WO2013054508A1

WO2013054508A1 - Finned tube heat exchanger

Info

Publication number: WO2013054508A1
Application number: PCT/JP2012/006469
Authority: WO
Inventors: 健二名越; 雅也本間; 岡市　敦雄; 長谷川　寛; 周平大坪
Original assignee: パナソニック株式会社
Priority date: 2011-10-11
Filing date: 2012-10-10
Publication date: 2013-04-18
Also published as: CN103890527A; EP2767791A4; EP2767791A1; JP5958771B2; JPWO2013054508A1; EP2767791B1; CN103890527B

Abstract

This finned tube heat exchanger (100) is provided with a fin (31) and a heat transfer tube (21). The fin (31) has a flat section (35), a first inclined section (36), and a second inclined section (38). The length of the fin (31) in the direction of airflow is defined as S1, the distance between heat transfer tube (21) centers in the direction of levels as S2, the diameter of the flat section (35) as D1, the plane passing through the upstream end and downstream end of the fin (31) in the direction of airflow as a reference plane (H1), the angle formed by the reference plane (H1) and the first inclined section (36) as θ1, the angle formed by the reference plane (H1) and the second inclined section (38) as θ2, and the distance from the reference plane (H1) to the flat section (35) as α. The finned tube heat exchanger (100) satisfies the relationship tan^-1{(S1·tanθ1±2α)/(S2-D1)} ≤ θ2 < 80°-θ1.

Description

Finned tube heat exchanger

The present invention relates to a finned tube heat exchanger.

The finned tube heat exchanger is composed of a plurality of fins arranged at predetermined intervals and a heat transfer tube penetrating the plurality of fins. The air flows between the fins and exchanges heat with the fluid in the heat transfer tubes.

9A to 9D are respectively a plan view of fins used in a conventional fin tube heat exchanger, a sectional view taken along line IXB-IXB, a sectional view taken along line IXC-IXC, and a line taken along line IXD-IXD. FIG. The fin 10 is formed so that the peaks 4 and the valleys 6 appear alternately in the airflow direction. Such fins are commonly referred to as “corrugated fins”. According to the corrugated fin, not only the effect of increasing the heat transfer area but also the effect of thinning the temperature boundary layer by meandering the air flow 3 can be obtained.

Also, as shown in FIGS. 10A to 10C, a technique for improving heat transfer performance by providing a corrugated fin with a cut and raised is also known (Patent Document 1). Cut and raised

portions

41a, 41b, 41c and 41d are provided on the fin

inclined surfaces

42a, 42b, 42c and 42d of the fin 1. The heights H1, H2, H3, and H4 of the cut-and-raised

portions

41a, 41b, 41c, and 41d are 1/5 · Fp ≦ (H1, H2, H3, H4) ≦ 1 when the distance between adjacent fins 1 is Fp. / 3 · Fp is satisfied.

Patent Document 1 also describes another fin configured to reduce the ventilation resistance during the frosting operation as much as possible. As shown in FIGS. 11A to 11C, the fin

inclined surfaces

12a and 12b of the fin 1 are provided with cut-and-raised portions 11a and 11b that satisfy the above-described relationship. Since the number of times of bending of the fin 1 is small, the inclination angles of the fin

inclined surfaces

12a and 12b are relatively gentle.

Japanese Patent Laid-Open No. 11-125495

However, even if the cut-up is sufficiently low, the cross-sectional area of the flow path is locally reduced by 20% or more during the frosting operation. For this reason, when the cut-and-raise is provided, even if the number of bendings is limited to one and the inclination angle is made gentle, a significant increase in ventilation resistance is inevitable. In order to reduce the ventilation resistance of the fin 1 shown in FIGS. 11A to 11C to a level equivalent to that of the fin 10 shown in FIGS. 9A to 9D, it is necessary to make the inclination angle of the fin 1 as close as possible to 0 °.

This invention aims at providing the finned-tube heat exchanger which has the outstanding basic performance irrespective of the time of frost operation and non-frost operation.

That is, this disclosure
A plurality of fins arranged in parallel to form a gas flow path;
A heat transfer tube configured to pass through the plurality of fins and to have a medium that exchanges heat with the gas flow therein;
The fin is a corrugated fin formed so that a peak portion appears only at one place in the airflow direction, and a plurality of through holes in which the heat transfer tubes are fitted, and a flat portion formed around the through holes And a first inclined part that is inclined with respect to the airflow direction so as to form the mountain part, and a second inclined part that connects the flat part and the first inclined part,
The plurality of through holes are formed along a step direction perpendicular to both the direction of arrangement of the plurality of fins and the airflow direction,
The length of the fin in the airflow direction is S1, the distance between the centers of the heat transfer tubes in the step direction is S2, the diameter of the flat portion is D1, and a plane passing through the upstream end and the downstream end of the fin in the airflow direction Is defined as a reference plane, an angle formed by the reference plane and the first inclined portion is defined as θ1, an angle formed between the reference plane and the second inclined portion is defined as θ2, and a distance from the reference plane to the flat portion is defined as α. When
Provided is a finned tube heat exchanger that satisfies the relationship of tan ⁻¹ {(S1 · tan θ1 ± 2α) / (S2-D1)} ≦ θ2 <80 ° -θ1.

