Heat Exchange Tube and Manufacturing Method Therefor

Abstract

A heat exchange tube is used to solve the problem of insufficient heat exchange efficiency of the conventional heat exchange tube. The heat exchange tube includes a tube, a first porous layer, and a second porous layer. The tube includes an inner wall. The first porous layer includes a plurality of holes. The first porous layer is disposed on the inner wall of the tube. The second porous layer includes a plurality of holes. The second porous layer is disposed on an inner surface of the first porous layer. An average diameter of the plurality of holes of the second porous layer is greater than an average diameter of the plurality of holes of the first porous layer. A method for manufacturing a heat exchange tube is also disclosed.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchange tube for heat exchange and, more particularly, to a heat exchange tube used in a reboiler to vaporize a working fluid by heat exchange and a method for manufacturing the heat exchange tube.

2. Description of the Related Art

A reboiler is a heating equipment widely used in the petrochemical industry and is mainly used in refinement of products. In brief, the reboiler is mounted to a bottom of a still pot and is used to heat a working fluid in the still pot, such that the working fluid is vaporized to form an ascending vapor, thereby separating predetermined components from the working fluid by the phase change of the working fluid. A heat exchange tube (so-called “high flux tube”) is disposed in the reboiler, and the working fluid can pass through the heat exchange tube to carry out the above phase change.

Please refer to FIG. 1 showing a conventional heat exchange tube 9. The heat exchange tube 9 includes a plurality of channels 91 therein. The plurality of channels 91 is parallel to each other. The plurality of channels 91 extends axially in the inner wall of the heat exchange tube. Therefore, the inner wall of the heat exchange tube 9 has a larger surface area to provide a larger contact area between the working fluid and the inner wall of the heat exchange tube 9. A heat source can supply heat from an outer side to the heat exchange tube 9. When the heat is transferred to the inner wall of the heat exchange tube 9, the working fluid can conduct heat exchange by contacting with the inner wall of the heat exchange tube 9, thereby causing a phase change. However, the heat change is only conducted by the working fluid contacting with the inner wall of the heat exchange tube 1, such that the heat exchange efficiency of the conventional heat exchange tube 9 is still insufficient.

Thus, improvement to the conventional heat exchange tube is necessary.

SUMMARY OF THE INVENTION

To solve the above problem, an objective of the present invention is to provide a heat exchange tube with a better heat exchange efficiency.

Another objective of the present invention is to provide a manufacturing method for a heat exchange tube. The manufacturing method can be used to manufacture a heat exchange tube with a good heat exchange efficiency.

When the terms “front”, “rear”, “left”, “right”, “up”, “down”, “top”, “bottom”, “inner”, “outer”, “side”, and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention, rather than restricting the invention.

As used herein, the term “a” or “an” for describing the number of the elements and members of the present invention is used for convenience, provides the general meaning of the scope of the present invention, and should be interpreted to include one or at least one. Furthermore, unless explicitly indicated otherwise, the concept of a single component also includes the case of plural components.

As used herein, the term “coupling”, “engagement”, “assembly”, or similar terms is used to include separation of connected members without destroying the members after connection or inseparable connection of the members after connection. A person having ordinary skill in the art would be able to select according to desired demands in the material or assembly of the members to be connected.

A heat exchange tube according to the present invention comprises a tube, a first porous layer, and a second porous layer. The tube includes an inner wall. The first porous layer includes a plurality of holes. The first porous layer is disposed on the inner wall of the tube. The second porous layer includes a plurality of holes. The second porous layer is disposed on an inner surface of the first porous layer. An average diameter of the plurality of holes of the second porous layer is greater than an average diameter of the plurality of holes of the first porous layer. In an example, the tube, the first porous layer, and the second porous layer may be manufactured by any materials with high thermal conductivity, such as metal or alloy.

