JP2020079681A - Heat exchanger and heat exchanger defrosting method - Google Patents

Abstract

To prevent frost adhering to an upstream side heat transfer pipe and a fin tip from growing and closing a cooling gas flow channel, and inhibiting thermal efficiency of a heat exchanger in operation from being deteriorated due to the heat required for defrosting by executing an efficient defrosting operation.SOLUTION: A heat exchanger includes: a gas flow channel in which cooled gas flows; a plurality of heat transfer pipes provided in the gas flow channel; and an upstream side heating part for keeping frost layer adhesion surface temperature at lower than 0°C and higher than the temperature of the cooled gas for at least one of one or more upstream side heat transfer pipes located in an upstream side area in a flow direction of the cooled gas of the plurality of heat transfer pipes, and a heat radiation member provided in the outer periphery of the upstream side heat transfer pipes.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a heat exchanger and a heat exchanger defrosting method.

  A fin-tube heat exchanger is used as a heat exchanger such as an air cooler provided in a freezer or a freezer. In the fin tube type heat exchanger, radiating fins are likely to be covered with frost, and the frost layer formed between the fins blocks the air flow, so that frequent defrost operation is required. Therefore, the present inventors have proposed a defrosting method of sublimating and removing frost attached to the fins and heat transfer tubes (Patent Document 1). In this defrost method, frost is sublimated and scattered on the air flow, so that no melt water is generated. Therefore, there is an advantage that the work of removing the melted water from the heat exchanger becomes unnecessary and defrosting can be performed while the air cooler continues to operate.

International Publication No. 2017/175411

  In the flow direction, the heat transfer surface of the most upstream heat transfer tube 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 tips of the fins due to inertial force. The phenomenon occurs in which frost is concentrated and frost grows faster. Therefore, since the cooling air flow passage is closed earlier in these portions due to the growth of the frost layer than in other portions, there is a problem that the heat exchange between the cooled air and the cooling medium flowing through the heat transfer tube is hindered.

  One embodiment prevents the frost attached to the upstream end portions of the upstream heat transfer tubes and the fins from growing and blocking the cooling gas flow path, and by performing an efficient defrost operation, the defrost operation An object of the present invention is to suppress a decrease in thermal efficiency of a heat exchanger in operation due to heat applied to a heat transfer tube or fins.

(1) The heat exchanger according to one embodiment is
A gas flow path through which the cooled gas flows,
A plurality of heat transfer tubes provided in the gas flow path,
Of the plurality of heat transfer tubes, at least one frost layer of at least one upstream heat transfer tube located in an upstream region in the flow direction of the gas to be cooled or a heat radiation member provided on the outer periphery of the upstream heat transfer tube. An upstream heating unit for maintaining the temperature of the adhering surface below 0° C. and higher than the gas to be cooled;
Equipped with.

According to the above configuration (1), the surface temperature of the heat radiating member (hereinafter, also referred to as “upstream heat radiating member”) provided on the upstream heat transfer tube or the outer circumference of the upstream heat transfer tube by the upstream heating unit. By adjusting the temperature range (upstream heating), the frost attached to the upstream heat transfer tube or the upstream heat dissipation member can be sublimated and scattered. This suppresses the growth of the frost layer on the heat transfer surface formed by the upstream heat transfer tube and the upstream heat dissipation member (hereinafter also referred to as the "upstream heat transfer surface"), and the gas around the heat transfer surface due to the frost layer. The blockage of the flow path can be suppressed. By performing the heating on the upstream side constantly or at a fairly high frequency, the growth of the frost layer is suppressed and the transfer by the frost layer is suppressed only by making the temperature of the frost layer adhering surface on the upstream heat transfer surface slightly higher than the gas to be cooled. It is possible to suppress clogging of the gas flow path around the hot surface and save energy.
Even if there is a part of the upstream heat transfer tube and the upstream heat radiating member that is not maintained in the above temperature range, it is premised that the part is maintained at a temperature not to exceed 0°C. This is because if there is a portion where the temperature is 0° C. or higher, molten water will be generated at that portion.

(2) In one embodiment, in the configuration of (1) above,
The plurality of heat transfer tubes extend in the gas flow path along a first direction orthogonal to the flow direction in the gas flow path, and a second direction orthogonal to the flow direction and the first direction. A heat transfer tube row formed by the plurality of heat transfer tubes arranged along the direction is arranged so as to be lined up in the flow direction,
The upstream heat transfer tubes include at least one or more heat transfer tubes belonging to the heat transfer tube row on the most upstream side in the flow direction.
Here, the "most upstream heat transfer tube row" is meant to include one row or a plurality of heat transfer tube rows provided on the most upstream side.
According to the configuration of (2), the most upstream side heat transfer tube array 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. As a result, it is possible to suppress the growth of the frost layer in the uppermost stream side heat transfer tube row where frost is likely to grow rapidly and to prevent the gas flow passage around the upstream heat transfer surface from being blocked.

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

  According to the configuration of (3) above, by appropriately selecting the order of performing defrosting according to the difference in frost growth of each heat transfer tube group, it is possible to prevent blockage of the gas flow path in each heat transfer tube group and to improve efficiency. Defrosting can be performed, and frost separated from the upstream frost-attached surface can be prevented from reattaching to the heat-transfer surface downstream in the flow direction. By using the defrosting operation and the upstream heating together, it is possible to effectively prevent the gas passage around the heat transfer surface from being blocked.

(4) In one embodiment, in the configuration of (3) above,
The defrost unit is configured to selectively defrost only the heat transfer tube row on the most upstream side in the flow direction of the plurality of heat transfer tube rows as the defrosting target tube.
According to the configuration of (4) above, by selectively defrosting only the heat transfer tube row on the most upstream side in the flow direction as a target tube for defrosting, the heat transfer tube row on the most upstream side where frost tends to rapidly grow is preferentially defrosted. It is possible to suppress the blockage of the gas flow path of the most upstream heat transfer tube array.

