Patent Application
20070074521
The present invention relates generally to a heat dissipation device, and more particularly to a method for making the heat dissipation device having a vacuum chamber and a working fluid therein, such as a heat pipe, a vapor chamber-based heat spreader, a liquid cooling system, a refrigeration system and the like. The present invention relates also to an apparatus for making such a heat dissipation device.
Currently, in order to efficiently remove heat from heat generating electronic components such as central processing units (CPUs) of computers, fluid-containing heat dissipation devices such as heat pipes, vapor chamber-based heat spreaders, liquid cooling systems, refrigeration systems and the like, are widely used. As a common characteristic, these heat dissipation devices contain therein a working fluid, such as water, and employ the working fluid as a heat transfer medium. When such a fluid-containing heat dissipation device operates, the working fluid contained therein, either undergoing a phase change or not, continuously takes heat away from a heat generating electronic component with which the heat dissipation device thermally contacts.
To ensure normal and efficient operations, it is desirable to make the heat dissipation device free from non-condensable air because non-condensable air remaining in the heat dissipation device will produce an adverse or negative effect which may either affect the heat dissipation efficiency of heat dissipation device or cause damage to the components of the heat dissipation device.
For example, in a liquid cooling system in which a coolant such as water is driven by a pump so as to circulate through the system, or in a refrigeration system in which a refrigerant such as Freon-12 is driven by a compressor, non-condensable air in the liquid cooling system or the refrigeration system will induce cavitations on the impeller of the pump or the compressor when the impeller rotates at a high speed, which will impair the heat dissipation efficiency of the liquid cooling system or the refrigeration system, and/or even cause damage to the pump or the compressor. In a heat pipe or a vapor chamber-based heat spreader, which includes an evaporating section/region and a condensing section/region, non-condensable air in the heat pipe or the vapor chamber-based heat spreader will form a barrier preventing heat transfer from a heat source to working fluid in the evaporating section/region, which in turn decreases the heat transfer capability of the heat pipe or the heat spreader.
Furthermore, as the working fluid circulates or flows quickly in the heat dissipation device, non-condensable air remaining in the heat dissipation device also accelerates the flow-induced erosion and corrosion associated with the components of the heat dissipation device, as well as the pipes interconnecting these components, which significantly affects the life-span of the heat dissipation device.
In order to fill a predetermined amount of working fluid into the heat dissipation device and meanwhile remove the non-condensable air from the same, a method involving the following steps is proposed. First, the predetermined amount of working fluid is filled into the heat dissipation device. After that, the non-condensable air originally in the heat dissipation device is pumped out.
In the foregoing method, the working fluid is filled into the heat dissipation device before the non-condensable air in the heat dissipation device is pumped out. Therefore, it is easy to lead to the problem that a portion of the previously filled working fluid will also be inadvertently pumped out during the following air-pumping step. This problem is especially easy to occur in the circumstances where a relatively high vacuum degree is desirable in the heat dissipation device. As a result, this method generally cannot effectively remove the non-condensable air from the heat dissipation device without the risk of reducing the amount of working fluid that is finally sealed within the heat dissipation device. The foregoing method generally is undesirable or inapplicable for use in making a heat pipe since even a little reduction of the amount of the working fluid sealed within the heat pipe will affect the heat transfer performance of the heat pipe significantly.
Therefore, it is desirable to provide a method of removing non-condensable air from a fluid-containing heat dissipation device, which overcomes the foregoing disadvantages. It is also desirable to provide an apparatus for carrying out the method.
The present invention relates, in one aspect, to a method of removing non-condensable air from a heat dissipation device in which a working fluid is contained. Such a heat dissipation device includes, but is not limited to, heat pipe, vapor chamber-based heat spreader, liquid cooling system and refrigeration system. The method includes the following steps: pumping the non-condensable air out of the heat dissipation device through an opening thereof; measuring a vacuum degree of an interior of the heat dissipation device; filling a predetermined amount of working fluid into the heat dissipation device through the opening when the interior of the heat dissipation device reaches a predetermined vacuum degree; and sealing the opening of the heat dissipation device.
The present invention relates, in another aspect, to an apparatus used for removing the non-condensable air from, and filling the predetermined amount of working fluid into, the heat dissipation device. The apparatus includes: a vacuum pump for pumping the non-condensable air originally in the heat dissipation device out of the heat dissipation device, a vacuum gauge for detecting the vacuum degree formed inside the heat dissipation device by the vacuum pump, and a fluid-storage tank containing therein the predetermined amount of working fluid. The fluid-storage tank is adapted for filling the predetermined quantity of working fluid into the heat dissipation device after the detected vacuum degree inside the heat dissipation device reaches the predetermined value.
Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which:
A heat pipe is a heat transfer device having an elongated configuration in which a wick structure is provided, with the filled working fluid being saturated in the wick structure. The heat pipe transfers heat continuously from an evaporating end to a condensing end thereof as the working fluid contained therein undergoes a phase change and travels between the two ends. A vapor chamber-based heat spreader has a similar structure and working principle with the heat pipe, except that the heat spreader generally has a plate-type configuration, making it particularly advantageous in transferring heat from a concentrated heat source uniformly to a large heat dissipation surface such as a heat sink base. A liquid cooling system generally includes a heat absorbing member, a heat dissipating member and a pump used for driving the filled working fluid to circulate between the heat absorbing member and the heat dissipating member. As with a refrigeration system, it generally includes an evaporator, a condenser and a compressor used for driving the working fluid to circulate between the evaporator and the condenser. The working fluid in the refrigeration system evaporates into vapor at the evaporator. The vapor flows towards the compressor, and after being compressed at the compressor, the resultant high pressure vapor flows towards the condenser where the vapor is condensed into liquid, which is then returned back to the evaporator.
The apparatus 20 includes a vacuum pump 22, a fluid-storage tank 24 and a vacuum gauge 26. The vacuum pump 22 is used to remove the non-condensable air as originally contained in the heat dissipation device 10. The fluid-storage tank 24 stores therein a predetermined quantity of working fluid, which is intended to fill into the heat dissipation device 10. In most cases except the refrigeration system, the working fluid used for the heat dissipation device 10 is water although other working fluid such as methanol, ammonia and the like may also be suitable, based on specific requirements of the heat dissipation device 10. In the refrigeration system, Freon-12 is used. In the present embodiment, a connection pipe 28 having first, second and third branches 282, 284, 286 is provided in order to connect the components (i.e., the vacuum pump 22, the fluid-storage tank 24 and the vacuum gauge 26) of the apparatus 20 with the heat dissipation device 10. Specifically, the heat dissipation device 10 has an opening 12. The connection pipe 28 is connected with the opening 12 of the heat dissipation device 10, while the vacuum pump 22, the fluid-storage tank 24 and the vacuum gauge 26 are connected at the first, second and third branches 282, 284, 286 of the connection pipe 28, respectively. A valve 283 is provided at the first branch 282 so that the vacuum pump 22 can be maintained in fluid communication with the connection pipe 28 selectively as the valve 283 is switched on or off. Similarly, a valve 285 is provided at the second branch 284 and a valve 287 at the third branch 286 for respectively permitting the fluid-storage tank 24 and the vacuum gauge 26 to establish fluidic communications with the connection pipe 28 selectively. The connection pipe 28 is provided with a valve 289, which selectively controls the fluid communication between the heat dissipation device 10 and the apparatus 20 as switched between on and off.
In operation, the connection pipe 28 is hermetically connected to the opening 12 of the heat dissipation device 10. The valves 283, 287, 289 are turned on, and the vacuum pump 22 operates to pump out the non-condensable air originally in the heat dissipation device 10. At this moment, the vacuum gauge 26 is used to measure a vacuum degree in the heat dissipation device 10 caused by the vacuum pump 22. After an interior of the heat dissipation device 10 reaches, as measured by the vacuum gauge 26, the predetermined vacuum degree, the valves 283, 287 are turned off. Then, the valve 285 is turned on, and the predetermined quantity of working fluid previously stored in the fluid-storage tank 24 is accordingly sucked into the heat dissipation device 10 due to the presence of vacuum condition in the heat dissipation device 10. Immediately thereafter, the valves 285, 289 are turned off, and the opening 12 of the heat dissipation device 10 is hermetically sealed by, for example, a soldering process. As a result, the heat dissipation device 10 is vacuum-sealed with the predetermined quantity of working fluid therein.
As indicated above, the non-condensable air in heat dissipation device 10 is firstly withdrawn and then the working fluid for the heat dissipation device 10 is filled into the heat dissipation device 10. In this order, the problem in relation to the conventional art that the previously filled working fluid will be inadvertently pumped out of the heat dissipation device in the following air-pumping step is effectively eliminated. The heat dissipation device 10 is sealed with a precise amount of working fluid therein. The non-condensable air in the heat dissipation device 10 can be effectively removed by the vacuum pump 22 before the working fluid contained in the fluid-storage tank 24 is filled into the heat dissipation device 10.
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, 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200510100055.0 | Sep 2005 | CN | national |
