JP7208768B2 - 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

However, in the sublimation defrost method, the frosted surface must be heated to a temperature lower than 0°C and higher than the temperature of the air to be cooled. There is a problem that In addition, there is a problem that the frost once peeled off from the adhering surface rides on the air flow and re-adheres to the heat transfer tubes and fins on the downstream side.
Moreover, even if defrosting is performed for each of a plurality of sections, the amount of frost formation differs depending on the flow direction of the gas to be cooled in the heat exchanger, so the defrosting operation must be continued until the entire heat exchanger is completely defrosted There is Therefore, there is a problem that the operating efficiency of the cooling device is deteriorated.

One embodiment can suppress a decrease in the thermal efficiency of the heat exchanger due to defrost operation, and can suppress re-adhesion of frost that has separated from the adhered surface during defrost to the heat transfer surface on the downstream side. An object of the present invention is to propose a defrosting means capable of efficiently operating a cooling device while suppressing wasteful defrosting heating of a heat exchanger.

(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 extending 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;
a defrosting unit for defrosting a defrosting target tube among the plurality of heat transfer tubes;
with
The plurality of heat transfer tubes are arranged such that a plurality of heat transfer tube rows formed by the plurality of heat transfer tubes arranged along a second direction orthogonal to the flow direction and the first direction are aligned in the flow direction. is,
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.

In the above configuration (1), the plurality of heat transfer tubes provided in the gas flow path are configured by a plurality of heat transfer tube groups, and the defrosting unit causes the heat transfer tubes constituting one or more heat transfer tube groups to be defrosted. Selectively defrosted. Since the degree of frost adhesion and growth differs for each heat transfer tube group, the time during which the gas flow path is blocked by the grown frost layer differs for each heat transfer tube group. Therefore, by appropriately selecting the order of defrosting each heat transfer tube group, while preventing the clogging of the gas flow path on the heat transfer surface formed by the heat transfer tubes, the deterioration of the thermal efficiency of the heat exchanger due to the defrosting operation is suppressed, In addition, it is possible to suppress re-adherence of frost separated from the adhering surface during defrosting to the heat transfer surface. Furthermore, it is possible to efficiently operate the cooling device while suppressing wasteful defrost heating of the heat exchanger.

(2) In one embodiment, in the configuration of (1),
The defrosting 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 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 fins due to inertia force. Then, a phenomenon occurs in which frost formation is concentrated on these parts and the growth of frost formation is accelerated.
According to the above configuration (2), by selectively defrosting only the heat transfer tube row on the most upstream side in the flow direction of the gas to be cooled as the defrosting target tube, the most upstream heat transfer tube row can be preferentially defrosted, As a result, it is possible to suppress the growth of frost on the heat transfer tube row on the most upstream side.

(3) In one embodiment, in the configuration of (1) or (2),
A plate-shaped heat radiating member is 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 (3), since the heat transfer area is increased by providing the plate-shaped heat radiating member, the heat transfer performance of the heat exchanger can be improved. 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 between the gas to be cooled and the plate-shaped heat radiating member is suppressed by the formation of this temperature boundary layer, the growth of the frost layer formed on the surface of the plate-shaped heat radiating member can be suppressed. 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. By using this, it is possible to optimally design the locations where frost is desired to grow and the locations where frost is not desired, that is, the amount of frost growth at each location in relation to the amount of heat exchange and the defrost interval.

(4) In one embodiment, in the configuration of (3),
A plurality of the plate-shaped heat-dissipating members are arranged in parallel with each other in the flow direction at intervals that do not disturb the temperature boundary layer for each of the heat-transfer tube groups.
According to the configuration (4) above, since a plurality of plate-shaped heat radiating members are arranged, the heat transfer area can be increased and the heat transfer performance can be improved. In addition, since the plate-shaped heat radiating members are arranged in parallel along the flow direction of the gas to be cooled, the turbulence of the gas to be cooled can be suppressed. By maintaining the boundary layer and suppressing the growth of the frost layer on the upstream end in the flow direction of the plate-shaped heat radiating member facing the gap, it is possible to suppress the concentration of frost formation and the partial blockage. In addition, according to this configuration, even if there is a temperature difference between the adjacent heat transfer tube groups during defrosting, the gaps serve as heat insulators, so the effect on the adjacent heat transfer tube groups is suppressed and the heat exchange efficiency is improved. Decrease can be suppressed.

