A magnetic flux tube through-core wrap-around water heating device

Abstract

The application discloses a magnetic flux tube through-hole winding type water heating device and relates to the technical field of electromagnetic induction heating and magnetic devices. The device solves the problem of the drawbacks of the circumferential winding coil in the tubular magnetic core or magnetic flux tube scene. The through-hole winding winding group comprises an inner cavity axial conductor section and an outer wall axial return line section. The multiple-turn conductor of the inner cavity axial conductor section adopts a through-hole winding structure and is arranged between a metal heat exchange pipe and a ferrous pipe magnetic core. The multiple-turn conductor of the outer wall axial return line section adopts a through-hole winding structure and is arranged outside the ferrous pipe magnetic core. Through the symmetrical arrangement of the inner and outer coaxial return conductors, the main magnetic flux can be closed in the ferrous pipe magnetic core to reduce the magnetic flux leakage. Meanwhile, the length of the end return circuit is shortened, the copper loss caused by the proximity effect is reduced, the coupling efficiency on the metal heat exchange pipe is improved, and the electric loss is reduced. The application is suitable for the scenes of straight pipe type hot water heating and fluid rapid heating.

Description

Technical Field

[0001] This invention relates to the technical field of electromagnetic induction heating and magnetic devices, and in particular to a magnetic flux tube through-hole type water heating device. Background Technology

[0002] Existing straight-tube electromagnetic heating devices typically generate an alternating magnetic field by circumferentially winding a coil around the core or metal tube to inductively heat the metal object. In tubular core or flux tube scenarios, circumferentially wound coils often present the following problems: 1. Longer end loops and leads lead to increased additional resistance and parasitic inductance, resulting in higher copper losses; 2. Concentration of the windings on the outer side of the core leads to significant flux leakage, decreased coupling efficiency, and potential additional eddy current losses in surrounding metal components; 3. Significant skin and proximity effects at higher frequencies increase the AC resistance of the windings, causing severe heat generation; 4. For long straight tube structures, insufficient reliability in coil fixation and insulation leads to vibration, noise, and wear. Therefore, a winding structure that achieves high coupling, low leakage flux, low copper losses, and easy engineering assembly is needed on long straight iron tube flux tubes. Summary of the Invention

[0003] To address the drawbacks of circumferentially wound coils in tubular magnetic cores or flux tube scenarios, the present invention aims to provide a flux tube through-core wound water heating device. By arranging axial conductor segments inside and outside the iron tube magnetic core and reversing them at the ends to form a closed loop, the magnetic flux is effectively closed within the magnetic core and efficiently coupled to the metal heat exchange tube, reducing leakage flux and winding electrical losses, and improving the reliability of structural assembly.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A flux tube through-wound water heating device includes: an iron tube core 1, a metal heat exchange tube 2, a through-wound winding, and end caps 5. The iron tube core 1 is a hollow cylindrical structure, and end caps 5 are installed at both ends of the iron tube core 1. The metal heat exchange tube 2 is located inside the iron tube core 1 and is coaxially arranged with the iron tube core 1. A water flow channel is provided inside the metal heat exchange tube 2. The end caps 5 are provided with wire passage holes 5a for the through-wound winding to pass through. The through-wound winding includes: an inner cavity axial conductor section 3 and an outer wall axial return section 4. The multi-turn conductor of the inner cavity axial conductor section 3 adopts a through-wound winding structure and is located between the metal heat exchange tube 2 and the iron tube core 1. The multi-turn conductor of the outer wall axial return section 4 adopts a through-wound winding structure and is located outside the iron tube core 1. The two ends of the through-wound winding are respectively connected to two terminals 8.

[0006] The above-mentioned flux tube through-core water heating device includes an iron tube core 1 comprising an iron tube core segment 1a and an insulating gasket 1b. Multiple iron tube core segments 1a are arranged axially, and an insulating gasket 1b is provided between any two adjacent iron tube core segments 1a. The metal heat exchange tube 2 is made of ferromagnetic metal material.

[0007] The above-mentioned magnetic flux tube through-core rewinding water heating device further includes: a heat insulation protective sleeve 9, which is sleeved on the outer surface of the iron pipe magnetic core 1, and is used to axially pre-tighten and fix multiple iron pipe magnetic core sections 1a and multiple insulating gaskets 1b.

[0008] The above-mentioned flux tube through-hole winding water heating device further includes: an outer winding carrier 11, the outer surface of the heat insulation protective sleeve 9 is covered with the outer winding carrier 11, the outer surface of the outer winding carrier 11 is provided with multiple axially extending outer guide grooves, and the outer wall axial return line segment 4 is wound on the outer winding carrier 11 by through-hole winding.

[0009] The aforementioned flux tube through-hole winding water heating device further includes: an inner conductor guide groove sleeve 10, which is located inside the iron tube magnetic core 1 and coaxially arranged with the iron tube magnetic core 1. The outer surface of the inner conductor guide groove sleeve 10 is provided with multiple inner guide grooves extending along the axial direction. The axial conductor section 3 of the inner cavity is wound around the inner conductor guide groove sleeve 10 by a through-hole winding method. The metal heat exchange tube 2 is located inside the inner conductor guide groove sleeve 10.

