Patent Description:
From the viewpoint of preventing ozone layer depletion, preventing global warming, and the like, 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<NUM> that is non-toxic and odorless is used as a secondary refrigerant has widely been used.

In such a refrigeration apparatus, a primary refrigerant circuit in which ammonia refrigerant circulates and a secondary refrigerant circuit in which CO<NUM> refrigerant circulates are connected by a cascade condenser, and heat is transferred between the ammonia refrigerant and the CO<NUM> refrigerant in the cascade condenser. The CO<NUM> 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<NUM> refrigerant partially vaporized by cooling the air in the cold storage room returns to a CO<NUM> receiver via the secondary refrigerant circuit and is again cooled and liquefied by the cascade condenser.

During operation of the refrigeration apparatus, 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).

In this regard, for example, in <CIT> X below, 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<NUM> refrigerant circulating in the defrost circuit with warm brine is disclosed. With the defrost system configured as described above, a CO<NUM> 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<NUM> refrigerant rises in the defrost circuit by the thermosiphon effect, and the risen CO<NUM> refrigerant gas heats and melts the frost attached to the outer surface of the fin-tube heat exchanger provided inside the cooler. The CO<NUM> refrigerant that is liquefied by heating the fin-tube heat exchanger descends in the defrost circuit by gravity. The CO<NUM> refrigerant liquid that has descended to the first heat exchanger is again heated and vaporized in the first heat exchanger.

<CIT> discloses a cooling system in which a first refrigerating circuit through which a first refrigerant circulates and a second refrigerating circuit through which a second refrigerant circulates are combined.

<CIT> discloses a refrigerator which can defrost an evaporator; in the refrigerator, a defrosting heater is turned on at regular intervals, thereby defrosting the evaporator. Under a heat-transfer member, a drain plate is provided to catch water produced when the evaporator is defrosted; on the back of the drain plate is provided the defrosting heater.

A refrigeration apparatus according to the preamble of claim <NUM> of the present invention is disclosed in <CIT>.

For a better understanding of the present invention, it is further referred to <CIT> and to <CIT>.

In the defrost system disclosed in <CIT> X, since the warm brine circuit is installed, a warm brine facility becomes bulky and the concentration control of the warm brine is required.

On the other hand, it is important to prevent icicles from forming in the lower part of the cooler by melting water flowing from the upper part of the cooler during defrosting.

The present invention was invented to solve the above problems, and an object is to provide a refrigeration apparatus comprising 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.

The object is achieved by a refrigeration apparatus having the features of claim <NUM>. Advantageous embodiments of the invention are laid out in the dependent claims.

A refrigeration apparatus according to the present invention for achieving the above object is 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<NUM> refrigerant having a low temperature at the time of cooling, and a refrigeration cycle that cools and reliquefies the CO<NUM> refrigerant in a gaseous form with a refrigerant that circulates inside. The refrigeration apparatus comprises a defrost system that includes a thermosiphon defrost circuit that is provided by being branched from the circulation line, in which, at the time of defrosting, the CO<NUM> refrigerant staying inside the fin-tube heat exchanger repeats a two-phase change of a gaseous form and reliquefaction, and which forms a CO<NUM> 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<NUM> 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<NUM> refrigerant in the closed circuit at the time of defrosting. The refrigeration apparatus is characterized in that the thermosiphon defrost circuit includes: a first line branched from the circulation line (<NUM>) of the CO<NUM> 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.

With the defrost system configured as described above, the CO<NUM> 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<NUM> refrigerant rises in the thermosiphon defrost circuit by the principle of thermosiphon, and the risen CO<NUM> 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<NUM> refrigerant that is liquefied by heating the fin-tube heat exchanger descends in the thermosiphon defrost circuit by gravity. The CO<NUM> 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.

An embodiment of the present invention will be described with reference to <FIG>. 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> is an overall configuration diagram of a refrigeration apparatus <NUM> according to the present embodiment. <FIG> is a schematic perspective view of a cooler <NUM>, a defrost system <NUM>, and the like according to the present embodiment. <FIG> is a schematic diagram of the cooler <NUM> and the defrost system <NUM> according to the present embodiment. <FIG> is a sectional view taken along line <NUM>-<NUM> in <FIG>. <FIG> is a sectional view taken along line <NUM>-<NUM> in <FIG>. <FIG> is a schematic diagram showing a thermosiphon defrost circuit <NUM> according to the present embodiment.

