JP6678235B2 - Heat exchanger - Google Patents

Description

  The present invention relates to a heat exchanger using a refrigerant that forms a gas-liquid two-phase flow.

  In recent years, heat exchangers used in heat pump systems have been reduced in diameter for heat transfer tubes for the purpose of reducing ventilation resistance outside the tubes and improving heat transfer performance in the tubes. Since the pressure loss in the heat transfer tubes increases as the diameter is reduced, the pressure loss is reduced by combining a plurality of heat transfer tubes and forming the flow paths in parallel.

  As a conventional heat exchanger, for example, there is one described in Patent Document 1. In Patent Literature 1, a flat multi-hole tube having a plurality of minute holes, a header for arranging a plurality of the flat multi-hole tubes in parallel and fixing both ends thereof, and a contact with the flat multi-hole tube An air-cooled micro-tube heat exchanger having corrugated fins arranged in a row is shown. In Patent Literature 1, the refrigerant flows in the respective slots in parallel.

  Further, as another example of the heat exchanger, there is one described in Patent Document 2, for example. In this patent document 2, in a multi-pass heat exchanger in which a plurality of heat transfer thin tubes are connected between an inlet header and an outlet header that are vertically separated from each other and mesh fins are provided in the heat transfer thin tube portion, A gas-liquid separation type heat exchanger is shown in which an opening and an outlet header opening are connected by a gas-liquid separation tube of a predetermined length, and a gas-liquid two-phase refrigerant supply pipe is connected to the upper portion of the gas-liquid separation tube. ing.

JP 2001-263681 A JP-A-6-117728

  In the multi-parallel heat exchanger as described in Patent Document 1, when the gas-liquid two-phase flow refrigerant flowing from the header on the inlet side is distributed to each of the long holes, the refrigerant is distributed with an equal gas-liquid ratio. There was a task that could not be done. For this reason, in the long holes in which the liquid refrigerant is distributed less than in the other long holes, the liquid refrigerant evaporates immediately due to the heat from the external air side, and the temperature in the long holes increases. There was a problem that the exchange performance deteriorated. Furthermore, in the long holes where the liquid refrigerant is distributed more than the other long holes, the liquid refrigerant cannot completely evaporate, so that liquid compression occurs in the downstream compressor and the compressor may be damaged. There was an issue.

  Further, in the heat exchanger described in Patent Literature 2 in which the space between the inlet and outlet headers is bypassed by the gas-liquid separator, only the liquid refrigerant flows into the heat transfer tube, so that the distribution of the refrigerant can be made uniform. However, in the vicinity of the heat transfer tube inlet, since the liquid is in a single-phase state, the heat transfer performance on the refrigerant side is reduced as compared with the two-phase flow state, and heat from the external air side is not efficiently transmitted to the refrigerant. there were.

  An object of the present invention is to provide a heat exchanger having a plurality of heat transfer tubes, to make the gas-liquid ratio of the refrigerant distributed and supplied to each of the heat transfer tubes uniform, and to enhance the heat transfer performance of the heat transfer tubes. is there.

  In order to achieve the above object, a heat exchanger of the present invention includes an inlet header, an outlet header, and a plurality of heat transfer tubes disposed therebetween, and the inside of the heat transfer tube has a refrigerant flow path. The lower end of the heat transfer tube is disposed inside the inlet header, and the heat transfer tube inside the inlet header has a through hole provided so that the gas refrigerant flows into the heat transfer tube.

  According to the present invention, in a heat exchanger having a plurality of heat transfer tubes, the gas-liquid ratio of the refrigerant to be distributed and supplied to each heat transfer tube is made uniform, and a two-phase flow is formed at the heat transfer tube inlet. Heat transfer performance can be improved.

FIG. 2 is a perspective view illustrating the heat exchanger according to the first embodiment. It is sectional drawing which shows the internal structure of the entrance header 11 of FIG. 1 is a schematic configuration diagram illustrating a heat pump system according to a first embodiment. It is a perspective view showing the heat exchanger of Example 2. FIG. 6 is a schematic configuration diagram illustrating a heat pump system according to a second embodiment. FIG. 5 is a sectional view showing the internal structure of the entrance header 11 of FIG. FIG. 13 is a partial perspective view illustrating the vicinity of an inlet header of the heat exchanger according to the third embodiment. It is a fragmentary sectional view which shows the bottom part of the entrance header 11 of FIG.

