Self-adapting wide temperature range cascade heat utilization thermoelectric power generation system based on phase transition heat transport

Abstract

The present disclosure provides a self-adaptive wide temperature range step heat utilization thermoelectric power generation system based on phase change heat transport. In the system, the inlet pipeline, the fluid bundle and the outlet pipeline are connected in sequence to provide a flow channel for the wide temperature range fluid; the liquid storage tank is divided into multiple liquid storage spaces along the flow direction of the wide temperature range fluid, different liquid storage spaces are filled with phase change medium with different boiling points, the boiling point gradually decreases along the flow direction of the wide temperature range fluid, and step heat exchange is realized; the fluid bundle is inserted in the liquid storage tank and exchanges heat with the phase change medium to provide energy for the phase change of the phase change medium; the top of each liquid storage space is connected to a group of thermoelectric modules through a boiling flow pipeline, and the thermoelectric modules are connected back to the bottom of the liquid storage space through a cooling return pipeline to realize the circulation of the phase change medium in the liquid storage space and the thermoelectric modules; the cold plate of the thermoelectric module is further connected to a cooling assembly. The use of the present application can realize the heat utilization of the wide temperature range fluid, improve the uniformity of the temperature distribution of the thermoelectric module, and improve the thermoelectric power generation efficiency.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric power generation technology that combines wide-temperature-range fluid heat utilization, and specifically to an adaptive wide-temperature-range cascade heat utilization thermoelectric power generation system based on phase change heat transport. Background Technology

[0002] Thermoelectric power generation technology directly converts temperature differences into electrical energy through the thermoelectric effect, offering advantages such as high efficiency, environmental friendliness, and low maintenance costs. It is applicable to waste heat recovery, aerospace, automotive energy efficiency improvement, and power supply for portable devices. In industry, thermoelectric power generation can recover waste heat (such as from factories and power plants) and convert it into electricity, improving energy utilization efficiency. In the automotive sector, waste heat recovery improves fuel efficiency. Furthermore, thermoelectric power generation can be combined with other renewable energy sources such as solar energy to enhance overall system efficiency.

[0003] Phase change heat transfer (PCT) utilizes the latent heat absorbed or released by a substance during a phase change process to efficiently transfer heat, offering significant advantages. First, the temperature remains almost constant during the phase change, improving heat transfer efficiency and ensuring temperature stability, making it ideal for precise temperature control. Second, PCT materials can store large amounts of heat, with a heat storage density far exceeding that of sensible heat materials, making them widely used in thermal storage systems. Different PCT materials cover a low-to-high temperature range, suitable for various industrial applications. Furthermore, PCT can significantly reduce equipment size and cost, and possesses multiple functions such as heat dissipation, heat storage, and temperature control, making it widely used in electronic heat dissipation, building energy conservation, and industrial thermal management.

[0004] In the industrial sector, energy-intensive industries such as metallurgy, chemicals, and cement generate large amounts of high-temperature waste gas and waste liquid. In construction and municipal facilities, data centers, sewage treatment plants, and large kitchens produce high-temperature fluids containing significant amounts of waste heat. In the transportation sector, automobile, train, and ship engines emit large quantities of high-temperature exhaust gases. These fluids contain a significant amount of usable heat, but the heat carried by fluids produced by different processes varies. It is difficult to have a single system to recover and utilize the heat from these fluids with a wide temperature range. In other words, traditional thermoelectric generators suffer from poor temperature uniformity when dealing with fluids with a wide temperature range, which is detrimental to heat conversion and utilization. Summary of the Invention

[0005] In view of this, the present invention provides an adaptive wide-temperature-range cascade heat utilization thermoelectric power generation system based on phase change heat transport, which can realize the heat utilization of fluids in a wide temperature range, improve the uniformity of temperature distribution of thermoelectric modules, and improve the efficiency of thermoelectric power generation.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows.

