JP2008267716A - Cross fin tube type heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cross fin tube type heat exchanger capable of enhancing the heat radiation efficiency of an adjacent plate fin in contact with a heat transfer pipe and further improving heat exchanging performance. <P>SOLUTION: The cross fin tube type heat exchanger 10 is constituted in such a manner that the heat radiation surface of a base (collar connecting part 28) of a fin collar 20 with respect to a flat fin body 16 of the plate fin 14 is positioned outside a tapered surface formed around a collar body 24 on a straight line which connects a position (a) separated by 0.2×p (p indicates a layered pitch of the plate fin 14) in the height direction of the collar body 24 from a crossing point (0) as a reference point where the radiation surface of the fin body 16 on the side where the fin collar 20 of the plate fin 14 is positioned, and the outer surface of the collar body 24 of the fin collar 20 are extended and crossed, and a position (b) separated from the reference point (0) by 0.3×p in the direction of the fin body 18. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cross fin tube type heat exchanger that is suitably used for air conditioners such as home air conditioners, automobile air conditioners, packaged air conditioners, refrigerators, heat pump water heaters, and the like.

  Conventionally, heat exchangers that operate as evaporators or condensers have been used for air conditioners such as home air conditioners, automobile air conditioners, packaged air conditioners, refrigerators, heat pump water heaters, etc. In a domestic indoor air conditioner and a commercial packaged air conditioner, a cross fin tube heat exchanger is most commonly used.

  Further, as refrigerants in such heat exchangers, CFC (chlorofluorocarbon) refrigerants, HCFC (hydrochlorofluorocarbon) refrigerants, HFC (hydrofluorocarbon) refrigerants and the like have been conventionally used as refrigerants. However, in view of the serious global environmental problems in recent years, heat exchangers using natural refrigerants with a low global warming potential have been developed from the viewpoint of protecting the ozone layer and preventing global warming. A cross fin tube type heat exchanger using a refrigerant mainly composed of has been developed. Furthermore, in a heat pump water heater using an air heat exchanger that performs heat exchange between the refrigerant mainly composed of carbon dioxide and air, a similar cross fin tube heat exchanger is preferably used. It is.

  And the cross fin tube which comprises such a cross fin tube type heat exchanger is normally comprised by assembling | attaching the aluminum fin by the side of an air and the heat exchanger tube by the side of a refrigerant | coolant integrally. Further, in the method of manufacturing such a cross fin tube type heat exchanger, for example, first, aluminum plate fins in which a plurality of predetermined assembly holes are formed on the fin surface are formed by pressing or the like, and then After laminating a plurality of the obtained aluminum plate fins so that the positions of the plurality of assembly holes coincide with each other, a separately manufactured heat transfer tube was inserted into each of the assembly holes, and well A technique of adhering the heat transfer tube and the aluminum plate fin using a known mechanical tube expansion method or the like is employed. In addition, as the heat transfer tube used here, for example, a tube whose inner surface is grooved by rolling or the like is cut into a predetermined length and subjected to hairpin bending. Then, after the assembly is completed, the opening ends of the plurality of heat transfer tubes fixed to the aluminum plate fins are connected using a U-bend tube so that a passage of the heat transfer medium is formed. Thus, the intended cross fin tube type heat exchanger is manufactured.

  By the way, in such a cross fin tube type heat exchanger, various efforts have been made so far in order to improve the heat transfer performance.

  For example, as a heat transfer tube used in such a cross fin tube type heat exchanger, a number of grooves, for example, a plurality of grooves extending in a spiral shape with a predetermined lead angle with respect to the tube axis are formed on the inner surface thereof. The so-called inner-surface grooved heat transfer tube, in which inner fins of a predetermined height are formed between the grooves, is often used. In addition, by making various improvements, the heat transfer coefficient in the pipe is increased and the heat transfer performance of the heat exchanger is improved.

