JP7614958B2 - Heat exchanger and method for manufacturing the same - Google Patents

Description

This disclosure relates to a heat exchanger and a method for manufacturing a heat exchanger.

Heat exchangers are used in food storage facilities, food processing plants, etc., and as a result may be used in an environment containing corrosive gases such as ammonia, formic acid, and hydrogen sulfide that are generated from the food. When used in such an environment, the heat exchanger may corrode. Therefore, to prevent corrosion by corrosive gases, the heat exchanger may be electrocoated with a corrosion-resistant paint.

For example, Patent Document 1 discloses that in a heat exchanger including multiple heat transfer tubes, multiple fins attached to the heat transfer tubes, and a holding member that holds the multiple heat transfer tubes, the heat transfer tubes, fins, and holding member are electrocoated. In the heat exchanger described in Patent Document 1, the entire heat exchanger is immersed in a corrosion-resistant paint and an electric current is passed through the entire heat exchanger, so that the heat transfer tubes, fins, and holding member included in the heat exchanger are electrocoated.

JP 2018-84374 A

In the heat exchanger described in Patent Document 1, each fin is formed in a plate shape, and the plate is large enough to cross all of the heat transfer tubes that extend in the same direction. The fins are arranged in the extension direction of the heat transfer tubes, with the plate surface facing the extension direction of the heat transfer tubes. As a result, the fins overlap in the extension direction of the heat transfer tubes. This can make it more difficult for current to flow through the center of the plate surfaces of the overlapping fins during electrocoating than through the outer periphery of the plate surfaces. In that case, the current density decreases.

When this type of decrease in current density occurs during electrocoating, it becomes difficult for the coating to deposit in the center of the fin's plate surface where the decrease in current density occurs. As a result, there is a large difference in the deposition speed of the coating within the same fin. This reduces the uniformity of the coating thickness.

This disclosure has been made to solve the above problems, and aims to provide a heat exchanger and a method for manufacturing a heat exchanger that can make the thickness of the coating film formed by electrocoating more uniform.

In order to achieve the above object, the heat exchanger according to the present disclosure includes a plurality of heat transfer tubes, a plurality of fins, and a holding member . The plurality of heat transfer tubes are electrically conductive. The plurality of fins each have a plate surface facing the direction in which the tube axis of the heat transfer tube extends, and each have a plurality of electrically conductive plate-shaped parts arranged in a direction intersecting the tube axis with a gap between them , and are attached to the heat transfer tube and arranged in the direction in which the tube axis extends . The holding member has a hanging hole, is electrically conductive, and holds the plurality of heat transfer tubes to connect the plurality of heat transfer tubes to each other and to make them conductive. Furthermore, each of the plurality of fins is formed in a cylindrical shape protruding from each of the plate-shaped parts, and has a fin collar that determines the interval between the fins in the extension direction of the tube axis by abutting the tip of the tube against the fin adjacent to the extension direction of the tube axis, and the gap is larger than the interval between the plurality of fins.

According to the configuration of the present disclosure, the multiple fins have their plate surfaces facing the direction in which the tube axis of the heat transfer tube extends, and each has multiple conductive plate-shaped parts arranged in a direction intersecting the tube axis with gaps between them. Therefore, compared to a fin in which multiple plate-shaped parts are integrated and have a plate surface the same size as the combined size of the multiple plate-shaped parts, current flows more easily during electrocoating, and the current density is higher. As a result, there is less difference in the deposition rate of the coating film within the fin during electrocoating. In addition, the thickness of the coating film formed during electrocoating can be made more uniform.

FIG. 1 is a front view of a heat exchanger according to a first embodiment of the present disclosure; FIG. 1 is a right side view of a tube sheet included in a heat exchanger according to a first embodiment of the present disclosure. FIG. 1 is an enlarged view of a portion of a fin included in a heat exchanger according to a first embodiment of the present disclosure. 4 is a cross-sectional view taken along line IV-IV shown in FIG. Flowchart of a method for manufacturing a heat exchanger according to the first embodiment of the present disclosure 1 is a conceptual diagram of an electrodeposition coating process included in a method for manufacturing a heat exchanger according to a first embodiment of the present disclosure. FIG. 1 is a top view of an electrodeposition tank used in an electrodeposition coating process provided in a method for manufacturing a heat exchanger according to a first embodiment of the present disclosure. A schematic diagram of an integral fin without a plate-like portion and no gaps when electrocoated, showing the direction of the current. Conceptual diagram of an integrated fin showing the thickness of the electrocoat coating on each part A conceptual diagram of a fin showing the direction of current flowing in an electrodeposition coating process included in the method for manufacturing a heat exchanger according to the first embodiment of the present disclosure. A conceptual diagram of a fin showing the thickness of a coating film at each part when the heat exchanger according to the first embodiment of the present disclosure is electrocoated by an electrocoating process. FIG. 13 is a right side view of a modification of the fins included in the heat exchanger according to the first embodiment of the present disclosure. FIG. 11 is a front view of a heat exchanger according to a second embodiment of the present disclosure. 12 is a cross-sectional view taken along the line XII-XII in FIG. FIG. 13 is a right side view of a modification of the fins included in the heat exchanger according to the second embodiment of the present disclosure.

Hereinafter, a heat exchanger and a manufacturing method for a heat exchanger according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or equivalent parts are given the same reference numerals. In addition, in the orthogonal coordinate system XYZ shown in the drawings, the direction in which the axis of each heat transfer tube extends is the left-right direction, and the direction in which the header to which the heat transfer tube is connected extends is the up-down direction. The left-right direction is the X-axis, the up-down direction is the Z-axis, and the direction perpendicular to the X-axis and Z-axis is the Y-axis. In the following explanation, this coordinate system will be referred to as appropriate.

(Embodiment 1)
The heat exchanger according to the first embodiment has a plurality of plate-shaped fins with gaps between each of them to enable the formation of a uniform coating film when performing electrocoating. First, the overall configuration of the heat exchanger will be described with reference to Figs. 1 to 4.