[0010] In the aforementioned magnetic flux tube through-hole rewinding water heating device, the inner wall of the wire hole 5a is provided with an insulating sleeve, which is used to pass through the through-hole rewinding winding.

[0011] The aforementioned magnetic flux tube through-hole revolving water heating device further includes: an inlet connector 6 and an outlet connector 7. The inlet connector 6 and the outlet connector 7 are respectively installed on the two end caps 5, and the inlet connector 6 and the outlet connector 7 are respectively connected to the two ends of the metal heat exchange tube 2.

[0012] In the aforementioned flux tube through-hole rewinding water heating device, the through-hole rewinding winding is a stranded wire or a Litz wire.

[0013] In the above-mentioned magnetic flux tube through-hole winding water heating device, the winding directions of the inner cavity axial conductor section 3 and the outer wall axial return line section 4 are opposite, and the inner cavity axial conductor section 3 and the outer wall axial return line section 4 are arranged symmetrically in the circumferential direction.

[0014] A water heating system includes a magnetic flux tube through-hole type water heating device, which further includes a power supply 12. The inner cavity axial conductor section 3 and the outer wall axial return line section 4 are both connected to the power supply 12 through terminals 8. The power supply 12 is used to provide alternating current to the inner cavity axial conductor section 3 and the outer wall axial return line section 4.

[0015] It also includes a temperature sensor 13 and a controller 14. The temperature sensor 13 is used to detect the water temperature through the metal heat exchange tube 2, and the controller 14 is used to adjust the output power of the power supply 12. The controller 14 adopts constant power control, constant outlet temperature control or segmented power control and triggers protection shutdown when water shortage, over-temperature or over-current occurs.

[0016] The present invention, by employing the above-mentioned technology, has the following positive effects compared with the prior art:

[0017] (1) In this invention, the inner and outer axial conductors form a coaxial circuit, the main magnetic flux tends to close inside the iron tube core, the leakage flux is reduced, and the coupling efficiency is improved;

[0018] (2) In this invention, the end circuit can be shortened in a structured manner, the equivalent resistance and AC resistance of the winding are reduced, and the copper loss is reduced;

[0019] (3) In this invention, the inner and outer conductors are arranged circumferentially and symmetrically, which reduces the leakage magnetic field and the loss due to proximity effect, which is beneficial to reduce the temperature rise and improve the system efficiency;

[0020] (4) In this invention, a segmented magnetic core and guide groove fixing structure is adopted, which is suitable for the assembly of 1 m long straight pipes, and has higher reliability and maintainability. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a magnetic flux tube through-hole type water heating device according to the present invention.

[0022] Figure 2 This is a longitudinal cross-sectional view of a magnetic flux tube through-hole type water heating device according to the present invention.

[0023] Figure 3 This is a schematic diagram of the cross-sectional structure of a magnetic flux tube through-hole revolving water heating device according to the present invention.

[0024] Figure 4 This is a schematic diagram of the current path of the through-winding winding of a flux tube through-winding water heating device according to the present invention.

[0025] Figure 5 This is a schematic diagram of a water heating system according to the present invention.

[0026] In the attached diagram: 1. Iron tube magnetic core; 1a. Iron tube magnetic core section; 1b. Insulating gasket; 2. Metal heat exchange tube; 3. Inner cavity axial conductor section; 4. Outer wall axial return section; 5. End cap; 5a. Through hole; 6. Water inlet connector; 7. Water outlet connector; 8. Terminal; 9. Heat insulation protective sleeve; 10. Inner conductor guide groove sleeve; 11. Outer winding carrier; 12. Power supply; 13. Temperature sensor; 14. Controller. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0028] Please refer to Figures 1 to 5 As shown, a flux-tube through-hole type water heating device is illustrated, comprising: an iron tube core 1, which is a hollow cylindrical structure with an axially penetrating inner hole; a metal heat exchange tube 2, which is coaxially disposed within the inner hole of the iron tube core 1 and forms a water flow channel for fluid passage; and a through-hole winding comprising: an inner cavity axial conductor section 3 and an outer wall axial return line section 4, which are composed of multiple turns of conductor, and each turn of conductor comprises: an inner cavity axial conductor section 3 located between the inner hole of the iron tube core 1 and the outer wall of the metal heat exchange tube 2, and an outer wall axial return line section 4 located outside the iron tube core 1; wherein, the inner cavity axial conductor section 3 and the outer wall axial return line section 4 are connected at at least one end of the device through an end-passing structure to form a closed current loop, thereby forming a main closed magnetic flux in the iron tube core 1 when energized and generating induction heating for the metal heat exchange tube 2.

[0029] Furthermore, in a preferred embodiment, the iron pipe magnetic core 1 is formed by assembling multiple iron pipe magnetic core segments 1a along the axial direction, with insulating gaskets 1b provided between adjacent iron pipe magnetic core segments 1a, and the multiple iron pipe magnetic core segments 1a are axially pre-tightened and fixed by heat-insulating protective sleeves 9 and / or pull rod clamping structures.

