Thermoelectric power generation system giving consideration to thermoelectric double loads and transient multi-field coupling simulation method

Abstract

According to the thermoelectric power generation system considering the thermoelectric double loads, starting is assisted by the storage battery, electric energy is provided for the heating pot and the cooling water pump, after the heating pot and the cooling water pump work, the hot spot device generates power through the temperature difference, the generated electric energy is fed back to the heating pot and the cooling water pump, and therefore high-temperature fuel gas and cooling water continue to be provided for temperature difference power generation. According to the scheme of auxiliary starting of the storage battery, self-starting under the condition of small power supply is realized. Meanwhile, heat preservation in a low-temperature environment is provided for the engine through cyclic utilization of a cooling medium, and cold start of the engine is guaranteed on the premise that electric heating cannot be conducted and the air inlet temperature is not increased. The invention further provides a simulation method of the system, the equivalent thermal load of the engine is introduced for the transient model of the thermoelectric power generation system, equivalent simplification is carried out, and the time cost is greatly reduced while the accuracy of the model is guaranteed to a large extent.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric power generation, and particularly relates to a thermoelectric power generation system that takes into account both thermal / electric dual loads and a transient multi-field coupling modeling method for this system. Background Art

[0002] The application prospect of the thermoelectric combined heat and power supply system based on the Seebeck effect in extreme environments is broad. In deep space, deep sea, polar regions, and low-temperature environments, the thermoelectric combined heat and power supply device needs to have characteristics such as long-term reliability, maintenance-free, adaptability to low-temperature environments, and good low-temperature starting performance. In recent years, the rapid development of thermoelectric materials has continuously improved the maturity of the thermoelectric combined heat and power supply device based on the Seebeck effect, and there have been important application breakthroughs in both military and civilian fields. However, there is still a lack of an efficient simulation method for the thermoelectric conversion device based on the Seebeck effect that considers the thermal / electric loads of the device, and this method is crucial for quickly determining the key design parameters of the device under the constraints of the thermal / electric load demand indicators at the initial stage of device design. Summary of the Invention

[0003] In view of this, the present invention provides a thermoelectric power generation system that takes into account both thermal / electric dual loads and a transient multi-field coupling modeling method for this system, which can achieve efficient simulation considering thermal / electric loads.

[0004] To solve the above technical problems, the present invention is implemented as follows.

[0005] A thermoelectric power generation system that takes into account both thermal and electric dual loads, the thermoelectric power generation system includes: a thermoelectric power generation device composed of a collector, a thermoelectric device, and water cooling, a heating pot, a cooling water pump, and a storage battery;

[0006] At the beginning of the operation of the thermoelectric power generation system, first, the storage battery supplies power to the heating pot for ignition. The high-temperature flue gas after combustion enters the collector of the thermoelectric power generation device for convective heat transfer, and the released heat is conducted from the inner wall surface to the hot end of the thermoelectric device material along the normal direction of the inner wall surface of the collector;

[0007] The cooling water pump is also powered by the storage battery. The cooling medium enters the water cooling plate of the thermoelectric power generation device to provide low temperature for the cold end of the thermoelectric device material; after the cooling medium exchanges heat through the water cooling plate, the cooling medium with increased temperature is introduced into the engine to keep the engine warm; after the cooling medium further exchanges heat in the engine, the temperature decreases, and it is pumped back into the water cooling plate by the cooling water pump to form a recycling of the water cooling medium;

[0008] The thermoelectric device converts the temperature difference between the hot end and the cold end into electric energy, replaces the storage battery to supply power to the heating pot and the cooling water pump, and the remaining electric energy is further output to supply power to external devices.

[0009] The present invention provides a transient multi-field coupling simulation method for the above-mentioned thermoelectric power generation system that takes into account both thermal and electric dual loads, including:

[0010] Step 1: Use Matlab / Simlink software to build a system model:

[0011] According to the heat transfer relationship of the thermoelectric power generation system, the heat release model of the high-temperature flue gas in the collector, the temperature change model of the inner surface of the collector, the heat exchange model of the thermoelectric material of the thermoelectric device, the heat exchange model of the cooling medium in the water-cooled plate, the temperature change model of the water-cooled plate over time, the engine heat exchange model, and the electrical output model of the thermoelectric device are constructed;

[0012] When constructing the engine heat exchange model, the engine is simplified into an equivalent solid module with a thickness of a and a heat transfer area of ​​b, where a and b are determined according to the engine; the cooling medium and the ambient air respectively conduct convective heat exchange on the heat transfer areas on both sides of the equivalent solid module, and heat is transferred along the thickness direction, and it is assumed that the equivalent solid module has no temperature gradient in all directions and the remaining sides are insulated; the cooling medium returns to water after releasing heat and is re-pumped into the water cooling plate of the thermoelectric power generation device to form a cycle; according to the heat exchange relationship between the equivalent engine and the cooling medium and air, a convective heat exchange model between the engine equivalent solid module and the cooling medium and the ambient air is constructed as the engine heat exchange model;

[0013] Step 2: Combine the models constructed in step 1 to simulate the thermoelectric power generation system.

