US20180080718A1

US20180080718A1 - Heat Pipe with Inner Zeolite Coated Structure

Info

Publication number: US20180080718A1
Application number: US15/268,758
Authority: US
Inventors: Heng-Yi Li; Meng-Chang Tsai; To-Mei Wang
Original assignee: Institute of Nuclear Energy Research
Current assignee: Institute of Nuclear Energy Research
Priority date: 2016-09-19
Filing date: 2016-09-19
Publication date: 2018-03-22

Abstract

The heat pipe comprises a shell and an inner zeolite coated structure. The shell has an inner surface. The inner surface surrounds an enclosed chamber. The chamber is partially filled with a working fluid in a vacuum. The working fluid may be changed into a liquid phase or a gas phase by following temperature change. The coating material comprises a zeolite, a binder and an additive. The material is sintered on the inner surface of the heat pipe. Consequently, the zeolite coating is formed between the inner surface and the enclosed chamber. Thus, the present invention uses a porous material of zeolite with pore size smaller than grooves and meshes to have excellent evaporation heat transfer and capillary force. The zeolite coating of the present invention does not fail without air isolation. The present invention is inner manufactured under atmospheric condition so has no size limitation.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the inner structure of heat pipe; more particularly, relates to the heat pipe with zeolite coated on the inner surface for capillary wick for cooling and waste heat recovery.

DESCRIPTION OF THE RELATED ARTS

Heat pipe is most commonly used in the following fields: cooling of electronic components and electrical devices, and waste heat recovery of equipment or machinery. Currently much waste heat is discharged directly or indirectly without recycling. Directly-discharged waste heat mostly exists in the exhausted gas and liquid, and its sources include boilers, burners, incinerators, furnaces, combustion engines and other heating facilities. Indirect-discharged heat sources are the cooling air or cooling water loops that are used to remove the heat of facilities for protection, or the heat of processes for next handling station.
The first prior art in FIG. 7 is a thermosyphon 100. The shell 101 is made of metal and partially filled with working fluid 102 inside after being vacuumed. When the evaporator section 103 is heated by heat source at lower position, the liquid working fluid 102 evaporates by absorbing heat and turns into gas. The gas working fluid 102 of high pressure is instantly formed and by buoyancy rushes upwards the condenser section 104 at higher position. There, the gas working fluid 102 condenses by releasing heat to outside and turns into liquid. The liquid working fluid 102 flows downwards the evaporator section 103 along the wall by gravity, and after that absorbs heat again. Such a cycle repeats to transfer heat from the lower position to the higher position. Yet, it is obvious that thermosyphon can only transfer heat upwardly.
In the case of the amount of the liquid working fluid flowing back to the evaporator section is reduced, the evaporator section would dry out. Hence, a second prior art that heat pipe which a capillary wick is built inside and attached to an inner surface is proposed. With the wick, capillary force is provided to enhance the liquid working fluid to flow back. The wick is obtained by sintering a powder of at least one of the following metals: copper, aluminum, zinc, lead, tin, nickel, silver, and gold. However, the metal powder must be sintered under a vacuum or inert gas filled circumstance. Besides, the overall length of the heat pipe is limited by the size of the sintering furnace so it is only suitable for a heat pipe with a length less than 50 centimeters (cm). In addition, air isolation is required after sintering; otherwise the wick may be easily oxidized and fail.
For other prior art, a capillary wick inside the heat pipe with a length more than 50 cm can be made by a fiber of the material compatible with working fluid. The fiber may be further woven into various forms of mesh to be placed inside the heat pipe. Otherwise grooves are formed on the inner surface of the heat pipe. Although the above method suits various sizes of pipe, the pore size is too big so that the evaporation heat transfer capability and capillary force is insufficient.
The other prior arts relates to the inner structure of heat pipe include U.S. Patent US2013/0168052A1, US2013/0160976A1, US2010/0200199A1, U.S. Pat. No. 7,594,573B2, US2006/0222423A1, US2006/0207750A1, US2006/0016580A1, US2005/0116336A1, U.S. Pat. Nos. 7,086,454, 4,674,565, 3,952,798, 3,762,011; and European Patent EP1715274A2. According to the above prior arts, there is no effective way to at the same time solve the problems of size limitation, wick oxidation during manufacturing, insufficient evaporation heat transfer capability and capillary force.
Hence, the prior arts do not fulfill all users' requests on actual use.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a heat pipe having an internal structure with a zeolite coating on inner surface, whereby the size of the heat pipe is limitless and wick oxidization is avoided without air isolation. Furthermore, maximum evaporation heat transfer capability and capillary force are obtained.
To achieve the above purpose, the present invention is a heat pipe with high efficiency, comprising a shell and a zeolite coating, where the shell has an inner surface; the inner surface surrounds an enclosed chamber; the enclosed chamber is partially filled with a working fluid under a vacuum; the working fluid is changed into a liquid phase or a gas phase by the temperature of the working fluid; the shell has an evaporator section and a condenser section; the condenser section is located away from the evaporator section; the zeolite coating is fabricated on the inner surface; the zeolite coating is fabricated with a material comprising a zeolite, a binder and an additive; the zeolite is mixed and stirred with the binder and the additive to obtain a slurry to be sintered on the inner surface of the shell; and the zeolite coating has pores and each pore has a diameter from less than 10 nanometers to several hundred micrometers and a specific surface of 100˜600 square meters per gram (m²/g). Accordingly, a heat pipe with high efficiency is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which

