KR20120071679A - Multi-vortex generator, and advanced heat exchanging apparatus using the same - Google Patents

Abstract

PURPOSE: A multi-vortex generating device and a high-end heat exchanger using the same are provided to enhance heat transmission properties in portions of the inside of a dimple and around a flat plate and to minimize a pressure loss by controlling properties of a vortex generated in the dimple with a vortex generating device. CONSTITUTION: A multi-vortex generating device comprises a dimple unit and a projected unit. The dimple unit is formed in a heat exchanging surface of a flow path. The projected unit generates a lateral axis vortex capable of reducing stagnation-flow domain inside of the dimple. The dimple unit and projected unit are repetitively formed in the heat exchanging surface. The projected unit has a concavo-convex shape.

Description

Multi-vortex generator and high performance heat exchanger using the same {Multi-vortex generator, and advanced heat exchanging apparatus using the same}

The present invention relates to a complex vortex generator and a high-performance heat exchanger using the same, in detail, i) dimples formed on the heat exchange surface of the flow path, and ii) generating a transverse vortex that can reduce the stagnant flow region in the dimples. The present invention relates to a composite vortex generator and a heat exchanger using the same, including a protrusion, an acoustic excitation, or a vibration unit.

1 is a basic shape of dimples formed in a conventional heat exchange surface to improve thermal performance, the dimples being arranged on the heat exchange surface in an aligned or staggered form. However, such a conventional dimple arrangement has a relatively low heat transfer coefficient (Sh = 10) in the dimple inner region, as can be seen from the Sherwood mumber distribution around the dimple of FIG. There is a problem in that an area having) is generated.

In order to solve the problem of the low heat transfer area formed inside the dimple, various attempts have been made, such as forming a double-sided dimple channel as shown in FIGS. 3 or variously arranged double-sided dimples as shown in FIGS. 4A to 4D. There was a limit to the reduction.

In the present invention, a complex vortex generation in which a lateral vortex generating unit such as a protrusion, an acoustic excitation unit or a vibrating unit is designed in combination with the dimple so as to drastically reduce the stagnant flow in the dimple and maximize the influence of the vortex in the dimple downstream plate portion. An apparatus and a heat exchanger using the same were developed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite vortex generator and a heat exchanger using the same that can improve heat transfer characteristics in the dimple and surrounding flat plate portions and minimize pressure loss.

It is an object of the present invention to provide a composite vortex generator and a heat exchanger using the same designed to enhance the flow of longitudinal vortices and trans versal vortices.

In order to achieve the object as described above, the present invention is a combination comprising: (i) a dimple formed on the heat exchange surface of the flow path, and ii) a projection for generating a transverse vortex that can reduce the stagnant flow area within the dimple. Provides a vortex generator, the dimple and the protrusion may be formed repeatedly on the heat exchange surface.

An embodiment of the protrusion may have a shape of rib turbulators, and the height ratio (d _rib / H) of the protrusions and the flow paths is preferably 0.05 to 0.15. In addition, one embodiment of the protrusion may have a delta wing shape, the angle of the delta wing is 15 ~ 60 °, the height ratio of the delta wing and the flow path (d _dw / H) is 0.3 ~ 0.5 The depth ratio (d _dim / H) of the dimple and the flow path may be 0.2 to 0.4.

 On the other hand, in order to achieve the object described above, the present invention is an acoustic excitation for generating a dimple (dimple) formed on the heat exchange surface of the flow path, and ii) a transverse vortex that can reduce the stagnant flow region in the dimple Provided is a composite vortex generator including an acoustic excitation or a vibration unit.

In this case, it is preferable to match the frequency of the acoustic excitation unit or the vibrating unit with the vortex frequency formed in the dimple, and the frequency of the acoustic excitation unit may be in the range of 1 to 2 St (stroul number).

On the other hand, in order to achieve the object as described above, the present invention provides a heat exchanger including the complex vortex generator.

