WO2013153486A1

WO2013153486A1 - Heat sink

Info

Publication number: WO2013153486A1
Application number: PCT/IB2013/052666
Authority: WO
Inventors: Lieven Raf Roger Desmet; Bram KNAAPEN
Original assignee: Koninklijke Philips N.V.
Priority date: 2012-04-10
Filing date: 2013-04-03
Publication date: 2013-10-17

Abstract

The present invention relates to a heat sink attached to a heat-generation device for dissipating heat therefrom. The heat sink comprises a plurality of air flow channels, wherein at least two air flow channels are mutually connected so that at least portion of the air flow entering a first air flow channel can be directed to a second air flow channel. The main advantage of this invention is that a higher efficiency in heat dissipation can be obtained.

Description

HEAT SINK

FIELD OF THE INVENTION

The present invention generally relates to a heat sink, especially to an illumination device attaching such a heat sink.

BACKGROUND OF THE INVENTION

Heat sinks are at present widely used in electronic equipment, mainly in the areas of displays and microprocessor cooling in desktop computers and laptops. They usually appear in the form of a 2D rectangular patterned block of aluminum or copper metal. The resulting fins add to the cooling capacity of the heat sink because of the increased metal surface exposed to air.

Heat sinks can work in a passive way or an active way, depending on whether the intended cooling happens through natural air convection of the heated air at the fins, or in turn actively by forced air flow resulting from the use of an additional fan.

Present heat sinks often lack aesthetical appearance, and are often used with forced air convection by the aid of a fan for better cooling.

For cost reasons, the use of a fan in a luminaire is normally to be avoided. Its electrical power consumption lowers the overall system efficacy and its mechanical moving parts constitute a challenge in robustness to achieve a long luminaire lifetime.

Therefore, the focus for thermal management in outdoor luminaires lies on passive cooling structures. Often the heat sink is integrated with the lamp/luminaire housing and is limited to a set of flat metal ribbons. From an aesthetical point such a design is often not very appealing to the eye.

The heat management of LED type of outdoor luminaires is more critical than lamp based luminaires. This is because LEDs do not directly radiate their heat away in the form of infrared radiation, but rather need to be cooled by conduction at the substrate level. It is therefore suggested that LEDs are mounted closely to a heat sink. US PAT. No. 7766514B2 discloses a cylindrical LED lamp with high heat-dissipating capacity, however, the cylindrical structure only works optimally if the air flow happens close to the axial direction. At least half of the cylindrical structure will not cool well if the air flow (wind) is coming from one side of the cooling structure (which in practice is always the case). Then more than half of the cooling structure will not profit from the air flow since the openings of the air channels are not facing the air flow direction to get the air in. Moreover, if you consider a random point in space within the air channels of cooling structure, since there are no openings in the connecting ribs between adjacent air channels, air flow directions are limited.

Hence, it is desiderated to improve the current heat-dissipating structure design. SUMMARY OF THE INVENTION

One object of the present invention is to provide a heat sink which facilitates air convection.

In order to achieve this object, according to some embodiments of the present invention, it provides a heat sink attached to a heat-generation device for dissipating heat therefrom. The heat sink comprises a plurality of air flow channels, wherein at least a first and a second air flow channels are mutually connected via at least one branch channel intersecting the two air flow channels, so that at least portion of the air flow entering any one of the first and the second air flow channels can be directed to another channel of the first and the second air flow channels via the at least one branch channel. The advantage is that both the two air flow channels can be used for thermal exchange, so as to improve the heat dissipation efficiency.

According to some embodiments of the present invention, at least one branch channel is formed by a hole on the wall between two adjacent air flow channels. Alternatively, it is practical to have more than one branch channels intersecting two adjacent air flow channels. It is also possible that one branch channel intersects three or more air flow channels, especially when a plurality of holes respectively formed on a plurality of walls among these air flow channels are arranged in a straight line and form a branch channel. In the embodiments of the present invention, the term "branch channel" is used to depict the channel intersecting two or more air flow channels, which should NOT be interpret to limit the size, orientation, shape and other characters of a channel which allows air flow through it.

According to some embodiments of the present invention, the plurality of air flow channels are configured to direct at least portion of the air flow entering the first air flow channel to a third air flow channel not adjacent to the first air flow channel, at least via the at least one branch channel. In some embodiments, the third air flow channel may be arranged at an opposite position or a diagonal position comparing to the position of the first air flow channel. The basic idea of these set of embodiments is allowing the air flowing through several air channels which may be spatially arranged far from each other, and the air or at least of the air flows via one or more branch channels.

According to some embodiments of the present invention, a portion of air flow channels close to the heat-generation device has a smaller cross-section than a portion of air flow channels far away from the heat-generation device. This brings the benefit that the air flow channels or the branch channels far from the heat-generation device have more efficient heat dissipation than those air flow channels or branch channels close to the heat-generation device, which in turn further accelerates the air flow from those air flow channels or branch channels close to the heat-generation device to those air flow channels or branch channels far from the heat-generation device.

