JP2006090636A - Small-diameter heat exchanger tube unit for small-diameter multitubular heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the mutually appropriate corresponding relation between fin joint surfaces and recessed groove parts for forming heat exchanger tubes in small-diameter heat exchanger tube units of laminated structure constituting a small-diameter multitubular heat exchanger. <P>SOLUTION: In the small-diameter heat exchanger tube units 4 of laminated structure constituting the small-diameter multitubular heat exchanger 1, engaging parts 46a, 46b engaged in an coaxial direction are formed in a plurality of mutually corresponding positions of fin plates 4A, 4B to be laminated. With this constitution the mutually appropriate corresponding relation between the fin joint surfaces and recessed groove parts for forming heat exchanger tube body parts 41 when laminated can be easily realized by engaging the engaging parts 46a, 46b provided in the plurality of mutually corresponding positions (outer peripheral edge parts or the like) of the fin plates 4A, 4B to be laminated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a structure of a small-diameter heat transfer tube unit of a small-diameter multi-tube heat exchanger.

  Recently, for example, a plurality of tubes having an annular cross section with a small diameter of about 0.2 mm to 0.8 mm are provided between an inlet tank and an outlet tank that are arranged to face each other at a predetermined interval. The tube is arranged such that the pitch L between the tubes is about the tube diameter d to 2d of the tube to form a core portion through which an external fluid flows, and the plurality of tubes of the core portion are further flowed through the core portion. There has been proposed a heat exchanger that employs a small-diameter multi-tube heat transfer tube structure that is arranged in a square grid pattern in the direction and has improved contact efficiency with an external fluid (see, for example, Patent Document 1).

  Compared to fin-and-tube heat exchangers that are generally used as heat exchangers such as air conditioners, such small-diameter multi-tube heat exchangers have higher performance, Since the ventilation resistance is smaller, it is possible to function as a highly efficient heat exchanger.

  However, in the case of the configuration of such a small-diameter multi-tube heat exchanger, since the core portion is composed of an assembly of small-diameter heat transfer tubes, the heat transfer coefficient itself as a heat transfer tube heat exchanger is high, but each other Since the heat transfer area of each heat transfer tube is small, a larger number of small-diameter heat transfer tubes are required to achieve higher performance than a certain level. As a result, the structure is complicated and the assembly is complicated.

  In addition, the heat transfer tube group of the same small diameter is provided with a large number of flow paths in a grid pattern in the flow direction of the external fluid (air) to flow the internal fluid (water). Since the amount of heat exchange for each flow path varies depending on the position, drift tends to occur, and this tendency is particularly noticeable when a gas-liquid two-phase refrigerant is flowed as in an air conditioner.

  Therefore, although it is good when the cooling water which does not change a phase state like the radiator of a car shown in patent documents 1 is made into an internal fluid, the refrigerant which changes a phase state like the above-mentioned air conditioner is made into an internal fluid. In that case, it was difficult to adopt.

  Therefore, based on such circumstances, a thin fin-like fin portion is added to each tubular body portion of the above-described small-diameter heat transfer tube, and the specification conditions of each tubular body portion and the fin portion are made less prone to drift. By forming, it is possible to effectively increase the heat transfer area in addition to the heat transfer coefficient, and to provide a small-diameter multi-tube heat exchanger that can be effectively used in air conditioners and the like. It has been.

  9 to 11 show an example of the configuration of the thin multi-tube heat exchanger provided with the heat transfer fins and the small-diameter heat transfer tube unit constituting the heat exchanger.

  That is, first, a small-diameter multi-tube heat exchanger 1 shown in FIG. 9 includes an inlet header 2A and an outlet header 2B having a refrigerant distribution function arranged in parallel with each other at a predetermined interval, and the inlet header 2A and the outlet Each of the headers 2B is connected to each of the headers 2B and is composed of a heat exchange section 3 including a plurality of small-diameter heat transfer tube units 4, 4...

  The thin-diameter heat transfer tube units 4, 4... Have a tubular body portion (thin-diameter tube portion) 41 that is bent in a U shape as a whole, and has open end portions 41 c of upper end side convex portions 44 a and 44 b. 41d is connected to the openings on the bottom side of the inlet header 2A and the outlet header 2B, respectively, while the straight portions 41a and 41b of the U-shaped tubular body 41 are respectively connected to the left and right side airflows. Fin portions 42a and 42b each having a predetermined width are provided on the upstream side and the downstream side. These fin portions 42 a and 42 b are continuous with each other to form one heat transfer fin 42 with respect to the U-shaped tube portion 41.

