigerant being ammonia evaporated from aqueous solution
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
    • F25B25/005—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00 using primary and secondary systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/40—Fluid line arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
    • F25B47/02—Defrosting cycles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/002—Defroster control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/06—Removing frost
    • F25D21/08—Removing frost by electric heating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/01—Heaters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/25—Control of valves
    • F25B2600/2525—Pressure relief valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures

Definitions

  • the present invention relates to a defrost system applied to a refrigeration apparatus that cools the interior of a cold storage room by circulating a CO 2 refrigerant in a cooler provided in the cold storage room, and for removing frost attached to a fin-tube heat exchanger provided in the cooler.
  • a refrigeration apparatus in which, as a refrigerant of a refrigeration apparatus used for indoor air conditioning, refrigeration of food, and the like, ammonia that has high cooling performance but is toxic is used as a primary refrigerant and CO 2 that is non-toxic and odorless is used as a secondary refrigerant has widely been used.
  • a primary refrigerant circuit in which ammonia refrigerant circulates and a secondary refrigerant circuit in which CO 2 refrigerant circulates are connected by a cascade condenser, and heat is transferred between the ammonia refrigerant and the CO 2 refrigerant in the cascade condenser.
  • the CO 2 refrigerant cooled and liquefied by the ammonia refrigerant is sent to the cooler provided inside the cold storage room, and cools the air inside the cold storage room via the fin-tube heat exchanger provided inside the casing of the cooler.
  • the CO 2 refrigerant partially vaporized by cooling the air in the cold storage room returns to a CO 2 receiver via the secondary refrigerant circuit and is again cooled and liquefied by the cascade condenser.
  • frost forms on the heat exchange tube provided in the cooler and reduces the heat transfer efficiency, and therefore it is necessary to perform defrosting (frost removal).
  • a defrost system in which a defrost circuit (thermosiphon defrost circuit) and a warm brine circuit are installed and which includes a first heat exchanger for heating a CO 2 refrigerant circulating in the defrost circuit with warm brine is disclosed.
  • a CO 2 refrigerant liquid in a closed circuit drops by gravity to the first heat exchanger in the defrost circuit, and is heated and vaporized by the warm brine in the first heat exchanger.
  • the vaporized CO 2 refrigerant rises in the defrost circuit by the thermosiphon effect, and the risen CO 2 refrigerant gas heats and melts the frost attached to the outer surface of the fin-tube heat exchanger provided inside the cooler.
  • the CO 2 refrigerant that is liquefied by heating the fin-tube heat exchanger descends in the defrost circuit by gravity.
  • the CO 2 refrigerant liquid that has descended to the first heat exchanger is again heated and vaporized in the first heat exchanger.
  • the present invention was invented to solve the above problems, and an object is to provide a defrost system capable of preferable defrosting of a cooler and preventing icicles from being generated in a fin-tube heat exchanger at a lower part of a casing without having to install a warm brine circuit for heating a thermosiphon defrost circuit.
  • a defrost system for achieving the above object is 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, including a circulation line that is connected to the fin-tube heat exchanger of the cooler and circulates a CO 2 refrigerant having a low temperature at the time of cooling, and a refrigeration cycle that cools and reliquefies the CO 2 refrigerant in a gaseous form with a refrigerant that circulates inside.
  • the defrost system includes a thermosiphon defrost circuit that is provided by being branched from the circulation line, in which, at the time of defrosting, the CO 2 refrigerant staying inside the 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; an opening/closing valve that is closed at the time of defrosting and sets the CO 2 circulation path to a closed circuit; and a first electric heater arranged above a 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.
  • the CO 2 refrigerant liquid in the closed circuit drops by gravity to the first electric heater in the thermosiphon defrost circuit, and is heated and vaporized by the first electric heater.