The complex vortex generator according to the present invention is a combination of dimples and various vortex generators for improving the thermal performance of the heat exchanger and the cooling device. The vortices generated in the dimples are controlled by using the vortex generator to control the inside and around the dimples. It is possible to improve heat transfer characteristics at the plate portion and to minimize pressure loss.

That is, the present invention by installing a protrusion, an acoustic excitation or a vibrating portion as a vortex generating device so that the longitudinal vortices and transverse vortices flow is strengthened with each other to improve thermal performance, the vortex generation Optimizing the specifications of the devices and dimples resulted in excellent thermal performance.

Figure 1-Basic cross-sectional view of the conventional dimple installed
Figure 2-Heat (Material) Transfer Coefficient (St) Characteristics in a Basic Flow Channel with Conventional Dimples Installed
3-Flow path cross section with double sided dimple structure
4a, 4b, 4c, 4d-various arrangement shapes of double-sided dimple flow paths
Fig. 5-A cross-sectional view of a flow path shape using a dimple and an unevenness
6, 7-Heat transfer comparison table according to the height ratio of the unevenness and the flow path and Re _H (uneven installation position: y / d = -1.5, -2.5)
Figure 8-Cross-sectional view of the flow path using a dimple and a delta wing
9-Heat exchange surface diagram of dimples and delta wings arranged repeatedly
10, 11, 12-Heat transfer comparison table according to delta wing angle (β), wing height ratio (h _dw / H) and dimple depth ratio (h / H) (Re _H = 1000, 3000, 5000)
13-Heat transfer performance comparison table of the vortex generators and the conventional dimple structure of the present invention
14-Heat transfer distribution according to change of frequency (St) of sound excitation at 110dB sound pressure
15-Heat transfer distribution according to sound pressure (SPL) change in the same acoustic excitation frequency band (St = 1.1)

The composite vortex generating apparatus according to the present invention includes a dimple formed on the heat exchange surface of the flow path and a protrusion for generating a transverse vortex capable of reducing the stagnant flow region in the dimple. The dimple and the protrusion may be repeatedly formed on the heat exchange surface.

The protrusion may have various shapes that may generate a transverse vortex, and as an example, may have a shape of rib turbulators. The uneven flow creates a transverse vortex, which increases the heat transfer performance by causing the vortic flow to impinge inside the dimples downstream of the uneven.

The shape of the unevenness can be made by using a press or stamp or welding method, and by adjusting the height of the unevenness when forming the unevenness, the unevenness can only minimize the flow loss near the wall by minimizing the pressure loss of the entire channel. .

FIG. 6 illustrates the height ratio (d _rib / H) and the Reynolds number (Re _H ) of the unevenness / flow path at the different uneven installation positions (y / d = -1.5, -2.5), respectively, when a single dimple and a single unevenness are formed in combination. ) Is a comparison of the heat transfer improvement.

As can be seen in the figure, the height ratio (d _rib / H) of the unevenness / flow path should be appropriately set so as to minimize the pressure drop in the entire flow path while generating sufficient transverse vortex according to the installation position and fluid flow. May be set in the range of 0.05 to 0.15.

In addition, the protrusion may have a delta wing shape as shown in FIGS. 8 and 9 as an example. The vortex flow formed by the delta wing serves to improve the heat transfer performance of the stagnant flow zone inside the dimple downstream and to enhance the heat transfer characteristics in the dimple downstream plate. Like the unevenness, the delta wing may be installed in a channel or a wall by using various methods such as perforation and welding.

At this time, since the size, direction, strength, etc. of the vortex flow changes according to the installation angle of the triangular wing of the delta wing, it is preferable to vary the installation angle of the delta wing according to the characteristics of the fluid and the installation environment.

10 to 12 show that when a single dimple and a single delta wing are combined, at different Reynolds numbers (Re _H = 1000, 3000, 5000), the angle of the delta wing, the height ratio of the wings (h _dw / H), and the dimple This is a table comparing the degree of heat transfer improvement according to the depth ratio (h / H).