  The present invention relates to a heat exchanger used for flowing a low-temperature gas-liquid two-phase flow refrigerant therein and exchanging heat with an external high-temperature heat source in a heat pump using a phase change of a refrigerant. The heat pump is applied to a refrigerator, a water heater, an air conditioner, and the like.

  Hereinafter, specific examples according to the heat exchanger of the present invention will be described with reference to the drawings. In the respective drawings, the portions denoted by the same reference numerals indicate the same or corresponding portions.

  The first embodiment will be described with reference to FIGS.

  First, the configuration of the heat exchanger of the present embodiment will be described with reference to FIG.

  FIG. 1 is a perspective view showing the heat exchanger of the present embodiment.

  In FIG. 1, the heat exchanger 1 includes an inlet header 11, an outlet header 12, a plurality of heat transfer tubes 13, fins 14, a liquid pipe 15, a gas pipe 16, an outlet pipe 17, and the like. G in FIG. 1 indicates the direction of gravity. A plurality of heat transfer tubes 13 and fins 14 are arranged between the inlet header 11 and the outlet header 12. The fins 14 are for improving heat transfer characteristics with the outside of the heat transfer tube 13.

  A plurality of heat transfer tubes 13, a liquid pipe 15, and a gas pipe 16 are connected to the inlet header 11. In this embodiment, the inlet header 11 is configured so that the refrigerant flowing from the liquid pipe 15 and the gas pipe 16 can flow to the plurality of heat transfer tubes 13. Then, the refrigerant that has passed through the heat transfer tube 13 passes through the outlet header 12 and flows out to the outlet pipe 17.

  FIG. 2 is a sectional view showing the internal structure of the entrance header 11 of FIG. FIG. 2 is a cross-sectional view including the line segment AA ′ in FIG. G in FIG. 2 indicates the direction of gravity as in FIG.

  In FIG. 2, the inlet header 11 is divided into a liquid reservoir 115 and a gas reservoir 116. The heat transfer tube 13 penetrates the gas reservoir 116 from above the inlet header 11 and reaches the liquid reservoir 115. A hole 131 (through hole) is provided in the region of the gas reservoir 116 of the heat transfer tube 13 so that the gas refrigerant flows into the heat transfer tube 13. In other words, the holes 131 (through holes) penetrate from the outer wall surface of the heat transfer tube 13 to the inner wall surface.

  Although the liquid pipe 15 and the gas pipe 16 do not penetrate to the inside of the inlet header 11, they are shown by broken lines in order to clarify the positional relationship between the liquid reservoir 115 and the gas reservoir 116.

  Before flowing into the heat exchanger 1, the refrigerant is separated into a liquid refrigerant and a gas refrigerant by a gas-liquid separator arranged on the upstream side of the heat exchanger 1. The separated liquid refrigerant flows from the liquid pipe 15 to the liquid reservoir 115, and the gas refrigerant flows from the gas pipe 16 to the gas reservoir 116, and flows to the heat transfer pipe 13. Therefore, the liquid refrigerant and the gas refrigerant that have entered the inlet header 11 remain in a state where they are separated from each other in the inlet header 11. The liquid refrigerant flowing into the inlet header 11 flows into the heat transfer tube 13 from the lower end of the heat transfer tube 13. On the other hand, the gas refrigerant flowing into the inlet header 11 flows into the heat transfer tube 13 from the hole 131.

  If the liquid refrigerant is vaporized in the inlet header 11 before flowing into the heat transfer tubes 13, it affects uniform distribution of the refrigerant in the plurality of heat transfer tubes 13. In order to prevent this, it is preferable that the inlet header 11 transports the refrigerant to the heat transfer tube 13 without exchanging heat as much as outside air. Therefore, the material of the inlet header 11 is preferably a material having a lower thermal conductivity than the heat transfer tube 13 that mainly exchanges heat with the outside air, and for example, a resin material or stainless steel is preferable. Even when the inlet header 11 is formed of a material having a high thermal conductivity such as copper, as in the case of the heat transfer tube 13, the liquid in the inlet header 11 is covered by covering the periphery of the inlet header 11 with a heat insulating material or the like. Evaporation of the refrigerant can be prevented.

