Field of Invention

The present invention relates to a system and method for fabricating heat transfer devices. In particular, the present invention relates to an in-line fabrication system and method for fabricating heat transfer devices, such as heat pipes.

Background

Currently, fabrications of sealed heat transfer systems that mostly rely on the temperature differences to transport the heat, such as heat pipes, pulsation heat pipes or the like, include either vacuum or vaporization, which are used for removing air /moisture from cavity of the heat pipes. The former relies mainly on vacuum pump to withdraw air from the cavity, and when the cavity reaches a desired vacuum level, the working fluid is injected into the cavity thereafter. Such vacuum process is generally carried out under a closed sealed environment. On the other hand, the later process first injects the working fluid into the cavity of the heat pipes, and thereafter, heats up the whole article (i.e. the heat pipe) to to the working fluid's boiling temperature to remove the air/moisture resided therein before the article is being sealed. After the aforementioned processes, the heat pipe is sealed tight to contain the working medium to form a heat pipe.

There exist various known drawbacks in these known systems. In the vacuum method, the currently available vacuum pumps are generally expensive, and require sophisticated systems to maintain and control the vacuum state during the fabrication process. During the filing and sealing process, due to the negative pressure, air back- flow often occurs. Further, the vacuum method is commonly not suitable for fabricating large size industrial used heat pipe. In addition, the vacuum method is not able to remove air that resided within the working medium and the material of the tube body effectively.

Vaporization method on the other hand is not able to accurately control the amount of working fluid to be filled within the heat pipe. It is also not able to effectively remove air that resided within the working medium and the material of the tube body effectively. Such method is not suitable for fabricating small size heat

Pipe- It is known that the heat transfer's performance can be affected by the quantity and the quality of the working medium contained in the heat pipe.

The above two methods are adapted for fabricating convection heat pipes that mainly uses the phase-change of the working medium to perform heat transfer. As the processes require a closed system to fabricate, therefore, fabrication throughput is limited to the size of the fabrication equipments. Further, none of the available system provides any form of pressure control over the working medium.

SUMMARY

In one aspect of the present invention, there is provided a method for fabricating a heat transfer device, having a sealed container containing working medium within its cavity. The method comprises providing a container having at least one opening; injecting (114) the working medium controlled at a predetermined condition that includes temperature and pressure; and sealing (116) the container entirely to enclose the working medium therein to form the heat transfer device.

In one embodiment, the working medium may be contained in a enclosed container before injecting into the containers through the at least one opening.

In another embodiment, the cavity of the container is in a positive pressure state.

In a further embodiment, the method further comprises pre-heating and pre- pressurizing the working medium within a enclosed container prior to injecting in the container. It is possible that the enclosed container is adapted to hold only a desired amount/volume of working medium for one heat transfer device.

In yet a further embodiment, the method further comprises pre-heating (112) the container to a predetermined temperature for exhausting air/moisture contained within a material of the container. The pre-determined temperature that heats up the container is lower than that of the desired temperature of the working medium.

In a further embodiment, the method further comprising preprocessing the container. The pre-processing of the containers may include cleaning and drying (102) the container; sealing (104) off the container with the at least one opening left opened; and inspecting (105) the container for leakage.

In yet a further embodiment, the method further comprises post-processing the heat transfer device. The post processing the heat transfer device further comprises cooling (122) the heat transfer device; heating (124) at least one portion of the heat transfer device; inspecting heat transfer performance of the heat transfer device by taking temperature readings on various portions of the heat transfer device; and grading (126) the heat transfer device based on the heat transfer performance of the heat transfer device, wherein the heat transfer performance is good when differences between the temperature readings is small. Preferably, the entire process is carried out at a positive pressure environment that does not require any vacuum suction.

In accordance with another aspect of the present invention, there is provided a fabrication system for fabricating a heat transfer device, wherein the system is adapted to carry out the aforesaid method.

In yet another aspect, there is provided the aforesaid method that comprises an in-line fabrication system.

BRIEF DESCRIPTION OF DRAWINGS

This invention will be described by way of non-limiting embodiments of the present invention, with reference to the accompanying drawings, in which:

FIG. 1 illustrates a flow diagram showing a heat transfer device fabrication process in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

In line with the above summary, the following description of a number of specific and alternative embodiments are provided to understand the inventive features of the present invention. It shall be apparent to one skilled in the art, however that this invention may be practiced without such specific details. Some of the details may not be described at length so as not to obscure the invention. For ease of reference, common reference numerals will be used throughout the figures when referring to the same or similar features common to the figures.

The present invention suggests a method and system for fabricating heat transfer devices, such as heat pipes. Understanding the relationship between the temperature and the pressure against the density of the material of the working medium, the method and system is able to ensure the desired amount of working medium be accurately dispensed and packed into the heat transfer device with minimal or no air and moisture presence.

FIG. 1 illustrates a flow diagram showing a heat transfer device fabrication process in accordance with one embodiment of the present invention. The fabrication process is adapted to fabricate heat transfer devices through an in-line fabrication system, which allows the fabrication to be carried out continuously. A typical heat transfer device comprises a sealed container containing working medium within its cavity. The container is typically made of heat conducting material or composition with good thermal conductivity. Copper and aluminum are good thermal conducting materials for the containers, though others may also be desired. The working medium is fluid, which serves as a heat carrier for the heat transfer device. It is selected generally based on an intended operating state of the heat transfer devices. The working medium can be fluid, i.e. either liquid or gas. The heat transfer device referred hereto does not necessarily refer to a heat transfer device where the working medium operationally changes its form (i.e. phase change) within the heat transfer device while transferring heat, such as a phase change heat pipe. It is apparent that the present invention is also applicable for fabricating any heat transfer devices that Y2009/000170

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function based on other phenomenon(s), such as a non-phase change heat transfer device.

