Helium magnetocaloric phase change circulating power device

Abstract

The invention discloses a helium magnetocaloric phase change circulation power device which comprises a liquid helium tank, a plunger pump, a helium compressor, a heat exchange tank, a first surge tank, a countercurrent heat exchanger, a second surge tank and a turbo expander. Liquid helium and gas helium are stored in the liquid helium tank; the plunger pump is used for pressurizing liquid helium in the liquid helium tank to set pressure; the heat exchange tank internally comprises a magnetocaloric working medium, a rotating magnetic field, a cold source helium heat exchange pipeline and a heat source helium heat exchange pipeline, and the magnetocaloric working medium based on the magnetocaloric inverse heat effect is used as a medium, so that a heat source and cold and heat source helium are subjected to inverse heat exchange; the first surge tank and the second surge tank are used for stabilizing the inlet and outlet air pressure of the expansion machine so as to stabilize the working efficiency of the expansion machine; the countercurrent heat exchanger is used for carrying out heat exchange on high-pressure helium output by the first surge tank and a heat exchange medium for absorbing environmental heat energy; the expansion machine is used for converting heat energy of gas into mechanical energy and then converting the mechanical energy into electric energy through the generator, and recycling of environment low-temperature heat energy is achieved.

Description

Technical Field

[0001] The present invention relates to the field of low-temperature thermal energy recycling, and in particular to a helium magnetothermal phase change cycle power device. Background Art

[0002] Current technologies for converting ambient thermal energy into mechanical or electrical energy primarily focus on thermoelectric generation, thermoacoustic generation, heat-driven mechanical structures, thermodeformable materials, and magnetocaloric effects. These technologies generally rely on limited temperature differences or fluctuations in the environment, and in practical applications, they suffer from low conversion efficiency, limited power output, and poor system stability.

[0003] Among them, although thermoelectric power generation technology can work under small temperature differences, it is limited by the performance of thermoelectric materials (such as ZT value), making it difficult to achieve efficient energy conversion; thermoacoustic power generation and thermal deformation drive devices are generally suitable for micro-power consumption scenarios, but are limited by thermal coupling efficiency and mechanical energy output capacity, making it difficult to build a continuous and stable energy circulation system; and technologies based on the magnetocaloric effect are still mostly in the theoretical and experimental stages, especially in the low temperature difference range of ambient temperature, where the ΔT of magnetocaloric materials is relatively stable. a d is limited, and it is difficult to achieve a complete energy cycle alone.

[0004] Existing technologies are generally unable to directly convert thermal energy in low-temperature areas (such as ambient thermal energy) into mechanical energy and achieve sustainable cyclic operation without the need for external high-temperature heat sources or electrical energy assistance. Therefore, there is still a lack of an efficient mechanical energy output system with a self-closing structure, self-sustaining energy, and driven solely by a low-temperature heat source. Summary of the Invention

[0005] In response to the above-mentioned problems existing in the prior art, the present invention provides a helium magnetothermal phase change cycle power device, which solves the shortcomings of the prior art and has sufficient theoretical basis and feasibility of practical implementation.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A helium magnetothermal phase change cycle power device, comprising a liquid helium tank, a plunger pump, a helium compressor, a heat exchange tank, a first pressure stabilizing tank, a countercurrent heat exchanger, a second pressure stabilizing tank and a turbine expander;

[0008] The liquid helium tank is a sealed Dewar flask with normal pressure inside, storing pure liquid helium and gaseous helium that circulates in and out;

[0009] The plunger pump is used to pressurize the liquid helium output from the liquid helium tank to a set pressure, and the outside of the pump body and the connecting pipeline are insulated;

[0010] The heat exchange tank body is a sealed Dewar flask structure to isolate the influence of external heat sources. The interior includes a magnetocaloric working medium, a rotating magnetic source, a cold source helium heat exchange pipeline, and a hot source helium heat exchange pipeline. The magnetocaloric working medium based on the magnetocaloric effect is used as a medium to enable reverse heat exchange between the heat source and the cold and hot source helium.

[0011] The first and second pressure stabilizing tanks are used to stabilize the inlet and outlet pressures of the expander to stabilize the work efficiency of the expander. The exterior of the pressure stabilizing tanks and the connecting pipes are insulated.

[0012] The countercurrent heat exchanger is used to exchange heat between the high-pressure helium output from the first pressure-surge tank and the heat exchange medium that absorbs environmental heat energy;

[0013] The expander is used to convert the thermal energy of the helium into mechanical energy, which is then converted into electrical energy through a generator.

[0014] Furthermore, the heat exchange tank includes a hollow rotating drum, and the outside of the rotating drum is sequentially covered with a magnetic thermal working medium cylindrical shell and a gear ring. The magnetic thermal working medium cylindrical shell is equally divided into several long strip composite material pipelines with arc-shaped trapezoidal cross-sections. As the heat source helium heat exchange pipeline, the composite material needs to be able to withstand the liquid helium temperature and a certain internal pressure; a number of cold source helium heat exchange pipelines are evenly spaced in the forward direction in each pipeline. The pipeline has high thermal conductivity and can withstand the low temperature and internal high pressure of liquid helium. The interior of the cold and hot source helium heat exchange pipelines are filled with magnetic thermal working medium. When the magnetic thermal working medium is metal-based microparticles, the surface of the particles needs to be covered with a high thermal conductivity insulating coating. The gaps between the magnetic thermal working medium microparticles constitute the cold source and hot source helium heat exchange channels.

