阅读说明：本技术 一种具有螺旋形加强热管的纳米流体集热器 (Nano fluid heat collector with spiral reinforced heat pipe ) 是由 李博 刘添旺 台颖娣 程驰 王军锋 于 2019-10-18 设计创作，主要内容包括：本发明公开了一种具有螺旋形加强热管的纳米流体集热器,包括相变蓄热箱和集热单元,集热单元包括一个或多个真空导热管,真空导热管包括封闭式的热管,热管套有集热层的一端为热管蒸发端,另一端插入相变蓄热箱内为热管冷凝端；热管内设有螺旋强化冷凝器,且热管内填充有纳米流体作为导热工质,本发明以纳米流体为工作介质能够有效提高太阳能集热效率。(The invention discloses a nanofluid heat collector with spiral reinforced heat pipes, which comprises a phase-change heat storage tank and a heat collection unit, wherein the heat collection unit comprises one or more vacuum heat conduction pipes, each vacuum heat conduction pipe comprises a closed heat pipe, one end of each heat pipe, which is sleeved with the heat collection layer, is a heat pipe evaporation end, and the other end of each heat pipe, which is inserted into the phase-change heat storage tank, is a heat pipe condensation end; the spiral reinforced condenser is arranged in the heat pipe, and the nano fluid is filled in the heat pipe to be used as a heat conducting working medium.)

1. A nanofluid heat collector with spiral reinforced heat pipes is characterized by comprising a phase change heat storage tank (8) and a heat collection unit, wherein the heat collection unit comprises one or more vacuum heat conduction pipes (10), each vacuum heat conduction pipe (10) comprises a closed heat pipe (30), one end, sleeved with the heat collection layer, of each heat pipe (30) is a heat pipe evaporation end (28), and the other end, inserted into the phase change heat storage tank (8), of each heat pipe is a heat pipe condensation end (29); a spiral reinforced condenser (31) is arranged in the heat pipe (30), and the nano fluid is filled in the heat pipe (30) and is used as a heat conducting working medium.

2. The nanofluid heat collector with spirally reinforced heat pipes according to claim 1, wherein the nanofluid in the heat pipe (30) is selected from Al2O3 nanofluid, CuO nanofluid, TiO2 nanofluid, MgO nanofluid, ZnO nanofluid or SiO2 nanofluid.

3. The nanofluid heat collector with spirally reinforced heat pipes according to claim 1, wherein the spirally reinforced condenser (31) comprises a drainage column (26) axially disposed along the heat pipe (30), a spiral wick (24) is disposed around the drainage column (26), and the spiral wick (24) is spirally tapered from a heat pipe condensation end (29) to a heat pipe evaporation end (28); the spiral liquid suction core (24) is connected with a drainage column (26) through a capillary suction pipe (25).

4. The nanofluid heat collector with spirally reinforced heat pipes according to claim 3, wherein the drainage columns (26) are made of a material having thermal conductivity and hydrophobicity.

5. The nanofluid heat collector with spirally reinforced heat pipes according to claim 3, wherein the spiral wick (24) is made of a material having good thermal conductivity and good resistance to expansion and contraction.

6. The nanofluid heat collector with spirally reinforced heat pipes according to claim 3, wherein the capillary suction pipe (25) is made of a hydrophilic material with good heat conductivity, such as metal or nonmetal.

7. The nanofluid heat collector with spirally reinforced heat pipes according to claim 1, wherein the heat collecting layer is a U-shaped double-layer glass pipe, and the open end of the double-layer glass pipe is fixed with the heat pipe (30) through a heat pipe connecting thread (20); a vacuum layer (15) is arranged between an outer glass tube (14) and an inner glass tube (17) of the double-layer glass tube, and a getter (22) is arranged in the vacuum interlayer (15).

8. The nanofluid heat collector with spirally reinforced heat pipes according to claim 7, wherein the inner glass tube (17) is coated on the outer surface with an absorption coating (16); and a silicon dioxide nanometer fluid (18) is filled between the inner glass tube (17) and the outer wall of the heat pipe.

9. The nanofluid heat collector with spirally reinforced heat pipes according to claim 8, wherein the silica nanofluid (18) has an average particle diameter of 10nm, a mass fraction of 5%, and a thermal conductivity varying from 1.102 to 1.402 according to temperature.

