HK1140810B - Heat exchanger - Google Patents

Description

Heat exchanger

Technical Field

The present invention relates to a heat exchanger, and more particularly, to a heat exchanger including a plurality of heat exchange tubes arranged in parallel, the heat exchange tubes being formed of a material having thermal conductivity as hollow tubes having a flat cross section, and cooling or heating a heat exchange fluid by heat exchange between the heat exchange fluid flowing through the plurality of heat exchange tubes and a fluid to be heat exchanged flowing between the plurality of heat exchange tubes.

Background

Conventionally, as such a heat exchanger, a heat exchanger including a plurality of tubes for allowing a refrigerant to flow between an inlet tank and an outlet tank of the refrigerant and exchange heat with the atmosphere has been proposed (for example, see patent document 1). In this heat exchanger, while the refrigerant flowing into the inlet tank is caused to flow through the plurality of tubes and reach the outlet tank, the refrigerant is cooled by heat exchange with the atmosphere between the tubes substantially perpendicular to the plurality of tubes. In addition, cooling fins are installed between the plurality of tubes in order to improve heat exchange efficiency.

Further, a heat exchanger including a plurality of tubes having a small diameter, which are configured to allow a refrigerant to flow through two header tanks forming an inlet and an outlet of the refrigerant and to exchange heat with the atmosphere, has been proposed (for example, see patent document 2). In this heat exchanger, a refrigerant is caused to flow through a plurality of tubes having a small diameter, and the atmosphere is caused to pass between the plurality of tubes, whereby the refrigerant is cooled by heat exchange between the refrigerant and the atmosphere.

Further, a flat tube heat exchanger has been proposed in which a plurality of hollow tubes having a flat cross section are arranged in parallel to increase the heat transfer area. In this heat exchanger, a finless heat exchanger including no cooling fin is configured to reduce the pressure loss of the fluid flowing between the flat tubes and to achieve miniaturization.

Patent document 1: japanese patent laid-open No. 2001 + 167782

Patent document 2: japanese patent laid-open publication No. 2004-218969

Disclosure of Invention

Although the amount of heat generated from the drive power supply of a personal computer or a robot is very small compared to the amount of industrial waste heat, the amount of heat generated per unit area and per unit time is tens of times that for industrial use. Further, the power supply unit is covered with a heat insulating material or the like, and thus is in a form in which heat is easily accumulated, and the heat generating unit cannot be directly cooled. Further, the demand for miniaturization also places restrictions on the installation location of the heat exchanger, and the weight reduction is also demanded.

In recent years, engines and fuel cells are further required to have improved thermal efficiency and clean exhaust gas, and therefore cooling is also required to efficiently recover and utilize the heat in the exhaust gas and lower the combustion temperature. In exhaust heat recovery and cooling of supply and exhaust gases, condensed water is acidic and is required to have good drainage properties, but stainless steel having excellent corrosion resistance has low thermal conductivity, and therefore, when fins are used, a problem arises in that fin efficiency is reduced. In addition, the fins also obstruct the downward flow of the condensed water, and the heat exchange may not be efficiently performed.

Further, in the heat exchanger in which a plurality of flat tubes are arranged, when the internal pressure of the flat tubes increases, the flat portions may be deformed outward, and in this case, the passage resistance of the fluid passing between the tubes increases, and the heat exchange amount decreases.

One of the objects of the heat exchanger of the present invention is to improve heat exchange efficiency. Another object of the heat exchanger of the present invention is to achieve miniaturization.

In order to achieve at least part of the above object, the heat exchanger of the present invention employs the following aspects.

A heat exchanger according to the present invention is a heat exchanger including a plurality of heat exchange tubes arranged in parallel, the heat exchange tubes being formed of a material having thermal conductivity and formed into hollow tubes having a flat cross section, and being configured to cool or heat a heat exchange fluid flowing through the plurality of heat exchange tubes by heat exchange between the heat exchange fluid and a fluid to be heat exchanged flowing between the plurality of heat exchange tubes, the heat exchange tubes including: the plurality of heat exchange tubes are formed with wavy irregularities on at least one of an outer wall surface and an inner wall surface through which a fluid flows, the wavy irregularities forming an angle with a predetermined direction within a range of 10 degrees to 60 degrees and being symmetrically folded back along folding lines at predetermined intervals in the predetermined direction.

In the heat exchanger of the present invention, wavy irregularities are formed on at least one of the outer wall surface and the inner wall surface of the plurality of heat exchange tubes through which the fluid flows, and the wavy irregularities are folded back symmetrically along folding lines at predetermined intervals in a predetermined direction at an angle in a range of 10 to 60 degrees with respect to the predetermined direction. The wavy irregularities formed on the outer wall surfaces or inner wall surfaces of the plurality of heat exchange tubes cause the vortex of the secondary flow generated during the circulation of the fluid to act as a secondary flow component that effectively promotes heat transfer. Therefore, the heat exchange efficiency of the heat exchanger can be improved, and a high-performance and small-sized heat exchanger can be formed. Here, the "predetermined direction" is preferably a direction of a main flow of the fluid, but is not limited thereto, and may be a direction having a predetermined angle with respect to the main flow of the fluid. The heat exchanger is preferably installed such that the heat exchange fluid and the fluid to be heat-exchanged flow substantially orthogonally to each other as a whole, but is not limited to this, and may be installed such that the heat exchange fluid and the fluid to be heat-exchanged flow at a predetermined angle in a cross manner, or such that the heat exchange fluid and the fluid to be heat-exchanged flow in a counter manner.