[0015] Furthermore, an internal magnetic source is fixed to the outer wall of the hollow drum, an external magnetic source is fixed to the inner wall of the gear ring, and the magnetocaloric working medium cylindrical shell is fixed between the inner and outer magnetic sources. The inner and outer magnetic sources maintain a certain rotational gap with the magnetocaloric working medium cylindrical shell, and the driving gear that drives the gear ring to rotate and the magnetocaloric working medium cylindrical shell are fixed to a fixed bracket inside the heat exchange tank;

[0016] The external magnetic source and the internal magnetic source are permanent magnets or superconducting coils. The number of internal and external magnetic sources is equal, and they rotate synchronously with opposite poles. The number of magnetic sources, the spacing between them, and the rotation speed are set according to the magnetocaloric properties of the overall magnetocaloric working fluid, the temperature change value after helium heat exchange, or the final liquefaction rate of the heat source helium.

[0017] Furthermore, when the external magnetic source and the internal magnetic source are superconducting coils, a coil heat exchange channel is provided between the superconducting coil wires, and the outer surface of the superconducting coil needs to be covered with an infrared reflective film with high reflectivity.

[0018] Furthermore, it also includes a first motor and a second motor, the first motor is used to drive the hollow drum to rotate, and the second motor is used to drive the ring gear to rotate. During the rotation and change of the magnetic field, the internal magnetic source and the external magnetic source correspond synchronously.

[0019] Furthermore, liquid helium is stored at the bottom of the liquid helium tank, and gas helium is above the liquid helium. A first pipeline is opened on the tank wall corresponding to the liquid helium. After the first pipeline is connected to the plunger pump, it is divided into several first branches, and the number of the first branches is equal to the number of the long strip composite material pipelines; several cold source helium heat exchange pipelines in each long strip composite material pipeline converge into a second branch at the bottom, and the several first branches are correspondingly connected to the several second branches; each first branch is provided with a first valve; second and third pipelines are opened on the tank wall corresponding to the gas helium, and after the second pipeline is connected to the gas valve A, it is divided into several branches and connected to the bottom end of the hot source helium heat exchange pipeline of the heat exchange tank; after the third pipeline is connected to the helium compressor, it is divided into several branches and connected to the bottom end of the coil heat exchange channel of the heat exchange tank, and the top end of the coil heat exchange channel is connected to the top end of the heat source heat exchange channel.

[0020] Furthermore, multiple cold source helium heat exchange pipelines converge into one channel from the top and are connected to the inlet of the first surge tank through the gas valve B;

[0021] The countercurrent heat exchanger includes a fourth pipeline and a fifth pipeline for exchanging heat with each other, one end of the fourth pipeline is connected to the outlet of the first pressure-surge tank, and the other end is connected to the expander, and both ends of the fifth pipeline are connected to the heat exchange medium that absorbs heat energy from the ambient heat source;

[0022] The expander is connected to the inlet of the second pressure stabilizing tank, and the outlet of the second pressure stabilizing tank is connected to the tail gas pipeline of the pressure stabilizing tank. After entering the heat exchange tank, the tail gas pipeline of the pressure stabilizing tank is divided into multiple branches and connected to the top of the heat source helium heat exchange pipeline. A second valve is provided on each branch.

[0023] Furthermore, the expander is connected to a generator, and part of the electricity generated by the generator is used to power the program control system, motor, helium compressor, plunger pump and gas valve of the device.

[0024] The beneficial technical effects brought about by the present invention are:

[0025] The present invention provides a helium magnetocaloric phase change cycle power device, which realizes the recycling of ambient low-temperature thermal energy. The temperature range includes the low temperatures of the North and South Poles and the high temperatures of the equator. The ambient low-temperature thermal energy can be converted into high-level mechanical energy and electrical energy, reducing dependence on fossil fuels. It does not produce greenhouse gases such as carbon dioxide. The device is simple to maintain and has low long-term operating costs.

[0026] By utilizing the characteristics of helium and the principle of reverse heat exchange due to the magnetocaloric effect, and then using liquid helium as both a working fluid and a cold source, this device uses a magnetocaloric working fluid (MCM) to absorb the latent heat released when the gas helium is liquefied, and transfers this heat energy to the cold source helium, realizing the heat release and re-liquefaction cycle of the helium after work, and realizing a high-efficiency, low-heat-to-mechanical energy system with a self-closing structure, self-sustaining energy, and a low-temperature heat source as the sole drive. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic structural diagram of a helium magnetothermal phase change cycle power device in the present invention;

[0028] Figure 2 A top view of the heat exchange pipelines between the magnetocaloric medium, the magnetic source, and the cold and hot source helium in the heat exchange tank of the present invention;

[0029] Figure 3 Schematic diagram of material selection for magnetocaloric working fluid combination in an embodiment of the present invention;

[0030] Figure 4 Schematic diagram of single material selection for magnetocaloric working fluid in an embodiment of the present invention;