A method for manufacturing a heat exchange tube according to the present invention comprises: mixing first metal powders having a diameter of 10-45 μm with an adhesive to form a first paste; sintering the first paste onto an inner wall of a tube at a sintering temperature of 575° C.-1035° C. to form a first porous layer on the inner wall of the tube; mixing second metal powders having a diameter of 45-200 μm with the adhesive to form a second paste; and sintering the second paste onto an inner surface of the first porous layer at a sintering temperature of 575° C.-1035° C. to form a second porous layer on the inner surface of the first porous layer, wherein an average diameter of the second metal powders is greater than an average diameter of the first metal powders.

Thus, the heat exchange tube according to the present invention provides the first porous layer and the second porous layer on the inner wall of the tube in sequence, and the average diameter of the holes in the second porous layer is greater than the average diameter of the holes in the first porous layer, such that a working liquid in the small holes in the first porous layer can form a large quantity of vaporization nuclei, whereas the large holes in the second porous layer can serve as an exchange passageway for liquid and gas. Therefore, the vaporized bubbles can more rapidly leave the second porous layer, enabling the liquid to rapidly enter the space in the first porous layer (the plurality of holes of the first porous layer), thereby achieving a better heat exchange efficiency. Furthermore, the method for manufacturing a heat exchange tube according to the present invention can produce the heat exchange tube with a better heat exchange efficiency.

In an example, an overall thickness of the first porous layer and the second porous layer is 0.125-0.3 times a wall thickness of the tube. Thus, an excessively large overall thickness of the first porous layer and the second porous layer can be avoided, thereby avoiding reduction in the heat conduction efficiency.

In an example, the wall thickness of the tube is 1-5 mm. Thus, heat can be easily conducted through the wall of the tube into an interior of the tube.

In an example, each of the tube, the first porous layer, and the second porous layer is made of a material selected from the group consisting of red copper, white copper, brass, and iron. Thus, the tube, the first porous layer, and the second porous layer can possess heat conduction properties to proceed with heat exchange with the working fluid.

In an example, the material of each of the tube, the first porous layer, and the second porous layer includes at least 75 wt % of copper. Thus, the tube, the first porous layer, and the second porous layer can possess good heat conductivities.

In an example, each of the tube, the first porous layer, and the second porous layer includes 75-95 wt % of copper and 5-25 wt % of nickel. Thus, the tube, the first porous layer, and the second porous layer can have good anti-corrosion effects.

In an example, the adhesive is selected from the group consisting of polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polymethacrylic acid, acetone, and xylene. Thus, the adhesive may be used as a carrier for aggregating the metal powders, assisting in application of the metal powders on the inner wall of the tube.

In an example, the method for manufacturing the heat exchange tube further comprises before forming the first porous layer on the inner wall of the tube and/or forming the second porous layer on the inner surface of the first porous layer, mixing the first paste and/or the second paste with a pore-forming agent. The pore-forming agent is selected from the group consisting of ferrous sulfate, ferric sulfate, mackinawite, marcasite, pyrite, troilite, pyrrhotite, greigite, amorphous iron sulfide, lead sulfide, coal, silicon dioxide, sodium silicate, sodium oxide, calcium oxide, magnesium oxide, potassium hydroxide, sodium hydroxide, ammonium nitrate, and potassium sulfate. Thus, the porosities of the first porous layer and the second porous layer can be adjusted responsive to the type of the working fluid to thereby provide the best phase change effect according to the respective type of the working fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a conventional heat exchange tube.

FIG. 2 is a perspective view of heat exchange tube of a preferred embodiment according to the present invention.

FIG. 3 is an enlarged view of a circled portion 3 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings. Furthermore, the elements designated by the same reference numeral in various figures will be deemed as identical, and the description thereof will be omitted.

Please refer to FIG. 2 showing a heat exchange tube of a preferred embodiment according to the present invention. The heat exchange tube comprises a tube 1, a first porous layer 2, and a second porous layer 3. The first porous layer 2 is disposed on an inner wall 11 of the tube 1. The second porous layer 3 is disposed on an inner surface of the first porous layer 2.