In the heat exchanger of the present invention, the heat exchanger may be characterized in that: the plurality of heat exchange tubes have the wavy irregularities formed on a surface of the heat exchange fluid through which a fluid having a low thermal conductivity among the heat exchange fluid and the heat-receiving fluid flows. By forming the wavy unevenness on the surface where the fluid having low thermal conductivity flows, the amount of heat transfer to the fluid having low thermal conductivity can be increased, and a heat exchanger having high efficiency can be formed. In this case, the present invention may be characterized in that: the plurality of heat exchange tubes have wavy projections and recesses formed on a surface of the heat exchange fluid through which a fluid having a high thermal conductivity flows, the surface being parallel to the wavy projections and recesses formed on the surface of the heat exchange fluid through which the fluid having a low thermal conductivity flows. For example, this form is obtained when corrugated irregularities are formed simultaneously with the press working of a thin plate to form heat exchange tubes. That is, since the thin plate itself is formed in a corrugated shape, the corrugated irregularities formed on the outer wall surface of the heat exchange tube and the corrugated irregularities formed on the inner wall surface are formed in parallel and paired integrally with each other. In addition, when the wavy unevenness is formed on both the outer wall surface and the inner wall surface, the wavy unevenness on the outer wall surface and the wavy unevenness on the inner wall surface may be formed in different directions, without forming the wavy unevenness on the inner wall surface in parallel to form a pair with the wavy unevenness formed on the outer wall surface.

In addition, in the heat exchanger of the present invention, it is possible to provide: a plurality of heat exchange tubes, each of which has the corrugated irregularities formed on at least the outer wall surface; the plurality of heat exchange tubes are attached so that the wavy projections and recesses formed on the outer wall surface are parallel to each other. Since the plurality of heat exchange tubes are attached in parallel to the wavy concavities and convexities, the flow resistance of the heat exchange fluid can be reduced as compared with the case where the heat exchange tubes are attached so that the wavy concavities and convexities oppose each other, that is, so that the peaks and valleys of the waves oppose each other and the valleys oppose each other.

Further, the heat exchanger of the present invention may be characterized in that: the plurality of heat exchange tubes are arranged so that the corrugated irregularities satisfy 1.3 × Re when the amplitude of the corrugated irregularities is a, the pitch is p, and the reynolds number defined by the overall flow velocity and the pitch is Re^-0.5An inequality of < a/p < 0.2, wherein the pitch is a pitch of the wavy concavities and convexities facing each other with the fluid interposed therebetween. In this way, the vortex of the secondary flow generated when the fluid flows can be made to function as a secondary flow component that effectively promotes heat transfer without being affected by the wall surfaces facing each other across the fluid. As a result, a high-performance and small-sized heat exchanger having higher heat exchange efficiency can be formed.

Alternatively, the heat exchanger of the present invention may be characterized in that: and a plurality of heat exchange tubes, wherein the corrugated irregularities are formed so as to satisfy an inequality of 0.25 < W/z < 2.0, where W is the predetermined interval of the folded lines and z is the wavelength of the corrugated irregularities. Thus, the ratio of the distance in the width (span) direction in which the secondary flow component moves to the distance in the perpendicular direction to the opposing wall surface can be suppressed from increasing, and the secondary flow component contributing to the promotion of heat transfer can be maintained large. As a result, a high-performance and small-sized heat exchanger having higher heat exchange efficiency can be formed.

In addition, the heat exchanger of the present invention may be characterized in that: and a plurality of heat exchange tubes, wherein the wavy concavities and convexities satisfy an inequality of 0.25 < r/z where r is a radius of curvature of a top and/or bottom of the wavy concavities and convexities, and z is a wavelength of the wavy concavities and convexities. Thus, local increase in the fluid flow passing over the wavy convex-concave portions can be suppressed, and increase in the passage resistance can be suppressed. As a result, a high-performance and small-sized heat exchanger having higher heat exchange efficiency can be formed.

In addition, the heat exchanger of the present invention may be characterized in that: and a plurality of heat exchange tubes, wherein the wavy unevenness is formed such that an inclination angle of a slope in a cross section of the wavy unevenness is 25 degrees or more. In this way, the secondary flow component along the wavy unevenness can be increased, whereby the secondary flow contributing to heat conduction can be efficiently generated, and the area of the region of the inclined surface that effectively contributes to heat conduction in the cross section of the wavy unevenness can be increased. As a result, a high-performance and small-sized heat exchanger having higher heat exchange efficiency can be formed.