  Next, the movement of the refrigerant from the inlet header 11 to the heat transfer tube 13 will be described.

  Since the inlet of the heat transfer tube 13 is connected to the liquid reservoir 115, first, the liquid refrigerant flows into the tube inlet (lower end) of the heat transfer tube 13. Thereafter, the gas refrigerant flows into the heat transfer tube 13 from a hole 131 provided in the heat transfer tube 13 in the gas reservoir 116. Therefore, in the heat transfer tube 13, the refrigerant flows again as a two-phase flow.

  The heat transfer tube 13 is disposed between the inlet header 11 and the outlet header 12. Further, the outside of the heat transfer tube 13 is connected to the fins 14, and heat exchange between the air around the fins 14 and the refrigerant inside the heat transfer tubes 13 can evaporate the refrigerant. Therefore, the heat transfer tube 13 is preferably made of a material having a high thermal conductivity, for example, copper or aluminum.

  In the present embodiment, the heat transfer tube 13 is a circular tube, but may be another tube shape such as an elliptical tube or a square tube. Further, a plurality of long holes may be provided in the longitudinal direction of the bar, and the heat transfer tube 13 may be configured by using each long hole as a tube. The heat transfer tube 13 is provided with a hole 131 so that a gas refrigerant can be introduced in the middle of the inlet. The shape, size, number, and position of the holes 131 are not limited to the present embodiment. The liquid refrigerant does not flow backward to the gas reservoir 116, and the refrigerant forms a slag flow in the heat transfer tube 13. It can be appropriately designed according to the inner diameter of the heat transfer tube 13, the flow rate of the refrigerant, the power of the compressor, and the like so that the heat flows to the outlet header 12.

  At the outlet header 12, the gas refrigerant gasified by the plurality of heat transfer tubes 13 rejoins and flows to the outlet pipe 17. Since the refrigerant flowing into the outlet header 12 is a single-phase gas, there is no need to separate the liquid reservoir and the gas reservoir as in the inlet header 11. Since it is not necessary to suppress the vaporization of the liquid refrigerant, the material of the outlet header 12 does not have to be a resin material or stainless steel, and a heat insulating material is not required.

The fins 14 need to efficiently transfer heat from the high-temperature air to the refrigerant in the heat transfer tubes 13.
For this reason, it is desirable that the fins 14 be made of a material having a high thermal conductivity, such as aluminum or copper, similarly to the heat transfer tubes 13. Further, in order to improve the heat transfer coefficient between the external air and the fins 14, grooves or slits may be provided in the fins 14.

  At the connection between the fins 14 and the heat transfer tubes 13, it is necessary to efficiently transfer heat. For this purpose, for example, the heat transfer tube 13 is inserted into a hole of the fin 14 that has been opened in advance, and then the heat transfer tube 13 is expanded to increase the surface pressure at the contact portion between the fin 14 and the heat transfer tube 13 or to reduce the heat conduction. It is preferable to fill the gap at the connection portion with a highly adhesive or grease, or to integrate by welding, brazing, soldering or the like. In the present embodiment, the fins 14 are provided to exchange heat between the refrigerant and the air. However, a case where heat exchange is performed with another fluid or solid such as a heat sink connected to high-temperature water or a heat source may be considered. In this case, it is preferable that the fins 14 be used as a flow path for flowing a fluid like a shell tube heat exchanger, or be integrated with a heat sink, depending on the high-temperature medium to be heat-exchanged.

  The liquid pipe 15, the gas pipe 16, and the outlet pipe 17 are provided for connecting the heat exchanger 1 to another device such as a compressor or an expansion valve. It is preferable that these materials can maintain a heat-insulated state without heat exchange with the outside so as to prevent useless heat intrusion and heat release. However, for example, in a general air conditioner or the like, the position of the device and the length of the pipe differ depending on the installation location. Therefore, a material that is easy to process in addition to maintaining heat insulation is preferable, and a material such as copper that is easy to process is used. By surrounding the outer periphery with a heat insulating material (not shown), a highly efficient heat pump system can be provided.

  Next, the configuration and operation of the heat pump system according to the present embodiment will be described with reference to FIG.

  FIG. 3 shows a schematic configuration of the heat pump system of the present embodiment.

