Self-adaptive wide-temperature-range gradient heat utilization thermoelectric power generation system based on phase change heat transportation

Abstract

The invention provides a self-adaptive wide-temperature-range cascade heat utilization thermoelectric power generation system based on phase change heat transportation. In the system, an inlet pipeline, a fluid pipe bundle and an outlet pipeline are connected in sequence to provide a flowing channel for wide-temperature-range fluid; the liquid storage box is divided into a plurality of liquid storage spaces in the wide-temperature-range fluid flowing direction, different liquid storage spaces are filled with phase change media with different boiling points, the boiling points are gradually reduced in the wide-temperature-range fluid flowing direction, and cascade heat exchange is achieved. The fluid tube bundle is inserted into the liquid storage tank, exchanges heat with the phase change medium and provides energy for the state 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 backflow pipeline, so that circulation of the phase change medium in the liquid storage space and the thermoelectric modules is realized; the cold plate of the thermoelectric module is further connected with a cooling assembly. The heat utilization of the wide-temperature-range fluid can be realized, the temperature distribution uniformity of the thermoelectric module is improved, and the thermoelectric power generation efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature difference power generation combined with wide temperature range fluid heat utilization, and in particular to an adaptive wide temperature range cascade heat utilization temperature difference power generation system based on phase change heat transport. Background Art

[0002] Thermoelectric power generation technology converts temperature difference directly into electrical energy through the thermoelectric effect, and has the advantages of high efficiency, environmental protection, and low maintenance cost. It is suitable for waste heat recovery, aerospace, automobile energy efficiency improvement, and portable device power supply. In industry, thermoelectric power generation can recover waste heat (such as factories, power stations, etc.) and convert it into electrical energy to improve energy utilization efficiency. In the automotive field, waste heat recovery is used to improve fuel efficiency. In addition, thermoelectric power generation can be combined with other renewable energy sources such as solar energy to improve the overall system efficiency.

[0003] Phase change heat transfer uses the latent heat absorbed or released by a substance during the phase change process to efficiently transfer heat, which has significant advantages. First, the temperature is almost constant during the phase change process, which improves the heat transfer efficiency and ensures temperature stability, and is very suitable for precise temperature control needs. Secondly, phase change materials can store a large amount of heat, and the heat storage density is much higher than that of sensible heat materials, and are widely used in heat storage systems. Different phase change materials cover a range from low temperature to high temperature and are suitable for various industrial applications. In addition, phase change heat transfer can significantly reduce the size of equipment and reduce costs, and has multifunctional properties such as heat dissipation, heat storage and temperature control. It is widely used in electronic heat dissipation, building energy conservation and industrial thermal management.

[0004] In the industrial field, high-energy-consuming industries such as metallurgy, chemicals and cement generate a large amount of high-temperature waste gas and waste liquid. In buildings and municipal facilities, data centers, sewage treatment plants and large kitchens generate high-temperature fluids containing a large amount of waste heat. In the field of transportation, automobile, train and ship engines emit a large amount of high-temperature exhaust gas. These fluids contain a large amount of heat that can be used, but the heat carried by fluids produced by different production processes is different. It is difficult to have a set of equipment to recycle the heat of these wide temperature range fluids, or the traditional temperature difference power generation device will have a problem of poor temperature uniformity when facing wide temperature range fluids, which is not conducive to the conversion and utilization of heat. Summary of the invention

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

[0006] In order to solve the above technical problems, the present invention is implemented as follows.

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

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

[0009] 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 media with different boiling points. The boiling point gradually decreases along the flow direction of the wide temperature range fluid to achieve step heat exchange. The fluid tube bundle is interspersed in the liquid storage tank to exchange heat with the phase change medium and provide energy for the physical state change of the phase change medium.

[0010] A group of thermoelectric modules is connected to the top of each liquid storage space through a boiling flow pipe, and the thermoelectric modules are connected back to the bottom of the liquid storage space through a cooling return pipe, so as to realize the circulation of 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 component.