[0031] Figure 5 This is the helium constant pressure specific heat diagram in the present invention; DETAILED DESCRIPTION

[0032] The specific implementation of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0033] A helium magnetothermal phase change cycle power device, such as Figure 1 and Figure 2 As shown, it includes a liquid helium tank 1, a plunger pump 2, a helium compressor 3, a heat exchange tank 4, a first surge tank 5, a countercurrent heat exchanger 6, a second surge tank 7 and a turbine expander 8;

[0034] The latent heat of liquefaction of helium is extremely low, and its latent heat of liquefaction can only cause the temperature of the same mass of helium to rise by about 4K. This feature is extremely important, and helium has become the only gas that can be used in this device. At the same time, the liquefaction temperature of helium is extremely low. When the temperature of ultra-low temperature helium rises to ambient temperature at a constant volume, it can generate huge expansion pressure, and the heat energy can be converted into mechanical energy through an expander. Some currently known giant magnetocaloric effect materials (GMCE) can produce a large adiabatic temperature difference (ΔT) under the action of a certain changing magnetic field (AMF). a d) Its temperature span can cover the temperature difference after heat exchange between cold and hot sources in a certain temperature zone, and can also cover the temperature difference after the heat source helium is liquefied and the cold source helium absorbs the heat of the heat source helium liquefaction and warms up.

[0035] The liquid helium tank is a sealed Dewar flask with normal pressure inside, storing pure liquid helium and gaseous helium that circulates in and out;

[0036] The plunger pump is used to pressurize the liquid helium output from the liquid helium tank to the set pressure, and the outside of the pump body and the connecting pipeline are insulated;

[0037] The heat exchange tank is a sealed Dewar flask structure, isolating it from external heat sources. It houses a magnetocaloric working fluid, a rotating magnetic source, a cold source helium heat exchange pipeline, and a hot source helium heat exchange pipeline. Using the magnetocaloric working fluid, based on the magnetocaloric effect, reverse heat exchange occurs between the heat source and the cold and hot source helium. The heat exchange tank can be positioned at any angle, ensuring that the liquefied helium can flow normally into the liquid helium tank. The pressure within the tank is set based on the properties of the magnetic source and magnetocaloric materials, as well as the operating conditions. A vacuum state is optimal. If the pressure is not in a vacuum state, the cold and hot source transmission pipelines, the magnetic source, and the hot source magnetocaloric heat exchange pipelines must be insulated to reduce convective heat transfer within the tank.

[0038] The first and second pressure stabilizing tanks are used to stabilize the inlet and outlet pressures of the expander to stabilize the work efficiency of the expander. The outside of the pressure stabilizing tanks and the connecting pipes are insulated.

[0039] The countercurrent heat exchanger is used to exchange heat between the high-pressure helium output from the first pressure-surge tank and the heat exchange medium that absorbs environmental heat energy;

[0040] The expander is used to convert the thermal energy of helium into mechanical energy, which is then converted into electrical energy through a generator.

[0041] Specifically, the heat exchange tank includes a hollow rotating cylinder (shaft), the exterior of which is in turn sheathed with a magnetocaloric working medium cylindrical shell and a rotating gear ring. The magnetocaloric working medium cylindrical shell is divided into several long strips of composite material pipes with arc-shaped trapezoidal cross-sections. As the heat source helium heat exchange pipe, the composite material needs to be able to withstand the temperature of liquid helium and a certain internal pressure. The pipe is fixed between the internal and external magnetic fields, remains stationary, and a magnetic field rotation gap is reserved between the internal and external magnetic sources. When the heat exchange tank is in a high vacuum environment, the pipe must be able to withstand a certain internal pressure. When the environment is not vacuum, the magnetocaloric working medium and the superconducting coil are insulated.

[0042] Each long strip of composite material pipe is evenly spaced forwardly within a number of independent cold source helium heat exchange pipes. The heat exchange pipes are made of low-eddy current, high-thermal-conductivity composite materials that can withstand the low temperature and internal high pressure of liquid helium. The cold and hot source helium heat exchange pipes are filled with magnetocaloric working fluid. When the magnetocaloric working fluid is metal-based microparticles, the surface of the particles must be covered with a high-thermal-conductivity insulating coating to significantly suppress the eddy current effect caused by the rotating magnetic field. The gaps between the magnetocaloric working fluid microparticles constitute the cold source and hot source helium heat exchange channels. To meet the needs of multi-temperature zone magnetic refrigeration, magnetocaloric microparticles with different magnetocaloric response characteristics are filled in sections from top to bottom. There is a certain pressure and density difference between the cold and hot source helium, and the cross-sectional area of ​​the cold and hot source helium pipes must be reasonably allocated according to the heat exchange requirements. The cold and hot source piping system is equipped with a multi-branch confluence device on the outside to improve the overall heat exchange efficiency and pipe layout flexibility.

