JP2012037156A - Fin tube heat exchanger - Google Patents

Abstract

A fin tube heat exchanger that can quickly remove water generated by defrosting operation from the surface of a fin.
A finned tube heat exchanger includes a plurality of fins and heat transfer tubes. Each of the plurality of fins 31 includes (a) an upwind portion 310 including the front edge 31f, (b) a cut and raised portion 12 formed on the upstream side of the upstream end 21p of the heat transfer tube 21, and (c) an upwind portion. And a flat portion 312 located behind 310. The cut and raised portion 12 has an opening 41 that can receive air from the upstream side in the airflow direction and guide the air from the first main surface side of the fin 31 to the second main surface side. The windward portion 310 is bent in a direction in which the opening 41 of the cut and raised portion 12 is enlarged, and is inclined with respect to the flat portion 312.
[Selection] Figure 2

Description

  The present invention relates to a finned tube heat exchanger.

  A finned tube heat exchanger having a plurality of heat transfer fins (hereinafter simply referred to as “fins”) arranged in parallel and a heat transfer tube passing through the plurality of fins is well known. Among them, fins formed so that peaks and valleys appear alternately along the airflow direction are called “corrugated fins”, and are widely used as fins boasting high performance.

  As fins other than the corrugated fins, those described in Patent Documents 1 and 2 are known. The fins described in Patent Documents 1 and 2 are formed with cut-and-raised portions called “louvers”. These fins are often referred to as “louver fins” and are widely used like corrugated fins.

JP-A-11-281279 JP 2001-141383 A

  As one of the problems when a finned tube heat exchanger is used in an outdoor heat exchanger (evaporator) of a heat pump, adhesion of frost to the fins at a low temperature is known. As the frost adheres, the air passage gradually narrows, causing an increase in pressure loss and a decrease in heat transfer performance. Therefore, in the heat pump, an operation for removing frost (so-called defrost operation) is periodically performed. If the number of defrosts can be reduced without degrading the performance of the finned tube heat exchanger, an improvement in cycle COP (coefficient of performance) can be expected.

  Moreover, one problem when performing defrost operation is that water droplets are generated on the surface of the fin. That is, if water generated by melting frost is not quickly removed from the surface of the fin, the water may increase air pressure loss or freeze again in the next normal operation. Furthermore, the water remaining on the surface of the fin prevents the temperature of the fin from rising. A general heat pump is controlled to end the defrost operation when the surface temperature of the fin reaches a predetermined temperature. If water remains on the surface of the fin, extra heat is required to raise the temperature of the remaining water, so the efficiency of the defrost operation is reduced. In particular, when a cut-and-raised part such as a louver is provided on the fin, water is easily retained around the cut-and-raised part, and thus the above problem becomes apparent.

  In view of the above circumstances, an object of the present invention is to provide a finned tube heat exchanger that can quickly remove water generated by defrosting operation from the surface of the fins.

That is, the present invention
A plurality of fins arranged in parallel to form an air flow path;
A plurality of fins, including a heat transfer tube through which a medium that exchanges heat with air flows,
Each of the plurality of fins includes (a) a windward portion including a straight leading edge of the fin, and (b) cutting a part of the fin, thereby causing an air flow direction to be higher than an upstream end of the heat transfer tube. A cut and raised portion formed on the upstream side, and (c) a flat portion located rearward of the windward direction with respect to the airflow direction,
The cut and raised portion has an opening that can receive air from the upstream side in the airflow direction and guide the air from the first main surface side to the second main surface side of the fin,
The opening of the cut and raised portion has an opening edge that has a convex shape toward the upstream side in the airflow direction in plan view,
The opening edge includes one end and the other end defined at the same position with respect to the airflow direction;
The windward portion is bent in a direction in which the opening of the cut-and-raised portion is enlarged, and is inclined with respect to the flat portion;
A direction parallel to the front edge is a width direction, a straight line passing through the one end and the other end of the opening edge is a first reference line, a straight line passing through the upstream end of the opening edge parallel to the width direction and the air flow direction When defined as a second reference line, a bending line resulting from the bending of the windward is (i) parallel to the width direction, and (ii) coincides with the first reference line, Alternatively, the present invention provides a finned tube heat exchanger that is located in a range downstream from the second reference line and upstream from the first reference line.