[0030] Furthermore, in a preferred embodiment, the device further includes an inner conductor guide groove sleeve 10, which is disposed in the inner hole of the iron pipe magnetic core 1 and coaxial with the iron pipe magnetic core 1. The outer surface of the inner conductor guide groove sleeve 10 is provided with multiple inner guide grooves extending axially, which are used to limit and fix the axial conductor segment 3 of the inner cavity.

[0031] Furthermore, in a preferred embodiment, an outer winding carrier 11 is provided on the outside of the heat insulation protective sleeve 9. The outer surface of the outer winding carrier 11 is provided with multiple axially extending outer guide grooves for limiting and fixing the axial return line segment 4 of the outer wall.

[0032] Furthermore, in a preferred embodiment, the end wire passage structure includes an end cap 5 and a wire passage hole 5a, wherein the wire passage hole 5a is provided with an insulating sleeve to prevent the conductor insulation layer from being worn or broken down at the wire passage.

[0033] Furthermore, in a preferred embodiment, the conductor is stranded wire or Litz wire, or flat copper strip / hollow copper tube; the device epoxy impregnates or pots the winding to suppress vibration and improve the withstand voltage level.

[0034] Furthermore, in a preferred embodiment, the metal heat exchange tube 2 is made of a ferromagnetic metal material, including ferromagnetic stainless steel or low-carbon steel, to improve induction heating efficiency.

[0035] Furthermore, in a preferred embodiment, the inner cavity axial conductor segment 3 and the outer wall axial return segment 4 are arranged symmetrically in the circumferential direction to reduce the leakage magnetic field and reduce the proximity effect loss of the winding.

[0036] Furthermore, in a preferred embodiment, the device has a double-ended lead-out structure, with the starting end terminal 8 of the through-core rewinding winding located at the first end cover 5 of the device, and the ending end terminal 8 of the through-core rewinding winding located at the second end cover 5 of the device; or, the device has a single-ended lead-out structure, with the ending wire led back to the end cover 5 of the first end through the return lead-in channel, and both the starting end terminal 8 of the through-core rewinding winding and the ending end terminal 8 of the through-core rewinding winding located at the end cover 5 of the first end.

[0037] Furthermore, in a preferred embodiment, the effective length of the iron tube magnetic core 1 is 800-1200 mm, the outer diameter of the iron tube magnetic core 1 is 110-170 mm, and the inner diameter is 90-140 mm; the outer diameter of the metal heat exchange tube 2 is 50-100 mm.

[0038] A water heating system includes: a power supply 12 and a flux tube through-wound water heating device, wherein the power supply 12 provides alternating current to the through-wound windings 3 and 4; the water heating system also includes a temperature sensor 13 and a controller 14, wherein the controller 14 adjusts the output power of the power supply 12 according to the inlet / outlet water temperature to achieve a target temperature rise.

[0039] Furthermore, in a preferred embodiment, the controller 14 employs any one of constant power control, constant outlet temperature control, or segmented power control, and triggers a protective shutdown when water shortage, over-temperature, or over-current occurs.

[0040] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention.

[0041] In addition to the above, the present invention also has the following embodiments:

[0042] In a further embodiment of the present invention, preferably, the iron pipe magnetic core 1 is assembled in sections and is pressed and fixed by the heat insulation protective sleeve 9 and the pull rod;

[0043] In a further embodiment of the present invention, preferably, an inner conductor guide groove sleeve 10 is provided in the inner hole of the iron pipe, and an outer winding carrier 11 is provided on the outside of the heat insulation protective sleeve 9, which are respectively used to fix the inner cavity axial conductor section 3 and the outer wall axial return line section 4.

[0044] In a further embodiment of the present invention, preferably, the conductor is made of Litz wire or copper stranded wire and is impregnated and cured to reduce high-frequency loss and improve insulation durability.

[0045] In a further embodiment of the present invention, this is as follows Figures 1-3As shown, the device of the present invention includes an iron tube magnetic core 1, a metal heat exchange tube 2, a through-wound winding (an inner cavity axial conductor section 3 and an outer wall axial return line section 4), an end cap 5, a water inlet connector 6, a water outlet connector 7, a terminal 8, a heat insulation protective sleeve 9, and an inner conductor guide groove sleeve 10 and / or an outer winding carrier 11. The iron tube magnetic core 1 has a hollow cylindrical structure, and the metal heat exchange tube 2 is coaxially arranged in its inner hole to form a water flow channel. The through-wound winding is composed of multiple turns of conductor, each turn of conductor forming an axial conductor section 3 in the inner cavity and an axial return line section 4 on the outer side, and is reversed at the end via a wire passage hole 5a on the end cap 5.