[0043] The Curie temperature (T ( C ) ), adiabatic temperature difference (△Ta d) and the change in specific heat capacity (RCP) can be optimized through composition control. In actual design, first select the appropriate magnetocaloric working fluid according to the target heat exchange temperature zone, and then determine the heat exchange temperature that can be achieved after the cold and hot sources pass through the magnetocaloric medium based on the magnetocaloric performance at different magnetic field intensities. In order to ensure the temperature span requirements of the heat exchange section, the effective temperature response range of the magnetocaloric working fluid must completely cover the temperature difference range of the cold and hot sources in this section. When dealing with heat exchange tasks under large temperature spans or low magnetic field intensities, two or more magnetocaloric working fluids with similar Curie temperatures can be mixed and filled after experimental verification, or filled in sequence. Alternatively, magnetocaloric working fluids with different Curie temperatures can be separately filled in the cold and hot source channels at the same section to construct a magnetocaloric heat exchange channel with gradient response capability.

[0044] The selection and filling quality of each section of magnetocaloric medium should be determined by combining the following key factors: the initial temperature of the cold and hot source helium, the target heat transfer and the expected temperature after heat transfer; the Curie temperature T of the magnetocaloric material. ( C ) , effective △T a d and unit mass RCP performance indicators, and accordingly make reasonable segmentation design and sequence arrangement. In order to further reduce the system radiation heat loss, the outer surface of the magnetocaloric working medium shell is covered with a high reflectivity infrared reflective film to reduce the impact of infrared radiation heat on the superconducting coil. In the embodiment of the present invention, the magnetocaloric working medium is selected from low temperature to high temperature. Figure 3 and Figure 4 As shown;

[0045] Specifically, an internal magnetic source is fixed on the outer wall of the hollow drum, an external magnetic source is fixed on the inner wall of the gear ring, and the cylindrical shell of the magnetocaloric working medium is fixed between the inner and outer magnetic sources. The inner and outer magnetic sources maintain a certain rotational gap with the cylindrical shell of the magnetocaloric working medium. The gear ring transmission wheel and the cylindrical shell of the magnetocaloric working medium are fixed on a fixed bracket inside the heat exchange tank, and the external magnetic source rotates with the gear ring. The type of magnetic source can be configured as a permanent magnet or a superconducting coil according to the performance requirements of the selected magnetocaloric working medium. The number of internal and external magnetic sources is equal, and they keep opposite poles facing each other and rotating synchronously. The number, spacing and rotation speed of the magnetic sources are set according to the magnetocaloric performance of the overall magnetocaloric working medium under different magnetic field changes, the temperature change value of helium after heat exchange or the final liquefaction rate of the heat source helium. The entire rotating magnetic field system is composed of internal and external magnetic sources, and the magnetocaloric working medium is arranged between the internal and external magnetic sources to form a magnetic flux change zone.

[0046] The device also includes a first motor and a second motor. The first motor drives the hollow drum, and the second motor drives the ring gear. During the magnetic field rotation and change, the internal and external magnetic sources rotate synchronously. During system operation, the internal and external magnetic sources are driven by the motors to rotate synchronously relative to each other, achieving periodic magnetization and demagnetization of the magnetocaloric working fluid to produce the desired magnetocaloric change. The motor position is also set based on the motor's power consumption and heat output. If the heat output is relatively low relative to the overall heat exchange capacity of the cold and heat sources, the motor can be placed inside the heat exchange tank to heat the helium after the coil heat exchange. Conversely, if the heat output is high, the motor can be placed outside the heat exchange tank, with power input via a non-metallic, high-strength, low-thermal-conductivity drive shaft to drive the magnetic source's rotation.

[0047] When the external and internal magnetic sources are superconducting coils, a coil heat exchange channel is installed between the superconducting coil wires. This channel is filled with low-temperature helium pressurized by a compressor to efficiently remove the heat generated by the superconducting coils during operation, ensuring that they maintain a stable superconducting state. This cooling helium remains in a gaseous state after the heat exchange and does not need to be liquefied.

[0048] Since the magnetocaloric working fluid is alternately exposed to strong and weak magnetic fields through the rotation of internal and external magnetic sources, realizing a dynamic demagnetization cycle, there is a problem of mutual interference in the spatial trajectory between the cold and hot source pipelines and the heat exchange channels of the superconducting coils. To resolve this structural conflict, the system adopts a composite rotating pipeline connection method inside the hollow drum, so that the helium in the inner superconducting coil heat exchange pipeline can achieve synchronous rotation and fluid continuity while maintaining sealing and thermal insulation. The outer superconducting coil heat exchange pipeline needs to be centered on the hollow drum, and a composite rotating pipeline is set up outside the hollow drum. The heat exchange convergence pipeline of the cold and hot source magnetocaloric working fluid is located in the middle of the inner and outer composite rotating pipelines, and there is no need to use a composite rotating pipeline.

[0049] The inner and outer magnetic sources have different poles, and the length, width, quantity and rotation speed of the equidistant magnetocaloric working fluid are set according to the circumferential length of each group of magnetocaloric working fluid, the magnetocaloric working fluid charging and demagnetization time, and the heat exchange effect of the cold and hot source helium through the magnetocaloric working fluid.

[0050] In addition, in order to further suppress the external heat load caused by infrared radiation, the outer surface of the superconducting coil needs to be covered with a high-reflectivity infrared reflective film to effectively reduce its absorption of infrared radiation heat from the internal environment of the insulation tank.