Figure 1 is a front view of a heat exchanger 1A according to the first embodiment. Figure 2 is a right side view of a tube sheet 10 included in the heat exchanger 1A. Figure 3 is an enlarged view of a portion of a fin 40A included in the heat exchanger 1A. Note that Figures 1 and 2 show a conceptual heat exchanger 1A with details omitted for ease of understanding. Also, in Figure 2, the tubes connecting the flow divider 50 and the header 60 to the heat transfer tube 30 are shown by two-dot chain lines.

As shown in FIG. 1, the heat exchanger 1A is a so-called fin-and-tube type heat exchanger. In detail, the heat exchanger 1A includes tube sheets 10 and 20, a plurality of heat transfer tubes 30 that are held by the tube sheets 10 and 20 and through which a refrigerant flows, and a plurality of fins 40A attached to the plurality of heat transfer tubes 30.

The tube sheets 10 and 20 are provided to reinforce the heat exchanger 1A. In detail, the tube sheets 10 and 20 are formed of a highly rigid metal material to obtain strength. The tube sheet 10 is formed in a plate shape as shown in Figs. 1 and 2. Its shape in side view is the same rectangular shape as the side portion of the heat exchanger 1A in order to reinforce the side portion of the heat exchanger 1A. Although not shown, the tube sheet 20 is also formed in a plate shape of the same size and shape as the tube sheet 10.

On the other hand, as shown in FIG. 2, a pair of hanging holes 11 are formed at the upper end of the tube sheet 10 so that the heat exchanger 1A can be suspended and transported during electrocoating. These hanging holes 11 are circular through-holes that penetrate the tube sheet 10 to facilitate hanging. Although not shown, a similar pair of hanging holes is also formed at the upper end of the tube sheet 20.

In addition, in order to hold the heat transfer tubes 30 arranged in the front-rear and up-down directions, the tube sheet 10 has a plurality of through holes 12 arranged in a matrix in the front-rear and up-down directions as shown in FIG. 2, and having an inner diameter that allows the heat transfer tubes 30 to be inserted. As shown in FIG. 1, the heat transfer tubes 30 are bent into a hairpin shape, and two straight tube portions 32 of the heat transfer tubes 30 shown in FIG. 3, sandwiching a hairpin portion 31 bent into a hairpin shape, are inserted into each of the through holes 12. Therefore, the number of through holes 12 is half the number of the heat transfer tubes 30. The tube sheet 20 also has the same number, arrangement, and size of through holes 22 as shown in FIG. 3.

As shown in FIG. 1, the tube sheets 10 and 20 are arranged apart from each other with the plate surfaces facing the left and right directions. In this state, although not shown in FIG. 1, the above-mentioned straight tube portions 32 of the heat transfer tubes 30 are passed through the through holes 12 of the tube sheet 10 and the through holes 22 of the tube sheet 20. Although not shown, the heat transfer tubes 30 are expanded on the inner walls of the through holes 12 of the tube sheet 10 and the through holes 22 of the tube sheet 20, and as a result, the heat transfer tubes 30 are in close contact with the inner walls. As a result, the heat transfer tubes 30 are fixed to the tube sheets 10 and 20. The tube sheets 10 and 20 hold the right and left ends of the heat transfer tubes 30. As a result, the tube sheets 10 and 20 reinforce the heat exchanger 1A.

The heat transfer tube 30 is made of a metal material with high thermal conductivity, such as pure copper, copper alloy, pure aluminum, or aluminum alloy, so that the heat of the refrigerant can be easily transferred. Although not shown, the heat transfer tube 30 is formed in a circular tube shape, and a space for flowing the refrigerant is formed inside. The circular tube of the heat transfer tube 30 is bent in a hairpin shape as described above. By bending the heat transfer tube 30 in a hairpin shape, the two straight tube portions 32 described above extend parallel to each other. The heat transfer tube 30 is attached to the through hole 12 of the tube plate 10 and the through hole 22 of the tube plate 20 described above, so that the straight tube portions 32 are oriented in the left-right direction as shown in FIG. 3. Also, as shown in FIG. 1, the hairpin portion 31 described above is oriented to the left, and the end of the straight tube portion 32 is oriented to the right.

In some of the heat transfer tubes 30, the right ends of the straight tube sections 32 are inserted into the through holes 12 at the front and rear ends of the tube sheet 10. The right ends of the straight tube sections 32 of these heat transfer tubes 30 are connected to the flow divider 50 and header 60 shown in FIG. 2.

The diverter 50 is connected to an external device that supplies refrigerant when the heat exchanger 1A is in use, and divides the refrigerant supplied from the external device. In contrast, the header 60 is connected to multiple heat transfer tubes 30 when the heat exchanger 1A is in use, and collects the refrigerant flowing from those heat transfer tubes 30.

In some of the heat transfer tubes 30 described above, the right end of the straight pipe section 32 is connected to the above-mentioned flow diverter 50 by a connecting pipe, adapter, etc., so that the refrigerant is supplied from an external device connected to the flow diverter 50. Alternatively, the right end of the straight pipe section 32 is connected to a header 60 by a connecting pipe, adapter, etc., so that the refrigerant is discharged to an external device connected to the header 60.

As shown in FIG. 2, the ends of the straight pipe sections 32 of the heat transfer tubes 30 are connected to each other by U-bend pipes 33, which are pipe joints. This allows the supplied refrigerant to flow between the heat transfer tubes 30. The heat of the refrigerant is then transferred to the heat transfer tubes 30. To dissipate the transferred heat, multiple fins 40A shown in FIG. 1 are attached to the heat transfer tubes 30.

The U-bend tube 33 is made of metal and has electrical conductivity. As a result, the U-bend tube 33 provides electrical conductivity between the heat transfer tubes 30 made of metal materials.