(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 defrost fluid.
According to the above configuration (5), the upstream heat transfer tube only supplies the defrost fluid and does not perform the normal cooling operation. By supplying a defrosting fluid having a temperature at which sublimation defrosting is possible to the upstream heat transfer tube, it is possible to perform upstream heating capable of suppressing rapid growth of frost. Moreover, since the upstream heat transfer tube does not perform the cooling operation, it is possible to constantly perform the upstream heating, and thus it is possible to constantly suppress the growth of the frost layer.

(6) In one embodiment, in any of the configurations of (1) to (5) above,
The upstream heating unit is configured to heat the upstream heat transfer tube or the heat dissipation member.
According to the configuration of (6), the upstream heating unit heats the upstream heat transfer tube or the upstream heat dissipation member to a temperature at which sublimation of frost is possible, thereby sublimating the frost adhering to the upstream heat transfer surface. It can be scattered and removed. In this embodiment, upstream heating is enabled by means other than the supply of defrost fluid.

(7) In one embodiment, in the configuration according to any one of (1) to (6) above,
The upstream heating unit includes a defrost fluid supply unit capable of supplying a defrost fluid capable of maintaining the temperature of the frost attachment surface to a temperature lower than 0° C. and higher than the temperature of the gas to be cooled to the upstream heat transfer tube.
With configuration (7) above, the upstream heat transfer surface can be heated by the defrost fluid supplied from the defrost fluid supply unit to the upstream heat transfer tube. The upstream heating by the defrost fluid and the upstream heating by the upstream heating unit can be used together.

(8) In one embodiment, in any one of the configurations (1) to (7) above,
The upstream heating unit is configured to maintain the temperature difference between the frost layer adhering surface temperature of at least one of the upstream heat transfer tube or the upstream heat dissipation member and the gas to be cooled to more than 0°C and 10°C or less. It
According to the configuration of (8) above, 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. it can.

(9) In one embodiment, in any one of the configurations (1) to (8),
The heat dissipation member is a plate-shaped heat dissipation member provided along the flow direction in the gas flow path so that the plurality of heat transfer tubes penetrate or come into contact with each other.
According to the configuration of (9) above, the heat transfer area of the heat exchanger is increased by including the plate-shaped heat dissipation member, and the heat transfer performance of the heat exchanger can be improved. Moreover, since the plate-shaped heat dissipation member is provided along the flow direction of the gas to be cooled, it is possible to suppress the turbulence of the gas to be cooled. A temperature boundary layer is formed on the surface of the plate-shaped heat dissipation member in which the turbulence of the gas to be cooled is suppressed, and the temperature gradually decreases toward the surface of the plate-shaped heat dissipation member. The formation of the temperature boundary layer reduces the heat transfer coefficient of the heat transfer surface, so that the growth of the frost layer formed on the surface of the plate-shaped heat dissipation member can be suppressed. On the contrary, if the temperature boundary layer is disturbed (for example, a louver fin or the like), the heat transfer coefficient is increased and the growth of frost is promoted. By utilizing this, it is possible to optimally design the place where frost is to be grown and the place where frost is not desired, that is, the growth amount of frost in each place in relation to the heat exchange amount 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 that suppresses heat transfer between the flow direction tip portion and the downstream side portion between the flow direction tip portion and the downstream side portion of the heat radiating member.
According to the configuration of (10) above, since the heat insulating region is provided, the heat applied to the tip portion by the upstream heating unit is transmitted to the downstream portion of the heat dissipation member, and the cooling operation is performed in the downstream portion. It is possible to suppress a decrease in efficiency.

(11) In one embodiment, in the configuration of (3) or (4) above,
The heat dissipation member is
Of the plurality of heat transfer tube groups, it is arranged so as to straddle an upstream heat transfer tube group arranged on the upstream side in the flow direction and a downstream heat transfer tube group arranged on the downstream side in the flow direction from the upstream heat transfer tube group. As well as
A heat insulating region that suppresses heat transfer between the upstream heat transfer tube group and the downstream heat transfer tube group is provided at a portion of the heat dissipation member between the upstream heat transfer tube group and the downstream heat transfer tube group. .

  According to the configuration of (11) above, the plate-shaped heat dissipation 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 in the entire region other than the tip portion in the flow direction. Further, since the heat insulating zone is provided between the upstream heat transfer tube group and the downstream heat transfer tube group, when performing upstream heating, or when performing defrosting on either the upstream heat transfer tube group or the downstream heat transfer tube group. The heat applied to the heat transfer tubes or the heat radiating member by the upstream heating or the defrosting operation can be prevented from being transferred to the other heat transfer tube group in the cooling operation and lowering the cooling efficiency.

(12) A defrosting method for a heat exchanger according to one embodiment is
A gas flow path through which the gas to be cooled flows, a plurality of heat transfer tubes provided in the gas flow path, and one or more upstreams of the plurality of heat transfer tubes located in an upstream region in the flow direction of the gas to be cooled. An upstream heating unit for maintaining the frost layer adhesion surface temperature of at least one of the heat dissipation members provided on the outer periphery of the side heat transfer tube or the upstream heat transfer tube at a temperature lower than 0° C. and higher than the gas to be cooled; A method of defrosting a heat exchanger comprising:
During operation of the heat exchanger, the temperature of the frost layer attachment surface of at least one of the upstream heat transfer tube or the heat dissipation member is constantly kept below 0° C. and higher than the gas to be cooled by the upstream heating unit. 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 above 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 can be performed (upstream heating), so that the upstream heat transfer surface is Frost that adheres 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 prevent the gas flow passage around the heat transfer surface from being blocked by the frost layer.