According to the above configuration, it is possible to provide a finned tube heat exchanger in which the ventilation resistance is sufficiently suppressed and the heat exchange amount (heat exchange capability) is high.

The perspective view of the finned-tube heat exchanger which concerns on one Embodiment of this invention. The top view of the fin used for the fin tube heat exchanger of FIG. Sectional drawing along the IIB-IIB line of the fin shown in FIG. 2A Sectional drawing along the IIC-IIC line of the fin shown in FIG. 2A Sectional view along the IID-IID line of the fin shown in Fig. 2A Graph showing the relationship between the second inclination angle θ2 and the surface area of the fin Graph showing the relationship between the second inclination angle θ2 and the surface area ratio (surface area of V-shaped corrugated fin / surface area of M-shaped corrugated fin) Schematic which shows the state which the adjacent 2nd inclination part contacted. Schematic showing the calculation method of the threshold angle θ2L Schematic showing how to calculate the maximum value αmax of distance α The top view which shows the part which has a high heat transfer rate in the fin shown to FIG. 2A The top view which shows the part which has a high heat transfer rate in the conventional fin Sectional view showing the analysis area of air flow Schematic showing the air flow when the sum of the first inclination angle θ1 and the second inclination angle θ2 is 36 ° Schematic showing the air flow when the sum of the first inclination angle θ1 and the second inclination angle θ2 is 66 ° Schematic showing the air flow when the sum of the first inclination angle θ1 and the second inclination angle θ2 is 76 ° Schematic showing the air flow when the sum of the first inclination angle θ1 and the second inclination angle θ2 is 86 ° Schematic showing the flow of air when the sum of the first inclination angle θ1 and the second inclination angle θ2 is 96 ° The graph which shows the relationship between 2nd inclination | tilt angle (theta) 2 and the performance (heat exchange amount and pressure loss) of a finned-tube heat exchanger. The top view of the fin concerning a 2nd embodiment Sectional drawing along the VIIIB-VIIIB line of the fin shown in FIG. 8A Sectional drawing along the VIIIC-VIIIC line of the fin shown in FIG. 8A Sectional drawing along the VIIID-VIIID line of the fin shown in FIG. 8A Schematic showing the calculation method of the threshold angle θ2L Top view of fins used in conventional fin tube heat exchanger Sectional drawing along the IXB-IXB line of the fin shown in FIG. 9A Sectional drawing along the IXC-IXC line of the fin shown in FIG. 9A Sectional drawing along the IXD-IXD line of the fin shown in FIG. 9A Top view of another fin used in a conventional fin tube heat exchanger Sectional drawing along the XB-XB line of the fin shown in FIG. 10A Sectional drawing along the XC-XC line of the fin shown in FIG. 10A Top view of yet another fin used in a conventional fin tube heat exchanger Sectional drawing along the XIB-XIB line of the fin shown in FIG. 11A Sectional drawing along the XIC-XIC line of the fin shown in FIG. 11A

The first aspect of the present disclosure is:
A plurality of fins arranged in parallel to form a gas flow path;
A heat transfer tube configured to pass through the plurality of fins and to have a medium that exchanges heat with the gas flow therein;
The fin is a corrugated fin formed so that a peak portion appears only at one place in the airflow direction, and a plurality of through holes in which the heat transfer tubes are fitted, and a flat portion formed around the through holes And a first inclined part that is inclined with respect to the airflow direction so as to form the mountain part, and a second inclined part that connects the flat part and the first inclined part,
The plurality of through holes are formed along a step direction perpendicular to both the direction of the plurality of fins and the airflow direction,
The length of the fin in the airflow direction is S1, the distance between the centers of the heat transfer tubes in the step direction is S2, the diameter of the flat portion is D1, and the plane passing through the upstream end and the downstream end of the fin in the airflow direction Is defined as a reference plane, an angle between the reference plane and the first inclined portion is defined as θ1, an angle formed between the reference plane and the second inclined portion is defined as θ2, and a distance from the reference plane to the flat portion is defined as α. When
Provided is a finned tube heat exchanger that satisfies the relationship of tan ⁻¹ {(S1 · tan θ1 ± 2α) / (S2-D1)} ≦ θ2 <80 ° −θ1.