  As shown in FIG. 1, the heat pump system 10 includes a heat exchanger 1, a condenser 2, an expansion valve 3, a compressor 4, a gas-liquid separator 5, and the like.

  The condenser 2 re-condenses the refrigerant by exchanging heat between the external working fluid such as air and water and the refrigerant compressed by the compressor 4. The re-condensed refrigerant is sent to the expansion valve 3. The expansion valve 3 adiabatically expands the refrigerant recondensed in the condenser 2. The adiabatic expanded refrigerant becomes a gas-liquid two-phase flow and flows into the gas-liquid separator 5. In the gas-liquid separator 5, the refrigerant is separated into a liquid and a gas, and flows into the heat exchanger 1 through the liquid pipe 15 and the gas pipe 16. Although the gas-liquid separator 5 is arranged outside the heat exchanger 1 in FIG. 3, the present invention is not limited to this. It may be arranged inside. Further, the gas-liquid separator 5 may be attached to the inlet header 11 of FIG. Further, the gas-liquid separator 5 may be integrated with the inlet header 11 of FIG.

  As shown in FIG. 2, the liquid refrigerant flowing into the heat exchanger 1 is equally distributed to the plurality of heat transfer tubes 13 and forms a slag flow with the gas refrigerant flowing from the holes 131 to exchange heat with the high-temperature air. And vaporize. Thereafter, the vaporized refrigerant joins again at the outlet header 12 and the outlet pipe 17, is compressed by the compressor 4, and then flows into the condenser 2 again.

  According to the present embodiment, the refrigerant separated into the liquid and the gas by the gas-liquid separator 5 is separately put into the liquid reservoir 115 and the gas reservoir 116 of the heat exchanger 1, and Refrigerant is sent evenly. Therefore, the heat transfer tubes 13 can function without waste, and the efficiency of the heat exchanger 1 can be increased.

  Furthermore, a gas-liquid two-phase slag flow can be formed in the heat transfer tube 13 by re-introducing the gas refrigerant from the hole 131 of the heat transfer tube 13. In the slag flow, as compared with the liquid single-phase flow, evaporation occurs in the thin liquid film layer between the slag bubble and the wall surface of the heat transfer tube 13, so that the heat transfer coefficient increases. Therefore, heat from the high-temperature air is efficiently transmitted to the liquid refrigerant, and a heat exchanger having high heat transfer performance can be obtained.

  In order to improve the heat transfer to the liquid refrigerant flowing through the heat transfer tube 13, the smaller the diameter of the heat transfer tube 13, the better. When the heat transfer tube 13 is a circular tube, the inner diameter is 1.0 mm or less. It is more preferable that the thickness be 0.5 mm or less. When the heat transfer tube 13 is other than a circular tube, its hydraulic equivalent diameter (diameter of the refrigerant passage) may be set to 1.0 mm or less. Also in this case, it is more preferable that the thickness be 0.5 mm or less. In this specification, the inner diameter of the circular pipe and the hydraulic equivalent diameter other than the circular pipe are both referred to as “inner diameter”.

  As the tube diameter is reduced, there is a possibility that the pressure loss increases due to the flow of the refrigerant and the heat transfer tube 13 is blocked. Therefore, it is necessary to determine the lower limit of the pipe diameter in consideration of these effects from the physical properties of the refrigerant to be used.

  In addition, the heat pump system 10 needs to determine the circulation amount of the refrigerant according to its capacity. For example, in the case of a small heat pump system of about several hundred W, the length of each heat transfer tube 13 shown in FIG. 1 is desirably 200 mm or less, more desirably 100 mm or less from the viewpoint of the pressure loss of the liquid refrigerant.

  Even in the case where the heat exchanger 1 is slightly inclined and the inlet header 11 is not kept horizontal, the liquid refrigerant is divided into the liquid reservoir 115 and the gas reservoir 116 in this embodiment. Can be maintained evenly.

  The second embodiment will be described with reference to FIGS.

  FIG. 4 is a perspective view illustrating the heat exchanger according to the second embodiment.