[0014] Preferably, the engine heat exchange model is constructed as follows:

[0015]

[0016]

[0017] Among them, Q ir Convection heat transfer between the cooling medium and the equivalent solid module of the engine; is the cooling medium flow rate, m ir is the engine equivalent solid module mass; c l is the specific heat capacity of the cooling medium, c ir is the specific heat capacity of the engine equivalent solid module; is the average convection coefficient between the cooling medium and the engine equivalent solid module, h is the average convection coefficient between the ambient air and the engine equivalent solid module; A lh is the convection heat transfer area between the cooling medium and the equivalent solid module of the engine, A is the convection heat transfer area between the ambient air and the equivalent solid module of the engine, A lh =A;T lo,I is the outlet temperature of the cooling medium of the water-cooled plate of the thermoelectric power generation device, T ir is the engine equivalent solid module temperature, T ∞ is the ambient air temperature.

[0018] Preferably, the construction of the heat release model of the high-temperature flue gas in the heat collector for heat exchange is as follows:

[0019] The high-temperature flue gas passes through the heat collector of the thermoelectric power generation device, and convective heat transfer occurs. According to the arrangement of the thermoelectric devices, it is evenly divided into modular zones. Suppose there are a total of M modules, and each module corresponds to a complete sandwich structure including a heat collector, a thermoelectric device, and a water-cooled plate. Then the heat release model of the high-temperature flue gas as a heat source in the heat collector is:

[0020]

[0021] where Q Hi is the heat released by the high-temperature flue gas in the heat collector of the i-th module, is the high-temperature flue gas flow rate, c p is the specific heat capacity of the high-temperature flue gas, is the average convective coefficient of the high-temperature flue gas, A h is the convective heat transfer area between the heat collector and the high-temperature flue gas, T i is the inlet temperature of the high-temperature flue gas of the i-th module, T w,i is the inner wall surface temperature of the heat collector of the i-th module through which the high-temperature flue gas passes;

[0022] The total heat released by the high-temperature flue gas in the heat collector is: Q H =∑Q Hi , i = 1, 2…, M.

[0023] Preferably, the construction of the inner surface temperature change model of the heat collector is as follows:

[0024] The heat released by the convective heat transfer of the high-temperature flue gas is conducted from the inner wall surface to the hot end of the thermoelectric device material along the normal direction of the inner wall surface of the heat collector; the thermal resistance in the transverse heat transfer process is only the heat collector, and the thermal resistance in the normal heat transfer process is the heat collector, the ceramic plate of the thermoelectric device, and the conductive copper sheet of the thermoelectric device; according to the law of conservation of energy, the heat released by the high-temperature flue gas is respectively absorbed by the heat collector and conducted by the thermoelectric device, and the inner surface temperature change model of the heat collector is determined as:

[0025]

[0026] where m w is the mass of the heat collector, c w is the specific heat capacity of the heat collector; the thermoelectric device is divided into multiple modules, and each module corresponds to a complete sandwich structure including a heat collector, a thermoelectric device, and a water-cooled plate, T w,i is the inner wall surface temperature of the heat collector of the i-th module through which the high-temperature flue gas passes, T h,i is the hot end temperature of the thermoelectric device of the i-th module, Q Hi is the heat released by the high-temperature flue gas in the heat collector corresponding to the i-th module, Q hi is the heat absorbed by the thermoelectric device of the i-th module, Qw,i is the heat difference between two adjacent modules of the thermoelectric device; R li is the sum of the normal heat transfer direction collector, ceramic plate, and copper sheet thermal resistances corresponding to the i-th module; R wi is the collector thermal resistance in the transverse heat transfer direction corresponding to the i-th module;

[0027] The heat absorbed by the thermoelectric device is Q h = ∑Q hi , i = 1, 2…, M.

[0028] Preferably, the construction of the thermoelectric material heat exchange model of the thermoelectric device is as follows:

[0029] The heat absorbed by the thermoelectric device is partly conducted by the thermoelectric device to the water-cooled plate, and the other part is absorbed by the thermoelectric material to raise the equivalent temperature T of the thermoelectric device TEG until it stabilizes. Another part is converted into the electrical energy output by the thermoelectric device. The thermoelectric material heat exchange model of the thermoelectric device is constructed as the variation of the temperature of the thermoelectric material of the thermoelectric device with time:

[0030]

[0031]

[0032] Among them, the thermoelectric device is divided into M modules, and each module corresponds to a complete sandwich structure including a collector, a thermoelectric device, and a water-cooled plate. Q ci is the heat released by the thermoelectric device of the i-th module, Q hi is the heat absorbed by the thermoelectric device of the i-th module, Q ri is the output power of the thermoelectric device of the i-th module; m p , m n are the masses of the p-type and n-type materials in the thermoelectric device respectively, c p′ , c n′ are the specific heat capacities of the p-type and n-type materials respectively; is the average Seebeck coefficient corresponding to the pn junction of the thermoelectric device of the i-th module, is the average thermal conductivity of the pn junction, is the average resistivity of the pn junction, A leg is the cross-sectional area in the heat transfer direction of the pn junction, H is the height of the pn junction, N i is the number of pn junctions in the i-th module area; T c,i is the cold-end temperature of the thermoelectric device of the i-th module, T h,i is the hot-end temperature of the thermoelectric device of the i-th module, T TEG,i is the equivalent temperature of the thermoelectric device of the i-th module; I is the output current of the thermoelectric power generation device;

[0033] The total heat released by the thermoelectric device is: Q c = ∑Qci , where \(i = 1, 2, \ldots, M\).