[0046] In a further embodiment of the present invention, in a preferred embodiment: the effective magnetic core length is 1000 mm; the iron tube magnetic core 1 is assembled from 5 iron tube magnetic core segments 1a, each segment being 200 mm long, with an outer diameter of 140 mm and an inner diameter of 120 mm, and an insulating gasket 1b with a thickness of 0.3-0.5 mm is provided between adjacent segments. The heat insulation protective sleeve 9 is a GFRP tube with an inner diameter of 141 mm, an outer diameter of 147 mm, and a length of 1020 mm, used to provide radial protection for the magnetic core segments and to provide axial pre-tightening in conjunction with the end clamping structure. The metal heat exchange tube 2 has an outer diameter of 76 mm, an inner diameter of 68 mm, and a length of 1000 mm, and is made of ferromagnetic stainless steel or low carbon steel; the inner conductor guide groove sleeve 10 has an outer diameter of 119 mm, an inner diameter of 78 mm, and a length of 1000 mm, and its outer surface is evenly distributed with 10 inner guide grooves along the circumference, each groove being 9 mm wide and 6.5 mm deep. The outer winding carrier 11 has an inner diameter of 147 mm, an outer diameter of 160 mm, and a length of 1000 mm. Its outer surface also has 10 external guide grooves for fixing the axial return segment 4 on the outer wall. The conductor uses an equivalent cross-sectional area of ​​25-35 mm². 2 The Litz wire or flexible copper stranded wire has an outer diameter (including insulation) of approximately 8 mm and 10 turns.

[0047] In a further embodiment of the present invention, the working principle and usage process of the present invention are as follows:

[0048] like Figure 4 As shown, when the power supply 12 supplies alternating current to the through-core winding, the inner cavity axial conductor segment 3 and the outer wall axial loop segment 4 form a coaxial loop. Since the current directions of the inner and outer conductors are opposite and the radial distance is small, the magnetic fields of the external space cancel each other out, and the magnetic flux tends to close in the magnetic circuit of the iron tube core 1, thereby generating eddy currents in the metal heat exchange tube 2 and generating heat through hysteresis / resistance loss. The heat is transferred to the fluid inside the tube through the tube wall to achieve heating.

[0049] The system can be configured with inlet / outlet temperature sensors 13 and controller 14. Controller 14 adjusts the output of power supply 12 according to the target outlet temperature (constant power or constant temperature control). When abnormalities such as water shortage, over-temperature, or overcurrent are detected, controller 14 triggers a protective shutdown to improve system safety and reliability.

[0050] In a further embodiment of the present invention, the present invention is an induction heating device that utilizes an iron pipe flux tube and an external excitation winding to achieve controllable heating of flowing water in a coaxial metal water pipe. By improving the winding method from "solenoid circumferential winding" to "through-the-center winding", the electromagnetic energy utilization efficiency is improved, the winding electrical loss and leakage magnetic field are reduced under the same heating task, while maintaining the manufacturability of the structure and the safety and reliability of operation.

[0051] In a further embodiment of the present invention, the present invention consists of four parts: "magnetic flux tube heating assembly + power supply and control + fluid and structural components + sensing and protection"; the magnetic flux tube heating assembly includes: a hollow iron tube core 1, a through-wound winding (10 turns or more), an internal metal heat exchange tube 2 (iron / copper), and end insulation and wire lead-out structure (end cover 5 and its wire through hole 5a); the power supply and control includes: DC bus or AC input, inverter / controllable current source, resonance compensation (optional), current / voltage sampling, and temperature closed-loop control; the fluid and structural components include: water inlet connector 6, water outlet connector 7, seals, support and positioning, outer shell (heat insulation protective sleeve 9) and insulation layer (optional), and maintenance and disassembly structure; the sensing and protection includes: water temperature sensor 13, winding temperature (thermocouple / NTC), overcurrent and overvoltage protection, leakage protection, and dry burning / current interruption protection.

[0052] In a further embodiment of the present invention, the heating power requirement is estimated as follows: Based on the law of conservation of energy, the heat transfer power required to achieve the target temperature rise is approximately:

[0053] P to water = ṁ·c p ·ΔT = ρ·Q·c p ·ΔT

[0054] Where Q is the volumetric flow rate (m³ / s). Taking Q = 1 L / min and ΔT = 10℃ as an example:

[0055] Q=1e -3 / 60≈1.67e -5 m³ / s, P≈998*1.67e -5 *4182*10≈700W.

[0056] This calculation is used to give the power level; in practice, heat dissipation and efficiency η also need to be considered.

[0057] P in ≈Pto water / η

[0058] First, determine ΔT and Q, then the required P can be determined. to water With P in The magnitude allows us to infer the range of power supply and winding current.

[0059] In a further embodiment of the invention, if the target power is relatively high and rapid heating is desired, a kHz level (e.g., 5-30kHz) can be considered. Eddy current heating efficiency is high, but winding AC losses and EMI control are more critical. If a simple power supply is desired, 50 / 60Hz can also be achieved, but the current is often higher for the same power, and the device size may be larger. The iron tube material needs to be matched with the frequency; for high frequencies, high-frequency grades of MnZn / NiZn are selected. The hysteresis loss of the iron tube is more significant at low and mid frequencies, and at high frequencies, it may be more biased towards eddy currents and surface heating.

[0060] In a further embodiment of the present invention, the winding design must simultaneously meet the following requirements: current carrying capacity, temperature rise limitation, withstand voltage insulation, and windability and assembly; the process includes: 1. Determining the current range: obtaining the target P through simulation / experimentation. to water I rms 2. Select wire diameter / Litz wire specifications: Initially select the cross-sectional area based on the allowable current density J (natural cooling is typically 2-5 A / mm², forced cooling can be higher); prioritize Litz wire for high frequencies to reduce AC resistance; 3. Estimate wire length and resistance: Estimate the total bus length based on the path length per turn (internal + external return + end connection), and calculate R. dc Then, combined with frequency estimation, R ac ≈k ac ·R dc (k) ac 4. Copper consumption calculation: P (determined by skin / proximity) cu =I rms 2 ·R ac And match the heat dissipation conditions (the winding is allowed to rise in temperature); 5. Layout optimization: the turns are evenly distributed, and the end bends are reinforced with protective sleeves to avoid sharp corners and scratches.