In addition, the heat exchanger of the present invention may be characterized in that: the plurality of heat exchange tubes are formed of a metal material into flat hollow tubes having a cross section of 9mm or less. The plurality of heat exchange tubes may be formed of a plate material having a thickness of 1.5mm or less.

Drawings

Fig. 1 is an external view showing an external appearance of a heat exchanger 20 according to an embodiment of the present invention.

Fig. 2 is an explanatory view showing the top, front, and side surfaces of the heat exchange tube 30 used in the heat exchanger 20 of the embodiment.

Fig. 3 is a cross-sectional explanatory view in which a plurality of the heat exchange tubes 30 of fig. 2 are juxtaposed in a cross-section a-a.

Fig. 4 is an explanatory view showing contours of secondary flows and temperatures of air generated on a flat plate when air flowing at a low flow rate is introduced into the flat plate of a corrugated plate shape.

Fig. 5 is an explanatory diagram showing the calculation results of the relationship between the amplitude pitch ratio (a/p), the reynolds number Re, and the improvement rate of thermal conductivity (h/hplate).

Fig. 6 is an explanatory diagram showing the calculation results of the relationship between the amplitude-to-pitch ratio (a/p) and the reynolds number Re, in which the thermal conductivity is 2 times or more that of the comparative example.

Fig. 7 is an explanatory diagram showing the calculation result of the relationship between the amplitude pitch ratio (a/p) and the improvement rate { (j/f)/(j/fplate) }, which is the improvement rate of the heat transfer friction ratio (j/f) that is the ratio between the kirschner j factor (コルバ — ン) and the friction coefficient f with respect to the ventilation.

Fig. 8 is an explanatory diagram showing the calculation results of the relationship between the space wavelength ratio (W/z) and the improvement rate (h/hplate) of the thermal conductivity.

Fig. 9 is an explanatory diagram showing the calculation results of the relationship between the curvature radius wavelength ratio (r/z) and the improvement rate of thermal conductivity (h/hplate).

Fig. 10 is an explanatory diagram showing a calculation result in which the relationship between the inclination angle α and the improvement rate (h/hplate) of the thermal conductivity is obtained.

Fig. 11 is an explanatory diagram illustrating an example of the structure of the heat exchange tube 30B according to the modification.

Fig. 12 is an explanatory diagram showing an example of a cross-sectional view taken along the section B1-B1 and a cross-sectional view taken along the section B2-B2 of the heat exchange tube 30C according to the modification.

Fig. 13 is an explanatory diagram illustrating an example of the structure of the heat exchange tube 30D according to the modification.

Detailed Description

Preferred embodiments for carrying out the present invention will be described below with reference to examples. Fig. 1 is an external view showing an external appearance of a heat exchanger 20 according to an embodiment of the present invention, fig. 2 is an explanatory view showing an upper surface, a front surface, and a side surface of a heat exchange tube 30 used in the heat exchanger 20 according to the embodiment, and fig. 3 is a sectional explanatory view showing a plurality of the heat exchange tubes 30 of fig. 2 arranged in parallel in a section a-a. The heat exchanger 20 of the embodiment, as shown, includes: a plurality of heat exchange tubes 30 formed as flat hollow tubes and arranged in parallel, and a pair of header tanks 40, 50 attached so as to cover the ends of the plurality of heat exchange tubes 30 and allowing heat exchange fluid to flow out of or into the plurality of heat exchange tubes 30.

The heat exchange tube 30 is formed in a flat tubular shape having a thickness of 0.5mm by pressing, bending, or the like, and is made of a material having thermal conductivity, such as a stainless steel material, and has a thickness of 0.1 mm. Flat surfaces (front and rear surfaces) of the heat exchange tube 30 are formed with a plurality of continuously curved crest portions (convex portions) 34 indicated by solid lines in fig. 2 and a plurality of continuously curved trough portions (concave portions) 36 indicated by one-dot chain lines between the plurality of crest portions 34 in parallel on the front and rear surfaces as viewed from the outer wall surface side, and are formed with a plurality of continuously curved trough portions (concave portions) corresponding to the plurality of continuously curved crest portions (convex portions) 34 of the outer wall surface and a plurality of continuously curved crest portions (convex portions) corresponding to the plurality of continuously curved trough portions (concave portions) 36 of the outer wall surface as viewed from the inner wall surface side. That is, the flat surfaces (front and rear surfaces) of the heat exchange tube 30, if the end portions are not seen, are formed in a corrugated plate shape including a plurality of continuously curved crest portions (convex portions) 34 and a plurality of continuously curved trough portions (concave portions) 36. In the embodiment, the heat exchanger 20 is configured such that a heat exchange fluid (e.g., water or oil) flows in the heat exchange tubes 30 from above to below the front surface in fig. 2, and as illustrated in the front surface in fig. 2 and fig. 3, a fluid to be heat-exchanged (e.g., air) flows substantially perpendicularly to the flow of the heat exchange fluid flowing in the heat exchange tubes 30, and the heat exchange fluid is cooled or heated by heat exchange between the heat exchange fluid and the fluid to be heat-exchanged. Next, a case of using oil as the heat exchange fluid and air as the heat exchange target fluid will be described.