Each of the fins 40A is made of a metal material with high thermal conductivity, such as pure copper, copper alloy, pure aluminum, or aluminum alloy, just like the heat transfer tubes 30, in order to dissipate heat from the heat transfer tubes 30 with high efficiency. The fins 40A are formed in the shape of a flat plate. In addition, each of the fins 40A has multiple fin collars 41 formed thereon, as shown in FIG. 3, in order to attach the fins to multiple heat transfer tubes 30.

Each fin collar 41 is formed in the shape of a tube protruding to the left from the flat plate of the fin 40A. The inner diameter of the fin collar 41 is a diameter that allows it to fit tightly against the outer periphery of the heat transfer tube 30. The same number of fin collars 41 are formed as the total number of straight tube sections 32 of all the heat transfer tubes 30. Furthermore, as shown in FIG. 3, the straight tube sections 32 of the heat transfer tubes 30 are passed through the fin collars 41. The fin collars 41 are fixed to the heat transfer tubes 30 by expanding the straight tube sections 32 of the heat transfer tubes 30 that have been passed through and fitting tightly against the fin collars 41. In this way, the fins 40A are attached to the heat transfer tubes 30.

Furthermore, a large number of fins 40A are provided to dissipate heat transferred to the heat transfer tube 30 with high efficiency. In detail, a large number of fins 40A are arranged in the left-right direction with the plate surfaces facing left-right. The left-right distance S between the fins 40A is determined by the left tip of the fin collar 41 touching the adjacent fin 40A on the left. The distance S is sufficiently small compared to the size of the plate surface of the fin 40A, which is not shown in FIG. 3.

The heat exchanger 1A equipped with such heat transfer tubes 30 and fins 40A is incorporated into an air conditioning system used in an atmosphere containing corrosive gas, which may result in the heat exchanger 1A becoming corroded. For this reason, it is desirable to cover the tube sheets 10, 20, heat transfer tubes 30, and fins 40A of the heat exchanger 1A with a corrosion-resistant coating to prevent corrosion by the corrosive gas. Therefore, in the heat exchanger 1A, the heat transfer tubes 30 and fins 40A are electrocoated with a corrosion-resistant paint.

In the following, corrosion-resistant coatings will simply be referred to as coatings. Also, corrosion-resistant paints will simply be referred to as paints, or, since they are electrocoating paints, they will be referred to as electrocoating paints.

However, as described above, the fins 40A are arranged at narrow intervals compared to the size of the plate surface of the fin 40A. For example, the area of the plate surface of the fin 40A is 0.2 ^m2 , while the interval between the fins 40A is about 2 to 4 mm. In electrocoating, as described below, a voltage is applied between the heat exchanger 1A and a counter electrode arranged around the heat exchanger 1A while the heat exchanger 1A is immersed in a paint solution. Since the interval between the fins 40A is smaller than the width and length of the plate surface of the fin 40A, the resistance of the solution from the counter electrode to the center of the fin 40A becomes larger than the resistance of the solution from the counter electrode to the outer periphery of the fin 40A. If the difference in resistance is too large, the progress of the coating film formation at the center of the fin 40A during electrocoating becomes slower than the progress of the coating film formation at the outer periphery. In electrocoating, as the coating film formation progresses, the coating film itself has an increased electrical resistance, making it difficult to form the coating film, and as a result, the coating film tends to have a uniform thickness. However, if there is such a difference in resistance, the coating film thickness will not be uniform, and for example, the coating film in the center of the fin 40A will become thinner. This will impair the uniformity of the coating film thickness within the same fin 40A.

Therefore, in the heat exchanger 1A, in order to increase the uniformity of the thickness of the coating, the fins 40A are formed of multiple plate-shaped parts with gaps between them. Next, the configuration of the fins 40A will be described with reference to Figure 4.

Figure 4 is a cross-sectional view taken along the line IV-IV shown in Figure 1. Note that, as a result of showing a cross-section taken along the line IV-IV, Figure 4 shows the fin 40A as seen from the right side. To facilitate understanding, the outline of the integral fin 400 that does not include multiple plate-shaped portions 421-423 is shown by a dotted line.

As shown in FIG. 4, the fin 40A has multiple plate-shaped portions 421-423 formed in a flat plate shape.

The plate surface of each of the plate-shaped portions 421-423 is perpendicular to the tube axis of the heat transfer tube 30 to facilitate air flow between the fins 40A when the heat exchanger 1A is in use. In other words, the plate surface of each of the plate-shaped portions 421-423 faces in the left-right direction, i.e., the X direction. The plate-shaped portions 421-423 are aligned in the X direction. This increases the heat dissipation area for air flowing in the same X position.

On the other hand, gaps 43, 44 are provided between plate-shaped portions 421, 422 and between plate-shaped portions 422, 423 to ensure a current path for the current flowing between the counter electrodes when performing electrocoating.

In detail, each of the plate-shaped parts 421-423 is formed in a rectangular shape of the same shape and size. The longitudinal direction of each of the plate-shaped parts 421-423 faces the front-rear direction, i.e., the Y direction, and the lateral direction faces the up-down direction, i.e., the Z direction. Furthermore, although not shown in FIG. 4, the plate-shaped parts 421-423 are arranged in a line at the same position in the left-right direction, i.e., the same position in the X direction. With the plate-shaped parts 421, 422 and 422, 423 arranged in such a positional relationship, slit-shaped, i.e., narrow gaps 43, 44 are provided between the plate-shaped parts 421, 422 and between the plate-shaped parts 422, 423, having a width W in the Z direction and extending in the Y direction.

The gaps 43 and 44 are gaps for dividing a single rectangular integral fin 400 with its short side oriented in the Y direction and its long side oriented in the Z direction, i.e., an integral fin 400 with plate-like portions 421-423 integrated into one piece, into three plate-like portions 421-423. In other words, the gaps 43 and 44 are gaps for dividing the integral fin 400 into a number of smaller plate-like portions 421-423.