  According to the finned tube heat exchanger of the present invention, the fin has a cut-and-raised portion formed on the upstream side of the upstream end of the heat transfer tube. The cut-and-raised part has an opening that can guide air from the first main surface side to the second main surface side of the fin. The windward portion including the leading edge is bent in a direction to expand the opening of the cut and raised portion, and is inclined with respect to the flat portion of the fin. According to such a structure, water is less likely to be held around the cut-and-raised portion, for example, at the opening of the cut-and-raised portion, compared to a case where the windward portion is not bent. Therefore, according to the present invention, it is possible to provide a finned tube heat exchanger that can quickly remove water generated in the defrosting operation from the surface of the fins.

The perspective view of the finned-tube heat exchanger which concerns on 1st Embodiment of this invention. The top view of the fin used for the fin tube heat exchanger of FIG. Partial enlarged plan view of the fin shown in FIG. Partial enlarged sectional view of the fin along the line IVA-IVA in FIG. Partial enlarged sectional view of the fin before the windward part is bent 1 is a cross-sectional view of the finned tube heat exchanger of FIG. 1 along the line V-V in FIG. Partial expanded sectional view of the fin which concerns on a modification Plan view of another example of cut-and-raised part Front view of yet another example of cut and raised part Front view of cut and raised part Front view of another example of cut and raised part Front view of yet another example of cut and raised part Plan view showing the detailed position of the cut and raised part Graph showing the relationship between the distance from the front edge of the fin and the local heat transfer coefficient Graph showing the relationship between the position of the cut-and-raised part and the average heat transfer coefficient Contour map showing temperature distribution around heat transfer tube The perspective view of the finned-tube heat exchanger which concerns on 2nd Embodiment of this invention. The top view of the fin used for the finned-tube heat exchanger of FIG. Sectional drawing of the finned-tube heat exchanger of FIG. 13 along the XV-XV line in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
As shown in FIG. 1, the finned tube heat exchanger 1 of the present embodiment includes a plurality of fins 31 arranged in parallel to form a flow path for air A and a plurality of fins 31 penetrating these fins 31. And a heat transfer tube 21. The finned tube heat exchanger 1 is configured to exchange heat between the medium B flowing inside the heat transfer tube 21 and the air A flowing along the surface of the fin 31. The medium B is a refrigerant such as carbon dioxide and hydrofluorocarbon. The heat transfer tubes 21 may be connected to one or may not be connected.

  As shown in FIG. 2, the fin 31 has a straight front edge 31f. In this specification, the direction in which the fins 31 are arranged is defined as the height direction, the direction parallel to the front edge 31f is defined as the width direction, and the direction perpendicular to the height direction and the width direction is defined as the airflow direction (air flow direction). As shown in FIG. 1, the airflow direction, the height direction, and the width direction correspond to the X direction, the Y direction, and the Z direction, respectively.

  The fin 31 typically has a rectangular and flat plate shape. The longitudinal direction of the fin 31 coincides with the width direction. In the present embodiment, the fins 31 are arranged at a constant interval (fin pitch). However, the interval between the two fins 31 adjacent to each other in the height direction is not necessarily constant, and may be different.

  As a material for the fins 31, a flat plate made of aluminum having a thickness of 0.05 to 0.8 mm that has been punched can be suitably used. From the viewpoint of improving fin efficiency, the thickness of the fin 31 is particularly preferably 0.08 mm or more. The surface of the fin 31 may be subjected to a hydrophilic treatment such as a boehmite treatment and application of a hydrophilic paint. It is also possible to perform a water repellent treatment instead of the hydrophilic treatment.