[0061] In a further embodiment of the invention, insulation and safety margin: Between the winding and the iron pipe: a minimum 0.5-1.0 mm insulation layer (temperature resistant / abrasion resistant) is recommended, with guide bushings added to the ends. Winding leads: High-temperature resistant silicone wire or fiberglass sheathing is used to prevent contact with sharp edges. Water circuit sealing: Temperature resistant sealing rings are used between the metal pipe and the external joint to prevent moisture from entering the gap between the winding and the iron pipe. Electrical protection: Overcurrent, overtemperature, and leakage protection; it is recommended to set "automatic power reduction / shutdown upon current interruption".

[0062] In a further embodiment of the present invention, the winding process of the through-hole winding includes: making a simple winding fixture: installing guide rings / flared mouths at both ends of the iron pipe to ensure smooth insertion and exit of the wire; operation per turn: starting the wire from the outer side of the left end - passing it through the tube core channel to the right end - returning axially to the left end along the outer wall - then passing it through to the right end to form a turn; positioning between turns: positioning marks can be affixed to the outer wall or shallow grooves / binding tape can be used to ensure that each turn is evenly distributed axially, reducing proximity effect and local overheating; fixing and potting: after winding, heat-resistant binding tape can be used for fixing, and varnishing / potting can be applied to key areas to improve mechanical strength and insulation reliability; lead wires and interfaces: reserve sufficient length of lead wires, and use crimp terminals or bolt terminals to connect the power supply to avoid contact resistance heating under high current.

[0063] In a further embodiment of the present invention, the control strategy and operating mode are as follows: Control objective:

[0064] Temperature control: based on outlet water temperature T out For feedback, adjust the coil current or duty cycle;

[0065] Constant power control: targets input power and is suitable for rapid heating;

[0066] Protection mode: Reduced rating or shutdown after detection of over-temperature, current interruption, short circuit, or open circuit.

[0067] In a further embodiment of the present invention, multiple temperature sensors 13 are used for monitoring, and the measurement points specifically include: water inlet / outlet temperature (at least one outlet temperature for closed loop), winding hot spot temperature (near the end bend and wire harness), iron pipe surface temperature (monitoring core overheating), and current / voltage sampling (for power estimation and protection).

[0068] In a further embodiment of the present invention, a section of hollow cylindrical iron pipe (hereinafter referred to as "iron pipe magnetic flux tube / magnetic core tube") is used as the magnetic circuit and magnetic flux constraint element, and an excitation winding is arranged on its outer surface. By applying an alternating current to the winding, an alternating magnetic field is established near the iron pipe and its inner cavity, thereby generating losses (mainly eddy current losses and / or hysteresis losses) in the coaxially arranged metal pipe (iron pipe or copper pipe). The metal pipe heats up and transfers the heat to the water flow inside the pipe, realizing non-contact heating through multi-physical coupling of electromagnetism, heat and fluid.

[0069] In a further embodiment of the present invention, a "through-the-core winding" is employed, wherein each turn of the through-the-core winding consists of two conductor segments: one segment passes through the tube core axially, and the other segment returns along the outer wall of the tube axially, forming a closed loop. The present invention improves electromagnetic coupling efficiency and reduces electrical losses (especially winding copper losses and ineffective leakage flux losses) while achieving the same heating effect.

[0070] In a further embodiment of the present invention, electromagnetic excitation and magnetic field establishment are achieved by applying an alternating current i(t) = I to the winding. pk • sin(ωt). Under low-frequency conditions, a quasi-static approximation can be used; at mid-to-high frequencies (kHz level), skin effect, proximity effect, and eddy currents need to be considered. Iron tubes have high permeability and high resistivity, making them suitable as "magnetic flux confinement / magnetic flux concentration" media: they can establish high magnetic flux density at relatively small ampere-turns (NI) and suppress their own eddy current losses.

[0071] The fundamental relationships of magnetic fields can be given by Ampere's circuital law and magnetic circuit models:

[0072] ∮H·dl = NI; B = μ0·μr·H; Φ = ∫B·dA; L ≈ N² / ℜ;

[0073] Where ℜ represents reluctance. When the magnetic circuit is more "closed" and the reluctance is smaller, the inductance L is larger, and the excitation current is smaller at the same voltage / frequency.

[0074] In a further embodiment of the present invention, the heating mechanism of the metal tube is as follows: the heat sources of the built-in metal tube mainly include:

[0075] Eddy current loss: An alternating magnetic field induces eddy currents inside a conductor, generating Joule heating, P eddy =∫(J² / σ) dV. The higher the frequency and the faster the magnetic flux changes, the more significant the eddy current loss; at the same time, the skin effect will cause the current to concentrate on the surface layer, affecting the equivalent resistance and heat distribution.

