JPH11337284A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a heat exchanging performance of a heat exchanger constituted by incorporating a heat transfer surface by devising a structure of a protrusion provided on the surface. SOLUTION: A plurality of heat transfer expediting parts 4 each made of a pair of ribs 5 are provided on a heat transfer surface. The pair of the ribs 5 are disposed to be deviated at an interval of 0.5 to 1.5 of its pitch from one another in a flowing direction of a fluid flowing along the surface. Similarly, the pair of the ribs 5 are inclined in opposite directions via a centerline β of the parts 4 parallel to the flowing direction of the fluid, and an attack angle θof the angle of inclination is set to 15 to 75 degrees.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The heat exchanger according to the present invention comprises:
It can be used as a heat exchanger such as a radiator or a condenser when performing heat exchange between various fluids.

[0002]

2. Description of the Related Art A variety of heat exchangers are widely used to cool a fluid flowing in a heat transfer tube by air, or to cool or heat air by a fluid flowing in the heat transfer tube. . In addition, when performing heat exchange between a fluid such as a refrigerant flowing in the heat transfer tube and a fluid such as air flowing outside the heat transfer tube by various heat exchangers, the heat transfer fins and the like inside and outside the heat transfer tube. Destroying the boundary layer, these heat transfer tubes and heat transfer fins,
It has been widely practiced to efficiently perform heat exchange with the fluid such as the refrigerant or air.

For example, Japanese Patent Application Laid-Open No. 63-17393 discloses that various shapes such as hemispherical and rectangular projections (transfers) projecting toward the inside of the flat heat transfer tube are provided on the inner surface of the flat heat transfer tube as a heat transfer surface. A technique for forming a large number of heat promoting portions is described. Each of these projections disturbs a fluid such as a refrigerant flowing along the inner surface of the flat heat transfer tube so that heat can be efficiently exchanged between the inner surface of the flat heat transfer tube and the fluid such as the refrigerant. That is, each of the protrusions disturbs the flow of the fluid flowing along the inner surface of the flat heat transfer tube, thereby forming a boundary layer of a part of the inner surface of the flat heat transfer tube, which is located downstream of each of the protrusions. I try to destroy it.

[0004]

However, in the case of the projections of various shapes described in the above publication, these projections 1
The effect of disturbing the flow of the fluid by the individual pieces was small, and the effect of improving the heat conductivity was not always obtained. The heat exchanger of the present invention, in consideration of the above-described circumstances, enhances the effect of disturbing the flow of the fluid due to each of the protrusions by devising the structure of the protrusions provided on the heat transfer surface, thereby improving the heat exchange performance. It was invented so that it could be obtained.

[0005]

According to the heat exchanger of the present invention, a heat transfer promoting portion is provided on the heat transfer surface, and the heat transfer promoting portion is provided along the heat transfer surface, similarly to the above-described conventional heat exchanger. To disturb the flowing fluid. In particular, in the heat exchanger of the present invention, the heat transfer promoting section is constituted by a pair of ribs, each of which protrudes from the heat transfer surface. Meet requirements. The pair of ribs are arranged so as to be shifted from each other by 0.5 to 1.5 pitches in the flow direction of the fluid flowing along the heat transfer surface. The pair of ribs are arranged such that their upstream axes are located on a line parallel to the flow direction of the fluid, and their central axes are opposite to each other with respect to a line parallel to the flow direction of the fluid. The angle between the central axis of each rib and a line parallel to the flow direction of the fluid is set to 1
5 to 75 degrees. Further, when the heat transfer promoting portion is provided on an inner surface of a pair of parallel flat portions constituting a flat heat transfer tube, each of which is a heat transfer surface, the pair of ribs further includes the following: It is desirable to meet the requirements. The pair of ribs have the same amount of protrusion from the inner surface of each of the flat portions. The amount of protrusion of each of the ribs is determined by the distance between the two flat portions (the cross-sectional height of the inner flow path of the flat heat transfer tube). ) Is 20 to 50% of the size.

[0006]

In the case of the heat exchanger of the present invention configured as described above,
The boundary layer of a part of the heat transfer surface existing downstream of the heat transfer promoting portion can be efficiently destroyed. Therefore, the heat transfer efficiency between the heat transfer surface and the fluid flowing along the heat transfer surface can be increased. Therefore, the heat exchange performance of the heat exchanger including the heat transfer surface can be improved.