The reason for providing such gaps 43, 44 is that the gaps 43, 44 allow the paint solution to enter these gaps 43, 44 during electrocoating, and as a result, a current path in the paint from the counter electrode to the plate-like parts 421-423 can be secured when a voltage is applied between the counter electrode of the electrocoating and the heat exchanger 1A. This reduces the difference between the maximum and minimum resistances of the solution from the counter electrode to each part in the plate-like parts 421-423 compared to an integrated fin 400 in which the narrow gaps 43, 44 are not formed. In addition, with this arrangement, by being provided between the plate-like parts 421-423 arranged in a row, the gaps 43, 44 are less likely to disturb the flow of air flowing between the fins 40A when the heat exchanger 1A is in use.

The width W of the gaps 43, 44 in the Z direction is larger than the left-right distance S between the fins 40A shown in FIG. 3 in order to ensure a current path in the paint during electrocoating. By forming the gaps 43, 44 in this shape, the uniformity of the thickness of the coating film formed by electrocoating on each of the plate-like portions 421-423 is increased. In addition, the coating film formation on each of the plate-like portions 421-423 proceeds simultaneously, shortening the time until the coating film formation is completed.

It is desirable that the width W of the gaps 43, 44 be narrower than the short-side length of the plate-shaped portions 421-423 shown in FIG. 4. If the width W is too large, the heat dissipation performance of the fins 40A will decrease.

In addition, in order to minimize the difference in resistance of the above-mentioned solution from the counter electrode to each part in the plate-like parts 421-423, it is desirable to form the gaps 43, 44 at positions that divide the integral fin 400 into plate-like parts 421-423 with shapes that are as equal in length as possible in the Y direction and Z direction. For example, it is desirable to form the gaps 43, 44 at positions that divide the integral fin 400 into plate-like parts 421-423 with shapes that are close to square.

Next, a method for manufacturing the heat exchanger 1A will be described with reference to Figures 5-7, 8A, 8B, 9A, and 9B. In the following explanation, the heat exchanger 1A is subjected to electrocoating, so the electrocoating method will also be described.

Figure 5 is a flow chart of the manufacturing method of the heat exchanger 1A according to the first embodiment. Figure 6 is a conceptual diagram of the electrocoating process included in the manufacturing method of the heat exchanger 1A. Figure 7 is a top view of the electrocoating tank 72 used in the electrocoating process.

First, the tube sheets 10, 20, heat transfer tubes 30, U-bend tubes 33, and plate-like portions 421-423 of the fins 40A are fabricated and prepared in the shapes, sizes, and quantities described above. For example, the heat transfer tubes 30 are fabricated by cutting a circular tube made of a metal material with high thermal conductivity to the desired length and then bending it into a hairpin shape. In this way, the heat transfer tubes 30 are prepared. In addition, the plate-like portions 421-423 of the fins 40A, which are equipped with the fin collars 41, are fabricated by pressing a metal sheet made of a metal material with high thermal conductivity. In this way, the plate-like portions 421-423 are prepared.

Next, as shown in FIG. 5, a fin stacking process is performed to stack the fins 40A (step S1). In detail, the plate-shaped portions 421 are stacked with the surfaces of the plate-shaped portions 421 from which the fin collars 41 protrude facing the same side. At this time, the distance between the plate-shaped portions 421 is determined by abutting the tip of the fin collar 41 against the plate surface of the plate-shaped portion 421 that is to be stacked. Plate-shaped portions 422 and 423 are also stacked in the same manner. In this way, the fins 40A are stacked.

Next, a heat transfer tube attachment process is performed in which the stacked plate-like portions 421-423 are attached to the heat transfer tube 30 (step S2). In detail, the tube sheets 10 and 20 are arranged on both sides of the stacked plate-like portions 421-423, and then the straight tube portion 32 of the heat transfer tube 30 is inserted into the fin collar 41 of the plate-like portions 421-423 that overlap the through holes 12 and 22 of the tube sheets 10 and 20. In this way, the heat transfer tube 30 is attached to the plate-like portions 421-423 that are stacked with the tube sheets 10 and 20. In other words, the heat transfer tube 30 is assembled to the tube sheets 10 and 20 and the fins 40A.

After the heat transfer tube 30 is assembled, a crimping process is performed in which the straight tube portion 32 of the heat transfer tube 30 is crimped to the tube sheets 10, 20, and the fins 40A (step S3). In detail, after the heat transfer tube 30 is assembled to the tube sheets 10, 20 and the stacked fins 40A, the straight tube portion 32 of the heat transfer tube 30 is expanded. This expansion can be performed, for example, by pushing a spherical metal jig whose outer diameter is larger than the inner diameter of the heat transfer tube 30 by the expansion dimension into the inside of the heat transfer tube 30. Alternatively, it can be performed by introducing a high-pressure liquid into the inside of the heat transfer tube 30. By expanding the straight tube portion 32, the tube wall portion of the straight tube portion 32 of the heat transfer tube 30 is crimped to the tube sheets 10, 20, and the fins 40A. As a result, the heat transfer tube 30 is fixed to the tube sheets 10, 20, and the fins 40A.

Next, although not shown, a U-bent tube 33 is connected to the end of the straight tube section 32 of the heat transfer tube 30 fixed to the tube sheets 10, 20, and fins 40A. For example, the U-bent tube 33 is brazed to the heat transfer tube 30. This connects multiple heat transfer tubes 30 to create a refrigerant path through which the refrigerant flows. Furthermore, a flow divider 50 and a header 60 are connected to the end of the straight tube section 32 of some of the heat transfer tubes 30 using connecting tubes, adapters, etc. This makes it possible to supply and discharge the refrigerant to the above-mentioned refrigerant path. As a result, a heat exchanger 1A is created in a state in which the refrigerant can flow.