In the second aspect of the present disclosure, in addition to the first aspect, the angle θ2 satisfies a relationship of tan ⁻¹ {(S1 · tan θ1 ± 2α) / (S2-D1)} ≦ θ2 <70 ° −θ1. A finned tube heat exchanger is provided.

In a third aspect of the present disclosure, in addition to the first or second aspect, the fin is configured to prohibit the flow of the gas from the front side to the back side of the fin in other regions excluding the plurality of through holes. Provided is a finned tube heat exchanger.

The fourth aspect of the present disclosure is:
A plurality of fins arranged in parallel to form a gas flow path;
A heat transfer tube configured to pass through the plurality of fins and to have a medium that exchanges heat with the gas flow therein;
The fin is a corrugated fin formed so that a peak portion appears only at one place in the airflow direction, and is closely attached to the heat transfer tube around the through hole in which the heat transfer tube is fitted. A cylindrical fin collar, a first inclined portion that is inclined with respect to the air flow direction so as to form the peak portion, and a second connecting the fin collar and the first inclined portion. An inclined portion,
The plurality of through holes are formed along a step direction perpendicular to both the direction of arrangement of the plurality of fins and the airflow direction,
The length of the fin in the airflow direction is S1, the distance between the centers of the heat transfer tubes in the step direction is S2, the outer diameter of the fin collar is D2, and the upstream end and the downstream end of the fin in the airflow direction are passed. When a plane is defined as a reference plane, an angle formed between the reference plane and the first inclined portion is defined as θ1, and an angle formed between the reference plane and the second inclined portion is defined as θ2.
Provided is a finned tube heat exchanger that satisfies the relationship of tan ⁻¹ {(S1 · tanθ1) / (S2-D2)} ≦ θ2 <80 ° −θ1.

In the fifth aspect of the present disclosure, in addition to the fourth aspect, the angle θ2 satisfies the relationship of tan ⁻¹ {(S1 · tanθ1) / (S2-D2)} ≦ θ2 <70 ° −θ1. Provide heat exchanger.

In a sixth aspect of the present disclosure, in addition to the fourth or fifth aspect, the fins prohibit the flow of the gas from the front side to the back side of the fins in other regions excluding the plurality of through holes. Provided is a finned tube heat exchanger.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited by the following embodiment.

(First embodiment)
As shown in FIG. 1, the finned tube heat exchanger 100 of the present embodiment passes through a plurality of fins 31 arranged in parallel to form a flow path of air A (gas) and these fins 31. And a heat transfer tube 21. The finned tube heat exchanger 100 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 or hydrofluorocarbon. The heat transfer tube 21 may be connected to one or may be divided into a plurality.

The fin 31 has a front edge 30a and a rear edge 30b. The front edge 30a and the rear edge 30b are each linear. In the present embodiment, the fins 31 have a symmetrical structure with respect to the center of the heat transfer tube 21. Therefore, it is not necessary to consider the direction of the fins 31 when assembling the heat exchanger 100.

In this specification, the arrangement direction of the fins 31 is defined as the height direction, the direction parallel to the front edge 30a is defined as the step direction, and the height direction and the direction perpendicular to the step direction are defined as the airflow direction (the flow direction of the air A). In other words, the step direction is a direction perpendicular to both the height direction and the airflow direction. The airflow direction is perpendicular to the longitudinal direction of the fins 31. The airflow direction, the height direction, and the step direction correspond to the X direction, the Y direction, and the Z direction, respectively.

As shown in FIGS. 2A to 2D, the fin 31 typically has a rectangular and flat plate shape. The longitudinal direction of the fin 31 coincides with the step direction. In the present embodiment, the fins 31 are arranged at a constant interval (fin pitch FP). However, the interval between the two fins 31 adjacent to each other in the height direction is not necessarily constant, and may be different. The fin pitch FP is adjusted to a range of 1.0 to 1.5 mm, for example. As shown in FIG. 2B, the fin pitch FP is represented by the distance between two adjacent fins 31.

The constant width portion including the front edge 30a and the constant width portion including the rear edge 30b are parallel to the airflow direction. However, these portions are portions used for fixing the fins 31 to the mold during molding, and do not greatly affect the performance of the fins 31.

As the material of the fin 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. The surface of the fin 31 may be subjected to hydrophilic treatment such as boehmite treatment or application of a hydrophilic paint. It is also possible to perform a water repellent treatment instead of the hydrophilic treatment.