[0007] An adaptive wide-temperature-range cascade thermal utilization thermoelectric power generation system based on phase change heat transport includes: an inlet pipe, an outlet pipe, a fluid tube bundle, a liquid storage tank, a boiling flow pipe, a thermoelectric module, a cooling return pipe, and a cooling component;

[0008] The inlet pipe, fluid tube bundle, and outlet pipe are connected in sequence to provide a flow channel for fluids over a wide temperature range;

[0009] The liquid storage tank is divided into multiple liquid storage spaces along the direction of fluid flow over a wide temperature range. Different liquid storage spaces are filled with phase change media with different boiling points. The boiling point gradually decreases along the direction of fluid flow over a wide temperature range, realizing stepped heat exchange. The fluid tube bundle is inserted in the liquid storage tank to exchange heat with the phase change media and provide energy for the phase change of the phase change media.

[0010] Each liquid storage space is connected to a set of thermoelectric modules at the top via a boiling flow pipe. The thermoelectric modules are connected back to the bottom of the liquid storage space via a cooling return pipe, realizing the circulation of the phase change medium in the liquid storage space and the thermoelectric modules. The cold plate of the thermoelectric module is further connected to a cooling component.

[0011] Preferably, each liquid storage space is provided with an upwardly contracting flared port at the top.

[0012] Preferably, the liquid storage tank includes a fluid tube bundle placed at the bottom, which is separated from the phase change medium storage space at the top by the tube bundle wall.

[0013] Preferably, the thermoelectric module includes a collector, thermoelectric elements, and a water-cooled plate; thermoelectric elements are attached to both ends of the collector to provide a heat source for the hot end of the thermoelectric elements; the cold end of each thermoelectric element is attached to the water-cooled plate for heat dissipation; the boiling flow pipe and the cooling return pipe are welded to the top and bottom of the collector, respectively, and the phase change medium condensed in the collector flows back to the storage tank by gravity through the cooling return pipe.

[0014] Preferably, the cold end of the thermoelectric element is attached to the water-cooled plate with thermally conductive adhesive, and the hot end is sandwiched between the thermoelectric element and the collector and then fastened together with bolts to form a sandwich structure.

[0015] Preferably, an inlet variable cross-section channel is connected between the inlet pipe and the inlet of the fluid tube bundle; an outlet variable cross-section channel is connected between the tail of the fluid tube bundle and the outlet pipe.

[0016] Preferably, the selection of thermoelectric elements in multiple thermoelectric modules is as follows: thermoelectric elements with different operating temperatures are selected along the fluid flow direction over a wide temperature range to adapt to the optimal operating temperature range.

[0017] Preferably, the liquid storage tank is divided into three parts by a partition along the direction of fluid flow over a wide temperature range, and is respectively filled with a high-temperature phase change medium, a medium-temperature phase change medium, and a low-temperature phase change medium.

[0018] Preferably, the high-temperature phase change medium is liquid metallic sodium; the medium-temperature phase change medium is heat-conducting oil; and the low-temperature phase change medium is cooling water.

[0019] Preferably, the mass of the phase change medium in the storage space and the external area of ​​the tube bundle are determined through matching calculations:

[0020] First, for each heat exchange-equipped liquid storage space i, the required heat flux density q is given. i The boiling heat transfer coefficient h can be calculated using formulas (I) and (II). i :

[0021]

[0022] In the formula, T i_in Let T be the temperature of the fluid entering storage space i; if storage space i is the first storage space where heat exchange occurs, then T... i_in Let T be the temperature of the fluid over a wide temperature range; if the storage space i is any storage space after the first storage space where heat exchange occurs, then T i_in For phase change medium b in the (i-1)th liquid storage space i-1 The boiling temperature, T i Phase change medium b in liquid storage space i i boiling temperature; r i The latent heat of vaporization of the phase change medium in the storage space i; c pli Pr is the specific heat capacity of the phase change medium. li ρ is the Prandtl number of the phase change medium. li ρ vi These are the liquid density and gas density of the phase change medium, respectively, η li Let σ be the dynamic viscosity of the phase change medium. i q represents the surface tension of the phase change medium. i The required heat flux density for the corresponding cavity; C wli Empirical coefficients for phase change media;

[0023] Given the mass flow rate of a wide-temperature-range fluid. Based on the boiling heat transfer coefficient h i Using relational expressions Determine the heat transfer Q between the phase change medium and the wide-temperature-range fluid in the storage space i. i , with the outer surface area A of the tube bundle i Relationship;

[0024] According to m i =Q i / r i and Q i With A i The relationship is obtained to obtain the phase change medium m in the liquid storage space i.i With A i Relationship;

[0025] Finally, according to m i With A i The relationship, through joint selection m i With A i Ensure that the volume of the phase change medium does not exceed the volume of the intermediate tube bundle.