  • the vaporized CO 2 refrigerant rises in the thermosiphon defrost circuit by the principle of thermosiphon, and the risen CO 2 refrigerant gas heats the fin-tube heat exchanger provided inside the cooler, and heats and melts the frost attached to the outer surface of the fin-tube heat exchanger.
  • the CO 2 refrigerant that is liquefied by heating the fin-tube heat exchanger descends in the thermosiphon defrost circuit by gravity.
  • the CO 2 refrigerant liquid that has descended to the first electric heater is heated and vaporized again by the first electric heater. From the above, it is possible to preferably perform defrosting of a cooler and prevent icicles from being generated in a fin-tube heat exchanger at a lower part of a casing without having to install a warm brine circuit for heating a thermosiphon defrost circuit.
  • FIG. 1 is an overall configuration diagram of a refrigeration apparatus according to the present embodiment.
  • FIG. 2 is a schematic perspective view of a cooler, a defrost system, and the like according to the present embodiment.
  • FIG. 3 is a schematic diagram of a cooler and a defrost system according to the present embodiment.
  • FIG. 4 is a sectional view taken along line 4 - 4 in FIG. 3 .
  • FIG. 5 is a sectional view taken along line 5 - 5 in FIG. 3 .
  • FIG. 6 is a schematic diagram showing a thermosiphon defrost circuit according to the present embodiment.
  • FIG. 7 is a diagram for explaining a circulation path of a CO 2 refrigerant at the time of defrosting.
  • FIG. 8A is a diagram showing a state in which an opening of a fan is close.
  • FIG. 8B is a diagram showing a state in which the opening of the fan is opened.
  • FIGS. 1 to 6 An embodiment of the present invention will be described with reference to FIGS. 1 to 6 . Note that, in the description of the drawings, the same elements will be denoted by the same reference symbols, and redundant description will be omitted. The dimensional ratios in the drawings are exaggerated for the sake of convenience of description, and may differ from the actual ratios.
  • FIG. 1 is an overall configuration diagram of a refrigeration apparatus 1 according to the present embodiment.
  • FIG. 2 is a schematic perspective view of a cooler 11 , a defrost system 20 , and the like according to the present embodiment.
  • FIG. 3 is a schematic diagram of the cooler 11 and the defrost system 20 according to the present embodiment.
  • FIG. 4 is a sectional view taken along line 4 - 4 in FIG. 3 .
  • FIG. 5 is a sectional view taken along line 5 - 5 in FIG. 3 .
  • FIG. 6 is a schematic diagram showing a thermosiphon defrost circuit 21 according to the present embodiment.
  • a refrigeration apparatus 1 includes a pair of coolers 11 provided in a cold storage room 10 , a defrost system 20 provided in the cooler 11 , a circulation line (secondary refrigerant circuit) 30 through which a CO 2 refrigerant circulates, a CO 2 receiver 40 for storing the CO 2 refrigerant, an ammonia refrigeration cycle 50 (refrigeration cycle) including a circulation line (primary refrigerant circuit) 56 in which an ammonia refrigerant circulates, a cooling water circuit 60 in which cooling water circulates, and a closed cooling tower 70 connected to the cooling water circuit 60 .
  • two coolers 11 are provided vertically. Since the configurations of the two coolers 11 are the mutually same configuration, and therefore the configuration of one cooler 11 will be described here.
  • the cooler 11 includes a casing 12 , a fin-tube heat exchanger 13 provided inside the casing 12 , and a fan 15 that forms an airflow that flows in and out of the casing 12 .
  • the casing 12 is configured in a substantially rectangular shape. Inside the casing 12 , the fin-tube heat exchanger 13 is arranged. Further, a second electric heater 23 is arranged below the lowermost part of the fin-tube heat exchanger 13 , and a third electric heater 24 is arranged below a dummy pipe L provided at the lowermost part of the casing 12 . The second electric heater 23 and the third electric heater 24 constitute a lower electric heater.