In the fin 31, a plurality of through holes 37h are formed in a row and at equal intervals along the step direction. Straight lines passing through the centers of the plurality of through holes 37h are parallel to the step direction. The heat transfer tube 21 is fitted in each of the plurality of through holes 37h. A cylindrical fin collar 37 is formed by a part of the fin 31 around the through hole 37h, and the fin collar 37 and the heat transfer tube 21 are in close contact with each other. The diameter of the through hole 37h is, for example, 1 to 20 mm, and may be 4 mm or less. The diameter of the through-hole 37 h matches the outer diameter of the heat transfer tube 21. The center distance (pipe pitch) between two through holes 37h adjacent to each other in the step direction is, for example, 2 to 3 times the diameter of the through hole 37h. The length of the fin 31 in the airflow direction is, for example, 15 to 25 mm.

As shown in FIGS. 2A and 2B, the fin 31 is formed so that the mountain portion 34 appears only in one place in the airflow direction. The ridge line of the mountain portion 34 is parallel to the step direction. That is, the fin 31 is a fin called a corrugated fin. If a portion projecting in the same direction as the projecting direction of the fin collar 37 is defined as a “mountain portion 34”, in the present embodiment, the fin 31 has only one mountain portion 34 in the airflow direction. The front edge 30a and the rear edge 30b correspond to the valleys. In the airflow direction, the position of the mountain portion 34 coincides with the center position of the heat transfer tube 21.

In the present embodiment, the fin 31 is configured to prohibit the flow of air A from the front side (upper surface side) to the back side (lower surface side) of the fin 31 in other regions excluding the plurality of through holes 37h. Yes. Thus, it is desirable that no opening other than the through hole 37h is provided in the fin 31. If there is no opening, there is no problem of clogging due to frost formation, which is advantageous in terms of pressure loss. Note that “no opening is provided” means that no slit, louver or the like is provided, that is, no hole penetrating the fin is provided.

The fin 31 further includes a flat portion 35, a first inclined portion 36, and a second inclined portion 38. The flat portion 35 is a portion adjacent to the fin collar 37 and an annular portion formed around the through hole 37h. The surface of the flat part 35 is parallel to the airflow direction and perpendicular to the height direction. The first inclined portion 36 is a portion inclined with respect to the airflow direction so as to form the mountain portion 34. The first inclined portion 36 occupies the widest area in the fin 31. The surface of the first inclined portion 38 is flat. The first inclined portions 36 are located on the left and right sides of a reference line that is parallel to the step direction and passes through the center of the heat transfer tube 21. That is, the peak portion 34 is formed by the first slope portion 36 on the windward side and the first slope portion 36 on the leeward side. The second inclined portion 38 is a portion that smoothly connects the flat portion 35 and the first inclined portion 36 so as to eliminate the difference in height between the flat portion 35 and the first inclined portion 36. . The surface of the second inclined portion 38 is a gently curved surface. The flat portion 35 and the second inclined portion 39 form a concave portion around the fin collar 37 and the through hole 37h.

Note that an appropriate radius (for example, R0.5 mm to R2.0 mm) may be given to the boundary portion between the first inclined portion 36 and the second inclined portion 38. Similarly, an appropriate radius (for example, R0.5 mm to R2.0 mm) may be applied to the boundary portion between the peak portion 34 and the second inclined portion 38. Such a round improves the drainage of the fin 31.

As shown in FIGS. 2A to 2D, the length of the fin 31 in the airflow direction is defined as S1. The center-to-center distance (tube pitch) of the heat transfer tubes 21 in the step direction is defined as S2. The diameter of the flat part 35 is defined as D1. A plane passing through the upstream end and the downstream end of the fin 31 in the airflow direction is defined as a reference plane H1. The upstream end and the downstream end of the fin 31 correspond to the

leading edges

30a and 30b, respectively. An angle formed by the reference plane H1 and the first inclined portion 36 is defined as θ1. An angle formed by the reference plane H1 and the second inclined portion 38 is defined as θ2. The angle θ <b> 1 is an acute angle side among the angles formed by the reference plane H <b> 1 and the first inclined portion 36. Similarly, the angle θ <b> 2 is an acute angle side angle among the angles formed by the reference plane H <b> 1 and the second inclined portion 38. In this specification, the angle θ1 and the angle θ2 are respectively referred to as “first inclination angle θ1” and “second inclination angle θ2”. Further, the distance from the reference plane H1 to the flat portion 35 is defined as α. In the embodiment shown in FIGS. 2A-2D, the distance α is zero. That is, in the height direction, the position of the flat portion 35, the position of the front edge 30a, and the position of the rear edge 30b coincide. At this time, the reference plane H1 coincides with a plane including the surface of the flat portion 35.