As shown in <FIG>, a refrigeration apparatus <NUM> includes a pair of coolers <NUM> provided in a cold storage room <NUM>, a defrost system <NUM> provided in the cooler <NUM>, a circulation line (secondary refrigerant circuit) <NUM> through which a CO<NUM> refrigerant circulates, a CO<NUM> receiver <NUM> for storing the CO<NUM> refrigerant, an ammonia refrigeration cycle <NUM> (refrigeration cycle) including a circulation line (primary refrigerant circuit) <NUM> in which an ammonia refrigerant circulates, a cooling water circuit <NUM> in which cooling water circulates, and a closed cooling tower <NUM> connected to the cooling water circuit <NUM>.

In the cold storage room <NUM>, as shown in <FIG>, two coolers <NUM> are provided vertically. Since the configurations of the two coolers <NUM> are the mutually same configuration, and therefore the configuration of one cooler <NUM> will be described here.

As shown in <FIG>, the cooler <NUM> includes a casing <NUM>, a fin-tube heat exchanger <NUM> provided inside the casing <NUM>, and a fan <NUM> that forms an airflow that flows in and out of the casing <NUM>.

As shown in <FIG>, the casing <NUM> is configured in a substantially rectangular shape. Inside the casing <NUM>, the fin-tube heat exchanger <NUM> is arranged. Further, a second electric heater <NUM> is arranged below the lowermost part of the fin-tube heat exchanger <NUM>, and a third electric heater <NUM> is arranged below a dummy pipe L provided at the lowermost part of the casing <NUM>. The second electric heater <NUM> and the third electric heater <NUM> constitute a lower electric heater. The dummy pipe L is provided to prevent bridges due to icicles of a drain pan <NUM> to be described below and a heat exchange tube 13A of the fin-tube heat exchanger <NUM> and to ensure a uniform front wind speed, and the CO<NUM> refrigerant does not circulate.

The fin-tube heat exchanger <NUM> includes the heat exchange tube 13A and fins 13B as shown in <FIG> and <FIG>. As shown in <FIG>, the heat exchange tube 13A is formed in a meander shape in a vertical direction and in a horizontal direction inside the casing <NUM>. The fin 13B is formed in the vertical direction as shown in <FIG>. Further, as shown in <FIG>, four heat exchange tubes 13A are provided along a depth direction of the casing <NUM>. Note that the configuration of the heat exchange tube 13A is not limited thereto as long as it is evenly arranged inside the casing <NUM>.

As shown in <FIG>, the four heat exchange tubes 13A are coupled to an inlet header <NUM> at a lower end of the four heat exchange tubes 13A. Further, as shown in <FIG>, the four heat exchange tubes 13A are coupled to an outlet header <NUM> at an upper end of the four heat exchange tubes 13A.

The fan <NUM> is arranged above the casing <NUM> as shown in <FIG>. Note that the position where the fan <NUM> is provided may be a side surface of the casing <NUM>, or the like. When the fan <NUM> operates, an airflow that flows in and out of the casing <NUM> is formed.

The defrost system <NUM> is provided for melting and removing (defrosting) frost attached to a surface of the fin-tube heat exchanger <NUM>. As shown in <FIG>, the defrost system <NUM> includes the thermosiphon defrost circuit <NUM>, a first electric heater <NUM>, the second electric heater <NUM>, and the third electric heater <NUM>.

As shown in <FIG>, the thermosiphon defrost circuit <NUM> is provided by being branched from a CO<NUM> feed line <NUM> of the circulation line <NUM>, and forms a CO<NUM> circulation path together with the fin-tube heat exchanger <NUM>. Further, a heat collection portion of the thermosiphon defrost circuit <NUM> is arranged below the first electric heater <NUM>.

