Carbon nanotube heating device and preparation method

Abstract

The invention provides a carbon nano tube heating device and a preparation method, the carbon nano tube heating device comprises a spiral heating assembly and an insulating outer layer, the spiral heating assembly is of a hollow tubular structure formed by winding a carbon nano tube heating layer, the carbon nano tube heating layer comprises a carbon nano tube thin film layer and a structural layer, and the surface of the carbon nanotube heating layer is coated with a boron nitride insulation heat conduction layer. The high-stability carbon nanotube heating device is prepared through supercritical dispersion and ALD processes, second-level temperature rise is achieved in combination with an intelligent split-ranging control algorithm, and the high-stability carbon nanotube heating device has good application value.

Description

Technical Field

[0001] The present invention relates to the technical field of electric heating equipment, and in particular to a carbon nanotube heating device and a preparation method thereof. Background Art

[0002] Instant hot water pipe is a new type of instant hot water pipe that can heat water as soon as it is pressed, without waiting. It can be heated as needed, and there is no need to store hot water such as heating and insulation inside the machine for a long time, which reduces energy loss and improves user experience. If the rated power of the instant hot water pipe is small, the water temperature will rise slowly when it comes out, and the user needs to wait for a long time before the water temperature reaches the set temperature, which greatly affects the user experience. The existing technology mostly uses traditional resistance wire, semiconductor or carbon fiber heating. The traditional resistance wire has a slow heating speed (>30 seconds) and low thermal efficiency (about 70%-80%); the semiconductor power decays quickly, the high temperature stability is poor, and the water flow contact is uneven (the resistance drift rate at high temperature is >15%); the carbon fiber resistance has poor uniformity, and local hot spots have appeared after long-term use. Summary of the invention

[0003] The present invention provides a carbon nanotube heating device and a preparation method thereof, which are used to solve the problems of low thermal efficiency, delayed thermal response, uniform heating and the like of the heating device in the prior art.

[0004] The first object of the present invention is to provide a carbon nano heating device, comprising a spiral heating component and an insulating outer layer, wherein the spiral heating component is a hollow tubular structure formed by winding a carbon nanotube heating layer, wherein the carbon nanotube heating layer comprises a carbon nanotube film layer and a structural layer, and the surface of the carbon nanotube heating layer is coated with a boron nitride insulating thermal conductive layer.

[0005] Furthermore, the inner diameter of the spiral heating component is 6-12 mm.

[0006] Furthermore, the pitch of the spiral heating component is 4-8 mm, and the spiral angle is 30°~60°.

[0007] Furthermore, the thickness of the boron nitride insulating thermal conductive layer is 5 nm to 100 μm.

[0008] Furthermore, the boron nitride insulating thermal conductive layer is doped with rare earth elements, and the doping amount of the rare earth elements is 0.1-0.5wt%.

[0009] Furthermore, the rare earth element is selected from La element.

[0010] Furthermore, the carbon nanotube film layer includes a carbon nanotube film, a thermal sensor and an electrode sheet, and the structural layer is a silicon carbide rigid pressure-resistant material.

[0011] Furthermore, there is at least one spiral heating component.

[0012] Furthermore, when there are two or more spiral heating components, the spiral heating components are connected in parallel.

[0013] Furthermore, the sheet resistance of the carbon nanotube film is 0.1-1000 Ω / □ (□ represents "square" and has nothing to do with the actual size of the sample), and its surface power density is 10-100 W / cm².

[0014] Furthermore, the defect density of the carbon nanotube film is less than 10³ / cm².

[0015] Furthermore, the carbon nano-heating device also includes an integrated control module, which includes a Hall flow sensor, a distributed optical fiber temperature sensor and a power regulation unit.

[0016] Furthermore, the Hall flow sensor is used to detect the fluid flow, the distributed optical fiber temperature sensor is used to detect the fluid temperature at the fluid inlet and outlet, and the power regulation unit is based on a neural network algorithm.

[0017] Furthermore, the measurement accuracy of the Hall flow sensor is ±1%, and the resolution of the distributed optical fiber temperature sensor is 0.1°C.