10. The nanofluid heat collector with the spiral reinforced heat pipes according to any one of claims 1 to 9, wherein an insulating layer is arranged between the inner wall (6) and the outer wall (4) of the phase change heat storage tank (8), an insulating material (5) is filled in the insulating layer, and the insulating material (5) is mineral wool or rock wool.

Technical Field

The invention belongs to the technical field of solar heat exchange, and particularly relates to a nanofluid heat collector with a spiral reinforced heat pipe.

Background

Solar energy is used as an ideal clean energy source, and has double important meanings for environmental protection and energy utilization for high-efficiency utilization of the solar energy. At present, the fields of solar energy utilization mainly include photovoltaic power generation, thermal power generation and direct heat utilization, and the limitations are that solar energy can only be utilized in the daytime and the conversion efficiency is very low. Therefore, improving the solar thermal efficiency is one of the important ways to solve these limitations.

Patent document (CN 1932410a) proposes a nano-fluid solar window type heat collector, which mainly uses different nano-fluids to utilize solar radiation in different bands, multiple forms and full bands, but this method has the disadvantage of too high heat dissipation rate to achieve the purpose of heat collection.

Patent document (CN 203813716U) proposes a cooling high-power concentrating solar photovoltaic photo-thermal system based on a nano-fluid microchannel, and the main scheme is to adopt a nano-fluid microchannel subsystem heat dissipation mode to achieve a high-efficiency photovoltaic effect, but the method has the defect that the microchannel is blocked by the nano-fluid.

Patent document (CN 102434981 a) proposes a flat heat pipe collector, which mainly uses a flat heat pipe collector to achieve efficient use of solar energy, but this method has the disadvantages of large manufacturing difficulty and loose theoretical basis.

It can be known from the current situation that the current market of solar heat collectors does not have products with very high comprehensive performance indexes, and further research and improvement of the technology are very important.

Disclosure of Invention

In order to solve the defects in the prior art, the invention provides a nanofluid heat collector with a spiral reinforced heat pipe.

The technical scheme adopted by the invention is as follows:

the heat collecting unit comprises one or more vacuum heat conducting pipes, each vacuum heat conducting pipe comprises a closed heat pipe, one end of each heat pipe, which is sleeved with the heat collecting layer, is a heat pipe evaporation end, and the other end of each heat pipe, which is inserted into the phase-change heat storage box, is a heat pipe condensation end; a spiral reinforced condenser is arranged in the heat pipe, and nano fluid is filled in the heat pipe to serve as a heat conducting working medium;

further, the nanofluid in the heat pipe is oxide nanofluid, such as Al2O3, CuO, TiO2, MgO, ZnO or SiO2 and other nanofluid;

furthermore, the spiral reinforced condenser comprises a drainage column arranged along the axial direction of the heat pipe, a spiral liquid absorption core is arranged around the drainage column, and the spiral liquid absorption core is spirally gradually reduced from the condensation end of the heat pipe to the evaporation end of the heat pipe; the spiral liquid suction core is connected with the drainage column through a capillary suction pipe;

further, the drainage column is made of a material with heat conductivity and hydrophobicity, such as copper, aluminum or stainless steel;

furthermore, the spiral liquid absorption core is made of glass, ceramic or silicon nitride which has good heat-conducting property and good expansion and contraction resistance;

furthermore, the capillary suction pipe is made of metal or nonmetal hydrophilic materials with good heat conduction performance, such as copper powder, nickel powder or ceramic powder sintering materials;

furthermore, the heat collecting layer comprises a U-shaped double-layer glass tube, and the open end of the double-layer glass tube is fixed with the heat tube through a heat tube connecting thread; a vacuum layer is arranged between the outer glass tube and the inner glass tube of the double-layer glass tube, and a getter is placed in the vacuum interlayer;

further, an absorbing coating is coated on the outer surface of the inner glass tube; silicon dioxide nanofluid is filled between the inner glass tube and the outer wall of the heat pipe;

further, the average diameter of the silicon dioxide nano fluid particles is 10nm, the mass fraction is 5%, and the variation range of the thermal conductivity with the temperature is 1.102-1.402;

further, a heat insulation layer is arranged between the inner wall of the heat storage box and the outer wall of the heat storage box of the phase-change heat storage box, a heat insulation material is filled in the heat insulation layer, and the heat insulation material is mineral wool or rock wool.