Briefly, the process includes cleaning the container at step 102; sealing the container at step 104; inspecting the container for leakage at step 106; pre-heating the container at step 112; filing working medium into the container at step 114; sealing the container at step 116; cooling the heat transfer device at step 122; testing the heat transfer device at step 124; and grading the heat transfer device at step 126.

The steps 102 to 104 are pre-fabrication processing for processing the containers of the working medium. These processes can be included as part of the inline fabrication system or carried out separately, off the system. The containers can be a hollow tube form, a hollow panel form, a hollow block and many other forms that are known in the art. At the step 102, the containers are cleaned and washed through a high-pressure water jet, and then they are being forced-air dried accordingly. Once cleaned and dried, at the step 104, the containers are subjected to seal off opening(s) through any welding means but leaving at least one opening for injecting working medium there through. At step 106, the containers are subjected for leakage test before further fabrication. The containers with leakage will be rejected or recycled.

Following the pre-fabrication process, the containers are subjected to a preheat process at the step 112. The pre-heat process is carried out under a temperature- controlled environment within the in-line fabrication system. The containers are heated up to a pre-determined temperature to heat up air and moisture that remains within pores in the body of the containers and the cavity of the containers. The pre- determined temperature may vary according to selected material for the containers. A preheat control system may be provided in the in-line fabrication system to provide the temperature-controlled environment.

In the present context, the pre-heat process is meant to heat up the air within the pores of the material and cavity of the containers' body, so that the air is expanded into a lighter form where some of the air escapes from the cavity of the containers. The pre-heat process also evaporates the moisture that remains in the containers. A skilled person would understand that the heated air and the evaporated moisture would still remain in the containers (within the material and the cavity) in the absence of any forced-vacuum control or other similar means. The pre-heat process is carried out in a positive pressure environment.

At the step 114, the working medium is injected into the containers through the at least one opening. At this stage, the containers are substantially in the pre-heat condition. The working medium is controlled and maintained at a predetermined condition prior to injecting into the containers. The predetermined condition includes a predetermined temperature and pressure. The working medium under the predetermined condition is then injected into the containers through the at least one opening. As the heated air and vaporized moisture remains in the cavity of the containers are now in a lighter form, the working medium injected thereto expelled the heated air and vaporized moisture from the containers. With the relevant changes on the working medium under the predetermined conditioned being factored, a desired amount of the working medium injected in to the containers can be effectively controlled. Further, as the aforementioned air/moisture removal process does not involve any vacuum or suction process, the process is therefore carried out in a positive pressure environment, making the fabrication process possible on the in-line fabrication system.

In one embodiment, the in-line fabrication system comprises a enclosed container along the system for containing the working medium before injecting into the containers. The working medium is pre-heated and pre-pressurized within the enclosed container. One advantage of containing the working medium in the enclosed container is that the temperature and pressure can be more effectively controlled. It is possible that the closed containers are sized to hold only the desired amount/volume of working medium for one heat transfer device only. Further, the enclosed container allows the working fluid be controlled under a desired temperature and pressure without the need of having an sealed working environment, therefore, the in-lice fabricating system can be realized.

In an alternative embodiment the enclosed container may further connect to a reservoir for supplying the working medium. No temperature and pressure control is required for the working medium in the reservoir as the temperature and pressure of the working medium is already been controlled within the enclosed container. The reservoir provides continuous supplies of working medium to the fabrication process.

Once the containers are filled with the working medium of the desired temperature and pressure, the containers are sealed at step 116 to form the heat transfer devices. The containers can be sealed by any known welding means or the like, such as metal inert gas welding under argon environment. Once the containers are sealed with the working medium, the heat transfer devices are formed. The heat transfer devices are then subjected to a post-fabrication process, which includes the steps 122 to 126. Similarly, these processes can be included in the in-line fabrication system or carried out separately off the in-line system. At step 122, the heat transfer devices are being forced-cool, to a room temperature for example. At step 124, the heat transfer devices are being heated up to a corresponding working temperature for inspecting the heat transfer performance of each heat transfer device. It is possible that the heat transfer devices are heated up at one portion only in the heat transfer performance's inspection. Temperature readings on various portions of each heated heat transfer device are taken. Accordingly, the heat transfer devices are being graded at step 126 based on the heat transfer performance. The heat transfer performance can be determined based on differences between the temperature readings.

In a further embodiment, the in-line fabrication system is adjustable in width.

It is understood to a skilled person that the fabrication process of present invention can be used to fabricate all types of heat transfer devices, which include flat panel heat transfer devices.

The present invention discloses a system and method that address the existing drawbacks and limitations in the known heat transfer device fabrication process. With the present invention, the heat transfer device fabrication process can be carried out in an in-line fabrication system that allow high throughput in heat transfer devices manufacturing. The present invention allows a desired temperature, pressure and amount of the working medium dispensing into the heat transfer device be effectively controlled. The system is less complicated to implement and thereby operable at a relatively lower cost. It does not require heating continuously throughout the fabrication process. It provides a series of fabrication process including pre-heating of the pipe material until end product testing in an in-line fabricating system. The present invention is also not limited in size (length, diameter) of the heat transfer device, the pipe material, the type of working medium to carry out the fabrication process. The present invention is able to achieve high quality heat transfer device at a high success rate. The present invention not only addresses the existing problems exist in the known system and method, it can also be used to fabricate all types of heat transfer device, which includes non-phase heat transfer device.

While specific embodiments have been described and illustrated, it is understood that many changes, modifications, variations and combinations thereof could be made to the present invention without departing from the scope of the invention.