  The heat transfer tube 21 is inserted into a through hole 31 h formed in the fin 31. A fin collar 5a is formed by a part of the fin 31 around the through hole 31h, and the fin collar 5a and the heat transfer tube 21 are in close contact with each other. The diameter φ of the through hole 31h is, for example, 1 to 20 mm, and may be 4 mm or less. The diameter φ of the through hole 31 h matches the outer diameter of the heat transfer tube 21. Moreover, the dimension L of the fin 31 regarding an airflow direction is 15-25 mm, for example.

  The fin 31 has an upwind portion 310 that is a portion including a straight front edge 31f. The windward portion 310 is bent in the depth direction of the paper surface in FIG. A bending line 42 is formed on the fin 31 due to the bending of the windward portion 310.

  A cut-and-raised portion 12 having a front edge different from the front edge 31 f is formed on the upstream side in the airflow direction as viewed from the heat transfer tube 21 by cutting and raising a part of the fin 31. Specifically, the cut-and-raised part 12 is located upstream of the upstream end 21p (specifically, the upstream end of the fin collar 5a or the through hole 31h) of the heat transfer tube 21 in the airflow direction.

  The fin 31 further includes a flat portion 312 that is located behind the upwind portion 310 in the airflow direction. Specifically, the flat portion 312 is located behind the cut and raised portion 310 in the airflow direction. The flat portion 312 constitutes a portion other than the cut and raised portion 12 and the windward portion 310.

As shown in FIG. 3, the cut-and-raised part 12 receives air from the upstream side in the airflow direction and guides it from the first main surface side (upper surface side) of the fin 31 to the second main surface side (lower surface side). An opening 41 is formed. The opening 41 of the cut-and-raised part 12 has an opening edge 41e that has a convex shape toward the upstream side in the airflow direction in plan view. In the present embodiment, the opening edge 41e has an arc shape in plan view. Further, the opening edge 41e includes an end E ₁ and the other end E ₂ defined in the same position with respect to the air flow direction.

  In this specification, “plan view” means observing objects such as the fins 31 and the openings 41 from a direction perpendicular to the flat portion 312 (Y direction).

  As shown in FIG. 4A, the windward portion 310 is bent in a direction in which the opening 41 of the cut and raised portion 12 is expanded. The “direction in which the opening 41 is expanded” represents a direction opposite to the protruding direction of the cut and raised portion 12. That is, if the protruding direction of the cut and raised portion 12 is the positive Y direction, the bending direction of the windward portion 310 is the negative Y direction.

As shown in FIG. 4B, the height H ₁ of the opening 41 before bending the windward portion 310 is equal to the height of the cut and raised portion 12. On the other hand, as shown in FIG. 4A, the height H ₂ of the opening 41 after the windward portion 310 is bent does not coincide with the height of the cut-and-raised portion 12, and the height H ₁ before the windward portion 310 is bent. (See FIG. 4B). That is, the opening 41 is expanded. This makes it difficult for water to be retained around the cut and raised portion 12. In particular, by increasing the height of the opening 41, a bridge of water based on the surface tension is hardly formed in the opening 41.

  The “height of the opening 41” means the maximum height of the opening 41 measured by observing the opening 41 from the upstream side in the airflow direction.

In the present embodiment, the boundary between the windward portion 310 and the flat portion 312, that is, the bend line 42 formed by bending the windward portion 310 is defined at the next position. As shown in FIG. 3, a straight line passing through one end E ₁ and the other end E ₂ of the opening edge 41 e is defined as a first reference line 45. The first reference line 45 is a virtual straight line on the surface of the fin 31. The bending line 42 is parallel to the width direction and coincides with the first reference line 45. When the windward portion 310 is bent so that the bending line 42 coincides with the first reference line 45, the height of the opening 41 can be increased to the maximum. From the viewpoint of enhancing the effect of removing water from the surface of the fin 31, the height of the opening 41 is preferably as high as possible.