[0018] The second object of the present invention is to provide a method for preparing a carbon nano-heating device, comprising the following steps: S1, weighing carbon nanotube powder, dispersant, viscosity reducer, and solvent through a supercritical dispersion process to prepare a carbon nanotube slurry; S2, after impregnating a layer of silane coupling agent on the surface of the silicon carbide rigid pressure-resistant material, immersing the carbon nanotube slurry obtained in S1 and drying it to form a carbon nanotube film layer; S3, coating the surface of the carbon nanotube film layer obtained in S2 with a boron nitride insulating layer by atomic layer deposition to obtain a multilayer structure of a spiral heating component; S4. Under the protection of inert gas, the multilayer structure of the spiral heating assembly obtained in S3 is annealed at 750° C. for 2 hours to enhance the interlayer bonding strength.

[0019] A method for preparing a carbon nanometer heating device comprises the following steps: S1, weighing carbon nanotube powder, dispersant, viscosity reducer, and solvent, fully infiltrating and mixing, and then introducing into a supercritical equipment for supercritical treatment for 30 minutes to obtain a carbon nanotube slurry; S2, after impregnating a layer of silane coupling agent on the surface of the silicon carbide rigid pressure-resistant material, immerse the carbon nanotube slurry obtained in S1, and then transfer it to an oven for drying, repeat the carbon nanotube slurry impregnation-drying process several times until a carbon nanotube film with a thickness of 10-80 μm is deposited on the surface of the silicon carbide to form a carbon nanotube film layer; S3, coating the surface of the carbon nanotube film layer obtained in S2 with a boron nitride insulating layer by atomic layer deposition to obtain a multilayer structure of a spiral heating component; S4. Under the protection of inert gas, the multilayer structure of the spiral heating assembly obtained in S3 is annealed at 750° C. for 2 hours to enhance the interlayer bonding strength. After cooling and taking out, electrodes and an integrated control module are added to the inner and outer sides of the spiral line.

[0020] Furthermore, the mass percentages of the carbon nanotube powder, dispersant, viscosity reducer and solvent are 5-18: 1-3: 0.1-0.5: 78.5-93.9.

[0021] Furthermore, the dispersant is selected from polyacrylic acid, polyvinyl alcohol, polyvinyl pyrrolidone or polyethylene glycol; the viscosity reducer is selected from ethanolamine or piperazine; and the solvent is selected from water, N-methylpyrrolidone or alcohols.

[0022] Furthermore, the pulse timing parameters of boron nitride deposition in step S3 are: precursor pulse time 0.1-0.5 seconds, purge time 3-8 seconds.

[0023] The third object of the present invention is to provide a heating control method for a carbon nanometer heating device, the method adopts intelligent split-range control logic, and comprises the following steps: S1. Constructing dynamic model of heating power:

[0024] in, ρ is the fluid density, C p is the specific heat capacity, Q is the fluid flow rate, η For system efficiency, k is the dynamic correction coefficient, ΔT=T target -T in （t） ( T target To set the temperature, T in is the fluid inlet temperature).

[0025] S2. In the startup phase, when the Hall flow sensor detects a flow rate Q ≥ 1L / min, it is preheated at a 50% duty cycle until the fluid outlet temperature reaches the base temperature and enters the steady-state phase; In the steady-state stage, heating is performed at a duty cycle of 50% to 100% according to the fluid flow rate; when heating at a duty cycle of 100%, if ΔT>30°C, the overload mode is enabled and the system is operated at maximum power until ΔT≤30°C. If ΔT is still>30°C after 10 seconds of operation, the power supply is cut off; A safety protection program is provided in the integrated control module of the heating device. When a leakage current > 5mA or an insulation resistance < 10MΩ is detected, the power supply is immediately cut off.

[0026] Furthermore, the basic temperature is 40°C.

[0027] Furthermore, in the steady-state stage, when the fluid pressure is greater than 0.6 MPa, the system automatically increases the duty cycle by 5 to 10%.

[0028] Furthermore, learning and training are performed according to the dynamic model of heating power to make the actual power deviation less than 1.5%. After the training is completed, the parameters under different ambient temperatures are interpolated and fitted to obtain a fitting function, and the fitting function is sent to the power adjustment unit to realize the control of the flow.

