JP7208770B2 - Heat exchanger and heat exchanger defrosting method - Google Patents

Description

The present disclosure relates to heat exchangers and methods of defrosting heat exchangers.

Fin-tube heat exchangers are used in heat exchangers such as air coolers provided in freezers and freezers. A finned-tube heat exchanger is prone to frost on the radiation fins, etc., and the frost layer formed between the fins obstructs the air flow, requiring frequent defrost operation. Therefore, the present inventors have proposed a defrosting method of sublimating and removing frost adhering to fins and heat transfer tubes (Patent Document 1). This defrost method does not generate melted water because the frost is sublimated and scattered by the air flow. Therefore, there is an advantage that the operation of removing the melted water from the heat exchanger is not required, and defrosting can be performed while the air cooler continues to operate.

WO2017/175411

The heat transfer surface of the most upstream heat transfer tube in the flow direction has a high heat transfer coefficient, and the mist (liquid and solid) contained in the gas to be cooled collides with the most upstream heat transfer tube and the tip of the fin due to inertial force. , a phenomenon occurs in which frost formation is concentrated and the growth of frost formation is accelerated. Therefore, since the cooling air flow path is blocked earlier by the growth of the frost layer at these parts than at other parts, there is a problem that the heat exchange between the air to be cooled and the cooling medium flowing through the heat transfer tubes is hindered.

In one embodiment, the frost adhered to the upstream heat transfer tubes and the upstream tip portions of the fins is prevented from growing and clogging the cooling gas flow path, and an efficient defrost operation is performed. An object of the present invention is to suppress deterioration in thermal efficiency of a heat exchanger in operation due to heat applied to heat transfer tubes and fins.

(1) A heat exchanger according to one embodiment,
a gas flow path through which the gas to be cooled flows;
a plurality of heat transfer tubes provided in the gas flow path;
Frost layer on at least one of the plurality of heat transfer tubes, one or more upstream heat transfer tubes positioned in an upstream region in the flow direction of the gas to be cooled, or a heat radiating member provided on the outer periphery of the upstream heat transfer tubes an upstream heating unit for maintaining the adhesion surface temperature below 0°C and higher than the gas to be cooled;
Prepare.

According to the above configuration (1), the surface temperature of the upstream heat transfer tube or the heat dissipating member provided on the outer periphery of the upstream heat transfer tube (hereinafter also referred to as "upstream heat dissipating member") is increased by the upstream heating unit. By adjusting the temperature within the above range (upstream heating), frost adhering to the upstream heat transfer tubes or the upstream heat radiating member can be sublimated and scattered. This suppresses the growth of a frost layer on the heat transfer surface formed by the upstream heat transfer pipe and the upstream heat radiation member (hereinafter also referred to as "upstream heat transfer surface"), and the frost layer prevents gas around the heat transfer surface. Blockage of the flow path can be suppressed. By performing upstream heating all the time or at a considerable frequency, the temperature of the upstream heat transfer surface on which the frost layer adheres is slightly higher than the temperature of the gas to be cooled. It is possible to suppress clogging of the gas flow path around the hot surface and to save energy.
Even if there is a portion of the upstream heat transfer tube and the upstream heat radiation member that is not maintained within the above temperature range, it is assumed that the temperature of that portion is maintained so as not to exceed 0°C. This is because, if there is a portion where the temperature is 0° C. or higher, melt water is generated at that portion.

(2) In one embodiment, in the configuration of (1),
The plurality of heat transfer tubes extend in the gas flow channel along a first direction orthogonal to the flow direction in the gas flow channel, and extend in a second direction orthogonal to the flow direction and the first direction. A plurality of heat transfer tube rows formed by the plurality of heat transfer tubes arranged along the direction are arranged so as to be aligned in the flow direction,
The upstream heat transfer tubes include at least one or more heat transfer tubes belonging to the most upstream heat transfer tube row in the flow direction.
Here, the term “most upstream heat transfer tube row” means including one or more heat transfer tube rows provided on the most upstream side.
According to the above configuration (2), the most upstream heat transfer tube row in the flow direction of the gas to be cooled (hereinafter also simply referred to as "flow direction") can be heated to the above temperature range intensively. As a result, it is possible to suppress the growth of a frost layer on the most upstream heat transfer tube row, where frost tends to grow rapidly, and to suppress the clogging of the gas flow path around the upstream heat transfer surface.

(3) In one embodiment, in the configuration of (2),
A defrost unit for defrosting a defrost target tube among the plurality of heat transfer tubes,
the gas flow channel includes a plurality of flow channel regions aligned in the second direction;
The plurality of heat transfer tubes respectively correspond to the plurality of flow path regions and belong to two or more heat transfer tube arrays adjacent to each other in the flow direction in the same flow direction region. comprising a plurality of heat transfer tube groups formed by
The defrosting unit is configured to selectively defrost the heat transfer tubes of one or more heat transfer tube groups among the plurality of heat transfer tube groups as defrosting target tubes.

According to the above configuration (3), by appropriately selecting the order of defrosting according to the difference in frost growth in each heat transfer tube group, the gas flow path in each heat transfer tube group is prevented from being clogged, and the efficiency is reduced. It is possible to effectively defrost, and it is possible to suppress reattachment of frost that has separated from the upstream frost adhered surface to the heat transfer surface downstream in the flow direction. By using the defrost operation and the upstream heating together, it is possible to effectively prevent clogging of the gas flow path around the heat transfer surface.

(4) In one embodiment, in the configuration of (3),
The defrosting unit is configured to selectively defrost only the most upstream heat transfer tube row in the flow direction as the defrost target tube among the plurality of heat transfer tube rows.
According to the above configuration (4), by selectively defrosting only the heat transfer tube row on the most upstream side in the flow direction as the defrosting target tube, the most upstream heat transfer tube row where frost tends to grow rapidly is preferentially defrosted. As a result, clogging of gas flow paths in the most upstream heat transfer tube array can be suppressed.

(5) In one embodiment, in any one of the configurations (1) to (4),
The upstream heat transfer tube is configured to be able to supply only the defrosting fluid.
According to the above configuration (5), only the defrosting fluid is supplied to the upstream heat transfer tube, and normal cooling operation is not performed. By supplying a defrost fluid having a temperature at which sublimation defrost is possible to the upstream heat transfer tubes, it is possible to perform upstream heating capable of suppressing rapid growth of frost. In addition, since the upstream heat transfer pipe does not perform cooling operation, it is possible to perform upstream heating at all times, thereby suppressing the growth of the frost layer at all times.

(6) In one embodiment, in any one of the configurations (1) to (5),
The upstream heating section is configured to heat the upstream heat transfer tube or the heat radiating member.
According to the above configuration (6), the upstream heat transfer tube or the upstream heat radiation member is heated by the upstream heating unit to a temperature at which frost formation can be sublimated, thereby sublimating the frost adhering to the upstream heat transfer surface. Let the splatter be removed. This embodiment allows for upstream heating by means other than the supply of defrost fluid.