[0026] Beneficial effects:

[0027] (1) The present invention uses intermediate phase change media with different temperature ranges to realize the cascade utilization of a wide temperature range fluid with a large temperature difference. When the low-temperature fluid part of the wide temperature range fluid passes through the phase change media in the high temperature range, the phase change media has not reached the boiling point and no phase change occurs. Only convective heat transfer occurs. The specific heat capacity of the phase change media is small, so the heat transfer is low. When the high-temperature fluid in the wide temperature range fluid enters, the phase change media reaches the boiling point and phase change heat transfer occurs. The medium transfers the heat of the fluid to the thermoelectric module, the fluid temperature decreases, and the cooled fluid then exchanges heat with the phase change media of the next temperature gradient, realizing the cascade heat transfer of the wide temperature range fluid.

[0028] (2) The liquid storage tank of this invention is connected to the thermoelectric module through a boiling flow pipe and a cooling circuit pipe forming a loop gravity heat pipe. It utilizes gravity and fluid phase change to achieve efficient heat transfer. After the phase change medium vaporizes, it rises to the boiling flow pipe and enters the thermoelectric module. After generating electricity using high heat, the condensed liquid phase change material flows back to the liquid storage tank under gravity through the cooling return pipe. The entire process is cyclical and requires no pumps or capillary structures; the system relies on gravity to drive the liquid return. This invention designs a tightly closed system, which facilitates rapid heat transfer from the hot end to the cold end, resulting in a fast heat exchange response and minimal impact on fluid flow over a wide temperature range. Simultaneously, the overall temperature uniformity is high during the transfer of the working fluid between the hot and cold ends, and the temperature at the hot end of the thermoelectric module is uniform, which helps improve the efficiency and output of thermoelectric power generation.

[0029] (3) In a preferred embodiment, each liquid storage space is provided with an upwardly contracting flared port at the top to facilitate gas discharge.

[0030] (4) In a preferred embodiment, an inlet variable cross-section channel connects the inlet pipe to the fluid bundle inlet, where a wide-temperature-range fluid with a certain initial velocity is buffered. As the fluid passes through the flared opening, the cross-sectional area of ​​the pipe increases, and according to the continuity equation, the fluid velocity decreases. This is because velocity and flow area are inversely proportional; the fluid must distribute the same flow rate across a larger cross-section. According to Bernoulli's equation, the decrease in velocity is accompanied by an increase in hydrostatic pressure; therefore, the flared opening typically leads to a pressure increase. The flared opening also avoids pressure loss due to abrupt contraction and reduces flow instability.

[0031] (5) In a preferred embodiment, thermoelectric elements with different operating temperatures are selected along the fluid flow direction over a wide temperature range to adapt to the optimal operating temperature range. Different thermoelectric elements are used for different temperature ranges primarily because the performance of thermoelectric materials varies significantly at different temperatures. At low temperatures, the material needs to have a high Seebeck coefficient and low thermal conductivity to improve the voltage output caused by the temperature difference. In the medium temperature range, the material needs to balance electrical and thermal conductivity to achieve a stable thermoelectric effect. At high temperatures, the material needs to have high-temperature stability and low thermal conductivity to reduce heat loss and improve efficiency. Temperature changes affect the Seebeck coefficient, electrical conductivity, and thermal conductivity of the material; therefore, selecting a suitable thermoelectric material can maximize the thermoelectric effect and improve energy conversion efficiency.