  And the small-diameter heat transfer tube units 4, 4... Having the heat transfer fins 42 are formed with tube portions 41 (41 a, 41 b), respectively, for example, as shown in FIGS. For example, a thin and flat fin plate (bonding member) 4A (a in FIG. 10) and 4B (b in FIG. 10) having a semi-circular groove having a semicircular cross-section are mutually connected as shown in FIG. In the state of being opposed to each other, by bonding and integrating, the fin portions 42a and 42b are in a single sheet state on both the left and right sides of the U-shaped tube portion 41 and the straight portions 41a and 41b of the tube portion 41. The integrally formed thin-diameter heat transfer tube units 4, 4,...

  The small-diameter heat transfer tube units 4, 4... Configured as described above are arranged in parallel with the flow direction of the external fluid F, for example, as shown in FIG. Units 4, 4... An inlet header 2A and an outlet header 2B are connected to the open end portions 41c and 41d of the projections 44a and 44b for connection to the upper headers 2A and 2B, and a small diameter multitubular heat exchanger. 1 is formed.

  According to the configuration as described above, heat transfer fins for further expanding the heat transfer area are provided on both sides of the tube body portion 41 (41a, 41b) of a large number of small-diameter heat transfer tubes with originally high heat transfer rates. 42 (42a, 42b) is added, in addition to the good heat transfer coefficient by the tube portions 41, 41... (41a, 41b, 41a, 41b...) Of a plurality of small diameter heat transfer tubes. As a result, the heat transfer area is also greatly increased, the overall heat exchange performance is greatly improved, and it is suitable for use conditions as a heat exchanger for an air conditioner.

Japanese Patent Laid-Open No. 2001-116481 (Specification, page 1-3, FIG. 1-4)

  By the way, in the case of the above configuration, the two fin plates (bonding members) 4A and 4B shown in FIGS. 10A and 10B can be bonded without using a brazing material, for example, Flux is applied to the opposing joint surface portions of the fin plates 4A (FIG. 10a) and 4B (FIG. 10b), superimposed on each other, and the periphery is crimped by press working or temporarily welded by laser welding. After stopping, it is done by brazing in a furnace in an atmospheric furnace.

  For this reason, it is important how to accurately achieve positioning at the time of joining, that is, an appropriate correspondence between the recessed groove portion for forming the heat transfer tube body portion 41 and the fin joining surface.

  The present invention has been made on the basis of such circumstances, and by forming engagement portions that engage in the coaxial direction at a plurality of positions corresponding to each other between heat transfer fin plates to be bonded together, the present invention is simple and low. An object of the present invention is to provide a small-diameter multi-tube heat exchanger thin-diameter heat transfer tube unit capable of realizing an appropriate correspondence between the concave groove portion for forming the heat-transfer tube tube portion and the fin joint surface at a low cost. Is.

  In order to achieve the object, the present invention includes the following problem solving means.

(1) First problem-solving means The first problem-solving means of the invention of the present application is that the pipe portions 41, 41... Are formed by bonding the heat transfer fin plates 4A, 4B having the concave grooves for forming the tubes. Of the small-diameter multitubular heat exchanger configured so that heat transfer fins 42, 42... Are integrally provided on both sides of the body portions 41, 41. The small-diameter heat transfer tube units 4, 4... Are characterized in that engaging portions are formed at a plurality of positions of the heat transfer fin plates 4A and 4B in the coaxial direction at the time of bonding. Yes.

  According to such a configuration, the engaging portions formed so as to engage in the coaxial direction at the time of bonding are respectively attached to the heat transfer fin plates 4A and 4B at a plurality of positions, thereby being attached to each other. It is possible to realize an appropriate correspondence between the heat transfer tube sections 41, 41... Forming concave grooves and the fin joint surfaces at the time of alignment easily and at low cost.

(2) Second Problem Solving Means According to the second problem solving means of the present invention, in the configuration of the first problem solving means, the engaging portion includes holes 46a and 46b in which pin members communicate in the coaxial direction. 46a, 46b...