(7) In one embodiment, in any one of the configurations (1) to (6),
The upstream heating section includes a defrost fluid supply section capable of supplying a defrost fluid capable of maintaining the temperature of the frosted surface of the upstream heat transfer tube at less than 0° C. and higher than the temperature of the gas to be cooled.
According to the above configuration (7), the upstream heat transfer surface can be heated by the defrost fluid supplied from the defrost fluid supply section to the upstream heat transfer tube. Note that the upstream heating by the defrost fluid and the upstream heating by the upstream heating section can be used together.

(8) In one embodiment, in any one of the configurations (1) to (7),
The upstream heating unit is configured to maintain a temperature difference between the temperature of the frost layer adhering surface of at least one of the upstream heat transfer pipe or the upstream heat radiation member and the gas to be cooled to be more than 0°C and 10°C or less. be.
According to the above configuration (8), the temperature difference between the upstream frost layer adhesion surface temperature and the gas to be cooled is maintained at more than 0 ° C. and 10 ° C. or less (low temperature heating), so the amount of heat required for upstream heating is reduced. can.

(9) In one embodiment, in any one of the configurations (1) to (8),
The heat dissipating member is a plate-like heat dissipating member provided along the flow direction in the gas flow path so that the plurality of heat transfer tubes penetrate through or come into contact with each other.
According to the above configuration (9), the provision of the plate-shaped heat radiating member increases the heat transfer area and improves the heat transfer performance of the heat exchanger. Further, since the plate-shaped heat radiating member is provided along the flow direction of the gas to be cooled, disturbance of the gas to be cooled can be suppressed. A temperature boundary layer is formed on the surface of the plate-shaped heat radiating member where the turbulence of the gas to be cooled is suppressed. Since the heat transfer coefficient of the heat transfer surface decreases due to the formation of this temperature boundary layer, it is possible to suppress the growth of a frost layer formed on the surface of the plate-shaped heat radiating member. Conversely, if a structure (for example, louver fins) that disturbs the temperature boundary layer is used, the heat transfer rate increases and frost growth is promoted. Using this, it is possible to optimally design the areas where frost should grow and the areas where frost should not grow, that is, the amount of frost growth at each location in relation to the amount of heat exchange and the defrost interval.

(10) In one embodiment, in any one of the configurations (1) to (9),
The heat radiating member has a heat insulating region between the flow direction tip portion and the downstream portion of the heat radiating member for suppressing heat transfer between the flow direction tip portion and the downstream portion.
According to the configuration (10), since the heat insulating region is provided, the heat applied to the tip portion by the upstream heating portion is transmitted to the downstream portion of the heat radiating member, and the cooling of the cooling operation performed at the downstream portion is performed. A decrease in efficiency can be suppressed.

(11) In one embodiment, in the configuration of (3) or (4),
The heat dissipation member is
Arranged so as to straddle an upstream heat transfer tube group arranged on the upstream side in the flow direction among the plurality of heat transfer tube groups and a downstream heat transfer tube group arranged on the downstream side in the flow direction from the upstream heat transfer tube group Along with being
A heat insulating region for suppressing heat transfer between the upstream heat transfer tube group and the downstream heat transfer tube group is provided in a portion of the heat dissipation member between the upstream heat transfer tube group and the downstream heat transfer tube group. .

According to the above configuration (11), the plate-shaped heat-radiating member is arranged so as to straddle the upstream heat-transfer tube group and the downstream heat-transfer tube group, so that the temperature boundary layer is continuously formed except for the tip portion in the flow direction. can be extended. As a result, it is possible to suppress the growth of frost formation in the entire region other than the leading end portion in the flow direction. Further, since the heat insulating region is provided between the upstream heat transfer tube group and the downstream heat transfer tube group, when performing upstream heating, or when performing defrosting in either the upstream heat transfer tube group or the downstream heat transfer tube group Also, it is possible to prevent the heat applied to the heat transfer tubes and the heat dissipating member by the upstream heating or defrosting operation from being transmitted to the other heat transfer tube group during the cooling operation, thereby reducing the cooling efficiency.

(12) A method of defrosting a heat exchanger according to one embodiment includes:
a gas channel through which a gas to be cooled flows; a plurality of heat transfer tubes provided in the gas channel; an upstream heating unit for maintaining a frost layer adhered surface temperature of at least one of the side heat transfer tubes and the heat dissipating members provided on the outer periphery of the upstream heat transfer tubes at less than 0° C. and higher than the temperature of the gas to be cooled; A method of defrosting a heat exchanger comprising:
During operation of the heat exchanger, the upstream heating unit maintains the frost layer adhesion surface temperature of at least one of the upstream heat transfer tube and the heat radiating member at a temperature lower than 0° C. and higher than the gas to be cooled at all times. An upstream heating step is provided.
Here, "always" means that the upstream heating step is performed for 50 to 100% of the cooling operation time.

According to the method (12), the upstream heating step is always performed, and the temperature of the upstream heat transfer surface is adjusted to a temperature at which sublimation defrost is possible (upstream heating), so that the upstream heat transfer surface Adhered frost can be sublimated and scattered. As a result, it is possible to suppress the growth of the frost layer on the upstream heat transfer surface and suppress the clogging of the gas flow path around the heat transfer surface by the frost layer.

(13) In one embodiment, in the method of (12),
The plurality of heat transfer tubes extend in the gas flow path along a first direction orthogonal to a flow direction of the gas to be cooled in the gas flow path, and extend in the flow direction and the first direction. A plurality of heat transfer tube rows formed by the plurality of heat transfer tubes arranged along the orthogonal second direction are arranged so as to be aligned in the flow direction,
The heat exchanger includes a defrost unit for defrosting a defrost target tube among the plurality of heat transfer tubes,
the gas flow channel includes a plurality of flow channel regions aligned in the second direction;
The plurality of heat transfer tubes respectively correspond to the plurality of flow path regions and belong to two or more heat transfer tube arrays adjacent to each other in the flow direction in the same flow direction region. comprising a plurality of heat transfer tube groups formed by
The defrosting unit is configured to selectively defrost the heat transfer tubes of one or more of the heat transfer tube groups among the plurality of heat transfer tube groups as the defrosting target tubes,
A defrosting step of defrosting one or more heat transfer tube groups among the plurality of heat transfer tube groups is provided.

According to the above method (13), by appropriately selecting the order of defrosting according to the difference in the growth of frost on each heat transfer tube group, the gas flow path on each heat transfer surface is prevented from being clogged, and the efficiency is reduced. It is possible to effectively defrost, and it is possible to suppress reattachment of frost that has separated from the adhering surface to the heat transfer surface on the downstream side in the flow direction. By using the defrost operation and the upstream heating together, it is possible to effectively prevent clogging of the gas flow path around the heat transfer surface.