  On the other hand, with regard to heat transfer enhancement in aluminum fins, for example, in JP-A-2-203199 (Patent Document 1), the fin surface is long in the direction perpendicular to the air flow (air flow) and rises. It has been clarified how to increase the surface area of the fins and make the fins easy to touch the fresh air supplied by providing cuts (louvers) in which the pieces are inclined with respect to the airflow direction.

  In JP-A-11-108575 (Patent Document 2), winglets made of cantilever-like projections are formed at a plurality of locations near the tip of the fin surface on the air inflow side, and the downstream side thereof. A heat exchanger has been proposed in which a louver that is cut and raised in the form of a beam supported at both ends is formed to generate vortices in the air flowing between the fins to disturb the air flow and promote heat transfer.

  Furthermore, recently, attention has also been paid to the reduction of contact thermal resistance between the heat transfer tube and the aluminum fin. For example, in Japanese Patent Application Laid-Open No. 2004-125235 (Patent Document 3), The presence of a solidified or hardened resin layer or organic / inorganic hybrid ceramic layer in at least part of the space between the heat transfer tubes reduces the effect of voids formed between the heat transfer tubes and the fins, improving heat transfer performance Attempts have also been made.

JP-A-2-203199 JP-A-11-108575 JP 2004-125235 A

  By the way, in recent years, particularly from the viewpoint of energy saving, there has been a demand for further improvement in the performance of cross fin tube type heat exchangers used in various air conditioners, and the present inventors have tackled such problems. As a result of intensive research, we have gained knowledge about the following factors affecting the heat transfer performance.

  That is, in the vicinity of the contact portion of the plate fin (aluminum fin) with the heat transfer tube, there is a region where the flow velocity of the air to be heat-exchanged approaches 0, and therefore the heat flow velocity at the fin base becomes extremely small. It is. In other words, in the conventional cross fin tube type heat exchanger, the plate fins in the vicinity of the heat transfer tubes make very little contribution to heat dissipation.

  Here, the present invention has been obtained based on the above findings and further investigation on the optimization of the shape of the plate fins. And the place made into the objective is to provide the cross fin tube type heat exchanger which can further improve the heat exchange performance by raising the heat dissipation efficiency of the plate fin of the neighborhood which contacts a heat exchanger tube. is there.

  And this invention was completed based on this knowledge, and the place made into the summary is the plate provided with the assembly hole by which the cylindrical collar part of predetermined height is provided in the circumference | surroundings of a hole. Using a plurality of fins, stacking the plurality of plate fins so that the assembly holes correspond and the collar portion is located on the same side, while inserting a heat transfer tube into the assembly holes and expanding the tubes Thus, in the cross fin tube type heat exchanger having a structure in which the heat transfer tube is integrally assembled with the plate fin, the heat radiation surface of the base portion of the collar portion with respect to the fin flat portion of the plate fin is the collar. The intersection point on the extended line between the heat radiating surface of the fin flat portion on the side where the portion is located and the outer surface of the collar portion is taken as a reference point, and 0.2 × p (provided that p in the height direction of the collar portion from this reference point) Is formed around the collar portion by a straight line connecting a position a apart from the reference point and a position b 0.3 × p away from the reference point in the direction of the flat portion of the fin. The cross fin tube type heat exchanger is configured to be located outside the tapered surface.

  According to one of the desirable embodiments of the cross fin tube heat exchanger according to the present invention, the heat radiating surface of the base portion of the collar portion has the axis in the cross section where the axis of the heat transfer tube is located. It will be configured to give a straight line that is inclined with respect to the heart.

  Further, in another desirable mode of the cross fin tube type heat exchanger according to the present invention, the heat radiation surface of the base portion of the collar portion is 0 in the cross section where the axial center of the heat transfer tube is located. It will be configured to provide an arcuate portion having a radius of curvature of .45xp or greater.

  Therefore, according to the cross fin tube type heat exchanger configured according to the present invention, the heat radiation surface of the base portion in the cylindrical collar portion provided around the assembly hole provided in the plate fin is provided. The heat radiation efficiency in the vicinity of the contact portion between the plate fin and the heat transfer tube is effectively increased from being configured to be located outside the predetermined region, and thus heat exchange of the heat exchanger The performance can be further improved.

