Patent Application
20070006994
The present invention relates generally to an apparatus for transfer or dissipation of heat from heat-generating components, and more particularly to a loop-type heat exchange device suitable for removing heat from electronic components.
As progress continues to be made in electronic industries, electronic components such as integrated circuit chips are produced to have more powerful functions while maintaining a unchanged size or even a smaller size. As a result, the amount of heat generated by these electronic components during their normal operations is commensurately increased, which in turn will adversely affect their workability and stability. It is well known that cooling devices are commonly used to remove heat from heat-generating components. However, currently well-known cooling devices such as heat sink plus cooling fan are no longer qualified or desirable for removing the heat from these electronic components due to their low heat removal capacity. Conventionally, increasing the rotation speed of the cooling fan and increasing the size of the heat sink are two approaches commonly used to improve the heat dissipating performance of the cooling device involved. However, if the rotation speed of the cooling fan is increased, problems such as large noise will inevitably be raised. On the other hand, by increasing the size of the heat sink, it will make the cooling device bulky, which contravenes the current trend towards miniaturization.
Currently, an advantageous mechanism for more effectively removing the heat from these electronic components and overcoming the aforementioned disadvantages is adopted, which is related to use of heat pipe technology. Heat pipes are an effective heat transfer means due to their low thermal resistance. A heat pipe is usually a vacuum casing containing therein a working fluid. Preferably, a wick structure is provided inside the heat pipe, lining an inner wall of the casing. The heat pipe has an evaporating section for receiving heat from a heat-generating component and a condensing section for releasing the heat absorbed by the evaporating section. When the heat is inputted into the heat pipe via its evaporating section, the working fluid contained therein absorbs the heat and turns into vapor. Due to the difference of vapor pressure between the two sections of the heat pipe, the generated vapor moves, with the heat being carried, towards the condensing section where the vapor is condensed into condensate after releasing the heat into ambient environment by, for example, fins thermally contacting the condensing section. Due to the difference of capillary pressure developed by the wick structure between the two sections, the condensate is then drawn back by the wick structure to the evaporating section where it is again available for evaporation.
In the heat pipe, however, there still exists a fatal drawback awaited to be overcome. The movement of the vapor is countercurrent to that of the condensate within the casing of the heat pipe. The movement of the vapor will, to a certain extent, produce a resistance to the flow of the condensate due to an interaction between the vapor and the condensate. This negative effect will lower down the speed of the condensate in supplying to the evaporating section of the heat pipe. If the condensate is not timely sent back to the evaporating section, the heat pipe will suffer a dry-out problem at that section.
In order to overcome the drawback of the conventional heat pipe, a loop-type heat exchange device has been proposed. The loop-type heat exchange device includes an evaporator, a condenser, a vapor conduit and a liquid conduit. The evaporator defines therein a chamber for containing a working fluid. The vapor and liquid conduits each are connected between the evaporator and the condenser by two individual pipes. Specifically, the working fluid in the evaporator evaporates into vapor after absorbing the heat from the heat-generating component, and the generated vapor then flows, via the vapor conduit, to the condenser where the vapor is condensed into condensate after releasing its latent heat of evaporation. The condensate then returns back to the evaporator via the liquid conduit to thereby be available again for evaporation, thus forming a heat transfer loop. One of the advantages of the loop-type heat exchange device in relation to the conventional heat pipe is that the vapor and the condensate move separately and do not interfere with each other.
In practice, however, many improvements still can be made on the design of the loop-type heat exchange device in order to exhibit its full advantages. For example, since both the vapor conduit and the liquid conduit are connected to the evaporator, if no effective mechanism is provided to prevent the vapor generated in the evaporator from moving backwards towards and entering into the liquid conduit, a situation that the vapor flows in the liquid conduit along a direction countercurrent to that of the condensate will happen. In this situation, the loop-type heat exchange device cannot have an optimal heat dissipation performance. Furthermore, the irregular movement of the vapor into the liquid conduit also produces significant resistance to the condensate to enter the evaporator, which will prevent the condensate from being supplied to the place where the evaporation of the working fluid is effectuated. If the condensate is not brought back to that place timely due to the influence of the vapor, a dry-out problem will accordingly be raised in the evaporator.
Therefore, it is desirable to provide a loop-type heat exchange device which overcomes the foregoing disadvantages.