[0011] Preferably, a bell-mouth interface that contracts upward is provided on the upper portion of each liquid storage space.

[0012] Preferably, the liquid storage tank comprises a lower portion where a fluid tube bundle is placed, which is separated from an upper portion of a phase change medium storage space by a tube bundle wall.

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

[0014] Preferably, the cold end of the thermoelectric sheet is adhered to the water-cooled plate by means of thermally conductive adhesive, and graphite paper is sandwiched between the hot end and the collector and then clamped together by 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; and 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 sheets in the multiple groups of thermoelectric modules is as follows: along the flow direction of the wide temperature range fluid, thermoelectric sheets with different operating temperatures are selected to adapt to the optimal operating temperature range.

[0017] Preferably, the liquid storage tank is divided into three parts by a partition along the flow direction of the wide temperature range fluid, 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 metal nanoparticles; the medium-temperature phase change medium is heat transfer oil; and the low-temperature phase change medium is cooling or water.

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

[0020] First, for each liquid storage space i with heat exchange, the required heat flux density q is given i , using formulas (I) and (II) to calculate the boiling heat transfer coefficient h i :

[0021]

[0022] Where, 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_in is the temperature of the wide temperature range fluid; if the liquid storage space i is any liquid storage space after the first liquid storage space where heat exchange occurs, then T i_in is the phase change medium b in the i-1th liquid storage space i-1 The boiling temperature, T i is the phase change medium b in the liquid storage space i i The boiling temperature of i is the latent heat of vaporization of the phase change medium in the liquid storage space i; c pli is the specific heat capacity of the phase change medium; Pr li is the Prandtl number of the phase change medium, ρ li , vi are the liquid density and gas density of the phase change medium, respectively, li is the dynamic viscosity of the phase change medium, σ i is the surface tension of the phase change medium; q i is the heat flux required for the corresponding cavity; C wli Empirical coefficients of phase change media;

[0023] The mass flow rate of the fluid with a wide temperature range is known. According to the boiling heat transfer coefficient h i , using the relation Determine the heat exchange Q between the phase change medium and the wide temperature range fluid in the liquid storage space i i , and the outer surface area of ​​the tube bundle A i relationship;

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

[0025] Finally, according to m i With A i The relationship between i With A i , ensure that the volume of phase change medium does not exceed the middle tube bundle.

[0026] Beneficial effects:

[0027] (1) The present invention uses intermediate phase change media of different temperature ranges to achieve the cascade utilization of wide temperature range fluids with large temperature differences. When the low-temperature fluid in the wide temperature range fluid passes through the phase change medium in the high temperature range, the phase change medium has not reached the boiling point, no phase change occurs, and only convection heat transfer occurs. The phase change medium has a small specific heat capacity, so the heat transfer is low; when the high-temperature fluid in the wide temperature range fluid enters, the phase change medium reaches the boiling point, and phase change heat transfer occurs. The medium transfers the heat of the fluid to the thermoelectric module, and the fluid temperature is reduced. The fluid after heat exchange and cooling is then heat exchanged with the phase change medium of the next temperature gradient, realizing the cascade heat transfer of the wide temperature range fluid.

[0028] (2) The liquid storage tank of the present invention is connected to the thermoelectric module through the boiling flow pipe and the cooling loop pipe that form a loop gravity heat pipe. It uses gravity and fluid phase change to achieve efficient heat transfer. After the phase change medium is vaporized, it rises to the boiling flow pipe and enters the thermoelectric module. After the thermoelectric module generates electricity using high heat, the condensed liquid phase change material flows back to the liquid storage tank through the cooling reflux pipe under the action of gravity. The whole process is repeated, and no pump or capillary structure is required. The system relies on gravity to drive the liquid to reflux. The present invention designs a tight closed system, which is conducive to the rapid transfer of heat from the hot end to the cold end, the heat exchange response speed is fast, and the impact on the flow of fluids in a wide temperature range is small. At the same time, when the working fluid is transferred between the hot end and the cold end, the overall temperature uniformity is high, and the temperature of the hot end of the thermoelectric module is uniform, which is conducive to improving the efficiency of thermoelectric power generation and increasing the power generation of thermoelectric power generation.