As can be seen in the figure, by appropriately combining the angle of the delta wing, the height ratio of the wings, the depth ratio of the dimples according to the fluid flow, it can be seen that the heat transfer coefficient is improved than when using only the dimples.

The dimples and the delta wing specifications should be appropriately set according to the fluid flow so as to minimize the pressure drop of the entire flow path while generating sufficient transverse vortex. Preferably, the angle of the delta wing is 15 ° to 60 °. °, the height ratio (d _dw / H) of the delta wing / flow path can be set to 0.3 ~ 0.5, the depth ratio (d _dim / H) of the dimple and the flow path is 0.2 to 0.4 range.

FIG. 13 is a comparison of the heat transfer performance of the dimples and convexities and the dimples and the delta wing in which the dimples and convexities are installed in comparison with the flow paths in which the conventional dimples are installed, as Sherwood numbers. ) And Dimple-DWP structures show up to 2.4 times higher heat transfer performance compared to conventional dimple structures.

In addition, an acoustic excitation device or a vibration device may be used as the vortex generator which is designed in combination with the dimple, and as in the case of the delta wing, the diameter, depth, arrangement, etc. of the dimple may be changed. The heat transfer characteristics can be improved by optimizing the frequency, size, and the like of the vibration device.

In this case, when the frequency of the acoustic excitation device or the vibration device is matched with the eddy currents formed in the dimple, the heat transfer improvement effect is greatest, and the frequency is generally in the range of 1 to 2 St (stroul number).

Figure 14 shows the heat transfer distribution according to the change in the frequency (Stroul number) of the sound excitation at a constant 110dB sound pressure, showing the greatest heat transfer effect when the acoustic excitation frequency is 1.11 St, the effect gradually decreases as the frequency increases have.

FIG. 15 shows heat transfer distribution according to a change in sound pressure (SPL) in the same acoustic excitation frequency band (St = 1.1). As the sound pressure increases, the overall heat transfer effect is improved.

As described above, by designing a variety of vortex generators with protrusions, acoustic excitations, or vibrations in combination with dimples, the vortex flow can be actively controlled, and the combined thermal vortex generator improves the overall thermal performance of the heat exchanger. I can make it

The present invention is not limited to the above specific embodiments and descriptions, and various modifications can be made by those skilled in the art without departing from the gist of the invention as claimed in the claims. Such variations are within the protection scope of the present invention.

Claims (12)

Iii) dimples formed on the heat exchange surface of the flow path, and ii) projections for generating transverse vortices capable of reducing the stagnant flow area within the dimples.
The complex vortex generator according to claim 1, wherein the dimple and the protrusion are repeatedly formed on the heat exchange surface.
The complex vortex generating device according to claim 1, wherein the protrusion has a shape of rib turbulators.
The complex vortex generator according to claim 3, wherein the height ratio d _rib / H between the unevenness and the flow path is 0.05 to 0.15.
The apparatus of claim 1, wherein the protrusion has a delta wing shape.
The composite vortex generator according to claim 5, wherein the delta wing has an angle of 15 to 60 degrees.
The composite vortex generator according to claim 5, wherein the height ratio (d _dw / H) of the delta wing and the flow path is 0.3 to 0.5.
The complex vortex generator according to claim 5, wherein a depth ratio (d _dim / H) of the dimple and the flow path is 0.2 to 0.4.
Iii) a dimple formed on the heat exchange surface of the flow path, and ii) an acoustic excitation or vibration unit for generating a transverse vortex that can reduce the stagnant flow area in the dimple.
10. The complex vortex generator according to claim 9, wherein the frequency of the acoustic excitation section or the vibration section matches the vortex frequency formed in the dimple.
11. The complex vortex generator according to claim 10, wherein the frequency is 1 to 2 St (stroul numbers).
A heat exchanger comprising the composite vortex generator according to any one of claims 1 to 11.

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