  According to such a configuration, the holes 46a, 46b in which the pin members communicate in the coaxial direction are provided so as to engage with each other in a plurality of corresponding positions of the heat transfer fin plates 4A, 4B to be bonded together, 46a, 46b, etc., it is possible to easily and inexpensively realize an appropriate correspondence between the groove portions 41 and 41 for forming the heat transfer tube portions 41 and 41 at the time of bonding and the fin joint surfaces. .

(3) Third Problem Solving Means According to a third problem solving means of the present invention, in the configuration of the first problem solving means, the engaging portion includes a hole 48 and a convex portion that are fitted in a coaxial direction. It is characterized by comprising part 47.

  According to such a configuration, the hole 48 and the convex portion which are fitted to each other in the coaxial direction so as to be engaged with each other in a plurality of positions corresponding to each other between the heat transfer fin plates 4A and 4B to be bonded together. 47 makes it possible to realize the appropriate correspondence between the heat transfer tube sections 41, 41... Forming concave grooves and the fin joint surfaces at the time of bonding easily and at low cost.

(4) Fourth Problem Solving Means According to a fourth problem solving means of the present invention, in the configuration of the first problem solving means, the engaging portion includes a concave portion 49 and a convex portion which are fitted in a coaxial direction. 47.

  According to such a configuration, the concave portion 49 and the convex portion 47 that are provided so as to engage with each other in the coaxial direction at a plurality of positions corresponding to each other between the heat transfer fin plates 4A and 4B to be bonded to each other. Thus, an appropriate correspondence between the groove portion for forming the heat transfer tube body portion at the time of bonding and the fin joint surface can be realized simply and at low cost.

(5) Fifth Problem Solving Means The fifth problem solving means of the present invention is the configuration of the first, second, third or fourth problem solving means, wherein the heat exchanger is a refrigeration apparatus such as an air conditioner. The internal fluid is a mixed refrigerant containing 50 wt% or more of R32, a single refrigerant of R32, or a high-pressure refrigerant such as a CO ₂ refrigerant.

  According to the configuration of the first, second, third or fourth problem solving means, the heat transfer fins are provided with the heat transfer fins 42 having a predetermined width on both sides of the tube portion 41 of the small-diameter heat transfer tube. In the small-diameter heat transfer tube unit 4 having the laminated structure of the plates 4A and 4B, the heat transfer fin plates 4A and 4B can be bonded accurately and reliably. Therefore, high sealing performance of the heat transfer fin 42 can be maintained, and high pressure performance can be improved.

Therefore, the heat exchanger is for a refrigerating apparatus such as an air conditioner, and the internal fluid is a mixed refrigerant containing 50 wt% or more of R32, or a single refrigerant of R32, or a high-pressure refrigerant such as a CO ₂ refrigerant. It is also suitable for a small-diameter heat transfer tube unit of a tube heat exchanger.

  As a result, according to the present invention, accurate and reliable positioning at the time of bonding the heat transfer fin plates can be achieved with a very simple and low-cost configuration.

Therefore, the sealing performance between the fin plate joint surfaces is also improved, and it is effective for a mixed refrigerant containing 50 wt% or more of R32 of a refrigerating apparatus such as an air conditioner, a single refrigerant of R32, or a high-pressure refrigerant such as a CO ₂ refrigerant. Thus, the heat exchange performance can be improved as much as possible.

(Best Embodiment 1)
1 to 4 show the structure of a small-diameter heat transfer tube unit of a small-diameter multi-tube heat exchanger according to the best embodiment 1 for carrying out the present invention.

  FIG. 5 and FIG. 6 show the configuration of a small-diameter multi-tube heat exchanger configured by adopting the small-diameter heat transfer tube unit having the same structure.

  That is, first, a small-diameter multitubular heat exchanger 1 shown in FIG. 5 includes an inlet header 2A and an outlet header 2B having a refrigerant distribution function arranged in parallel with each other at a predetermined interval, and the inlet header 2A and the outlet A heat exchange section composed of thin heat transfer tube units (fined heat transfer tubes with fins) 4, 4... Connected to each of the headers 2 </ b> B and arranged on the lower side along the longitudinal direction. 3.

  As shown in FIGS. 1 and 2, for example, the small-diameter heat transfer tube units 4, 4,... Have a tubular portion (thin-diameter tube portion) 41 of the heat transfer tube bent in a U shape as a whole. The open end portions 41c and 41d of the upper end convex portions 44a and 44b are respectively connected to the respective opening portions on the bottom side of the inlet header 2A and the outlet header 2B, while the U-shaped tube portion 41 is provided. The left and right straight portions 41a and 41b are respectively provided with fin portions 42a and 42b having predetermined widths located on the left and right sides thereof. The fin portions 42a and 42b on both sides of the straight portions 41a and 41b are continuous with each other to form one heat transfer fin 42 for the U-shaped tube portion 41.