(5) In one embodiment, in the configuration of (3) or (4),
The plate-shaped heat radiating member extends from the heat transfer tube provided on the most upstream side in the flow direction to one or more heat transfer tubes adjacent to the heat transfer tubes in the flow direction.
Since the thickness of the temperature boundary layer is thin at the tip portion of the plate-shaped heat radiating member, the heat transfer coefficient between the gas to be cooled and the plate-shaped heat radiating member is promoted, and the growth of frost is accelerated. Therefore, by extending the plate-shaped heat radiating member to the heat transfer tube on the downstream side, formation of a new tip portion is eliminated, and a temperature boundary layer exists in regions other than the tip portion. As a result, frost growth can be suppressed in regions other than the tip portion.

(6) In one embodiment, in any one of the configurations (3) to (5),
The plate-shaped heat radiating member is arranged so as to straddle two or more of the heat transfer tube groups in the flow direction, and a heat insulating region is formed between the heat transfer tube groups to suppress heat transfer between the heat transfer tube groups. have.
According to the above configuration (6), since the plate-shaped heat-dissipating member has the heat-insulating region that suppresses heat transfer between the heat-transfer tube groups in the region between the heat-transfer tube groups, the heat-transfer tube group on one side of the heat-insulating region is When normal cooling operation is continued and the heat transfer tube group on the other side performs defrost operation, the heat added during defrost operation is suppressed from being transferred to the heat transfer tube group in cooling operation and reducing the cooling efficiency of the heat exchanger. can.

(7) In one embodiment, in any one of the configurations (1) to (6),
The defrost unit includes one or more defrost fluids capable of maintaining a frost-adhered surface temperature of the heat transfer tubes at a temperature lower than 0° C. and higher than the temperature of the gas to be cooled for each heat transfer tube group. Includes defrost fluid supply.
According to the above configuration (7), the defrost fluid supply unit can maintain the temperature of the frosted surface of the heat transfer tube group that performs the defrost operation at a temperature lower than 0° C. and higher than the temperature of the gas to be cooled. Sublimation defrost, in which the frost adhering to the adhering surface is sublimated and removed by supplying a suitable defrost fluid, becomes possible. A plurality of defrosting fluid supply units may be provided as required.

(8) A method of defrosting a heat exchanger according to one embodiment includes:
a gas flow path through which a gas to be cooled flows; a plurality of heat transfer tubes extending 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; a defrosting unit for defrosting a defrosting target tube among the heat transfer tubes, wherein the plurality of heat transfer tubes are arranged along a second direction orthogonal to the flow direction and the first direction. A plurality of heat transfer tube rows formed by heat tubes are arranged in the flow direction of the gas to be cooled, and the gas flow path includes a plurality of flow path regions aligned in the second direction, and the plurality of heat transfer tube rows are arranged in the second direction. The heat tubes are formed of a plurality of heat transfer tubes belonging to two or more heat transfer tube rows that correspond to the plurality of flow path regions and are adjacent to each other in the flow direction within the same flow path region. A method of defrosting a heat exchanger including a plurality of heat transfer tube groups, comprising:
A defrosting step is provided in which one or more heat transfer tube groups are selected from the plurality of heat transfer tube groups as defrosting target tubes, and the one or more heat transfer tube groups are sequentially and repeatedly defrosted.

In the above method (8), in the defrosting step, one or more heat transfer tube groups among the plurality of heat transfer tube groups are selected as defrost target tubes, and the one or more heat transfer tube groups are sequentially and repeatedly defrosted. Therefore, by appropriately selecting the order in which each heat transfer tube group is defrosted, it is possible to prevent the gas to be cooled around the heat transfer surface from being clogged by the frost layer, and to suppress the deterioration of the thermal efficiency of the heat exchanger due to the heat applied during defrosting. In addition, it is possible to suppress re-adherence of frost separated from the adhering surface during defrosting to the heat transfer surface on the downstream side. Furthermore, it is possible to efficiently operate the cooling device while suppressing wasteful defrost heating of the heat exchanger.

(9) In one embodiment, in the method of (8),
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 (9), in the defrosting step, only the heat transfer tube row on the most upstream side in the flow direction of the gas to be cooled is selectively defrosted as the defrosting target tube, thereby giving priority to the most upstream heat transfer tube row. It is possible to defrost the heat transfer tube row at the most upstream side and suppress the growth of frost formation on the most upstream heat transfer tube row.

(10) In one embodiment, in the method of (8) or (9),
In the defrosting step,
One defrost time required to defrost all the heat transfer tube groups once is set in accordance with the limit time for the frost amount adhering to at least part of the heat transfer tubes to reach the upper limit of the allowable value, and the one defrost time to set the defrosting time interval for each of the heat transfer tube groups.
According to the method (10) above, by setting the limit time to the upper limit value at which the flow of the gas to be cooled is not blocked, the defrost operation can be performed so as not to block the gas to be cooled in each heat transfer tube group. .