As described above, when S1, S2, D1, θ1, θ2, and α are defined, the finned tube heat exchanger 100 satisfies the following formula (1).

tan ^-1 {(S1 ・ tanθ1 ± 2α) / (S2-D1)} ≦ θ2 <80 ° -θ1 (1)

In the height direction, the position of the flat portion 35 may be different from the position of the front edge 30a and the position of the rear edge 30b. Specifically, when the flat portion 35 is located closer to the ridgeline of the peak portion 34 than the reference plane H1, the left side of the equation (1) is expressed as tan ⁻¹ {(S1 · tanθ1-2α) / (S2− D1)}. If the flat portion 35 is located closer to the ridgeline of the mountain portion 34 than the reference plane H1, the angle formed by the first inclined portion 36 and the second inclined portion 38 is increased, so that the surface area of the fin 31 is reduced. However, pressure loss is reduced. That is, the fin 31 with a low pressure loss is obtained.

On the other hand, when the flat part 35 is farther from the ridgeline of the peak part 34 than the reference plane H1, the left side of the expression (1) is tan ⁻¹ {(S1 · tanθ1 + 2α) / (S2-D1)}. . When the flat portion 35 is farther from the ridge line of the peak portion 34 than the reference plane H1, the angle formed by the first inclined portion 36 and the second inclined portion 38 is reduced, so that the pressure loss increases, but the fin 31 Increases surface area. Moreover, the effect of reducing the dead water area | region which generate | occur | produces behind the heat exchanger tube 21 can also be anticipated by the angle (theta) 2 of the 2nd inclination part 38 increasing. That is, the fin 31 with high heat exchange capability is obtained.

In addition, although the 2nd inclination part 38 is a curved surface as a whole, 2nd inclination angle (theta) 2 can be specified in the cross section shown to FIG. 2C or FIG. 2D. The cross section of FIG. 2C is a cross section observed when the fins 31 are cut along a plane perpendicular to the step direction and passing through the center of the heat transfer tube 21. 2D is a cross section observed when the fins 31 are cut along a plane perpendicular to the flow direction and passing through the center of the heat transfer tube.

Hereinafter, the technical significance of Equation (1) will be described in detail.

(About the lower limit value of the second inclination angle θ2)
Assuming that the length in the airflow direction is constant, the surface area of the corrugated fin is necessarily larger than the surface area of the flat fin (unbent fin). Further, when the first inclination angle θ1 is constant, the surface area of the corrugated fin (V-shaped corrugated fin) in which the number of bendings is limited to one is the corrugated fin (M-shaped corrugated fin) having two or more times of bending. It is wider than the surface area. This reason can be understood by comparing the cross section of the fin 31 of this embodiment with the cross section of the conventional fin 10.

As can be understood by comparing FIG. 2B and FIG. 9B, the length of the cross-sectional contour shown in FIG. 2B is equal to the length of the cross-sectional contour shown in FIG. 9B. Since the cross section shown in FIG. 2C corresponds to the cross section shown in FIG. 9C, the lengths of both contours are equal. On the other hand, as can be understood by comparing FIG. 2D and FIG. 9D, the length of the cross-sectional contour shown in FIG. 2D exceeds the length of the cross-sectional contour shown in FIG. 9D. This is because according to the fin 31 of the present embodiment, the second inclined portion 38 having the second inclination angle θ2 is included in the cross section shown in FIG. 2D. According to the conventional fin 10, the inclined portion 8 is not included in the cross section shown in FIG. 9D, and only the flat portion 5 and the valley portion 6 are included. Due to the increase of the surface area based on the second inclined portion 38, the surface area of the fin 31 of the present embodiment exceeds the surface area of the conventional two-folded fin 10.

In order to prove the above fact, the surface area of the V-shaped corrugated fin and the surface area of the M-shaped corrugated fin were respectively calculated while changing the second inclination angle θ2. The results are shown in FIGS. 3A and 3B. Other conditions used for the calculation are as follows.

・ Fin length S1 = 18.9mm
・ Distance between heat transfer tube centers S2 = 18.3mm
-Diameter of flat part D1 = 11 mm
・ First tilt angle θ1 = 16 °
・ Fin pitch FP = 1.3mm

As shown in FIG. 3A, the surface area of the fin increases as the second inclination angle θ2 increases, regardless of the number of bendings. However, the increase rate of the surface area of the V-shaped corrugated fin with respect to the second inclination angle θ2 exceeds that of the M-shaped corrugated fin. As shown in FIG. 3B, when the second inclination angle θ2 is close to 0 °, the surface area of the V-shaped corrugated fin substantially matches the surface area of the M-shaped corrugated fin. That is, the surface area ratio is about 100%. The larger the second tilt angle θ2, the greater the difference in surface area.