The plurality of crests 34 and troughs 36 formed on the flat surfaces (front and rear surfaces) of the heat exchange tube 30 are formed such that a connecting line (solid line, one-dot chain line) of the crests 34 and the troughs 36 forms an angle γ in the range of 10 degrees to 60 degrees, for example, 30 degrees with respect to the main flow of air (air flow from the left to the right in the front of fig. 2), and is symmetrically folded back at a folding back line (line not shown connecting the curved portions of the solid line, one-dot chain line in fig. 2) at a predetermined interval (folding back interval) W along the main flow of air. In this way, the heat exchange tubes 30 are formed such that the angle γ between the connecting line (solid line, one-dot chain line) of the crest portion 34 and the trough portion 36 and the air flow (main flow) is in the range of 10 degrees to 60 degrees, in order to efficiently generate the secondary flow of air. Fig. 4 shows contours of secondary flows (arrows) and temperatures of air generated on a flat plate when air flowing at a low flow rate is introduced into the flat plate of a corrugated plate shape. As shown in the drawing, the crest portions 34 and the trough portions 36 generate strong secondary flows, and a large temperature gradient is generated in the vicinity of the wall surface. In the embodiment, the angle γ formed by the connecting line (wavy line, one-dot chain line) of the peak portion 34 and the valley portion 36 and the main flow of air is set to 30 degrees in order to efficiently generate the secondary flow. If the angle γ is too small, no effective secondary flow can be generated in the air stream; if the angle γ is too large, the air cannot flow along the crest 34 and the trough 36, and peeling occurs, local acceleration occurs, and the ventilation resistance increases. Therefore, in order to generate the secondary flow of air, the angle γ is preferably 10 degrees to 60 degrees, more preferably 15 degrees to 45 degrees, and even more preferably 25 degrees to 35 degrees within the range of an acute angle. In the exemplary embodiment, therefore, 30 degrees are used as angle γ. In addition, when the air flow is small, the secondary flow generated by the peak portions 34 and the valley portions 36 can be efficiently generated while keeping the main flow of the air flow substantially the same as that in the case of a simple flat plate without the peak portions 34 and the valley portions 36. Here, in the embodiment, the angle γ is constant at 30 degrees, but the angle γ is not necessarily constant, and may be changed so that the peak portion 34 and the valley portion 36 are curved. As described above, the plurality of crests 34 and troughs 36 are formed on the flat surfaces (front and rear surfaces) of the heat exchange tubes 30 of the embodiment so that the angle γ with respect to the main flow of air is an angle in the range of 10 degrees to 60 degrees, because the thermal conductivity of air as the heat exchange fluid flowing outside the heat exchange tubes 30 is smaller than that of oil as the heat exchange fluid flowing inside the heat exchange tubes 30, and therefore the heat transfer with respect to air is improved, thereby improving the performance of the heat exchanger 20.

As shown in fig. 3, the heat exchanger 20 of the embodiment configured as described above is disposed in parallel with the crests 34 and troughs 36 formed on the outer wall surfaces of the opposing heat exchange tubes 30, that is, the crests 34 of one heat exchange tube 30 are aligned with the troughs 36 of the other heat exchange tube 30, and the troughs 36 of one heat exchange tube 30 are aligned with the crests 34 of the other heat exchange tube 30. This arrangement is to reduce the ventilation resistance of the air flowing between the heat exchange tubes 30. That is, the air flow resistance of the heat exchanger 20 of the embodiment is smaller than that in the case where the peak portions 34 of one of the heat exchange tubes 30 are integrated with the peak portions 34 of the other heat exchange tube 30, and the valley portions 36 of one of the heat exchange tubes 30 are integrated with the valley portions 36 of the other heat exchange tube 30.