FIG. 1 is the vertical cross-sectional view showing the preferred embodiment according to the present invention;

FIG. 2 is the horizontal cross-sectional view showing the zeolite single-layer coating;

FIG. 3 is the horizontal cross-sectional view showing the zeolite dual-layer coating;

FIG. 4 is the flow block diagram showing the fabrication of the present invention;

FIG. 5 is the cross-sectional view showing the zeolite coating on the surface of the micro grooves;

FIGS. 6A-6C are views showing the zeolite crystals; and

FIG. 7 is the view of the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the preferred embodiment is provided to understand the features and the structures of the present invention.
Please refer to FIG. 1˜FIG. 6, which are a vertical cross-sectional view showing a preferred embodiment according to the present invention; horizontal cross-sectional views showing a zeolite single-layer coating and a zeolite dual-layer coating; a flow block diagram showing fabrication of the present invention; a cross-sectional view showing a zeolite coating on surface of micro grooves; and a view showing zeolite crystals. As shown in the figures, the present invention is a heat pipe 200 for cooling or recycling waste heat with high efficiency, comprising a shell 201, and a zeolite coating 205.
The shell 201 has an evaporator section 203 and a condenser section 204 located away from the evaporator section 203. The shell 201 has an inner surface 2011. The inner surface 2011 surrounds an enclosed chamber 2012. The enclosed chamber 2012 is partially filled with a working fluid 202 under a vacuum, where the working fluid 202 is changed into a liquid phase or a gas phase by following a temperature of the working fluid 202.
The zeolite coating 205 is formed between the inner surface 2011 and the enclosed chamber 2012 in the shell 201. The zeolite coating 205 is made of a zeolite, a binder and an additive. The zeolite, the binder and the additive are uniformly mixed and stirred together to be sintered on the inner surface 2011 of the shell 201.
Thus, a heat pipe with high efficiency is obtained.
The shell 201 is made of a metal having a tensile strength more than 50 kilograms per square millimeter (kg/mm²) at 100˜1000 Celsius degrees (° C.); such as carbon steel, SUS201, SUS202, SUS304, SUS316 and SUS430.
The shell 201 has a cross-sectional round, elliptic, square, rectangle or polygon shape. The cross-sectional shape of the shell 201 has a radius of gyration of 1˜1000 mm and the shell 201 has a slenderness ratio of 0.001˜1000.
The working fluid 202 transfers heat by being changed into a gas phase or a liquid phase at 50˜1000° C.; and is water, an alcohol, a benzene, an alkane, a refrigerant, a synthetic oil, lithium, sodium or potassium. Or, the working fluid 202 is added with high thermally conductive powder or particles of silver, copper or aluminum.
The zeolite coating 205 has pores; and, each pore has a diameter from less than 10 nanometers to several hundred micrometers and a specific surface of 100˜600 square meters per gram (m²/g). The zeolite coating 205 has a thickness of 1˜1000 micrometers (μm) for one layer contained.
As shown in FIG. 2, the zeolite coating 205 can be a single-layer coating of zeolite. Or, as shown in FIG. 3, the zeolite coating 205 can be a dual-layer coating, where each layer has pores; the two layers comprises a bottom-coating layer 207 and a top-coating layer 206 sequentially formed bottom-up from the inner surface 2011; and the pores of the bottom-coating layer have larger sizes than the pores of the top-coating layer.
A flow block diagram for fabricating the zeolite coating 205, (206, 207) is shown in FIG. 4. At first, the zeolite is mixed with the binder and the additive for obtaining slurry. The binder is geopolymer or epoxy. The slurry is then coated on the inner surface 2011 of the shell 201. After being spread, mold formed and calcined, the zeolite coating 205 is obtained. Or, the inner surface 2011 of the shell 201 may be further processed to be roughened or to form micro grooves 2013; and, then, the zeolite coating 205 is coated on the roughened inner surface 2011 or surface of the micro grooves 2013, as shown in FIG. 5.