[0007]

1 to 3 show an example of an embodiment of the present invention. A flat heat transfer tube 1 formed by press forming or roll forming a plate made of a metal having good heat conductivity, such as an aluminum alloy, has a pair of flat portions 2, 2 parallel to each other, and each flat portion 2, 2 in the width direction (the left-right direction in FIG. 1). A large number of heat transfer promoting portions 4 are provided on the inner surfaces of the pair of flat portions 2, each of which is a heat transfer surface, in the axial direction. Each of the heat transfer promoting portions 4, 4 is constituted by a pair of elongated ribs 5, 5 each having a rectangular cross section and protruding toward the inside of the flat heat transfer tube 1.
The cross-sectional shape of each of the ribs 5, 5 may be, for example, a semicircle, a semi-ellipse, or a triangle.

The pair of ribs 5, 5 are indicated by arrows α in FIG.
In the flow direction of the fluid flowing in the flat heat transfer tube 1 (in the axial direction of the flat heat transfer tube 1), they are displaced from each other (offset). In the illustrated example, this offset amount is one pitch (projection length L described later). Further, the pair of ribs 5, 5 are respectively
With the upstream edge {left edge of FIGS. 2 and 3 (A)} positioned on the center line β of the heat transfer promoting portion 4 parallel to the flow direction α, the respective center axes are aligned with this center line. They are inclined to the opposite sides with respect to β. In the illustrated example, the angle of attack θ, which is the angle between the central axis of each of the ribs 5 and 5 and the central line β, is set to 30 degrees. Note that the above-mentioned projection length L, and each rib 5, 5 is the length projected onto the central line beta, the length of each of these ribs 5, 5 in the case where the L _5, L = L ₅ · cos θ. The magnitude of the angle of attack θ of the pair of ribs 5, 5 may be different from each other. In addition, the pair of ribs 5 and 5 make the protrusion amounts h from the inner surface of the flat heat transfer tube 1 equal to each other. The protrusion amount h of each of the ribs 5, 5 is determined by the distance between the inner surfaces of the pair of flat portions 2, 2 (the cross-sectional height of the inner flow passage of the flat heat transfer tube 1).
20% to 50%. The ribs 5, 5 as described above are used.
Is formed at the same time as the flat heat transfer tube 1 is formed by press forming or roll forming, and after the flat heat transfer tube 1 is extruded, the ribs 5 are formed by roll forming or press forming. You can do things.

When the heat exchanger of the present embodiment incorporating the flat heat transfer tube 1 constructed as described above is used, when a fluid such as a refrigerant flows through the flat heat transfer tube 1, the pair of flat portions 2 , 2
A large number of heat transfer promoting portions 4 and 4 formed on the inner surface of FIG.
(A) and (B), the fluid flowing along the inner surfaces of the pair of flat portions 2 and 2 is disturbed as indicated by arrows. That is,
Fluid flowing along the inner surfaces of the pair of flat portions 2, 2 forms a pair of ribs 5,
5, a pair of vortices is generated downstream of the pair of ribs 5, 5 (the right side in FIGS. 2 and 3A). As described above, a pair of ribs 5, which constitute each heat transfer promoting portion 4, 4,
5 are inclined in directions opposite to each other with respect to the center line β of each of the heat transfer promoting portions 4, 4. Therefore, a pair of vortices (winding direction) generated downstream of the pair of ribs 5, 5
Are opposite to each other as shown in FIG.

Further, as described above, the pair of ribs 5, 5 constituting each heat transfer promoting portion 4, 4 are arranged offset from each other in the flow direction of the fluid. Therefore, these 1
Of the pair of ribs 5, 5, the vortex generated on the downstream side of the rib 5 on the upstream side (left side in FIGS. 2 and 3A) hits the upstream edge of the rib 5 on the downstream side. The vortex generated by the upstream rib 5 and the reverse vortex generated by the downstream rib 5 merge at the downstream rib 5 and include the downstream rib 5. The heat transfer promoting section 4,
4. A strong vortex is formed in a wide area downstream of 4. As a result,
Due to the pair of vortices in opposite directions, a part of the inner surfaces of the pair of flat portions 2, 2 constituting the flat heat transfer tube 1, a portion existing downstream of the heat transfer promoting portions 4, 4 Can be efficiently destroyed. For this reason, the heat transfer efficiency between the flat heat transfer tube 1 and the fluid flowing in the flat heat transfer tube 1 can be improved. Accordingly, the heat exchange performance of the heat exchanger incorporating the flat heat transfer tube 1 can be improved.