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

  According to the method of (13) above, by appropriately selecting the order of performing defrosting according to the difference in frost growth of each heat transfer tube group, it is possible to prevent the gas flow passages from being blocked on each heat transfer surface and to improve the efficiency. Defrosting can be performed, and frost separated from the adhering surface can be suppressed from re-adhering to the heat transfer surface on the downstream side in the flow direction. By using the defrosting operation and the upstream heating together, it is possible to effectively prevent the gas passage around the heat transfer surface from being blocked.

(14) In one embodiment, in the method of (13) above,
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 defrosting target tube,
The defrosting step includes a step of 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 predominantly. As a result, it is possible to suppress the growth of the frost layer in the uppermost stream side heat transfer tube row where frost is likely to grow rapidly and to prevent the gas flow passage around the upstream heat transfer surface from being blocked.

In one embodiment, in the method of (13) or (14) above,
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 at which the amount of frost adhering to at least a part of the heat transfer tubes reaches an allowable upper limit value, and from the one defrost time to the heat transfer tube group. Allocate a defrosting time interval for each.
According to the above method, by setting the limit time to an upper limit value at which the flow of the gas to be cooled is not blocked on at least a part of the heat transfer surface, the block of the gas to be cooled does not occur in each heat transfer tube group, and Defrost can be carried out efficiently.

(15) In one embodiment, in the method according to (13) or (14) above,
In the defrosting step,
When the heat transfer tube group arranged on the upstream side in the flow direction is subjected to defrosting, the flow direction is reversed.
According to the above method (15), when defrosting the heat transfer tube group arranged on the upstream side in the flow direction, the flow direction of the gas to be cooled is reversed so that the frost separated from the adhering surface is on the downstream side. It is possible to suppress re-adhesion to the heat transfer tube, and it is possible to perform processing on the upstream side. Moreover, the frost adhering to the tip portion can be efficiently removed. Furthermore, the gas to be cooled, which has been heated by the heat applied during defrosting, once returns to the upstream side and is mixed and flows into another heat transfer tube group, so that temperature unevenness in the downstream of the heat exchanger can be suppressed.

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

It is a perspective view of the heat exchanger which concerns on one Embodiment. It is a top view of the heat exchanger which concerns on one Embodiment. It is a systematic diagram of the refrigerator concerning one embodiment for sending a cooling medium to a heat exchanger. It is a block diagram of the upstream side heating part concerning one embodiment. It is a block diagram of the upstream side heating part concerning one embodiment. It is a top view of an upstream side heat dissipation member concerning one embodiment. It is a top view of an upstream side heat dissipation member concerning one embodiment. It is a top view of the upstream side heat transfer surface concerning one embodiment. It is a top view of an upstream side heat transfer surface concerning one embodiment. It is a schematic plan view of the heat exchanger which concerns on one Embodiment. It is a schematic plan view of the heat exchanger which concerns on one Embodiment. It is process drawing of the defrosting method of the heat exchanger which concerns on one Embodiment.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described as the embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.
For example, the expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" are strict. In addition to representing such an arrangement, it also represents a state of relative displacement, or a state of relative displacement with an angle or distance such that the same function can be obtained.
For example, expressions such as "identical", "equal", and "homogeneous" that indicate that they are in the same state are not limited to a state in which they are exactly equal to each other. It also represents the existing state.
For example, the representation of a shape such as a quadrangle or a cylinder does not only represent a shape such as a quadrangle or a cylinder in a geometrically strict sense, but also an uneven portion or a chamfer within a range where the same effect can be obtained. The shape including parts and the like is also shown.
On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one element are not exclusive expressions excluding the existence of other elements.

  FIG. 1 is a perspective view of a heat exchanger 10 (10A) according to one embodiment, and FIG. 2 is a plan view showing a part of a heat exchanger 10 (10B) according to another embodiment. The casing 12 of the heat exchanger 10 (10A, 10B) has an open front surface that flows in from the air to be cooled a and a rear surface that flows out from the air to be cooled a, and the flow of the air to be cooled a passing through the inside of the casing 12 by the operation of the fan 14 or the like. A path is formed. Inside the casing 12, a plurality of heat transfer tubes 16 are provided facing the cooling air flow path. Although the fan 14 (14a, 14b, 14c) is arranged on the downstream side in the flow direction of the casing 12 in FIG. 1, it may be arranged on the upstream side in the flow direction of the casing 12 and operated as a push-type fan. .. In the heat exchanger 10 (10B) with respect to the casing 12, the heat dissipation member 40 is provided on the outer periphery of the heat transfer tube 16. Although the heat radiating member 40 is not shown 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 the upstream heating unit 50 (50 a, 50 b, 50 c ), and the upstream heating unit 50 causes the cooled air a of the plurality of heat transfer tubes 16 to flow. The frost layer adhering surface temperature of one or more upstream heat transfer tubes 16 (16a) located in the upstream area in the flow direction, or the upstream heat dissipation member 40 (40a) provided on the outer circumference of the upstream heat transfer tubes 16 (16a). It is possible to maintain at least one of the frost layer attachment surface temperatures of less than 0° C. and higher than the cooled air a.
If there is a part of the upstream heat transfer tube 16 (16a) and the upstream heat radiating member 40 (40a) that is not maintained within the above temperature range, the temperature of that part 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, frost-melting water is generated at that portion.

  During the cooling operation of the heat exchanger 10, the upstream heating unit 50 constantly adjusts the surface temperature of the upstream heat transfer tube 16 (16a) or the upstream heat radiating member 40 (40a) to the above temperature range in which sublimation defrosting is possible. .. As a result, the frost attached to the upstream heat transfer surface formed by the upstream heat transfer tube 16 (16a) and the upstream heat dissipation member 40 (40a) can be sublimated and scattered, so that the frost on the upstream heat transfer surface. It is possible to suppress the growth of the layer and to prevent the air passage around the heat transfer surface from being blocked by the frost layer. In addition, by constantly performing the upstream heating, the growth of the frost layer on the upstream heat transfer surface is suppressed only by making the temperature of the frost layer adhering surface slightly higher than the air to be cooled a (light temperature heating). It is possible to prevent the gas passage around the heat transfer surface from being blocked by the frost layer.

