JP2019015433A - Heat transfer device - Google Patents

Abstract

To provide a heat transfer device which greatly changes heat transfer performance according to a flow rate of a heat transfer fluid.SOLUTION: A heat transfer device of the invention includes a heat transfer fluid and a passage of the heat transfer fluid. The passage has a vortex flow generation part in at least one part of its inner surface. In the vortex flow generation part, multiple recessed parts extending in a direction intersecting with a heat transfer fluid circulation direction are arranged at predetermined intervals. A contact angle of a surface of the vortex flow generation part and the heat transfer fluid is 110° or larger. Heat transfer is facilitated when the flow rate of the heat transfer fluid is high, and the heat transfer is inhibited when the flow rate of the heat transfer fluid is low.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat transfer device, and more particularly to a heat transfer device that generates a vortex flow in a heat transfer fluid.

  A cooling device that cools a heating element such as an electronic component by flowing a cooling medium is known. Patent Document 1 includes a plurality of heat radiating members that extend in a direction away from the electronic component. A cooling device that cools the heating element by passing a cooling fluid between members is described.

  The length of the plurality of heat dissipating members is formed to be shorter as the heat conduction temperature due to heat generation of the electronic component is lower, and even if the size is reduced, the pressure loss of the cooling fluid is suppressed and the cooling performance is maintained. be able to.

JP 2003-8264 A

  However, in a cooling device that improves the cooling performance by increasing the contact area between the cooling medium and the flow path component, the flow rate of the heat transfer fluid is reduced during warm-up, etc. Even when it is desired to raise the temperature up to the temperature, the cooling performance is high, so that excessive heat dissipation is performed and the cooling loss increases.

  This invention is made | formed in view of the subject which such a prior art has, The place made into the objective is to provide the heat-transfer apparatus from which the heat-transfer performance changes a lot with the flow volume of the fluid for heat-transfer. is there.

  As a result of intensive studies to achieve the above object, the present inventor provided a recess on the inner surface of the flow path of the heat transfer fluid to generate a vortex flow therein, and the surface of the recess, the heat transfer fluid, It has been found that the above-mentioned object can be achieved by setting the contact angle to a certain level or more, and the present invention has been completed.

That is, the heat transfer device of the present invention includes a heat transfer fluid and a flow path for the heat transfer fluid, and the flow path has a vortex flow generation portion on at least a part of its inner surface.
And the said eddy flow production | generation part has arrange | positioned the several recessed part extended in the direction which cross | intersects the distribution direction of the said heat transfer fluid at predetermined intervals, and the surface and the said heat transfer fluid The contact angle is 110 ° or more.

  According to the present invention, the vortex flow is generated in the recess of the vortex flow generation section, and the contact angle between the surface of the vortex flow generation section and the heat transfer fluid is set to 110 ° or more. It is possible to provide a heat transfer device that promotes heat transfer when the flow rate of fluid is high and suppresses heat transfer when the flow rate is slow.

It is a schematic sectional drawing when the heat transfer apparatus of this invention is cut | disconnected in the distribution direction of the fluid for heat transfer. It is a schematic plan view which shows an example when a vortex | eddy_current production | generation part is seen from the inside of a flow path. It is an expanded sectional view showing an example of a vortex flow generation part. It is an expanded sectional view of another vortex flow generation part. It is a schematic plan view when another vortex flow production | generation part is seen from the inside of a flow path. It is a schematic plan view when another vortex flow production | generation part is seen from the inside of a flow path. It is a schematic plan view when another vortex flow production | generation part is seen from the inside of a flow path. It is a schematic plan view when another vortex flow production | generation part is seen from the inside of a flow path. FIG. 2 is a cross-sectional view of a flow path at a location indicated by A-A ′ in FIG. 1. It is a graph which shows the relationship with the heat transfer rate with the thickness ((delta) s) of a laminar bottom layer. It is a figure which shows an example of the circulation path which circulates the fluid for heat transfer between a heat-transfer apparatus and an engine and a transmission. It is a figure which shows the other example of the circulation path which circulates the fluid for heat transfer between a heat-transfer apparatus and an engine and a transmission. It is a figure which shows the further another example of the circulation path which circulates the fluid for heat transfer between a heat-transfer apparatus and an engine and a transmission. It is a graph which shows the heat transfer rate with respect to the flow velocity of the fluid for heat transfer of an Example and a comparative example. It is a graph which shows the heat transfer rate of the Example in case a flow velocity is 0.5 m / s and 3.3 m / s, and a comparative example.