  As shown in FIG. 4, the present embodiment is different from the first embodiment in that the refrigerant flows into the heat exchanger 1 from the inlet pipe 18 without performing gas-liquid separation before the refrigerant flows. In response to this difference, the gas-liquid separator 5 of FIG. 3 is not used in the present embodiment, as shown in FIG. 5 described later. The internal structure of the entrance header 11 is as shown in FIG. 6 described later. Other configurations are the same as in the first embodiment.

  FIG. 5 shows a configuration of the heat pump system 10 of the present embodiment.

  As shown in this figure, the gas-liquid separator used in Example 1 was not used. Therefore, the refrigerant flows into the heat exchanger 1 in a gas-liquid two-phase flow state.

  The operation of the heat pump system 10 in the present embodiment is as follows.

In FIG. 5, the refrigerant pressurized by the compressor 4 flows into the condenser 2 where it is condensed and liquefied.
The liquid refrigerant is adiabatically expanded by the expansion valve 3 and becomes a gas-liquid two-phase flow. Then, it flows into the heat exchanger 1.
The refrigerant vaporized in the heat exchanger 1 is pressurized again by the compressor 4 and sent to the condenser 2.

  FIG. 6 shows the internal structure of the entrance header 11 of FIG. FIG. 6 is a cross-sectional view including the line AA ′ in FIG. G in FIG. 6 indicates the direction of gravity as in FIG.

  In FIG. 6, there is no partition inside the entrance header 11, and a refrigerant storage section 181 is provided. The plurality of heat transfer tubes 13 penetrating the upper portion of the inlet header 11 are arranged so as to reach a portion of the coolant storage section 181 where the liquid coolant is stored. In addition, each heat transfer tube 13 is provided with a hole 131 at a portion where the gas refrigerant is stored, so that the gas refrigerant flows into the heat transfer tube 13. In other words, normally, the liquid refrigerant flowing into the inlet header 11 does not completely evaporate in the inlet header 11 but accumulates in the inlet header 11, so that the liquid refrigerant before the steady operation is reached. The surface is higher than the lower end of the heat transfer tube 13. Therefore, if the lower end of the heat transfer tube 13 is disposed inside the inlet header 11, the liquid refrigerant flows in from the lower end of the heat transfer tube 13. Since the heat transfer tube 13 inside the inlet header 11 has the hole 131 (through hole) provided so that the gas refrigerant flows into the heat transfer tube 13, the gas refrigerant flows from the hole 131. Then, the once separated liquid refrigerant and gas refrigerant merge again. Thereby, a two-phase slag flow can be formed, and the heat transfer coefficient can be increased as compared with a liquid single-phase flow. It is desirable that the lower end of the heat transfer tube 13 is closer to the bottom surface of the inlet header 11. This is because the liquid refrigerant accumulated in the refrigerant storage section 181 reaches the lower end of the heat transfer tube 13 early. In addition, assuming that the inlet header 11 is installed horizontally, it is desirable that the lower ends of all the heat transfer tubes 13 have the same height. Thereby, the liquid level of the liquid refrigerant stored in the refrigerant storage section 181 reaches the lower end portions of all the heat transfer tubes 13 almost simultaneously.

  The gas-liquid two-phase refrigerant flowing through the expansion valve 3 shown in FIG. 5 flows into the refrigerant reservoir 181 from the inlet pipe 18. The inlet pipe 18 does not penetrate to the inside of the inlet header 11, but is shown by a broken line to clarify the connection position in the inlet header 11. Also, the liquid level of the refrigerant is shown by broken lines. As shown in FIG. 6, during a steady operation, the volume of the refrigerant reservoir 181 is set such that the refrigerant level is higher than the lower end of the heat transfer tube 13 and lower than the hole 131. And the positions of the lower end of the heat transfer tube 13 and the hole 131 are set. With such a configuration, the refrigerant is automatically separated in the refrigerant storage unit 181 due to a gas-liquid density difference.

  In FIG. 6, the inlet pipe 18 is connected to the upper part of the side surface of the refrigerant storage part 181. It is considered that the liquid refrigerant flowing from the inlet pipe 18 into the refrigerant storage unit 181 does not disturb the liquid surface of the liquid refrigerant stored in the lower part of the refrigerant storage unit 181 by arranging in this manner.