The tube 1 may form a space S surrounded by an annular wall, such that a working fluid can be received in the space S and can absorb heat outside of the tube 1 via heat transfer to thereby conduct exchange of heat. The wall thickness D of the tube 1 may be 1-5 mm. The tube 1 may be a straight tube or a bent tube. Furthermore, the cross section of the tube 1 may be circular, square, or other geometric shape. The present invention is not limited in this regard. The tube 1 may be made of a metal material advantageous to conduct the heat into the tube 1. For example, the tube 1 may be made of a material having thermal conduction properties, such as copper alloy (red copper, white copper, or brass), iron, or iron alloy. Preferably, the tube 1 includes at least 75 wt % of copper to provide a good thermal conductivity. In this embodiment, the tube 1 is made of white copper to provide the tube 1 with enhanced anti-corrosion property, which can be used in most chemical liquids. The white copper may include 75-95 wt % of copper and 5-25 wt % of nickel.

With reference to FIGS. 2 and 3, the first porous layer 2 may be disposed on the inner wall 11 of the tube 1. The first porous layer 2 has a first average thickness D1 which may be 0.05-0.4 mm. In another embodiment, the first average thickness D1 may be 0.2 mm. The first porous layer 2 may be formed by sintering metal powders. The gaps between metal particles of the metal powders can provide the first porous layer 2 with a plurality of holes. Specifically, the metal particles of the first porous layer 2 may have a diameter of 10-45 μm, such that the average diameter of the plurality of holes of the first porous layer 2 may be 20-22 μm.

The metal powders may be sintered on the inner wall 11 of the tube 1. The metal powders may be powders of a copper alloy (such as red copper, white copper, or brass) or an iron alloy. The first porous layer 2 and the tube 1 may be made of the same material or different materials. In this embodiment, the first porous layer 2 may be formed on the inner wall 11 of the tube 1 by sintering white copper powders. Therefore, the first porous layer 2 and the tube 1 can be of the same material, such that the first porous layer 2 and the inner wall 11 of the tube 1 may have a better engagement.

The second porous layer 3 is disposed on the inner surface of the first porous layer 2. The second porous layer 3 has a second average thickness D2 which may be 0.1-0.4 mm. In another embodiment, the second average thickness D2 may be 0.3 mm. The relationship between the overall thickness D1+D2 of the first porous layer 2 and the second porous layer 3 and the wall thickness D of the tube 1 may be as follows: 0.125D≤D1+D2≤0.3D. Therefore, an excessively large overall thickness of the first porous layer 2 and the second porous layer 3 can be avoided, thereby avoiding reduction in the heat conduction efficiency. The second porous layer 3 may also be formed by sintering metal powders. The gaps between metal particles of the metal powders can provide the second porous layer 3 with a plurality of holes. It is worth noting that the average diameter of the plurality of holes of the second porous layer 3 is greater than the average diameter of the plurality of holes of the first porous layer 2. Specifically, the metal particles of the second porous layer 3 may have a diameter of 45-200 μm, such that the average diameter of the plurality of holes of the second porous layer 3 may be 85-97 μm. The second porous layer 3 and the first porous layer 2 may be made of the same material or different materials. In this embodiment, the second porous layer 3 may also be formed on the inner surface of the first porous layer 2 by sintering white copper powders. Therefore, the second porous layer 3 and the first porous layer 2 may have a better engagement.