[0051] With the discovery of high-temperature superconducting materials and technological advancements, the heat exchange of the superconducting coils in the device can now be performed directly using the heat source helium. This requires the superconducting coils to maintain a stable superconducting temperature above the initial temperature range of the heat source helium. After exchanging heat with the coils, the heat source helium then enters the magnetocaloric fluid to complete the heat exchange with the cold source helium. Under this premise, the internal pressure of the heat exchange tank can be isobaric with that of the heat source helium. However, the magnetocaloric fluid housing, the heat and cold source transmission pipelines, and the magnetic source must be insulated to minimize heat exchange with the helium in the tank.

[0052] Specifically, liquid helium is stored at the bottom of the liquid helium tank, and gas helium is above the liquid helium. A first pipeline is opened in the tank wall corresponding to the liquid helium. After being connected to the plunger pump, the first pipeline is divided into several first branches, and the number of first branches is equal to the number of long composite material pipelines. Several cold source helium heat exchange pipelines in each long composite material pipeline converge at the bottom to form a second branch, and several first branches are correspondingly connected to several second branches. A first valve is provided on each first branch. Second and third pipelines are opened in the tank wall corresponding to the gas helium. After being connected to the gas valve A, the second pipeline is divided into several branches and connected to the bottom end of the heat source helium heat exchange pipeline of the heat exchange tank. The third pipeline is connected to the helium compressor and then divided into several branches and connected to the bottom end of the coil heat exchange channel of the heat exchange tank. The top end of the coil heat exchange channel is connected to the top end of the heat source heat exchange channel. The helium compressor is used to pressurize the helium and adjust the internal pressure of the liquid helium tank. The temperature inside the superconducting coil and the heat exchange tank is maintained through heat exchange in the pipelines.

[0053] Multiple cold source helium heat exchange pipelines converge into one channel from the top and are connected to the inlet of the first surge tank through valve B;

[0054] The countercurrent heat exchanger includes a fourth pipeline and a fifth pipeline for exchanging heat with each other. One end of the fourth pipeline is connected to the outlet of the first surge tank and the other end is connected to the expander. Both ends of the fifth pipeline are connected to the heat exchange medium, and the heat exchange medium absorbs heat energy from the external atmosphere or seawater.

[0055] The expander is connected to the inlet of the second pressure stabilizing tank, and the outlet of the second pressure stabilizing tank is connected to the tail gas pipeline of the pressure stabilizing tank. After entering the heat exchange tank, the tail gas pipeline of the pressure stabilizing tank is divided into multiple branches and connected to the top of the heat source helium heat exchange pipeline. A second valve is provided on each branch.

[0056] The expander is connected to a generator, and part of the electricity generated by the generator is used to power the device's program control system, motor, helium compressor, plunger pump and gas valve.

[0057] The control system is electrically connected to the expander, the generator, the first and second motors, the plurality of first gas valves and the second gas valves, the gas valve A, the gas valve B, the helium compressor, and the plunger pump.

[0058] The latent heat of liquefaction of helium is extremely low. After absorbing its latent heat of liquefaction, the temperature rise of the same mass of helium is only about 4K. At the same time, the liquefaction temperature of helium is extremely low. When the constant volume of ultra-low temperature helium is heated to ambient temperature, it can generate huge pressure potential energy, which can be converted into mechanical energy through an expander. It is known that some giant magnetocaloric effect materials (GMCE) can produce a large adiabatic temperature difference (ΔT) under a certain changing magnetic field (AMF). ad) Its temperature span covers the temperature difference between the heat source and the heat source after heat exchange within a certain temperature range, and also covers the temperature difference between the liquefaction of the heat source helium and the temperature increase of the cold source helium after absorbing the heat of liquefaction of the heat source helium. Utilizing this characteristic, the magnetocaloric medium (MCM) absorbs the latent heat released during the liquefaction of the helium and transfers this heat energy to the cold source helium, achieving the heat release and re-liquefaction of the helium after work is performed.

[0059] During the cycle, liquid helium absorbs heat during pressurization, causing it to heat up and expand, generating pressure that drives the expander to produce work. The exhaust gas after expansion and work acts as a high-temperature heat source, while the initial pressurized liquid helium acts as a low-temperature cooling source. Through the reverse heat exchange principle of the magnetocaloric effect (MCE), the two transfer heat step by step through the multi-stage magnetocaloric medium (MCM). This releases heat energy from the high-temperature exhaust gas, which is absorbed by the low-temperature cooling source helium, ultimately cooling the exhaust gas again and liquefying it.

[0060] By using magnetocaloric working fluid as the heat exchange medium, a phase change cycle of "liquid helium-gas helium-liquid helium" is formed, and the expander converts part of the thermal energy into mechanical energy, and then outputs electrical energy.

[0061] The specific working process of the device of the present invention is:

[0062] After the plunger pump pressurizes the liquid helium to the set pressure, it enters the heat exchange tank through the pipeline and is divided into several branches, the same number of branches as the cold source helium heat exchange pipeline. Each branch is controlled by the first gas valve, which opens in sequence according to the movement of the magnetic source. The high-pressure, low-temperature helium flows from bottom to top, and simultaneously exchanges heat in the opposite direction with the high-temperature exhaust helium flowing from top to bottom through the magnetic thermal medium.