As shown in <FIG> and <FIG>, in the thermosiphon defrost circuit <NUM>, an electromagnetic opening/closing valve 21A and a check valve 21J are arranged. At the time of defrosting, the thermosiphon defrost circuit <NUM> closes electromagnetic opening/closing valves 34A and 34B, which will be described below, and opens the electromagnetic opening/closing valve 21A to form the CO<NUM> circulation path through which CO<NUM> circulates. On the other hand, the thermosiphon defrost circuit <NUM> opens the electromagnetic opening/closing valves 34A and 34B and closes the electromagnetic opening/closing valve 21A at the time of a refrigerating operation.

The configuration of the thermosiphon defrost circuit <NUM> will be described below in detail with reference to <FIG> and <FIG>.

As shown in <FIG> and <FIG>, the thermosiphon defrost circuit <NUM> includes a first line 21B branched from the CO<NUM> feed line <NUM> of the circulation line <NUM>, a first header 21C to which an end of the first line 21B is connected, three second lines 21D, 21E, 21F extending from the first header 21C, a second header <NUM> to which the three second lines 21D, 21E, 21F are coupled and which is provided at a position higher than the first header 21C, and a third line <NUM> extending from the second header <NUM> and connected to a CO<NUM> return line <NUM> of the circulation line <NUM>.

The three second lines 21D, 21E, 21F, as shown in <FIG>, include the second line 21D connecting the most distant parts of the first header 21C and the second header <NUM> in a meander shape, the second line 21E connecting the closest parts of the first header 21C and the second header <NUM> in a meander shape, and the second line 21F arranged between the second line 21D and the second line 21E. With this configuration, the three second lines 21D, 21E, 21F are arranged in an upward inclination without crossing each other, and therefore, in the three second lines 21D, 21E, 21F, CO<NUM> can be circulated preferably.

As shown in <FIG>, <FIG>, and <FIG>, the first electric heater <NUM> is arranged below the drain pan <NUM> described below and above the three second lines 21D, 21E, 21F. As shown in <FIG>, the first electric heater <NUM> is configured such that six heaters have a U shape. The output per heater is not particularly limited, but is <NUM> kW.

The second electric heater <NUM> is, as shown in <FIG>, <FIG>, and <FIG>, arranged below the fin-tube heat exchanger <NUM> inside the casing <NUM>. Specifically, as shown in <FIG>, the second electric heater <NUM> is arranged below the heat exchange tube 13A and above the dummy pipe L. The output of one heater is not particularly limited, but is <NUM> kW. Since the second electric heater <NUM> is arranged below the fin-tube heat exchanger <NUM> inside the casing <NUM> as described above, water droplets descending the fin-tube heat exchanger <NUM> can be recovered by the drain pan <NUM> without being refrozen to be icicles at the fin-tube heat exchanger <NUM> at a lower part of the casing <NUM>.

The third electric heater <NUM> is, as shown in <FIG>, arranged below the dummy pipe L. That is, the third electric heater <NUM> is arranged at the lowermost part inside the casing <NUM>. Since the third electric heater <NUM> is arranged at the lowermost part inside the casing <NUM>, it is possible to preferably prevent refreezing at a lower part of the casing <NUM> to generate icicles.

As shown in <FIG> and <FIG>, a heat insulating material <NUM> is provided below the thermosiphon defrost circuit <NUM>. The thickness of the heat insulating material <NUM> is not particularly limited, but is, for example, <NUM>, and prevents heat radiation loss from the lower surface of the thermosiphon defrost circuit <NUM> heated by the first electric heater <NUM>. The drain pan <NUM> is provided above the first electric heater <NUM>, and water droplets at the time of defrosting can be drained from a drain discharge pipe 83A without refreezing. Further, between the thermosiphon defrost circuit <NUM> and the first electric heater <NUM>, a heat transfer plate <NUM> is provided. By providing the heat transfer plate <NUM> in this way, the heat of the first electric heater <NUM> can be appropriately transferred to the heating of the CO<NUM> refrigerant.

The circulation line <NUM> is configured to circulate the CO<NUM> refrigerant. The circulation line <NUM>, as shown in <FIG>, includes the CO<NUM> feed line <NUM> for feeding the CO<NUM> refrigerant in a liquid form to the pair of cold storage rooms <NUM> from the CO<NUM> receiver <NUM>, the CO<NUM> return line <NUM> for returning a gas-liquid mixed CO<NUM> refrigerant coming out of the pair of cold storage rooms <NUM> to the CO<NUM> receiver <NUM>, and a reliquefaction line <NUM> for relique-fying the gasified CO<NUM> refrigerant.