[0029] Compared with the prior art, the beneficial technical effects of the present invention are: The fluid in the carbon nanometer heating device of the present invention is directly heated through the internal channel of the spiral heating component, and the heat transfer efficiency is greater than 98%. The surface power density of the carbon nanometer heating device obtained by the method of the present invention reaches 10-50W / cm², which is much higher than the 4.5W / cm² of the traditional resistance wire; the thermal conductivity is greater than 3000 W / m·K, and the electrical conductivity is greater than 10 6 The present invention uses a boron nitride insulating thermal conductive layer design to make the temperature coefficient of resistance (TCR) less than 0.01% / ℃; a high-stability carbon nanotube heating device is prepared through supercritical dispersion and ALD process, and combined with an intelligent step-by-step control algorithm to achieve second-level heating, which has great application value.

[0030] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment and are not considered to be limitations of the present invention. In addition, the same reference symbols are used to represent the same components throughout the accompanying drawings.

[0032] Attached Figure 1This is a schematic diagram of the structure of the carbon nanometer household water heater in Example 1 of the present invention.

[0033] Attached Figure 2 It is a schematic cross-sectional view of the spiral heating assembly of the present invention.

[0034] Attached Figure 3 This is a diagram showing the structural relationship of each layer of the spiral heating component of the present invention.

[0035] Attached Figure 4 This is a schematic diagram of the structure of the industrial heater in Example 2 of the present invention.

[0036] Attached Figure 5 The present invention is a flow chart of the method for preparing the carbon nano heating device.

[0037] Attached Figure 6 This is an exemplary control logic diagram of the heating control method of the nano-heating device in Example 4 of the present invention.

[0038] In the attached drawings, 1 is an insulating outer layer, 2 is a spiral heating component, 3 is a boron nitride insulating heat-conducting layer, 4 is a structural layer, 5 is a carbon nanotube film layer, and 6 is a heating grid. DETAILED DESCRIPTION

[0039] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0040] Example 1 Carbon nanotube household water heater See attached Figure 1-3 A carbon nano household water heater includes a spiral heating component 2 and an insulating outer layer 1. The spiral heating component 2 is a hollow tubular structure formed by winding a carbon nanotube heating layer. The carbon nanotube heating layer includes a carbon nanotube film layer 5 and a structural layer 4. The surface of the carbon nanotube heating layer is coated with a boron nitride insulating thermal conductive layer 3. The insulating outer layer 1 is a PPR tube, so that the spiral heating component 2 is arranged inside the PPR tube.

[0041] The thickness of the multilayer carbon nanofilm in the obtained carbon nano household water heater is 20μm, the thickness of the boron nitride insulating heat conductive layer is 5nm, the inner diameter of the obtained spiral heating component is 8mm, and the pitch is 5mm. The power of the water heater is 3~6kW.

[0042] Example 2 Industrial Heater An industrial heater includes a spiral heating component 2 and an insulating outer layer. The spiral heating component 2 is a hollow tubular structure formed by winding a carbon nanotube heating layer. The carbon nanotube heating layer includes a carbon nanotube film layer 5 and a structural layer 4. The surface of the carbon nanotube heating layer is coated with a boron nitride insulating thermal conductive layer 3. There are 12 spiral heating components 2, and the 12 spiral heating components 2 are connected in parallel. The insulating outer layer is a combination of an alumina ceramic base layer and a polyetheretherketone outer layer, so that the spiral heating component is arranged inside the insulating outer layer. The thickness of the alumina ceramic base layer is 50~100μm (the thickness is 60μm in this embodiment), the thickness of the polyetheretherketone outer layer is 0.2~0.5μm (the thickness is 0.4μm in this embodiment), and the inner diameter of the single-tube spiral heating component is 12mm. The power of the industrial heater obtained in this embodiment is between 20~50kW.

[0043] See attached Figure 2-4 Preferably, each spiral heating component 2 in the industrial heater is designed in parallel with multiple layers, and each layer is designed with at least two parallel spiral heating components, which increases the surface area of ​​the nanotube film and improves the effective power of the heater. Figure 4 In the industrial heater, 12 spiral heating components 2 are divided into three groups and are respectively arranged at the bottom of the heating grid 6 and fixed by the heating grid 6, which has higher heat transfer efficiency and ensures that each layer of the objects to be heated are heated evenly.