  • the dummy pipe L is provided to prevent bridges due to icicles of a drain pan 83 to be described below and a heat exchange tube 13 A of the fin-tube heat exchanger 13 and to ensure a uniform front wind speed, and the CO 2 refrigerant does not circulate.
  • the fin-tube heat exchanger 13 includes the heat exchange tube 13 A and fins 13 B as shown in FIGS. 2 and 3 .
  • the heat exchange tube 13 A is formed in a meander shape in a vertical direction and in a horizontal direction inside the casing 12 .
  • the fin 13 B is formed in the vertical direction as shown in FIG. 2 .
  • four heat exchange tubes 13 A are provided along a depth direction of the casing 12 . Note that the configuration of the heat exchange tube 13 A is not limited thereto as long as it is evenly arranged inside the casing 12 .
  • the four heat exchange tubes 13 A are coupled to an inlet header 16 at a lower end of the four heat exchange tubes 13 A. Further, as shown in FIG. 3 , the four heat exchange tubes 13 A are coupled to an outlet header 17 at an upper end of the four heat exchange tubes 13 A.
  • the fan 15 is arranged above the casing 12 as shown in FIG. 1 . Note that the position where the fan 15 is provided may be a side surface of the casing 12 , or the like. When the fan 15 operates, an airflow that flows in and out of the casing 12 is formed.
  • the defrost system 20 is provided for melting and removing (defrosting) frost attached to a surface of the fin-tube heat exchanger 13 . As shown in FIGS. 1 to 5 , the defrost system 20 includes the thermosiphon defrost circuit 21 , a first electric heater 22 , the second electric heater 23 , and the third electric heater 24 .
  • thermosiphon defrost circuit 21 is provided by being branched from a CO 2 feed line 31 of the circulation line 30 , and forms a CO 2 circulation path together with the fin-tube heat exchanger 13 . Further, a heat collection portion of the thermosiphon defrost circuit 21 is arranged below the first electric heater 22 .
  • thermosiphon defrost circuit 21 an electromagnetic opening/closing valve 21 A and a check valve 21 J are arranged.
  • the thermosiphon defrost circuit 21 closes electromagnetic opening/closing valves 34 A and 34 B, which will be described below, and opens the electromagnetic opening/closing valve 21 A to form the CO 2 circulation path through which CO 2 circulates.
  • the thermosiphon defrost circuit 21 opens the electromagnetic opening/closing valves 34 A and 34 B and closes the electromagnetic opening/closing valve 21 A at the time of a refrigerating operation.
  • thermosiphon defrost circuit 21 The configuration of the thermosiphon defrost circuit 21 will be described below in detail with reference to FIGS. 3 and 6 .
  • the thermosiphon defrost circuit 21 includes a first line 21 B branched from the CO 2 feed line 31 of the circulation line 30 , a first header 21 C to which an end of the first line 21 B is connected, three second lines 21 D, 21 E, 21 F extending from the first header 21 C, a second header 21 G to which the three second lines 21 D, 21 E, 21 F are coupled and which is provided at a position higher than the first header 21 C, and a third line 21 H extending from the second header 21 G and connected to a CO 2 return line 32 of the circulation line 30 .
  • the three second lines 21 D, 21 E, 21 F include the second line 21 D connecting the most distant parts of the first header 21 C and the second header 21 G in a meander shape, the second line 21 E connecting the closest parts of the first header 21 C and the second header 21 G in a meander shape, and the second line 21 F arranged between the second line 21 D and the second line 21 E.
  • the three second lines 21 D, 21 E, 21 F are arranged in an upward inclination without crossing each other, and therefore, in the three second lines 21 D, 21 E, 21 F, CO 2 can be circulated preferably.
  • the first electric heater 22 is arranged below the drain pan 83 described below and above the three second lines 21 D, 21 E, 21 F. As shown in FIG. 2 , the first electric heater 22 is configured such that six heaters have a U shape.
  • the output per heater is not particularly limited, but is 1.5 kW.