  In one embodiment, the plurality of heat transfer tubes 16 constituting the heat exchanger 10 (10A) shown in FIG. 1 are in the cooling air flow path in a direction orthogonal to the flow direction of the cooled air a (arrow b direction. And a direction (arrow c direction; hereinafter also referred to as "second direction") extending along the "first direction") and orthogonal to the flow direction of the cooled air a and the first direction. A plurality of heat transfer tube rows formed by the plurality of heat transfer tubes 16 arranged in parallel are arranged so as to be aligned 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 row of heat transfer tubes on the most upstream side in the flow direction to the above temperature range. Frost attached to the heat transfer surface formed in the side heat transfer tube row can be sublimated and scattered intensively. As a result, it is possible to suppress the growth of the frost layer in the uppermost stream side heat transfer tube array where frost is likely to grow rapidly and to prevent the cooling air flow passages around the heat transfer surface from being blocked.

  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 passage includes a plurality of flow passage regions Fa, Fb, and Fc arranged in the second direction, and the plurality of heat transfer tubes 16 correspond to the plurality of flow passage regions Fa to Fc, respectively. , And a plurality of heat transfer tube groups Ta, Tb, Tc,... Formed by a plurality of heat transfer tubes 16 belonging to two or more heat transfer tube rows adjacent to each other in the flow direction within the same flow path region. .. In FIG. 1, the plurality of heat transfer tube groups are not shown in the flow path regions Fb and Fc, but the flow path regions Fb and Fc also include a plurality of heat transfer tube groups like the flow path region 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 defrosting target tubes.

  In one embodiment, as shown in FIG. 1, the fan 14 (14a, 14b, 14c) is provided in each flow passage region Fa, Fb, and Fc, and selects the flow of the cooled air a for each flow passage region. Can be formed as desired. Further, as shown in FIG. 1, a plurality of heat transfer tube groups Ta, Tb, Tc are sequentially arranged from the upstream side in the flow direction, and the upstream heat transfer tube 16 (16a) constitutes a heat transfer tube group Ta provided on the upstream side. Is a part of the heat transfer tubes arranged on the upstream side.

  In the above configuration, one or more heat transfer tube groups are selected as the defrosting target tubes from the plurality of heat transfer tube groups, and defrosting is performed from the selected heat transfer tube group. By appropriately selecting the order of defrosting, the frost separated from the adhering surface at the time of defrosting is prevented on the downstream side while preventing the cooling air flow passage around the heat transfer surface formed on the surface of the heat transfer tube 16 or the heat dissipation member 40 from being blocked. Reattachment to the heat transfer surface can be suppressed. For example, in the heat transfer tube group to which the same flow passage region belongs to the same flow passage region among the plurality of flow passage regions Fa, Fb, and Fc, defrosting is performed simultaneously on both the upstream side and the downstream side, so that the frost layer separated from the upstream-side adhered surface is on 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 heat transfer tube group on the downstream side in the flow direction in which the frost layer grows slowly. Alternatively, as described later, the blocking time of the air flow path on the heat transfer surface is obtained for each heat transfer tube group, and at least one defrost operation is performed per blocking time of each heat transfer tube group.

  In one embodiment, as shown in FIG. 3, the refrigerator 20 supplies the refrigerant to the heat transfer tubes 16 to cool the cooled air a during the cooling operation. The defrost unit 18 supplies the defrost fluid to the heat transfer tube group to be defrosted during defrosting. The refrigerant circulating in the refrigerant circuit 22 is sucked into the compressor 24 in a gaseous state, pressurized by the compressor 24, cooled by the condenser 26, and liquefied. The refrigerant liquid liquefied by the condenser 26 is once stored in the receiver 28, and then depressurized via the expansion valve 30. The refrigerant whose pressure has been reduced by the expansion valve 30 is non-returned except for the heat transfer tube group Ta (Ta, Tb and Tc) of the upstream side heat transfer tube 16 (16a) of the heat exchanger 10 which is the defrosting target heat transfer tube group Ta. 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 cooled air a to a predetermined cooling temperature. The refrigerant that has been used to cool the cooled air a is returned to the refrigerant circuit 22.

  As the defrosting fluid, a refrigerant (gas phase portion) under high pressure in the receiver 28 is stored in the buffer tank 45 and is supplied to the heat transfer tube group that has been defrosted through the defrosting flow path 34. The refrigerant under high pressure is stored in the buffer tank 45 after adjusting the temperature, pressure, and other conditions. The control unit 48 controls the opening degree of the pressure adjusting 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 controls the defrosting refrigerant gas flowing through the defrosting passage 34. , When it is sent to the heat transfer tube group that is the target of defrosting, the frost adhesion surface temperature is adjusted to a temperature lower than 0° C. so that it can be maintained at a temperature higher than that of the air to be cooled a, and the sublimation defrosting is adjusted. The adjusted defrosting refrigerant gas is sent to the heat transfer tube group that is the object of defrosting. The refrigerant gas provided for 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 vaporized and gasified through another heat transfer tube group and is returned to the refrigerant circuit 22. A pressure reducing valve such as an electromagnetic valve or an expansion valve may be used as a pressure reducing mechanism instead of the capillary tube 38.