The heat exchanger 1A in this state still has a heat exchange function, but in this embodiment, to improve corrosion resistance, electrocoating is applied to the heat exchanger 1A. Next, when the heat exchanger 1A in a state in which the above-mentioned refrigerant can flow is produced, an electrocoating process is performed in which the heat exchanger 1A is electrocoated (step S4).

In detail, first, the heat exchanger 1A is immersed in an electrodeposition tank 72 filled with electrodeposition paint 71, as shown in FIG. 6.

For this immersion, a number of counter electrodes 74 are arranged in advance along the inner circumference of the electrodeposition tank 72 near the inner wall of the electrodeposition tank 72. In addition, an amount of electrodeposition paint 71 sufficient to immerse the counter electrodes 74 and the entire heat exchanger 1A is placed in the electrodeposition tank 72 in advance.

The electrodeposition paint 71 is a cationic electrodeposition paint, which is a corrosion-resistant paint. For example, the electrodeposition paint 71 is a cationic electrodeposition paint that contains a base resin, a hardener, a pigment, and additives as non-volatile components, and a solvent, a neutralizer, and water as volatile components. It is preferable that the base resin is made water-soluble by a neutralizer. It is also preferable that the base resin contains an epoxy resin, the neutralizer contains acetic acid, and the pigment contains carbon black.

After setting the electrodeposition tank 72 in the above-mentioned state, as shown in FIG. 7, a hanging tool 73 made of a conductive material is passed through the hanging hole 11 of the tube sheet 10 shown in FIG. 2 to hang the heat exchanger 1A. The hung heat exchanger 1A is then transported and placed in the center of the electrodeposition tank 72. This causes the heat exchanger 1A to be immersed in the electrodeposition paint 71, and the heat exchanger 1A is surrounded by the counter electrode 74.

When the heat exchanger 1A is immersed, the hanging tool 73 and the counter electrode 74 shown in FIG. 6 are electrically connected to the cathode and anode of the DC power source 75, and a DC voltage is applied between the hanging tool 73 and the counter electrode 74. The hanging tool 73 is made of a conductive material, and the tube sheets 10 and 20, which have the hanging hole 11 through which the hanging tool 73 passes, are also made of a metal material, and are therefore conductive. The heat transfer tube 30, the U-bent tube 33, and the fins 40A are also made of a metal material and are conductive. Therefore, when a DC voltage is applied to the hanging tool 73 and the counter electrode 74, a DC current flows through the electrocoating paint 71 between the counter electrode 74 and the heat exchanger 1A. Then, a coating is deposited on each part of the heat exchanger 1A.

The deposition speed of the coating depends on the current density flowing from the electrocoating paint 71 to each part of the heat exchanger 1A. The coating is deposited from the parts of the heat exchanger 1A where current flows easily. The current flow at that time and the thickness of the coating after a certain time has passed are shown in Figures 8A, 8B, 9A, and 9B.

Figure 8A is a conceptual diagram of an integrated fin 400 that does not have plate-shaped portions 421-423 and does not have gaps 43, 44, showing the direction of current when the integrated fin 400 is electrocoated. Figure 8B is a conceptual diagram of an integrated fin 400 showing the thickness of the coating film at each part by electrocoating. Also, Figure 9A is a conceptual diagram of a fin 40A showing the direction of current flowing in the electrocoating process included in the manufacturing method of heat exchanger 1A. Figure 9B is a conceptual diagram of a fin 40A showing the thickness of the coating film at each part when heat exchanger 1A is electrocoated by the electrocoating process.

Note that Figures 8A, 8B, 9A, and 9B show the fins 400 and 40A as viewed from the right side, but for ease of understanding, the fin collar 41, heat transfer tube 30, and other components or parts are omitted. Also, in Figures 8A and 9A, arrow A indicates the direction of current only in a portion of the fins 400, 40A where the current density is high. In Figures 8B and 9B, the thickness of the coating is indicated by shading, with the darker areas indicating a thicker coating.

As shown by arrow A in FIG. 8A, in an integrated fin 400 that does not have plate-shaped portions 421-423 and does not have gaps 43, 44, current flows from the outer periphery of the fin 400 toward the inside when electrocoating begins. This is because the fins 400 are stacked at intervals S that are relatively small compared to the size of the plate surface, and as a result, the closer to the outer periphery of the fin 400 the current flows more easily and the current density tends to increase. In addition, the fin 400 is electrically connected to the hanging device 73 connected to the DC power source 75 via the heat transfer tube 30 or fin collar 41 on the inside of the plate surface.

As a result, as shown in FIG. 8B, when the fin 400 is electrocoated, the thickness of the coating is greater on the outer periphery and becomes thinner toward the inside. Furthermore, because the plate surface of the fin 400 is large, a relatively large area of thin coating thickness is distributed in the center of the fin 400.

In contrast, in the fin 40A of the heat exchanger 1A, as shown by arrow A in FIG. 9A, when electrocoating begins, in addition to the current flowing inward from the upper end of the plate-shaped portion 421, which corresponds to the outer periphery of the fin 40A, the right and left ends of -423 of the plate-shaped portion 421, and the lower end of the plate-shaped portion 423, current also flows inward from the lower end of the plate-shaped portion 421, the upper end and lower end of the plate-shaped portion 422, and the upper end of the plate-shaped portion 423, which face the gaps 43 and 44. This is because the gaps 43 and 44 provided between the plate-shaped portions 421 and 423 are larger than the spacing S between the layers of the fin 40A, and therefore current flows more easily in the portions facing the gaps 43 and 44.

As a result, a coating film is more easily deposited on the fin 40A than on the fin 400. This allows the coating film to deposit at a faster rate. As a result, a coating film of sufficient thickness can be formed in a short time. Also, since the coating film is deposited on the plate-shaped portions 421-423, which have smaller plate surfaces than the fin 400, starting from their outer periphery, as shown in FIG. 9B, the coating film thickness of the fin 40A after electrocoating is completed is less variable than that of the fin 400. In short, the throwing power of the electrocoating is improved.