(14) In one embodiment, in the method of (13),
The defrost unit is configured to selectively defrost only the heat transfer tube row on the most upstream side in the flow direction among the plurality of heat transfer tube rows as the defrost target tube,
The defrosting step includes selectively defrosting only the heat transfer tube row on the most upstream side in the flow direction as the defrosting target tube.
According to the above method (13), in the defrosting step, only the most upstream heat transfer tube row can be selectively heated, so that the upstream heat transfer surface can be defrosted intensively. As a result, it is possible to suppress the growth of a frost layer on the most upstream heat transfer tube row, where frost tends to grow rapidly, and to suppress the clogging of the gas flow path around the upstream heat transfer surface.

In one embodiment, in the method (13) or (14),
In the defrosting step,
One defrost time required to defrost all the heat transfer tube groups once is set to be within a limit time for the frost amount adhering to at least a part of the heat transfer tubes to reach an allowable upper limit, and the heat transfer tube group is started from the one defrost time. Allocate a defrost execution time interval for each of
According to the above method, by setting the limit time to an upper limit value that does not block the flow of the gas to be cooled on at least part of the heat transfer surfaces, the blockage of the gas to be cooled does not occur in each heat transfer tube group, and Defrost can be performed efficiently.

(15) In one embodiment, in the method of (13) or (14),
In the defrosting step,
When the heat transfer tube group arranged on the upstream side in the flow direction is to be defrosted, the flow direction is reversed.
According to the above method (15), when the heat transfer tube group arranged on the upstream side in the flow direction is defrosted, the flow direction of the gas to be cooled is reversed so that the frost separated from the adhering surface is removed on the downstream side. To suppress redeposition to a heat transfer tube and to enable treatment on the upstream side. Also, the frost adhering to the tip portion can be removed efficiently. Furthermore, since the gas to be cooled whose temperature is raised by the heat applied during defrosting returns to the upstream side once, is mixed, and flows into another heat transfer tube group, it is possible to suppress temperature unevenness downstream of the heat exchanger.

According to some embodiments, it is possible to prevent the gas flow path from being clogged by frost adhering to the upstream heat transfer surface, and to enable efficient defrost operation. The effect of added heat on the thermal efficiency of the heat exchanger can be reduced.

1 is a perspective view of a heat exchanger according to one embodiment; FIG. 1 is a plan view of a heat exchanger according to one embodiment; FIG. 1 is a system diagram of a refrigerator according to one embodiment for sending a cooling medium to a heat exchanger; FIG. 4 is a block diagram of an upstream heating section according to one embodiment; FIG. 4 is a block diagram of an upstream heating section according to one embodiment; FIG. It is a top view of the upstream heat radiating member which concerns on one Embodiment. It is a top view of the upstream heat radiating member which concerns on one Embodiment. FIG. 4 is a plan view of an upstream heat transfer surface according to one embodiment; FIG. 4 is a plan view of an upstream heat transfer surface according to one embodiment; 1 is a schematic plan view of a heat exchanger according to one embodiment; FIG. 1 is a schematic plan view of a heat exchanger according to one embodiment; FIG. FIG. 4 is a process diagram of a defrosting method for a heat exchanger according to one embodiment;

Several embodiments of the present invention will now be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as the embodiment or shown in the drawings are not meant to limit the scope of the present invention, but merely illustrative examples.
For example, expressions denoting relative or absolute arrangements such as "in a direction", "along a direction", "parallel", "perpendicular", "center", "concentric" or "coaxial" are strictly not only represents such an arrangement, but also represents a state of relative displacement with a tolerance or an angle or distance to the extent that the same function can be obtained.
For example, expressions such as "identical", "equal", and "homogeneous", which express that things are in the same state, not only express the state of being strictly equal, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, expressions that express shapes such as squares and cylinders do not only represent shapes such as squares and cylinders in a geometrically strict sense, but also include irregularities and chamfers to the extent that the same effect can be obtained. The shape including the part etc. shall also be represented.
On the other hand, the expressions "comprising", "comprising", "having", "including", or "having" one component are not exclusive expressions excluding the presence of other components.

FIG. 1 is a perspective view of a heat exchanger 10 (10A) according to one embodiment, and FIG. 2 is a plan view showing part of a heat exchanger 10 (10B) according to another embodiment. The casing 12 of the heat exchanger 10 (10A, 10B) is open at the front surface to which the air to be cooled a flows and the rear surface to which the air to be cooled a flows out. A path is formed. A plurality of heat transfer tubes 16 are provided inside the casing 12 so as to face the cooling air flow path. In FIG. 1, the fans 14 (14a, 14b, 14c) are arranged on the downstream side of the casing 12 in the flow direction, but they may be arranged on the upstream side of the casing 12 in the flow direction and operated as forced-type fans. . In the heat exchanger 10 ( 10 B) with respect to the casing 12 , a heat radiating member 40 is provided on the outer circumference of the heat transfer tube 16 . Although the heat radiating member 40 is not illustrated in the heat exchanger 10 (10A) shown in FIG. 1, the heat radiating member 40 may or may not be provided.

As shown in FIGS. 3 to 5, the heat exchanger 10 includes upstream heating units 50 (50a, 50b, 50c). Frost layer adhering surface temperature of one or more upstream heat transfer tubes 16 (16a) located in the upstream region in the flow direction, or upstream heat dissipation member 40 (40a) provided on the outer circumference of the upstream heat transfer tube 16 (16a) At least one of the frost layer adhering surface temperatures can be maintained at less than 0° C. and higher than the temperature of the air to be cooled a.
If there is a portion of the upstream heat transfer pipe 16 (16a) and the upstream heat radiation member 40 (40a) that is not maintained within the above temperature range, the temperature of that portion is maintained so as not to exceed 0°C. This is because, if there is a portion where the temperature is 0° C. or higher, water from melting frost is generated at that portion.

During the cooling operation of the heat exchanger 10, the surface temperature of the upstream heat transfer tube 16 (16a) or the upstream heat radiation member 40 (40a) is always adjusted to the above temperature range where sublimation defrost is possible by the upstream heating unit 50. . As a result, the frost adhering to the upstream heat transfer surface formed by the upstream heat transfer pipe 16 (16a) and the upstream heat radiation member 40 (40a) can be sublimated and scattered. It is possible to suppress the growth of the layer and suppress the blockage of the air flow path around the heat transfer surface due to the frost layer. In addition, this upstream heating is always performed, so that the temperature of the frost layer adhering surface is slightly higher than the temperature of the air to be cooled a (low temperature heating), and the growth of the frost layer on the upstream heat transfer surface is suppressed. , blockage of the gas flow path around the heat transfer surface by the frost layer can be suppressed.

In one embodiment, the plurality of heat transfer tubes 16 constituting the heat exchanger 10 (10A) shown in FIG. ) and perpendicular to the flow direction of the air to be cooled a and the first direction (the direction of arrow c; hereinafter also referred to as the “second direction”). A plurality of heat transfer tube rows formed by a plurality of heat transfer tubes 16 arranged in a row are arranged so as to line up in the flow direction. The upstream heat transfer tubes 16 (16a) include at least one or more heat transfer tubes belonging to the most upstream heat transfer tube row in the flow direction.