The CO<NUM> feed line <NUM> is, as shown in <FIG>, connected to a lower part of the CO<NUM> receiver <NUM>. Further, the CO<NUM> return line <NUM> is, as shown in <FIG>, connected to an upper part of the CO<NUM> receiver <NUM>.

Further, a first pump P1 is provided in the CO<NUM> feed line <NUM>, and the CO<NUM> refrigerant in a liquid form in the CO<NUM> receiver <NUM> is fed to the cooler <NUM> in the cold storage room <NUM> by the first pump P1.

As shown in <FIG>, the CO<NUM> feed line <NUM> is branched into a first feed line 31A connected to one cooler <NUM> and a second feed line 31B connected to the other cooler <NUM>.

The first feed line 31A is connected to a first return line 32A via the one cooler <NUM>. Further, the second feed line 31B is connected to a second return line 32B via the other cooler <NUM>. The first return line 32A and the second return line 32B join again and are coupled to the CO<NUM> return line <NUM>.

The first feed line 31A is, as shown in <FIG> and <FIG>, connected to the inlet header <NUM>, and the first return line 32A is connected to the outlet header <NUM>. As shown in <FIG>, an electromagnetic opening/closing valve (opening/closing valve) 34A is arranged in the first feed line 31A, and an electromagnetic opening/closing valve (opening/closing valve) 34B is arranged in the first return line 32A.

As shown in <FIG>, a pressure sensor <NUM> is connected to the first return line 32A. A control portion <NUM> to which a detection value of the pressure sensor <NUM> is input is connected to the pressure sensor <NUM>. Further, a controller <NUM> of the first electric heater <NUM> is connected to the control portion <NUM>, and the control portion <NUM> can control the temperature of the first electric heater <NUM> and ON/OFF of the six heaters.

At the time of defrosting, the control portion <NUM> can reduce the temperature of the first electric heater <NUM> or reduce the number of heaters of the first electric heater <NUM> among the six heaters to be turned on when the pressure of the CO<NUM> circulation path measured by the pressure sensor <NUM> is higher than a predetermined pressure.

Further, the first return line 32A is provided with a branch circuit <NUM> that branches from the first return line 32A, the branch circuit <NUM> is provided with a pressure adjusting valve <NUM>, and when the pressure is higher than a predetermined pressure, the pressure adjusting valve <NUM> is opened to reduce the pressure.

The reliquefaction line <NUM> is connected an upper part of the CO<NUM> receiver <NUM>. When passing through the reliquefaction line <NUM>, the CO<NUM> refrigerant in a gaseous form in the CO<NUM> receiver <NUM> is reliquefied by a heat exchanger <NUM> of the ammonia refrigeration cycle <NUM> described below. Then, the reliquefied CO<NUM> refrigerant in a liquid form returns to the CO<NUM> receiver <NUM>.

The ammonia refrigeration cycle <NUM> circulates the ammonia refrigerant. The ammonia refrigeration cycle <NUM> cools and liquefies the CO<NUM> refrigerant in a gaseous form. As shown in <FIG>, the ammonia refrigeration cycle <NUM> includes the heat exchanger (cascade condenser) <NUM> as an evaporator, a refrigeration compressor <NUM>, a condenser <NUM>, an ammonia receiver <NUM>, an expansion valve <NUM>, and the circulation line (primary refrigerant circuit) <NUM> through which the ammonia refrigerant circulates.

The ammonia refrigerant gas evaporated by the heat of the CO<NUM> refrigerant in a gaseous form in the heat exchanger <NUM> is compressed by the refrigeration compressor <NUM>, the high temperature and high pressure ammonia refrigerant gas is cooled and condensed in the condenser <NUM>, the liquefied ammonia refrigerant liquid is stored in the ammonia receiver <NUM>, the ammonia refrigerant liquid in the ammonia receiver <NUM> is fed to and expanded by the expansion valve <NUM>, and the low-pressure ammonia refrigerant liquid is fed to the heat exchanger <NUM> and is used for cooling CO<NUM> refrigerant in a gaseous form.