Analyzing in detail, when the second inclination angle θ2 decreases from 80 ° to 40 °, the slope of the curve representing the surface area ratio gradually becomes gentle. However, the slope of the curve suddenly increases near the point A shown in FIG. 3B. As shown in FIG. 4A, the threshold angle θ2L corresponding to the point A is an angle at which the second inclined portions 38 adjacent to each other in the step direction come into contact with each other in the V-shaped corrugated fin. In the region where the second inclination angle θ2 is smaller than the threshold angle θ2L, the erosion of the adjacent second inclined portions 38 proceeds, so the reduction in the surface area ratio is accelerated. Here, the threshold angle θ2L is expressed by the following formula (2) using the length S1 of the fin 31, the center-to-center distance S2 of the heat transfer tube 21, the diameter D1 of the flat portion 35, the first inclination angle θ1, and the distance α. The

θ2L = tan ^-1 {(S1 ・ tanθ1 ± 2α) / (S2-D1)} (2)

The threshold angle θ2L is an angle calculated by the following method. As shown in FIG. 4B, the height of the peak portion 34 is represented by (S1 / 2) · tan θ1 ± α. The tangent of the second inclination angle θ2 (= threshold angle θ2L) when the adjacent second inclined portions 38 just contact each other is {(S1 / 2) · tanθ1 ± α} / {(S2-D1) / 2}. expressed. Therefore, the threshold angle θ2L can be expressed by Expression (2).

Further, when the second inclination angle θ2 is less than the threshold angle θ2L, the adjacent second inclined portions 38 are eroded and the mountain portions 34 disappear, and the contact portions between the second inclined portions 38 are substantially parallel to each other. It becomes. When passing over a horizontal plane at the contact portion, the air is decelerated, causing a decrease in heat transfer coefficient. For this reason, when the second inclination angle θ2 is less than the threshold angle θ2L, a decrease in heat exchange capability due to a decrease in heat transfer coefficient is added to a decrease in heat exchange capability due to a rapid decrease in surface area. As a result, the heat exchange capacity of the finned tube heat exchanger is significantly reduced.

Therefore, in order to increase the heat exchange capability of the finned tube heat exchanger, it is important that the second inclination angle θ2 is equal to or greater than the threshold angle θ2L.

In addition, the improvement of an average heat transfer rate is mentioned as another reason which can expect improvement of a heat exchange capability by using the fin 31 which has only one peak part 34. FIG. FIG. 5A shows the results obtained by numerical analysis for a V-shaped corrugated fin having only one peak. FIG. 5B shows the results obtained by numerical analysis for an M-shaped corrugated fin having two peaks. A portion having a high heat flux (heat exchange amount) is indicated by a thick line. As shown to FIG. 5A, the heat flux in the front edge 30a and the peak part 34 is very high. Similarly, as shown in FIG. 5B, the heat flux at the leading edge 9 and the peak 4 is extremely high. However, when the total length of the thick line is compared, the total length of the thick line shown in FIG. 5A exceeds the total length of the thick line shown in FIG. 5B. That is, the V-shaped corrugated fin can ensure a longer region of high heat flux. Therefore, the fin 31 of this embodiment is advantageous to the conventional fin 10 also in terms of heat transfer coefficient.

(About the upper limit value of the second inclination angle θ2)
As a disadvantage associated with the increase in the second inclination angle θ2, “flow separation” can be cited. As shown by the broken line D in FIG. 6A, in the finned tube heat exchanger 100, the section where the meandering angle of the air A is the largest exists near the boundary between the first inclined portion 36 and the second inclined portion 38. The meandering angle of the airflow in the section indicated by the broken line D can be represented by the sum (θ1 + θ2) of the first inclination angle θ1 and the second inclination angle θ2.

In order to investigate the influence of the meander angle (θ1 + θ2) on the airflow, an airflow analysis was performed using a corrugated fin model having the conditions used in the calculation of the surface area. Specifically, while changing the meandering angle (θ1 + θ2), the size of the peeling area in the meandering portion and the airflow direction in the peeling area were examined. The front wind speed was 1.3 m / sec. Representative results are shown in FIGS. 6B-6F.