The additive in the slurry is selected from aluminum oxide, titanium oxide, zirconium oxide or silicon oxide; or a mixture of some selected therefrom. The zeolite framework is constructed by two tetrahedrons of silicon oxide (SiO₄) and aluminum oxide (AlO₄), whose form is open and has interconnect spaces or tunnels. Thus it is a porous material with an extremely large surface for being widely used in adsorbents, catalytic converters and catalyst carriers. The zeolite has a selectable ratio of silicon to aluminum, which can be low-silica zeolite, intermediate-silica zeolite or high-silica zeolite, as shown in FIGS. 6A-6C. The zeolite framework type concludes MFI-type, X-type and A-type. Hence, the zeolite coating 205 of the inner surface has the following advantages:
(1) The zeolite coating 205 is made of a porous material. According to Laplace-Yang's formula, a capillary pressure can be obtained by the following equation:
ΔPcap=(2σ·cos(θ))/rp
Therein, σ is a surface tension; θ is a contact angle of solid and liquid; rp is a pore radius. Accordingly, a smaller pore radius obtains a greater capillary pressure. Since the radiuses of pores of the zeolite is smaller than the micro grooves and meshes, a greater capillary pressure is obtained to increase a backflow of the working fluid 202 at the condenser section 204 for transferring heat downwardly, upwardly, slantingly or horizontally.
(2) The zeolite coating 205 is made of a porous material. The porous zeolite coating forms reentrant cavities on the inner surface of heat pipe evaporator section 203 and act as vapor traps during nucleate boiling, which increases stable bubble nucleation sites. It also enlarges the heat transfer area and improves liquid replenishment. Thus pool boiling or evaporation heat transfer is enhanced.
(3) The main components of the zeolite are aluminum oxide, silicon oxide and other oxides, which will not fail by oxidation and can be inner manufactured under atmospheric conditions regardless of the size of the heat pipe.
The present invention relates to an industrial heat exchanger using pipe for cooling or recycling heat, which proposes a new design of internal structure of the heat pipe. On using the present invention, the evaporator section 203 is contacted with heat source of corrosive gas, corrosive liquid, radioactive gas, radioactive liquid, radioactive solid, toxic gas, toxic liquid, toxic solid, smoke, waste liquid, solvent, sludge, powder, granule, sand, incinerator bottom ash, smelting furnace slag, hot spring geothermal heat, steam geothermal heat, sulfur geothermal heat or solar heat; and the heat source has a temperature of 50˜1000° C. The condenser section 204 is contacted with a heat sink of air, water, a phase-changing material or a gas-phase, a liquid-phase and a solid-phase material. The present invention applies the zeolite coating on the inner surface of the heat pipe, where the zeolite is a porous material and has a great surface area with pore radiuses smaller than those of micro grooves and meshes for obtaining good heat-transfer capability and capillary. The main components of the zeolite are aluminum oxide, silicon oxide and other oxides, which will not fail by oxidation; and the heat pipe, regardless of its size, can be inner manufactured under an atmospheric condition without air isolation.
To sum up, the present invention is a heat pipe for cooling and recycling waste heat with high efficiency, where a new design of internal structure of a heat pipe for cooling and recycling waste heat is proposed to be inner manufactured under an atmospheric condition without air isolation regardless of the size of the heat pipe.
The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.