(11) In one embodiment, in the method of (10),
The defrost execution time interval for each of the plurality of heat transfer tube groups is set longer for the heat transfer tube groups located further downstream in the flow direction.
The growth of frost tends to be slower toward the downstream side in the flow direction of the cooled gas. Therefore, by setting the defrost implementation time interval to be longer for the downstream heat transfer tube group in the flow direction where the frost growth is slower, the frequency of the defrost operation can be reduced, thereby suppressing the decrease in cooling efficiency due to the defrost operation.

(12) In one embodiment, in the method of any one of (8) to (11),
In the defrosting step,
A defrosting fluid capable of maintaining a temperature of the surface on which frost adheres is lower than 0° C. and higher than the temperature of the gas to be cooled is supplied to the heat transfer tubes, and the frost adhering to the heat transfer tubes is sublimated by the inherent heat of the defrosting fluid. Let
According to the method (12) above, by supplying a defrost fluid capable of maintaining the temperature of the frosted surface below 0° C. and higher than the temperature of the gas to be cooled to the heat transfer tubes that perform the defrost operation. , sublimation defrost, which sublimates and removes the frost adhering to the adhering surface, becomes possible.

(13) In one embodiment, in the method of (12),
In the defrosting step,
In each of the plurality of heat transfer tube groups, the temperature difference between the gas to be cooled and the defrost fluid is set to be smaller for the heat transfer tube group located further downstream in the flow direction.
As the temperature difference between the gas to be cooled and the defrost fluid decreases, the frost removal effect decreases, but the decrease in thermal efficiency of the heat exchanger during cooling operation can be suppressed. 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 prevent the gas passage from being clogged due to frost, and to suppress the decrease in the cooling efficiency of the heat exchanger.

(14) In one embodiment, in the method of any one of (8) to (13),
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 (14), 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 that has separated from the adhering surface is removed from 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 has been raised by the defrost heat source 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, the reduction in the thermal efficiency of the heat exchanger due to the defrost operation is suppressed while preventing the clogging of the gas flow path on the heat transfer surface, and the frost peeled off from the adhering surface during the defrost is removed from the heat transfer surface. reattachment can be suppressed. Furthermore, it is possible to efficiently operate the cooling device while suppressing wasteful defrost heating of the heat exchanger.

1 is a perspective view of a heat exchanger according to one embodiment; FIG. 3 is a system diagram of a refrigeration unit and a defrost unit according to one embodiment; FIG. 1 is a plan view of a heat exchanger according to one embodiment; FIG. It is a top view of the plate-shaped heat radiating member which concerns on one Embodiment. It is a top view of the plate-shaped heat radiating member which concerns on one Embodiment. It is a mimetic diagram by plane view of a heat exchanger concerning one embodiment. It is a mimetic diagram by plane view of a heat exchanger concerning one embodiment. 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 schematically showing a heat exchanger according to one embodiment. A heat exchanger 10 shown in FIG. 1 is an air cooler provided in, for example, a freezer or a freezer. The casing 12 of the heat exchanger 10 has an open front surface into which the air to be cooled a flows and a rear surface out of which the air to be cooled a flows. A flow path for the air to be cooled a flowing out from is formed. A plurality of heat transfer tubes 16 are provided in this cooling air flow path. The heat transfer tubes 16 extend along the width direction (arrow b direction) (first direction) perpendicular to the flow direction (arrow a direction) of the air to be cooled a in the cooling air flow path.

Further, as shown in FIG. 2, a defrosting unit 18 is provided for defrosting a heat transfer tube 16 selected as a defrosting target tube among the plurality of heat transfer tubes 16 . The plurality of heat transfer tubes 16 are arranged in a vertical direction (direction of arrow c) perpendicular to the flow direction of the air to be cooled a and the direction of arrow b. are arranged so that multiple In FIG. 1, the heat transfer tubes 16 are shown only in the upper region within the casing 12, and the illustration of the heat transfer tubes 16 in other regions is omitted. As in the upper region, there are multiple heat transfer tube groups.

The cooling air flow path includes a plurality of flow path areas Fa, Fb and Fc aligned in the direction of arrow c. The plurality of heat transfer tubes 16 are formed by a plurality of heat transfer tubes 16 that correspond to the plurality of flow path regions Fa to Fc and belong to two or more heat transfer tube rows that are adjacent to each other in the flow direction within the same flow path region. including a plurality of heat transfer tube groups Ta, Tb, Tc, . . . 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.