The heat transfer device of the present invention will be described in detail.
The heat transfer device includes a heat transfer fluid and a flow path through which the heat transfer fluid flows. If necessary, fins provided in contact with the outside of the flow path constituent material, And a flow rate control device for controlling the flow rate of the heat transfer fluid.
Further, at least a part of the inner surface of the flow path has a vortex flow generation section, and the flow of heat transfer fluid flowing through the flow path causes a vortex flow to be generated in the recess of the vortex flow generation section. Heat is exchanged between the working fluid and the flow path component, and the heat transfer fluid is cooled or heated.

FIG. 1 is a schematic cross-sectional view of the heat transfer device according to the present invention when cut in the flow direction of the heat transfer fluid, and FIG. 2 is a schematic plan view of a vortex flow generating section provided in the flow path of the heat transfer device. FIG. 3 is an enlarged cross-sectional view of the vortex flow generator surrounded by a circle in FIG.
The heat transfer fluid flows in the direction indicated by the arrow in FIGS. 1, 2, and 3.

  The vortex flow generating section is formed by arranging a plurality of elongated recesses, that is, grooves, extending in a direction intersecting with the flow direction of the heat transfer fluid at predetermined intervals. Then, a vortex flow is generated in the recess according to the flow rate of the heat transfer fluid flowing in the flow path, and the heat transfer fluid in the recess is discharged out of the recess to promote heat transfer. It is intended.

The contact angle between the surface of the vortex flow generating portion and the heat transfer fluid is 110 ° or more, so that heat transfer is promoted when the flow rate of the heat transfer fluid is high, and heat transfer is performed when the flow rate is low. It is suppressed.
In the present invention, the contact angle between the surface of the vortex flow generator and the heat transfer fluid refers to the contact angle between the surface and the heat transfer fluid when the vortex flow generator is flattened.

  The reason why the heat transfer performance largely changes depending on the flow velocity of the heat transfer fluid is not clarified, but is presumed as follows.

Since the surface of the vortex flow generating portion of the present invention has high liquid repellency with respect to the heat transfer fluid, the frictional resistance between the vortex flow generation portion surface and the heat transfer fluid is small when the flow velocity is low, and the heat transfer fluid generates the vortex flow. It flows smoothly without being dragged to the surface of the part. Therefore, the vortex flow in the recess is reduced, and the heat transfer fluid in the recess circulates in the recess without being discharged out of the recess. Heat transfer is suppressed.
On the other hand, when the flow velocity is high, the kinetic energy of the heat transfer fluid is superior to the liquid repellency of the surface of the vortex flow generating section, the vortex flow in the recess is increased, and the heat transfer fluid in the recess is discharged out of the recess. This is considered to be because heat transfer is promoted between the inside and outside of the recessed portion of the vortex flow generating portion.

  The groove shape of the vortex flow generating section is not particularly limited as long as vortex flow can be generated in the recess, and the groove has a polygonal shape such as a triangle or a quadrangle, or a groove depicting an arc such as a semicircle. Although it can mention, it is preferable that the cross section draws the circular arc.

  As shown in FIG. 3, when the cross section of the groove draws an arc, a large vortex flow is generated along the inner wall of the recess when heat transfer is promoted, so that the heat transfer fluid stays at the corner when the cross section is polygonal. Is prevented.

  As for the arrangement of the grooves, adjacent grooves may be arranged closely without gaps, or may be arranged with a gap between the grooves. Also, as shown in FIG. 4, it is preferable to connect the adjacent grooves with a smooth curve by bending the inner walls of the grooves without providing corners.

By connecting adjacent grooves with a smooth curved surface and forming a top portion between them with a curved surface, it is possible to suppress wear due to erosion and to easily process the vortex flow generating portion.
In addition, since the generation of cracks and chips in the mold can be suppressed and there are no corners, the average film thickness can be easily managed when a liquid repellent layer is formed on the surface.

In addition, the grooves intersecting with the flow direction of the heat transfer fluid may be provided by arranging a plurality of grooves shorter than the width of the flow path as shown in the plan view of the vortex flow generating section shown in FIG. It is preferable to be provided in the entire width direction of the flow path.
By providing a continuous groove over the entire width of the flow path, a vortex flow can be formed throughout the direction intersecting the flow direction of the flow path, and heat transfer is promoted.