  Hereinafter, in order to clarify the configuration of the present invention more specifically, the cross fin tube heat exchanger according to the present invention will be described in detail with reference to the drawings.

  First, in FIG. 1, an example of the appearance of a general cross fin tube heat exchanger to which the present invention is applied is schematically shown in the form of a sectional view thereof. That is, in FIG. 1, the heat transfer tube 12 has an internally grooved transfer made of a predetermined metal material, which is appropriately selected from copper, copper alloy, or the like according to required heat transfer performance. Here, the heat transfer tube 12 is used in a U-shape. On the other hand, the plate fin 14 which is a plate-like heat radiating fin is formed of a predetermined metal material such as aluminum or an alloy thereof as in the conventional case, and the flat fin main body portion 16 is shown in FIG. As shown in FIG. 2, a plurality of assembly holes 18 are provided at predetermined intervals, and a fin collar 20 is provided around the plurality of assembly holes 18 as shown in FIG. They are formed in a structure in which each is integrally erected.

  A plurality of such plate fins 14 become holes that penetrate in the left-right direction in the state in which the respective assembly holes 18 are aligned and the fin collar 20 is positioned on the same side (in FIGS. 1 and 3). In addition, after the heat transfer tube 12 is inserted into the matching assembly hole 18, the heat transfer tube 12 is expanded in the same manner as before. Thus, a cross fin tube in which the heat transfer tube 12 and the plate fin 14 are fixed to each other is formed.

  Further, the open ends of the heat transfer tubes 12 fixed to the plate fins 14 of such a cross fin tube are connected to each other using a U-bend tube 22 having a U shape as shown in FIG. The cross fin tube type heat exchanger 10 is configured. Here, such a U-bend tube 22 is configured such that its outer diameter is such that it can be inserted into an opening at the end of the heat transfer tube 10. Are inserted into the openings of the adjacent ends of the heat transfer tubes 12 and 12 so as to connect the adjacent heat transfer tubes 12 and 12, respectively, and then inserted into the inner peripheral surface of the heat transfer tube 12 and the U bend By pouring a brazing material into a gap formed between the outer peripheral surface of the tube 22, the heat transfer tubes 12 and 12 and the U vent tube 22 are brazed and joined, and the heat transfer tubes 12 are connected in series. Heat transfer refrigerant is allowed to flow through the heat transfer tubes 12 fixed to the laminated plate fins 14.

  In the cross fin tube heat exchanger 10 having such a configuration, the thickness (t) of the plate fin 14 is variously selected according to the size of the heat exchanger 10 and the heat exchange performance. It is desirably about 0.1 mm. Moreover, even if it exists in the space | interval (pitch: p) between the adjacent plate fins 14 and 14, although it will be suitably determined according to the desired heat transfer performance etc. of a heat exchanger, generally 1.0 mm The interval is about ˜2.0 mm, preferably about 1.5 mm.

  Further, the fin collar 20 portion where the plate fin 14 and the heat transfer tube 12 are in contact with each other has a cylindrical shape with a predetermined height that is actually in contact with the heat transfer tube, as shown in the enlarged sectional views of FIGS. A collar body portion 24, a flare portion 26 formed at the tip of the color body portion 24 that exerts an effect of keeping the fin pitch (p) stable by contacting the adjacent plate fins 14, and a color body The collar 24 includes a collar connecting portion 28 that smoothly connects the portion 24 to the fin body portion 16 of the plate fin 14 with a predetermined radius of curvature R (here, approximately 0.25 mm).

  Thus, in the cross fin tube type heat exchanger 10 configured by assembling the plate fins 14 to the heat transfer tubes 12, heat is transferred from the heat transfer tubes 12 to the plate fins 14, and from the plate fins 14 to the air outside thereof. In the present situation where the pitch (p) of adjacent plate fins 14 is becoming narrower, fresh air sent by a fan between the plurality of stacked plate fins 14 at the base of the plate fins 14 It is not possible to sufficiently send the heat transfer tube 12 and the vicinity of the plate fin 14.