The defrosting unit 18 selectively defrosts one or more of the heat transfer tube groups Ta, Tb, Tc, . . . as defrosting target tubes. Since the degree of frost adhesion and growth differs for each heat transfer tube group, the time during which the gas flow path is blocked by the grown frost layer differs for each heat transfer tube group. Therefore, by appropriately selecting the order of defrosting each heat transfer tube group, the heat applied during defrosting reduces the thermal efficiency of the heat exchanger 10 while preventing the blockage of the air flow path on the heat transfer surface of each heat transfer tube group. can be suppressed, and re-adherence of frost separated from the adhered surface during defrosting to the heat transfer surface can be suppressed. Furthermore, it is possible to efficiently operate the cooling device while suppressing wasteful defrost heating of the heat exchanger (heating applied to the heat transfer tubes by the heat retained by the defrost fluid).

For example, the closing time due to frost formation in the air flow path around the heat transfer surface is obtained for each heat transfer tube group, and the defrosting operation is performed at least once per closing time in each heat transfer tube group. As a result, blockage of the air flow path of each heat transfer tube group can be suppressed. Alternatively, in the same flow path region, the defrost operation is performed simultaneously on the upstream heat transfer tube group and the downstream heat transfer tube group. As a result, it is possible to suppress reattachment of frost peeled off from the upstream heat transfer tubes to the downstream heat transfer tubes. Alternatively, as will be described later, the defrost time interval is lengthened for the downstream heat transfer tube group in which the growth of frost is slow. As a result, it is possible to suppress a decrease in thermal efficiency of the heat exchanger due to defrosting.

FIG. 2 shows a refrigerator 20 that supplies refrigerant to the heat transfer tubes 16 during the cooling operation of the heat exchanger 10 to cool the air a to be cooled, and a defrosting unit that supplies defrosting fluid to the heat transfer tube groups to be defrosted during the defrosting operation. 18 shows an embodiment of the configuration of 18. FIG. 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 supplied to the heat transfer tubes 16 of the heat exchanger 10 through the check valves 32 provided in each of the heat transfer tube groups Ta, Tb, and Tc of the heat exchanger 10, and the air to be cooled a is cooled 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 portion) in the receiver 28 is stored in the buffer tank 44 and supplied through the defrost flow path 34 to the heat transfer tube group serving as the defrost target tube. This high-pressure refrigerant is stored in the buffer tank 44 after its temperature, pressure, etc. are adjusted. That is, the pressure is reduced through the pressure regulating valve 36 and heated by the heating unit 46 to adjust the conditions such as temperature and pressure. This defrosting refrigerant gas is sent to the heat transfer tube group that is the target tube for defrosting, and is subjected to defrosting in this heat transfer tube group. After being condensed and liquefied inside the heat transfer tube, the refrigerant gas is expanded and decompressed through the capillary tube 38 and joins the low-pressure refrigerant line. After that, it is evaporatively gasified through another heat transfer tube group and returned to the refrigerant circuit 22 . Incidentally, this capillary tube 38 may be an electromagnetic valve or an expansion valve.
In one embodiment, the refrigerant circuit 22 and the defrost flow path 34 are provided with electromagnetic valves 47 and 49 for opening and closing.

In one embodiment, the defrosting unit 18 selectively selects only the most upstream heat transfer tube row in the flow direction (in this embodiment, the heat transfer tube row belonging to the heat transfer tube group Ta) among the plurality of heat transfer tube rows as defrost target tubes. configured to defrost; The most upstream heat transfer tube row has a high heat transfer coefficient, and the mist (liquid and solid) contained in the gas to be cooled collides with the upstream tip portion due to inertial force, which promotes frost accumulation and stacking. As a result, frost formation is concentrated on the most upstream heat transfer tube row, and the growth of frost formation is accelerated. Therefore, it is effective to concentrate the defrost operation on the most upstream heat transfer tube row.
According to this embodiment, by selectively defrosting only the most upstream heat transfer tube row (heat transfer tube group Ta) in the flow direction of the air to be cooled a, the most upstream heat transfer tube row is prioritized. can be used to increase the defrost frequency. Therefore, it is possible to suppress the growth of frost formation on the most upstream heat transfer tube row, and conversely, to reduce the frequency of defrosting in the downstream heat transfer tube group, thereby achieving energy saving.

In one embodiment, as shown in FIG. 3, 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 penetrate 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. 4A, a temperature boundary layer Bt is formed on the surface of the plate-shaped heat radiating member 40 where the turbulence of the air to be cooled a is suppressed. be. Due to the formation of this temperature boundary layer, the heat transfer coefficient between the air to be cooled a and the plate-shaped heat radiating member 40 is lowered, so that the growth of the frost layer formed on the surface of the plate-shaped heat radiating member 40 can be suppressed. FIG. 4A schematically shows the temperature distribution of the thermal boundary layer Bt.

