Carbon nanotube heating device and preparation method

Abstract

The present invention provides a carbon nanotube heating device and its preparation method. The device comprises a spiral heating assembly and an insulating outer layer. The spiral heating assembly is a hollow tubular structure formed by winding a carbon nanotube heating layer. The carbon nanotube heating layer comprises a carbon nanotube film layer and a structural layer. The surface of the carbon nanotube heating layer is coated with a boron nitride insulating and thermally conductive layer. The device is manufactured using supercritical dispersion and ALD processes to achieve a high-stability carbon nanotube heating device. Combined with an intelligent step-by-step control algorithm, it achieves temperature rise within seconds, demonstrating its potential for application.

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 pipes are a new type of instant hot water pipe that delivers hot water instantly, eliminating the need for waiting. They heat on demand, eliminating the need for internal heating and insulation, reducing energy loss and improving user experience. However, if the rated power of the instant hot water pipe is low, the water will heat up slowly, requiring users to wait for a long time for the water to reach the set temperature, significantly impacting the user experience. Existing technologies often use traditional resistance wire, semiconductors, or carbon fiber heating. Traditional resistance wires heat slowly (>30 seconds) and have low thermal efficiency (approximately 70%-80%). Semiconductors exhibit rapid power decay, poor high-temperature stability, and uneven water contact (resistance drift >15% at high temperatures). Carbon fiber resistance has poor uniformity and can develop localized hot spots 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, and uniform heating of heating devices 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 and heat-conducting layer is doped with rare earth elements, and the doping amount of the rare earth elements is 0.1-0.5 wt %.

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

[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 carbon nanotube film has a sheet resistance of 0.1-1000 Ω / □ (□ represents "square" and has nothing to do with the actual size of the sample), and a surface power density of 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] A second object of the present invention is to provide a method for preparing a carbon nano-heating device, comprising the following steps:

[0019] S1. Weigh carbon nanotube powder, dispersant, viscosity reducer, and solvent and prepare carbon nanotube slurry through supercritical dispersion process;

[0020] 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;

[0021] S3, coating the surface of the carbon nanotube film obtained in S2 with a boron nitride insulating layer by atomic layer deposition to obtain a multilayer structure of a spiral heating component;

[0022] S4. Under the protection of inert gas, anneal the multilayer structure of the spiral heating assembly obtained in S3 at 750° C. for 2 hours to enhance the bonding strength between the layers.

[0023] A method for preparing a carbon nanometer heating device comprises the following steps:

[0024] S1. Weigh carbon nanotube powder, dispersant, viscosity reducer, and solvent, thoroughly infiltrate and mix, and then introduce into a supercritical equipment for supercritical treatment for 30 minutes to prepare a carbon nanotube slurry;

[0025] S2. After impregnating a layer of silane coupling agent on the surface of the silicon carbide rigid pressure-resistant material, immerse it in 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 to 80 μm is deposited on the silicon carbide surface to form a carbon nanotube film layer;

[0026] S3, coating the surface of the carbon nanotube film obtained in S2 with a boron nitride insulating layer by atomic layer deposition to obtain a multilayer structure of a spiral heating component;

[0027] 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 removal, electrodes and an integrated control module are installed on the inner and outer sides of the spiral line.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] A third object of the present invention is to provide a heating control method for a carbon nanometer heating device, the method using intelligent split-range control logic, comprising the following steps:

[0032] S1. Constructing a dynamic model of heating power:

[0033]

[0034] 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).

[0035] S2. During 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.

[0036] In the steady-state stage, heating is performed at a duty cycle of 50% to 100% depending on the fluid flow rate. When heating at a duty cycle of 100%, if ΔT>30°C, the overload mode is activated and the unit is operated at maximum power until ΔT≤30°C. If ΔT is still>30°C after 10 seconds of operation, the power is cut off.

[0037] A safety protection program is set in the integrated control module of the heating device. When a leakage current greater than 5mA or an insulation resistance less than 10MΩ is detected, the power supply is immediately cut off.

[0038] Furthermore, the basic temperature is 40°C.