In one embodiment, as shown in FIG. 3, the upstream heating unit 50 (50a) has a temperature of the heat transfer surface where frost adheres to the upstream heat transfer pipe 16 (16a) at a temperature of less than 0° C. and less than 0° C. during defrosting. It includes a defrost fluid supply unit 44 capable of supplying a defrost fluid that can be maintained at a temperature higher than the temperature of the cooling air a. The defrost fluid supply unit 44 includes a buffer tank 45 and a heating unit 46. The defrost fluid supply unit 44 supplies, for example, a defrost fluid that can maintain the frost attachment surface temperature at a temperature of −2° C. to −5° C. The defrost fluid supply unit 44 supplies the defrost fluid capable of maintaining the temperature of the frost adhering surface below 0° C. and higher than the temperature of the cooled air “a” to the heat transfer tube group that is the object of defrost. This enables sublimation defrost to sublime and remove the frost attached to the frost layer attachment surface.
Further, by supplying the defrost fluid, which is adjusted to allow sublimation of frost, to the upstream heat transfer pipe 16 (16a), upstream heating becomes possible. Frost, which cannot be handled by upstream heating due to its structure, can be dealt with by defrosting operation.

  In the refrigerator 20 shown in FIG. 3, the defrost fluid is a refrigerant under high pressure that is stored in the receiver 28 and is supplied through the defrost flow passage 34. By using this refrigerant as the defrost fluid, it is not necessary to obtain the defrost heat source from another heat source.

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

In one embodiment, as shown in FIG. 3, a defrost flow passage 35 that supplies the defrost fluid from the buffer tank 45 to only the upstream heat transfer pipe 16 (16a) that is the most upstream heat transfer pipe array is provided. Only the defrost operation is performed for the heat transfer tube row of the upstream heat transfer tube 16 (16a), and the normal cooling operation is not performed in this embodiment. By supplying the defrost fluid in a state of temperature, pressure, etc., which allows constant sublimation defrost, to the heat transfer tube row of the upstream heat transfer tube 16 (16a), upstream heating becomes possible.
In one embodiment, the temperature of the frost layer adhering surface of the upstream heat transfer tube 16 (16a), which is the most upstream heat transfer tube row, is lower than the temperature of the frost layer adhering surface of the downstream heat transfer tube group during defrosting. To be done. For example, the temperature of the defrost fluid is controlled by the pressure control valve 37 provided in the defrost flow path 35 to adjust the temperature of the frost layer adhering surface. This makes it possible to efficiently suppress the growth of the frost layer.

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

4 and 5 show another embodiment of the upstream heating section 50. The upstream heating section 50 (50b, 50c) is configured to heat the upstream heat transfer tube 16 (16a) or the upstream heat dissipation member 40 (40a). The upstream heating section 50 (50b, 50c) heats the upstream heat transfer surface formed by the upstream heat transfer tube 16 (16a) or the upstream heat dissipation member 40 (40a) to a temperature at which sublimation defrost is possible. Thus, the frost layer F attached to the upstream heat transfer surface can be sublimated and removed.
In this embodiment, upstream heating can be performed by means other than the defrost operation.

The upstream heating section 50 (50b) shown in FIG. 4 includes a high frequency current induction section 52. The high-frequency current induction section 52 is connected to the upstream heat transfer tube 16 (16a) via a conductor wire 54. The cooling medium r cooled by the refrigerator 20 flows inside the heat transfer tube 16 (16a). By flowing the high-frequency current E from the high-frequency current guide portion 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 defrosting is possible. In this case, since 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, the heating effect of the frost layer F can be improved and the high frequency current E can be increased. Energy can be saved by concentrating on the surface of the upstream heat transfer tube 16 (16a).
It should be noted that the heating target is the upstream heat dissipation member 40 (40a) instead of the upstream heat transfer tube 16 (16a), and the frost layer F attached to the upstream heat dissipation member 40 (40a) is removed by sublimation defrosting. Good.

In one embodiment, as shown in FIG. 5, on the surface of the upstream side heat dissipation member 40 (40a), a conductive material layer 58 that is heated by flowing an electric current from the current-carrying portion 56 is formed. An electric insulation layer 60 is formed inside the layer 58. The upstream heating section 50 (50b) is configured to include an energization section 56 for passing an electric current through the conductive material layer 58 through the conductive wire 54. During the defrost operation, an electric current is passed from the energizing portion 56 to the conductive material layer 58 to heat the conductive material layer 58, and the frost layer F attached to the surface of the conductive material layer 58 is heated to a temperature of less than 0°C. Then, the frost layer F is sublimated and removed. According to this embodiment, since the electrically insulating layer 60 is provided inside the conductive material layer 58, the electric current can be concentrated on the conductive material layer 58 to flow the current. Further, by reducing the film thickness of the conductive material layer 58 as much as possible, it is possible to reduce the power required for heating.
In the present embodiment, the object to be heated is the upstream heat dissipation member 40 (40a), but the upstream heat transfer tube 16 (16a) may be used instead.

  In one embodiment, the upstream heating unit 50 sets the temperature difference between the frost layer attachment surface temperature of at least one of the upstream heat transfer tube 16 (16a) and the upstream heat dissipation member 40 (40a) and the cooled air a to 0°C. It is configured to maintain above 10°C and above. This slight heating can reduce the amount of heat required as a defrost heat source during defrosting due to sublimation.

  In one embodiment, as shown in FIG. 2, a plate-shaped heat dissipation member 40 is provided along the flow direction (direction of arrow a) in the cooling air flow path so that the plurality of heat transfer tubes 16 penetrate or contact each other. .. Since the heat transfer area is increased by providing the plate-shaped heat dissipation member 40, the heat transfer performance of the heat exchanger 10 can be improved. Further, since the plate-shaped heat dissipation member 40 is provided along the flow direction of the cooled air a, it is possible to suppress the disturbance of the cooled air a. As shown in FIG. 6A, on the surface of the plate-shaped heat dissipation member 40 in which the turbulence of the cooled air a is suppressed, there is a temperature boundary layer Bt in which the temperature gradually decreases toward the surface of the plate-shaped heat dissipation member 40. It is formed. By forming this temperature boundary layer, the heat transfer coefficient of the heat transfer surface is reduced, and the growth of the frost layer formed on the surface of the plate-shaped heat dissipation member can be suppressed. FIG. 6A schematically shows the temperature distribution of the temperature 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 each other at intervals along the flow direction. In this way, since the plate-shaped heat dissipation member 40 is arranged along the flow direction of the cooled air a, it is possible to suppress the disturbance of the cooled air a, and a plurality of them are arranged in parallel, so that the heat transfer area is increased. The heat transfer performance can be improved. Further, since the turbulence of the cooled air a can be suppressed, the temperature boundary layer Bt is formed on the surface of the plate-shaped heat dissipation member 40. This can suppress the growth of the frost layer.
Note that the plate-shaped heat dissipation member 40 can suppress the disturbance of the cooled air a to the maximum by forming the plate-shaped heat dissipation member 40. However, the plate-shaped heat dissipation member 40 is not limited to the plate-shaped heat dissipation member, and has a corrugated, louver-shaped, or wave-shaped plate shape. It may be a heat dissipation member.