In the embodiment, the plurality of heat exchange tubes 30 are formed such that the amplitude pitch ratio (a/p) between the amplitude a (see fig. 3) of the waveform including the crest 34 and the trough 36 and the pitch p (see fig. 3) which is the interval between the adjacent heat exchange tubes 30 is within the range of the inequality of the following expression (1), and the plurality of heat exchange tubes 30 are assembled to the heat exchanger 20. Here, "Re" in the formula (1) is a reynolds number, and is represented by Re up/ν (ν is a kinematic viscosity coefficient) when the bulk flow rate u and the pitch p are used. The inequality on the left side of the formula (1) is based on the amplitude-to-pitch ratio (a/p) being 1.3 × Re^-0.5In a wide range, the improvement rate (h/hplate) is calculated as a ratio of the thermal conductivity h of the wave plate in which the waveform including the crest 34 and the trough 36 is formed to the thermal conductivity hplate of the plate in which the waveform including the crest 34 and the trough 36 is not formed, to 2.0 or more. Fig. 5 shows the calculation results of the relationship between the amplitude pitch ratio (a/p) and the reynolds number Re and the improvement rate of thermal conductivity (h/hplate), and fig. 6 shows the calculation results of the relationship between the amplitude pitch ratio (a/p) and the reynolds number Re, in which the thermal conductivity is 2 times or more that of the comparative example. From the results of fig. 5, it is understood that the optimum amplitude pitch ratio (a/p) exists for the reynolds number Re, and from the results of fig. 6, it is understood that the left inequality of equation (1) can be derived. The inequality on the right side of the expression (1) is based on the calculation result that the amplitude pitch ratio (a/p) is less than 0.2, the influence of the increase of the ventilation resistance is suppressed, and the heat transfer performance is good. Fig. 7 shows the calculation result of the relationship between the amplitude pitch ratio (a/p) and the improvement rate { (j/f)/(j/fplate) }, which is the ratio of the kirschner j factor to the friction coefficient f against the ventilation, i.e., the heat transfer friction ratio (j/f), of the heat transfer friction ratio (j/fplate) of the heat sink of the comparative example. Here, the kirberghen j factor is a quasi number (a number having a dimension of 1) of the thermal conductivity. Therefore, the heat transfer friction ratio (j/f) is a ratio of the heat transfer performance to the ventilation resistance, and therefore, the larger the ratio, the higher the performance of the heat exchanger. As is clear from fig. 7, in the range where the amplitude pitch ratio (a/p) is less than 0.2, the rate of increase of the heat transfer friction ratio { (j/f)/(j/fplate) } can be made 0.8 or more, and when the amplitude pitch ratio (a/p) becomes greater than 0.2, the influence of the increase in the draft resistance becomes greater, and the performance as a heat exchanger deteriorates. The amplitude a of the waveform does not necessarily have to be constant, and the average value of the whole waveform when the amplitude pitch ratio (a/p) is set to be within the range of expression (1).

1.3×Re^0.5＜a/p＜0.2(1)

In the embodiment, the plurality of heat exchange tubes 30 are formed so that the pitch wavelength ratio (W/z) between the folding interval W (see fig. 2), which is an interval at which the connection line (solid line, one-dot chain line) of the peak portion 34 and the valley portion 36 is folded symmetrically with respect to the main flow of air, and the wavelength z (see fig. 3) of the waveform including the peak portion 34 and the valley portion 36 is in a range of more than 0.25 and less than 2.0 as shown in the following formula (2). This is a result of calculation based on a good improvement rate (h/hplate) which is the ratio of the thermal conductivity h of the wave plate to the thermal conductivity hplate of the flat plate, in which the space wavelength ratio (W/z) is in the range of more than 0.25 and less than 2.0. Fig. 8 shows the calculation results of the relationship between the space wavelength ratio (W/z) and the improvement rate of thermal conductivity (h/hplate). As shown in the figure, the space wavelength ratio (W/z) was in the range of more than 0.25 and less than 2.0, and the improvement rate of the thermal conductivity (h/hplate) was good. As is clear from fig. 8, the spacing wavelength ratio (W/z) is preferably greater than 0.25 and less than 2.0, more preferably greater than 0.5 and less than 2.0, and still more preferably greater than 0.7 and less than 1.5. The wavelength z of the waveform is not necessarily constant, and the average value of the entire waveform when the interval wavelength ratio (W/z) is set may be within the range of expression (2).

0.25＜W/z＜2.0(2)

Further, in the embodiment, the plurality of heat exchange tubes 30 are formed so that the radius of curvature wavelength ratio (r/z) between the radius of curvature r (see fig. 3) of the top of the crest portion 34 and the bottom of the trough portion 36 and the wavelength z of the waveform including the crest portion 34 and the trough portion 36 is in a range of more than 0.25 as shown in the following expression (3). This is a calculation result based on that the ratio of the radius of curvature to the wavelength (r/z) is in the range of more than 0.25, and the improvement rate (h/plate), which is the ratio of the thermal conductivity h of the wave plate to the thermal conductivity hplate of the flat plate, becomes good. Fig. 9 shows the calculation results of the relationship between the curvature radius wavelength ratio (r/z) and the improvement rate of thermal conductivity (h/hplate). The curvature radius r of the top of the crest 34 and the bottom of the trough 36 is related to a local increase in the airflow speed when the air passes over the crest 34 and the trough 36, and an increase in the ventilation resistance can be suppressed by suppressing the local increase in the airflow speed. The curvature radius wavelength ratio (r/z) is obtained from the relationship between the appropriate range of the curvature radius r and the wavelength z. As shown in fig. 9, it was found that the ratio of the radius of curvature to the wavelength (r/z) was in the range of more than 0.25, and the improvement rate of the thermal conductivity (h/hplate) was good. As is clear from fig. 9, the radius of curvature wavelength ratio (r/z) is preferably greater than 0.25, more preferably greater than 0.35, and still more preferably greater than 0.5. The curvature radius r is not necessarily constant, and the average value of the entire curvature radius wavelength ratio (r/z) may be within the range of expression (3).