Although not shown, the offset amount of the pair of ribs 5 constituting the heat transfer promoting portions 4 is set to 0.
In this case, 1 is generated by each of the ribs 5 and 5.
The merging position of the pair of vortices moves downstream from the merging position when the ribs 5 and 5 are offset. Because of this,
In this manner, the boundary between the heat transfer promoting portion 4 and the confluence position on a part of the inner surfaces of the pair of flat portions 2 and 2 corresponds to the movement of the confluence position of the pair of vortices to the downstream side. The layer cannot be destroyed efficiently. Therefore, the heat transfer promoting sections 4, 4
It is preferable that the pair of ribs 5, 5 be offset from each other as in the present invention described above.

The heat transfer promoting portions 4 and 4 as described above are provided on portions other than the inner surface of the (flat) heat transfer tube among the heat transfer surfaces constituting the heat exchanger. However, it goes without saying that the boundary layer between these heat transfer surfaces can be efficiently destroyed, and the heat transfer efficiency between each of the heat transfer surfaces and the fluid can be improved.
As such a heat transfer surface, for example, the outer surface of the heat transfer tube,
Alternatively, the surface of a heat transfer fin such as a plate fin, a corrugated fin, or an inner fin may be considered.

[0013]

EXAMPLES Hereinafter, experiments performed by the present inventors to confirm the effects of the present invention will be described. In the experiment, the effect of the offset amount of the pair of ribs 5 constituting the heat transfer promotion section 4 and the magnitude of the angle of attack θ on the heat transfer efficiency between the heat transfer surface and the fluid was examined. Was. Note that, as in the above-described embodiment, the heat transfer promoting section 4 is connected to the flat heat transfer tube 1 (FIG. 1).
Is provided on the inner surfaces of the pair of flat portions 2 and 2 (FIG. 1), the protrusion amount h of the pair of ribs 5 and 5 with respect to the interval W between the inner surfaces of the flat portions 2 and 2. The size (ratio) is also a factor that changes the heat transfer efficiency. For this reason, in the experiment, the effect of the magnitude (ratio) of the protrusion amount h with respect to the space W on the heat transfer efficiency between the fluid and the inner surface of the flat heat transfer tube as the heat transfer surface was also examined. The flat heat transfer tube 1 used had a distance W between the inner surfaces of the pair of flat portions 2 and 10 of 10 mm.

First, only one heat transfer promoting portion 4 is provided on the inner surface of one of the pair of flat portions 2, 2. The heat transfer promoting unit 4 sets the pair of ribs 5 and 5 at an offset amount of one pitch (projected length L × 1) and sets the angle of attack θ
Is set to 30 degrees, and the protrusion amount h is set to 2 mm (20% of the interval W between the inner surfaces of the flat portions 2 and 2). Then, low-temperature air is sent toward the heat transfer promoting section 4 along the inner surface of the flat section 2 having a higher temperature than the surrounding area,
The surface temperature of the flat portion 2 was measured by thermography. Then, when the Reynolds number of the low-temperature air is 1500 (in the case of laminar flow), a cooling part as shown in FIG. Appeared in the downstream part. In the cooling part shown in FIG. 4A, the part a represented by the oblique lattice has a particularly low temperature portion outside the part a, and the part b represented by the oblique line is , Portions where the temperature is relatively low are shown. In the case where the heat transfer promoting portion 4 is configured by changing only the protrusion amount h of the pair of ribs 5 and 5 to 3 mm (a size of 30% of the interval W), FIG. As shown in ()), a wider-range cooling section appeared in the downstream portion of the heat transfer promoting section 4.