The present invention relates to a loop-type heat exchange device for removing heat from a heat-generating component. The heat exchange device includes an evaporator, a condenser, a vapor conduit and a liquid conduit. The evaporator defines therein a chamber for containing a working fluid. The chamber is divided into two regions. The working fluid is capable of turning into vapor in the evaporator upon receiving the heat at one region of said chamber from the heat-generating component. Each of the vapor and liquid conduits is connected between the evaporator and the condenser. The vapor generated in the evaporator is capable of being transferred via the vapor conduit to the condenser and turning into condensate in the condenser upon releasing the heat carried by the vapor. The condensate is capable of being transferred via the liquid conduit to the evaporator. The heat exchange device further includes means formed on the evaporator for reducing an amount of vapor being accumulated in the other region of the chamber of the evaporator.
In one embodiment of the present heat exchange device, said means for reducing the amount of vapor being accumulated in the other region of the chamber of the evaporator is a cooling device thermally connected to the evaporator corresponding to that region. The cooling device may be a plurality of cooling fins connected to an outer surface of the evaporator. In an alternative embodiment, the evaporator includes a top cover and a bottom cover cooperating with each other to define the chamber of the evaporator and said means is a projected section from the bottom cover corresponding to the one region of the chamber of the evaporator. The cooling device is capable of condensing that portion of vapor having entered into the other region of the chamber and meanwhile maintaining a low temperature for that region. The projected section of the bottom cover is used to receive the heat from the heat-generating component and functions for reducing an amount of the heat to be conducted from the projected section to the remaining part of the bottom cover and finally to the other region of the chamber. On this basis, the vapor formed and accumulated in the other region of the chamber is reduced to a minimum amount and the unidirectional working fluid movement mechanism along the heat transfer loop established by the present heat exchange device is well followed, thus effectively taking the heat away from the heat-generating component.
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:
The evaporator 20 contains therein a working fluid (not shown). As heat from a heat source (not shown) is applied to the evaporator 20, the working fluid contained in the evaporator 20 evaporates into vapor after absorbing the heat. Then, the generated vapor flows, via the vapor conduit 30, to the condenser 40 where the vapor releases its latent heat of evaporation and is thus condensed into condensate. The condensate then returns back from the condenser 40, via the liquid conduit 50, to the evaporator 20 where it is again available for evaporation, thus forming a heat transfer loop. In the present heat transfer device 10, the movements of the vapor and the condensate are carried out respectively and separately in the vapor conduit 30 and the liquid conduit 50.
In the present heat exchange device 10, the condenser 40 is used to dissipate the heat carried by the vapor. Although the condenser 40 located between the vapor conduit 30 and the liquid conduit 50 is schematically shown in broken lines, it is well known by those skilled in the art that the condenser 40 may take various forms, including metal fins, cooling devices (typically including heat sinks and cooling fans), or liquid cooling systems. For example, if the vapor conduit 30 and the liquid conduit 50 are an integral pipe, as shown in
With reference to
Corresponding to the first and second sections 221, 223 of the bottom cover 220 of the evaporator 20, an interior of the chamber of the evaporator 20 is divided into two major regions, i.e., a liquid micro-channel region 231 and an adjacent evaporating region 232. The micro-channel region 231 is fully filled with the first wick structure 230. A portion of the first wick structure 230 extends from the micro-channel region 231 into a middle part of the evaporating region 232 between opposite front and rear sides of the evaporator 20 as viewed from
Preferably, a second wick structure 501 is arranged against an inner surface of the liquid conduit 50 in order to bring the condensate resulting from the vapor back from the condenser 40 to the evaporator 20 timely, as shown in
In operation, the protrusion 225 of the evaporator 20 is maintained into thermal contact with the heat source. Preferably, a layer of thermal interface material is applied over their contacting surfaces in order to reduce thermal resistance. The heat generated by the heat source is firstly transferred to the projected second section 223 of the bottom cover 220 and then to the evaporating region 232 of the chamber of the evaporator 20 to cause the working fluid contained in that region to evaporate into the vapor after absorbing the heat from the heat source. Since the micro-channel region 231 is filled with the first wick structure 230, the generated vapor then enters into the vapor-gathering section 233 for temporary storage. Thereafter, due to the difference of vapor pressure between the evaporator 20 and the condenser 40, the vapor accordingly goes into the vapor conduit 30 and moves towards the condenser 40. After the vapor releases its latent heat in the condenser 40 and turns into the condensate, the condensate is then rapidly drawn back to the micro-channel region 231 of the chamber of the evaporator 20 via the liquid conduit 50 due to the capillary force of the second wick structure 501. Since an inventory of working fluid in the evaporating region 232 is reduced due to the evaporation in that region, the condensate returned to the micro-channel region 231 is subsequently drawn to the evaporating region 232 for being available again for evaporation as a result of the capillary force developed by the first wick structure 230, thus forming the heat transfer loop for continuously and effectively removing the heat generated by the heat source. In the present heat exchange device 10, the working fluid takes the heat away from the heat source specially in the unidirectional, circular manner along the heat transfer loop, when the working fluid continuously undergoes phase transitions from liquid to vapor and then from vapor to liquid (condensate). Due to the presence of the first wick structure 230 in the micro-channel region 231, which is saturated by the condensate, the vapor generated in the evaporating region 232 is prevented from moving towards the micro-channel region 231 and proceeding therefrom to the liquid conduit 50.