[0076] Hysteresis loss (significant only for ferromagnetic pipes / ferromagnetic materials): The alternating magnetic field drives the domain flipping, resulting in loss, which can be approximated by the Steinmetz form P. hys ≈ k·f·B α • V. The effect on copper pipes is negligible.

[0077] Additional losses include end effects, local eddy current enhancement caused by non-uniform magnetic fields, and field distortion caused by assembly eccentricity.

[0078] In a further embodiment of the present invention, heat transfer and water temperature rise: the volumetric heat source q''' generated by the metal pipe transfers heat to the water flow through: ① heat conduction through the metal pipe wall; ② metal-water convection heat transfer; ③ heat dissipation from the outer surface to the environment (an insulation layer can be designed to reduce heat dissipation). The water temperature rise approximately satisfies the law of conservation of energy.

[0079] P to water ≈ṁ·c p ·ΔT

[0080] Where ṁ represents mass flow rate, and c pLet ΔT be the specific heat capacity and ΔT be the inlet and outlet temperature difference. The system efficiency can be defined as η = P to water / P in .

[0081] In a further embodiment of the invention, a through-hole winding is employed, wherein the current path comprises: one section passing axially within the core channel, and another section returning axially along the outer wall. Each turn is like "passing the wire through the core once and then winding it back," which is topologically similar to a toroidal through-hole winding.

[0082] In this invention, the current enclosed by the Ampere loop causes the magnetic field H to be mainly distributed along the circumferential direction (circumferential magnetization), and the magnetic flux forms a closed magnetic circuit along the circumference within the thickness of the iron pipe wall, which significantly reduces magnetic resistance and leakage flux.

[0083] In this invention, the equivalent inductance L of the winding is increased, and the magnetic field is more confined to the vicinity of the iron pipe and the inner cavity; the external dissipated magnetic field is reduced, and the electromagnetic energy is more "focused" in the effective area.

[0084] In this invention, from the power supply side, the main electrical power consumed by the winding includes: copper loss P cu =I rms ²·R ac (Including DC resistance and AC additional resistance) and core loss P core The ineffective magnetic energy caused by leakage flux will be converted into additional excitation current demand, ultimately resulting in higher I. rms and higher P cu The through-hole winding reduces magnetic reluctance and leakage flux, and improves mutual coupling and flux utilization, thus enabling:

[0085] Under the same heating target (same heating power of the metal tube), the required excitation current is smaller, P cu Significantly reduced;

[0086] The reduction in external leakage flux reduces eddy current losses and electromagnetic interference (EMI) on the surrounding metal structure.

[0087] The magnetic flux is more controlled, and the heating is more uniform (requires a combination of winding distribution and end compensation design).

[0088] Input power P in Line current I rms Power factor PF (if AC grid power supply) or DC bus power (if inverter power supply); winding copper loss P cu (Including AC resistance), core loss P core Built-in metal tube loss P tube (Effective heating source); water temperature rise ΔT, time required to reach steady-state temperature rise (transient thermal response); spatial leakage magnetic field B leak(e.g., the maximum value at 10 cm from the outer surface) is used to assess EMI and safety; overall system efficiency η and energy consumption per unit temperature rise (kWh / m³·℃).

[0089] In this invention, considering the winding conductors and insulation, Litz wire or multi-strand parallel winding is preferred to reduce high-frequency copper losses; reliable insulation (temperature and moisture resistant) is required between the iron pipe surface and the conductors, and impregnation / potting is used to improve reliability. The iron pipe exhibits a saturation magnetic flux density B. sat If the operating point is close to saturation, the inductance decreases and the excitation current increases sharply, which will cause copper loss to rise and the magnetic core to overheat.

[0090] In this invention, the inductance of a through-hole winding can be approximated using a toroidal magnetic circuit:

[0091] L≈μ0·μr·N²·A f / l m

[0092] Substituting μr=2000, N=10, A f ≈0.0035 m², l m ≈0.346 m, so L≈2.51 mH (for order of magnitude reference only).

[0093] If a sinusoidal voltage V is applied to the power supply rms In an ideal inductor model that neglects resistance and losses, the excitation current I m ≈V rms / (ωL). Therefore, increasing L will directly decrease I. m This reduces winding copper loss.

[0094] In this invention, the heating method is electromagnetic induction heating (the built-in metal heat exchange tube is the heated body, and water flows inside the tube to carry away the heat); the magnetic core is formed by an iron tube magnetic flux tube (hollow cylinder) + external / internal axial winding conductor to form a "coaxial circuit", and the main magnetic flux is closed inside the magnetic core; the nominal effective heating length is 1000mm (excluding end protection / end cap structure); the number of winding turns (standard) is 10 turns (expandable to 6-14 turns, depending on the power supply voltage, current and target power); the conductor is selected from high frequency resistant stranded wire (Litz) or flexible copper stranded wire; flat copper strip / hollow copper tube can also be used (requires reinforced fixing and insulation); the iron tube adopts a "segmented set + heat insulation protective sleeve overall compression" structure to avoid the processing and transportation risks of a 1m single iron tube.