The cooling water circuit <NUM> is installed on the condenser <NUM>. The cooling water circulating in the cooling water circuit <NUM> is heated by the ammonia refrigerant in the condenser <NUM>.

The cooling water circuit <NUM> is connected to the closed cooling tower <NUM>. The cooling water is circulated in the cooling water circuit <NUM> by a cooling water pump <NUM>. The cooling water that has absorbed the exhaust heat of the ammonia refrigerant in the condenser <NUM> comes into contact with the outside air and spray water in the closed cooling tower <NUM>, and is cooled by the latent heat of vaporization of the spray water.

The closed cooling tower <NUM> includes a cooling coil <NUM> connected to the cooling water circuit <NUM>, a fan <NUM> for ventilating outside air a through the cooling coil <NUM>, a sprinkling pipe <NUM> and a pump <NUM> for spraying the cooling water on the cooling coil <NUM>. A part of the cooling water sprayed from the sprinkling pipe <NUM> evaporates, and the latent heat of vaporization is used to cool the cooling water flowing through the cooling coil <NUM>.

The configuration of the refrigeration apparatus <NUM> has been described heretofore. Next, with reference to <FIG>, <FIG>, and <FIG>, a method of using the refrigeration apparatus <NUM> according to the present embodiment will be described separately for the refrigerating operation and the defrosting.

<FIG> is a diagram showing a circulation path of a CO<NUM> refrigerant at the time of a refrigerating operation. At the time of the refrigerating operation, the electromagnetic opening/closing valves 34A and 34B are opened and the electromagnetic opening/closing valve 21A is closed. Thus, the CO<NUM> refrigerant supplied from the CO<NUM> feed line <NUM> circulates through the first feed line 31A, the second feed line 31B, and the fin-tube heat exchanger <NUM>. On the other hand, by the operation of the fan <NUM> inside the cold storage room <NUM>, a circulating flow of the inside air passing through the inside of the cooler <NUM> is formed. The inside air is cooled by the CO<NUM> refrigerant circulating through the fin-tube heat exchanger <NUM>, and the inside of the cold storage room <NUM> is kept at a low temperature of -<NUM>, for example. At the time of the refrigerating operation, as shown in <FIG>, the fan <NUM> is operated to open a sock duct.

<FIG> is a diagram showing a circulation path of a CO<NUM> refrigerant at the time of defrosting. At the time of defrosting, the electromagnetic opening/closing valves 34A and 34B are closed and the electromagnetic opening/closing valve 21A is opened. This forms a closed CO<NUM> circulation path including the fin-tube heat exchanger <NUM> and the thermosiphon defrost circuit <NUM>.

The CO<NUM> refrigerant liquid in the closed circuit drops by gravity in the thermosiphon defrost circuit <NUM> to the first header 21C and the three second lines 21D, 21E, 21F extending from the first header 21C, is heated and vaporized by the first electric heater <NUM>. The vaporized CO<NUM> refrigerant rises in the check valve 21J of the thermosiphon defrost circuit <NUM> by the principle of thermosiphon, and the risen CO<NUM> refrigerant gas heats and melts the frost attached to the outer surface of the fin-tube heat exchanger <NUM> provided inside the cooler <NUM>. The CO<NUM> refrigerant that is liquefied by heating the fin-tube heat exchanger <NUM> descends in the thermosiphon defrost circuit <NUM> by gravity. The CO<NUM> refrigerant liquid that has descended to the first header 21C and the three second lines 21D, 21E, 21F extending from the first header 21C is again heated and vaporized by the first electric heater <NUM>.

The melt water obtained as the frost is heated and melted falls toward the drain pan <NUM>. At this time, for example, with the configuration in which the second electric heater <NUM> is not provided, there is a possibility that icicles are formed as refreezing occurs below the fin-tube heat exchanger <NUM>. On the other hand, with the defrost system <NUM> according to the present embodiment, since the second electric heater <NUM> and the third electric heater <NUM> are provided at the lowermost part inside the casing <NUM>, it is possible to prevent icicles from being formed below the casing <NUM>. Further, at the time of defrosting, as shown in <FIG>, an opening of the fan <NUM> is closed by the sock duct to assist the temperature rise in the cooler <NUM> and prevent the generation of fog in the cold storage room <NUM>. Note that the configuration in which the second electric heater <NUM> is not provided is also included in the present invention.