[0039] 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%.

[0040] Furthermore, learning and training are carried out 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, which is sent to the power adjustment unit to realize flow control.

[0041] Compared with the prior art, the beneficial technical effects of the present invention are:

[0042] The fluid in the carbon nanometer heating device of the present invention is directly heated by 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 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 achieve a temperature coefficient of resistance (TCR) of less than 0.01% / °C. A highly stable carbon nanotube heating device is prepared through supercritical dispersion and ALD processes, and combined with an intelligent step-by-step control algorithm, it achieves second-level heating, demonstrating excellent application value.

[0043] 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 in accordance with 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 specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be construed as limiting the present invention. The same reference numerals are used throughout the accompanying drawings to denote the same components.

[0045] Attachment Figure 1 This is a schematic diagram of the structure of the carbon nanometer household water heater in Example 1 of the present invention.

[0046] Attachment Figure 2 It is a schematic cross-sectional view of the spiral heating assembly of the present invention.

[0047] Attachment Figure 3 This is a diagram showing the structural relationship between the various layers of the spiral heating component of the present invention.

[0048] Attachment Figure 4 This is a schematic structural diagram of the industrial heater in Example 2 of the present invention.

[0049] Attachment Figure 5 The figure is a flow chart of the method for preparing the carbon nano-heating device of the present invention.

[0050] Attachment 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.

[0051] In the accompanying drawings, 1 is the insulating outer layer, 2 is the spiral heating component, 3 is the boron nitride insulating heat-conducting layer, 4 is the structural layer, 5 is the carbon nanotube film layer, and 6 is the heating grid. DETAILED DESCRIPTION

[0052] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although 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. Rather, 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.

[0053] Example 1 Carbon Nano-Household Water Heater

[0054] See attached Figure 1-3 A carbon nanotube 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 and thermally 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.

[0055] The resulting carbon nanostructured household water heater has a multilayer carbon nanofilm thickness of 20 μm, a boron nitride insulating and thermally conductive layer of 5 nm, and an 8 mm inner diameter spiral heating element with a 5 mm pitch. The water heater's power output ranges from 3 to 6 kW.

[0056] Example 2 Industrial Heater

[0057] An industrial heater includes a spiral heating assembly 2 and an insulating outer layer. The spiral heating assembly 2 is a hollow tubular structure formed by winding a carbon nanotube heating layer. The carbon nanotube heating layer includes a carbon nanotube thin 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 assemblies 2, and the 12 spiral heating assemblies 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 assembly is disposed within the insulating outer layer. The thickness of the alumina ceramic base layer is 50-100 μm (60 μm in this embodiment), the thickness of the polyetheretherketone outer layer is 0.2-0.5 μm (0.4 μm in this embodiment), and the inner diameter of the single-tube spiral heating assembly is 12 mm. The power of the industrial heater obtained in this embodiment is between 20 and 50 kW.

[0058] 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, the 12 spiral heating components 2 are divided into three groups and are respectively arranged at the bottom of the heating grid 6. They are fixed by the heating grid 6, which has higher heat transfer efficiency and ensures that the objects to be heated on each layer are heated evenly.

[0059] It should be noted that the structural design of the carbon nano heater in this embodiment is not only applicable to industrial heaters, but is also applicable to various household heaters and other types of industrial heating devices.

[0060] 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.

[0061] Table 1

[0062]

[0063] Example 3

[0064] A method for preparing a carbon nanometer heating device comprises the following steps:

[0065] 101. Weigh carbon nanotube powder, polyvinyl pyrrolidone, ethanolamine, and N-methyl pyrrolidone, fully soak and mix them, and then introduce them into a supercritical equipment for supercritical treatment for 30 minutes to prepare a carbon nanotube slurry; the mass percentage of carbon nanotube powder, polyvinyl pyrrolidone, ethanolamine, and N-methyl pyrrolidone is 12:2:0.3:85.