  In addition, in order to suppress the turbulence of the liquid surface of the liquid refrigerant, once a partition serving as a baffle plate (not shown) is provided for the liquid refrigerant flowing from the inlet pipe 18 into the refrigerant storage unit 181, the liquid refrigerant is once provided. Alternatively, the flow direction of the liquid refrigerant flowing from the inlet pipe 18 into the refrigerant storage unit 181 may be bent so that the liquid refrigerant meanders. In this case, it is possible to stabilize the liquid level of the liquid refrigerant without having to connect the inlet pipe 18 to the upper part of the side surface of the refrigerant storage part 181.

  The other configuration is the same as that of the first embodiment.

  Even in a configuration in which the gas-liquid separator is not provided as in the present embodiment, the same effect as in the first embodiment can be obtained.

  The inlet header 11 (FIG. 6) of the present embodiment may be provided with the gas-liquid separator 5, the liquid pipe 15, and the gas pipe 16 (FIG. 3) of the first embodiment. In this case, the refrigerant flows into the undivided inlet header 11 in a state of being separated into the liquid and the gas, and the connection position of the liquid pipe 15 in the inlet header 11 is set below the connection position of the gas pipe 16. Thereby, the state where gas and liquid are separated in the inlet header 11 is maintained.

  The third embodiment will be described with reference to FIGS.

  FIG. 7 is a partial perspective view showing the vicinity of the inlet header of the heat exchanger of the present embodiment. In this drawing, a cross section of the inlet header 11 inside the connection portion of the inlet pipe 18 of the inlet header 11 is shown so that the inside of the inlet header 11 can be seen.

  In the present embodiment, a protrusion 182 is provided below the refrigerant storage 181. The lower end of the heat transfer tube 13 is disposed below the upper surface of the projection 182. In other words, the lower end of the heat transfer tube 13 is inserted into the groove 183 between the protrusions 182.

  FIG. 8 is a partial cross-sectional view showing the bottom (the inside of the entrance header 11) of the entrance header 11 of FIG.

  In FIG. 8, each of the protrusions 182 has a rectangular parallelepiped shape, and a lattice-shaped groove 183 is formed between them. The heat transfer tube 13 is disposed in a groove 183 between the convex portions 182 (a portion where two grooves 183 intersect in this figure).

  In addition, the convex part 182 may be produced by casting together with the bottom of the entrance header 11, or may be produced by press-molding a plate-like member. Press molding is desirable in that the weight of the entrance header 11 can be reduced.

  With such a configuration, the liquid level of the refrigerant can be maintained above the inlet of the heat transfer tube 13 even when the amount of the refrigerant is smaller than in the second embodiment. Therefore, the amount of refrigerant sealed in the heat pump system 10 (FIG. 5) can be reduced.

  The present invention is not limited to the above-described embodiments, but includes various modifications. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of one embodiment can be added to the configuration of another embodiment. Further, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described above.

  1: heat exchanger, 2: condenser, 3: expansion valve, 4: compressor, 5: gas-liquid separator, 10: heat pump system, 11: inlet header, 12: outlet header, 13: heat transfer tube, 14: Fin, 15: liquid pipe, 16: gas pipe, 17: outlet pipe, 18: inlet pipe, 115: liquid storage section, 116: gas storage section, 131: hole, 181: refrigerant storage section, 182: convex section, 183 :groove.

Claims (3)

An entrance header,
An exit header,
A plurality of heat transfer tubes arranged between them,
And a gas-liquid separator ,
The inside of the heat transfer tube is a refrigerant flow path,
The lower end of the heat transfer tube is disposed inside the inlet header,
Wherein the heat transfer tube in the interior of the inlet header, have a inside through hole gas refrigerant is provided so as to flow into the heat transfer tube,
The inlet header has a liquid reservoir and a gas reservoir,
A partition is provided between the liquid reservoir and the gas reservoir,
The lower end of the heat transfer tube is disposed inside the liquid reservoir,
The through hole is provided inside the gas reservoir,
The heat exchanger, wherein the inlet header is formed of a material having a lower thermal conductivity than the heat transfer tube, or is covered with a heat insulating material . A heat exchanger according to claim 1 Symbol placement,
A heat exchanger, wherein the inner diameter of the heat transfer tube is 1.0 mm or less. The heat exchanger according to claim 1 or 2 ,
A heat exchanger, wherein a protrusion is provided at the bottom of the inlet header.

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