However, even when the bending line 42 does not coincide with the first reference line 45, the opening 41 can be expanded by bending the windward portion 310. Specifically, as shown in FIG. 3, a straight line passing through the upstream end 41p of the opening edge 41e in the airflow direction is defined as a second reference line 46. The second reference line 46 is also a virtual straight line on the surface of the fin 31 and is parallel to the width direction. The bend line 42 may be located in a specific range R ₁ downstream of the second reference line 46 and upstream of the first reference line 45. As shown in FIG. 6, is as high as the opening 41 when the bending line 42 to a specific range R ₁ Curved Kazejobu 310 so as to be positioned, than before (see FIG. 4B) to bend Kazejobu 310 Increase.

As shown in FIG. 3, a straight line existing at an equal distance from the first reference line 45 and the second reference line 46 is further defined as a third reference line 47. The third reference line 47 is also a virtual straight line on the surface of the fin 31 and is parallel to the width direction. The bend line 42 may be located in a specific range R ₂ downstream of the third reference line 47 and upstream of the first reference line 45. In this case as well, the opening 41 can be expanded.

  As shown in FIGS. 4A and 5, the inclination angle β of the windward portion 310 with respect to the flat portion 312 is such that the front edge 31 f is positioned between the flat portions 312 and 312 adjacent to each other with respect to the height direction. It has been adjusted. In this way, an increase in pressure loss due to the bending of the windward portion 310 can be suppressed.

  Since the inclination angle β depends on other design conditions such as the distance (fin pitch) between the fins 31 adjacent to each other, the dimensions of the windward portion 310, etc., it cannot be uniquely determined. The range is set to 30 degrees.

  Next, the cut and raised portion 12 will be described in more detail. In the present embodiment, the cut and raised portion 12 has a semicircular shape in plan view. However, the shape of the cut and raised portion 12 is not particularly limited. As shown in FIGS. 7A and 7B, the cut-and-raised portion 12 may have a polygonal shape in plan view. 7A shows a cut and raised portion 12 having a triangular shape, and FIG. 7B shows a cut and raised portion 12 having a rectangular shape.

As shown in FIG. 4A, the dimension L ₁ (length) of the cut-and-raised portion 12 in the airflow direction is, for example, 0.5 to 1.5 mm. As shown in FIG. 8A, the opening 41 has a semicircular shape when viewed from the upstream side in the airflow direction. The dimension W ₁ (lateral width) of the cut and raised portion 12 in the width direction is, for example, 1.0 to 3.0 mm. However, the size of the cut and raised portion 12 is not particularly limited.

  In addition, the shape of the opening 41 when viewed from the upstream side in the airflow direction is not limited to a semicircular shape, and may be, for example, a polygonal shape. Specifically, it may be a triangle as shown in FIG. 8B or a rectangle as shown in FIG. 8C. The number and shape of the cut-and-raised portions 12 can be appropriately adjusted so as to obtain a desired heat transfer performance.

As shown in FIG. 5, when the fin pitch is FP, the cut-and-raised portion 12 has a height H ₁ less than the fin pitch FP. Preferably, the height H ₁ is in a range of 0.4FP <H ₁ <0.6FP. “Height H ₁ ” means the height from the surface (upper surface) of the fin 31. “Fin pitch” means an arrangement interval of the fins 31 when the thickness of the fins 31 is assumed to be zero. If the height H ₁ of the cut-and-raised portion 12 is appropriately adjusted, it is possible to suppress a decrease in the airflow speed when frost adheres to the front edge of the cut and raised portion 12. Further, the cut and raised portion 12 does not interfere with the assembly of the fin tube heat exchanger 1, and the cut and raised portion 12 can be easily formed by pressing or the like.

  In the present embodiment, the plurality of cut-and-raised portions 12 are formed in a line in the width direction. Therefore, the plurality of cut-and-raised portions 12 share the bending line 42 and are translationally symmetric with respect to the width direction. A plurality of through holes 31h are formed at regular intervals in the width direction, and a plurality of (for example, two) cut-and-raised portions 12 are formed for one through hole 31h.