  That is, in such a region, the flow velocity of the air to be heat-exchanged is almost 0, so that the heat flow rate at the root of the plate fin 14 becomes extremely small. In other words, the plate fins 14 in contact with the heat transfer tubes 12 have a very small contribution to heat dissipation. Then, as a result of various studies by the present inventors, such a region is a triangular region A such as a peripheral portion of the base portion of the assembly hole 18 in the plate fin 14, that is, a hatched portion shown in FIG. It has been found that this is remarkable in a tapered region formed around the fin collar 20 having a cross-sectional shape.

  Specifically, as shown in FIG. 4 represented as a cross-sectional view in which the axial center of the heat transfer tube 12 is located on the surface, the heat radiation surface of the fin body portion 16 on the side where the fin collar 20 of the plate fin 14 is located, Extending the outer surface of the collar body 24 of the fin collar 20 and intersecting the intersection: 0 is a reference point, and 0.2 × p (provided that p in the height direction of the collar body 24 from the reference point (0)) As shown in FIG. 3, the position “a” apart (which indicates the stacking pitch of the plate fins 14) and 0.3 in the direction in which the fin main body 18 extends (separates from the heat transfer tube 12) from this reference point (0). In a region inside the taper surface formed around the collar main body portion 24 on a straight line connecting the b positions separated by × p, in other words, the three points of the a position, the b position, and the reference point (0). In the triangular area (A) surrounded by It became clear that the contribution to heat dissipation was extremely small.

  Therefore, even if the heat dissipation surface B of the plate fin 14 is provided in such a region A, the portion hardly contributes to heat dissipation. Therefore, in order to improve the heat dissipation performance, this region is as much as possible. Since it is desirable to provide the plate fin 14 while avoiding A, in the present invention, the base portion of the fin collar 20, that is, the collar body portion 24 of the fin collar 20 and the fin body portion of the plate fin 14. 16 is a mortar-shaped taper surface formed by rotating the straight line connecting the a position and the b position around the axis of the heat transfer tube 12. It is configured to be located on the outer side.

  And from such a viewpoint, the cross fin tube type heat exchanger configured according to the present invention is shown in FIGS. 5 and 6 in the form of a cross-sectional view in which the joint portion of the heat transfer tube 12 and the plate fin 14 is enlarged. Has been.

  That is, FIG. 5 shows a cross section where the base portion of the fin collar 20, that is, the collar connecting portion 28 that connects the collar body portion 24 and the fin body portion 16 of the plate fin 14, is located at the axis of the heat transfer tube 12. In this case, the heat sinking surface B of the plate fin 14 has a taper shape in which the collar connecting portion 28 gradually decreases in diameter from the fin main body portion 16 side toward the collar main body side 24 by being configured to be linear. What is configured to avoid the triangular region A is shown.

  On the other hand, in FIG. 6, the plate fin 14 is provided by providing a relatively large root R (here, 0.45 × p) at a portion of the collar connecting portion 28 that connects the collar body portion 24 and the fin body portion 16. In the cross section where the heat radiating surface B of the heat transfer tube 12 is located, the region A obtained as described above is avoided. In order to avoid the heat radiation surface of the base portion (28) of the fin collar 20 from being located in the region A by increasing the fin base R in this way, the curvature radius R is 0.45 × It will be set to p or more.

  Thus, according to the cross fin tube type heat exchanger configured according to the present invention, the fin collar 20 provided around the hole 18 of the assembly hole 18 for assembling the heat transfer tube 12 to the plate fin 14. A heat radiating surface B in the base portion, that is, the collar connecting portion 28 portion that connects the flat fin main body portion 16 of the plate fin 14 and the cylindrical collar main body portion 24 of the fin collar 20, is determined by a predetermined pitch pitch (p). The heat radiation efficiency in the vicinity of the contact portion between the plate fin 14 and the heat transfer tube 12 can be effectively increased from the position that is configured to be located outside the region (A). It is possible to further improve the heat exchange performance of the vessel.