Claims

What is claimed is:

1. A heat pipe for cooling and recycling waste heat, comprising

a shell, said shell having an inner surface, said inner surface surrounding an enclosed chamber, said enclosed chamber being partially filled with a working fluid under a vacuum, said working fluid being changed into a phase selected from a group consist of a liquid phase and a gas phase by following a temperature of said working fluid, said shell having an evaporator section and a condenser section, said condenser section being located away from said evaporator section; and

a zeolite coating, said zeolite coating being obtained between said inner surface and said enclosed chamber, said zeolite coating being coated with a material comprising a zeolite, a binder and an additive,

wherein said binder is geopolymer or expoxy, and mixed with said zeolite and said additive to obtain slurry to be sintered on said inner surface of said shell; and

wherein said zeolite coating has pores and each pore has a diameter from less than 10 nanometers to several hundred micrometers and a specific surface of 100˜600 square meters per gram (m²/g).

2. The heat pipe according to claim 1,

wherein said shell is made of a metal having a tensile strength more than 50 kilograms per square millimeter (kg/mm²) at 100˜1000 Celsius degrees (° C.).

3. The heat pipe according to claim 2,

wherein said metal is selected from a group consist of carbon steel, SUS201, SUS202, SUS304, SUS316 and SUS430.

4. The heat pipe according to claim 2,

wherein said metal material is a mixture of materials selected from a group consist of carbon steel, SUS201, SUS202, SUS304, SUS316 and SUS430.

5. The heat pipe according to claim 1,

wherein said shell has a cross-sectional shape selected from a group consist of a round shape, an elliptic shape, a square shape, a rectangle shape and a polygon shape.

6. The heat pipe according to claim 1,

wherein said cross-sectional shape of said shell has a radius of gyration of 1˜1000 mm and said shell has a slenderness ratio of 0.001˜1000.

7. The heat pipe according to claim 1,

wherein said working fluid is selected from a group consist of water, an alcohol, a benzene, an alkane, a refrigerant, a synthetic oil, lithium, sodium and potassium to transfer heat by being changed into a gas phase or a liquid phase at 100˜1000° C.

8. The heat pipe according to claim 1,

wherein said working fluid is added with nanometer sized powders or particles form of a high thermally conductive metal to obtain high heat transfer performance; said form is selected from a group consist of powder and particles; and said metal is selected from a group consist of silver, copper and aluminum.

9. The heat pipe according to claim 1,

wherein said zeolite coating has only one layer and has a thickness of 100˜1000 micrometers (μm).

10. The heat pipe according to claim 1,

wherein said zeolite coating has two layers with pores;

wherein said two layers comprises a bottom-coating layer and a top-coating layer sequentially obtained bottom-up from said inner surface; and

wherein said pores of said bottom-coating layer have larger sizes than said pores of said top-coating layer.

11. The heat pipe according to claim 1,

wherein said zeolite is selected from a group consist of low-silica zeolite, intermediate-silica zeolite and high-silica zeolite.

12. The heat pipe according to claim 1,

wherein said zeolite has a type of crystal and said type is selected from a group consist of MFI type, X type and A type.

13. The heat pipe according to claim 1,

wherein said additive is selected from a group consist of aluminum oxide, titanium oxide, zirconium oxide and silicon oxide.

14. The heat pipe according to claim 1,

wherein said additive is a mixture of materials selected from a group consist of aluminum oxide, titanium oxide, zirconium oxide and silicon oxide.

15. The heat pipe according to claim 1,

wherein micro grooves are located on said inner surface of said shell and said zeolite coating is obtained on surface of said micro grooves.

16. The heat pipe according to claim 1,

wherein said evaporator section is contacted with heat source selected from a group consist of corrosive gas, corrosive liquid, radioactive gas, radioactive liquid, radioactive solid, toxic gas, toxic liquid, toxic solid, smoke, waste liquid, solvent, sludge, powder, granule, sand, incinerator bottom ash, smelting furnace slag, hot spring geothermal heat, steam geothermal heat, sulfur geothermal heat and solar heat; and

wherein said heat source has a temperature of 50˜1000° C.

17. The heat pipe according to claim 1,

wherein said condenser section is contacted with a heat sink selected from a group consist of air, water, a phase-changing material.

18. The heat pipe according to claim 1,

wherein said condenser section is contacted with a heat sink of a material having a phase selected from a group consist of a gas phase, a liquid phase and a solid phase.