The temperature boundary layer Bt becomes thinner toward the upstream side. Therefore, heat transfer between the air to be cooled a and the cooling medium flowing in the heat transfer tubes 16 is promoted as it goes upstream. Therefore, it is assumed that the amount of frost adhered to the upstream end portion 40a of the plate-shaped heat radiating member 40 increases during normal cooling operation. Conversely, on the downstream side in the flow direction, the formation of this temperature boundary layer Bt can suppress the growth of the frost layer formed on the surface of the plate-shaped heat radiating member 40 .

In one embodiment, as shown in FIG. 3, a plurality of plate-shaped heat radiating members 40 are arranged in parallel along the flow direction at intervals so as not to disturb the temperature boundary layer Bt for each heat transfer tube group. By arranging the plurality of plate-shaped heat radiating members 40, the heat transfer area is increased and the heat transfer performance can be improved. Further, since the plate-shaped heat radiating member 40 is arranged along the flow direction of the air to be cooled a, disturbance of the air to be cooled a can be suppressed. In addition, since the plurality of plate-shaped heat radiating members 40 are arranged for each heat transfer tube group at intervals so as not to disturb the temperature boundary layer Bt, the gap between the plate-shaped heat radiating members of the adjacent heat transfer tube groups is reduced. By maintaining the temperature boundary layer Bt and suppressing the growth of the frost layer on the upstream end in the flow direction of the plate-shaped heat radiating member facing the gap, it is possible to suppress the concentration of frost formation and the partial blockage. In addition, according to this configuration, even if there is a temperature difference between the adjacent heat transfer tube groups during defrosting, the gaps serve as heat insulators, so the effect on the adjacent heat transfer tube groups is suppressed and the heat exchange efficiency is improved. Decrease can be suppressed.
The plate-shaped heat radiating member 40 can suppress the turbulence of the air to be cooled a to the maximum by making it flat, but it is not limited to the flat heat-radiating member, and may have a corrugated shape, a louver shape, or a wave shape.

In one embodiment, the arrangement of the plurality of heat transfer tubes 16 suppresses the growth of a frost layer without forming turbulence in 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 FIG. 3, the plate-shaped heat radiating member 40 extends from the heat transfer tube 16 (16a) provided on the most upstream side in the flow direction of the air to be cooled a to the heat transfer tube 16 (16a) in the flow direction. It extends to one or more adjacent heat transfer tubes 16 . As described above, since the temperature boundary layer Bt is thin in the upstream end portion 40a of the plate-shaped heat radiating member 40, the growth of frost is accelerated. Therefore, by extending the plate-shaped heat radiating member 40 to the heat transfer tube 16 on the downstream side, the second tip portion is not formed. In this way, the temperature boundary layer Bt can be continuously formed to the downstream side, and the growth of frost formation can be suppressed by not stopping the temperature boundary layer Bt to the downstream side.

In one embodiment, as shown in FIGS. 4A and 4B, the plate-shaped heat radiating member 40 is arranged so as to straddle two or more heat transfer tube groups Ta and Tb in the flow direction of the air to be cooled a. A heat insulating region 42 (42a, 42b) for suppressing heat transfer between the heat transfer tube groups is provided in the region between the heat transfer tube groups.
According to this embodiment, since the heat-insulating region 42 is provided in the region between the heat-transfer tube groups of the plate-shaped heat-dissipating member 40, the heat-transfer tube group Ta on one side of the heat-insulating region 42 performs the cooling operation, while the heat-transfer tube group Ta on the other side performs cooling operation. When Tb performs the defrost operation, it is possible to prevent the heat applied during the defrost from being transmitted to the heat transfer tube group during the cooling operation and reducing the cooling efficiency of the heat exchanger 10 .

In the embodiment shown in FIG. 4A, the heat insulating region 42 (42a) is composed of a gap formed with 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 existing in this gap has heat insulating properties, a heat insulating area can be formed by forming the gap. In addition, since this gap 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 is formed at the end of the plate-like heat radiating member 40 that is interrupted by this gap. Suppressed.
In the embodiment shown in FIG. 4B, the heat insulating zone 42 (42b) constitutes a heat 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.

In one embodiment, as shown in FIG. 2, the defrost unit 18 can maintain the surface temperature of the frosted heat transfer tubes 16 of each heat transfer tube group at a temperature lower than 0° C. and higher than the temperature of the air to be cooled a. A defrost fluid supply unit 50 capable of supplying defrost fluid is provided. As described in Patent Document 1, the temperature of the frost adhered surface is maintained at less than 0 ° C. and higher than the temperature of the air to be cooled a during defrosting, so that the frost layer adhered to the adhered surface is sublimated, can be scattered. For example, the temperature of the frosted surface is maintained at -2°C to -5°C.
According to this embodiment, the defrost fluid supply unit 50 supplies the defrost fluid capable of maintaining the temperature of the frosted surface within the above temperature range to the heat transfer tube group that performs the defrost operation. Sublimation defrost, which sublimates and removes adhering frost, becomes possible.