  • the second electric heater 23 is, as shown in FIGS. 1, 2, and 5 , arranged below the fin-tube heat exchanger 13 inside the casing 12 .
  • the second electric heater 23 is arranged below the heat exchange tube 13 A and above the dummy pipe L.
  • the output of one heater is not particularly limited, but is 1.5 kW. Since the second electric heater 23 is arranged below the fin-tube heat exchanger 13 inside the casing as described above, water droplets descending the fin-tube heat exchanger 13 can be recovered by the drain pan 83 without being refrozen to be icicles at the fin-tube heat exchanger 13 at a lower part of the casing 12 .
  • the third electric heater 24 is, as shown in FIG. 5 , arranged below the dummy pipe L. That is, the third electric heater 24 is arranged at the lowermost part inside the casing 12 . Since the third electric heater 24 is arranged at the lowermost part inside the casing 12 , it is possible to preferably prevent refreezing at a lower part of the casing 12 to generate icicles.
  • a heat insulating material 81 is provided below the thermosiphon defrost circuit 21 .
  • the thickness of the heat insulating material 81 is not particularly limited, but is, for example, 20 mm, and prevents heat radiation loss from the lower surface of the thermosiphon defrost circuit 21 heated by the first electric heater 22 .
  • the drain pan 83 is provided above the first electric heater 22 , and water droplets at the time of defrosting can be drained from a drain discharge pipe 83 A without refreezing.
  • a heat transfer plate 82 is provided between the thermosiphon defrost circuit 21 and the first electric heater 22 . By providing the heat transfer plate 82 in this way, the heat of the first electric heater 22 can be appropriately transferred to the heating of the CO 2 refrigerant.
  • the circulation line 30 is configured to circulate the CO 2 refrigerant.
  • the circulation line 30 includes the CO 2 feed line 31 for feeding the CO 2 refrigerant in a liquid form to the pair of cold storage rooms 10 from the CO 2 receiver 40 , the CO 2 return line 32 for returning a gas-liquid mixed CO 2 refrigerant coming out of the pair of cold storage rooms 10 to the CO 2 receiver 40 , and a reliquefaction line 33 for reliquefying the gasified CO 2 refrigerant.
  • the CO 2 feed line 31 is, as shown in FIG. 1 , connected to a lower part of the CO 2 receiver 40 .
  • the CO 2 return line 32 is, as shown in FIG. 1 , connected to an upper part of the CO 2 receiver 40 .
  • a first pump P 1 is provided in the CO 2 feed line 31 , and the CO 2 refrigerant in a liquid form in the CO 2 receiver 40 is fed to the cooler 11 in the cold storage room 10 by the first pump P 1 .
  • the CO 2 feed line 31 is branched into a first feed line 31 A connected to one cooler 11 and a second feed line 31 B connected to the other cooler 11 .
  • the first feed line 31 A is connected to a first return line 32 A via the one cooler 11 . Further, the second feed line 31 B is connected to a second return line 32 B via the other cooler 11 . The first return line 32 A and the second return line 32 B join again and are coupled to the CO 2 return line 32 .
  • the first feed line 31 A is, as shown in FIGS. 1 and 3 , connected to the inlet header 16 , and the first return line 32 A is connected to the outlet header 17 .
  • an electromagnetic opening/closing valve (opening/closing valve) 34 A is arranged in the first feed line 31 A
  • an electromagnetic opening/closing valve (opening/closing valve) 34 B is arranged in the first return line 32 A.
  • a pressure sensor 34 is connected to the first return line 32 A.
  • a control portion 35 to which a detection value of the pressure sensor 34 is input is connected to the pressure sensor 34 .
  • a controller 36 of the first electric heater 22 is connected to the control portion 35 , and the control portion 35 can control the temperature of the first electric heater 22 and ON/OFF of the six heaters.
  • control portion 35 can reduce the temperature of the first electric heater 22 or reduce the number of heaters of the first electric heater 22 among the six heaters to be turned on when the pressure of the CO 2 circulation path measured by the pressure sensor 34 is higher than a predetermined pressure.