[0032] (6) Since the boiling point of the phase change medium with gradient setting can match the incoming fluid, different types of phase change materials have different thermodynamic properties. By using the boiling point, density, viscosity, surface tension and other properties of the phase change material as well as the required heat flux density, the boiling heat transfer coefficient between the phase change medium and the wide temperature range fluid can be calculated, thereby calculating the heat transfer between the phase change medium and the wide temperature range fluid, thus determining the required mass of the phase change medium and the outer surface area of ​​the tube bundle, and achieving matching.

[0033] (7) The device of the present invention has a simple structure, is flexible and convenient to use, has a low cost, a long service life, is easy to disassemble and install, and has strong applicability. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the adaptive wide-temperature-range cascade thermal utilization thermoelectric power generation system based on phase change heat transport according to the present invention.

[0035] Figure 2 This is a three-dimensional diagram of an adaptive wide-temperature-range cascade thermal utilization thermoelectric power generation system based on phase change heat transport in an embodiment of the present invention.

[0036] Figure 3 This is a cross-sectional view of an adaptive wide-temperature-range cascade thermal utilization thermoelectric power generation system based on phase change heat transport in an embodiment of the present invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] The present invention provides an adaptive wide-temperature-range cascade heat utilization thermoelectric power generation system based on phase change heat transport. The basic idea is as follows: Fluids generated from different production processes have a large temperature range variation. Traditional thermoelectric power generation devices will have a very poor temperature uniformity problem when facing wide-temperature-range fluids, which is not conducive to the conversion and utilization of heat. In the present invention, the liquid storage tank is filled with multiple phase change media, and the boiling points of the phase change media gradually decrease along the flow direction of the wide-temperature-range fluid. When the wide-temperature-range fluid passes through these phase change media in sequence, heat exchange occurs at the corresponding media respectively, and the low-temperature fluid with good temperature uniformity after heat exchange is discharged from the liquid storage tank along the pipeline, realizing gradient heat exchange.

[0039] Meanwhile, the present invention connects a thermoelectric module to the liquid storage tank. The high-temperature gaseous medium generated after the phase change medium boils enters the corresponding thermoelectric module for condensation heat exchange, playing a role in transporting heat from the wide-temperature-range fluid to the thermoelectric module, providing a heat source for the hot end of the thermoelectric chip, and the thermoelectric chip generates electric energy. The excess heat is dissipated from the cold end of the thermoelectric chip to the cooling component. The liquefied medium returns to the corresponding liquid storage tank along the return pipeline, realizing the reuse of the phase change medium.

[0040] Next, taking three cavities and three phase change media as an example, the stepped heat exchange principle of the present invention will be described.

[0041] Assume the temperature of the wide-temperature-range fluid is T in , the boiling points of the three phase change media are T1, T2, T3 (T1>T2>T3) respectively; the latent heats of vaporization are r1, r2, r3 respectively; the boiling heat transfer coefficients are h1, h2, h3 respectively; the mass flow rate of the fluid is The outer surface areas of the tube bundles in the cavities are A1, A2, A3 respectively; full heat exchange occurs in the cavities; considering that the specific heat capacity of the phase change medium is much smaller than its latent heat of vaporization, the heat exchange mode between the fluid and the medium only considers boiling heat transfer, and natural convection heat transfer is ignored.

[0042] When the wide-temperature-range fluid flows through the liquid storage tank, the temperature of the wide-temperature-range fluid can be divided into three intervals, and the temperatures of the wide-temperature-range fluid in these three intervals are set here. When T in >T1, define the temperature of the wide-temperature-range fluid as T h ; when T2<T in <T1, define the temperature of the wide-temperature-range fluid as T m ; when T3<T in <T2, define the temperature of the wide-temperature-range fluid as T l . Define the heat transfer amounts of the fluid in the three cavities along the flow direction as Q1, Q2, Q3 respectively;

[0043] Calculate the boiling heat transfer coefficients of the three fluids respectively:

[0044]

[0045] Among them, Pr li The Prandtl number and ρ of the phase change medium li ρ vi The liquid density and gas density of the phase change medium, respectively, η li The dynamic viscosity and σ of the phase change medium i For the surface tension of the phase change medium, q i To correspond to the required heat flux density of the cavity, C wli This is an empirical coefficient for phase change media.