Returning to FIG. 5, in the electrocoating process of step S4, DC current is passed through the heat exchanger 1A for a certain period of time, and then the supply of DC current is stopped. This causes a coating film of the above-mentioned thickness to be formed on each part of the heat exchanger 1A, such as the fins 40A, the tube sheets 10 and 20, and the heat transfer tube 30.

When the supply of direct current is stopped, the heat exchanger 1A is removed from the electrochemical deposition tank 72 by lifting the hanging tool 73. The removed heat exchanger 1A is then dried. If necessary, it is washed with water and baked. This completes the painted heat exchanger 1A.

The tube sheets 10 and 20 described in the first embodiment are an example of a holding member for holding the heat transfer tube 30 as defined in this specification. The gaps 43 and 44 are an example of a slit whose width direction is the arrangement direction of the multiple plate-like portions 421-423 as defined in this specification. A coating film formed by electrocoating is also called an electrocoating film, and a coating film formed by a cationic electrocoating paint is an example of an electrocoating film as defined in this specification. Furthermore, the stacking direction of the fins 40A is also the direction in which the tube axis of the heat transfer tube 30 extends, and is therefore also called the extension direction of the tube axis.

As described above, in the heat exchanger 1A according to the first embodiment, each of the fins 40A has a plate surface extending in a direction perpendicular to the tube axis of the heat transfer tube 30, and has plate-shaped parts 421-423 attached to the heat transfer tube in a state of being arranged in a direction perpendicular to the tube axis of the heat transfer tube 30, and gaps 43, 44 are provided between the plate-shaped parts 421-423. Therefore, compared to the fin 400 in which the plate-shaped parts 421-423 are integrated and have a plate surface of the same size as the combined size of the plate-shaped parts 421-423, current flows more easily to the fin 40A during electrocoating, and the current density of the fin 40A is high. As a result, in the heat exchanger 1A, the difference in the deposition rate of the coating film in the fin 40A during electrocoating can be reduced. In addition, the thickness of the coating film formed can be made more uniform.

The gaps 43, 44 between the plate-like portions 421-423 are larger than the spacing S between the stacked fins 40A. As a result, current flows easily through the fins 40A during electrocoating, and the current density of the fins 40A is high. This makes it easier for a coating film to deposit on the fins 40A during electrocoating. As a result, the throwing power of the electrocoating is high. In addition, the thickness of the coating film formed can be made more uniform.

(Modification)
In the first embodiment, the fins 40A are elongated in the vertical direction, but the shape of the fins 40A is not limited to this.

Figure 10 is a right side view of a modified example of the fin 40A provided in the heat exchanger 1A according to embodiment 1.

As shown in FIG. 10, the fin 40A may be elongated in the front-to-rear direction, i.e., in the Y direction. On the other hand, the gaps 43, 44 may be shaped to cross the longitudinal direction of the plate surface of the fin 40A. In the case of the fin 40A shown in FIG. 10, since the Y direction is the longitudinal direction, the gaps 43, 44 may extend in the short direction of the fin 40A, i.e., in the Z direction.

In this way, the overall shape of the plate surface of the fin 40A is arbitrary. Furthermore, when the fin 40A has a shape having a longitudinal direction and a lateral direction, for example, a rectangular, elliptical, or oval shape, the gaps 43 and 44 may have a shape that crosses the longitudinal direction of the plate surface of the fin 40A.

(Embodiment 2)
In the first embodiment, the plate-shaped portions 421-423 of the fin 40A are completely separated by the gaps 43, 44. However, the fin 40A is not limited to this. The plate-shaped portions 421-423 of the fin 40A may be connected to each other. For example, the plate-shaped portions 421-423 may be connected to each other by being partially separated by the gaps 43, 44.

In the heat exchanger 1B according to the second embodiment, the plate-shaped portions 421-423 have slits 45, 46 that partially separate them from each other. Below, the configuration of the fins 40B provided in the heat exchanger 1B will be described with reference to Figures 11 and 12. In the second embodiment, the configuration that differs from the first embodiment will be mainly described.

Figure 11 is a front view of a heat exchanger 1B according to embodiment 2. Figure 12 is a cross-sectional view taken along the line XII-XII shown in Figure 11.

As shown in FIG. 11, heat exchanger 1B has multiple fins 40B arranged in the left-right direction, similar to heat exchanger 1A.

As shown in FIG. 12, the fin 40B is in the shape of a rectangular plate with its longitudinal direction facing up and down. Although not shown, on the left side, i.e., on the plate surface on the -X side, multiple cylindrical fin collars 41 described in embodiment 1 are provided with the same shape, size, and arrangement as the fin 40A. The heat transfer tubes 30 are passed through these fin collars 41.

On the other hand, as shown in FIG. 12, fin 40B has slits 45 and 46 that divide the plate surface into thirds in the longitudinal direction. More specifically, slit 45 is provided at a position 1/3 of the length of the longitudinal side of fin 40B from the top end of fin 40B. Slit 46 is provided at a position 2/3 of the length of the longitudinal side of fin 40B from the top end of fin 40B.

The slits 45, 46 have a width W in the up-down direction, i.e., in the Z direction, that is the same as the width of the gaps 43, 44 described in embodiment 1. The slits 45, 46 then extend in the front-to-back direction, i.e., in the Y direction, while maintaining that width. As a result, the slits 45, 46 divide the fin 40B into plate-shaped portions 421-423. As a result, the slits 45, 46, like the gaps 43, 44 described in embodiment 1, facilitate the flow of current during electrocoating, increasing the current density. As a result, the slits 45, 46 facilitate the deposition of a coating on the fin 40B during electrocoating.