  As shown in FIG. 9, the interval W between the two cut-and-raised portions 12 adjacent to each other in the width direction is adjusted to, for example, (FP) / 2 or more. Preferably, the interval W is in the range of 0.5FP <W <5FP. If the interval W between the cut and raised portions 12 is appropriately adjusted, the effect of suppressing the local frosting on the front edge 31f of the fin 31 is sufficiently obtained as well as the effect of improving the heat transfer performance. Of course, the number of the cut-and-raised portions 12 is not particularly limited.

  In the present embodiment, the cut-and-raised part 12 is located in a specific area indicated by oblique lines. The entire cut-and-raised part 12 may be located in a specific area indicated by hatching, or a part of the cut-and-raised part 12 on the downstream side may protrude from the specific area.

  The specific area indicated by hatching can be determined according to the following rules. As shown in FIG. 9, the diameter of the through hole 31h is φ, and a point on the surface of the fin 31 that is at a distance of 0.8φ in the width direction from the center O of the through hole 31h is a reference point BP. A plane that passes through the reference point BP and is perpendicular to the width direction is defined as a reference plane VL. The intersection of the reference surface VL and the leading edge 31f when the fin 31 is viewed in plan is defined as a leading edge reference point BPF. A region on the surface of the fin 31 surrounded by a line segment connecting the two reference points BP and the two leading edge reference points BPF and adjacent to the through hole 31h is defined as a reference region. Further, an imaginary line on the surface of the fin 31 that is at a distance of 2 mm from the front edge 31f is an upstream reference line LU, and a line that is also at a distance of 3 mm from the front edge 31f is a downstream reference line LD. A region included in the reference region and defined between the upstream reference line LU and the downstream reference line LD is defined as a specific region.

  The reason why the cut and raised portion 12 is provided in the specific area will be described. As known to those skilled in the art, when it is assumed that the temperature of the fin (flat plate) is constant, the local heat transfer coefficient α at an arbitrary position on the surface of the fin can be calculated by the following equation (1). In equation (1), “Pr” is the Prandtl number, “λ” is the thermal conductivity of the fin, “ν” is the kinematic viscosity of the fluid, “U” is the velocity of the fluid, and “x” is from the leading edge of the fin. It represents the distance to the position where the local heat transfer coefficient α should be obtained.

α = 0.332 × Pr ^1/3 × λ × ν ^−1/2 × U × x ^−1/2 (1)

  According to equation (1), the local heat transfer coefficient α depends on the distance from the front edge of the fin. Under the condition that the fluid is air, the fin is aluminum, and the temperature is −5 ° C., the change in the local heat transfer coefficient α with respect to the distance x from the leading edge was calculated based on the formula (1). The results are shown in FIG.

  The graph of FIG. 10 shows that the local heat transfer coefficient α decreases as the distance from the front edge increases. Specifically, the local heat transfer coefficient α gradually decreases from around 3.0 mm from the front edge. This indicates that the thickness of the boundary layer is saturated around 3.0 mm from the front edge. Although the shape of the local heat transfer coefficient α curve also changes according to the fluid velocity U, the tendency of the local heat transfer coefficient α to drop sharply in a region relatively close to the leading edge does not change.

  Note that the results shown in FIG. 10 do not consider the bending of the windward portion 310. However, in consideration of the fact that only the fluid velocity U is the parameter that changes due to the bending of the windward portion 310 and the change in the velocity U based on the bending of the windward portion 310 is small, this calculation result is for the flat portion 312. The fin 31 having the inclined windward portion 310 has a certain validity. The same can be said for the calculation result of the average heat transfer coefficient described with reference to FIG.

  Next, the change in the average heat transfer coefficient of the fin surface with respect to the position of the cut and raised portion 12 when the cut and raised portion 12 is provided on the fin was calculated. However, the bending of the windward portion 310 was not considered.