[0095] In this invention, the total length L total Approximately 1080mm (including end caps and connector area; effective core length 1000mm); maximum outer diameter D of the assembly totalApproximately 160mm (including outer winding carrier / shroud); outer diameter D of the internal heat pipe. tube The pipe diameter is 76mm (the recommended standard pipe diameter for easy procurement; 60 / 89mm specifications are also available); the water interface uses DN20-DN25 quick-connect or threaded connectors at both ends (select according to flow rate); electrical connection is used, specifically one copper terminal at each end (double-ended wiring); a "same-ended wiring" structure is also available.

[0096] In this invention, the iron tube magnetic core 1 is divided into 5 iron tube magnetic core segments 1a and 4 insulating gaskets 1b. The 5 iron tube magnetic core segments 1a are assembled into a 1000 mm section; the end face flatness is <= 0.05 mm; the chamfer is 0.5 × 45°; there are 4 inter-segment insulating gaskets 1b, made of polyimide / mica paper / thin glass fiber, used to suppress inter-segment wear and stress concentration; the inner diameter of the heat insulation protective sleeve 9 (GFRP / FRP) has a radial assembly gap of 0.5 mm; the outer surface can be used to attach the winding carrier; there are two end clamping rings, located at both ends of the iron tube magnetic core 1, between the iron tube magnetic core 1 and the end cap 5; the material is aluminum alloy or stainless steel, which, together with the pull rod, clamps the magnetic core segment; the material of the end cap 5 (non-magnetic) is aluminum alloy / stainless steel 304 / FR4; it includes a wire hole and a water pipe connector mounting position; the pull rods are evenly distributed around the circumference; the ends are protected with spring washers to prevent loosening; and an axial preload is provided (2-4 kN recommended). (Overall preload); the positioning key / anti-rotation key prevents rotation between the end cover and the sheath, preventing the winding / shroud from rotating.

[0097] The heat exchange tube serves as both a water channel and a "heated body" subjected to induction heating. It is made of ferromagnetic stainless steel (such as 430) or low-carbon steel (with anti-corrosion surface treatment). The length of the heat exchange tube is consistent with the effective core length. The outer diameter (OD) of the heat exchange tube is selected according to standard specifications for easy procurement; a larger outer diameter results in a larger heat exchange area but occupies more internal space. The inner diameter (ID) of the heat exchange tube has a wall thickness of 3-5 mm, balancing strength and thermal resistance. The end joint area is used for welding / threaded joints and sealing.

[0098] In this invention, each turn consists of two "axial conductors": the inner cavity axial conductor segment: located in the annular space between the inner diameter of the iron pipe and the outer diameter of the heat exchange tube, running axially from the left end to the right end; the outer wall axial return segment: located outside the outer diameter of the iron pipe (outside the sheath), running axially from the right end back to the left end; the two ends achieve reversal through the wire holes at the end caps, thereby forming a closed loop.

[0099] In this invention, the outer surface of the inner conductor guide sleeve (PEEK / FR4) is machined with 10 axial guide grooves; the clearance between the inner diameter and the magnetic core is 0.5 mm; the inner guide grooves are evenly distributed at 36°; they are used to place conductors with a diameter of 8 mm (including insulation); the heat insulation / insulation pad is selected by adding a heat insulation pad between the conductor and the heat exchange tube to prevent wear and electrical breakdown.

[0100] In this invention, the outer winding carrier is installed on the outside of the heat insulation protective sleeve; 10 axial guide grooves are machined on the outer surface; the outer guide grooves are used to place the return conductor; and it can be covered with heat-resistant binding tape + impregnated epoxy for fixation.

[0101] In this invention, the equivalent cross-sectional area of ​​the Litz line is 25-35 mm. 2 (Or flexible copper stranded wire) to reduce skin and proximity effects at high frequencies; 8×3 mm flat copper strip can also be used (requires good fixing); insulation class is temperature resistant 180-200℃ (H class), and the end through hole needs to be fitted with an insulating sleeve; conductor outer diameter (including insulation) is about 8 mm, which fits with a 9 mm guide groove, leaving a 0.5 mm installation allowance; number of turns is 10, which can be adjusted according to the power supply / target power.

[0102] In this invention, the outgoing wires can be either double-ended or single-ended. Double-ended outgoing wires have the starting end on the left and the ending end on the right, which facilitates the formation of a symmetrical magnetic field and reduces the skin effect at the ends. Single-ended outgoing wires add a "return lead channel" on the right to lead the ending wire back to the left terminal block, which facilitates power supply wiring and maintenance.

[0103] In this invention, the flatness of the end face of the iron pipe section is <= 0.05 mm to reduce the air gap and local stress between sections; the iron pipe ID and the guide sleeve OD are fitted with a radial gap of 0.3-0.6 mm to ensure assembly without loosening; the heat insulation protective sleeve ID is fitted with the iron pipe OD with a radial gap of 0.3-0.8 mm to avoid assembly jamming and allow for the use of adhesive layers / gaskets; the end wire passage hole has a chamfer of 0.5×45° to prevent scratching the conductor insulation; the impregnation and curing uses epoxy potting / impregnation (temperature resistance >= 150℃) to fix the winding, suppress vibration and noise, and improve the withstand voltage.