The invention has the beneficial effects that:

1. the heat pipe type heat collector adopts a phase change heat transfer mode, takes the nano fluid as a working medium, and is not filled with the vacuum interlayer in the inner glass pipe and the outer glass pipe due to the unique property and the special structural design of the nano fluid, a nano fluid heat exchange working medium in the heat pipe is stored at the evaporation end of the heat pipe in an inactivated state, and the working medium has a certain expansion space.

2. Solar energy can irradiate the inner glass through the outer glass tube, the inner tube absorbs heat, then heat transfer fluid between the inner tube and the heat pipe is heated, and the interlayer is vacuumized; effectively reduces the heat loss to the environment and improves the heat collection efficiency. The special selective coating has temperature resistance. The solar radiation energy is mainly distributed in visible light and near infrared light regions, the energy of blackbody radiation generated by heating an object is mainly distributed in a far light region, the solar energy absorptivity of the aluminum-nitrogen/aluminum selective coating is greater than 0.93, and the infrared emissivity is less than 0.09, so that the heat collection efficiency is greatly improved, and the heat loss is remarkably reduced.

3. Because the particle size of the nano particles is in the nano scale, the nano particles suspended in the nano fluid do random motion under the action of Brownian force and the like. The micro-motion of the nano-particles causes micro-convection between the particles and the liquid, and the micro-convection enhances the energy transfer process between the particles and the liquid, so that the heat conductivity coefficient of the nano-fluid is much higher than that of the traditional pure liquid. Therefore, the nanometer fluid is adopted as the heat conducting working medium, the heat efficiency of the heat collector can be improved, and the water can be heated to the required temperature in a short heating time.

4. By adopting the solar heat collector disclosed by the invention, the highest stable temperature can be reached within 1-2 h under the direct solar radiation, and the highest stable temperature is about 76 ℃. Compared with the traditional solar heat collector, the maximum stable temperature can be reached within at least three to four hours under the same illumination condition, and the maximum stable temperature is about 70 ℃. The heat collector has the characteristics of short starting time, high heat conduction efficiency, small heat loss and the like.

5. The spiral reinforced condenser is arranged in the heat pipe, the conical structure has a one-way condensation function, and the spiral structure divides the interior of the heat pipe into two channels, namely a part of steam channel and a part of condensate reflux channel. The capillary suction pipe in the spiral structure and the capillary suction force of the drainage column form a return channel, so that the return resistance is reduced, and the axial heat conductivity coefficient is increased. Compared with the traditional heat pipe, the heat pipe has the advantages of high starting speed, high axial heat conductivity coefficient, high circulation rate and the like.

6. The product designed by the invention has long service life, high reliability and good stability.

7. The product saves energy and reduces emission, adopts the nano fluid photo-thermal technology, obviously improves the solar energy absorption rate, and accords with the sustainable development policy.

Drawings

FIG. 1 is a schematic view of the structural assembly of the present invention;

FIG. 2 is a cross-sectional view of a heat pipe configuration of the present invention;

in the figure, 1, an outlet flow regulating valve, 2, a temperature sensor, 3, an exhaust port, 4, an outer wall of a heat storage box, 5, a heat insulation material, 6, an inner wall of the heat storage box, 7, an inlet flow regulating valve, 8, a phase change heat storage box, 9, a water level detector, 10, a vacuum heat conduction pipe, 11, hot water in the heat storage box, 12, a water outlet, 13, a water inlet, 14, an outer glass pipe, 15, a vacuum layer, 16, a heat absorption coating, 17, an inner glass pipe, 18, a silicon dioxide nanofluid, 19, an inner wall of the heat pipe, 20, a connecting thread of the heat pipe, 21, a supporting material of the outer glass pipe, 22, an air detraining agent, 23, a bracket, 24, a spiral liquid absorption core, 25, a capillary suction pipe, 26, a drainage column, 27, a spiral condenser gap, 28, an evaporation end of the heat.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1, the nanofluid heat collector with the spiral reinforced heat pipe designed by the invention comprises a phase change heat storage tank 8 and a heat collection unit, wherein a heat insulation layer is arranged between a heat storage tank inner wall 6 and a heat storage tank outer wall 4 of the phase change heat storage tank 8, and a heat insulation material 5 is filled in the heat insulation layer. A water inlet 13 is arranged at the bottom of one side wall of the phase-change heat storage tank 8, an inlet flow regulating valve 7 is arranged on the water inlet 13, a water outlet 12 is arranged at the upper part of the other side wall, an outlet flow regulating valve 1 is arranged on the water outlet 12, and an exhaust port 3 is arranged at the top of the phase-change heat storage tank 8. A temperature sensor 2 is arranged on the inner wall 6 of the heat storage box close to the water outlet 12 and used for detecting the temperature of the water outlet, judging whether the use requirement is met or not, and opening the outlet flow regulating valve 1 only when the use requirement is met; and a water level detector 9 is arranged on the inner side of the bottom of the phase-change heat storage tank 8, and whether the water tank needs to supply water or not is judged according to the data of the water level detector, so that the water tank is ensured to store enough hot water.