[0063] The selection of the magnetocaloric fluid for each section is determined by the temperature range, temperature differential, and required heat exchange of the corresponding cold and hot sources within that section. After heat exchange is complete, all high-pressure cold source helium branches converge into one path, exit the heat exchanger, enter the first surge tank, and then enter the countercurrent heat exchanger to exchange heat with the heat exchange medium, which has absorbed ambient heat energy. After reaching the set temperature, the helium enters the expander to perform work, and the resulting exhaust enters the second surge tank.

[0064] The exhaust gas from the second surge tank returns to the heat exchange tank via a pipeline, becoming heat source helium. The pipeline is divided into a number of branches, each containing the same number of heat source helium heat exchange pipelines. A second gas valve sequentially controls the flow of exhaust gas into the heat source helium heat exchange pipeline, where it undergoes reverse heat exchange with the upstream cold source helium through the magnetocaloric working fluid. After the heat exchange is complete, the heat source helium is cooled and liquefied, ultimately entering the liquid helium tank for storage.

[0065] After gas-liquid separation in the liquid helium tank, the cryogenic helium is pressurized by a compressor to the same pressure as the exhaust gas and then re-enters the heat exchange tank, where it is divided into several branches corresponding to the number of superconducting coil cooling channels. The helium exchanges heat with the superconducting coils through the pipelines and is then further divided into branches equal to the number of magnetocaloric working medium heat exchange channels. Together with the heat source exhaust gas, it enters the magnetocaloric working medium heat exchange pipeline under the control of a gas valve, where it undergoes multiple stages of heat exchange and is further cooled or liquefied.

[0066] The following is a further explanation of the operation process of liquid helium in the device based on the data:

[0067] A plunger pump pressurizes the liquid helium and feeds it into the heat exchange tank. It then branches into multiple cold-source helium heat exchange pipelines, with valves controlling the opening and closing sequence and mass flow rate of each branch. The cold-source helium gradually absorbs heat and heats up during the magnetocaloric process. The heated helium gas converges into a single channel, passes through a surge tank, and then enters a countercurrent heat exchanger to exchange heat with an external heat source before entering an expander to perform work. The expanded exhaust gas returns to the heat exchange tank as the heat source helium gas, branching into the heat source helium heat exchange pipeline. Heat is released by the magnetocaloric working fluid during demagnetization and refrigeration, gradually liquefying from top to bottom before converging into a single channel to enter the liquid helium tank. The opening and closing of the cold and hot sources and the mass flow rate ratio are controlled by gas valves.

[0068] Liquid helium is pressurized to P = 3.0 MPa by a plunger pump. According to REFPROP software, the temperature is T = 6.1334 K and the specific enthalpy h = 19.6485 kJ / kg. Considering the plunger pump efficiency of 0.9, the corrected T = 6.68 K, h = 22 kJ / kg, and the compression work W ≈ 22 kJ / kg are obtained. The pressurized liquid helium (supercritical helium) is fed into the heat exchange tank via a pipeline. It is divided proportionally according to the number of heat exchange pipelines for the magnetocaloric working fluid cold source. Controlled by a multi-way first valve, it flows sequentially through the corresponding cold source helium heat exchange pipelines within the magnetocaloric working fluid. As the magnetocaloric working fluid releases heat, it absorbs heat from the magnetocaloric working fluid from bottom to top, gradually increasing in temperature. The liquid eventually converges at the top, exits the tank, enters the first surge tank, and then enters the countercurrent heat exchanger. After exchanging heat with the external heat source, it enters the expander to perform work.

[0069] Assume the external heat source temperature is 273K (0°C), the helium temperature after heat exchange is T = 250K, P = 3.0MPa, h = 1313kJ / kg, and the specific entropy s = 20kJ / (kg·K). Assume the final pressure after expansion is 0.11MPa. According to REFPROP calculations, under ideal conditions, T = 66.7K, h = 351.6kJ / kg. Considering the expander efficiency of 0.85, the actual T = 94.3K, h = 495kJ / kg, and the output power is approximately W = 818kJ / kg.

[0070] Knowing the initial state parameters of the cold source and the hot source, the heat released by the liquefaction of the hot source helium can be calculated, and the temperature that the cold source helium can reach through magnetocaloric reverse heat exchange can be evaluated accordingly. The initial temperature of the heat source helium is T = 94.3K, the specific enthalpy h = 495kJ / kg, the enthalpy value of liquid helium is about h = -0.0733kJ / kg, and the total heat release ΔH required for liquefaction is ≈ 496kJ / kg. The initial h of the cold source helium is 22kJ / kg, so the total enthalpy after absorbing this heat is 518kJ / kg, and the corresponding temperature calculated by REFPROP is T = 97.4K. The heat exchange temperature difference ΔT = 97.4–94.3 = 3.1K is obtained. Since the cold source needs to release the same amount of heat or drop the corresponding temperature difference, the effective adiabatic temperature difference ΔT of the magnetocaloric working fluid in this temperature range is a When d≥6.2K, complete reverse heat exchange can be achieved. The temperature range of this temperature zone is the heat source temperature T=91.2K and the cold source temperature T=97.4K.