As described above, in the defrost system <NUM> of the refrigeration apparatus <NUM> according to the present embodiment, the cooler <NUM> including the casing <NUM>, the fin-tube heat exchanger <NUM> provided inside the casing <NUM>, and the drain pan <NUM> provided below the fin-tube heat exchanger <NUM> is provided inside the cold storage room <NUM>. It is the defrost system <NUM> of the refrigeration apparatus <NUM> including the circulation line (secondary refrigerant circuit) <NUM> connected to the fin-tube heat exchanger <NUM> of the cooler <NUM> and in which a low-temperature CO<NUM> refrigerant circulates at the time of cooling, and the refrigeration cycle <NUM> that cools and reliquefies the CO<NUM> refrigerant in a gaseous form with a refrigerant circulating inside.

The defrost system <NUM> includes the thermosiphon defrost circuit <NUM> that is provided by being branched from the circulation line <NUM>, in which, at the time of defrosting, the CO<NUM> refrigerant staying inside the fin-tube heat exchanger <NUM> repeats a two-phase change of a gaseous form and reliquefaction, and which forms a CO<NUM> circulation path together with the fin-tube heat exchanger <NUM>; the opening/closing valves 34A and 34B that are closed at the time of defrosting and sets the CO<NUM> circulation path to a closed circuit; and the first electric heater <NUM> arranged above the thermosiphon defrost circuit <NUM> so as to be adjacent to the thermosiphon defrost circuit <NUM>.

The CO<NUM> refrigerant is naturally circulated in the closed circuit at the time of defrosting. With the defrost system <NUM> configured in this way, the CO<NUM> refrigerant liquid in the closed circuit is heated and vaporized by the first electric heater <NUM>, and rises in the thermosiphon defrost circuit <NUM> by the principle of thermosiphon, the risen CO<NUM> refrigerant gas heats the fin-tube heat exchanger <NUM> provided inside the cooler <NUM>, and heats and melts the frost attached to the outer surface of the fin-tube heat exchanger <NUM>. The CO<NUM> refrigerant that is liquefied by heating the fin-tube heat exchanger <NUM> descends in the thermosiphon defrost circuit <NUM> by gravity. The CO<NUM> refrigerant liquid that has descended to the first electric heater <NUM> is heated and vaporized by the first electric heater <NUM>. Further, since the second electric heater <NUM> is provided at a lower part inside the casing <NUM>, water droplets descending the fin-tube heat exchanger <NUM> can be recovered in the drain pan <NUM> without being refrozen to be icicles in the fin-tube heat exchanger <NUM> at a lower part of the casing <NUM>. 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 13A and the fins 13B at a lower part of the casing <NUM>.

Further, it includes the pressure sensor <NUM> for measuring the pressure of the CO<NUM> circulation path at the time of defrosting, and the control portion <NUM> that controls the first electric heater <NUM> such that the pressure of the CO<NUM> circulation path decreases when the measurement value measured by the pressure sensor <NUM> is higher than a predetermined pressure. With the defrost system <NUM> configured in this way, it is possible to prevent the pressure inside the thermosiphon defrost circuit <NUM> and the fin-tube heat exchanger <NUM> from becoming extremely high at the time of defrosting, and therefore it is possible to preferably prevent damage to the pipes of the thermosiphon defrost circuit <NUM> and the fin-tube heat exchanger <NUM>.

Further, the thermosiphon defrost circuit <NUM> includes the first line 21B branched from the CO<NUM> feed line <NUM> of the circulation line <NUM> of the CO<NUM> refrigerant, the first header 21C to which an end of the first line 21B is connected, the three second lines 21D, 21E, 21F extending from the first header 21C, the second header <NUM> to which the three second lines 21D, 21E, 21F are connected and which is provided at a position higher than the first header 21C, and the third line <NUM> extending from the second header <NUM> and connected to the CO<NUM> return line <NUM> of the circulation line <NUM>.