During the cooling operation of the heat exchanger 10, the upstream heating unit 50 selectively adjusts at least one or more heat transfer tubes belonging to the most upstream heat transfer tube row in the flow direction to the above temperature range. The frost adhering to the heat transfer surfaces formed on the side heat transfer tube rows can be predominantly sublimated and scattered. As a result, it is possible to suppress the growth of a frost layer on the most upstream heat transfer tube row, where frost tends to grow rapidly, and to suppress the blockage of the cooling air flow path around the heat transfer surface.

In one embodiment, as shown in FIG. 3 , the heat exchanger 10 includes a defrost unit 18 for defrosting a defrost target tube among the plurality of heat transfer tubes 16 . As shown in FIG. 1, the cooling air flow path includes a plurality of flow path areas Fa, Fb, and Fc arranged in the second direction, and the plurality of heat transfer tubes 16 correspond to the plurality of flow path areas Fa to Fc, respectively. and a plurality of heat transfer tube groups Ta, Tb, Tc, . . In FIG. 1, although a plurality of heat transfer tube groups are not shown in the flow path areas Fb and Fc, the flow path areas Fb and Fc also include a plurality of heat transfer tube groups in the same manner as the flow path area Fa. and The defrost unit 18 is configured to selectively defrost the heat transfer tubes 16 of one or more heat transfer tube groups among the plurality of heat transfer tube groups as defrost target tubes.

In one embodiment, as shown in FIG. 1, the fans 14 (14a, 14b, 14c) are provided in each flow path area Fa, Fb, and Fc, and select the flow of the air to be cooled a for each flow path area. can be formed Further, as shown in FIG. 1, a plurality of heat transfer tube groups Ta, Tb, and Tc are arranged in order from the upstream side in the flow direction, and the upstream heat transfer tube 16 (16a) constitutes the heat transfer tube group Ta provided on the upstream side. It is a part of the heat transfer tubes arranged on the upstream side of the group of heat transfer tubes.

In the above configuration, one or more heat transfer tube groups are selected from the plurality of heat transfer tube groups as defrost target tubes, and defrosting is performed from the selected heat transfer tube group. By appropriately selecting the order of defrosting, while preventing the blockage of the cooling air flow path around the heat transfer surface formed on the surface of the heat transfer tube 16 and the heat dissipating member 40, the frost peeled off from the adhered surface during defrosting is removed from the downstream side. Redeposition on the heat transfer surface can be suppressed. For example, in the heat transfer tube group to which the same flow path area belongs among the plurality of flow path areas Fa, Fb, and Fc, defrosting is performed simultaneously on the upstream side and the downstream side, so that the frost layer peeled off from the upstream adhesion surface is removed from the downstream side. Redeposition on the side heat transfer surface can be suppressed. Alternatively, the defrost operation can be made more efficient by reducing the defrost frequency in the downstream heat transfer tube groups in the flow direction where the frost layer grows slowly. Alternatively, as will be described later, the closing time of the air flow path on the heat transfer surface is obtained for each heat transfer tube group, and the defrosting operation is performed at least once per closing time of each heat transfer tube group.

In one embodiment, as shown in FIG. 3, the refrigerator 20 supplies refrigerant to the heat transfer tubes 16 to cool the air a to be cooled during the cooling operation. The defrosting unit 18 supplies a defrosting fluid to a heat transfer tube group to be defrosted during defrosting. The refrigerant circulating in the refrigerant circuit 22 is sucked into the compressor 24 in gaseous state, pressurized by the compressor 24, cooled by the condenser 26, and liquefied. The refrigerant liquid liquefied by the condenser 26 is temporarily stored in the receiver 28 and then decompressed through the expansion valve 30 . The refrigerant decompressed by the expansion valve 30 is a non-return tube 16 (16a) of the heat exchanger 10 and the heat transfer tube groups Ta, Tb, and Tc except for the heat transfer tube group Ta that is defrosted. It is supplied to the heat transfer tubes 16 of the heat transfer tube groups Tb and Tc through the valve 32, and cools the air to be cooled a to a predetermined cooling temperature. The refrigerant that has been used to cool the air a to be cooled is returned to the refrigerant circuit 22 .

High-pressure refrigerant (gas phase) in the receiver 28 is stored in the buffer tank 45 as the defrost fluid and supplied to the heat transfer tube group to be defrosted through the defrost flow path 34 . This high-pressure refrigerant is stored in the buffer tank 45 after being adjusted in terms of temperature, pressure, and the like. The control unit 48 controls the opening degree of the pressure regulating valve 36 so that the detection value of the pressure sensor 47 becomes a predetermined value, controls the operation of the heating unit 46, and reduces the defrost refrigerant gas flowing through the defrost flow path 34. When sent to a heat transfer tube group to be defrosted, the temperature of the surface on which frost adheres is adjusted to be lower than 0°C and higher than the temperature of air to be cooled a can be maintained, and sublimation defrost is possible. The adjusted defrost refrigerant gas is sent to the heat transfer tube group to be defrosted. The refrigerant gas subjected to defrosting is condensed and liquefied inside the heat transfer tube, then expanded and decompressed through the capillary tube 38, and joins the low-pressure refrigerant line 22a. After that, it is evaporatively gasified through another heat transfer tube group and returned to the refrigerant circuit 22 . As a decompression mechanism instead of the capillary tube 38, a decompression valve such as an electromagnetic valve or an expansion valve may be used.

In one embodiment, as shown in FIG. 3 , the upstream heating unit 50 (50a) reduces the temperature of the heat transfer surface on which frost adheres to the upstream heat transfer tube 16 (16a) during defrosting to less than 0° C. A defrost fluid supply section 44 capable of supplying a defrost fluid that can be maintained at a temperature higher than the temperature of the cooling air a is included. The defrosting fluid supply section 44 includes a buffer tank 45 and a heating section 46 . The defrosting fluid supply unit 44 supplies a defrosting fluid capable of maintaining the temperature of the frosted surface at -2°C to -5°C, for example. The defrost fluid supply unit 44 supplies defrost fluid capable of maintaining the temperature of the frosted surface below 0° C. and higher than the temperature of the air to be cooled a to the heat transfer tube group to be defrosted. As a result, sublimation defrost, which sublimates and removes the frost adhering to the frost layer adhering surface, becomes possible.
Further, by supplying the defrost fluid adjusted to a state in which sublimation of frost formation is possible to the upstream heat transfer pipe 16 (16a), upstream heating becomes possible. Frost formation that cannot be dealt with by upstream heating due to the structure can be dealt with by defrosting operation.

In the refrigerator 20 shown in FIG. 3 , the defrost fluid is a high-pressure refrigerant stored in the receiver 28 and supplied via the defrost channel 34 . By using this refrigerant as the defrost fluid, the defrost heat source does not need to be obtained from another heat source.