  In this calculation, the position of the raised portion 12 was changed on a line passing through the center O of the heat transfer tube 21 and parallel to the airflow direction. Depending on the position of the cut and raised part 12, the average value of the local heat transfer coefficient from the front edge to the position 4.5 mm downstream was determined as the “average heat transfer coefficient”. The results are shown in FIG. “The position of the cut and raised portion” means the distance from the front edge of the fin to the upstream end of the cut and raised portion 12. As shown in FIG. 11, the average heat transfer coefficient of the fin becomes maximum when the raised portion 12 is provided at a position where the distance from the front edge is 2.5 mm regardless of the fluid velocity.

  Furthermore, the fin surface temperature was simulated when a finned tube heat exchanger having fins composed only of flat surfaces was used as the evaporator. The results are shown in FIG. The contour map of FIG. 12 indicates that the closer to the heat transfer tube 21, the lower the surface temperature of the fin. As shown in FIG. 12, the surface of the fin exhibits a low temperature in a region (reference region) surrounded by a line segment connecting two reference points BP and two leading edge reference points BPF. That is, the temperature difference between the fin and air is large in the reference region. Therefore, the heat exchange amount can be efficiently increased by improving the heat transfer performance of the reference region.

  Considering the above results, the effect of suppressing frost formation on the front edge 31f and the heat transfer performance of the fin 31 are improved by providing the cut-and-raised portion 12 in a specific region whose distance from the front edge is 2 to 3 mm. Both effects can be achieved. In addition, when the position of the cut-and-raised part 12 is too close to the front edge 31f, there is a problem that it is difficult to form the cut-and-raised part 12 by press working. Pressing can be performed relatively easily on a portion 2 to 3 mm away from the front edge 31f.

  Note that the cut-and-raised portion 12 may be provided in a region other than the specific region. For example, the cut-and-raised part 12 may be provided in the flat part 312.

(Second Embodiment)
A fin tube heat exchanger can be configured by combining the fins described in the first embodiment and other fins. Hereinafter, the same elements as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 13, the finned tube heat exchanger 10 of the present embodiment includes a plurality of fins 3 arranged in parallel at regular intervals to form a flow path for air A, and penetrates these fins 3. A plurality of heat transfer tubes 2.

  As shown in FIGS. 13 and 14, the fin 3 includes a plurality of first fins 31 arranged on the upstream side in the airflow direction and a plurality of first fins so that air A that has passed through the plurality of first fins 31 flows in. A plurality of second fins 32 disposed on the downstream side of the first fin 31. As described in the first embodiment, the first fin 31 includes the windward portion 310, the flat portion 312, and the plurality of cut and raised portions 12. Regarding the airflow direction, the dimensions of the first fins 31 (see FIG. 2) and the dimensions of the second fins 32 may be the same or different. However, it is preferable to be the same in order to enhance the mass production effect.

  As shown in FIG. 13 and FIG. 14, the heat transfer tube 2 includes a plurality of first heat transfer tubes 21 provided on the first fin 31 side so as to be aligned in the width direction, and the second fins 32 also aligned in the width direction. And a plurality of second heat transfer tubes 22 provided on the side. The first heat transfer tubes 21 and the second heat transfer tubes 22 are alternately arranged in the width direction. Similar to the first heat transfer tube 21, the second heat transfer tube 22 is inserted into the through-hole 32 h formed in the second fin 32 and is in close contact with the fin collar 5 b formed by a part of the second fin 32. ing.

  As shown in FIG. 15, a gap 37 having a width G of, for example, 1 to 3 mm in the airflow direction is formed between the downstream end 31e of the first fin 31 and the front edge 32f (upstream end) of the second fin 32. Is formed. The gap 37 has a role of preventing frost from forming between the downstream end 31e of the first fin 31 and the front edge 32f of the second fin 32 and blocking the air passage. That is, the gap 37 can suppress an increase in pressure loss during frost formation. Further, if the gap 37 is present, the front edge 32 f of the second fin 32 is not hidden behind the downstream end face of the first fin 31, so that the amount of heat exchange in the second fin 32 also increases.