[0029] (3) In a preferred embodiment, a bell-mouth interface that contracts upward is provided at the top of each liquid storage space to facilitate gas discharge.

[0030] (4) In a preferred embodiment, an inlet variable cross-section channel is connected between the inlet pipe and the inlet of the fluid tube bundle, and a wide temperature range fluid with a certain initial velocity is buffered in this part. When the fluid passes through the gradually widening mouth, the cross-sectional area of ​​the pipe increases, and according to the continuity equation, the flow rate of the fluid will decrease. This is because the flow rate is inversely proportional to the flow area, and the fluid must distribute the same flow rate over a larger cross-section. According to the Bernoulli equation, the decrease in flow rate is accompanied by an increase in the static pressure of the fluid, so the gradually widening mouth usually leads to an increase in pressure. The gradually widening mouth can also avoid pressure loss caused by sharp contraction and reduce flow instability.

[0031] (5) In a preferred embodiment, along the flow direction of the wide temperature range fluid, thermoelectric sheets with different operating temperatures are selected to adapt to the optimal operating temperature range. Different thermoelectric sheets are used in different temperature ranges mainly because the performance of thermoelectric materials varies significantly at different temperatures. At low temperatures, the material needs to have a higher Seebeck coefficient and low thermal conductivity to increase the voltage output caused by the temperature difference. The medium temperature range requires the material to balance electrical conductivity and thermal conductivity, which is suitable for 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, so choosing 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. The boiling heat transfer coefficient between the phase change medium and the wide temperature range fluid can be calculated through the boiling point and density, viscosity, surface tension and other properties of the phase change material and the required heat flux density, thereby calculating the heat transfer between the phase change medium and the wide temperature range fluid, thereby determining the required mass of the phase change medium and the outer surface area of ​​the tube bundle to achieve 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The schematic diagram of the adaptive wide temperature range cascade heat utilization temperature difference power generation system based on phase change heat transport of the present invention;

[0035] Figure 2 A three-dimensional diagram of an adaptive wide temperature range cascade heat utilization temperature difference power generation system based on phase change heat transport in an embodiment of the present invention;

[0036] Figure 3 It is a cross-sectional view of an adaptive wide temperature range cascade heat utilization temperature difference power generation system based on phase change heat transport in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0038] The present invention provides an adaptive wide-temperature-range cascade heat utilization thermoelectric 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. In the face of wide-temperature-range fluids, traditional thermoelectric generation devices will have a very poor temperature uniformity problem, which is not conducive to the conversion and utilization of heat. In the present invention, the liquid storage tank is filled with a variety of 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. 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 stepwise 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 exchange 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 is the Prandtl number of the phase change medium, ρ li , vi are the liquid density and gas density of the phase change medium, η li is the dynamic viscosity of the phase change medium, σ i is the surface tension of the phase change medium, q i is the heat flux required for the corresponding cavity, C wli is the empirical coefficient of phase change medium.

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

[0047] 1. When the fluid temperature is T h When the heat exchange rate Q1, Q2, and Q3 can be calculated according to the following formula:

[0048]

[0049]

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

[0051] m1=Q1 / r1(reaches boiling point, absorbs heat) (10)

[0052] m2=Q2 / r2 (11)

[0053] m3=Q3 / r3 (12)

[0054] 2. When the fluid temperature is T m When considering the small specific heat capacity of the phase change medium, the heat transfer Q1 is negligible, and the heat transfer Q2 and Q3 can be calculated according to the following formula:

[0055]

[0056] The evaporation mass m1, m2, and m3 of the three media can be calculated according to 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 When considering the small specific heat capacity of the phase change medium, the heat transfer Q1 and Q2 are negligible, and the heat transfer Q3 can be calculated according to the following formula:

[0061]

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

[0063] m1≈0 (19)

[0064] m2≈0 (20)

[0065] m3=Q3 / r3 (21)

[0066] In actual application, multiple fluids can be selected as needed, not limited to three fluids. The present invention selects three fluids with different boiling points for demonstration. See the schematic diagram. Figure 1 , where (a) corresponds to the initial state of the three fluids, and also the fluid temperature is T h The corresponding heat transfer process when the fluid temperature is T m , T l The corresponding heat exchange process.

