Heat pipe made of composite material and method of manufacturing the same   

Abstract: The heat pipe made of composite material is a sealed hollow tube being a multilayer structure made of a composite material including copper and aluminum, is filled with water and has an inner surface, an evaporator end, a condenser end and a wick. The wick is attached to the inner surface of the tube. The invention provides a cost effective and lightweight heat pipe as it uses aluminum, which is cheap and light in weight. Also, the invention provides a high performance heat pipe system as it uses copper, which is highly thermally conductive. Therefore, the heat pipe is desirable for thermal management applications in a variety of products.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat pipe, and more particularly to a heat pipe made of copper and aluminum for high performance and less weight and manufacturing cost.

2. Description of the Prior Arts

Heat pipes provide very high conductivity for transmitting heat and are used in thermal management applications in a variety of systems and products. With reference to FIG. 10, a conventional heat pipe is a sealed hollow tube 20, is filled with water 24, is evacuated to lower an evaporation temperature of the water 24 and has an inner surface, an evaporator end 21, a condenser end 22 and a wick 23. The wick 23 is attached to the inner surface of the tube 20.

The heat pipe works on a principle of evaporative cooling of the water 24. The evaporator end 21 absorbs heat from a heat source and transfers the heat to the water 24. The water 24 absorbs the heat and evaporates to form vapor. The vapor flows to the condenser end 22 in a direction of arrows d1, dissipates the heat to cooling components (e.g. fins) and then condenses to form droplets. The condensed water 24 flows back to the evaporator end 21 in a direction of arrows d2 due to capillary force exerted by the wick 23. Thereby, the water 24 is circulated in the tube 20 and transfers heat from the evaporator end 21 to the condenser end 22.

One kind of the conventional heat pipe is made of a high thermal conductivity material such as copper. However, copper has a density of 8.92 grams per cubic centimeter and that results in a relatively heavy weight of the heat pipe. Besides, copper is an expensive metal and thus results in a high cost of the heat pipe. Another kind of the conventional heat pipe is made of a lighter and less costly material such as aluminum. However, aluminum gets corroded when it comes in contact with water over time. Further, aluminum and water react to generate hydrogen gas which gets accumulated inside the heat pipe as a non-condensable gas. This results in a significant loss in performance of the heat pipe. Accordingly, heat pipes with both less weight and manufacturing cost and high performance are needed.

To overcome the shortcomings, the present invention provides a heat pipe made of composite material to mitigate or obviate the aforementioned problems.

SUMMARY

The main object of the present invention is to provide a heat pipe made of copper and aluminum for high performance and less weight and manufacturing cost.

To achieve the foregoing objective, the heat pipe made of composite material in accordance with the present invention is a sealed hollow tube being a multilayer structure made of a composite material including copper and aluminum, is filled with water and has an inner surface, an evaporator end, a condenser end and a wick. The wick is attached to the inner surface of the tube. The invention provides a cost effective and lightweight heat pipe as it uses aluminum, which is cheap and light in weight. Also, the invention provides a high performance heat pipe system as it uses copper, which is highly thermally conductive. Therefore, the heat pipe is desirable for thermal management applications in a variety of products.

Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view in partial section of a first embodiment of a heat pipe made of composite material in accordance with the present invention;

FIG. 2 is a cross sectional front view of the heat pipe made of composite material in FIG. 1;

FIG. 3 is a cross sectional front view of a second embodiment of a heat pipe made of composite material in accordance with the present invention;

FIG. 4 is a cross sectional front view of a third embodiment of a heat pipe made of composite material in accordance with the present invention;

FIG. 5 is a cross sectional front view of a fourth embodiment of a heat pipe made of composite material in accordance with the present invention;

FIG. 6 is a cross sectional front view of a fifth embodiment of a heat pipe made of composite material in accordance with the present invention;

FIG. 7 is a cross sectional front view of a sixth embodiment of a heat pipe made of composite material in accordance with the present invention;

FIG. 8 is a cross sectional front view of a seventh embodiment of a heat pipe made of composite material in accordance with the present invention;

FIG. 9 is a flow diagram of a method of manufacturing a heat pipe made of composite material in accordance with the present invention; and

FIG. 10 is a side view in partial section of a conventional heat pipe in accordance with the prior art.