The length L1 of the slits 45 and 46 in the Y direction is shorter than the length L2 of the fin 40B in the longitudinal direction. As a result, the slits 45 and 46 separate most of the center of the fin 40B in the Y direction, but do not separate the +Y end and -Y end of the fin 40B. In other words, the slits 45 and 46 do not completely divide the fin 40B into the plate-shaped portions 421-423, but leave the plate-shaped portions 421-423 adjacent in the Z direction across the slits 45 and 46 partially connected. This makes it unnecessary to stack the plate-shaped portions 421-423 separately when manufacturing the heat exchanger 1B, and the plate-shaped portions 421-423 can be stacked together. As a result, the heat exchanger 1B is easier to assemble than the heat exchanger 1A.

The length L1 of the slits 45, 46 in the Y direction is preferably at least 1/2 the length L2 of the fin 40B in the longitudinal direction. This is because such a length allows current to flow more easily during electrocoating than a single fin 400 without the slits 45, 46, and increases the current density. Furthermore, as in the first embodiment, the slits 45, 46 are preferably provided at positions that divide the integrated fin 400 in the longitudinal direction in order to minimize the difference in the resistance of the above-mentioned solution from the counter electrode to each part in the plate-shaped parts 421-423. In this case, it is preferable that the longitudinal length and the lateral length of the plate-shaped parts 421-423 formed by the slits 45, 46 are as equal as possible. For example, the plate-shaped parts 421-423 are preferably formed in a square shape by the slits 45, 46.

The manufacturing method of the heat exchanger 1B equipped with such fins 40B is the same as the manufacturing method of the heat exchanger 1A described in the first embodiment, including the electrocoating process, except that the fins 40B in which the plate-shaped portions 421-423 are connected to each other are stacked in the fin stacking process. For this reason, a detailed description of the manufacturing method of the heat exchanger 1B is omitted.

As described above, in the heat exchanger 1B according to the second embodiment, each of the fins 40B has slits 45, 46 that divide the fins 40B into a number of plate-shaped portions 421-423. During electrocoating, the electrocoating paint 71 enters the slits 45, 46, making it easier for the electrocoating current to flow and resulting in a high current density. As a result, as with the heat exchanger 1A, the difference in deposition speed of the coating film within the fins 40B during electrocoating can be reduced, and the thickness of the coating film formed can be made more uniform.

In fin 40B, the plate-shaped portions 421-423 are partially connected. This makes assembly easier than with fin 40A described in embodiment 1.

(Modification)
In addition, in embodiment 2, slits 45 and 46 separate only a large portion of the center of the short side of fin 40B and leave both ends of fin 40B connected in the short side direction, but the portions of fin 40B that are not separated and remain connected by slits 45 and 46 are not limited to this.

Figure 13 is a right side view of a modified example of the fin 40B provided in the heat exchanger 1B according to embodiment 2.

As shown in FIG. 13, instead of the slits 45 shown in FIG. 12, the fin 40B may have slits 451 extending from the +Y end of the fin 40B toward a central portion 453 in the center in the Y direction, and slits 452 extending from the -Y end of the fin 40B toward the central portion 453. The slits 451, 452 may divide the fin 40B into plate-shaped portions 421 and 422. In this case, the plate-shaped portions 421 and 422 may be connected to each other by the central portion 453.

Similarly, as shown in FIG. 13, fin 40B may have, instead of slit 46 shown in FIG. 12, slit 461 extending from the +Y end of fin 40B toward central portion 463 at the center in the Y direction, and slit 462 extending from the -Y end of fin 40B toward central portion 463. Fin 40B may be divided into plate-shaped portions 422 and 423 by these slits 461, 462. In this case, plate-shaped portions 422 and 423 may also be connected to each other by central portion 463.

In this way, the fin 40B may be divided into an incomplete state with some parts still connected by multiple slits 451, 452, 461, and 462.

The slits 45, 46, 451, 452, 461, and 462 described in the second embodiment are an example of a slit whose width direction is the arrangement direction of the multiple plate-like portions 421-423, as defined in this specification. The front and rear ends of the slits 45 and 46 described in the second embodiment, which are not separated, i.e., the +Y end and the -Y end, are an example of a connecting portion that connects the plate-like portions 421-423 to each other, as defined in this specification. The center portions 453 and 463 of the modified example are also an example of a connecting portion that connects the plate-like portions 421-423 to each other.

The above describes the heat exchangers 1A, 1B and the manufacturing method for the heat exchangers 1A, 1B according to the embodiment of the present disclosure, but the heat exchangers 1A, 1B and the manufacturing method for the heat exchangers 1A, 1B are not limited to this.

For example, in the first and second embodiments, the heat transfer tubes 30 are cylindrical and hairpin shaped, but the shape of the heat transfer tubes 30 is not limited to these. There may be multiple heat transfer tubes 30, and the heat transfer tubes 30 may be any shape as long as they are conductive. To this extent, the shape of the heat transfer tubes 30 is arbitrary.

For example, the heat transfer tubes 30 may be flat tubular with a flat cross section. The heat transfer tubes 30 may also be straight. If they are straight, the heat transfer tubes 30 may be connected to each other by pipe joints.

In the first and second embodiments, the heat transfer tubes 30 are held by the tube sheets 10 and 20. However, the heat exchangers 1A and 1B are not limited to this. In the heat exchangers 1A and 1B, the tube sheets 10 and 20 may be of any configuration, and the tube sheets 10 and 20 may not be provided. Even in such a configuration, electrodeposition coating is possible by passing a direct current for electrodeposition coating through the heat transfer tubes 30 or the fins 40A and 40B, respectively. In addition, the gaps 43 and 44 and the slits 45, 46, 451, 452, 461, and 462 described in the first and second embodiments can make the thickness of the coating film formed by electrodeposition coating more uniform.