Such a measurement is carried out by changing only the protrusion amount h of the pair of ribs 5, 5 between 1 and 5 mm (10 to 50% of the interval W) in increments of 1 mm. where the obtained relation between the heat radiation amount the amount of projection h (the product of the area of the cooling section with reduced temperature), such results are shown by a solid line P ₁ is obtained in FIG. The case where the heat radiation amount ratio is 1 on the vertical axis of the graph shown in FIG. 5 means that the heat radiation amount of the cooling section is not provided with the heat transfer promoting section 4 on the inner surface of the flat section 2. Means the same as the heat radiation amount of the flat portion 2. As shown in FIG. 5, the heat radiation amount of the cooling section sharply increases when the protrusion amount h exceeds the size of 20% of the interval W. Therefore, the size of the protrusion amount h is 2
In the range of 0 to 50% (more preferably 30 to 50%),
The heat exchange between the flat portion 2 and the fluid is improved, and the temperature of the flat portion 2 can be sufficiently reduced.

The reason why the upper limit of the amount of protrusion h is set to 50% of the distance W is that if the amount of protrusion h is further increased, the flow rate of the fluid flowing through the flat heat transfer tube 1 will increase. This is because the resistance is increased and the heat transfer performance between the flat heat transfer tube 1 and the fluid is reduced. Also, the dashed line to _{Q 1} 5, the Reynolds number of the cold air 700
It shows the measurement results when 0 (turbulent flow).
As apparent from FIG. 5, even in the case of the turbulent flow, the effect is not so large as in the case of the laminar flow, but the protrusion amount h
In the range of 20 to 50% (more preferably 30 to 50%) of the interval W, the heat exchange between the flat portion 2 and the fluid is improved, and the temperature of the flat portion 2 is sufficiently increased. Can be reduced.

Next, the relationship between the angle of attack θ and the amount of heat released from the cooling section was examined. That is, the same experiment as above was performed.
The heat transfer was promoted by changing only the angle of attack θ while keeping the offset amount and the protrusion amount h of the pair of ribs 5 constituting the heat transfer promoting section 4 constant. First, such an experiment was carried out by changing the angle of attack θ from 15 to 90 degrees in increments of 15 degrees while equalizing the angles of attack θ of the pair of ribs 5, 5. The result as shown in FIG. As is apparent from FIG. 6, when the flow of the fluid (air) is in a laminar flow state (solid line P ₂ ), when the angle of attack θ is in the range of 15 to 75 degrees,
It has been found that the heat radiation amount of the cooling unit can be sufficiently increased.
Also, when the flow of the fluid is in a turbulent state (broken line Q ₂ ),
Although not as pronounced as in the case of the laminar flow, the angle of attack θ
It was found that the heat radiation amount of the cooling unit could be increased in the range of 15 to 75 degrees. Although not shown, the above-described experiment was performed by setting the angle of attack θ of the pair of ribs 5 and 5 different from each other.
It was found that the heat radiation amount of the cooling unit could be increased in the range of 15 to 75 degrees.

Further, the relationship between the offset amount and the heat radiation amount of the cooling section was examined. That is, the same experiment as described above was carried out except that the angle of attack θ and the protrusion amount h of the pair of ribs 5, 5 constituting the heat transfer promoting unit 4 were kept constant, and only the offset amount was 0.5 to 1.5 pitch (Projection length L × 0.5-1.5)
Up to 0.5 pitch increments, the results shown in FIG. 7 were obtained. As shown in FIG. 7, when the flow of the fluid is in a laminar flow state (solid line P ₃ ), the heat radiation amount of the cooling unit can be sufficiently increased when the offset amount is in the range of 1 to 1.5 pitches. I understood that. On the other hand, when the flow of the fluid is in a turbulent state (broken line Q ₃ ), it has been found that the heat radiation amount of the cooling unit can be sufficiently increased when the offset amount is in the range of 0.5 to 1.5 pitches. .