[0067] From the above analysis, it can be seen that fluids at different temperature stages can be fully heat exchanged in the wide temperature range cascade heat utilization temperature difference power generation system of the present invention.

[0068] Figure 2 and Figure 3 The structural diagram of the adaptive wide temperature range cascade heat utilization temperature difference power generation system based on phase change heat transport in an embodiment of the present invention is shown. 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, the fluid tube bundle 11, and the outlet pipe 10 are connected end to end in sequence to provide a flow channel for the wide temperature range fluid. Preferably, the inlet variable cross-section channel 2 is connected between the inlet pipe 1 and the inlet of the fluid tube bundle 11, and the wide temperature range fluid with a certain initial velocity is buffered in this part and then flows into the intermediate tube bundle 11; the 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 exhaust gas after heat exchange.

[0070] The liquid storage tank is divided into three liquid storage spaces along the flow direction of the wide temperature range fluid. Different liquid storage spaces are filled with phase change media with different boiling points. The boiling point gradually decreases along the flow direction of the wide temperature range fluid to achieve step heat exchange. The fluid tube bundle 11 is inserted into the liquid storage tank 3 to exchange heat with the phase change medium and provide energy for the physical state change of the phase change medium. The structure of the fluid tube bundle 11 can increase the heat exchange area.

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

[0072] Preferably, a bell-mouth interface that contracts upward is provided on the top of each liquid storage space to facilitate the outflow of gas.

[0073] The top of each liquid storage space is connected to a group of thermoelectric modules through a boiling flow pipe 4, and the thermoelectric modules are connected back to the bottom of the liquid storage space through a cooling return pipe 5, so that the phase change medium circulates in the liquid storage space and the thermoelectric modules. The cold plate of the thermoelectric module is further connected to a cooling component to achieve a heat dissipation effect.

[0074] In a preferred embodiment, a group of thermoelectric modules includes a collector 6, two thermoelectric sheets 8, and two water-cooled plates 7. Thermoelectric sheets 8 are attached to both ends of the collector 6 to provide a heat source for the hot end of the thermoelectric sheet 8; the cold end of each thermoelectric sheet 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, to provide a flow channel for the gaseous phase change medium to achieve heat transport. The cooling assembly can use a cooling water system to connect the cooling medium outlet and inlet of the water-cooled plate 7.

[0075] In a preferred embodiment, the cold end of the thermoelectric sheet 8 is attached to the water-cooled plate 7 by means of a heat-conducting adhesive, and the hot end and the heat collector 6 are clamped together by bolts after being sandwiched with graphite paper to form a sandwich structure. The graphite paper plays a role in reducing the contact thermal resistance.

[0076] The operation process of the temperature difference power generation system of the present invention is as follows: the wide temperature range fluid obtained by different production processes enters the device through the wide temperature range fluid inlet pipe 1, is buffered at the inlet variable cross-section channel 2, and evenly enters the fluid tube bundle 11. The fluid tube bundle 11 exchanges heat with the phase change medium with different boiling points in different compartments in the liquid storage tank 3 to achieve heat transfer of the wide temperature range fluid. After the heat exchange is completed, the low-temperature uniform temperature fluid flows out from the outlet variable cross-section channel 9 to the wide temperature range fluid outlet pipe 10 to achieve 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, releases the latent heat of vaporization in the collector 6, and provides a constant heat flux for the hot end of the thermoelectric plate 8. The condensed liquid medium returns to the liquid storage tank 3 through the cooling reflux pipe 5 to achieve the heat and mass transfer cycle of the phase change medium. The thermoelectric sheet 8 converts part of the absorbed heat into electrical energy, realizing the conversion and utilization of heat transport of fluid in a wide temperature range. The excess heat is taken away by the cooling water in the water-cooled plate 7. The heat of the heated cooling water is supplied to the remaining heat-requiring devices, and then cooled and 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 along the flow direction of the wide-temperature-range 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 type and quantity of the intermediate medium in the present invention are not fixed. The type and mass of the intermediate medium can be increased or decreased to change the demand for cascade utilization of temperature difference power generation. The size of the box for containing the intermediate medium is adjusted according to the demand for heat exchange, and the boiling point and working range of the intermediate phase change medium are selected as required.