  Moreover, the said groove | channel should just cross | intersect the distribution direction of the heat-transfer fluid, and as shown in the plan view of the vortex flow generating part shown in FIGS. The bent grooves may be arranged at an angle with the flow direction of the heat transfer fluid. However, as shown in the plan view of the vortex flow generator shown in FIG. It is preferable that the grooves are arranged in parallel.

Further, the relationship between the maximum depth (H) of the recess and the thickness (δs) of the laminar bottom layer (viscous bottom layer) represented by the following formula (1) is (H)> It is preferable that (δs) and (H) ≦ (δs) when heat transfer is suppressed.
Laminar bottom layer thickness (δs) = 63.5 / (Re7 / 8) × d Formula (1)
However, in Formula (1), Re represents the Reynolds number calculated by ud / v,
d is the representative length, u is the flow velocity, and v is the kinematic viscosity of the heat transfer fluid.

  The representative length d can be calculated from the minimum channel cross-sectional area A of the channel cross-section orthogonal to the flow direction of the heat transfer fluid and the maximum wetting slip length L, and d = 4 A / L. Desired.

FIG. 9 is a cross-sectional view of a portion indicated by AA ′ in FIG. 1 when the flow path is viewed from the flow direction of the heat transfer fluid.
The minimum flow path cross-sectional area A is a cross-sectional area of the flow path excluding the vortex flow generation section. In FIG. 9, the hatched portion surrounded by the outline T of the vortex flow generation section and the inner surface of the flow path. It is an area.
The wet wetting length L is the length of the entire circumference of the cross section of the flow path including the vortex flow generation section. In FIG. 9, the length of the inner circumference of the entire flow path including the bottom V of the vortex flow generation section. That's it.

  The laminar bottom layer (viscous bottom layer) is a region that is strongly influenced by the viscosity of the heat transfer fluid formed in the vicinity of the channel wall surface. In this region, the flow is close to the laminar flow. This is a region where the heat transfer rate is slow because the working fluid is not agitated and heat transfer is performed by heat conduction due to the temperature gradient.

  When the maximum depth (H) of the recess is larger than the thickness (δs) of the laminar bottom layer, the laminar bottom layer is interrupted by the vortex flow generation unit, and a vortex flow is generated in the recess to cause heat transfer Heat transfer performance is improved because of stirring.

  Moreover, it is preferable that the maximum depth (H) of the said recessed part is smaller than the diameter of the circle | round | yen which draws the circular arc of the inner wall of a recessed part. When the depth of the recess is smaller than the diameter of the circle that draws the arc, the inside of the recess is agitated by the vortex flow, and the vortex flow flows from the inside of the recess to the outside of the recess, thereby improving the heat transfer performance.

FIG. 10 shows the laminar bottom layer when the thickness of the laminar bottom layer is changed by changing the flow velocity of the three types of vortex flow generating portions having the shape shown in FIG. 3 with the groove depth (H) changed. The relationship between the thickness (δs) and the heat transfer coefficient is shown.
FIG. 10 shows that the heat transfer performance is improved when the maximum depth (H) of the recess is larger than the thickness (δs) of the laminar bottom layer.

The opening diameter W of the recess, that is, the width of the groove is preferably 0.2 mm to 5 mm, although it depends on the flow rate of the heat transfer fluid, the cross-sectional shape of the flow path, and the like. By being in the above range, the heat transfer performance can be greatly changed within a practical flow rate range.
In addition, the opening diameter W at the time of connecting adjacent grooves with a smooth curved surface means the space | interval between the adjacent top parts T, as shown in FIG.

  The vortex flow generating part can be formed by forming a desired groove in a metal material by pressing, cutting, casting, or the like, and then applying and drying a resin that repels the heat transfer fluid.

  Although there is no restriction | limiting in particular as said metal material, Aluminum, copper, or the alloy containing these metals has high heat conductivity, and can be used preferably.

Examples of the resin that repels the heat transfer fluid include silicone resins and fluorine resins.
The film thickness of the resin is preferably 5 nm to 50 μm and more preferably 5 nm to 20 μm from the balance between thermal conductivity and durability.
Since the resin has a lower thermal conductivity than that of a metal material, it is preferably thin from the viewpoint of improving heat transfer properties. However, if the resin is too thin, it may be difficult to obtain desired durability.

  As the heat transfer fluid, water, ethylene glycol, or a mixture thereof, as well as a lubricating oil can be used, and if necessary, an additive such as a rust inhibitor and an antifoaming agent is included. May be.