In one embodiment, the defrost fluid supply 50 includes a buffer tank 44 provided in the defrost channel 34 . The buffer tank 44 is provided with a heating unit 46 for heating the defrost fluid stored in the buffer tank 44 , and the control unit 48 controls the opening degree of the pressure regulating valve 36 and also controls the heating unit 46 . , The temperature, pressure, etc. of the cooling medium supplied to the heat transfer tube group during the defrost operation are controlled so that the temperature of the frosted surface can be maintained at a temperature lower than 0°C and higher than the temperature of the air to be cooled a. .

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 groups of heat transfer tubes may be arranged in the flow direction of the air to be cooled a. Also, a plurality of heat transfer tube groups may be stacked vertically.
Further, as shown in FIG. 5A, 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. 5B is an example in which the heat transfer tube group is divided into a plurality of flow path regions Fa, Fb and Fc, and each flow path region is configured with a plurality of heat transfer tube groups Ta, Tb and Tc. Furthermore, the fan 14 may be arranged upstream of a plurality of heat transfer tube groups and operated as a forced-type fan.

A defrosting method for a heat exchanger according to one embodiment relates to a defrosting method using the heat exchanger 10 shown in FIG. That is, the heat exchanger 10 includes a cooling air flow path through which the air to be cooled a flows, and a direction perpendicular to the flow direction of the air to be cooled a in the cooling air flow path (arrow b direction/ a plurality of heat transfer tubes 16 extending along the first direction), and a defrosting unit 18 for defrosting a defrost target tube among the plurality of heat transfer tubes 16 . The plurality of heat transfer tubes 16 are formed by a plurality of heat transfer tubes 16 arranged along the flow direction of the air to be cooled a (direction of arrow a) and the direction perpendicular to the direction of arrow b (direction of arrow c/second direction). A plurality of heat transfer tube rows are arranged in the flow direction of the air to be cooled a. The cooling air flow path includes a plurality of flow path areas Fa, Fb, and Fc aligned in the direction of arrow c, and the plurality of heat transfer tubes 16 correspond to these flow path areas and are located within the same flow path area. includes a plurality of heat transfer tube groups Ta, Tb and 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 of the air to be cooled a.

As shown in FIG. 6, this defrosting method selects one or more heat transfer tube groups from a plurality of heat transfer tube groups Ta, Tb, and Tc as defrosting target tubes, and sequentially defrosts each of the one or more heat transfer tube groups. defrosting repeatedly (defrosting step S10).
According to the above method, one or more heat transfer tube groups among the plurality of heat transfer tube groups Ta, Tb, Tc . While preventing blockage of the air a, it is possible to suppress a decrease in thermal efficiency of the heat exchanger 10 due to the defrost operation, and to suppress reattachment of frost separated from the adhering surface during defrosting to the heat transfer surface on the downstream side. Furthermore, it is possible to efficiently operate the cooling device while suppressing wasteful defrost heating of the heat exchanger.

In one embodiment, as shown in FIG. 2 , the defrost unit 18 includes only the most upstream heat transfer tube row in the flow direction (in this embodiment, the heat transfer tube row belonging to the heat transfer tube group Ta) among the plurality of heat transfer tube rows. The defrosting step S10 selectively defrosts only the heat transfer tube row (heat transfer tube group Ta) on the most upstream side in the flow direction of the air to be cooled a (heat transfer tube group Ta) as the defrost target tube. (Step S10a).
In this way, by selectively defrosting only the most upstream heat transfer tube row in the flow direction of the air to be cooled a, the growth of frost on the most upstream heat transfer tube row can be suppressed.

In one embodiment, in the defrost step S10, one defrost required to defrost all the heat transfer tube groups once is set in accordance with the limit time for the frost amount adhering to at least a part of the heat transfer tubes 16 to reach the upper limit of the allowable value. A time is set, and from this one defrost time, a 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 close the gaps between the plate-shaped heat radiating members 40, etc., in each heat transfer tube group, The defrost operation can be performed so as not to clog the flow path of the air to be cooled a.

In one embodiment, the defrosting time interval for each of the heat transfer tube groups is set longer for the heat transfer tube groups arranged downstream in the flow direction. Frost growth tends to slow down in the heat transfer tube group downstream in the flow direction of the air to be cooled a.
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, thereby enabling heat exchange during the defrost operation. A decrease in the cooling efficiency of the vessel 10 can be suppressed.