[0034] Preferably, the construction of the heat exchange model of the cooling medium in the water-cooled plate and the model of the change of the water-cooled plate temperature over time is as follows:

[0035]

[0036] Among them, the thermoelectric device is divided into \(M\) modules, and each module corresponds to a complete sandwich structure including a collector, a thermoelectric device, and a water-cooled plate. \(Q\) CW,i is the heat absorption of the cooling medium in the \(i\)-th module, and \(Q\) ci is the heat release of the thermoelectric device in the \(i\)-th module; is the flow rate of the cooling medium, and \(c\) l is the specific heat capacity of the cooling medium, is the average convective coefficient of the high-temperature flue gas, and \(A\) lh is the convective heat transfer area between the collector and the high-temperature flue gas, and \(R\) c,i is the thermal resistance in the heat transfer direction of the water-cooled plate in the \(i\)-th module, and \(T\) lin,i is the inlet temperature of the cooling water of the water-cooled plate in the \(i\)-th module, and \(T\) s,i is the outer wall temperature of the water-cooled plate in the \(i\)-th module, and \(T\) lo,i is the outlet temperature of the cooling water of the water-cooled plate in the \(i\)-th module, where \(T\) lo,i = \(T\) lin,i+1 ; \(m\) s is the mass of the water-cooled plate, and \(c\) s is the specific heat capacity of the water-cooled plate;

[0037] The total heat absorption of the cooling medium is: \(Q\) CW = \(\sum Q\) CW,i , where \(i = 1, 2, \ldots, M\).

[0038] Preferably, the construction of the electrical output model of the thermoelectric device is as follows:

[0039] According to the hot and cold end temperatures of the thermoelectric device, calculate the open-circuit voltage of the thermoelectric device, calculate the maximum power generation capacity of the thermoelectric power generation device, connect the heating pot blower, the cooling water pump, and the external device to form an electrical circuit, and perform maximum power point capture through the MPPT controller connected to the electrical output of the thermoelectric power generation device to complete the power output:

[0040]

[0041] \(Q\) E,max = \(I\) 2 \(R\) load

[0042] \(Q\) E = \(Q\) E,max \(\cdot \eta\)

[0043] \(P\)w = ρ·g·H·Q water

[0044] P a = Q a ·ΔP a

[0045] ΔP = Q E - P w - P a

[0046] Wherein, U is the open - circuit voltage of the thermoelectric power generation device, N is the number of pn - junctions of all modules, I is the output current of the thermoelectric power generation device; The thermoelectric device is divided into M modules, and each module corresponds to a complete sandwich structure including a collector, a thermoelectric device, and a water - cooling plate. R TE,i is the internal resistance of the thermoelectric device of the i - th module, R load is the load resistance of the thermoelectric power generation device, Q E,max is the maximum power generation capacity of the thermoelectric power generation device, Q E is the output power of the thermoelectric power generation device after passing through the MPPT controller, η is the efficiency of the MPPT controller, P w is the power consumed by the cooling water pump, ρ is the density of the cooling medium, g is the acceleration due to gravity, H is the head of the cooling water pump, Q water is the flow rate of the cooling water pump, P a is the power consumed by the heating pot blower, Q a is the air flow rate of the blower, ΔP a is the pressure increment of the blower, and ΔP is the net output power of the thermoelectric power generation system; is the average Seebeck coefficient corresponding to the thermoelectric device of the i - th module, T c,i is the cold - end temperature of the thermoelectric device of the i - th module, T h,i is the hot - end temperature of the thermoelectric device of the i - th module.

[0047] Beneficial effects:

[0048] (1) The thermal / electric dual - load thermoelectric power generation system provided by the present invention is assisted by a battery for starting, providing electrical energy for the heating pot and the cooling water pump. After the heating pot and the cooling water pump work, the thermoelectric device generates electricity using the temperature difference and feeds the generated electricity back to the heating pot and the cooling water pump, thereby continuing to provide high - temperature gas and cooling water for the temperature - difference power generation. This battery - assisted starting scheme realizes self - starting under small - power supply conditions. At the same time, the system of the present invention provides heat preservation for the engine in a low - temperature environment through the recycling of the cooling medium, ensuring cold starting of the engine on the premise that electric heating cannot be carried out and the intake air temperature is not increased.

[0049] (2) The present invention combines the actual engine cold start problem and introduces the engine equivalent heat load into the transient model of the thermoelectric power generation system, so that the transient model of the thermoelectric power generation system can analyze the actual situation in more aspects, improves the operability of the transient model of the thermoelectric power generation system, and breaks through the limitations of the existing model.

[0050] (3) The present invention provides a transient multi-field coupling modeling and simulation method for a thermoelectric power generation system that takes into account both thermal and electrical loads. It performs equivalent simplification on the thermal load of the engine, saving the time for thermal resistance analysis caused by the complex structure of the engine. Reasonable simplification can greatly reduce the time cost while ensuring the accuracy of the model to a large extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Schematic diagram of a thermal / electric dual-load thermoelectric power generation system.