In one embodiment, as shown in FIG. 3, the defrost unit 18 uses only the upstream heat transfer tube 16 (16a), which is the most upstream heat transfer tube row in the flow direction, as the defrost target tube among the plurality of heat transfer tube rows. configured to selectively defrost;
According to this embodiment, by selectively defrosting only the upstream heat transfer pipe 16 (16a) as the defrost target pipe, it is possible to preferentially defrost the upstream heat transfer pipe 16 (16a) in which the frost layer tends to grow rapidly. . As a result, it is possible to suppress the growth of frost formation on the upstream heat transfer tubes 16 (16a) where the growth of frost formation is remarkable. In this case, the upstream heating unit 50 (50a) maintains the defrosting fluid in a state in which sublimation of frost formation is possible, so that the defrosting operation can also serve as the upstream heating.

In one embodiment, as shown in FIG. 3, a defrost flow path 35 is provided for supplying the defrost fluid from the buffer tank 45 only to the upstream heat transfer tube 16 (16a), which is the most upstream heat transfer tube row. The heat transfer tube row of the upstream heat transfer tubes 16 (16a) is only subjected to defrost operation, and normal cooling operation is not performed in this embodiment. By supplying a defrost fluid having a temperature, pressure, etc. that enables sublimation defrost at all times to the heat transfer tube row of the upstream heat transfer tubes 16 (16a), upstream heating becomes possible.
In one embodiment, during defrosting, the temperature of the frost layer adhered surface of the upstream heat transfer tube 16 (16a), which is the most upstream heat transfer tube row, is configured to be lower than the temperature of the frost layer adhered surface of the downstream heat transfer tube group. be done. For example, the pressure regulating valve 37 provided in the defrost passage 35 controls the temperature, pressure, etc. of the defrost fluid, thereby adjusting the temperature of the frost layer adhering surface. As a result, it is possible to efficiently suppress the growth of the frost layer.

The defrost fluid that has been defrosted in the upstream heat transfer tube 16 (16a) is expanded and decompressed through the capillary tube 38 and joins the low-pressure refrigerant line 22a. Unlike other heat transfer tube groups, the upstream heat transfer tube 16 (16a) is not provided with a branch line 23 into which the refrigerant flows from the refrigerant circuit 22 .

4 and 5 show another embodiment of the upstream heating section 50. FIG. The upstream heating units 50 (50b, 50c) are configured to heat the upstream heat transfer tubes 16 (16a) or the upstream heat radiation members 40 (40a). The upstream heat transfer surface formed by the upstream heat transfer pipe 16 (16a) or the upstream heat radiation member 40 (40a) is heated by the upstream heating unit 50 (50b, 50c) to a temperature at which sublimation defrost is possible. , the frost layer F adhering to the upstream heat transfer surface can be sublimated and removed.
In this embodiment, upstream heating is enabled by means other than the defrost operation.

The upstream heating section 50 ( 50 b ) shown in FIG. 4 includes a high-frequency current induction section 52 . The high-frequency current induction part 52 is connected to the upstream heat transfer tube 16 (16a) via a lead wire 54 . The cooling medium r cooled by the refrigerator 20 flows inside the heat transfer tube 16 (16a). By passing the high-frequency current E from the high-frequency current induction part 52 to the upstream heat transfer tube 16 (16a), the surface temperature of the upstream heat transfer tube 16 (16a) can be set to a temperature at which sublimation defrost can be performed. In this case, the high-frequency current E can be concentrated on the surface of the upstream heat transfer tube 16 (16a) to which the frost layer F adheres due to the skin effect. Concentrating on the surface of the upstream heat transfer tube 16 (16a) enables energy saving.
The object to be heated is the upstream heat radiation member 40 (40a) instead of the upstream heat transfer pipe 16 (16a), and the frost layer F adhering to the upstream heat radiation member 40 (40a) is removed by sublimation defrost. good too.

In one embodiment, as shown in FIG. 5, a conductive material layer 58 is formed on the surface of the upstream heat radiating member 40 (40a) to be heated by applying a current from the conducting portion 56. An electrically insulating layer 60 is formed inside 58 . The upstream heating section 50 ( 50 b ) includes a conducting section 56 for applying current to the conductive material layer 58 via the conducting wire 54 . During the defrost operation, a current is passed from the conducting part 56 to the conductive material layer 58 to heat the conductive material layer 58, and the frost layer F adhering to the surface of the conductive material layer 58 is heated to a temperature of less than 0°C. and remove the frost layer F by sublimation. According to this embodiment, since the electrically insulating layer 60 is provided inside the conductive material layer 58 , current can flow intensively in the conductive material layer 58 . Also, by making the film thickness of the conductive material layer 58 as thin as possible, the electric power required for heating can be saved.
In this embodiment, the object to be heated is the upstream heat radiation member 40 (40a), but it may be the upstream heat transfer pipe 16 (16a) instead.

In one embodiment, the upstream heating unit 50 reduces the temperature difference between the frost layer adhering surface temperature of at least one of the upstream heat transfer pipe 16 (16a) or the upstream heat radiation member 40 (40a) and the air to be cooled a to 0°C. above and maintained at 10° C. or less. This low-temperature heating can reduce the amount of heat required as a defrosting heat source during defrosting by sublimation.

In one embodiment, as shown in FIG. 2, a plate-shaped heat radiating member 40 is provided along the flow direction (arrow a direction) in the cooling air flow path so that the plurality of heat transfer tubes 16 pass through or come into contact with each other. . By providing the plate-shaped heat radiating member 40, the heat transfer area is increased, so that the heat transfer performance of the heat exchanger 10 can be improved. Further, since the plate-shaped heat radiating member 40 is provided along the flow direction of the air to be cooled a, disturbance of the air to be cooled a can be suppressed. As shown in FIG. 6A, on the surface of the plate-shaped heat radiating member 40 in which the turbulence of the air to be cooled a is suppressed, there is a temperature boundary layer Bt in which the temperature gradually decreases toward the surface of the plate-shaped heat radiating member 40. It is formed. Due to the formation of this temperature boundary layer, the heat transfer coefficient of the heat transfer surface is reduced, and the growth of a frost layer formed on the surface of the plate-shaped heat radiating member can be suppressed. FIG. 6A schematically shows the temperature distribution of the thermal boundary layer Bt.

In one embodiment, as shown in FIG. 2, a plurality of plate-shaped heat dissipation members 40 are arranged in parallel with a space therebetween along the flow direction. In this way, since the plate-shaped heat radiating member 40 is arranged along the flow direction of the air to be cooled a, turbulence of the air to be cooled a can be suppressed. can improve heat transfer performance. Further, since disturbance of the air to be cooled a can be suppressed, a temperature boundary layer Bt is formed on the surface of the plate-shaped heat radiating member 40 . This can suppress the growth of the frost layer.
The plate-shaped heat dissipation member 40 can suppress turbulence of the air to be cooled a to the maximum by forming the plate-shaped heat dissipation member 40 into a flat plate shape. It may be a heat radiating member.

In one embodiment, the arrangement of the plurality of heat transfer tubes 16 suppresses the growth of a frost layer without forming a turbulent flow of the air to be cooled a, and suppresses the concentration of frost due to the adhesion of mist due to inertia. From the point of view, a grid arrangement is preferable to a staggered arrangement with respect to the flow of the air to be cooled a. Also, from the viewpoint of promoting heat transfer, a staggered arrangement is desirable, and it is preferable to appropriately select them in relation to conditions such as the amount of heat exchanged and the defrost cycle time.