  As mentioned above, although one of the typical embodiments of the present invention has been described in detail, they are merely examples, and the present invention is based on a specific description according to such embodiments. It should be understood that this should not be construed as limiting in any way. And although not enumerated one by one, the present invention can be implemented in an aspect to which various changes, modifications, improvements, etc. are added based on the knowledge of those skilled in the art. It goes without saying that any one of them falls within the scope of the present invention without departing from the spirit of the present invention.

  In the following, one of the representative embodiments of the present invention will be shown to clarify the features of the present invention. However, the present invention is not restricted by the description of such embodiments. It goes without saying that it is not a thing.

First, in order to perform a numerical fluid simulation, it was decided to produce a model of a cross fin tube heat exchanger as shown in FIG. Here, pure copper is used for the material of the heat transfer tubes constituting the heat exchanger, and pure aluminum is used for the material of the plate fins. Further, the size and interval of the fins and the heat transfer tubes are as shown in FIG. Plate fin thickness (t): 0.1 mm, plate fin spacing (fin pitch: p): 1.4 mm, heat transfer tube pitch (p ₂ ): 25 mm, heat transfer tube outer diameter (D): 8.45 mm It was.

  And as a heat exchanger applicable to the structure according to this invention, the fin main-body part (16) of a plate fin (14) and the color main-body part (20) of a fin collar (20) as shown in FIG. 5 of above-mentioned embodiment. A structure having a structure in which the collar connecting portion (28) for connecting 24) is a straight line inclined with respect to the axis of the heat transfer tube (12) is modeled and used as an example. In addition, regarding the connecting portion between the both ends of the collar connecting portion (28) and the fin body portion (16) or the collar body portion, it is actually smoothly connected with a small radius of curvature R as shown in FIG. However, it is simplified to a model having a shape as shown in FIG. Further, in order to exclude the influence of the contact area between the heat transfer tube and the plate fin, a model was used in which aluminum was embedded in a non-contact portion (cross hatched portion in FIG. 8) between the heat transfer tube and the plate fin.

  The dimension of the collar connecting portion (28) formed to have a linear shape inclined with respect to the axial center in this way is the height of the collar body portion (24) from the heat radiation surface of the fin body portion (16). The distance in the direction (distance from the heat radiation surface of the fin body part to the point a ′) is set to 0.30 mm, which is larger than 0.2 times (0.28 mm) of the fin pitch (p), and the collar body part (24). The distance in the direction from the outer surface to the fin body (16) (the distance from the outer surface of the collar body to the point b ') is 0.45 mm, which is larger than 0.3 times (0.42 mm) the fin pitch (p). did.

  On the other hand, as a cross fin tube type heat exchanger having a conventional structure, as shown in FIG. 9, the fin body (16) of the plate fin (14) and the collar body (24) of the fin collar (20). Were modeled as shapes connected with a relatively small radius of curvature, and this was used as a comparative example. The radius of curvature (R) was 0.25 mm, which is smaller than 0.45 times (0.63 mm) the fin pitch (p).

A numerical fluid simulation was performed using the models of Examples and Comparative Examples prepared as described above, and the heat transfer performance was evaluated. The calculation model of the cross-fin tube type heat exchanger to be calculated was a model in which air at a front wind speed of 1.4 m / s and air at 35 ° C. and a heat transfer tube at 39 ° C. exchange heat through fins. The calculation area was an area for one fin and one heat transfer tube (hatched portion in FIG. 7), and a symmetrical boundary was given to the fin cross section, and a periodic boundary was given to the fin stacking direction. In modeling, in order to analyze only the air side, an isothermal condition was given to the outer surface of the heat transfer tube as a boundary condition. For this numerical analysis, general-purpose fluid software is used, the second-order center difference is used for the diffusion term, the second-order upwind difference is used for the convection term, and the SIMPLE method is applied to calculate the pressure, and the flow is calculated as a laminar flow. It was. In addition, as a condition of the contact surface between the aluminum fin and the heat transfer tube, the contact conductance was set to 9000 (W / m ² K).