[0079] This embodiment specifically gives the required mass m of a phase change medium i matched with the outer surface area A of the tube bundle i design scheme. First, determine the number of cavities according to the temperature gradient, and reduce the temperature gradient in each cavity by increasing the number of cavities. Then, since the thermophysical properties of different phase change media are different, the phase change medium has different boiling heat transfer coefficients h i during boiling. Select the required heat in each cavity as the required heat flux density, calculate the boiling heat transfer coefficient h i of the phase change medium, and then calculate the required heat exchange Q i in each cavity, 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, carry out matching design. Finally, the designed A i and m i can be used to verify whether the heat exchange amount is reasonable.

[0080] The process of matching 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 incoming fluid be T i_in ; for each liquid storage space i with heat exchange, given the required heat flux density q i , use formulas (22) and (23) to calculate the boiling heat transfer coefficient h i :

[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 with heat exchange, then T i_inis the temperature of the wide temperature range fluid; if the liquid storage space i is any liquid storage space after the first liquid storage space where heat exchange occurs, then T i_in is the phase change medium b in the i-1th liquid storage space i-1 The boiling temperature, T i is the phase change medium b in the liquid storage space i i The boiling temperature of i is the latent heat of vaporization of the phase change medium in the liquid storage space i; c pli is the specific heat capacity of the phase change medium; Pr li is the Prandtl number of the phase change medium, ρ li , vi are the liquid density and gas density of the phase change medium, respectively, li is the dynamic viscosity of the phase change medium, σ i is the surface tension of the phase change medium; q i is the heat flux required for the corresponding cavity; C wli Empirical coefficients of phase change media;

[0084] The mass flow rate of the fluid with a wide temperature range is known. According to the boiling heat transfer coefficient h i , using the relation Determine the heat exchange Q between the phase change medium and the wide temperature range fluid in the liquid storage space i i , and the outer surface area of ​​the tube bundle A i relationship.

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

[0086] Step 4: According to m i With A i The relationship between i With A i , ensure that the volume of phase change medium does not exceed the middle tube bundle.

[0087] After this, you can also do step 1 i Verification of the rationality of the value: Set the m selected in step 4 to i Substitute m i =Q i / r i , get Q i , and then use the formula q i =Q i / Ao calculates qi ; and q assumed in step 1 i If the difference between the two is within the range, then the q set in step 1 is considered i Reasonable.

[0088] For the case of three phase change media in the specific implementation manner of the present invention, the high-temperature phase change medium, the medium-temperature phase change medium, and the low-temperature phase change medium can be selected from liquid metal nanoparticles, heat transfer oil, and cooling / water, respectively.

[0089] The present invention is applicable to devices capable of generating fluids in a wide temperature range, such as diesel combustion chambers, boilers, and gas turbines, and is not limited to a specific device.

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

[0091] The above specific embodiments only describe the design principle of the present invention. The shapes and names of the components in the description may be different and are not limited. Therefore, those skilled in the art in the field of the present invention may modify or replace the technical solutions recorded in the above embodiments; and these modifications and replacements do not deviate from the creative purpose 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 heat utilization temperature difference power generation system based on phase change heat transport, characterized in that: include: Inlet pipe (1), outlet pipe (10), fluid pipe bundle (11), liquid storage tank (3), boiling flow pipe (4), thermoelectric module, cooling return pipe (5), cooling assembly; The inlet pipe (1), the fluid pipe bundle (11), and the outlet pipe (10) are connected in sequence to provide a flow channel for a fluid with a wide temperature range; The liquid storage tank is divided into a plurality of liquid storage spaces along the flow direction of the wide temperature range fluid, and different liquid storage spaces are filled with phase change media with different boiling points, and the boiling point gradually decreases along the flow direction of the wide temperature range fluid, thereby realizing step heat exchange; the fluid tube bundle (11) is inserted into the liquid storage tank (3), performs heat exchange with the phase change medium, and provides energy for the physical state 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 pipe (4), and the thermoelectric modules are connected back to the bottom of the liquid storage space through a cooling return pipe (5), so as 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 the cooling component.