[0052] Figure 2 Thermal resistance diagram of thermoelectric power generation device.

[0053] Figure 3 Flowchart for establishing a transient multi-field coupling model for a thermal / electric dual-load thermoelectric power generation system.

[0054] Figure 4 It is a schematic diagram of the structure and modular partitioning of a plate-type thermoelectric power generation device.

[0055] Figure 5 This is a schematic diagram of the structure and modular partitioning of a cylindrical thermoelectric conversion device. DETAILED DESCRIPTION

[0056] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0057] like Figure 1 As shown, the heat / electric dual-load thermoelectric power generation system provided by the present invention includes a thermoelectric power generation device, a heating pot, a cooling water pump and a battery; the thermoelectric power generation device includes a collector, a thermoelectric device, and a water-cooled plate. Among them, the heating pot is a burner independent of the engine, which is used to heat the coolant of the automobile power system and assist in starting in a low-temperature environment. In a low-temperature environment, the present invention uses a cooling medium with a certain temperature that has been heat exchanged by a water-cooled plate to keep the engine warm. After convection heat exchange with the engine ambient air, the temperature of the cooling medium is reduced and reused for low-temperature cooling of the water-cooled plate. The system of the present invention provides insulation for the engine in a low-temperature environment by recycling the cooling medium, and ensures the cold start of the engine under the premise that electric heating cannot be performed and the intake temperature is not increased. At the same time, the battery-assisted system starting method can guide the system into a normal working state while providing a small amount of additional electricity, thereby realizing self-starting under low power supply conditions.

[0058] See also Figure 1The working mode of the thermoelectric power generation system is as follows: at the beginning of the operation of the thermoelectric power generation system, the battery first supplies power to the heating pot to ignite it, and the high-temperature flue gas after combustion enters the collector of the thermoelectric power generation device for convective heat exchange, and the released heat is conducted from the inner wall surface along the normal direction of the inner wall surface of the collector to the hot end of the thermoelectric device material;

[0059] The cooling water pump is also powered by the battery. The cooling medium enters the water-cooled plate of the thermoelectric power generation device to provide low temperature for the cold end of the thermoelectric device material. After the cooling medium exchanges heat through the water-cooled plate, the heated cooling medium is passed into the engine. At the same time, the engine dissipates heat to the low-temperature environment to achieve thermal balance and finally realize the heat preservation of the heating pot. After the cooling medium exchanges heat in the engine, the temperature is reduced and it is pumped back into the water-cooled plate by the cooling water pump, forming a recycling of the water-cooled medium.

[0060] Thermoelectric devices convert the temperature difference between the hot end and the hot end into electrical energy, replacing batteries to power the heating pot and cooling water pump. The remaining electrical energy is further output to power external devices.

[0061] The above system has fluid-solid coupled heat transfer, solid heat conduction, thermoelectric coupling, etc., so its model construction is relatively complex and needs to consider transient multi-field coupling. In order to verify its performance, the present invention further designs a transient multi-field coupling model simulation scheme.

[0062] First, before establishing the transient multi-field coupling model of the thermal / electric dual-load thermoelectric power generation system, the system must be thermally analyzed. The thermoelectric power generation device is the core of the thermoelectric power generation system, so the thermal resistance analysis is mainly performed on it, such as Figure 2 The thermal resistance includes R l,i (the sum of the thermal resistance of the collector in the heat conduction direction, the thermal resistance of the thermoelectric device ceramic plate, and the thermal resistance of the thermoelectric device conductive copper sheet), R pn (thermal resistance of thermoelectric materials of thermoelectric devices in the direction of heat conduction) and R c,i (Thermal resistance of the water cooling plate in the direction of heat conduction, ignoring the thermal resistance of the ceramic plate and the conductive copper sheet at the cold end of the thermoelectric device).

[0063] Figure 3The transient multi-field coupling modeling process of the heat / electric dual-load thermoelectric power generation system is constructed using Matlab / Simlink software. First, according to the heat transfer relationship of the thermoelectric power generation system, the heat release model of the heat exchange of high-temperature flue gas in the collector, the temperature change model of the inner surface of the collector, the heat exchange model of the thermoelectric material of the thermoelectric device, the heat exchange model of the cooling medium in the water-cooled plate, the temperature change model of the water-cooled plate over time, the engine heat exchange model, and the electrical output model of the thermoelectric device are constructed; among them, the modeling of the engine part is relatively complex. The present invention simplifies the engine into an equivalent solid module, constructs the engine heat exchange model, saves the thermal resistance analysis time caused by the complex structure of the engine, and reasonable simplification can greatly reduce the time cost while ensuring the accuracy of the model to a large extent. Finally, the above-mentioned constructed models are combined to simulate the thermoelectric power generation system.

[0064] The above modeling process is described in detail below.

[0065] Step S1: Parameter analysis of high-temperature flue gas inlet and cooling water inlet.