In one embodiment, in the defrosting step S10, a defrosting fluid capable of maintaining a frost-adhering surface temperature of less than 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 defrosting fluid, the inherent heat of the defrosting fluid sublimates the frost adhering to the heat transfer tubes 16 (sublimation defrosting step S10b). As the defrosting fluid, for example, high-temperature refrigerant gas on the compressor discharge side of the refrigerator 20 is used.
According to this embodiment, by supplying the defrosting fluid capable of maintaining the temperature of the surface of the frost adhering to less than 0° C. and higher than the temperature of the gas to be cooled to the heat transfer tubes 16 that perform the defrosting operation, Sublimation defrost, which sublimates and removes frost adhering to the surface, becomes possible.

In one embodiment, in the defrosting step S10, 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. As the temperature difference between the gas to be cooled and the defrost fluid decreases, the effect of removing frost formation decreases, but the frost layer grows slower toward the downstream side. 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 S10, 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 S10c). As shown in FIG. 1, by providing fans 14 (14a, 14b, 14c) for each of the flow path areas Fa, Fb, and Fc, only the heat transfer tube group to be defrosted can reverse the flow of the air to be cooled a. .
According to this embodiment, by reversing the flow direction of the air to be cooled a during the defrosting operation, it is possible to suppress the reattachment of the frost that has separated from the adhered surface to the heat transfer tubes 16 on the downstream side, and the frost on the upstream side. It is possible to process with Also, the frost adhering to the tip portion can be removed efficiently. Furthermore, the air to be cooled a heated by the defrost heat source returns to the upstream side once, 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, in a heat exchanger such as an air cooler installed in a freezer, freezer, or the like, it is possible to prevent the heat transfer surface from being clogged with the gas to be cooled, while preventing the thermal efficiency of the heat exchanger from decreasing due to the defrost operation. In addition, it is possible to suppress reattachment of frost that has separated from the adhered surface during defrosting to the heat transfer surface. Furthermore, it is possible to realize a defrosting means capable of operating the cooling device efficiently while suppressing wasteful defrosting heating of the heat exchanger.

10 Heat Exchanger 12 Casing 14 (14a, 14b, 14c) Fan 16 Heat Transfer Tube 18 Defrost Unit 20 Refrigerator 22 Refrigerant Circuit 24 Compressor 26 Condenser 28 Receiver 30 Expansion Valve 32 Check Valve 34 Defrost Channel 36 Pressure Regulating Valve 38 Capillary tube 40 Plate-like heat radiating member 40a Tip portion 42 (42a, 42b) Thermal insulation area 44 Buffer tank 46 Heating unit 47, 49 Solenoid valve 48 Control unit 50 Defrost fluid supply unit Bt Temperature boundary layer
Fa, Fb, Fc Flow path area Ta, Tb, Tc Heat transfer tube group a Air to be cooled

Claims (14)