[0046] Heat transfer calculations were performed for the three fluid temperatures respectively:

[0047] 1. When the fluid temperature is T h The heat exchange amounts Q1, Q2, and Q3 can be calculated using the following formulas:

[0048]

[0049]

[0050] The evaporation mass flow rates m1, m2, and m3 of the three media can be calculated using the following formulas:

[0051] m1 = Q1 / r1 (reaching boiling point, absorbing heat) (10)

[0052] m2=Q2 / r2 (11)

[0053] m3=Q3 / r3 (12)

[0054] 2. When the fluid temperature is T m Considering the small specific heat capacity of the phase change medium, the heat exchange Q1 is negligible. The heat exchange Q2 and Q3 can be calculated using the following formulas:

[0055]

[0056] The evaporation masses m1, m2, and m3 of the three media can be calculated using the following formula:

[0057] m1≈0 (15)

[0058] m2=Q2 / r2 (16)

[0059] m3=Q3 / r3 (17)

[0060] 3. When the fluid temperature is T l Considering the small specific heat capacity of the phase change medium, the heat exchange rates Q1 and Q2 are negligible. The heat exchange rate Q3 can be calculated using the following formula:

[0061]

[0062] The evaporation masses m1, m2, and m3 of the three media can be calculated using the following formula:

[0063] m1≈0 (19)

[0064] m2≈0 (20)

[0065] m3=Q3 / r3 (21)

[0066] In practical applications, multiple fluids can be selected as needed, not limited to three. This invention uses three fluids with different boiling points for demonstration and explanation. The principle diagram is shown below. Figure 1 Where (a) corresponds to the initial state of the three fluids, which is also the fluid temperature T. h The heat transfer process corresponding to time T; (b) and (c) are the fluid temperature T, respectively. m T l The heat exchange process corresponding to that time.

[0067] As can be seen from the above analysis, fluids at different temperature stages can all achieve sufficient heat exchange in the wide-temperature-range cascade heat utilization thermoelectric power generation system of the present invention.

[0068] Figure 2 and Figure 3 The figure shows a structural diagram of an adaptive wide-temperature-range cascade thermal utilization thermoelectric power generation system based on phase change heat transport according to an embodiment of the present invention. As shown in the figure, the system includes an inlet pipe 1, an outlet pipe 10, a fluid tube bundle 11, a liquid storage tank 3, a boiling flow pipe 4, a thermoelectric module, a cooling return pipe 5, and a cooling component.

[0069] The inlet pipe 1, fluid tube bundle 11, and outlet pipe 10 are connected end to end to provide a flow channel for fluids with a wide temperature range. Preferably, an inlet variable cross-section channel 2 is connected between the inlet pipe 1 and the inlet of the fluid tube bundle 11, where the fluid with a certain initial velocity is buffered before flowing into the intermediate tube bundle 11; an outlet variable cross-section channel 9 is connected between the tail of the fluid tube bundle 11 and the outlet pipe 10 to discharge the waste gas after heat exchange.

[0070] The liquid storage tank is divided into three storage spaces along the wide-temperature-range fluid flow direction. Different storage spaces are filled with phase change media with different boiling points, and the boiling point gradually decreases along the flow direction, achieving cascade heat exchange. Fluid tube bundle 11 is inserted within the liquid storage tank 3, exchanging heat with the phase change media and providing energy for its phase change. The structure of the fluid tube bundle 11 can increase the heat exchange area.

[0071] In this embodiment, the liquid storage tank includes a lower fluid tube bundle 11, which is separated from the upper phase change medium storage space by the tube bundle wall. The phase change medium storage space is divided by a partition to form a square storage space. In practice, the square structure is not necessary and other shapes are also possible.

[0072] Preferably, each liquid storage space is provided with an upwardly contracting flared port at the top to facilitate the outflow of gas.

[0073] Each liquid storage space is connected to a set of thermoelectric modules at its top via a boiling flow pipe 4. The thermoelectric modules are then connected back to the bottom of the liquid storage space via a cooling return pipe 5, enabling the phase change medium to circulate between the liquid storage space and the thermoelectric modules. The cold plate of the thermoelectric module is further connected to a cooling component for heat dissipation.