2. The thermoelectric power generation system according to claim 1, characterized in that: A bell-mouth interface which contracts upward is arranged on the upper part of each liquid storage space.

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

4. The thermoelectric power generation system according to claim 1, characterized in that: The thermoelectric module comprises a heat collector (6), a thermoelectric sheet (8), and a water-cooled plate (7); the thermoelectric sheets (8) are attached to both ends of the heat collector (6) to provide a heat source for the hot end of the thermoelectric sheet (8); the cold end of each thermoelectric sheet (8) is attached to the water-cooled plate (7) to dissipate heat; a boiling flow pipe (4) and a cooling return pipe (5) are respectively welded to the top and bottom of the heat collector, and the phase change medium condensed in the heat collector flows back to the liquid storage tank through the cooling return pipe (5) by gravity.

5. The thermoelectric power generation system according to claim 4, characterized in that: The cold end of the thermoelectric sheet (8) is adhered to the water-cooled plate (7) by means of heat-conducting adhesive, and the hot end and the heat collector (6) are clamped together by means of bolts after being sandwiched with graphite paper to form a sandwich structure.

6. The thermoelectric power generation system according to 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 pipe bundle (11); and an outlet variable cross-section channel (9) is connected between the tail of the fluid pipe bundle (11) and the outlet pipe (10).

7. The thermoelectric power generation system according to claim 1, characterized in that: The selection of thermoelectric sheets in multiple groups of thermoelectric modules is as follows: along the flow direction of the wide temperature range fluid, thermoelectric sheets with different operating temperatures are selected to adapt to the optimal working temperature range.

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

9. The thermoelectric power generation system according to claim 8, characterized in that: The high-temperature phase change medium uses liquid metal nanoparticles; the medium-temperature phase change medium uses heat transfer oil; and the low-temperature phase change medium uses cooling or water.

10. The thermoelectric power generation system according to claim 1, characterized in that: The mass of the phase change medium in the liquid storage space and the external area of ​​the tube bundle are determined by matching calculation: First, for each liquid storage space i with heat exchange, the required heat flux density q is given i , using formulas (I) and (II) to calculate the boiling heat transfer coefficient h i : Where, 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_in is the temperature of the wide temperature range fluid; if the liquid storage space i is any liquid storage space after the first liquid storage space where heat exchange occurs, then T i_in is the phase change medium b in the i-1th liquid storage space i-1 The boiling temperature, T i is the phase change medium b in the liquid storage space i i The boiling temperature of i is the latent heat of vaporization of the phase change medium in the liquid storage space i; c pli is the specific heat capacity of the phase change medium; P rli is the Prandtl number of the phase change medium, ρ li , vi are the liquid density and gas density of the phase change medium, respectively, li is the dynamic viscosity of the phase change medium, σ i is the surface tension of the phase change medium; q i is the heat flux required for the corresponding cavity; C wli Empirical coefficients of phase change media; The mass flow rate of the fluid with a wide temperature range is known. According to the boiling heat transfer coefficient h i , using the relation Determine the heat exchange Q between the phase change medium and the wide temperature range fluid in the liquid storage space i i , and the outer surface area of ​​the tube bundle A i relationship; According to m i =Q i / r i , and Q i With A i The relationship between the phase change medium m in the liquid storage space i is obtained. i With A i relationship; Finally, according to m i With A i The relationship between i With A i , ensure that the volume of phase change medium does not exceed the middle tube bundle.

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