In one embodiment, as shown in FIGS. 6A and 6B, between the flow direction tip portion 40 (40b) of the upstream heat dissipation member 40 (40a) and the downstream portion, the tip portion 40 (40b) and the downstream side It has adiabatic regions 62 (62a, 62b) that suppress heat transfer with the heat transfer tubes 16. As shown in FIG. Since the heat insulating regions 62 (62a, 62b) are provided, when the upstream heating is performed by the upstream heating unit 50 (50b, 50c), the heat applied from the upstream heating unit 50 to the tip portion 40 (40b) is kept during the cooling operation. can be suppressed from being transmitted to the downstream heat transfer tube 16 and lowering the cooling efficiency.
6A and 6B show an embodiment in which a heat radiating member 40 is provided further upstream than the upstream heat transfer tubes 16 (16a).

In the embodiment shown in FIG. 6A, the heat insulating region 62 (62a) is composed of a gap s formed to have a length that allows the temperature boundary layer Bt to be maintained without interruption in the flow direction of the air to be cooled a. Since the air present in the gap s has heat insulating properties, the formation of the gap s enables the formation of a heat insulating region. Further, since the gap s is formed to have a length that allows the temperature boundary layer Bt to be maintained without interruption in the flow direction of the air to be cooled a, frost formation is promoted at the end of the heat radiating member 40 formed by the gap s. will not be
In the embodiment shown in FIG. 6B, the insulating zone 62 (62b) constitutes a thermal insulating zone made of a material with low thermal conductivity. The surface of this adiabatic area is formed smooth so that the air to be cooled a is not disturbed, and does not form a step with the other tip portion 40 (40b).
Note that the heat insulating regions 62 may be provided between each heat transfer tube group.

In one embodiment, as shown in FIGS. 7A and 7B, the heat radiating member 40 includes an upstream heat transfer tube group Ta arranged on the upstream side in the flow direction among the plurality of heat transfer tube groups, and an upstream heat transfer tube group Ta. It is arranged so as to straddle the downstream heat transfer tube group Tb arranged on the downstream side in the direction. A heat insulating region for suppressing heat transfer between the upstream heat transfer tube group Ta and the downstream heat transfer tube group Tb is provided between the upstream heat transfer tube group Ta and the downstream heat transfer tube group Tb of the heat radiating member 40. 62 (62a, 62b).
According to these embodiments, the temperature boundary layer Bt can be continuously extended except for the tip portion 40 (40b) in the flow direction. As a result, the growth of frost formation can be suppressed in the entire region other than the tip portion 40 (40b) in the flow direction. In addition, since the heat insulating region 62 (62a, 62b) is provided between the upstream heat transfer tube group Ta and the downstream heat transfer tube group Tb, when performing upstream heating, or when performing upstream heat transfer tube group Ta or downstream heat transfer tube When defrosting is performed in one group Tb, the heat applied to the heat transfer tubes 16 and the heat dissipation member 40 by upstream heating or defrosting operation is suppressed from being transmitted to the other heat transfer tube group during cooling operation and reducing the cooling efficiency. can.

In one embodiment, as shown in FIG. 1, a plurality of heat transfer tube groups may be arranged in the flow direction of the air to be cooled a. For example, two or more heat transfer tube groups may be arranged in the flow direction of the air to be cooled a. , the upstream heat transfer tube 16 (16a) on the most upstream side may be preferentially defrosted. Also, a plurality of heat transfer tube groups may be stacked vertically.
Moreover, as shown in FIG. 8A, a plurality of heat transfer tube groups Ta, Tb, and Tc may be formed in an arc shape so as to surround the fan 14 with the fan 14 as the center. A plurality of heat transfer tube groups Ta, Tb and Tc are arranged in this order from the upstream side of the air to be cooled a. The embodiment shown in FIG. 8B is an example in which the heat transfer tube group is divided into a plurality of flow path areas Fa, Fb and Fc, and each flow path area is composed of a plurality of heat transfer tube groups Ta, Tb and Tc.

In the defrosting method according to one embodiment, as shown in FIG. 9, while the heat exchanger 10 is in operation, the upstream heating unit 50 first heats the upstream heat transfer pipe 16 (16a) or the upstream heat radiation member 40 (40a). ) is always kept below 0° C. and higher than the temperature of the air to be cooled a (upstream heating step S10). As a result, the frost layer adhering to the upstream heat transfer pipe 16 (16a) or the upstream heat radiation member 40 (40a) can be sublimated and removed. Therefore, by adjusting the temperature condition to the above, the growth of the frost layer can be suppressed, and the cooling air flow path on the heat transfer surface can always be secured.

In the upstream heating step S10, as shown in FIG. 3, the upstream heat transfer tube 16 (16a) is heated by flowing a defrost fluid that can be heated upstream into the heat transfer tube, and FIG. As shown in 6B, there is a case where the upstream side heat radiating member 40 (40a) is heated by energization or the like, and a case where these are used together as shown in FIGS. 4, 7A, and 7B. Electric heating heats the conductive substance layer 58 by passing a current from the conductive portion 56 to the conductive substance layer 58 of the upstream heat radiating member 40 (40a) to remove the frost layer F adhering to the surface of the conductive substance layer 58. The temperature is raised to less than 0° C. to sublimate and remove the frost layer F.

In one embodiment, the plurality of heat transfer tubes 16 extend along a width direction (direction of arrow b in FIG. 1; first direction) perpendicular to the flow direction of the air to be cooled a in the cooling air flow path, and A plurality of heat transfer tube rows formed by a plurality of heat transfer tubes 16 arranged along the vertical direction (direction of arrow c in FIG. 1; second direction) orthogonal to the flow direction and the width direction are arranged in the flow direction. arrayed. In addition, as shown in FIG. 3, the heat exchanger 10 includes a defrost unit 18 for defrosting a defrost-target tube among the plurality of heat transfer tubes 16, and the cooling air flow path includes a plurality of flow paths arranged in the vertical direction. It contains regions Fa, Fb and Fc. The plurality of heat transfer tubes 16 are formed of a plurality of heat transfer tubes that correspond to the plurality of flow path regions Fa to Fc and belong to two or more heat transfer tube rows adjacent to each other in the flow direction within the same flow path region. The defrost unit 18 selectively defrosts the heat transfer tubes 16 of one or more of the heat transfer tube groups Ta, Tb, Tc, etc. as defrost target tubes among the plurality of heat transfer tube groups. configured to do so. In the heat exchanger 10 having such a configuration, one or more heat transfer tube groups among the plurality of heat transfer tube groups are defrosted (defrosting step S12).