[0044] It should be noted that the structural design of the carbon nano heater in this embodiment is not only applicable to industrial heaters, but also to various household heaters and other types of industrial heating devices.

[0045] The spiral heating component in this embodiment is replaced with a conventional iron-chromium-aluminum alloy resistance wire. The main technical effects (thermal response time from 20°C to 60°C, steady-state thermal efficiency, power density, insulation resistance, etc.) are compared as shown in Table 1.

[0046] Table 1

[0047] Example 3 A method for preparing a carbon nanometer heating device comprises the following steps: 101. Weigh carbon nanotube powder, polyvinyl pyrrolidone, ethanolamine and N-methyl pyrrolidone, fully wet and mix them, and then introduce them into a supercritical equipment for supercritical treatment for 30 minutes to obtain carbon nanotube slurry; the mass percentage of carbon nanotube powder, polyvinyl pyrrolidone, ethanolamine and N-methyl pyrrolidone is 12:2:0.3:85.

[0048] 102. After impregnating a layer of silane coupling agent on the surface of the silicon carbide rigid pressure-resistant material, immerse the carbon nanotube slurry obtained in S1, and then transfer to a 120° C. oven for drying. Repeat the carbon nanotube slurry impregnation-drying process 3 times until a carbon nanotube film with a thickness of 30 μm is deposited on the surface of the silicon carbide to form a carbon nanotube film layer; 103. The surface of the carbon nanotube film layer obtained on S2 by atomic layer deposition is coated with a boron nitride insulating layer to obtain a multilayer structure of a spiral heating component; the pulse timing parameters of boron nitride atomic deposition are: precursor pulse time 0.1-0.5 seconds, purge time 3-8 seconds.

[0049] 104. Under the protection of inert gas, the multilayer structure of the spiral heating assembly obtained in S3 is annealed at 750° C. for 2 hours to enhance the interlayer bonding strength, and after cooling and taking out, electrodes and an integrated control module are installed on the inner and outer sides of the spiral line. The inner and outer ends of the spiral heating assembly are connected to the electrodes.

[0050] Example 4 A heating control method for a carbon nanometer heating device adopts intelligent split-range control logic and comprises the following steps: S1. Constructing dynamic model of heating power:

[0051] in, ρ is the fluid density, C p is the specific heat capacity, Q is the fluid flow rate, η For system efficiency, k is the dynamic correction coefficient, ΔT=T target -T in （t） ( T target To set the temperature, T in is the fluid inlet temperature).

[0052] The dynamic model of heating power is used for learning and training so that the actual power deviation is less than 1.5%. After the training is completed, the parameters under different ambient temperatures are interpolated and fitted to obtain the fitting function, which is sent to the power adjustment unit to realize the control of the flow.

[0053] S2. In the startup phase, when the Hall flow sensor detects that the flow rate Q ≥ 1L / min, it is preheated at a duty cycle of 50% until the fluid outlet temperature reaches the base temperature of 40°C and enters the steady-state phase; In the steady-state stage, heating is performed at a duty cycle of 50% to 100% according to the fluid flow rate; when the fluid pressure is greater than 0.6 MPa, the system automatically increases the duty cycle by 5 to 10%; When heating at 100% duty cycle, if ΔT>30℃, overload mode is enabled and the system runs at maximum power until ΔT≤30℃. If ΔT is still>30℃ after 10 seconds, the power is cut off. A safety protection program is provided in the integrated control module of the heating device. When a leakage current > 5mA or an insulation resistance < 10MΩ is detected, the power supply is immediately cut off.

[0054] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0055] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0056] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A carbon nano heating device, characterized in that: It includes a spiral heating component and an insulating outer layer. The spiral heating component is a hollow tubular structure formed by winding a carbon nanotube heating layer. The carbon nanotube heating layer includes a carbon nanotube film layer and a structural layer. The surface of the carbon nanotube heating layer is coated with a boron nitride insulating thermal conductive layer.

2. A carbon nanotube heating device as claimed in claim 1, characterized in that: The thickness of the boron nitride insulating heat-conducting layer is 5nm-100μm.