[0074] In a preferred embodiment, a set of thermoelectric modules includes one collector 6, two thermoelectric elements 8, and two water-cooled plates 7. The thermoelectric elements 8 are attached to both ends of the collector 6 to provide a heat source for the hot ends of the thermoelectric elements 8; the cold ends of each thermoelectric element 8 are attached to the water-cooled plates 7 for heat dissipation; a boiling flow pipe 4 and a cooling return pipe 5 are welded to the top and bottom of the collector, respectively, to provide a flow path for the gaseous phase change medium and realize heat transport. The cooling assembly can be a cooling water system, connected to the cooling medium outlet and inlet of the water-cooled plates 7.

[0075] In a preferred embodiment, the cold end of the thermoelectric element 8 is attached to the water-cooled plate 7 with thermally conductive adhesive, and the hot end is sandwiched between graphite paper and the collector 6 and then fastened together with bolts to form a sandwich structure. The graphite paper serves to reduce contact thermal resistance.

[0076] The operation process of the thermoelectric power generation system of this invention is as follows: A wide-temperature-range fluid obtained from different production processes enters the device through the wide-temperature-range fluid inlet pipe 1. It is buffered at the inlet variable cross-section channel 2 and uniformly enters the fluid tube bundle 11. Heat exchange occurs between the fluid tube bundle 11 and phase change media with different boiling points in different compartments of the storage tank 3, achieving heat transfer of the wide-temperature-range fluid. After heat exchange, the low-temperature homogeneous fluid flows out through the outlet variable cross-section channel 9 to the wide-temperature-range fluid outlet pipe 10, achieving the discharge of the low-temperature fluid. The phase change medium after phase change enters the corresponding collector 6 through the corresponding boiling flow pipe 4, releasing its latent heat of vaporization in the collector 6 to provide a constant heat flux to the hot end of the thermoelectric element 8. The condensed liquid medium returns to the storage tank 3 through the cooling return pipe 5, realizing the heat and mass transfer cycle of the phase change medium. The thermoelectric element 8 converts a portion of the absorbed heat into electrical energy, realizing the conversion and utilization of heat transport of fluids over a wide temperature range. Excess heat is carried away by the cooling water in the water-cooled plate 7. After the heat of the heated cooling water is supplied to other heat-requiring devices, it is cooled and then returned to the water-cooled plate 7 to realize the heat and mass transfer cycle of the cooling water.

[0077] The type of the thermoelectric sheet 8 is selected according to the highest average temperature on the surface of the collector 6. The maximum temperature tolerance of the thermoelectric sheet 8 gradually decreases with the flow direction of the wide-temperature fluid. A variety of thermoelectric sheets such as high-temperature thermoelectric sheets, medium-temperature thermoelectric sheets, and low-temperature thermoelectric sheets are sequentially selected according to the flow direction to adapt to the optimal working range.

[0078] The types and quantities of the intermediate media in the present invention are not fixed. The types and masses of the intermediate media can be increased or decreased to change the requirements for cascade utilization of temperature difference power generation. The size of the box for containing the intermediate media is adjusted according to the heat exchange requirements, and the boiling point and working range of the intermediate phase change media are selected as required.

[0079] This embodiment specifically gives the required mass m of a phase change medium i and the outer surface area A of the tube bundle i of the matching design scheme. First, the number of cavities is determined according to the temperature gradient, and the temperature gradient in each cavity is reduced by increasing the number of cavities. Then, due to the different thermophysical properties of different phase change media, the phase change media have different boiling heat transfer coefficients h i during boiling. The heat required in each cavity is selected as the required heat flux density, and the boiling heat transfer coefficient h i of the phase change medium is calculated. Then, the required heat exchange amount Q i in each cavity is calculated, so as to determine the required mass m i of the phase change medium and the relationship between the outer surface area A i of the tube bundle and the heat exchange area; according to this matching relationship, the matching design is carried out. Finally, the designed A i and m i can be used to verify whether the heat exchange amount is reasonable.