According to the defrosting step S12, during defrosting, the order of defrosting is appropriately selected according to the difference in frost growth between the heat transfer tube groups Ta, Tb, Tc, . Efficient defrosting can be performed while preventing clogging of the flow path, and reattachment of frost separated from the adhered surface to the heat transfer surface on the downstream side in the flow direction can be suppressed. By using both the defrost operation and the upstream heating, it is possible to effectively prevent clogging of the gas flow path around the heat transfer surface.

In one embodiment, the defrost unit 18 is configured to selectively defrost only the upstream heat transfer tube 16 (16a), which is the most upstream heat transfer tube row in the flow direction, as a defrost target tube among the plurality of heat transfer tube rows. be done. Then, in the defrosting step S12, defrosting is selectively performed on the upstream heat transfer tube 16 (16a) in the flow direction as a defrosting target tube (step S12a).
According to this embodiment, in the defrosting step S12, by selectively defrosting the upstream heat transfer pipe 16 (16a) as the defrosting target pipe, the upstream heat transfer pipe 16 (16a) can be preferentially defrosted. It is possible to suppress the growth of frost on the heat transfer tubes 16 (16a).

In one embodiment, in the defrost step S12, one defrost required to defrost all the heat transfer tube groups once in accordance with the limit time for the frost amount adhering to at least a part of the heat transfer tube 16 to reach the upper limit of the allowable value. set the time. Then, from this one defrost time, the defrost execution time interval for each heat transfer tube group is set.
According to this embodiment, by setting the limit time to the upper limit value at which the flow of the air to be cooled a does not block the gaps between the plurality of heat radiating members 40, the cooling air between the heat radiating members 40 in each heat transfer tube group Defrost can be performed efficiently without clogging the flow path.

In one embodiment, the defrost execution time interval of each of the plurality of heat transfer tube groups is set to the downstream side in the flow direction of the air to be cooled a, because the growth of frost tends to slow down in the heat transfer tube group on the downstream side in the flow direction of the air to be cooled a. The longer the heat transfer tube group, the longer it is set.
According to this embodiment, by setting the defrost implementation time interval to be longer for the heat transfer tube groups downstream in the flow direction of the air to be cooled a, the frequency of the defrost operation can be reduced. 10 can be suppressed from decreasing in cooling efficiency.

In one embodiment, in the defrosting step S12, a defrosting fluid capable of maintaining a frost-attached surface temperature below 0° C. and higher than the temperature of the gas to be cooled is applied to the heat transfer tubes 16 of the heat transfer tube group to be defrosted. By supplying the defrost fluid, the frost adhering to the heat transfer tubes 16 is sublimated by the inherent heat of the defrost fluid (sublimation defrost step S12b). The defrost fluid is, for example, a high-pressure refrigerant stored in the receiver 28 and supplied via the defrost flow path 34 in the refrigerator 20 shown in FIG.
According to this embodiment, the defrosting fluid capable of maintaining the surface temperature of the frost adhering to less than 0° C. and higher than the temperature of the gas to be cooled is supplied to the heat transfer tubes 16 for defrosting. Sublimation defrost, which sublimates and removes the frost that has formed, becomes possible.

In one embodiment, in the defrosting step S12, in each of the plurality of heat transfer tube groups, the temperature difference between the air to be cooled a and the defrost fluid is set to be smaller as the heat transfer tube group is arranged downstream in the flow direction of the air to be cooled a. be done. The smaller the temperature difference between the air to be cooled a and the defrost fluid, the less the frost removing effect. Therefore, by decreasing the temperature difference toward the downstream side in the flow direction where the growth of frost is slow, it is possible to suppress a decrease in the cooling efficiency of the heat exchanger 10 while maintaining the effect of removing frost.

In one embodiment, in the defrosting step S12, when the heat transfer tube group to be defrosted is arranged on the upstream side in the flow direction of the air to be cooled a, the fan 14 is reversely rotated to reverse the flow direction (reverse flow direction). Step S12c).
According to this embodiment, when the heat transfer tube group arranged on the upstream side in the flow direction is defrosted, by reversing the flow direction of the air to be cooled a, the frost separated from the adhering surface is transferred to the heat transfer tube on the downstream side. It is possible to suppress the re-adhesion to , and to treat it on the upstream side. Also, the frost adhering to the tip portion can be removed efficiently. Furthermore, since the gas to be cooled whose temperature is raised by the heat applied during defrosting returns to the upstream side once, is mixed, and flows into another heat transfer tube group, temperature unevenness on the downstream side of the heat exchanger 10 can be suppressed.

According to some embodiments, frost adhering to the upstream heat transfer pipes and the tip portions of the heat radiating members can be prevented from growing and clogging the cooling gas flow path, and efficient defrost operation can be performed. Also, it is possible to prevent the heat applied to the heat transfer tubes and the fins from the heat applied to the heat transfer tubes and the fins during the defrost operation from lowering the thermal efficiency of the heat exchanger during the cooling operation.

10 (10A, 10B) heat exchanger 12 casing 14 fan 16 heat transfer tube 16a upstream heat transfer tube 18 defrost unit 20 refrigerator 22 refrigerant circuit 22a low pressure refrigerant line 23 refrigerant branch passage 24 compressor 26 condenser 28 receiver 30 expansion valve 32 reverse Stop valves 34, 35 Defrost flow paths 36, 37 Pressure regulating valve 38 Capillary tube 40 Heat dissipation member 40a Upstream heat dissipation member 40b Tip portion 44 Defrost fluid supply unit 45 Buffer tank 46 Heating unit 47 Pressure sensor 48 Control unit 50 (50a, 50b , 50c) upstream heating section 52 high-frequency current induction section 54 conducting wire 56 current-carrying section 58 conductive material layer 60 electric insulation layer 62 (62a, 62b) heat insulation zone Bt temperature boundary layer
F Frost layer Fa, Fb, Fc Flow path area Ta, Tb, Tc Heat transfer tube group a Air to be cooled r Cooling medium s Gap

Claims (14)