The heat collecting unit comprises one or more vacuum heat conducting pipes 10, as shown in fig. 2, the vacuum heat conducting pipes 10 comprise closed heat pipes 30, heat collecting layers are sleeved outside the heat pipes 30, the heat collecting layers comprise U-shaped double-layer glass pipes, and the open ends of the double-layer glass pipes are fixed with the heat pipes 30 through heat pipe connecting threads 20; a vacuum layer 15 is arranged between an outer glass tube 14 and an inner glass tube 17 of the double-layer glass tube, a getter 22 is arranged in a vacuum interlayer 15, and a support piece 21 is arranged between the outer glass tube 14 and the inner glass tube 17 in order to ensure the stability between the outer glass tube 14 and the inner glass tube 17.

The outer surface of the inner glass tube 17 is coated with an absorption coating 16, the absorption coating 16 adopts a magnetron sputtering process, an aluminum-nitrogen/aluminum selective absorption film is utilized, the absorption rate of the film is greater than 0.93, the infrared emissivity is about 0.06, the selective heat absorption coating has the function of absorbing solar energy as much as possible and converting the solar energy into heat energy for utilization, meanwhile, the heat loss caused by heat radiation is reduced as much as possible, and the photo-thermal conversion efficiency of the heat collection tube is improved. Silicon dioxide nanofluid 18 is filled between the inner glass tube 17 and the outer wall of the heat pipe, the average diameter of particles of the silicon dioxide nanofluid 18 is 10nm, the mass fraction is 5%, and the variation range of the thermal conductivity coefficient along with the temperature is 1.102-1.402; the inside of the heat pipe 30, which is wrapped by the heat collecting layer, is a heat pipe evaporation end 28, the other end is a heat pipe condensation end 29, and the heat pipe condensation end 29 is inserted into the phase change heat storage tank 8.

Oxide nanofluid serving as a heat conducting working medium, such as nanofluid of Al2O3, CuO, TiO2, MgO, ZnO or SiO2, is filled in the heat pipe 30, and in the embodiment, Al2O3 nanofluid is selected; 4 drainage columns 26 are arranged in the heat pipe 30 along the axial direction of the heat pipe 30, a square is formed by the 4 drainage columns 26, the side length of the square (namely the distance between every two drainage columns 26) is equal to 10mm, the bottom ends of the drainage columns 26 are fixedly connected with the inner wall of the heat pipe 30 through a support 23, the drainage columns 26 are made of materials with smooth surfaces, and have good thermal expansion and cold contraction resistance, thermal conductivity and hydrophobicity, for example, copper, aluminum or stainless steel is selected;