0.25＜r/z (3)

In the embodiment, the plurality of heat exchange tubes 30 are formed such that the inclination angle α (see fig. 3) of the wavy cross section including the crest portions 34 and the trough portions 36 is 25 degrees or more. This is based on the calculation result that the rate of increase (h/hplate) which is the ratio of the thermal conductivity h of the wave plate to the thermal conductivity hplate of the flat plate becomes good in the range where the inclination angle is 25 degrees or more. This is because the air flow along the waveform including the crest portions 34 and the trough portions 36 can be enhanced, and the secondary flow contributing to the heat transfer can be efficiently generated. Fig. 10 shows the calculation result of the relationship between the inclination angle α and the improvement rate (h/hplate) of the thermal conductivity. As shown in the figure, it is understood that the rate of improvement in thermal conductivity (h/hplate) is good in the range where the inclination angle α is 25 degrees or more. As is apparent from fig. 10, the inclination angle α is preferably 25 degrees or more, more preferably 30 degrees or more, and still more preferably 40 degrees or more.

According to the heat exchanger 20 of the embodiment described above, the crest portions 34 and the trough portions 36 are formed on the flat surfaces (front and rear surfaces) of the heat exchange tubes 30, and the connecting lines (solid lines and one-dot chain lines) between the crest portions 34 and the trough portions 36 form a predetermined angle (for example, 30 degrees) in the range of 10 degrees to 60 degrees with respect to the main flow of air, and are symmetrically folded back along the folding back lines at the predetermined intervals (folding back intervals) W along the main flow of air, whereby effective secondary flows can be generated in the air flow, the heat transfer efficiency can be improved, and the overall heat exchange efficiency can be improved. As a result, the heat exchanger 20 can be provided as a small-sized and high-performance heat exchanger. Further, by forming a plurality of continuously curved peak portions (convex portions) 34 and a plurality of continuously curved valley portions (concave portions) 36 on the flat surfaces (front and rear surfaces) of the heat exchange tube 30, the strength of the flat surfaces can be increased, and the pressure resistance can be increased. When the rigidity of the flat surface is increased, the transmittance of noise generated in the heat exchange tube 30 is reduced, and therefore a heat exchanger having excellent stability can be obtained. Further, since the rigidity of the heat exchange tube 30 is improved, deformation when the heat exchange tube 30 is formed by bending or the like can be reduced, and the assemblability of the heat exchange tube 30 can be improved.

In the heat exchanger 20 according to the embodiment, the plurality of heat exchange tubes 30 are formed so as to have the amplitude pitch ratio (a/p) within the range of the inequality of the above expression (1), the amplitude pitch ratio (a/p) being the ratio of the amplitude a of the waveform including the crest portions 34 and the trough portions 36 and the fin pitch p being the interval between the adjacent heat exchange tubes 30, and the heat exchanger 20 is assembled, so that the heat conductivity of the heat exchanger 20 can be made good. As a result, the heat exchanger 20 can be further miniaturized.

Further, according to the heat exchanger 20 of the embodiment, the plurality of heat exchange tubes 30 are formed so that the interval wavelength ratio (W/z) of the folded interval W where the connection line of the peak portion 34 and the valley portion 36 is folded symmetrically with respect to the main flow of the air and the wavelength z of the waveform including the peak portion 34 and the valley portion 36 is in the range of more than 0.25 and less than 2.0 as expressed by the above expression (2), and therefore, the heat conductivity of the heat exchanger 20 can be made good. As a result, the heat exchanger 20 can be further miniaturized.

Further, according to the heat exchanger 20 of the embodiment, the heat exchange tubes 30 are formed so that the curvature radius wavelength ratio (r/z) of the curvature radius r of the top of the crest portion 34 and the bottom of the trough portion 36 to the wavelength z of the waveform including the crest portion 34 and the trough portion 36 is in the range of more than 0.25 as shown in the above expression (3), and therefore, the local increase in the speed of the air flow when the air passes over the crest portion 34 and the trough portion 36 is suppressed, and the increase in the ventilation resistance can be suppressed. As a result, the heat exchanger 20 can be a higher-performance heat exchanger.

In the heat exchanger 20 of the embodiment, the inclination angle α of the cross section of the heat exchange tube 30 including the waveform of the crest 34 and the trough 36 is 25 degrees or more, and therefore the heat conductivity of the heat exchanger 20 can be improved. As a result, the heat exchanger 20 can be further miniaturized.