a gas flow path through which the gas to be cooled flows;
a plurality of heat transfer tubes provided in the gas flow path;
a heat radiating member provided on the outer circumference of one or more upstream heat transfer tubes positioned in an upstream region in the flow direction of the gas to be cooled among the plurality of heat transfer tubes ;
an upstream heating unit for maintaining a frost layer adhered surface temperature of at least one of the upstream heat transfer pipe and the heat radiating member at less than 0° C. and higher than the temperature of the gas to be cooled;
with
the heat radiating member has, between the flow direction tip portion and the downstream portion of the heat radiating member, a heat insulating region that suppresses heat transfer between the flow direction tip portion and the downstream portion;
While cooling the gas to be cooled by flowing a refrigerant through one or more downstream heat transfer tubes that form a downstream heat transfer surface together with the downstream portion of the heat radiating member, the upstream heating unit configured to adjust the frost layer adhering surface temperature of at least one of the upstream heat transfer tube or the heat radiation member
A heat exchanger characterized by: The plurality of heat transfer tubes extend in the gas flow channel along a first direction orthogonal to the flow direction in the gas flow channel, and extend in a second direction orthogonal to the flow direction and the first direction. A plurality of heat transfer tube rows formed by the plurality of heat transfer tubes arranged along the direction are arranged so as to be aligned in the flow direction,
2. The heat exchanger according to claim 1, wherein the upstream heat transfer tubes include at least one heat transfer tube belonging to the most upstream heat transfer tube row in the flow direction. A defrost unit for defrosting a defrost target tube among the plurality of heat transfer tubes,
the gas flow channel includes a plurality of flow channel regions aligned in the second direction;
The plurality of heat transfer tubes respectively correspond to the plurality of flow path regions and belong to two or more heat transfer tube arrays adjacent to each other in the flow direction in the same flow direction region. comprising a plurality of heat transfer tube groups formed by
3. The defrost unit is configured to selectively defrost the heat transfer tubes of one or more of the heat transfer tube groups among the plurality of heat transfer tube groups as the defrost target tubes. A heat exchanger as described. 3. The defrosting unit is configured to selectively defrost only the heat transfer tube row on the most upstream side in the flow direction as the defrost object tube among the plurality of heat transfer tube rows. The heat exchanger according to . The heat exchanger according to any one of claims 1 to 4, wherein the upstream heat transfer tube is configured to be capable of supplying only defrost fluid. The heat exchanger according to any one of claims 1 to 5, wherein the upstream heating section is configured to heat the upstream heat transfer pipe or the heat radiating member. The upstream heating unit includes a defrost fluid supply unit capable of supplying a defrost fluid capable of maintaining a temperature of a frosted surface of the upstream heat transfer tube at less than 0° C. and higher than the temperature of the gas to be cooled. The heat exchanger according to any one of claims 1 to 6, characterized by: The upstream heating unit is configured to maintain a temperature difference between the frost layer adhering surface temperature of at least one of the upstream heat transfer pipe or the heat radiating member and the gas to be cooled at more than 0° C. and 10° C. or less. The heat exchanger according to any one of claims 1 to 7, characterized in that: 9. The heat radiation member is formed of a plate-like heat radiation member provided along the flow direction in the gas flow path so that the plurality of heat transfer tubes penetrate through or come into contact with each other. The heat exchanger according to any one of . The heat dissipation member is
Arranged so as to straddle an upstream heat transfer tube group arranged on the upstream side in the flow direction among the plurality of heat transfer tube groups and a downstream heat transfer tube group arranged on the downstream side in the flow direction from the upstream heat transfer tube group Along with being
The heat insulating region for suppressing heat transfer between the upstream heat transfer tube group and the downstream heat transfer tube group is provided at a portion of the heat radiating member between the upstream heat transfer tube group and the downstream heat transfer tube group. 5. A heat exchanger according to claim 3 or 4, characterized in that it has a a gas channel through which a gas to be cooled flows; a plurality of heat transfer tubes provided in the gas channel; A heat radiating member provided on the outer circumference of the side heat transfer tube and a temperature of the frost layer adhering surface of at least one of the upstream heat transfer tube and the heat radiating member is maintained below 0°C and higher than the gas to be cooled. A defrosting method for a heat exchanger comprising an upstream heating section,
During operation of the heat exchanger, the upstream heating unit maintains the frost layer adhesion surface temperature of at least one of the upstream heat transfer tube and the heat radiating member at a temperature lower than 0° C. and higher than the gas to be cooled at all times. comprising an upstream heating step ,
the heat radiating member has, between the flow direction tip portion and the downstream portion of the heat radiating member, a heat insulating region that suppresses heat transfer between the flow direction tip portion and the downstream portion;
While cooling the gas to be cooled by flowing a refrigerant through one or more downstream heat transfer tubes that form a downstream heat transfer surface together with the downstream portion of the heat radiating member, the upstream heat transfer tube or Adjusting the temperature of the frost layer adhering surface of at least one of the heat radiating members
A method of defrosting a heat exchanger, characterized by: The plurality of heat transfer tubes extend in the gas flow path along a first direction orthogonal to a flow direction of the gas to be cooled in the gas flow path, and extend in the flow direction and the first direction. A plurality of heat transfer tube rows formed by the plurality of heat transfer tubes arranged along the orthogonal second direction are arranged so as to be aligned in the flow direction,
The heat exchanger includes a defrost unit for defrosting a defrost target tube among the plurality of heat transfer tubes,
the gas flow channel includes a plurality of flow channel regions aligned in the second direction;
The plurality of heat transfer tubes respectively correspond to the plurality of flow path regions and belong to two or more heat transfer tube arrays adjacent to each other in the flow direction in the same flow direction region. comprising a plurality of heat transfer tube groups formed by
The defrosting unit is configured to selectively defrost the heat transfer tubes of one or more of the heat transfer tube groups among the plurality of heat transfer tube groups as the defrosting target tubes,
12. The method of defrosting a heat exchanger according to claim 11 , further comprising a defrosting step of defrosting for each of at least one of said heat transfer tube groups out of said plurality of heat transfer tube groups. The defrost unit is configured to selectively defrost only the heat transfer tube row on the most upstream side in the flow direction among the plurality of heat transfer tube rows as the defrost target tube,
13. The method of defrosting a heat exchanger according to claim 12 , wherein the defrosting step includes a step of selectively defrosting only the heat transfer tube rows on the most upstream side in the flow direction as the defrosting target tubes. a gas channel through which a gas to be cooled flows; a plurality of heat transfer tubes provided in the gas channel; an upstream heating unit for maintaining a frost layer adhered surface temperature of at least one of the side heat transfer tubes and the heat dissipating members provided on the outer periphery of the upstream heat transfer tubes at less than 0° C. and higher than the temperature of the gas to be cooled; A method of defrosting a heat exchanger comprising:
During operation of the heat exchanger, the upstream heating unit maintains the frost layer adhesion surface temperature of at least one of the upstream heat transfer tube and the heat radiating member at a temperature lower than 0° C. and higher than the gas to be cooled at all times. comprising an upstream heating step,
The plurality of heat transfer tubes extend in the gas flow path along a first direction orthogonal to a flow direction of the gas to be cooled in the gas flow path, and extend in the flow direction and the first direction. A plurality of heat transfer tube rows formed by the plurality of heat transfer tubes arranged along the orthogonal second direction are arranged so as to be aligned in the flow direction,
The heat exchanger includes a defrost unit for defrosting a defrost target tube among the plurality of heat transfer tubes,
the gas flow channel includes a plurality of flow channel regions aligned in the second direction;
The plurality of heat transfer tubes respectively correspond to the plurality of flow path regions and belong to two or more heat transfer tube arrays adjacent to each other in the flow direction in the same flow direction region. comprising a plurality of heat transfer tube groups formed by
The defrosting unit is configured to selectively defrost the heat transfer tubes of one or more of the heat transfer tube groups among the plurality of heat transfer tube groups as the defrosting target tubes,
A defrosting step of defrosting one or more of the plurality of heat transfer tube groups for each of the heat transfer tube groups,
In the defrosting step,
A defrosting method for a heat exchanger in which the flow direction is reversed when the heat transfer tube group arranged on the upstream side in the flow direction is to be defrosted.

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