[0071] Further consider the heat release of the final liquefaction stage of the heat source helium. Assume that the initial temperature of the heat source in the liquefaction stage is T = 4.3K, P = 0.1MPa, h = 21.4kJ / kg; the initial state of the cold source helium is P = 3.0MPa, T = 6.68K, h = 19.6485kJ / kg. The total heat exchange ΔH ≈ 21.4 + 19.65 = 41.15kJ / kg. After calculation by REFPROP, the corresponding cold source temperature after heat exchange can reach T = 10.8K, 10.8K-6.68K = 4.12K, and the temperature rise is about 4.2K. The effective adiabatic temperature difference of the corresponding magnetocaloric working fluid should be greater than 4.3K. Considering that the temperature of the heat source drops by only 0.1K during the liquefaction process, in order to maintain a sufficient temperature difference to drive heat exchange, the lowest temperature of the magnetocaloric working fluid needs to be lower than 4.2K, generally about 2K, and the corresponding terminal magnetocaloric working fluid needs to have an effective adiabatic temperature difference ΔT a d≥6.3K.

[0072] By comparing the specific enthalpy and temperature changes at both ends of the cold and hot sources, combined with the constant pressure specific heat curve of the cold and hot sources ( Figure 5 ), it can be determined that the temperature of the cold and hot source helium at the corresponding position and the effective adiabatic temperature difference of the corresponding magnetocaloric working fluid are ΔT a When d ≥ 6.3 K, the cold and hot sources can be adjusted to the set temperature through magnetic reverse heat transfer. However, this corresponding temperature range is too narrow, requiring too many magnetocaloric working fluid stages. Therefore, a giant magnetocaloric effect working fluid with a large temperature span is needed to reduce the number of stages to ensure heat exchange requirements. Figure 5 The data are from REFPROP software.

[0073] In order to ensure the final liquefaction rate of helium, the helium liquefaction section can adopt a two-stage magnetocaloric heat exchange, in which the second and last sections liquefy part of the gas helium, and the last section is used to complete the liquefaction of the set proportion of gas helium, so as to achieve full absorption of the liquefaction heat of the heat source helium by the cold source helium.

[0074] Figure 2As shown, when the magnetic field rotates from zone A to zone B, the magnetocaloric fluid in zone B is magnetized and releases heat, causing the temperature to rise. When the temperature reaches the set value or the magnetization time is set, the first valve of the cold source helium heat exchange pipeline between the internal and external magnetic sources is opened, and valve B is opened. The cold source helium flows from bottom to top through the magnetocaloric particles, exchanging heat with the magnetocaloric fluid in each temperature zone, causing the temperature to rise and the magnetocaloric fluid temperature to gradually decrease. When the temperature or time after heat exchange reaches the set value, valve B and the first valve are closed. At the same time, the magnetocaloric fluid in zone A begins to demagnetize and cool. After it drops to the set temperature or demagnetizes for a certain period of time, valve A is opened. At the same time, the second valve of the heat source helium heat exchange pipeline between the internal and external magnetic sources is opened. The heat source helium flows from top to bottom, exchanging heat with the magnetocaloric fluid step by step, completing the final heat exchange and proportional helium liquefaction. After the magnetocaloric fluid reaches the set temperature or the heat exchange reaches the set time, valve A and the second valve are closed. The next round of cold and hot source helium heat exchange cycle begins while the magnetic source rotates to magnetize and demagnetize the magnetocaloric fluid. In this process, as the rotating magnetic field sequentially magnetizes and demagnetizes the magnetocaloric fluid, the cold and hot source helium undergoes countercurrent heat exchange and liquefaction cycles through the magnetocaloric fluid.

[0075] After the heat source helium is liquefied, it flows into the storage tank to replenish the liquid level. The unliquefied cryogenic helium is pressurized by a compressor to the same pressure as the exhaust gas. It then enters the superconducting coil heat exchange channel within the heat exchange tank through a pipeline for heat exchange. It then absorbs heat energy from the magnetic source rotating motor and other heat energy before being merged into the exhaust gas mixing pipeline. Together with the heat source helium, it undergoes heat exchange and liquefaction through the magnetocaloric working fluid. The heat load within the vacuum chamber comes from heat conduction from the external environment, internal infrared radiation, and self-heating of the superconducting coils. This heat energy can be adjusted to maintain stable operation by controlling the heat and cold sources and the helium flow quality of the compressor.

[0076] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A helium magnetocaloric phase change cycle power device, characterized in that: It includes a liquid helium tank, a plunger pump, a helium compressor, a heat exchange tank, a first surge tank, a countercurrent heat exchanger, a second surge tank and a turbine expander; The liquid helium tank is a sealed Dewar flask with normal pressure inside, storing pure liquid helium and gaseous helium that circulates in and out; The plunger pump is used to pressurize the liquid helium output from the liquid helium tank to a set pressure, and the outside of the pump body and the connecting pipeline are insulated; The heat exchange tank body is a sealed Dewar flask structure to isolate the influence of external heat sources. The interior includes a magnetocaloric working medium, a rotating magnetic source, a cold source helium heat exchange pipeline, and a hot source helium heat exchange pipeline. The magnetocaloric working medium based on the magnetocaloric effect is used as a medium to enable reverse heat exchange between the heat source and the cold and hot source helium. The first and second pressure stabilizing tanks are used to stabilize the inlet and outlet pressures of the expander to stabilize the work efficiency of the expander. The exterior of the pressure stabilizing tanks and the connecting pipes are insulated. The countercurrent heat exchanger is used to exchange heat between the high-pressure helium output from the first pressure-surge tank and the heat exchange medium that absorbs environmental heat energy; The expander is used to convert the thermal energy of the helium into mechanical energy, which is then converted into electrical energy through a generator.