  And the small diameter heat-transfer tube unit 4,4 ... provided with this tube part 41 (41a, 41b) and the heat-transfer fin 42 (42a, 42b) is shown to (a), (b) of FIG. As shown, thin and flat vertically elongated rectangular fin plates 4A and 4B each having a semi-circular groove having a semicircular cross section for forming a tubular body portion 41 (41a and 41b) are shown in FIGS. As shown in FIG. 3, they are formed by being bonded and integrated in a state of being opposed to each other, whereby fin portions 42 a are formed on both the left and right sides of the tubular portion 41 and the straight portions 41 a and 41 b of the tubular portion 41. , 42b constitute the same thin-diameter heat transfer tube unit 4, 4.

  In this case, holes 46a and 46b in which pin members communicate with each other in the coaxial direction are provided as engaging portions for positioning at a plurality of positions on the outer peripheral side corresponding to the two fin plates 4A and 4B to be bonded together. 46a, 46b... Are provided. And by connecting a pin member to each of these holes 46a, 46b, 46a, 46b..., Heat transfer tube portions 41, 41. This makes it possible to realize an appropriate correspondence relationship easily and at low cost.

  The small-diameter heat transfer tube units 4, 4... Configured as described above are arranged in parallel at a predetermined pitch in parallel with the flow direction of the external fluid F, for example, as shown in FIG. In the same arrangement state, each of the small-diameter heat transfer tube units 4, 4... Has an inlet header 2 A and an outlet header at the opening end portions 41 c, 41 d, 41 d, 41 c. 2B is connected, and finally the thin multi-tube heat exchanger 1 as shown in FIG. 5 is formed.

  According to such a configuration, the heat transfer fins 42 (42a, 42a, 41a, 41a, 41b, 42a, 41a, 41b) are further provided on both sides of the tube portion 41 (41a, 41b, 41a, 41b) of the small-diameter heat transfer tube having a high heat transfer rate. 42b) is added, in addition to the good heat transfer coefficient by the tube portion 41 (41a, 41b) of the small diameter heat transfer tube, the heat transfer area is also greatly increased, and the overall heat exchange performance is increased. It improves and becomes suitable for the use conditions as a heat exchanger for an air conditioner.

  By the way, in the case of such a configuration, when the heat exchange unit 3 is configured by arranging a plurality of small-diameter heat transfer tube units 4, 4... As shown in FIG. If they are arranged side by side, the adjacent pipe body parts 41 (41a, 41b) and 41 (41a, 41b) are close to each other and the ventilation resistance is increased, so that the fin pitch is also limited. On the other hand, in order to solve this problem, for example, if the positions are alternately changed in the front-rear direction in which the external fluid F flows and arranged in a zigzag structure as a whole, the size of the heat exchanger 3 is increased accordingly, and the compactness is improved In addition to being chipped, the positions of the opening end portions 41c and 41d for connection with the headers 2A and 2B are not aligned.

  Therefore, in this embodiment, as shown in FIGS. 1 to 4, for example, one of the two straight portions 41a and 41b of the U-shaped tube portion 41 is opened at its upper end side. Rather than linearly extending downward from the end 41d, it is once bent into a crank shape by a predetermined width a on the center side of the heat transfer fins 42 (crank portion R). The U-shaped tube part 41 (41a, 41b) is configured so as to be displaced to the left or right side of the heat transfer fin 42 as a whole.

  In this state, the heat transfer fin 42 is further provided between the two straight portions 41a and 41b of the tube portion 41 in the heat transfer fin 42 and at the center of the outer periphery side of the straight portion 41b bent in a crank shape. Two slits 43a and 43b having the same width as the outer diameter of the tube part 41 (41a and 41b) are provided as openings penetrating both sides of the tube.

  Moreover, the small-diameter heat transfer tube units 4, 4... Configured as described above are arranged in parallel with the left and right directions alternately reversed, as shown in FIGS. The flow of the external fluid F so that the straight portions 41a, 41b, 41a, 41b ... of the tube portions 41, 41 ... of the radial heat transfer tube units 4, 4 ... are arranged in a staggered manner as a whole. Arranged parallel to the direction.