The flow rate of the heat transfer fluid can be controlled by adjusting the flow rate of the heat transfer fluid with a flow rate control device provided in the flow path.
Examples of the flow rate control device include a pump, a flow rate adjustment valve, and a flow rate distribution valve that allows a heat transfer fluid to flow in a bypass flow path.

  The heat transfer device of the present invention can be suitably used for cooling an internal combustion engine, cooling and heating a transmission, and the like. Specifically, as shown in FIGS. 11 to 13, the heat transfer device of the present invention circulates a heat transfer fluid between an internal combustion engine or a transmission and a heat transfer device, and heat transfer is performed by a flow rate control device. By adjusting the flow rate of the working fluid, the desired heat transfer performance can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to the following Example.

[Example 1]
The aluminum plate is press-molded to form a vortex flow generating portion having the shape shown in FIG. 3 in which grooves having a semi-circular cross section with a maximum depth (H) of 0.5 mm and an opening diameter of 1 mm are arranged. Was applied to prepare a flow path.

[Comparative Example 1]
A flow path was formed in the same manner as in Example 1 except that the fluororesin was not applied.

[Comparative Example 2]
Without forming a vortex flow generating part on a flat aluminum plate, a fluororesin was applied to produce a flow path.

[Comparative Example 3]
A flow path was formed in the same manner as in Comparative Example 2 except that the fluororesin was not applied.

<Measurement of contact angle>
The contact angle between the flow path surfaces of Comparative Example 2 and Comparative Example 3 and the heat transfer fluid was measured by the following method.
Using Contact Angle System OCA-20 (manufactured by Data Physics Co., Ltd.), 5 droplets of heat transfer fluid (water) were formed with a dispenser on a flat flow path component, and each contact angle was measured. The average value was calculated.
The contact angle of the flow path of Comparative Example 2 was 95 °, and the contact angle of the flow path of Comparative Example 3 was 135 °.

<Measurement of heat transfer characteristics>
The flow rate of the heat transfer fluid was changed, and the heat transfer coefficient for each flow rate was measured. The measurement results are shown in FIG. FIG. 15 shows the heat transfer coefficient when the flow velocity is 0.5 m / s and 3.3 m / s.

From FIG. 14, the heat transfer devices of Example 1 and Comparative Example 1 having the vortex flow generation unit promote heat transfer more than the heat transfer devices of Comparative Examples 2 and 3 having a flat flow path by increasing the flow velocity. You can see that
Further, in Example 1 in which the liquid repellent film is formed on the surface of the vortex flow generating portion, heat transfer is suppressed by slowing the flow rate as compared with Comparative Example 1 having no liquid repellent film. It can be seen that the heat transfer coefficient greatly changes due to the change of.

From FIG. 15, when the flow rate is high, the heat transfer coefficient does not change depending on the presence or absence of the liquid repellent film, but when the flow rate is low, a flat one that does not have the vortex flow generation unit is provided with a liquid repellent film. It can be seen that, while heat transfer is promoted, those having a vortex flow generation part are suppressed by providing a liquid repellent film, and the heat transfer rate is reversed.
It can also be seen that the contact angle is 110 ° or more and the heat transfer coefficient at the low flow rate is reversed, and the transfer is suppressed at the low flow rate.

1 Heat Transfer Device 1A Heat Transfer Device (Radiator)
1B Heat transfer device (cooling jacket)
2 flow path 21 vortex flow generation section 3 heat transfer fluid 4 fin 5 pump 6 flow rate control valve 7 detour flow path 8 flow distribution valve 9 engine 10 transmission 101 oil pan 102 oil warmer V bottom T top H depth W opening diameter (Groove width)

Claims (2)

A heat transfer device comprising a heat transfer fluid and a flow path,
The flow path has a vortex flow generation part on at least a part of its inner surface,
The vortex flow generator is formed by arranging a plurality of recesses extending in a direction intersecting with the flow direction of the heat transfer fluid at a predetermined interval, and a contact angle between the surface and the heat transfer fluid Is a heat transfer device characterized by being 110 ° or more. The relationship between the maximum depth (H) of the recess and the thickness (δs) of the laminar bottom layer represented by the following formula (1) is:
The heat transfer device according to claim 1, wherein (H)> (δs) is satisfied when heat transfer is promoted.
Laminar bottom layer thickness (δs) = 63.5 / (Re7 / 8) × d Formula (1)
However, in Formula (1), Re represents the Reynolds number calculated by ud / v,
d is the representative length, u is the flow velocity, and v is the kinematic viscosity of the heat transfer fluid.

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