In the first and second embodiments, the fins 40A and 40B have three plate-shaped portions 421-423. However, the fins 40A and 40B are not limited to this. The fins 40A and 40B may be provided in a plurality of pieces, and each of the fins 40A and 40B may have a plate surface facing the direction in which the tube axis of the heat transfer tube 30 extends, and may have a plurality of conductive plate-shaped portions 421-423 arranged in a direction intersecting the tube axis with gaps 43 and 44 between them, and may be attached to the heat transfer tube 30. Here, the gaps 43 and 44 may be formed by slits 45, 46, 451, 452, 461, and 462. The number of plate-shaped portions 421-423 provided on the fins 40A and 40B may be any number as long as the above conditions are met.

For example, each of the fins 40A, 40B may have two plate-shaped portions 421-423. Also, each of the fins 40A, 40B may have four or more plate-shaped portions 421-423. It is preferable that the number of plate-shaped portions 421-423 is as large as possible within the range in which the fins 40A, 40B achieve the desired heat dissipation and heat transfer performance. This is because such a configuration makes it possible to make the thickness of the coating film formed by electrocoating more uniform.

Furthermore, as described above, the fins 40A, 40B are provided in multiple numbers, and as long as the plate surface faces the direction in which the tube axis of the heat transfer tube 30 extends, and each has multiple conductive plate-shaped parts 421-423 arranged in a direction intersecting the tube axis with gaps 43, 44 between them, and is attached to the heat transfer tube 30, the shape of the fins 40A, 40B is also arbitrary.Furthermore, as long as the shape of the gaps 43, 44 in the fins 40A, 40B is also arbitrary.

For example, in the first and second embodiments, the overall shape of the fins 40A and 40B is rectangular, but the overall shape of the fins 40A and 40B may be square. Also, the overall shape of the fins 40A and 40B may be strip-shaped or rectangular.

The gaps 43, 44 may also be in the shape of an arc-shaped or curved slit. This is because such a shape makes it easier for current to flow through the fins 40A, 40B during electrocoating, making the thickness of the coating film that is formed more uniform.

In the first and second embodiments, the paint used for the electrodeposition coating is a cationic electrodeposition paint, but the paint used for the electrodeposition coating may be an anionic electrodeposition paint.

The heat exchangers 1A and 1B described in the first and second embodiments are incorporated into an air conditioner used in an atmosphere containing corrosive gas, but the heat exchangers 1A and 1B can be applied to air conditioners in general. The heat exchangers 1A and 1B may also be used as radiators.

1A, 1B heat exchanger, 10 tube plate, 11 hanging hole, 12 through hole, 20 tube plate, 22 through hole, 30 heat transfer tube, 31 hairpin section, 32 straight tube section, 33 U-bend tube, 40A, 40B fin, 41 fin collar, 43, 44 gap, 45, 46 slit, 50 shunt, 60 header, 71 electrocoating paint, 72 electrocoating tank, 73 hanging tool, 74 counter electrode, 75 DC power source, 400 fin, 421-423 plate-shaped section, 451, 452 slit, 453 center section, 461, 462 slit, 463 center section, A arrow, L1, L2 length, W width, S interval.

Claims (6)

A plurality of conductive heat transfer tubes;
a plurality of fins attached to the heat transfer tube and arranged in the direction in which the tube axis extends, each of the fins having a plate surface facing the direction in which the tube axis extends and a plurality of conductive plate-shaped parts arranged in a direction intersecting the tube axis with gaps between them;
a holding member having a hanging hole, being electrically conductive, and holding the plurality of heat transfer tubes to connect and electrically connect the plurality of heat transfer tubes to each other;
Equipped with
Each of the multiple fins is formed in a cylindrical shape protruding from each of the plate-shaped portions, and has a fin collar that determines the spacing between the fins in the extension direction of the tube axis by abutting the tip of the tube against the adjacent fin in the extension direction of the tube axis, and the gap is larger than the spacing between the multiple fins . A corrosion-resistant coating film is provided to cover the surface of the plate-shaped portion.
2. The heat exchanger of claim 1. The corrosion-resistant coating film is an electrodeposition coating film.
3. The heat exchanger of claim 2. The gap is formed by a slit provided between the plurality of plate-shaped portions and having a width direction that is the arrangement direction of the plurality of plate-shaped portions.
A heat exchanger according to any one of claims 1 to 3. The plurality of fins have connecting portions that connect the plate-shaped portions to each other.
A heat exchanger according to any one of claims 1 to 4 . Attaching a plurality of fins, each of which has a plurality of conductive plate-shaped portions, to a plurality of conductive heat transfer tubes ;
a step of attaching the fins to the heat transfer tubes, and then holding the heat transfer tubes in a holding member having a hanging hole and being conductive, thereby connecting and electrically conducting the heat transfer tubes to each other;
a step of holding the plurality of heat transfer tubes on the holding member, suspending the holding member by passing a conductive suspending tool through the suspending hole, immersing the plurality of heat transfer tubes with the plurality of fins attached and held by the holding member in an electrocoating paint for forming a corrosion-resistant coating film, and applying a voltage between a counter electrode immersed in the electrocoating paint and the suspending tool to electrocoat the heat transfer tubes and the fins;
Equipped with
The step of attaching the plurality of fins to the plurality of heat transfer tubes includes :
The plate surfaces of the plurality of plate-shaped portions are oriented in a direction in which the tube axis of the heat transfer tube extends, and the plate-shaped portions are arranged in a direction intersecting the tube axis with gaps provided between the plate-shaped portions. In this state, the plurality of plate-shaped portions provided on the fins are attached to the plurality of heat transfer tubes;
Furthermore, the fins are arranged in the direction in which the tube axis extends, and the tips of fin collars formed in a cylindrical shape protruding from each of the plate-like portions are brought into contact with the fins adjacent to each other in the direction in which the tube axis extends, thereby determining the interval between the fins in the direction in which the tube axis extends,
In the arrangement of the plurality of plate-shaped portions, the plate-shaped portions are arranged so as to be spaced apart from each other by a distance greater than the interval, thereby making the gap larger than the interval .
A method for manufacturing a heat exchanger.

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