  In one embodiment, the arrangement of the plurality of heat transfer tubes 16 suppresses the growth of the frost layer without forming a turbulent flow of the cooled air a, and suppresses the concentration of frost due to the attachment of mist due to inertia. From the viewpoint, it is preferable to use the lattice arrangement rather than the staggered arrangement with respect to the flow of the cooled air a. In addition, from the viewpoint of promoting heat transfer, it is desirable to arrange in a staggered manner, and it may be appropriately selected in relation to the conditions such as the heat exchange amount and the defrost cycle time.

In one embodiment, as shown in FIGS. 6A and 6B, the tip end portion 40 (40b) and the downstream side are provided between the tip end portion 40 (40b) in the flow direction of the upstream heat dissipation member 40 (40a) and the downstream side portion. It has the heat insulation area|region 62 (62a, 62b) which suppresses heat transfer between the heat transfer tubes 16. Since the heat insulating area 62 (62a, 62b) is provided, when the upstream heating section 50 (50b, 50c) performs upstream heating, the heat applied from the upstream heating section 50 to the tip portion 40 (40b) is in the cooling operation. It is possible to prevent the cooling efficiency from being lowered by being transmitted to the downstream heat transfer tube 16.
6A and 6B show an embodiment in which the heat dissipation member 40 is provided on the upstream side of the upstream heat transfer tube 16 (16a).

In the embodiment shown in FIG. 6A, the heat insulating area 62 (62a) is formed by a gap s formed to have a length such that the temperature boundary layer Bt can be maintained without interruption in the flow direction of the cooled air a. Since the air existing in the gap s has a heat insulating property, the heat insulating region can be formed by forming the gap s. 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 cooled air a, frost formation is promoted at the end of the heat dissipation member 40 formed by the gap s. It will not be done.
In the embodiment shown in FIG. 6B, the heat insulating area 62 (62b) constitutes a heat insulating area made of a material having a low thermal conductivity. The surface of this adiabatic region is formed so as not to disturb the cooled air a, and does not form a step with the other tip portion 40 (40b).
The heat insulating area 62 may be provided between the heat transfer tube groups.

In one embodiment, as shown in FIGS. 7A and 7B, the heat dissipation member 40 flows from the upstream heat transfer tube group Ta and the upstream heat transfer tube group Ta that are arranged on the upstream side in the flow direction of the plurality of heat transfer tube groups. It is arranged so as to straddle the downstream heat transfer tube group Tb arranged on the downstream side in the direction. Then, in a portion of the heat dissipation member 40 between the upstream heat transfer tube group Ta and the downstream heat transfer tube group Tb, a heat insulating region that suppresses heat transfer between the upstream heat transfer tube group Ta and the downstream heat transfer tube group Tb. 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, it is possible to suppress the growth of frost in the entire region except the flow direction tip portion 40 (40b). Further, since the heat insulation zone 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 the upstream heat transfer tube group Ta or the downstream heat transfer tube. When defrosting is performed on one side of the group Tb, it is suppressed that heat applied to the heat transfer tube 16 or the heat radiating member 40 due to upstream heating or defrosting operation is transferred to the other heat transfer tube group during cooling operation to reduce cooling efficiency. it 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 cooled air a. For example, two or more heat transfer tube groups may be arranged in the flow direction of the cooled air a, or further, the upstreammost heat transfer tube 16 (16a) on the most upstream side is set as another heat transfer tube group, and Thus, the upstream heat transfer pipe 16 (16a) on the most upstream side may be preferentially defrosted. In addition, a plurality of heat transfer tube groups may be arranged so as to be vertically stacked.
Further, 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. The plurality of heat transfer tube groups Ta, Tb, and Tc are arranged in this order from the upstream side of the cooled air 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 configured by a plurality of heat transfer tube groups Ta, Tb, and Tc.

  In the defrosting method according to the embodiment, as shown in FIG. 9, during operation of the heat exchanger 10, the upstream heating unit 50 first causes the upstream heat transfer pipe 16 (16a) or the upstream heat dissipation member 40 (40a). ) At least one of the frost layer adhering surface temperatures of 0) is constantly maintained below 0° C. and higher than the air to be cooled a (upstream heating step S10). Thereby, the frost layer adhered to the upstream heat transfer tube 16 (16a) or the upstream heat dissipation member 40 (40a) can be sublimated and removed. Therefore, by adjusting to the above temperature condition, it is possible to suppress the growth of the frost layer and always secure the cooling air flow path on the heat transfer surface.

In the upstream heating step S10, as shown in FIG. 3, a case where a defrost fluid capable of upstream heating is flowed into the heat transfer tube to heat the upstream heat transfer tube 16 (16a), and FIG. 5, FIG. 6A and FIG. As shown in FIG. 6B, there is a case where the upstream heat radiating member 40 (40a) is heated by energization or the like, and a case where these are used together as in FIGS. 4, 7A and 7B. The energization heating is performed by passing an electric current from the energization section 56 to the conductive material layer 58 of the upstream heat dissipation member 40 (40a) to heat the conductive material layer 58, and remove the frost layer F attached to the surface of the conductive material layer 58. The frost layer F is sublimated and removed by raising the temperature to below 0°C.