  • the first return line 32 A is provided with a branch circuit 37 that branches from the first return line 32 A, the branch circuit 37 is provided with a pressure adjusting valve 38 , and when the pressure is higher than a predetermined pressure, the pressure adjusting valve 38 is opened to reduce the pressure.
  • the reliquefaction line 33 is connected an upper part of the CO 2 receiver 40 .
  • the CO 2 refrigerant in a gaseous form in the CO 2 receiver 40 is reliquefied by a heat exchanger 51 of the ammonia refrigeration cycle 50 described below. Then, the reliquefied CO 2 refrigerant in a liquid form returns to the CO 2 receiver 40 .
  • the ammonia refrigeration cycle 50 circulates the ammonia refrigerant.
  • the ammonia refrigeration cycle 50 cools and liquefies the CO 2 refrigerant in a gaseous form.
  • the ammonia refrigeration cycle 50 includes the heat exchanger (cascade condenser) 51 as an evaporator, a refrigeration compressor 52 , a condenser 53 , an ammonia receiver 54 , an expansion valve 55 , and the circulation line (primary refrigerant circuit) 56 through which the ammonia refrigerant circulates.
  • the ammonia refrigerant gas evaporated by the heat of the CO 2 refrigerant in a gaseous form in the heat exchanger 51 is compressed by the refrigeration compressor 52 , the high temperature and high pressure ammonia refrigerant gas is cooled and condensed in the condenser 53 , the liquefied ammonia refrigerant liquid is stored in the ammonia receiver 54 , the ammonia refrigerant liquid in the ammonia receiver 54 is fed to and expanded by the expansion valve 55 , and the low-pressure ammonia refrigerant liquid is fed to the heat exchanger 51 and is used for cooling CO 2 refrigerant in a gaseous form.
  • the cooling water circuit 60 is installed on the condenser 53 .
  • the cooling water circulating in the cooling water circuit 60 is heated by the ammonia refrigerant in the condenser 53 .
  • the cooling water circuit 60 is connected to the closed cooling tower 70 .
  • the cooling water is circulated in the cooling water circuit 60 by a cooling water pump 61 .
  • the cooling water that has absorbed the exhaust heat of the ammonia refrigerant in the condenser comes into contact with the outside air and spray water in the closed cooling tower 70 , and is cooled by the latent heat of vaporization of the spray water.
  • the closed cooling tower 70 includes a cooling coil 71 connected to the cooling water circuit 60 , a fan 72 for ventilating outside air a through the cooling coil 71 , a sprinkling pipe 73 and a pump 74 for spraying the cooling water on the cooling coil 71 .
  • a part of the cooling water sprayed from the sprinkling pipe 73 evaporates, and the latent heat of vaporization is used to cool the cooling water flowing through the cooling coil 71 .
  • the configuration of the refrigeration apparatus 1 has been described heretofore. Next, with reference to FIGS. 1, 7, and 8 , a method of using the refrigeration apparatus 1 according to the present embodiment will be described separately for the refrigerating operation and the defrosting.
  • FIG. 1 is a diagram showing a circulation path of a CO 2 refrigerant at the time of a refrigerating operation.
  • the electromagnetic opening/closing valves 34 A and 34 B are opened and the electromagnetic opening/closing valve 21 A is closed.
  • the CO 2 refrigerant supplied from the CO 2 feed line 31 circulates through the first feed line 31 A, the second feed line 31 B, and the fin-tube heat exchanger 13 .
  • the fan 15 inside the cold storage room 10 a circulating flow of the inside air passing through the inside of the cooler 11 is formed.
  • the inside air is cooled by the CO 2 refrigerant circulating through the fin-tube heat exchanger 13 , and the inside of the cold storage room 10 is kept at a low temperature of ⁇ 25° C., for example.