DETAILED DESCRIPTION

With reference to FIGS. 1 and 2, a heat pipe made of composite material in accordance with the present invention is a sealed hollow tube 10 being a multilayer structure made of a composite material, is filled with water 13, is evacuated to lower an evaporation temperature of the water 13 and has an inner surface, an evaporator end 11, a condenser end 12 and a wick 16. The composite material includes a high thermal conductivity material such as copper and a lighter and less costly material such as aluminum. The wick 16 is attached to the inner surface of the tube 10.

In a first embodiment, the tube 10 comprises an inner layer 14 and an outer layer 15. The inner layer 14 is made of copper. The outer layer 15 is made of aluminum and is clad around the inner layer 14 using a method such as diffusion bonding or press fitting. The wick 16 is attached to an inner surface of the inner layer 14.

With reference to FIG. 3, in a second embodiment, the tube 10A comprises an inner layer 14A, a mid layer 17A and an outer layer 15A. The inner layer 14 is made of copper. The mid layer 17A is made of aluminum and is clad around the inner layer 14A using a method such as diffusion bonding or press fitting. The outer layer 15A is made of copper and is clad around the mid layer 17A using a method such as diffusion bonding or press fitting. The wick 16A is attached to an inner surface of the inner layer 14A.

The wick 16 may be a screen mesh wick, a groove wick or a fiber wick. FIGS. 4 to 8 show various embodiments of the wick 16. With reference to FIG. 4, the wick 16B is a screen mesh wick and has a mesh structure mounted around the inner surface of the inner layer 14B. With reference to FIG. 5, the wick 16C is a groove wick and has multiple axial grooves. The grooves of the wick 16C are formed around the inner surface of the inner layer 14C and are rectangular in cross section. With reference to FIG. 6, the wick 16D is a groove wick and has multiple axial grooves. The grooves of the wick 16D are formed around the inner surface of the inner layer 14D and are triangular in cross section. With reference to FIG. 7, the wick 16E is both a screen mesh wick and a groove wick and has multiple axial grooves and a mesh structure. With reference to FIG. 8, the wick 16F is a fiber wick and has a fiber wick structure mounted around the inner surface of the inner layer 14F.

With reference to FIG. 1, when the heat pipe is in operation, the evaporator end 11 contacts a heat source and the condenser end 12 contacts cooling components. The water 13 absorbs heat at the evaporator end 11 and gets evaporated to form vapor. The vapor flows to the condenser end 12 in a direction of arrows D1, dissipates the heat to the cooling components and then condenses to form droplets. The condensed water 13 flows back to the evaporator end 11 in a direction of arrows D2 due to capillary force exerted by the wick 16. In this manner, the heat transfer effect is achieved.

The present invention provides a high performance, cost effective and lightweight heat pipe as it uses both copper and aluminum. Therefore, the heat pipe is desirable for thermal management applications in a variety of electronics products such as notebook computers, desktop computers, servers, LEDs, etc.

With reference to FIG. 9, a method of manufacturing a heat pipe made of composite material in accordance with the present invention comprising:

Step 1. Forming a tube: an outer layer is clad around an inner layer using a method such as diffusion bonding or press fitting to form a tube with a multilayer structure.

Step 2. Cutting and cleaning the tube: the tube is cut to a desirable length and is cleaned.

Step 3. Attaching a wick: a wick is attached to an inner surface of the inner layer to provide capillary force and one end of the tube is sealed thereafter.

Step 4. Evacuating the tube: the tube is evacuated.

Step 5. Filling water: water is filled into the tube and the other end of the tube is sealed thereafter.

Step 6. Subsequent processing: the tube is flattened to have a rectangular cross-section or the tube is bended to form a desirable shape corresponding to a product that needs to be cooled.

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 features of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, 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.