BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the present apparatus and method can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present apparatus and method. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
FIG. 1 is a longitudinally cross-sectional view of a heat pipe in accordance with a first embodiment of the present invention;
FIG. 2 is a transversely cross-sectional view of the heat pipe in accordance with the first embodiment of the present invention;
FIG. 3 is a longitudinally cross-sectional view of a heat pipe in accordance with a second embodiment of the present invention;
FIG. 4 is a longitudinally cross-sectional view of a heat pipe in accordance with a third embodiment of the present invention; and
FIG. 5 is a longitudinally cross-sectional view of a heat pipe in accordance with related art.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates a heat pipe in accordance with a first embodiment of the present invention. The heat pipe comprises a casing 100 and a composite capillary wick (not labeled) arranged on an inner wall of the casing 100. The casing 100 comprises an evaporating section 400 at one end and a condensing section 600 at an opposite end thereof, and a central section (i.e., adiabatic section) 500 located between the evaporating section 400 and the condensing section 600. The casing 100 is made of highly thermally conductive materials such as copper or copper alloys and filled with a working fluid (not shown), which acts as a heat carrier for carrying thermal energy from the evaporating section 400 to the condensing section 600. Heat that needs to be dissipated is transferred firstly to the evaporating section 400 of the casing 100 to cause the working fluid therein to evaporate. Then, the heat is carried by the working fluid in the form of vapor to the condensing section 600 where the heat is released to ambient environment; thus, the vapor condenses into liquid. The condensed liquid is then brought back via the composite capillary wick to the evaporating section 400 where it is again available for evaporation.
The composite capillary wick comprises a first type of capillary wick 200 made by a plurality of fine grooves and a second type of capillary wick 220 formed by a layer of meshed wick. The first type of capillary wick 200 is formed on the inner wall of the casing 100 through all of the evaporating, central and condensing sections 400, 500, 600 of the casing 100, and the second type of capillary wick 220 is arranged to be attached on the first type of capillary wick 200 at the evaporating and central sections 400, 500 of the casing 100 only. Accordingly, the condensing section 600 only has the first type of capillary wick 200, i.e., a plurality of fine grooves, while the central and evaporating sections 500, 400 have both the first and second types of capillary wicks 200, 220, i.e., a plurality of fine grooves and a layer of meshed wick, wherein the fine grooves surround the layer of meshed wick. The meshed wick is consisted of a fine mesh. The first type of capillary wick 200 extends in the lengthwise direction of the casing 10 and may be formed by mechanical machining. The capillary pore size of the first type of capillary wick 200 is larger than that of the second type of capillary wick 220 (see FIG. 2) so that the first type of capillary wick 200 at the central section 500 can provide a smaller flow resistance than the second type of capillary wick 220 at the central section 500. In addition, the second type of capillary wick 220 can provide a larger capillary force than the first type of capillary wick 200. By such design of a composite capillary wick at the evaporating section 400 and the central section 500, the condensed liquid can be quickly drawn back to the evaporating section 400 from the condensing section 600 via the central section 500.
In this embodiment, the composite capillary wick has different types of capillary wick disposed in different sections of the heat pipe. The first type of capillary wick 200 has a relatively large average capillary pore size and therefore provides a relatively low flow resistance to the condensed liquid to flow therethrough, and meanwhile, the second type of capillary wick 220 has a relatively small average capillary pore size and accordingly develops a relatively large capillary force to the liquid. As a result, the first type of capillary wick 200 reduces the flow resistance the condensed liquid encounters when flowing through the condensing and central sections 600, 500, and the second type of capillary wick 220 has a large capillary force and therefore the liquid is then rapidly drawn back to the evaporating section 400 from the central section 500. The condensed liquid is returned back from the condensing section 600 in an accelerated manner. After the condensed liquid is returned back to the evaporating section 400, a next phase-change cycling will then begin. Thus, as a whole, the cycling of the working fluid is accelerated and therefore the total heat transfer capacity of the heat pipe is enhanced.
FIG. 3 illustrates a heat pipe in accordance with a second embodiment of the present invention. Main differences between the first and second embodiments are that in the second embodiment a sintered-type wick 210 is arranged on the first type of capillary wick 200 at the evaporating section 400 of the casing 100 instead of the second type of capillary wick 220. The first type of capillary wick 200 surrounds the sintered-type wick 210. Metal or ceramic powders are filled into the grooves of the first type of capillary wick 200 at the evaporating section 400 and sintered to form the sintered-type wick 210. Filling the powders into the grooves of the first type of capillary wick 200 at the evaporating section 400 can change the capillary pore size of the first type of capillary wick 200 so as to form a small pore size structure in the first type of capillary wick 200 at the evaporating section 400. The combined first type of capillary wick 200 and the sintered-type wick 210 at the evaporating section 400 can develop a very large capillary force to draw the condensed liquid from the condensing and central sections 600, 500 back to the evaporating section 400.
FIG. 4 illustrates a heat pipe in accordance with a third embodiment of the present invention. Main differences between the third and second embodiments are that in the third embodiment the second type of capillary wick 220 is arranged on the sintered-type wick 210 at the evaporating section 400 of the casing 100 and connects with the second type of capillary wick 220 at the central section 500. An arrangement of the first type of capillary wick 200, the sintered-type wick 210 and the second type of capillary wick 220 is that the first type of capillary wick 200 surrounds the sintered-type wick 210, which in turn surrounds the second type of capillary wick 220. The capillary pore size of the composite capillary wick at the evaporating section 400 is gradually increased along an inward direction from the first type of capillary wick 200 toward the second type of capillary wick 220.
In the present invention, it is feasible that any other type of capillary wick with smaller pore size, such as a beehive-type capillary wick can be disposed on the first type of capillary wick 200 at the central and the evaporating sections 500, 400 of the casing 100 to form the composite wick structure.
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.
Patent Application
20070240858