  • the fan 15 is operated to open a sock duct.
  • FIG. 7 is a diagram showing a circulation path of a CO 2 refrigerant at the time of defrosting.
  • the electromagnetic opening/closing valves 34 A and 34 B are closed and the electromagnetic opening/closing valve 21 A is opened. This forms a closed CO 2 circulation path including the fin-tube heat exchanger 13 and the thermosiphon defrost circuit 21 .
  • the CO 2 refrigerant liquid in the closed circuit drops by gravity in the thermosiphon defrost circuit 21 to the first header 21 C and the three second lines 21 D, 21 E, 21 F extending from the first header 21 C, is heated and vaporized by the first electric heater 22 .
  • the vaporized CO 2 refrigerant rises in the check valve 21 J of the thermosiphon defrost circuit 21 by the principle of thermosiphon, and the risen CO 2 refrigerant gas heats and melts the frost attached to the outer surface of the fin-tube heat exchanger 13 provided inside the cooler 11 .
  • the CO 2 refrigerant that is liquefied by heating the fin-tube heat exchanger 13 descends in the thermosiphon defrost circuit 21 by gravity.
  • the CO 2 refrigerant liquid that has descended to the first header 21 C and the three second lines 21 D, 21 E, 21 F extending from the first header 21 C is again heated and vaporized by the first electric heater 22 .
  • the melt water obtained as the frost is heated and melted falls toward the drain pan 83 .
  • the second electric heater 23 is not provided, there is a possibility that icicles are formed as refreezing occurs below the fin-tube heat exchanger 13 .
  • the defrost system 20 according to the present embodiment since the second electric heater 23 and the third electric heater 24 are provided at the lowermost part inside the casing 12 , it is possible to prevent icicles from being formed below the casing 12 . Further, at the time of defrosting, as shown in FIG.
  • an opening of the fan 15 is closed by the sock duct to assist the temperature rise in the cooler 11 and prevent the generation of fog in the cold storage room 10 .
  • the configuration in which the second electric heater 23 is not provided is also included in the present invention.
  • the cooler 11 including the casing 12 , the fin-tube heat exchanger 13 provided inside the casing 12 , and the drain pan 83 provided below the fin-tube heat exchanger 13 is provided inside the cold storage room 10 .
  • the defrost system 20 includes the thermosiphon defrost circuit 21 that is provided by being branched from the circulation line 30 , in which, at the time of defrosting, the CO 2 refrigerant staying inside the fin-tube heat exchanger 13 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 13 ; the opening/closing valves 34 A and 34 B that are closed at the time of defrosting and sets the CO 2 circulation path to a closed circuit; and the first electric heater 22 arranged above the thermosiphon defrost circuit 21 so as to be adjacent to the thermosiphon defrost circuit 21 .
  • the CO 2 refrigerant is naturally circulated in the closed circuit at the time of defrosting.
  • the CO 2 refrigerant liquid in the closed circuit is heated and vaporized by the first electric heater 22 , and rises in the thermosiphon defrost circuit 21 by the principle of thermosiphon, the risen CO 2 refrigerant gas heats the fin-tube heat exchanger 13 provided inside the cooler 11 , and heats and melts the frost attached to the outer surface of the fin-tube heat exchanger 13 .
  • the CO 2 refrigerant that is liquefied by heating the fin-tube heat exchanger 13 descends in the thermosiphon defrost circuit 21 by gravity.
  • the CO 2 refrigerant liquid that has descended to the first electric heater 22 is heated and vaporized by the first electric heater 22 .
  • the second electric heater 23 is provided at a lower part inside the casing 12 , water droplets descending the fin-tube heat exchanger 13 can be recovered in the drain pan 83 without being refrozen to be icicles in the fin-tube heat exchanger 13 at a lower part of the casing 12 . From the above, it is possible to preferably perform defrosting without installing a brine circuit, and it is possible to prevent the generation of icicles on the heat exchange tubes 13 A and the fins 13 B at a lower part of the casing 12 .