As shown in FIG. 6B, when the meandering angle (θ1 + θ2) was 36 °, a peeling region was generated in the vicinity of the outer peripheral wall of the meandering portion. However, the thickness was very thin, and the internal flow was flowing forward along the main stream. As shown in FIG. 6C, when the meandering angle (θ1 + θ2) was 66 °, a peeling region was generated in the vicinity of the outer peripheral wall of the meandering portion. The exfoliation region was relatively thick, but the flow in the exfoliation region was basically forward. There was also a slight flow showing a vector different from the mainstream. When the meandering angle (θ1 + θ2) was 76 °, there was a slight flow showing a vector different from the mainstream, similar to when the meandering angle (θ1 + θ2) was 66 °. When the meander angle (θ1 + θ2) was 86 °, the flow showing a vector different from the main flow increased clearly. When the meandering angle (θ1 + θ2) was 96 °, the vicinity of the outer peripheral wall of the meandering portion was covered with a wide range and a very thick peeling region. Further, most of the flow in the separation region is a vortex flow including a vector in the opposite direction to the main flow. The vortex flow in the separation region not only causes a significant increase in ventilation resistance, but also reduces the effective heat transfer area. That is, if the meander angle (θ1 + θ2) is too large, an increase in heat exchange amount due to an increase in surface area may be offset. Therefore, the meandering angle (θ1 + θ2) is desirably in a range that does not cause a significant increase in ventilation resistance.

In the above analysis results, when the meander angle (θ1 + θ2) was 76 °, there was a slight flow showing a vector different from the mainstream. On the other hand, when the meander angle (θ1 + θ2) is 86 °, the flow showing a vector different from the main flow clearly increased. Therefore, by limiting the meandering angle (θ1 + θ2) to less than 80 °, preferably less than 70 °, generation of vortex flow in the separation region can be suppressed, and consequently, ventilation resistance can be suppressed.

From the above results, a suitable range of the second inclination angle θ2 is expressed by the above-described formula (1).

The first inclination angle θ1 is not particularly limited, but is preferably less than 40 °. When 1st inclination-angle (theta) 1 is 40 degrees or more, the bending angle of the peak part 34 will be 80 degrees or more. In this case, a thick separation region is generated in the peak portion 34, and there is a possibility that a vortex flow including a vector in the opposite direction to the main flow is generated. Therefore, the first inclination angle θ1 is preferably less than 40 °. The lower limit of the first inclination angle θ1 is not particularly limited. In the corrugated fin, the first inclination angle θ1 is larger than 0 °.

FIG. 7 is a graph showing the relationship between the second inclination angle θ2 and the performance (heat exchange amount and pressure loss) of the finned tube heat exchanger. The rate of change of the heat exchange amount greatly changes with the threshold angle θ2L as a boundary. That is, when the second inclination angle θ2 is equal to or greater than the threshold angle θ2L, a sufficient heat exchange amount can be ensured. On the other hand, the rate of change in ventilation resistance varies greatly with the angle θ2H (= 80 ° −θ1 or 70 ° −θ1) as a boundary. That is, when the second inclination angle θ2 is smaller than the angle θ2H, the ventilation resistance can be sufficiently suppressed.

Investigate the upper and lower limits of the distance α in equation (1). As can be understood from FIG. 4B, when the flat portion 35 gradually approaches the ridgeline of the peak portion 34, the distance (S1 / 2) from the flat portion 35 to the ridgeline of the peak portion 34, and the value of α in tan θ1-α gradually increases. It increases to. In order to bring the flat portion 35 closer to the ridgeline of the mountain portion 34, it is necessary to provide a step between the flat portion 35 and the first inclined portion 36 at a certain time. Such a step significantly hinders the air flow around the flat portion 35 and greatly increases the ventilation resistance. The maximum value αmax of α that does not cause such a step is represented by tan θ1 · (S1-D1) / 2 as can be understood from FIG. 4C.

On the other hand, when the flat portion 35 gradually moves away from the ridge line of the mountain portion 34, the value of α at the distance (S1 / 2) tan θ1 + α from the flat portion 35 to the ridge line of the mountain portion 34 gradually increases. In this case, as can be understood from Expression (2), the threshold angle θ2L increases as the value of α increases. However, a new step does not appear due to the fin structure. Accordingly, the value of α is not limited as long as it is within a range where no significant vortex flow is generated in the separation region (θ2 <80 ° −θ1 or θ2 <70 ° −θ1).

(Second Embodiment)
As shown in FIGS. 8A to 8D, the fin 41 of the present embodiment has the same structure as the fin 31 of the first embodiment, except that the flat portion 35 is not provided around the fin collar 37. Elements common to the fins 41 of the present embodiment and the fins 31 of the first embodiment are assigned the same reference numerals, and descriptions thereof are omitted.