The three second lines 21D, 21E, 21F include the second line 21D connecting the most distant parts of the first header 21C and the second header <NUM> in a meander shape, the second line 21E connecting the closest parts of the first header 21C and the second header <NUM> in a meander shape, and the second line 21F arranged between the second line 21D and the second line 21E. With this configuration, because the three second lines 21D, 21E, 21F, which are arranged without crossing one another, can be preferably heated by the first electric heater <NUM> via the heat transfer plate <NUM>, the CO<NUM> refrigerant can be naturally circulated.

With the defrost system <NUM> configured in this way, at the time of defrosting, it can be performed only by the first electric heater <NUM> that heats and naturally circulates the CO<NUM> refrigerant remaining in the pipes of the thermosiphon defrost circuit <NUM> and the fin-tube heat exchanger <NUM> and enables heating and draining of the drain pan <NUM> and the second electric heater <NUM> for preventing re-freezing at the fin-tube heat exchanger <NUM> at a lower part of the casing <NUM> (the third electric heater <NUM> 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 <NUM>. Further, since the fin-tube heat exchanger <NUM> is directly heated, the delay in starting the defrosting can be eliminated.

Further, it further includes the branch circuit <NUM> provided by being branched from the circulation line <NUM>, and on the branch circuit <NUM>, the pressure adjusting valve <NUM> for reducing the pressure when the pressure in the circulation line <NUM> is higher than a predetermined pressure is arranged. With the defrost system <NUM> configured in this way, it is possible to prevent the pressure inside the thermosiphon defrost circuit <NUM> and the fin-tube heat exchanger <NUM> from becoming extremely high at the time of defrosting operation, and therefore it is possible to preferably prevent damage to the thermosiphon defrost circuit <NUM> and the fin-tube heat exchanger <NUM>.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the claims.

Further, in the above-described embodiment, the three second lines 21D, 21E, 21F are provided, but two or more may be provided.

Further, in the above-described embodiment, 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.

Claim 1:
A refrigeration apparatus (<NUM>) in which a cooler (<NUM>) having a casing (<NUM>), a fin-tube heat exchanger (<NUM>) provided inside the casing (<NUM>), and a drain pan (<NUM>) provided below the fin-tube heat exchanger (<NUM>) is provided inside a cold storage room (<NUM>), comprising:
a circulation line (<NUM>) that is connected to the fin-tube heat exchanger (<NUM>) of the cooler (<NUM>) and circulates a CO<NUM> refrigerant having a low temperature at a time of cooling; and
a refrigeration cycle that cools and reliquefies the CO<NUM> refrigerant in a gaseous form with a refrigerant that circulates inside,
the refrigeration apparatus (<NUM>) comprising a defrost system (<NUM>) which includes:
a thermosiphon defrost circuit (<NUM>) that is provided by being branched from the circulation line (<NUM>), in which, at a time of defrosting, the CO<NUM> refrigerant staying inside the fin-tube heat exchanger (<NUM>) repeats a two-phase change of a gaseous form and reliquefaction, and which forms a CO<NUM> circulation path together with the fin-tube heat exchanger (<NUM>);
an opening/closing valve (34A, 34B) that is closed at the time of defrosting and sets the CO<NUM> circulation path to a closed circuit; and
a first electric heater (<NUM>) arranged above the thermosiphon defrost circuit (<NUM>) so as to be adjacent to the thermosiphon defrost circuit (<NUM>), and
naturally circulating the CO<NUM> refrigerant in the closed circuit at the time of defrosting,
wherein
the thermosiphon defrost circuit (<NUM>) includes:
a first line (21B) branched from the circulation line (<NUM>) of the CO<NUM> refrigerant; characterized in that the thermosiphon defrost circuit (<NUM>) further includes:
a first header (21C) to which an end of the first line (21B) is connected
a plurality of second lines (21D, 21E, 21F) that extends from the first header (21C),
a second header (<NUM>) to which the plurality of second lines (21D, 21E, 21F) is connected and which is provided at a position higher than the first header (21C); and
a third line (<NUM>) that extends from the second header (<NUM>) and is connected to the circulation line (<NUM>), and
the plurality of second lines ( 21D, 21E, 21F) at least includes a line (21D) connecting most distant parts of the first header (21C) and the second header (<NUM>) in a meander shape, and a line (21E) connecting closest parts of the first header (21C) and the second header (<NUM>) in a meander shape.