[0104] In this invention, the assembly steps are as follows:

[0105] 1) Preparation: Check the dimensions and flatness of the iron pipe sections; attach inter-section insulating gaskets to the end faces of the sections.

[0106] 2) Set: Insert the 5 sections of iron pipe into the heat insulation protective sleeve in sequence, and install the compression ring at the end.

[0107] 3) Inner parts: Insert the inner conductor guide groove sleeve into the inner diameter of the iron pipe; then insert the heat exchange tube into the inner diameter of the sleeve and adjust the concentricity.

[0108] 4) Winding: Arrange the axial conductor segments in the inner cavity in sequence according to the guide slot numbers 1-10; reverse the direction at the right end through the end cover and wire hole; arrange the return conductor segment in the guide slot of the outer winding carrier and return to the left end.

[0109] 5) Electrical connection: Install terminal block, crimp / weld conductor ends to ensure low contact resistance and stress relief.

[0110] 6) Tightening: Install the end cap and pull rod, and tighten them evenly to the recommended pre-tightening force; check that there are no obvious gaps in the iron pipe section.

[0111] 7) Curing: Epoxy impregnation / potting is performed on the windings and guide slots (avoiding the bare copper contact surfaces of the terminals) to complete insulation and fixation.

[0112] 8) Tests: Perform withstand voltage test (1-2kV recommended, depending on the power supply level), water withstand voltage test, and no-load / load temperature rise test.

[0113] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A magnetic flux tube through-hole type water heating device, characterized in that, include: The iron tube magnetic core (1), the metal heat exchange tube (2), the through-wound winding and the end cap (5) are provided. The iron tube magnetic core (1) is a hollow cylindrical structure. Both ends of the iron tube magnetic core (1) are equipped with end caps (5). The metal heat exchange tube (2) is located inside the iron tube magnetic core (1) and is coaxial with the iron tube magnetic core (1). The metal heat exchange tube (2) is provided with a water flow channel. The end cap (5) is provided with a wire hole (5a) for the through-wound winding to pass through. The through-wound winding includes: an inner cavity axial conductor section (3) and an outer wall axial return section (4). The multi-turn conductor of the inner cavity axial conductor section (3) adopts a through-wound winding structure and is located between the metal heat exchange tube (2) and the iron tube magnetic core (1). The multi-turn conductor of the outer wall axial return section (4) adopts a through-wound winding structure and is located outside the iron tube magnetic core (1). The two ends of the through-wound winding are respectively connected to two terminals (8).

2. The magnetic flux tube through-hole revolving water heating device according to claim 1, characterized in that, The iron tube magnetic core (1) includes: an iron tube magnetic core segment (1a) and an insulating gasket (1b). Multiple iron tube magnetic core segments (1a) are arranged along the axial direction, and an insulating gasket (1b) is provided between any two adjacent iron tube magnetic core segments (1a). The metal heat exchange tube (2) is made of ferromagnetic metal material.

3. The magnetic flux tube through-hole revolving water heating device according to claim 2, characterized in that, It also includes: a heat insulation protective sleeve (9), which is fitted on the outer surface of the iron pipe magnetic core (1). The heat insulation protective sleeve (9) is used to axially pre-tighten and fix multiple iron pipe magnetic core segments (1a) and multiple insulating pads (1b).

4. The magnetic flux tube through-hole revolving water heating device according to claim 3, characterized in that, Also includes: The outer winding carrier (11) is fitted on the outer surface of the heat insulation protective sleeve (9). The outer surface of the outer winding carrier (11) is provided with multiple axially extending outer guide grooves. The outer wall axial return line segment (4) is wound on the outer winding carrier (11) in a through-wound winding manner.

5. The magnetic flux tube through-hole revolving water heating device according to claim 1, characterized in that, Also includes: The inner conductor guide sleeve (10) is located inside the iron pipe magnetic core (1) and is coaxial with the iron pipe magnetic core (1). The outer surface of the inner conductor guide sleeve (10) is provided with multiple inner guide grooves extending along the axial direction. The inner cavity axial conductor section (3) is wound on the inner conductor guide sleeve (10) by a through-wound winding method. The metal heat exchange tube (2) is located inside the inner conductor guide sleeve (10).

6. The magnetic flux tube through-hole revolving water heating device according to claim 1, characterized in that, The inner wall of the through hole (5a) is provided with an insulating sleeve, which is used to pass through the through-hole rewinding.

7. The magnetic flux tube through-hole revolving water heating device according to claim 1, characterized in that, It also includes: an inlet connector (6) and an outlet connector (7). The two end caps (5) are respectively equipped with an inlet connector (6) and an outlet connector (7), which are connected to both ends of the metal heat exchange tube (2).

8. The magnetic flux tube through-hole revolving water heating device according to claim 1, characterized in that, The through-wound winding is made of stranded wire or Litz wire.

9. The magnetic flux tube through-hole revolving water heating device according to claim 8, characterized in that, The axial conductor segment (3) in the inner cavity and the axial loop segment (4) in the outer wall have opposite winding directions, and the axial conductor segment (3) in the inner cavity and the axial loop segment (4) in the outer wall are arranged symmetrically in the circumferential direction.

Images