  As a result, it is not necessary to shift the position of each of the small-diameter heat transfer tube units 4, 4. Since the pipe portions 41 (41a, 41b), 41 (41a, 41b)... Themselves are displaced by a predetermined dimension upstream and downstream in the flow direction of the external fluid F, and the distance between them increases, the external fluid F The flow path resistance of the tube portions 41 (41a, 41b), 41 (41a, 41b)... And the heat transfer fins 42 (42a, 42b), 42 (42a, 42b). Flows evenly and smoothly on the surface. Therefore, the heat exchange performance is improved without causing the heat exchange part 3 to expand.

  Further, in the case of the above configuration, the two fin plates (bonding members) 4A and 4B shown in FIGS. 4A and 4B are joined without using brazing material, for example, each fin plate. By applying flux to the opposing joint surface parts of 4A and 4B and overlaying each other and caulking the periphery by press working, or temporarily fixing by laser welding and then brazing in an oven in an atmosphere furnace Made.

  For this reason, in order to improve the sealing performance of the joint and prevent leakage of the refrigerant or the like, it is necessary to effectively and uniformly leak the flux gas generated between the joint surfaces during the joint.

  However, in the case of the configuration as shown in FIGS. 1 to 4, the heat transfer fins 42 (parts where the fin portions 42 a and 42 b are combined) as compared with the tube diameter φ of the thin tube portion 41 (41 a, 41 b). ) Since the width of the part is considerably large, the area of the joint surface is large, and it is difficult to vent the above-described flux gas. Therefore, improvement of the sealing performance and pressure resistance of the joint surface is a problem.

  In order to improve this, for example, brazing sheets may be frequently used and brazed in a furnace in a vacuum furnace. However, doing so increases costs and complicates the process of brazing in the furnace.

  Therefore, in this embodiment, two slits 43a and 43b extending in the vertical direction as openings penetrating the heat transfer fins 42 (42a, 42b), 42 (42a, 42b). ... the opening part which consists of is formed.

  Therefore, according to such a configuration, the fin width is actually reduced by the slits 43a, 43b... Penetrating through both sides of the heat transfer fins 42 (42a, 42b), 42 (42a, 42b). Effective degassing similar to the narrowing is possible, and the sealing performance and pressure resistance of the fin joint surface can be improved effectively.

Therefore, for example, it is possible to effectively cope with a mixed refrigerant (R410A) containing 50 wt% or more of R32, a single refrigerant of R32, or a high-pressure refrigerant such as a CO ₂ refrigerant, and the heat exchange performance is improved. be able to.

  Further, in the case of the above configuration, as is apparent from FIG. 6, the slits 43a, 43b are formed so that the tube portions 41 (41a, 41b), 41 () of the adjacent small-diameter heat transfer tube units 4, 4,. 41a, 41b)...

  Therefore, a part of the air flow that bends and flows laterally at each tubular body portion 41 (41a, 41b), 41 (41a, 41b)... Portion passes through the slits 43a and 43b to the adjacent passage. Also flows by bypass, the flow resistance is further reduced, and the leading edge effect is further improved.

(Best Mode 2)
Next, FIG. 7 shows the structure of the small-diameter heat transfer tube unit of the small-diameter multi-tube heat exchanger according to the second preferred embodiment when the present invention is implemented.

  In this configuration, the positioning engaging portions at the time of joining the fin plates 4A and 4B shown in FIGS. 4A and 4B are the holes 46a, 46b, and 46a in the configuration of the best embodiment 1 described above. .., 46b..., For example, as shown in FIG. 7, one fin plate 4B side hole 48 and the other fin plate 4A side spherical convex portion 47 are adopted, and these are shown in FIG. As shown in the figure, by engaging each other in the coaxial direction, it is positioned accurately, and the groove portions for forming the heat transfer tube portions 41, 41... (41a, 41b, 41a, 41b. The present invention is characterized in that an appropriate correspondence between the fin joint surfaces can be realized with a simple configuration.

  Even with such a configuration, the same effects as those of the first embodiment can be realized easily and at low cost.

(Best Mode 3)
Next, FIG. 8 shows the structure of a small-diameter heat transfer tube unit of a small-diameter multitubular heat exchanger according to the third preferred embodiment for carrying out the present invention.