Still referring to FIG. 3, the first porous layer 2 and the second porous layer 3 are disposed on the inner wall 11 of the tube 1, such that the inner wall 11 has a dual-layer porous structure having relatively smaller holes and relatively larger holes in sequence. When the working fluid in the tube 1 comes in contact with the second porous layer 3 having relatively larger holes, a plurality of liquid molecules of the working fluid can easily enter the holes of the second porous layer 3. Furthermore, the first porous layer 2 has relatively smaller holes, such that the plurality of liquid molecules of the working fluid can enter each hole of the first porous layer 2 to form nucleation sites during the vaporization process to thereby proceed with nucleation. Nucleation is the initial stage of a phase change. Namely, a plurality of small-diameter holes of the first porous layer 2 permits a plurality of liquid molecules of the working fluids to form a plurality of vaporization nuclei, which permits easy phase change after heat exchange. Furthermore, the metal particles of a relatively smaller size in the first porous layer 2 also enables the first porous layer 2 to form a larger overall surface area to thereby provide a better heat exchange efficiency. After the liquid molecules vaporizes, the relatively larger holes in the second porous layer 3 permit easy exit of the vaporized molecules, such that the holes in the first porous layer 2 can rapidly receive other liquid molecules, thereby achieving a better phase-change efficiency.

Specifically, the method for manufacturing a heat exchange tube according to the present invention comprises mixing first metal powders having a diameter of 10-45 μm with an adhesive to form a first paste. The adhesive may be selected from the group consisting of polypropylene (PP), polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), polymethacrylic acid, acetone, and xylene. The adhesive may be used as a carrier for aggregating the metal powders. After the first paste is applied to the inner wall 11 of the tube 1, sintering can be conducted at a temperature of 575° C.-1035° C. in a sintering furnace, and the first porous layer 2 is formed after cooling to the room temperature. Second metal powders are mixed with the adhesive to form a second paste. Metal powders having a diameter of 45-200 μm may be selected as the metal powders for the second paste. Furthermore, the average diameter of the metal powders of the second paste is greater than the average diameter of the metal powders of the first paste. After the second paste is applied to the inner surface of the first porous layer 2, sintering can be conducted at a temperature of 575° C.-1035° C. in the sintering furnace, and the second porous layer 3 is formed after cooling to the room temperature. In another embodiment, the first porous layer 2 is formed by sintering the first paste at 1000° C., and the second paste can be sintered at 800° ° C. Therefore, the second paste can be sintered at a lower temperature to reduce the risk of damage to the first porous layer 2.

Furthermore, the porosity of the holes in the first porous layer 2 may be the same as or different from the porosity of the holes in the second porous layer 3, which can be adjusted responsive to the type of the working fluid to thereby provide the best phase change effect according to the respective type of the working fluid. For example, the porosity of the first porous layer 2 may be 60.3%, and the porosity of the second porous layer 3 may be 35.73%. In another embodiment, the porosity of the first porous layer 2 may be 59.8%, and the porosity of the second porous layer 3 may be 34.9%. Therefore, a pore-forming agent can be added into the first paste and/or the second paste to adjust the porosities of the holes of the first porous layer 2 and/or the second porous layer 3. The pore-forming agent may, but not limited to, be selected from the group consisting of ferrous sulfate, ferric sulfate, mackinawite, marcasite, pyrite, troilite, pyrrhotite, greigite, amorphous iron sulfide, lead sulfide, coal, silicon dioxide, sodium silicate, sodium oxide, calcium oxide, magnesium oxide, potassium hydroxide, sodium hydroxide, ammonium nitrate, and potassium sulfate.

In view of the foregoing, the heat exchange tube according to the present invention provides the first porous layer 2 and the second porous layer 3 on the inner wall 11 of the tube 1 in sequence, and the average diameter of the holes in the second porous layer 3 is greater than the average diameter of the holes in the first porous layer 2, such that a working liquid in the small holes in the first porous layer 2 can form a large quantity of vaporization nuclei, whereas the large holes in the second porous layer 3 can serve as an exchange passageway for liquid and gas. Therefore, the vaporized bubbles can more rapidly leave the second porous layer 3, enabling the liquid to rapidly enter the space in the first porous layer 2, thereby achieving a better heat exchange efficiency. Furthermore, the method for manufacturing a heat exchange tube according to the present invention can produce the heat exchange tube with a better heat exchange efficiency.