In the heat exchanger 20 of the embodiment, the heat exchange tube 30 is formed in a corrugated plate shape including a plurality of continuously curved crests (convex portions) 34 and a plurality of continuously curved troughs (concave portions) 36 on the flat surfaces (front and back surfaces) of the heat exchange tube 30, that is, a plurality of continuously curved crests (convex portions) 34 and a plurality of continuously curved troughs (concave portions) 36 are formed on both the outer wall surface side and the inner wall surface side, but as illustrated in the heat exchange tube 30B of the modification of fig. 11, a plurality of continuously curved crests (convex portions) 34 and a plurality of continuously curved troughs (concave portions) 36 are formed on the outer wall surface side of the flat surfaces (front and back surfaces) of the heat exchange tube 30B, and such crests 34 and troughs 36 are not formed on the inner wall surface side. In this case, a plurality of continuously curved crests (convex portions) 34 and a plurality of continuously curved troughs (concave portions) 36 may be formed on the outer wall surface of the flat surface (front surface and back surface) of the heat exchange tube 30B, or such crests 34 and troughs 36 may be bonded. When the heat transfer coefficient of the heat exchange fluid flowing inside the heat exchange tubes is smaller than the heat transfer coefficient of the heat exchange fluid flowing outside the heat exchange tubes, as illustrated in the heat exchange tube 30C of the modification of fig. 12, a plurality of continuously curved crest portions (convex portions) 34 and a plurality of continuously curved valley portions (concave portions) 36 are formed on the inner wall surface side of the flat surface (front surface and rear surface) of the heat exchange tube 30, and the crest portions 34 and the valley portions 36 are not formed on the outer wall surface side. Fig. 12 is an explanatory diagram showing an example of a cross-sectional view of the heat exchange tube 30C of the modification taken along the section B1-B1 and a cross-sectional view taken along the section B2-B2. As illustrated in the heat exchange tube 30D of the modification of fig. 13, the crests 34 and the troughs 36 may be formed on the flat surfaces (front and rear surfaces) of the heat exchange tube 30 so that the intervals between the continuously curved crests (protrusions) 34 and the continuously curved troughs (recesses) 36 are not substantially uniform.

In the heat exchanger 20 of the embodiment, since the thermal conductivity of the air as the heat exchange fluid flowing outside the heat exchange tubes 30 is smaller than that of the oil as the heat exchange fluid flowing inside the heat exchange tubes 30, the plurality of crests 34 and troughs 36 are formed on the flat surfaces (front and rear surfaces) of the heat exchange tubes 30 so that the angle γ with respect to the main flow of the air is an angle in the range of 10 degrees to 60 degrees, but the plurality of crests 34 and troughs 36 may be formed so that the angle γ with respect to the direction having a predetermined angle (for example, 5 degrees, 10 degrees, or the like) with respect to the main flow of the air is an angle in the range of 10 degrees to 60 degrees.

In the heat exchanger 20 of the embodiment, the crest portions 34 and the trough portions 36 formed on the outer wall surfaces of the opposing heat exchange tubes 30 are arranged in parallel, that is, the trough portions 36 of the other heat exchange tube 30 are integrated with the crest portions 34 of one heat exchange tube 30, and the crest portions 34 of the other heat exchange tube 30 are integrated with the trough portions 36 of one heat exchange tube 30, but the crest portions 34 and the trough portions 36 formed on the outer wall surfaces of the opposing heat exchange tubes 30 may be arranged so as to oppose the crest portions 34 and the trough portions 36, respectively.

In the heat exchanger 20 of the embodiment, the plurality of heat exchange tubes 30 are formed so that the amplitude pitch ratio (a/p) is 1.3 × Re as shown in the above formula (1)^-0.5The heat exchanger 20 is assembled in the range of inequality of < a/p < 0.2, where the amplitude pitch ratio (a/p) is the ratio of the amplitude a of the waveform including the crest portion 34 and the trough portion 36 to the pitch p, which is the interval between the adjacent heat exchange tubes 30, but the heat exchanger 20 may be assembled in the range of inequality of the above equation (1) with the amplitude pitch ratio (a/p) of the plurality of heat exchange tubes 30 being outside.

In the heat exchanger 20 of the embodiment, the plurality of heat exchange tubes 30 are formed so that the pitch wavelength ratio (W/z) of the folded-back pitch W at which the connecting line of the peak portion 34 and the valley portion 36 is folded back symmetrically with respect to the main flow of the air and the wavelength z of the waveform including the peak portion 34 and the valley portion 36 is in the range of more than 0.25 and less than 2.0 as expressed by the above expression (2), but the plurality of heat exchange tubes 30 may be formed so that the pitch wavelength ratio (W/z) is not in the range of more than 0.25 and less than 2.0.

In the heat exchanger 20 of the embodiment, the plurality of heat exchange tubes 30 are formed so that the curvature radius wavelength ratio (r/z) of the top of the crest portion 34, the bottom of the trough portion 36, and the wavelength z of the waveform including the crest portion 34 and the trough portion 36 is in the range of more than 0.25, but the heat exchange tubes 30 may be formed so that the curvature radius wavelength ratio (r/z) is in the range of less than 0.25.

In the heat exchanger 20 of the embodiment, the heat exchange tubes 30 are formed such that the inclination angle α of the waveform cross section including the crest portions 34 and the trough portions 36 is 25 degrees or more, but the heat exchange tubes 30 may be formed such that the inclination angle α is less than 25 degrees.