[0080] The matching calculation process for the mass of the phase change medium in the liquid storage space and the external area of the tube bundle is as follows:

[0081] Step 1: Summarize the above case. Let the number of cavities be n, i be the corresponding serial number of the cavity (1 < i < n), and the temperature of the inlet fluid be T i_in ; for each liquid storage space i with heat exchange, a required heat flux density q i is given, and the boiling heat transfer coefficient h i is obtained by using formulas (22) and (23):

[0082]

[0083] In the above formula, T i_in is the temperature of the fluid entering the liquid storage space i; if the liquid storage space i is the first liquid storage space where heat exchange occurs, then T i_inLet T be the temperature of the fluid over a wide temperature range; if the storage space i is any storage space after the first storage space where heat exchange occurs, then T i_in For phase change medium b in the (i-1)th liquid storage space i-1 The boiling temperature, T i Phase change medium b in liquid storage space i i boiling temperature; r i The latent heat of vaporization of the phase change medium in the storage space i; c pli Pr is the specific heat capacity of the phase change medium. li ρ is the Prandtl number of the phase change medium. li ρ vi These are the liquid density and gas density of the phase change medium, respectively, η li Let σ be the dynamic viscosity of the phase change medium. i q represents the surface tension of the phase change medium. i The required heat flux density for the corresponding cavity; C wli Empirical coefficients for phase change media;

[0084] Given the mass flow rate of a wide-temperature-range fluid. Based on the boiling heat transfer coefficient h i Using relational expressions Determine the heat transfer Q between the phase change medium and the wide-temperature-range fluid in the storage space i. i , with the outer surface area A of the tube bundle i The relationship.

[0085] Step 3: Based on m i =Q i / r i and Q i With A i The relationship is obtained to obtain the phase change medium m in the liquid storage space i. i With A i The relationship.

[0086] Step 4: Based on m i With A i The relationship, through joint selection m i With A i Ensure that the volume of the phase change medium does not exceed the volume of the intermediate tube bundle.

[0087] After this, you can proceed with step 1, q. i Verification of the reasonableness of the selected value: m selected in step 4 i Substitute m i =Q i / r i , get Q i Then use the formula q i =Q i / Ao calculates qi ; compared with the q assumed in step 1 i Compare the two values. If the difference is within a certain range, then the value of q set in step 1 is considered to be true. i Reasonable.

[0088] In the specific embodiments of the present invention, the three phase change media can be selected as liquid sodium metal, heat transfer oil, and cooling / water, respectively.

[0089] This invention is applicable to devices such as diesel combustion chambers, boilers, and gas turbines that have the ability to generate fluids over a wide temperature range, and is not limited to any specific device.

[0090] The cavity structure of this invention is not limited to the examples given. Under the premise of strength, finding a suitable pipe arrangement is beneficial to improving the corresponding heat exchange area and heat exchange capacity. The compartment for holding the medium is not limited to a cuboid. When there are other volume restrictions, its shape can be changed as needed. The type and quantity of the medium are not limited. The mass of the medium and the number of cavities can be increased according to specific requirements.

[0091] The specific embodiments described above only illustrate the design principles of the present invention. The shapes and names of the components in this description may differ and are not limited. Therefore, those skilled in the art can modify or make equivalent substitutions to the technical solutions described in the foregoing embodiments; and these modifications and substitutions do not depart from the inventive spirit and technical solutions of the present invention, and should all fall within the protection scope of the present invention.