  In this configuration, the engaging portions for positioning at the time of joining the fin plates 4A and 4B shown in FIGS. 4A and 4B are the holes 46a, 46b, 46a in the configuration of the first embodiment. For example, as shown in FIG. 8, a spherical concave portion 49 on one fin plate 4B side and a convex portion 47 on the other fin plate 4A side are adopted as shown in FIG. As shown in the cross-sectional view, the grooves are accurately positioned by engaging each other in the coaxial direction, and the groove portions for forming the heat transfer tube portions 41, 41... (41a, 41b, 41a, 41b...) In addition, the correspondence relationship between the fin joint surfaces can be realized with a simple configuration.

  Even with such a configuration, the same effects as those of the first embodiment can be realized easily and at low cost.

It is a perspective view which shows the structure of the thin diameter heat exchanger tube unit of the thin diameter multitubular heat exchanger which concerns on the best Embodiment 1 of this invention. It is an expansion perspective view of the principal part of the same small diameter heat exchanger tube unit. It is a horizontal sectional view (AA of FIG. 1) of the same small-diameter heat transfer tube unit. It is a figure which shows the structure of the opposing surface (joining surface) before bonding of the right-and-left fin plate (bonding member) of the same small diameter heat-transfer tube unit as compared with right and left. It is a perspective view which shows the structure of the small diameter multitubular heat exchanger formed by arranging the same small diameter heat exchanger tube unit in parallel. It is a horizontal sectional view which shows the structure of the heat exchange part of the same small diameter multi-tube heat exchanger. It is a horizontal sectional view which shows the structure of the engaging part for positioning at the time of joining of the thin diameter heat exchanger tube unit of the thin diameter multitubular heat exchanger which concerns on the best Embodiment 2 of this invention. It is a horizontal sectional view which shows the structure of the engaging part for positioning at the time of joining of the thin diameter heat exchanger tube unit of the thin diameter multi-tube heat exchanger which concerns on the best Embodiment 3 of this invention. It is a perspective view which shows the structure of the small diameter multitubular heat exchanger comprised using the conventional small diameter heat exchanger tube unit. It is an inner side front view which contrasts and shows the structure before bonding of the right-and-left fin plates (bonding member) of the small diameter heat exchanger tube unit which comprises the same small diameter multi-tube heat exchanger. It is a horizontal sectional view which shows the joining structure of the thin diameter heat exchanger tube unit part of the same thin diameter multi-tube heat exchanger.

Explanation of symbols

  1 is a thin multi-tubular heat exchanger, 2A is an inlet header, 2B is an outlet header, 3 is a heat exchanger, 4 is a small diameter heat transfer tube unit, and 41 is a U-shaped tube portion of the small diameter heat transfer tube unit 4 , 41a and 41b are straight portions of the tube body portion 41, 42 are heat transfer fins, 42a and 42b are fin portions, 46a and 46b are hole portions, 47 is a convex portion, 48 is a hole portion, and 49 is a concave portion.

Claims (5)

  Tube parts (41), (41) ... Tube parts (41), (41) ... by bonding heat transfer fin plates (4A), (4B) having concave grooves for formation And heat transfer fins (42), (42) ... are integrally provided on both sides of the tube portions (41), (41) ... The small-diameter heat transfer tube units (4), (4)... Are engaged with each other at a plurality of positions of the heat transfer fin plates (4A) and (4B) in the coaxial direction at the time of bonding. A thin heat transfer tube unit of a thin multi-tube heat exchanger, characterized in that a section is formed.   2. The small-diameter multi-tubular type according to claim 1, wherein the engaging portion includes holes (46a), (46b), (46a), (46b),. Small heat transfer tube unit for heat exchanger.   2. A small-diameter heat transfer tube unit of a thin multi-tubular heat exchanger according to claim 1, wherein the engaging portion includes a hole portion (48) and a convex portion (47) which are fitted in the same direction as each other. .   The small-diameter heat transfer tube unit of the small-diameter multitubular heat exchanger according to claim 1, wherein the engaging portion is composed of a concave portion (49) and a convex portion (47) which are fitted in the coaxial direction. The heat exchanger is for a refrigerating apparatus such as an air conditioner, and the internal fluid is a mixed refrigerant containing 50 wt% or more of R32, or a single refrigerant of R32, or a high-pressure refrigerant such as a CO ₂ refrigerant. The thin-diameter heat transfer tube unit of the thin-diameter multitubular heat exchanger according to claim 1, 2, 3, or 4.

Images