[0066] At the beginning of the operation of the thermoelectric power generation system, the battery first powers the heating pot to ignite, and the high-temperature flue gas after combustion enters the collector of the thermoelectric power generation device. The circulating water pump is also powered by the battery, and the cooling water enters the water-cooled plate of the thermoelectric power generation device. Determine the inlet flow and temperature of the high-temperature flue gas, and determine the inlet flow and initial temperature of the cooling water.

[0067] Step S2: construct a heat release model for heat exchange of high-temperature flue gas in the collector.

[0068] The high-temperature flue gas passes through the collector of the thermoelectric power generation device, and convective heat transfer occurs. According to the arrangement of thermoelectric devices, uniform modular partitioning is performed. Assume that there are M modules in total, and each module has n thermoelectric sheets. The modular partitioning is shown in Figure 4 , Figure 5 . Figure 4 It is a plate-type thermoelectric power generation device. Figure 5 It is a cylindrical thermoelectric conversion device, wherein Figure 5 (a) is the exploded view of the overall structure, and (b) is the structure with the water cooling plate hidden. M modules are divided into partitions, and the collector and water cooling plate are also divided into corresponding M modules. Each module corresponds to a complete sandwich structure including collector, thermoelectric device, and water cooling plate. Calculate the heat released by high-temperature flue gas as a heat source in the collector:

[0069]

[0070] Among them, Q Hi is the heat released by high-temperature flue gas from the collector corresponding to the i-th module, is the high temperature flue gas flow rate, c p is the specific heat capacity of high temperature flue gas, is the average convection coefficient of high temperature flue gas, A h is the convection heat transfer area between the collector and the high-temperature flue gas, T i is the high-temperature flue gas inlet temperature of the ith module. w,i is the inner wall temperature of the collector corresponding to the i-th module.

[0071] Step S3: Construct a collector inner surface temperature variation model.

[0072] The heat released by high-temperature flue gas convection heat transfer is conducted from the inner wall surface to the hot end of the thermoelectric device material along the normal direction of the inner wall surface of the collector, and the lateral heat transfer of the collector (parallel to the wall direction) is considered. The thermal resistance of the normal heat transfer process includes the collector, the thermoelectric device ceramic plate, the thermoelectric device conductive copper sheet, the combination of the thermoelectric device semiconductor material and the copper sheet, and the hot end of the thermoelectric device material and the copper sheet at the junction surface are the same temperature boundary conditions. Since only the lateral heat transfer of the collector is considered, the thermal resistance of the lateral heat transfer process is only the collector. According to the law of conservation of energy, the heat released by the high-temperature flue gas is absorbed by the collector and conducted by the thermoelectric device (heat absorption by the thermoelectric device). According to the geometric structure and material composition of the collector, the thermal resistance, specific heat capacity, and mass of the collector are obtained, and the change of the collector temperature over time is calculated.

[0073]

[0074]

[0075] Among them, m w is the mass of the collector, c w is the specific heat capacity of the collector; the thermoelectric device is divided into multiple modules, and the corresponding collector also corresponds to each divided module, T w,i is the inner wall temperature of the collector corresponding to the i-th module through which the high-temperature flue gas passes, T h,i is the hot end temperature of the i-th module of the thermoelectric device, Q Hi is the heat release of high-temperature flue gas from the collector corresponding to the i-th module, Q hi is the heat absorbed by the i-th module of the thermoelectric device, Q w,i is the heat difference between two adjacent modules of the thermoelectric device; R li is the sum of the thermal resistances of the collector, ceramic plate, and copper sheet in the normal heat transfer direction corresponding to the i-th module; R wi is the collector thermal resistance in the lateral heat transfer direction corresponding to the i-th module;

[0076] The specific meaning of formula (2) is: the sum of the heat released by the flue gas of the i-th module and the heat released by the i-1th module is the heat flowing into the collector of the i-th module, the heat absorbed by the thermoelectric device of the i-th module and the heat released by the i-th module are the heat flowing out of the collector of the i-th module, and the difference between the two is the change in the internal energy of the collector of the i-th module. Based on this fluid-solid coupling heat transfer relationship, the change of the collector temperature over time is calculated.

[0077] Step S4: construct a heat exchange model of thermoelectric materials of thermoelectric devices.

[0078] Thermoelectric devices absorb heat and part of it is transferred to the water cooling plate, while the other part is absorbed by the thermoelectric material. TEG It rises until it stabilizes, and part of it is converted into electrical energy output by the thermoelectric device. Calculate the temperature change of the thermoelectric material of the thermoelectric device over time

[0079]

[0080] Among them, the thermoelectric device is divided into M modules, and the corresponding collector also corresponds to each divided module, Q ci The heat released by the i-th module of the thermoelectric device, Q hi is the heat absorbed by the i-th module of the thermoelectric device, Q ei is the output power of the thermoelectric device in the i-th module; m p 、m n are the mass of p-type and n-type materials in the thermoelectric device, respectively, and c p′ 、c n′ are the specific heat capacities of p-type and n-type materials respectively; is the average Seebeck coefficient of the pn junction, is the average thermal conductivity of the pn junction, is the average resistivity of the pn junction, A leg is the cross-sectional area of ​​the pn junction in the heat transfer direction, H is the height of the pn junction, N i is the number of pn junction pairs of the i-th module; T c,i is the cold end temperature of the thermoelectric device in the ith module, T h,i is the hot end temperature of the i-th module of the thermoelectric device, T TEG,i is the equivalent temperature of the thermoelectric device in the i-th module; I is the output current of the thermoelectric power generation device.