[0066] 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 it to a 120°C oven for drying. Repeat the carbon nanotube slurry impregnation-drying process three times until a carbon nanotube film with a thickness of 30 μm is deposited on the silicon carbide surface to form a carbon nanotube film layer;

[0067] 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 the boron nitride atomic deposition are: precursor pulse time 0.1-0.5 seconds, purge time 3-8 seconds.

[0068] 104. Under inert gas protection, anneal the multilayer structure of the spiral heating assembly obtained in S3 at 750°C for 2 hours to enhance interlayer bonding. After cooling and removal, electrodes and an integrated control module are installed on the inner and outer sides of the spiral. The inner and outer endpoints of the spiral heating assembly are connected to the electrodes.

[0069] Example 4

[0070] A heating control method for a carbon nanometer heating device adopts intelligent split-range control logic and includes the following steps:

[0071] S1. Constructing a dynamic model of heating power:

[0072]

[0073] 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).

[0074] Learning and training are performed based on the dynamic model of heating power to ensure 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 a fitting function, which is sent to the power adjustment unit to achieve flow control.

[0075] S2. During 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 of 40°C and enters the steady-state phase.

[0076] 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%;

[0077] When heating at 100% duty cycle, if ΔT>30℃, overload mode is enabled and the machine runs at maximum power until ΔT≤30℃. If ΔT is still>30℃ after 10 seconds, the power is cut off.

[0078] A safety protection program is set in the integrated control module of the heating device. When a leakage current greater than 5mA or an insulation resistance less than 10MΩ is detected, the power supply is immediately cut off.

[0079] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0080] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0081] 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 methods. The above-mentioned specific implementation methods are merely illustrative and not 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 protected by the present invention.

Claims

1. A heating control method for a carbon nanometer heating device, characterized in that: The method adopts intelligent split-range control logic and includes the following steps: S1. Constructing a dynamic model of heating power: ； 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） ,in, T target To set the temperature, T in is the fluid inlet temperature; S2. During 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% depending on the fluid flow rate. When heating at a duty cycle of 100%, if ΔT>30°C, the overload mode is activated and the unit is operated at maximum power until ΔT≤30°C. If ΔT is still>30°C after 10 seconds of operation, the power is cut off. A safety protection program is set in the integrated control module of the heating device. When a leakage current greater than 5mA or an insulation resistance less than 10MΩ is detected, the power supply is immediately cut off.

2. The heating control method of the carbon nanometer heating device according to claim 1, characterized in that: Learning and training are performed based on the dynamic model of heating power to ensure 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 a fitting function, which is sent to the power adjustment unit to achieve flow control.

3. 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, and the surface of the carbon nanotube heating layer is coated with a boron nitride insulating thermal conductive layer; it also includes an integrated control module, the integrated control module includes a Hall flow sensor, a distributed optical fiber temperature sensor and a power regulation unit; the integrated control module is used to execute the steps of the heating control method according to any one of claims 1-2.

4. A carbon nanotube heating device as claimed in claim 3, characterized in that: The thickness of the boron nitride insulating heat-conducting layer is 5 nm to 100 μm.

5. The carbon nanotube heating device according to claim 3, characterized in that: The boron nitride insulating and heat-conducting layer is doped with rare earth elements, and the doping amount of the rare earth elements is 0.1-0.5 wt %.

6. The carbon nanotube heating device according to claim 3, characterized in that: The carbon nanotube film layer includes a carbon nanotube film, a thermal sensor and an electrode sheet, and the structural layer is made of silicon carbide rigid pressure-resistant material.

7. The method for preparing a carbon nano-heating device according to any one of claims 3 to 6, characterized in that: The following steps are involved: S1. Weigh carbon nanotube powder, dispersant, viscosity reducer, and solvent, thoroughly infiltrate and mix, and then introduce into a supercritical equipment for supercritical treatment for 30 minutes 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, immerse it in 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 to 80 μm is deposited on the silicon carbide surface to form a carbon nanotube film layer; S3, coating the surface of the carbon nanotube film 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 removal, electrodes and an integrated control module are installed on the inner and outer sides of the spiral line.

8. The method for preparing a carbon nano-heating device according to claim 7, wherein: 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.

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