a gas flow path through which the gas to be cooled flows;
a plurality of heat transfer tubes extending 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;
a defrosting unit for defrosting a defrosting target tube among the plurality of heat transfer tubes;
with
The plurality of heat transfer tubes are arranged such that a plurality of heat transfer tube rows formed by the plurality of heat transfer tubes arranged along a second direction orthogonal to the flow direction and the first direction are aligned in the flow direction. is,
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 ,
The defrost unit is
A defrosting fluid capable of maintaining a temperature of the surface on which frost adheres is lower than 0° C. and higher than the temperature of the gas to be cooled is supplied to the heat transfer tubes, and the frost adhering to the heat transfer tubes is sublimated by the inherent heat of the defrosting fluid. and
In each of the plurality of heat transfer tube groups, the temperature difference between the gas to be cooled and the defrost fluid is set smaller for the heat transfer tube group arranged downstream in the flow direction.
configured as
A heat exchanger characterized by: 2. The defrost 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. A heat exchanger as described. 3. The heat exchanger according to claim 1, further comprising a plate-shaped heat radiating member provided along the flow direction in the gas flow path so that the plurality of heat transfer tubes penetrate through or contact with each other. a gas flow path through which the gas to be cooled flows;
a plurality of heat transfer tubes extending 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;
a defrosting unit for defrosting a defrosting target tube among the plurality of heat transfer tubes;
with
The plurality of heat transfer tubes are arranged such that a plurality of heat transfer tube rows formed by the plurality of heat transfer tubes arranged along a second direction orthogonal to the flow direction and the first direction are aligned in the flow direction. is,
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 plate-shaped heat radiating member provided along the flow direction in the gas flow path so that the plurality of heat transfer tubes penetrate or contact,
A heat exchanger according to claim 1, wherein a plurality of said plate-shaped heat radiating members are arranged in parallel with each other for each heat transfer tube group along said flow direction at intervals not to disturb a temperature boundary layer. 3. The plate-shaped heat radiating member extends from the heat transfer tube provided most upstream in the flow direction to one or more heat transfer tubes adjacent to the heat transfer tube in the flow direction. Or the heat exchanger according to 4. The plate-shaped heat radiating member is arranged so as to straddle two or more of the heat transfer tube groups in the flow direction, and a heat insulating region is formed between the heat transfer tube groups to suppress heat transfer between the heat transfer tube groups. 6. A heat exchanger as claimed in any one of claims 3 to 5, characterized in that it comprises: The defrost unit includes one or more defrost fluids capable of maintaining a frost-adhered surface temperature of the heat transfer tubes at a temperature lower than 0° C. and higher than the temperature of the gas to be cooled for each heat transfer tube group. 7. A heat exchanger as claimed in any one of claims 4 to 6, comprising a defrost fluid supply. a gas flow path through which a gas to be cooled flows; a plurality of heat transfer tubes extending 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; a defrosting unit for defrosting a defrosting target tube among the heat transfer tubes, wherein the plurality of heat transfer tubes are arranged along a second direction orthogonal to the flow direction and the first direction. A plurality of heat transfer tube rows formed by heat tubes are arranged in the flow direction of the gas to be cooled, and the gas flow path includes a plurality of flow path regions aligned in the second direction, and the plurality of heat transfer tube rows are arranged in the second direction. The heat tubes are formed of a plurality of heat transfer tubes that correspond to the plurality of flow path regions and belong to two or more heat transfer tube rows that are adjacent to each other in the flow direction within the same flow path region. A method of defrosting a heat exchanger including a plurality of heat transfer tube groups, comprising:
a defrosting step of selecting one or more heat transfer tube groups from the plurality of heat transfer tube groups as defrosting target tubes, and sequentially and repeatedly defrosting each of the one or more heat transfer tube groups ;
In the defrosting step,
A defrosting fluid capable of maintaining a temperature of the surface on which frost adheres is lower than 0° C. and higher than the temperature of the gas to be cooled is supplied to the heat transfer tubes, and the frost adhering to the heat transfer tubes is sublimated by the inherent heat of the defrosting fluid. and
In each of the plurality of heat transfer tube groups, the temperature difference between the gas to be cooled and the defrost fluid is set to be smaller for the heat transfer tube group disposed further downstream in the flow direction.
A method of defrosting a heat exchanger, characterized by: 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,
9. The method of defrosting a heat exchanger according to claim 8, 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. In the defrosting step,
One defrost time required to defrost all the heat transfer tube groups once is set in accordance with the limit time for the frost amount adhering to at least part of the heat transfer tubes to reach the upper limit of the allowable value, and the one defrost time 10. The defrosting method for a heat exchanger according to claim 8, wherein the defrosting execution time interval for each of the heat transfer tube groups is set from . 11. The defrost of the heat exchanger according to claim 10, wherein the defrost execution time interval for each of the plurality of heat transfer tube groups is set longer for the heat transfer tube groups located further downstream in the flow direction. Method. a gas flow path through which a gas to be cooled flows; a plurality of heat transfer tubes extending 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; a defrosting unit for defrosting a defrosting target tube among the heat transfer tubes, wherein the plurality of heat transfer tubes are arranged along a second direction orthogonal to the flow direction and the first direction. A plurality of heat transfer tube rows formed by heat tubes are arranged in the flow direction of the gas to be cooled, and the gas flow path includes a plurality of flow path regions aligned in the second direction, and the plurality of heat transfer tube rows are arranged in the second direction. The heat tubes are formed of a plurality of heat transfer tubes that correspond to the plurality of flow path regions and belong to two or more heat transfer tube rows that are adjacent to each other in the flow direction within the same flow path region. A method of defrosting a heat exchanger including a plurality of heat transfer tube groups, comprising:
a defrosting step of selecting one or more heat transfer tube groups from the plurality of heat transfer tube groups as defrosting target tubes, and sequentially and repeatedly defrosting each of the one or more heat transfer tube groups;
In the defrosting step,
When the heat transfer tube group arranged upstream in the flow direction is subject to defrosting, the flow direction is reversed.
A method of defrosting a heat exchanger, characterized by: In the defrosting step,
A defrosting fluid capable of maintaining a temperature of the surface on which frost adheres is lower than 0° C. and higher than the temperature of the gas to be cooled is supplied to the heat transfer tubes, and the frost adhering to the heat transfer tubes is sublimated by the inherent heat of the defrosting fluid. 13. The method of defrosting a heat exchanger according to claim 12 , wherein In the defrosting step,
14. The method according to claim 13 , wherein in each of the plurality of heat transfer tube groups, the temperature difference between the gas to be cooled and the defrost fluid is set to be smaller for the heat transfer tube group arranged on the downstream side in the flow direction. A method of defrosting the described heat exchanger.

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