  In one embodiment, the plurality of heat transfer tubes 16 extend along the width direction (the arrow b direction in FIG. 1, the first direction) orthogonal to the flow direction of the cooled air 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 in the up-down direction (the arrow c direction in FIG. 1, the second direction) orthogonal to the flow direction and the width direction are arranged in the flow direction. Arranged. Further, as shown in FIG. 3, the heat exchanger 10 includes a defrost unit 18 for defrosting the defrost target pipe among the plurality of heat transfer pipes 16, and the cooling air flow passage has a plurality of flow passages arranged in the vertical direction. It includes regions Fa, Fb and Fc. The plurality of heat transfer tubes 16 are formed by a plurality of heat transfer tubes that respectively correspond to the plurality of flow path areas Fa to Fc and belong to two or more heat transfer tube rows adjacent to each other in the same flow path area in the flow direction. , The plurality of heat transfer tube groups Ta, Tb, Tc,... Are included, and the defrost unit 18 selectively defrosts the heat transfer tubes 16 of one or more heat transfer tube groups among the plurality of heat transfer tube groups as defrosting target tubes. Is configured to do. In the heat exchanger 10 having such a configuration, defrosting is performed for each one or more heat transfer tube groups among the plurality of heat transfer tube groups (defrosting step S12).

  According to the defrosting step S12, at the time of defrosting, by appropriately selecting the order of defrosting according to the difference in frost growth of each heat transfer tube group Ta, Tb, Tc,... It is possible to perform efficient defrosting while preventing the blockage of the flow path, and it is possible to suppress the re-adhesion of the frost separated from the adhesion surface to the heat transfer surface on the downstream side in the flow direction. By using the defrosting operation and the upstream heating together, it is possible to effectively prevent the gas passage around the heat transfer surface from being blocked.

In one embodiment, the defrost unit 18 is configured to selectively defrost only the upstream heat transfer tube 16 (16a), which is the heat transfer tube row on the most upstream side in the flow direction among the plurality of heat transfer tube rows, as the defrosting target tube. To be done. Then, in the defrosting step S12, the upstream heat transfer tube 16 (16a) in the flow direction is selectively defrosted as the 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, and the upstream heat transfer pipe 16 (16a) can be defrosted. The growth of frost on the heat transfer tube 16 (16a) can be suppressed.

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

In one embodiment, the defrosting time interval of each of the plurality of heat transfer tube groups is set to the downstream side in the flow direction because the growth of frost tends to be slower in the heat transfer tube group on the downstream side in the flow direction of the cooled air a. The arranged heat transfer tube group is set longer.
According to this embodiment, by setting the defrost execution time interval to be longer in the heat transfer tube group on the downstream side in the flow direction of the cooled air a, it is possible to reduce the frequency of defrost operation, and thus the heat exchanger during the defrost operation. It can suppress that the cooling efficiency of 10 falls.

In one embodiment, in the defrosting step S12, the defrosting fluid capable of maintaining the frost attachment surface temperature below 0° C. and higher than the temperature of the gas to be cooled is transferred to the heat transfer tubes 16 of the heat transfer tube group which is the defrosting target. The frost adhered to the heat transfer tube 16 is sublimated by the retained heat of the defrost fluid (sublimation defrost step S12b). The defrost fluid is, for example, a refrigerant under high pressure that is stored in the receiver 28 and supplied through the defrost flow passage 34 in the refrigerator 20 shown in FIG.
According to this embodiment, by supplying the defrost fluid capable of maintaining the frost adhesion surface temperature below 0° C. and higher than the temperature of the gas to be cooled to the heat transfer tube 16 for defrosting, the frost adhesion surface adheres to the adhesion surface. Sublimation defrost that sublimates and removes frost is possible.

  In one embodiment, in the defrost 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 on the downstream side in the flow direction of the air to be cooled a. To be done. The smaller the temperature difference between the cooled air a and the defrost fluid, the smaller the frost removal effect. Therefore, the cooling efficiency of the heat exchanger 10 can be suppressed from decreasing while maintaining the frost removal effect by reducing the above-mentioned temperature difference toward the downstream side in the flow direction where the growth of frost is slow.

In one embodiment, in the defrost step S12, when the heat transfer tube group to be defrosted is arranged on the upstream side in the flow direction of the cooled air a, the fan 14 is rotated in the reverse direction to reverse the flow direction (backflow). Step S12c).
According to this embodiment, when defrosting the heat transfer tube group arranged on the upstream side in the flow direction, by making the flow direction of the cooled air a reverse, the frost separated from the adhering surface causes the frost on the downstream side. It is possible to suppress re-adhesion to the surface and to perform processing on the upstream side. Moreover, the frost adhering to the tip portion can be efficiently removed. Further, the gas to be cooled, which has been heated by the heat applied during the defrosting, once returns to the upstream side and is mixed and flows into another heat transfer tube group, so that temperature unevenness on the downstream side of the heat exchanger 10 can be suppressed.