In the heat exchanger 20 of the embodiment, the plate material formed of the stainless material having a thickness of 0.1mm is formed into the flat tubular heat exchange tubes 30 having a thickness of 0.5mm by press working, bending working, or the like, but the thickness of the plate material is not limited to 0.1mm, and plate materials having various thicknesses may be used depending on the use of the heat exchanger 20. In this case, the thickness of the tube is not limited to 0.5mm, and may be any thickness. When the heat exchanger 20 is used for recovering heat from waste heat, the heat exchange tubes 30 having a thickness of about 9mm can be formed using a plate material of 0.3 to 1.5 mm. The plate material forming the heat-exchange tubes 30 is not limited to stainless steel, and various materials can be used depending on the type of the heat-exchange fluid or the fluid to be heat-exchanged.

In the heat exchanger 20 of the embodiment, the heat exchange fluid flowing through the heat exchange tubes 30 and the fluid to be heat exchanged flowing through the heat exchange tubes 30 are made to flow so as to be orthogonal to each other, but the heat exchange fluid and the fluid to be heat exchanged may be made to flow opposite to each other or the fluid to be heat exchanged may be made to flow so as to intersect at a predetermined acute angle or an obtuse angle with respect to the flow of the heat exchange fluid.

While the best mode for carrying out the invention has been described with reference to the examples, it is needless to say that the invention is not limited to the examples, and various modes can be carried out without departing from the scope of the invention.

The present invention can be applied to the manufacturing industry of heat exchangers, and the like.

Claims (11)

1. A heat exchanger, which is a finless heat exchanger having a plurality of heat exchange tubes formed of a heat conductive material into hollow tubes having a flat cross section and arranged in parallel, wherein a heat exchange fluid flowing in the plurality of heat exchange tubes is cooled or heated by heat exchange with a heat exchange target fluid flowing between the plurality of heat exchange tubes, characterized in that:

wherein a plurality of corrugated irregularities formed by a continuous smooth curved surface are formed on at least one of an outer wall surface and an inner wall surface through which a fluid flows, and a plurality of crest portions and trough portions are formed on the corrugated irregularities, and wherein connecting lines of the crest portions and connecting lines of the trough portions are folded back symmetrically with respect to a folding line at a predetermined interval along a predetermined direction at an angle in a range of 10 to 60 degrees with respect to the predetermined direction,

in the plurality of heat exchange tubes, the wavy projections and recesses formed on the two facing wall surfaces are not in contact with each other.

2. The heat exchanger according to claim 1, wherein:

the plurality of heat exchange tubes have the wavy irregularities formed on a surface of the heat exchange fluid through which a fluid having a low thermal conductivity among the heat exchange fluid and the heat-receiving fluid flows.

3. The heat exchanger according to claim 2, wherein:

the plurality of heat exchange tubes have wavy projections and recesses formed on a surface of the heat exchange fluid through which a fluid having a high thermal conductivity flows, the surface being parallel to the wavy projections and recesses formed on the surface of the heat exchange fluid through which the fluid having a low thermal conductivity flows.

4. The heat exchanger according to claim 1, wherein:

a plurality of heat exchange tubes, each of which has the corrugated irregularities formed on at least the outer wall surface;

the plurality of heat exchange tubes are attached so that the wavy projections and depressions formed on the outer wall surface are parallel to each other.

5. The heat exchanger according to claim 1, wherein:

the predetermined direction is a direction of a main flow of the fluid.

6. The heat exchanger according to claim 1, wherein:

the wavy concavities and convexities of the plurality of heat exchange tubes are formed so as to satisfy an inequality of equation (1) where the amplitude of the wavy concavities and convexities is a, the pitch is p, and the Reynolds number defined by the overall flow velocity and the pitch is Re, where the pitch is the interval of the wavy concavities and convexities facing each other with the fluid interposed therebetween,

1.3×Re^-0.5＜a/p＜0.2 (1)。

7. the heat exchanger according to claim 1, wherein:

the wavy irregularities of the plurality of heat exchange tubes are formed so as to satisfy an inequality of equation (2) when the predetermined interval of the folded lines is W and the wavelength of the wavy irregularities is z,

0.25＜W/z＜2.0 (2)。

8. the heat exchanger according to claim 1, wherein:

the wavy unevenness of the plurality of heat exchange tubes is formed so as to satisfy an inequality of equation (3) where r is a radius of curvature of a top portion and/or a bottom portion of the wavy unevenness, and z is a wavelength of the wavy unevenness,

0.25＜r/z (3)。

9. the heat exchanger according to claim 1, wherein:

the plurality of heat exchange tubes are flat hollow tubes made of a metal material and having a cross-sectional thickness of 9mm or less.

10. The heat exchanger according to claim 1, wherein:

the plurality of heat exchange tubes are formed of a plate material having a thickness of 1.5mm or less.

11. The heat exchanger according to claim 1, wherein:

is installed so that the heat exchange fluid flows substantially orthogonally to the entire body of the heat-exchanged fluid.