Claims

1. An adaptive wide-temperature-range cascade thermal utilization thermoelectric power generation system based on phase change heat transport, characterized in that, include: Inlet pipe (1), outlet pipe (10), fluid tube bundle (11), liquid storage tank (3), boiling flow pipe (4), thermoelectric module, cooling return pipe (5), cooling assembly; The inlet pipe (1), fluid tube bundle (11), and outlet pipe (10) are connected in sequence to provide a flow channel for fluids with a wide temperature range; The liquid storage tank is divided into multiple liquid storage spaces by a partition along the direction of fluid flow in a wide temperature range. Different liquid storage spaces are filled with phase change media with different boiling points. The boiling point gradually decreases along the direction of fluid flow in a wide temperature range, realizing stepwise heat exchange. The fluid tube bundle (11) is inserted in the liquid storage tank (3) to exchange heat with the phase change media and provide energy for the phase change media's physical state change. Each liquid storage space is connected to a set of thermoelectric modules at the top via a boiling flow pipe (4). The thermoelectric modules are connected back to the bottom of the liquid storage space via a cooling return pipe (5), realizing the circulation of the phase change medium in the liquid storage space and the thermoelectric modules. The cold plate of the thermoelectric module is further connected to the cooling components. The thermoelectric module includes a collector (6), thermoelectric elements (8), and a water-cooled plate (7); thermoelectric elements (8) are attached to both ends of the collector (6) to provide a heat source for the hot end of the thermoelectric elements (8); the cold end of each thermoelectric element (8) is attached to the water-cooled plate (7) for heat dissipation; the boiling flow pipe (4) and the cooling return pipe (5) are welded to the top and bottom of the collector respectively, and the phase change medium condensed in the collector flows back to the storage tank by gravity through the cooling return pipe (5); The selection of thermoelectric elements in multiple thermoelectric modules is as follows: along the direction of fluid flow over a wide temperature range, thermoelectric elements with different operating temperatures are selected to adapt to the optimal operating temperature range. The mass of the phase change medium in the storage space and the external area of ​​the tube bundle were determined through matching calculations: First, for each liquid storage space with heat exchange... i Given the required heat flux density The boiling heat transfer coefficient can be calculated using the following formula. h i : In the formula, To enter the liquid storage space i The fluid temperature; if the storage space i If this is the first liquid storage space where heat exchange occurs, then... The temperature of the fluid over a wide temperature range; if the storage space i For any liquid storage space after the first liquid storage space where heat exchange occurs, then For the first i- Phase change medium in a single liquid storage space b i-1 boiling temperature For liquid storage space i Medium phase change medium b i The boiling temperature; For liquid storage space i The latent heat of vaporization of a phase change medium; Specific heat capacity of the phase change medium; The Prandtl number is the phase change medium. These are the liquid density and gas density of the phase change medium, respectively. The dynamic viscosity of the phase change medium. The surface tension of the phase change medium; The required heat flux density for the corresponding cavity; Empirical coefficients for phase change media; Given the mass flow rate of a wide-temperature-range fluid. According to the boiling heat transfer coefficient h i Using relational expressions Determine the phase change medium in the liquid storage space i Heat exchange with fluids over a wide temperature range , with the outer surface area of ​​the tube bundle Relationship; according to ,as well as and Relationship, to obtain storage space i Medium phase change medium and Relationship; Finally, according to and Relationship, through joint selection and Ensure that the volume of the phase change medium does not exceed the volume of the intermediate tube bundle.

2. The thermoelectric power generation system as described in claim 1, characterized in that, Each liquid storage space is equipped with an upward-contracting flared port at the top.

3. The thermoelectric power generation system as described in claim 1 or 2, characterized in that, The liquid storage tank includes a fluid tube bundle (11) placed at the bottom, which is separated from the phase change medium storage space at the top by the tube bundle wall.

4. The thermoelectric power generation system as described in claim 1, characterized in that, The cold end of the thermoelectric element (8) is attached to the water-cooled plate (7) with thermally conductive adhesive, and the hot end is sandwiched with graphite paper between it and the collector (6) and then clamped together with bolts to form a sandwich structure.

5. The thermoelectric power generation system as described in claim 1, characterized in that, An inlet variable cross-section channel (2) is connected between the inlet pipe (1) and the inlet of the fluid tube bundle (11); an outlet variable cross-section channel (9) is connected between the tail of the fluid tube bundle (11) and the outlet pipe (10).

6. The thermoelectric power generation system as described in claim 1, characterized in that, The liquid storage tank (3) is divided into three parts by a partition along the direction of fluid flow in a wide temperature range, and is filled with a high-temperature phase change medium, a medium-temperature phase change medium and a low-temperature phase change medium respectively.

7. The thermoelectric power generation system as described in claim 6, characterized in that, The high-temperature phase change medium is liquid metallic sodium; the medium-temperature phase change medium is heat-conducting oil; and the low-temperature phase change medium is water.

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