  • the defrost system 20 includes the pressure sensor 34 for measuring the pressure of the CO 2 circulation path at the time of defrosting, and the control portion 35 that controls the first electric heater 22 such that the pressure of the CO 2 circulation path decreases when the measurement value measured by the pressure sensor 34 is higher than a predetermined pressure.
  • thermosiphon defrost circuit 21 includes the first line 21 B branched from the CO 2 feed line 31 of the circulation line 30 of the CO 2 refrigerant, the first header 21 C to which an end of the first line 21 B is connected, the three second lines 21 D, 21 E, 21 F extending from the first header 21 C, the second header 21 G to which the three second lines 21 D, 21 E, 21 F are connected and which is provided at a position higher than the first header 21 C, and the third line 21 H extending from the second header 21 G and connected to the CO 2 return line 32 of the circulation line 30 .
  • the three second lines 21 D, 21 E, 21 F include the second line 21 D connecting the most distant parts of the first header 21 C and the second header 21 G in a meander shape, the second line 21 E connecting the closest parts of the first header 21 C and the second header 21 G in a meander shape, and the second line 21 F arranged between the second line 21 D and the second line 21 E.
  • the three second lines 21 D, 21 E, 21 F which are arranged without crossing one another, can be preferably heated by the first electric heater 22 via the heat transfer plate 82 , the CO 2 refrigerant can be naturally circulated.
  • the defrost system 20 configured in this way, at the time of defrosting, it can be performed only by the first electric heater 22 that heats and naturally circulates the CO 2 refrigerant remaining in the pipes of the thermosiphon defrost circuit 21 and the fin-tube heat exchanger 13 and enables heating and draining of the drain pan 83 and the second electric heater 23 for preventing re-freezing at the fin-tube heat exchanger 13 at a lower part of the casing 12 (the third electric heater 24 if the dummy pipe L is present), and therefore it is possible to perform defrosting with very little electric power as compared with heater defrost in which heaters are evenly arranged in the arrangement of the fin-tube heat exchanger 13 . Further, since the fin-tube heat exchanger 13 is directly heated, the delay in starting the defrosting can be eliminated.
  • thermosiphon defrost circuit 21 and the fin-tube heat exchanger 13 are arranged on the branch circuit 37 .
  • the pressure adjusting valve 38 for reducing the pressure when the pressure in the circulation line 30 is higher than a predetermined pressure is arranged.
  • thermosiphon defrost circuit 21 includes the first line 21 B branched from the circulation line 30 , the first header 21 C to which an end of the first line 21 B is connected, the three second lines 21 D, 21 E, 21 F extending from the first header 21 C, the second header 21 G to which the three second lines 21 D, 21 E, 21 F are coupled, and the third line 21 H extending from the second header 21 G and connected to the circulation line 30 , but is not particularly limited as long as it is configured to form the CO 2 circulation path together with the fin-tube heat exchanger 13 .
  • the three second lines 21 D, 21 E, 21 F are provided, but two or more may be provided.
  • ammonia is used as the refrigerant of the refrigeration cycle, but it is not limited thereto, but chlorofluorocarbon or other natural refrigerants may be used.
  • the two coolers 11 are provided, but one or three or more coolers 11 may be provided.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Defrosting Systems (AREA)
US16/982,326 2019-07-22 2019-07-22 Defrost system Abandoned US20210262721A1 (en)

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JP6912673B2 (ja) 2021-08-04
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CN113631876B (zh) 2023-10-27
US20230127825A1 (en) 2023-04-27
WO2021014526A1 (ja) 2021-01-28
EP4006451A1 (en) 2022-06-01
JPWO2021014526A1 (ja) 2021-09-13
KR102406789B1 (ko) 2022-06-10
MX2021011453A (es) 2021-10-13
EP4006451A4 (en) 2022-08-10
KR20210013005A (ko) 2021-02-03

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