a spiral liquid absorption core 24 is arranged around the drainage column 26, the spiral liquid absorption core 24 is arranged from a heat pipe condensation end 29 to a heat pipe evaporation end 28 in a spiral and gradually-reduced mode, and a spiral condenser gap 27 between the spiral liquid absorption core 24 at the uppermost end and the inner wall 19 of the heat pipe is larger and larger downwards; and the spiral liquid absorbing core 24 is connected with the outer wall of the drainage column 26 through a capillary suction pipe 25; the spiral liquid suction core 24 is supported and fixed by the capillary suction pipe 25. In the present embodiment, spiral wick 24 is made of a material having good thermal conductivity and good resistance to expansion caused by heat and contraction caused by cold, such as glass, ceramic, or silicon nitride; the capillary suction pipe 25 is made of metal or nonmetal hydrophilic materials with good heat conduction performance, the thickness of the capillary suction pipe 25 and the spiral liquid absorption core 24 is about 5mm, the diameter of the connection end of the capillary suction pipe 25 and the drainage column 26 is about 2mm, the inclination angle is about 45 degrees, the capillary suction pipe 25 has good adsorption effect on liquid drops, the liquid drops formed by condensation are adsorbed and converged to the drainage column 26, and the liquid drops flow to the evaporation end 28 of the heat pipe from the drainage column 26.

In this embodiment, the stable Al2O3 nanofluid and the SiO2 nanofluid 18 are prepared by a two-step method, and a proper amount of SiO2 nanoparticle powder material is selected by calculation, and after being sheared by a high-speed shearing machine, the particles are uniformly dispersed into the base liquid by the high-pressure microjet, so that the nanofluid with the mass fraction of 5% is prepared. The detailed process comprises using Al2O3 and SiO2 nanoparticles with average particle diameter of 10nm, deionized water as base solution, and anionic surfactant SDS and high molecular surfactant gum Arabic (Arabic gum, AG) as dispersing agent. Sequentially adding the base liquid, the dispersing agent and the nano particles, uniformly stirring, magnetically stirring for 10min, and then putting into a KQ-400KDB type high-power numerical control ultrasonic cleaner for ultrasonic dispersion. In order to prevent the nanometer fluid from being overheated, the ultrasonic cleaning is stopped for 3min every 40min, and the water is changed for the ultrasonic cleaner. And after the ultrasonic dispersion is finished, standing the nanofluid for 0.5h, cooling the nanofluid to room temperature, and measuring the content of suspended matters in the nanofluid by using an SS-2Z type suspended matter tester so as to analyze the stability of the nanofluid.

In order to explain the technical scheme protected by the invention more clearly, the following is further explained by combining the working process of the invention:

in the working process of the heat collector designed by the invention, cold water is firstly injected into the phase change heat storage tank 8, solar energy is received through the heat collecting layer at the lower part of the vacuum heat conducting pipe 10, the heat collecting layer transmits heat into the heat pipe 30, 18 heat conducting working media in the inner wall 19 of the heat pipe absorb the heat, the heat is gasified at the evaporation end 28 of the heat pipe, and the heat pipe penetrates through the spiral condenser gap 27 to rise. Heat is exchanged with water at the end 29 of the heat pipe condensation section that extends into the phase change thermal storage water tank 8. Exhaust gas generated at the heat pipe condensation end 29 after heat exchange flows back to the heat pipe condensation end 27, the outer edge of the spiral reinforced condenser 31 is tightly contacted with the inner wall 19 of the heat pipe, and condensed liquid drops on the inner wall can be separated from the wall surface, enter the interior of the spiral reinforced condenser and are attached to the edge of the condenser. The condensed liquid drops on the inner wall 19 of the heat tank are separated in time, so that the increase of the axial thermal resistance of the heat pipe caused by the residence and polymerization of the liquid drops on the wall surface of the conventional heat pipe is avoided. The liquid drops condensed on the outer edge of the condenser are converged to the central part of the condenser to flow downwards quickly under the action of the capillary suction pipe 25 and the drainage column 26, so that the axial thermal resistance of the heat pipe is reduced, and a steam channel and a condensate backflow channel are formed in the heat pipe due to the surface tension between a gas-liquid interface and a liquid-liquid interface. The tapered shape of the spiral reinforced condenser 31 controls the liquid content of the section, so that the steam has enough steam channels when rising from the heat pipe evaporation section 28, and can be condensed sufficiently and quickly when falling, thereby improving the working efficiency of the heat pipe 10. The temperature sensor 2 and the water level detector 9 in the phase change heat storage water tank 8 detect the water temperature and the water level in the water tank, and control the flow of the water outlet 12 and the water inlet 13. When the temperature in the phase change heat storage water tank 8 is too high, the device releases pressure through the air outlet 3.

The above embodiments are only used for illustrating the design idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes and modifications made in accordance with the principles and concepts disclosed herein are intended to be included within the scope of the present invention.