Although the present invention has been described with respect to the above preferred embodiments, these embodiment are not intended to restrict the present invention. Various changes and modifications on the above embodiments made by any person skilled in the art without departing from the spirit and scope of the present invention are still within the technical category protected by the present invention. Accordingly, the scope of the present invention shall include the literal meaning set forth in the appended claims and all changes which come within the range of equivalency of the claims.

Claims

1. A heat exchange tube comprising:

a tube including an inner wall;

a first porous layer including a plurality of holes, wherein the first porous layer is disposed on the inner wall of the tube; and

a second porous layer including a plurality of holes, wherein the second porous layer is disposed on an inner surface of the first porous layer, and wherein an average diameter of the plurality of holes of the second porous layer is greater than an average diameter of the plurality of holes of the first porous layer.

2. The heat exchange tube as claimed in claim 1, wherein an overall thickness of the first porous layer and the second porous layer is 0.125-0.3 times a wall thickness of the tube.

3. The heat exchange tube as claimed in claim 2, wherein the wall thickness of the tube is 1-5 mm.

4. The heat exchange tube as claimed in claim 1, wherein each of the tube, the first porous layer, and the second porous layer is made of a material selected from the group consisting of red copper, white copper, brass, and iron.

5. The heat exchange tube as claimed in claim 1, wherein the material of each of the tube, the first porous layer, and the second porous layer includes at least 75 wt % of copper.

6. The heat exchange tube as claimed in claim 5, wherein each of the tube, the first porous layer, and the second porous layer includes 75-95 wt % of copper and 5-25 wt % of nickel.

7. A method for manufacturing a heat exchange tube, the method comprising:

mixing first metal powders having a diameter of 10-45 μm with an adhesive to form a first paste;

sintering the first paste onto an inner wall of a tube at a sintering temperature of 575° C.-1035° C. to form a first porous layer on the inner wall of the tube;

mixing second metal powders having a diameter of 45-200 μm with the adhesive to form a second paste; and

sintering the second paste onto an inner surface of the first porous layer at a sintering temperature of 575° C.-1035° C. to form a second porous layer on the inner surface of the first porous layer, wherein an average diameter of the second metal powders is greater than an average diameter of the first metal powders.

8. The method for manufacturing the heat exchange tube as claimed in claim 7, wherein an overall thickness of the first porous layer and the second porous layer is 0.125-0.3 times a wall thickness of the tube.

9. The method for manufacturing the heat exchange tube as claimed in claim 8, wherein the wall thickness of the tube is 1-5 mm.

10. The method for manufacturing the heat exchange tube as claimed in claim 7, wherein each of the tube, the first porous layer, and the second porous layer is made of a material selected from the group consisting of red copper, white copper, brass, and iron.

11. The method for manufacturing the heat exchange tube as claimed in claim 7, wherein the material of each of the tube, the first porous layer, and the second porous layer includes at least 75 wt % of copper.

12. The method for manufacturing the heat exchange tube as claimed in claim 11, wherein each of the tube, the first porous layer, and the second porous layer includes 75-95 wt % of copper and 5-25 wt % of nickel.

13. The method for manufacturing the heat exchange tube as claimed in claim 7, wherein the adhesive is selected from the group consisting of polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polymethacrylic acid, acetone, and xylene.

14. The method for manufacturing the heat exchange tube as claimed in claim 7, further comprising before forming the first porous layer on the inner wall of the tube and/or forming the second porous layer on the inner surface of the first porous layer, mixing the first paste and/or the second paste with a pore-forming agent, wherein the pore-forming agent is selected from the group consisting of ferrous sulfate, ferric sulfate, mackinawite, marcasite, pyrite, troilite, pyrrhotite, greigite, amorphous iron sulfide, lead sulfide, coal, silicon dioxide, sodium silicate, sodium oxide, calcium oxide, magnesium oxide, potassium hydroxide, sodium hydroxide, ammonium nitrate, and potassium sulfate.