According to one exemplary embodiment of the invention, the plurality of air flow channels or at least portion of them are formed in the shape of crystal lattice or sponge.

According to one exemplary embodiment of the invention, the plurality of air flow channels are formed over at least three spatial directions such that air flow enters from one direction can be directed out from other directions.

According to one exemplary embodiment of the invention, the plurality of air flow channels have a profile of bio-mimicry shape. The bio-mimicry shape may be a natural coral or a natural sponge shape.

According to one exemplary embodiment of the invention, the plurality of air flow channels are rounded at a corner where they intersect.

According to one exemplary embodiment of the invention, the heat sink is manufactured by 2D-layer stacking and/or 3D printing and/or machine cutting/milling/drilling.

According to one exemplary embodiment of the invention, the heat sink is a single piece component made of metal. The metal is Al or Cu or Al-alloy or Cu-alloy.

The present invention also provides a luminaire comprising such a heat sink.

The main advantage of this invention is that a higher efficiency in heat dissipation can be obtained.

Though we take a lighting luminaire as an example for the heat-generation device, it should be appreciated that the proposed heat sink not only can be attached to a luminaire, but also can be attached to another heat-generation device, for example an outdoor electric or electronic device.

Other objects, advantages, and novel features of the present invention will be apparent from the following detailed description thereof with reference to the attached drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a functional schematic view of a heat sink according to one embodiment of the present invention with air flow channels constant in size and/or shape;

Figure 2 is a functional schematic view of a heat sink according to another embodiment of the present invention with a gradient in channel size with respect to a distance from an illumination device;

Figures 3-4 show two kinds of shapes of the heat sink according to two examples of the present invention. DETAILED DESCRIPTION OF THE PRESENT INVENTION

Using nature-inspired designs in the area of outdoor lighting could greatly enhance acceptance of using unnatural objects. This invention is in line with the trend of biomimicry: "a new science that studies nature's models and then imitates or takes inspiration from these designs and processes to solve human problems". In nature, trees and corals have evolved into structures optimally capable of exchange gasses (O₂ and CO₂). Even though this invention challenges a different problem they are related. For trees and corals the direction of the flow (of air and water) does not have an effect on the efficiency of the gas exchange and offer a motivation to design efficient organic heat-exchanging structures.

The basic idea of the present invention is to enhance the air flow within a plurality of air flow channels, especially via the branch channels intersecting the plurality of air flow channels. One more advantage benefit brought by some embodiments of the present invention is that the heat sink may be designed to toward a wide range of angles, even 360°, via the plurality of air flow channels facing different directions, so as to receive the air flow from different directions no matter how the heat-generation device placed, and further via the branch channels intersecting the plurality of air flow channels, the air flow enters into the heat sink from one direction and may be directed to some other air flow channels facing different directions and leave the heat sink via as many as air flow channels. The benefit is that the surface for heat dissipation can be greatly increased since a lot of air flow channels are involved into air convection, even some of these air flow channels are not arranged toward the nature air flow.

In some embodiments of the present invention, it is proposed a 3D sponge-like or crystal-lattice shaped heat sinks for augmented cooling of outdoor lighting (LED) luminaires by taking advantage of natural convective cooling induced by environmental air flow (wind). The advantage of a sponge type of cooling structure is to maximally augment the cooling surface within a given 3D volume. Holes with a certain geometrical shape protrude or "blow through" the heat sink completely from one side to another. By arranging holes in all different directions, natural air flows (coming from any direction) will be allowed to flow less-hindered through the sponge heat sink, increasing the latter' s cooling capacity. Furthermore, aerodynamically design should allow for free air flow through the structure. This will keep the local air velocity high at the internal cooling surface areas and will result in better effective convective heat exchange to the air environment. Additionally to this functional heat sink design, the proposed sponge or crystal-like structure will enable luminaire heat sink/housing designs with high aesthetic quality, reflecting the natural evolution of organic structures that can be found in nature.

The spirit of the present invention will be detailed described hereafter with reference to the attached drawings.

Now please refer to Fig. 1 , which shows a functional schematic view of a heat sink 10 attached to a heat-generation device 3 for dissipating heat therefrom according to one embodiment of the present invention. The heat sink 10 includes a first heat dissipation part 1 attached to the heat-generation device 3 for dissipating the heat from the heat-generation device 3 and a second heat dissipation part 2 thermally coupled with the first heat dissipation part 1 for speeding up the dissipation of the heat from the illumination device 3.