3. A carbon nanotube heating device as claimed in claim 1, characterized in that: The boron nitride insulating thermal conductive layer is doped with rare earth elements, and the doping amount of the rare earth elements is 0.1-0.5wt%.

4. A carbon nanotube heating device as claimed in claim 1, characterized in that: The carbon nanotube film layer comprises a carbon nanotube film, a thermal sensor and an electrode sheet, and the structural layer is a silicon carbide rigid pressure-resistant material.

5. A carbon nanotube heating device as claimed in claim 1, characterized in that: The carbon nanometer heating device also includes an integrated control module, which includes a Hall flow sensor, a distributed optical fiber temperature sensor and a power regulation unit.

6. A method for preparing the carbon nano heating device according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, weighing carbon nanotube powder, dispersant, viscosity reducer, and solvent through a supercritical dispersion process to prepare a carbon nanotube slurry; S2, after impregnating a layer of silane coupling agent on the surface of the silicon carbide rigid pressure-resistant material, immersing the carbon nanotube slurry obtained in S1 and drying it to form a carbon nanotube film layer; S3, coating the surface of the carbon nanotube film layer obtained in S2 with a boron nitride insulating layer by atomic layer deposition to obtain a multilayer structure of a spiral heating component; S4. Under the protection of inert gas, the multilayer structure of the spiral heating assembly obtained in S3 is annealed at 750° C. for 2 hours to enhance the interlayer bonding strength.

7. A method for preparing a carbon nano heating device as claimed in claim 6, characterized in that: The following steps are involved: S1, weighing carbon nanotube powder, dispersant, viscosity reducer, and solvent, fully infiltrating and mixing, and then introducing into a supercritical equipment for supercritical treatment for 30 minutes to obtain a carbon nanotube slurry; S2, after impregnating a layer of silane coupling agent on the surface of the silicon carbide rigid pressure-resistant material, immerse the carbon nanotube slurry obtained in S1, and then transfer it to an oven for drying, repeat the carbon nanotube slurry impregnation-drying process several times until a carbon nanotube film with a thickness of 10-80 μm is deposited on the surface of the silicon carbide to form a carbon nanotube film layer; S3, coating the surface of the carbon nanotube film layer obtained in S2 with a boron nitride insulating layer by atomic layer deposition to obtain a multilayer structure of a spiral heating component; S4. Under the protection of inert gas, the multilayer structure of the spiral heating assembly obtained in S3 is annealed at 750° C. for 2 hours to enhance the interlayer bonding strength. After cooling and taking out, electrodes and an integrated control module are added to the inner and outer sides of the spiral line.

8. A method for preparing a carbon nano-heating device as claimed in claim 6 or 7, characterized in that: The mass percentages of the carbon nanotube powder, dispersant, viscosity reducer and solvent are 5-18:1-3:0.1-0.5:78.5-93.

9.

9. A heating control method of the carbon nano heating device according to any one of claims 1 to 5, characterized in that: The method adopts intelligent split-range control logic and includes the following steps: S1. Construct dynamic model of heating power: ， in, ρ is the fluid density, is the specific heat capacity, Q is the fluid flow rate, η For system efficiency, k is the dynamic correction coefficient, ΔT= T target -T in （t）， in, T target To set the temperature, T in is the fluid inlet temperature; S2. In the startup phase, when the Hall flow sensor detects a flow rate Q ≥ 1L / min, it is preheated at a 50% duty cycle until the fluid outlet temperature reaches the base temperature and enters the steady-state phase; In the steady-state stage, heating is performed at a duty cycle of 50% to 100% according to the fluid flow rate; when heating at a duty cycle of 100%, if ΔT>30°C, the overload mode is enabled and the system is operated at maximum power until ΔT≤30°C. If ΔT is still>30°C after 10 seconds of operation, the power supply is cut off; A safety protection program is provided in the integrated control module of the heating device. When a leakage current > 5mA or an insulation resistance < 10MΩ is detected, the power supply is immediately cut off.

10. A heating control method for a carbon nano heating device as claimed in claim 9, characterized in that: The dynamic model of heating power is used for learning and training so that the actual power deviation is less than 1.5%. After the training is completed, the parameters under different ambient temperatures are interpolated and fitted to obtain the fitting function, which is sent to the power adjustment unit to achieve flow control.

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