2. A helium magnetothermal phase change cycle power device according to claim 1, characterized in that: The heat exchange tank includes a hollow rotating drum, and a magnetic thermal working medium cylindrical shell and a gear ring are sequentially sleeved on the outside of the rotating drum. The magnetic thermal working medium cylindrical shell is equally divided into several long strip composite material pipelines with arc-shaped trapezoidal cross-sections. As the heat source helium heat exchange pipeline, the composite material needs to be able to withstand the liquid helium temperature and a certain internal pressure; a number of cold source helium heat exchange pipelines are evenly spaced in the forward direction in each pipeline. The pipeline has high thermal conductivity and can withstand the low temperature and internal high pressure of liquid helium. The interiors of the cold and hot source helium heat exchange pipelines are filled with magnetic thermal working medium. When the magnetic thermal working medium is metal-based microparticles, the surface of the particles needs to be covered with a high thermal conductivity insulating coating, and the gaps between the magnetic thermal working medium microparticles constitute cold source and hot source helium heat exchange channels.

3. A helium magnetothermal phase change cycle power device according to claim 2, characterized in that: The outer wall of the hollow drum is fixed with an internal magnetic source, the inner wall of the gear ring is fixed with an external magnetic source, the magnetocaloric working medium cylindrical shell is fixed between the inner and outer magnetic sources, and a certain rotational gap is maintained between the inner and outer magnetic sources and the magnetocaloric working medium cylindrical shell. The driving gear that drives the gear ring to rotate and the magnetocaloric working medium cylindrical shell are fixed to a fixed bracket inside the heat exchange tank; The external magnetic source and the internal magnetic source are permanent magnets or superconducting coils. The number of internal and external magnetic sources is equal, and they rotate synchronously with opposite poles. The number of magnetic sources, the spacing between them, and the rotation speed are set according to the magnetocaloric properties of the overall magnetocaloric working fluid, the temperature change value after helium heat exchange, or the final liquefaction rate of the heat source helium.

4. A helium magnetothermal phase change cycle power device according to claim 3, characterized in that: When the external magnetic source and the internal magnetic source are superconducting coils, a coil heat exchange channel is provided between the superconducting coil wires, and the outer surface of the superconducting coil needs to be covered with an infrared reflective film with high reflectivity.

5. The helium magnetothermal phase change cycle power device according to claim 4, characterized in that: It also includes a first motor and a second motor. The first motor is used to drive the hollow drum to rotate, and the second motor is used to drive the ring gear to rotate. During the rotation and change of the magnetic field, the internal magnetic source and the external magnetic source correspond synchronously.

6. The helium magnetothermal phase change cycle power device according to claim 5, characterized in that: Liquid helium is stored at the bottom of the liquid helium tank, and gas helium is above the liquid helium. A first pipeline is opened on the tank wall corresponding to the liquid helium. After the first pipeline is connected to the plunger pump, it is divided into a plurality of first branches. The number of the first branches is equal to the number of the long strip composite material pipelines. The bottom of a plurality of cold source helium heat exchange pipelines in each long strip composite material pipeline converges into a second branch. The plurality of first branches are correspondingly connected to the plurality of second branches. A first valve is provided on each first branch. A second and a third pipeline are opened on the tank wall corresponding to the gas helium. After the second pipeline is connected to the gas valve A, it is divided into a plurality of branches and connected to the bottom end of the heat source helium heat exchange pipeline of the heat exchange tank. After the third pipeline is connected to the helium compressor, it is divided into a plurality of branches and connected to the bottom end of the coil heat exchange channel of the heat exchange tank. The top end of the coil heat exchange channel is connected to the top end of the heat source heat exchange channel.

7. The helium magnetothermal phase change cycle power device according to claim 6, characterized in that: Multiple cold source helium heat exchange pipelines converge into one channel from the top and are connected to the inlet of the first surge tank through valve B; The countercurrent heat exchanger includes a fourth pipeline and a fifth pipeline for exchanging heat with each other, one end of the fourth pipeline is connected to the outlet of the first pressure-surge tank, and the other end is connected to the expander, and both ends of the fifth pipeline are connected to the heat exchange medium that absorbs heat energy from the ambient heat source; The expander is connected to the inlet of the second pressure stabilizing tank, and the outlet of the second pressure stabilizing tank is connected to the tail gas pipeline of the pressure stabilizing tank. After entering the heat exchange tank, the tail gas pipeline of the pressure stabilizing tank is divided into multiple branches and connected to the top of the heat source helium heat exchange pipeline. A second valve is provided on each branch.

8. The helium magnetothermal phase change cycle power device according to claim 7, characterized in that: The expander is connected to a generator, and part of the electricity generated by the generator is used to power the program control system, motor, helium compressor, plunger pump and gas valve of the device.

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