[0081] The specific meaning of formula (7) is: the heat absorbed by the thermoelectric device of the i-th module is regarded as the heat flowing into the thermoelectric material, and the heat released by the thermoelectric device of the i-th module is regarded as the heat flowing out of the thermoelectric material. According to the law of conservation of energy, the difference between the above two values ​​minus the power generation of the thermoelectric material is the change in the internal energy of the thermoelectric material. Based on this, the change of the temperature of the thermoelectric material of the thermoelectric device over time is calculated.

[0082] Step S5: construct a heat exchange model of the cooling medium in the water-cooling plate and a model of the temperature change of the water-cooling plate over time.

[0083] The heat released by the thermoelectric device is Q c The cooling water in the water-cooled plate is taken out through the copper sheet, ceramic plate, and water-cooled plate. The heat transfer at the cold end is simplified. The thermal resistance of the copper sheet and ceramic plate of the thermoelectric device at the cold end is negligible. The inner wall temperature of the water-cooled plate is equivalent to the water inlet temperature, and the water inlet temperature of each module water-cooled plate is the same. Calculate the heat exchange of cooling water in the water-cooled plate and the change of the water-cooled plate temperature over time.

[0084]

[0085] Among them, the thermoelectric devices are divided into M modules, and the corresponding collectors and water cooling plates also correspond to each divided module. CW,i is the heat absorbed by the cooling medium of the i-th module, Q ci Dissipate heat for the i-th module of the thermoelectric device; is the cooling medium flow rate, c l is the specific heat capacity of the cooling medium, is the average convection coefficient of high temperature flue gas, A lh is the convection heat transfer area between the collector and the high-temperature flue gas, R c,i is the thermal resistance of the water cooling plate in the heat transfer direction of the i-th module, T lin,i is the cooling water inlet temperature of the water cooling plate of the i-th module, T s,i is the outer wall temperature of the water cooling plate of the i-th module, T lo,i is the cooling water outlet temperature of the water cooling plate of the i-th module, where T lo,i =T lin,i+1 ;m s is the mass of the water cooling plate, c s is the specific heat capacity of the water-cooled plate; since the thermal resistance of the cold-end copper sheet and ceramic plate of the thermoelectric device is negligible, T s =T c .

[0086] The specific meaning of formula (10) is: the heat released by the thermoelectric material of the i-th module is regarded as the heat flowing into the water-cooled plate, and the heat absorbed by the cooling water of the i-th module is regarded as the heat flowing out of the water-cooled plate. The difference between the two is the change in the internal energy of the water-cooled plate, based on which the change of the temperature of the water-cooled plate over time is calculated.

[0087] Step S6: construct an engine heat exchange model.

[0088] The engine is simplified to be a mm thick and has a heat transfer area of ​​bm 2The solid module has water and ambient air for convective heat exchange on the heat transfer areas on both sides, and heat is transferred along the thickness direction. It is assumed that the solid module has no temperature gradient in all directions and the other sides are insulated; the cooling water returns to the thermoelectric power generation device after releasing heat, forming a cycle, and the equivalent engine temperature is calculated. The temperature of the cooling water after releasing heat (the water inlet temperature of the thermoelectric device)

[0089]

[0090] Among them, Q ir Convection heat transfer between the cooling medium and the equivalent solid module of the engine; is the cooling medium flow rate, m ir is the engine equivalent solid module mass; c l is the specific heat capacity of the cooling medium, c ir is the specific heat capacity of the engine equivalent solid module; is the average convection coefficient between the cooling medium and the engine equivalent solid module, h is the average convection coefficient between the ambient air and the engine equivalent solid module; A lh is the convection heat transfer area between the cooling medium and the equivalent solid module of the engine, A is the convection heat transfer area between the ambient air and the equivalent solid module of the engine, A lh =A=n;T lo,I is the outlet temperature of the cooling medium of the water cooling plate of the last module of the thermoelectric power generation device, T ir is the engine equivalent solid module temperature, T ∞ is the ambient air temperature.

[0091] Step S7: constructing an electrical output model of the thermoelectric device.

[0092] According to the hot and cold end temperatures of the thermoelectric device, the open circuit voltage of the thermoelectric device is calculated, the maximum power generation capacity of the thermoelectric power generation device is calculated, and the heating pot blower, cooling water pump and other electrical loads are connected to form an electrical circuit. The maximum power point is captured by the MPPT controller to complete the power output under actual conditions.