The fin 41 has a fin collar 37, a first inclined portion 36, and a second inclined portion 38. The fin collar 37 is a cylindrical portion that is in close contact with the heat transfer tube 21 around the through hole 37h. The second inclined portion 38 is a portion connecting the fin collar 37 and the first inclined portion 36. When the outer diameter of the fin collar 37 is defined as D2, the fin 41 (specifically, the fin tube heat exchanger 100) satisfies the following formula (3).

tan ^-1 {(S1 ・ tanθ1) / (S2-D2)} ≦ θ2 <80 ° -θ1 (3)

In the present embodiment, the position of the lower end of the fin collar 37 coincides with the position of the reference plane H1, and does not vary like the flat portion 35 of the first embodiment. As shown in FIG. 8E, the height of the peak portion 34 is represented by (S1 · tan θ1) / 2. Further, since the fin 41 does not have the flat portion 35, when the second inclined portions 38 adjacent to each other in the step direction come into contact with each other, the length of the second inclined portion 38 in the step direction is (S2-D2) / 2. It is represented by Furthermore, as estimated from the results of the airflow analysis shown in FIGS. 6A to 6F, the presence or absence of the flat portion 35 is considered not to have a large effect on the increase or decrease in the ventilation resistance. For the above reason, all the explanations regarding the formula (1) can be applied to the formula (3). When the expression (3) is satisfied, the finned tube heat exchanger 100 including the fins 41 has a low ventilation resistance and a high heat exchange capacity. As in the first embodiment, the second inclination angle θ2 is preferably less than (70 ° −θ1).

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.

Claims

A plurality of fins arranged in parallel to form a gas flow path;
A heat transfer tube configured to pass through the plurality of fins and to have a medium that exchanges heat with the gas flow therein;
The fin is a corrugated fin formed so that a peak portion appears only at one place in the airflow direction, and a plurality of through holes in which the heat transfer tubes are fitted, and a flat portion formed around the through holes And a first inclined part that is inclined with respect to the airflow direction so as to form the mountain part, and a second inclined part that connects the flat part and the first inclined part,
The plurality of through holes are formed along a step direction perpendicular to both the direction of arrangement of the plurality of fins and the airflow direction,
The length of the fin in the airflow direction is S1, the distance between the centers of the heat transfer tubes in the step direction is S2, the diameter of the flat portion is D1, and a plane passing through the upstream end and the downstream end of the fin in the airflow direction Is defined as a reference plane, an angle formed by the reference plane and the first inclined portion is defined as θ1, an angle formed between the reference plane and the second inclined portion is defined as θ2, and a distance from the reference plane to the flat portion is defined as α. When
A finned tube heat exchanger that satisfies the relationship of tan −1 {(S1 · tan θ1 ± 2α) / (S2-D1)} ≦ θ2 <80 ° -θ1.
The fin tube heat exchanger according to claim 1, wherein the angle θ2 satisfies a relationship of tan −1 {(S1 · tan θ1 ± 2α) / (S2-D1)} ≦ θ2 <70 ° −θ1.
The fin tube heat exchanger according to claim 1, wherein the fin is configured to prohibit the flow of the gas from the front side to the back side of the fin in the other region excluding the plurality of through holes.
A plurality of fins arranged in parallel to form a gas flow path;
A heat transfer tube configured to pass through the plurality of fins and to have a medium that exchanges heat with the gas flow therein;
The fin is a corrugated fin formed so that a peak portion appears only at one place in the airflow direction, and is closely attached to the heat transfer tube around the through hole in which the heat transfer tube is fitted. A cylindrical fin collar, a first inclined portion that is inclined with respect to the air flow direction so as to form the peak portion, and a second connecting the fin collar and the first inclined portion. An inclined portion,
The plurality of through holes are formed along a step direction perpendicular to both the direction of arrangement of the plurality of fins and the airflow direction,
The length of the fin in the airflow direction is S1, the distance between the centers of the heat transfer tubes in the step direction is S2, the outer diameter of the fin collar is D2, and the upstream end and the downstream end of the fin in the airflow direction are passed. When a plane is defined as a reference plane, an angle formed between the reference plane and the first inclined portion is defined as θ1, and an angle formed between the reference plane and the second inclined portion is defined as θ2.
A finned tube heat exchanger that satisfies the relationship of tan -1 {(S1 · tanθ1) / (S2-D2)} ≦ θ2 <80 ° -θ1.
The fin tube heat exchanger according to claim 4, wherein the angle θ2 satisfies a relationship of tan −1 {(S1 · tan θ1) / (S2-D2)} ≦ θ2 <70 ° −θ1.
The fin tube heat exchanger according to claim 4, wherein the fin is configured to prohibit the flow of the gas from the front side to the back side of the fin in other regions excluding the plurality of through holes.