  According to some embodiments, it is possible to prevent the frost adhering to the tips of the upstream heat transfer pipes and the heat dissipation member from growing and blocking the cooling gas flow path, and it becomes possible to perform an efficient defrost operation. It is possible to suppress a decrease in the thermal efficiency of the heat exchanger during the cooling operation due to the heat applied to the heat transfer tubes and the fins during the defrost 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 path 24 Compressor 26 Condenser 28 Receiver 30 Expansion valve 32 Reverse Stop valve 34, 35 Defrost flow path 36, 37 Pressure adjusting valve 38 Capillary tube 40 Heat dissipation member 40a Upstream heat dissipation member 40b Tip part 44 Defrost fluid supply part 45 Buffer tank 46 Heating part 47 Pressure sensor 48 Control part 50 (50a, 50b) , 50c) Upstream heating part 52 High frequency current induction part 54 Conductive wire 56 Conducting part 58 Conductive material layer 60 Electrical insulating layer 62 (62a, 62b) Thermal insulation area Bt Temperature boundary layer
F Frost layer Fa, Fb, Fc Flow path region Ta, Tb, Tc Heat transfer tube group a Cooled air r Cooling medium s Gap

Claims (15)

A gas flow path through which the cooled gas flows,
A plurality of heat transfer tubes provided in the gas flow path,
Of the plurality of heat transfer tubes, at least one frost layer of at least one upstream heat transfer tube located in an upstream region in the flow direction of the gas to be cooled or a heat dissipation member provided on the outer periphery of the upstream heat transfer tube. An upstream heating unit for maintaining the temperature of the adhered surface below 0° C. and higher than the gas to be cooled;
A heat exchanger comprising: The plurality of heat transfer tubes extend in the gas flow path along a first direction orthogonal to the flow direction in the gas flow path, and a second direction orthogonal to the flow direction and the first direction. A heat transfer tube row formed by the plurality of heat transfer tubes arranged along the direction is arranged so as to be lined up in the flow direction,
The heat exchanger according to claim 1, wherein the upstream heat transfer tube includes at least one heat transfer tube belonging to the heat transfer tube row on the most upstream side in the flow direction. A defrost unit for defrosting a defrost target tube among the plurality of heat transfer tubes,
The gas flow path includes a plurality of flow path regions arranged in the second direction,
The plurality of heat transfer tubes respectively correspond to the plurality of flow path areas and belong to two or more heat transfer tube rows adjacent to each other in the same flow path area in the flow direction. Including a plurality of heat transfer tube groups formed by
The defrost unit is configured to selectively defrost the heat transfer tubes of one or more heat transfer tube groups of the plurality of heat transfer tube groups as the defrost target tubes. The heat exchanger described.   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 defrosting target tube. The heat exchanger described in.   The heat exchanger according to claim 1, wherein the upstream heat transfer pipe is configured to be able to supply only a defrost fluid.   The heat exchanger according to claim 1, wherein the upstream heating unit is configured to heat the upstream heat transfer tube or the heat dissipation member.   The upstream heating unit includes a defrost fluid supply unit capable of supplying a defrost fluid capable of maintaining the temperature of the frost attachment surface to be lower than 0° C. and higher than the temperature of the gas to be cooled to the upstream heat transfer tube. The heat exchanger according to claim 1, wherein the heat exchanger is a heat exchanger.   The upstream heating unit is configured to maintain the temperature difference between the frost layer adhering surface temperature of at least one of the upstream heat transfer tube or the heat dissipation member and the gas to be cooled to more than 0° C. and 10° C. or less. The heat exchanger according to claim 1, wherein the heat exchanger is a heat exchanger.   9. The heat dissipating member is a plate-shaped heat dissipating member provided along the flow direction in the gas flow path so that the plurality of heat transfer tubes penetrate or contact each other. The heat exchanger according to claim 1.   The heat dissipating member has a heat insulating region between the tip portion in the flow direction of the heat dissipating member and a downstream side portion that suppresses heat transfer between the tip portion in the flow direction and the downstream side portion. The heat exchanger according to any one of claims 1 to 9. The heat dissipation member is
Of the plurality of heat transfer tube groups, it is arranged so as to straddle an upstream heat transfer tube group arranged on the upstream side in the flow direction and a downstream heat transfer tube group arranged on the downstream side in the flow direction from the upstream heat transfer tube group. As well as
A heat insulating region that suppresses 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. The heat exchanger according to claim 3, wherein the heat exchanger is a heat exchanger. A gas flow path through which the gas to be cooled flows, a plurality of heat transfer tubes provided in the gas flow path, and one or more upstreams of the plurality of heat transfer tubes located in an upstream region in the flow direction of the gas to be cooled. An upstream heating unit for maintaining the frost layer adhesion surface temperature of at least one of the heat dissipation members provided on the outer periphery of the side heat transfer tube or the upstream heat transfer tube at a temperature lower than 0° C. and higher than the gas to be cooled; A method of defrosting a heat exchanger comprising:
During operation of the heat exchanger, the temperature of the frost layer attachment surface of at least one of the upstream heat transfer tube or the heat dissipation member is constantly kept below 0° C. and higher than the gas to be cooled by the upstream heating unit. A defrosting method for a heat exchanger, comprising an upstream heating step. The plurality of heat transfer tubes extend in the gas flow path along a first direction orthogonal to the flow direction of the gas to be cooled in the gas flow path, and in the flow direction and the first direction. A heat transfer tube array formed by a plurality of the heat transfer tubes arranged along a second direction orthogonal to each other is arranged so as to be lined up in the flow direction,
The heat exchanger includes a defrost unit for defrosting a defrost target pipe among the plurality of heat transfer pipes,
The gas flow path includes a plurality of flow path regions arranged in the second direction,
The plurality of heat transfer tubes respectively correspond to the plurality of flow path areas and belong to two or more heat transfer tube rows adjacent to each other in the same flow path area in the flow direction. Including a plurality of heat transfer tube groups formed by
The defrost unit is configured to selectively defrost the heat transfer tubes of one or more heat transfer tube groups of the plurality of heat transfer tube groups as the defrost target tubes,
The defrosting method for a heat exchanger according to claim 12, further comprising a defrosting step of defrosting each of the one or more heat transfer tube groups out of the 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 defrosting target tube,
The defrosting method for a heat exchanger according to claim 13, wherein the defrosting step includes a step of selectively defrosting only the heat transfer tube row on the most upstream side in the flow direction as the defrosting target tube. In the defrosting step,
The defrosting method for a heat exchanger according to claim 13 or 14, wherein when the heat transfer tube group arranged on the upstream side in the flow direction is subjected to defrosting, the flow direction is reversed.

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