The second heat dissipation part 2 includes a plurality of air flow channels 21 , wherein at least two air flow channels are mutually connected so that at least portion of the air flow entering a first air flow channel can be directed to a second air flow channel. Optionally, the plurality of air flow channels 21 are configured to direct at least portion of the air flow entering the first air flow channel to a third air flow channel located substantially at the opposite side of the first air flow channel. The first heat dissipation part 1 and the second heat dissipation part 2 can be a single piece component made of metal, such as Al or Cu or Al-alloy or Cu-alloy.

The plurality of air flow channels 21 are formed, in the shape of a crystal lattice (see Fig. 1), over three spatial directions such that air flow enters from one direction can be directed out from other directions. Optionally, the plurality of air flow channels are formed over four or more different spatial directions such that air flow can be performed in/along 4, 5, 6 or more different spatial directions. Optionally, almost all of the air flow channels or more than one half of the air flow channels are connected with one another spatially.

In practice, the heat sink is manufactured by 2D-layer stacking and/or 3D printing and/or machine cutting/milling/drilling.

Please refer to Fig. 2, which shows a functional schematic view of a heat sink 10 attached to a heat-generation device 3 for dissipating heat therefrom according to another embodiment of the present invention. The heat sink structure of Fig. 2 is similar to that of Fig. 1. The differences between Figs. 1 and 2 will be described as follows. In Fig. 2, a portion of air flow channels close to the heat-generation device 3 has a smaller cross-section than a portion of air flow channels far away from the heat-generation device; the air flow channels are varied in size and/or pitch and have a gradient in channel size with respect to the distance from the heat-generation device 3. Although the channel size shown in Fig. 2 is increasing gradually when the distance from the illumination device 3 increases, it should be noted that the channel size shown in Fig. 2 can also be decreasing gradually when the distance from the illumination device 3 increases.

Figures 3-4 show two kinds of shapes of the heat sink 10 according to two examples of the present invention. The second heat dissipation part 2 (or the overall the heat sink 10) is configured to have a sponge-like structure. The plurality of air flow channels 21 are formed in the shape of sponge (Fig. 3) or in a bio-mimicry shape, such as a coral (Fig. 4). Wherein a plurality of air flow channels 21 are formed over a plurality of spatial directions such that the heat-dissipating capacity of the heat sink is not affected when outside air flow direction is varied.

The present invention also provides a luminaire (not shown) (especially an outdoor luminaire) comprising such a heat sink.

The main advantages of this invention are that: a higher efficiency in heat dissipation can be obtained; the heat sink according our invention is aesthetical in appearance; and the heat-dissipating capacity of the heat sink is not affected when outside air flow direction is varied.

Though we take an illumination as an example for the heat-generation device, it should be appreciated that the proposed heat sink not only can be attached a luminaire, but also can be attached to other heat-generation device, especially an outdoor electric or electronic device.

It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, number, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

It should be noted that the abovementioned embodiments illustrate rather than limit the invention and that those skilled in the art would be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, the word "comprising" does not exclude the presence of elements or steps not listed in a claim or in the description. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. In the apparatus claims enumerating several units, several of these units can be embodied by one and the same item of hardware or software. The usage of the words first, second and third, et cetera, does not indicate any ordering. These words are to be interpreted as names. Further, in this context, and for the purposes of brevity and clarity, detailed descriptions of well-known methodologies have been omitted so as to avoid unnecessary detail and possible confusion.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A heat sink attached to a heat-generation device for dissipating heat therefrom, comprising:

a plurality of air flow channels,

wherein at least a first and a second air flow channels are mutually connected via at least one branch channel intersecting the two air flow channels, so that at least portion of the air flow entering the first air flow channel can be directed to the second air flow channel via the at least one branch channel.

2. The heat sink of claim 1 , wherein the least one branch channel comprises at least one hole in a wall between two adjacent air flow channels.

3. The heat sink of claim 1 or 2, wherein the plurality of air flow channels are configured to direct at least a portion of the air flow entering the first air flow channel to a third air flow channel not adjacent to the first air flow channel, at least via the at least one branch channel.

4. The heat sink of claim 1 or 2, wherein a portion of air flow channels close to the heat-generation device has a smaller cross-section than a portion of air flow channels far away from the heat-generation device.

5. The heat sink of claim 1 or 2, wherein the plurality of air flow channels are formed in the shape of a crystal lattice or a sponge.

6. The heat sink of claim 1 or 2, wherein the plurality of air flow channels are formed over at least three spatial directions such that air flow enters from one direction can be directed out from other directions.

7. The heat sink of claim 1 or 2, wherein the plurality of air flow channels have a profile of bio-mimicry shape.

8. The heat sink according to claim 1 or 2, wherein the heat sink is manufactured by 2D-layer stacking and/or 3D printing and/or machine cutting/milling/drilling.

9. The heat sink according to claim 1 or 2, wherein the heat-generation device is an illumination device.

10. A luminaire comprising of the heat sink as claimed in any one of the preceding claims.