  As shown in FIG. 15, in this embodiment, the 2nd fin 32 is a corrugated fin shape | molded so that a mountain and a valley may appear alternately along an airflow direction. Further, the fin pitch FP of the first fin 31 is equal to the fin pitch FP of the second fin 32, and the first fin 31 and the second fin 32 are alternately arranged in the height direction. According to such an arrangement, the front edge 32 f of the second fin 32 faces the air path between two adjacent first fins 31. The air that maintains a high flow velocity hits the front edge 32f of the second fin 32, whereby the heat transfer coefficient at the front edge 32f of the second fin 32 is improved, and the heat exchange amount at the second fin 32 is increased. The first fin 31 provided with the cut-and-raised portion 12 may be used as the downstream fin instead of the corrugated fin.

  The finned tube heat exchanger of the present invention is useful for a heat pump used in an air conditioner, a hot water supply device, a heating device, or the like. In particular, it is useful for an evaporator for evaporating a refrigerant.

1,10 Fin tube heat exchanger 2 Heat transfer tube 3 Fin 5a Fin collar 12 Cut-and-raised part 21 Heat transfer tube, first heat transfer tube 21p Upstream end 22 of heat transfer tube Second heat transfer tube 31 Fin, first fin 31h Through hole 31f Previous Edge 32 Second fin 32f Second fin front edge 41 Opening 41e Opening edge 41p Upstream upstream end 45 First reference line 46 Second reference line 47 Third reference line 310 Upwind 312 Flat part VL Reference plane BP Reference point BPF Leading edge reference point LU Upstream reference line LD Downstream reference line A Air flow

Claims (6)

A plurality of fins arranged in parallel to form an air flow path;
A plurality of fins, including a heat transfer tube through which a medium that exchanges heat with air flows,
Each of the plurality of fins includes (a) a windward portion including a straight leading edge of the fin, and (b) cutting a part of the fin, thereby causing an air flow direction to be higher than an upstream end of the heat transfer tube. A cut and raised portion formed on the upstream side, and (c) a flat portion located rearward of the windward direction with respect to the airflow direction,
The cut and raised portion has an opening that can receive air from the upstream side in the airflow direction and guide the air from the first main surface side to the second main surface side of the fin,
The opening of the cut and raised portion has an opening edge that has a convex shape toward the upstream side in the airflow direction in plan view,
The opening edge includes one end and the other end defined at the same position with respect to the airflow direction;
The windward portion is bent in a direction in which the opening of the cut-and-raised portion is enlarged, and is inclined with respect to the flat portion;
A direction parallel to the front edge is a width direction, a straight line passing through the one end and the other end of the opening edge is a first reference line, a straight line passing through the upstream end of the opening edge parallel to the width direction and the air flow direction When defined as a second reference line, a bending line resulting from the bending of the windward is (i) parallel to the width direction, and (ii) coincides with the first reference line, Alternatively, the finned tube heat exchanger is located in a range downstream from the second reference line and upstream from the first reference line.   The finned tube heat exchanger according to claim 1, wherein the bending line coincides with the first reference line. When the alignment direction of the plurality of fins is defined as a height direction,
The inclination angle of the windward with respect to the flat portion is adjusted so that the front edge is located between the flat portion and the flat portion adjacent to each other with respect to the height direction. The finned tube heat exchanger described in 1.   The finned tube heat exchanger according to claim 3, wherein the inclination angle is in a range of 5 to 30 degrees.   The finned tube heat exchanger according to any one of claims 1 to 4, wherein the opening has a semicircular or polygonal shape when viewed from the upstream side in the airflow direction. A plurality of second fins arranged on the downstream side of the plurality of fins so that air that has passed through the plurality of fins flows;
The second fin is a corrugated fin formed such that peaks and valleys appear alternately along the airflow direction,
The fin pitch of the first fin, which is the fin having the cut-and-raised portion, is equal to the fin pitch of the second fin,
When the arrangement direction of the plurality of first fins is defined as a height direction, the first fins and the second fins are alternately arranged with respect to the height direction. The finned tube heat exchanger according to item 1.

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