Next, FIG. 8 shows the results of an experiment conducted by the present inventor to compare the performance of the flat heat transfer tube incorporated in the heat exchanger of the present invention with that of the conventional flat heat transfer tube. In such an analysis, a plurality of flat heat transfer tubes in which the heat transfer accelerating portion and the conventional projections of various shapes constituting the present invention are similarly arranged on the respective inner surfaces are described. The heat transfer efficiency between the fluid flowing inside each flat heat transfer tube and the rate at which the surface of the flat heat transfer tube is improved compared to the case where the surface of the flat heat transfer tube is merely a flat surface, and the rate at which the pressure loss increases are analyzed. . In this analysis, each flat heat transfer tube is assumed to have a distance W between inner surfaces of a pair of flat portions constituting the flat heat transfer tube of 10 mm. Further, the heat transfer promoting section sets a pair of ribs with an offset amount of one pitch, an angle of attack θ of 30 degrees, and a protrusion amount h of 3 mm (30% of the interval W). Was configured.

In FIG. 8, each point surrounded by a broken line a
The analysis results when the Reynolds number of the fluid (air) is 1500 (in the case of laminar flow), and the points surrounded by the chain line b are the analysis in the case where the Reynolds number of the fluid is 7000 (in the case of turbulent flow). The results are shown respectively. First, when the flow of the fluid is laminar, as shown by a point P in FIG. 8, the rate of increase in the heat transfer efficiency between the flat heat transfer tube of the present invention and the fluid (protrusions and the like are provided on the inner surface). The rate of increase in the heat transfer efficiency between the flat heat transfer tube and the fluid) is smaller than the rate of increase in the heat transfer efficiency of any of the conventional flat heat transfer tubes indicated by dots such as circles, triangles, and squares in FIG. At least 60% or more, and it was found that the rate of increase of the pressure loss was not so large. Further, even when the flow of the fluid is in a turbulent state, as shown by a point Q in FIG. 8, the rate of increase in the heat transfer efficiency between the flat heat transfer tube and the fluid of the present invention is indicated by a circle or a triangle in the same figure. In comparison with the conventional rate of increase in heat transfer efficiency of any of the flat heat transfer tubes indicated by points such as squares and squares, it was found that the heat transfer efficiency was at the top level.

[0021]

Since the heat exchanger of the present invention is constructed and operates as described above, heat exchange between the heat transfer surface and the fluid is effectively performed to improve the performance of the heat exchanger. Can do things.

[Brief description of the drawings]

FIG. 1 is a perspective view of a flat heat transfer tube, showing an example of an embodiment of the present invention.

FIG. 2 is a perspective view of a heat transfer promoting unit.

FIG. 3 shows a state of a fluid disturbed by a heat transfer promoting unit, and FIG. 3 (A) is a perspective view. (B) is an arrow X view of (A).

FIG. 4 is a plan view showing a cooling unit obtained by a heat transfer promoting unit.

FIG. 5 is a diagram showing the relationship between the amount of protrusion of a pair of ribs and the amount of heat radiation.

FIG. 6 is a diagram showing a relationship between an angle of attack of a pair of ribs and a heat radiation amount.

FIG. 7 is a diagram showing the relationship between the amount of offset between a pair of ribs and the amount of heat radiation.

FIG. 8 is a diagram showing the results of an experiment performed to compare the performance of the present invention with a conventional structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat heat transfer tube 2 Flat part 3 Continuous part 4 Heat transfer promotion part 5 Rib

Claims (2)

[Claims] In a heat exchanger in which a heat transfer promoting portion is provided on a heat transfer surface and a fluid flowing along the heat transfer surface is disturbed by the heat transfer promoting portion, each of the heat transfer promoting portions includes Are constituted by a pair of ribs protruding from the heat transfer surface, and the pair of ribs satisfy the following requirements (1) to (4). The pair of ribs are arranged so as to be shifted from each other by 0.5 to 1.5 pitches in the flow direction of the fluid flowing along the heat transfer surface. The pair of ribs are arranged such that their upstream axes are located on a line parallel to the flow direction of the fluid, and their central axes are opposite to each other with respect to a line parallel to the flow direction of the fluid. The angle between the central axis of each rib and a line parallel to the flow direction of the fluid is set to 1
5 to 75 degrees. 2. The heat transfer promoting portion is provided on the inner surface of the flat heat transfer tube, and the height of each rib is 20 to 50% of the cross-sectional height of the inner flow passage of the flat heat transfer tube. 2. The heat exchanger according to 1.