[0093]

[0094] Q E,max =I 2 R load (15)

[0095] Q E =Q E,max ·η (16)

[0096] P w =ρ·g·H·Q water (17)

[0097] P a =Qa ΔP a (18)

[0098] ΔP=Q E -P w -P a (19)

[0099] Among them, U is the open circuit voltage of the thermoelectric power generation device, N is the number of pn junction pairs of all modules, and I is the output current of the thermoelectric power generation device; the thermoelectric device is divided into M modules, and the corresponding collector and water cooling plate also correspond to each divided module, R TE,i is the internal resistance of the thermoelectric device in the ith module, R load is the load resistance of the thermoelectric generator (R TE =R load ), Q E,max is the maximum power generation capacity of the thermoelectric power generation device, Q E is the output power of the thermoelectric power generation device after passing through the MPPT controller, η is the efficiency of the MPPT controller, P w is the power consumed by the cooling water pump, ρ is the density of the cooling medium, g is the acceleration of gravity, H is the head of the cooling water pump, Q water is the flow rate of the cooling water pump, P a is the power consumed by the heating pot blower, Q a is the air flow rate of the blower, ΔP a is the blower pressure increment, ΔP is the net output power of the thermoelectric power generation system; is the average Seebeck coefficient corresponding to the thermoelectric device of the i-th module; T c,i is the cold end temperature of the thermoelectric device in the ith module, T h,i is the hot end temperature of the i-th module of the thermoelectric device.

[0100] The specific meaning of formula (12) is: the convective heat transfer between cooling water and the engine equivalent solid module is regarded as the heat flowing into the engine equivalent solid module, and the convective heat transfer between low-temperature ambient air and the engine equivalent solid module is regarded as the heat flowing out of the engine equivalent solid module. The difference between the two is the change in internal energy of the engine equivalent solid module. Based on this, the equivalent engine temperature and the temperature of cooling water after heat release (water inlet temperature of the thermoelectric device) are calculated.

[0101] Step S8: Combine the above formulas and sum them to get Q H , Q c , Q CW , Q h , T w , T hi , T ci , I, ΔP, etc.

[0102] Q H =∑QHi (20)

[0103] Q CW =∑Q Cwi (twenty one)

[0104] Q c =∑Q ci (twenty two)

[0105] Q h =∑Q hi (twenty three)

[0106] Where Q H Q is the heat released by high temperature flue gas. CW The heat absorbed by cooling water, Q c Heat released by thermoelectric devices, Q h Absorb heat for thermoelectric devices.

[0107] Step S9: Use the above model to perform system simulation.

[0108] In summary, the present invention designs a thermoelectric power generation system and a transient multi-field coupling simulation method that takes into account both thermal and electric loads. The transient multi-field coupling model of the thermoelectric power generation system that takes into account both thermal and electric loads is built using Matlab / Simlink. While the thermoelectric power generation system is connected to the electric load, the engine is kept warm, and an engine equivalent solid module is added as a heat load, which reduces a lot of time costs for the idea of ​​simplifying the equivalent of the engine. In the process of practical application, it should be considered according to the actual situation, for example, according to different engine configurations, it should be reasonably simplified and equivalent.

[0109] 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. A thermoelectric power generation system that takes into account both thermoelectric and thermal loads, characterized in that: The thermoelectric power generation system comprises: a thermoelectric power generation device consisting of a heat collector, a thermoelectric device, a water cooler, a heating pot, a cooling water pump and a storage battery; At the beginning of the operation of the thermoelectric power generation system, the battery first powers the heating pot to ignite it, and the high-temperature flue gas after combustion enters the collector of the thermoelectric power generation device for convection heat exchange. The released heat is conducted from the inner wall surface along the normal direction of the inner wall surface of the collector to the hot end of the thermoelectric device material; The cooling water pump is also powered by the battery. The cooling medium enters the water-cooled plate of the thermoelectric power generation device to provide low temperature for the cold end of the thermoelectric device material. After the cooling medium exchanges heat through the water-cooled plate, the heated cooling medium is passed into the engine to keep the engine warm. After further heat exchange in the engine, the cooling medium is cooled and pumped back into the water-cooled plate by the cooling water pump, forming a recycling of the cooling medium. Thermoelectric devices convert the temperature difference between the hot end and the hot end into electrical energy, replacing batteries to power the heating pot and cooling water pump. The remaining electrical energy is further output to power external devices.

2. A transient multi-field coupling simulation method for a thermoelectric power generation system taking into account both thermoelectric and dual loads as claimed in claim 1, characterized in that: The method includes: Step 1: Use Matlab / Simlink software to build a system model: According to the heat transfer relationship of the thermoelectric power generation system, the heat release model of the high-temperature flue gas in the collector, the temperature change model of the inner surface of the collector, the heat exchange model of the thermoelectric material of the thermoelectric device, the heat exchange model of the cooling medium in the water-cooled plate, the temperature change model of the water-cooled plate over time, the engine heat exchange model, and the electrical output model of the thermoelectric device are constructed; When constructing the engine heat exchange model, the engine is simplified into an equivalent solid module with a thickness of a and a heat transfer area of ​​b, where a and b are determined according to the engine; the cooling medium and the ambient air respectively conduct convective heat exchange on the heat transfer areas on both sides of the equivalent solid module, and heat is transferred along the thickness direction, and it is assumed that the equivalent solid module has no temperature gradient in all directions and the remaining sides are insulated; the cooling medium returns to water after releasing heat and is re-pumped into the water cooling plate of the thermoelectric power generation device to form a cycle; according to the heat exchange relationship between the equivalent engine and the cooling medium and air, a convective heat exchange model between the engine equivalent solid module and the cooling medium and the ambient air is constructed as the engine heat exchange model; Step 2: Combine the models constructed in step 1 to simulate the thermoelectric power generation system.