In order to reduce an amount of vapor to be formed and accumulated in the micro-channel region 231, it is preferred to prevent the condensate returned to and stored in that region from being directly heated and evaporated into vapor, since the thus generated vapor will accumulate in that region and accordingly produce a large resistance to the flow of the condensate towards the evaporating region 232. If the condensate is not timely sent to the evaporating region 232 due to the resistance of the vapor accumulated in the micro-channel region 231, a dry-out problem will be raised in the evaporating region 232. On the other hand, the vapor accumulated in the micro-channel region 231 will also has the chance to enter into and march along the liquid conduit 50, which will disorder the heat transfer mechanism along the heat transfer loop established by the present heat exchange device 10. In the present heat exchange device 10, the heat coming from the heat source is directly transferred to the second, thicker section 223 of the bottom cover 220. The two-section design of the bottom cover 220 is aimed to reduce an amount of the heat from the heat source to be conducted from the second, thicker section 223 to the thinner first section 221 and finally to the micro-channel region 231 of the evaporator 20. Since the second, thicker section 223 has a larger thickness than the first section 221, the heat conducted laterally from the second, thicker section 223 towards the first section 221 is thus capable of being effectively reduced. As a result, the heat transferred from the first section 221 of the bottom cover 220 to the micro-channel region 231 of the evaporator 20 is also effectively reduced, and thus excessive vapor is prevented from being formed and accumulated in that region. The condensate temporarily stored in the micro-channel region 231 is accordingly capable of being timely supplied to the evaporating region 232.
Since the micro-channel region 231 is connected with the adjacent evaporating region 232, a portion of the vapor generated in the evaporating region 232 will “creep” from the evaporating region 232 into the micro-channel region 231 due to a large vapor pressure in the vapor-gathering section 233. That is, a specific amount of the vapor generated in the evaporating region 232 will gradually move towards and enter into the micro-channel region 231 due to the large vapor pressure. In addition, the temperature in the micro-channel region 231 will also gradually increase, subject to a relatively high temperature and a flow of the vapor in the evaporating region 232. Thus, in order to reduce the vapor to be brought into and accumulated in the micro-channel region 231 to a minimum amount, it is also preferred to lower the temperature in the micro-channel region 231. In the present heat exchange device 10, the metal fins 250 formed on the top and bottom covers 210, 220 of the evaporator 20 corresponding to the micro-channel region 231 are applied to directly condense that portion of vapor having crept into the micro-channel region 231 into condensate at that region and on the other hand to maintain a relatively low temperature for the micro-channel region 231. In practice, the metal fins 250 may be substituted with other cooling devices such as cooling fans or thermoelectric cooling devices. The metal fins 250 preferably have a low height and are integrally formed with the top and bottom covers 210, 220 so as to minimize the size of the evaporator 20.
In the present heat exchange device 10, the condensate resulting from the vapor after releasing its latent heat in the condenser 40 is sent back to the evaporator 20 for being available again for evaporation under the capillary force developed by the second wick structure 501 arranged in the liquid conduit 50. With respect to the evaporator 20, the two-section design of the bottom cover 220 and the presence of the metal fins 250 on both the top and bottom covers 210, 220 cooperatively maintain a low temperature for the micro-channel region 231 of the evaporator 20 and effectively reduce the amount of vapor to be formed and accumulated in that region, thus enabling the condensate returned to the evaporator 20 to be supplied from the micro-channel region 231 to the evaporating region 232 of the evaporator 20 timely and eliminating the potential dry-out problem occurring at the evaporating region 232. As a result, the unidirectional working liquid movement mechanism along the heat transfer loop established by the present heat exchange device 10 is well followed and the heat generated by the heat source is taken away effectively.
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 |
|---|---|---|---|
| 200510035934.X | Jul 2005 | CN | national |