  According to the simulation results as described above, the heat exchanger of the embodiment according to the present invention has a heat transfer amount increased by about 2% compared to the heat exchanger of the comparative example having the conventional structure. Confirmed to do. Thereby, it was confirmed that the effect of improving the heat transfer performance of the heat exchanger can be obtained by improving the shape of the plate fin in the vicinity of the contact portion between the heat transfer tube and the plate fin.

It is explanatory drawing which shows schematically an example of the general cross fin tube type heat exchanger with which this invention is applied in the form of sectional drawing. It is a cross-sectional explanatory drawing which expands and shows the circumference | surroundings of the assembly hole of the heat exchanger tube of the plate fin which comprises the cross fin tube type heat exchanger shown by FIG. FIG. 2 is an explanatory cross-sectional view showing an enlarged view of a cross section where the axial center of the heat transfer tube is located in the vicinity of the joint between the heat transfer tube and the plate fin in the cross fin tube heat exchanger. Is an enlarged version. FIG. 4 is an enlarged cross-sectional explanatory view showing a II part in FIG. 3. An example of a cross fin tube type heat exchanger having a structure according to the present invention, in which the vicinity of the joint between the heat transfer tube and the plate fin is cut at a cross section where the axis of the heat transfer tube is located, and the cross section is shown in an enlarged manner FIG. 5 is an explanatory diagram corresponding to FIG. 4. Another example of a cross fin tube type heat exchanger having a structure according to the present invention is shown by cutting the vicinity of the junction between the heat transfer tube and the plate fin at a section where the axis of the heat transfer tube is located, and enlarging it. FIG. 5 is a cross-sectional explanatory diagram corresponding to FIG. 4. It is explanatory drawing which shows arrangement | positioning of a heat exchanger tube and a plate fin of the cross fin tube type heat exchanger examined in the Example. It is explanatory drawing which cut | disconnects and shows the joint part vicinity of a heat exchanger tube and a plate fin in the cross section in which the axial center of a heat exchanger tube is located of the cross fin tube type heat exchanger of the structure according to this invention examined in the Example. . It is explanatory drawing which cut | disconnects and shows the junction part vicinity of a heat exchanger tube and a plate fin of the cross fin tube type heat exchanger of the conventional structure examined in the Example in the cross section in which the axial center of a heat exchanger tube is located.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Heat exchanger 12 Heat transfer tube 14 Plate fin 16 Fin main-body part 18 Assembling hole 20 Fin collar 22 U-bend pipe 24 Color main-body part 26 Flare part 28 Color connection part

Claims (3)

Using a plurality of plate fins having an assembly hole in which a cylindrical collar portion of a predetermined height is provided around the hole, so that the assembly hole corresponds and the collar portion is located on the same side, A cross fin tube type heat exchange having a structure in which the heat transfer tubes are integrally assembled to the plate fins by stacking the plurality of plate fins and inserting the heat transfer tubes into the assembly holes and expanding the plate fins. In the vessel
The heat radiation surface of the base portion of the collar portion with respect to the fin flat portion of the plate fin is based on the intersection point on the extension line between the heat radiation surface of the fin flat portion on the side where the collar portion is located and the outer surface of the collar portion, A position 0.2 × p away from this reference point in the height direction of the collar portion (where p represents the stacking pitch of the plate fins), and 0. 0 from the reference point toward the fin flat portion. A cross fin tube type heat exchanger configured so as to be positioned outside a tapered surface formed around the collar portion along a straight line connecting b positions separated by 3 × p.   2. The cross fin tube according to claim 1, wherein a heat radiating surface of a base portion of the collar portion is configured to give a straight portion inclined with respect to the axis in a cross section where the axis of the heat transfer tube is located. Mold heat exchanger. The heat radiation surface of the base portion of the collar portion is configured to give an arc-shaped portion having a radius of curvature of 0.45 × p or more in a cross section where the axis of the heat transfer tube is located. Cross fin tube type heat exchanger.

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