3. The method according to claim 2, characterized in that The engine heat exchange model is constructed as follows: Among them, Q ir Convection heat transfer between the cooling medium and the equivalent solid module of the engine; is the cooling medium flow rate, m ir is the engine equivalent solid module mass; c l is the specific heat capacity of the cooling medium, c ir is the specific heat capacity of the engine equivalent solid module; is the average convection coefficient between the cooling medium and the engine equivalent solid module, h is the average convection coefficient between the ambient air and the engine equivalent solid module; A lh is the convection heat transfer area between the cooling medium and the equivalent solid module of the engine, A is the convection heat transfer area between the ambient air and the equivalent solid module of the engine, A lh =A;T lo,I is the outlet temperature of the cooling medium of the water-cooled plate of the thermoelectric power generation device, T ir is the engine equivalent solid module temperature, T ∞ is the ambient air temperature.

4. The method according to claim 2, characterized in that The heat release model of the high-temperature flue gas in the collector heat exchange is constructed as follows: The high-temperature flue gas passes through the collector of the thermoelectric power generation device, and convective heat transfer occurs. According to the arrangement of thermoelectric devices, uniform modular partitioning is performed. Assume that there are M modules in total, and each module corresponds to a complete sandwich structure including collectors, thermoelectric devices, and water-cooled plates. The heat release model of the heat released by the high-temperature flue gas as a heat source in the collector is: Among them, Q Hi is the heat released by high-temperature flue gas from the ith module collector, is the high temperature flue gas flow rate, c p is the specific heat capacity of high temperature flue gas, is the average convection coefficient of high temperature flue gas, A h is the convection heat transfer area between the collector and the high-temperature flue gas, T i is the high-temperature flue gas inlet temperature of the ith module, T w,i is the inner wall temperature of the ith module collector through which high-temperature flue gas passes; The total heat released by high-temperature flue gas in the collector is: Q H =∑Q Hi , i=1,2…,M.

5. The method according to claim 2, characterized in that The collector inner surface temperature variation model is constructed as follows: The heat released by high-temperature flue gas convection heat transfer is conducted from the inner wall surface to the hot end of the thermoelectric device material along the normal direction of the inner wall surface of the collector; the thermal resistance of the lateral heat transfer process is only the collector, and the thermal resistance of the normal heat transfer process includes the collector, the ceramic plate of the thermoelectric device, and the conductive copper sheet of the thermoelectric device; according to the law of energy conservation, the heat released by high-temperature flue gas is absorbed by the collector and conducted by the thermoelectric device, and the temperature change model of the inner surface of the collector is determined as follows: Among them, m w is the mass of the collector, c w is the specific heat capacity of the collector; the thermoelectric device is divided into multiple modules, each module corresponds to a complete sandwich structure including the collector, the thermoelectric device, and the water cooling plate, T w,i is the inner wall temperature of the ith module collector through which high-temperature flue gas passes, T h,i is the hot end temperature of the thermoelectric device in the i-th module, Q Hi is the heat release of high-temperature flue gas from the collector corresponding to the i-th module, Q hi is the heat absorbed by the thermoelectric device of the i-th module, Q w,i is the heat difference between two adjacent modules of the thermoelectric device; R li is the sum of the thermal resistances of the collector, ceramic plate, and copper sheet in the normal heat transfer direction corresponding to the i-th module; R wi is the collector thermal resistance in the lateral heat transfer direction corresponding to the i-th module; The amount of heat absorbed by the thermoelectric device is Q h =∑Q hi , i=1,2…,M.

6. The method according to claim 2, characterized in that The construction of the heat exchange model of thermoelectric materials of the thermoelectric device is as follows: Thermoelectric devices absorb heat and part of it is transferred to the water cooling plate, and the other part is absorbed by the thermoelectric material, making the equivalent temperature of the thermoelectric device T TEG It rises until it stabilizes, and part of it is converted into electrical energy output by the thermoelectric device. The heat exchange model of the thermoelectric material of the thermoelectric device is constructed as the temperature change of the thermoelectric material of the thermoelectric device over time: Among them, the thermoelectric device is divided into M modules, each module corresponds to a complete sandwich structure including collector, thermoelectric device, water cooling plate, Q ci The heat released by the thermoelectric device of the i-th module, Q hi is the heat absorbed by the thermoelectric device of the i-th module, Q ei is the output power of the thermoelectric device in the i-th module; m p 、m n are the mass of p-type and n-type materials in the thermoelectric device, respectively, and c p′ 、c n′ are the specific heat capacities of p-type and n-type materials respectively; is the average Seebeck coefficient corresponding to the pn junction of the thermoelectric device in the i-th module, is the average thermal conductivity of the pn junction, is the average resistivity of the pn junction, A leg is the cross-sectional area of ​​the pn junction in the heat transfer direction, H is the height of the pn junction, N i is the number of pn junction pairs in the ith module area; T c,i is the cold end temperature of the thermoelectric device in the ith module, T h,i is the hot end temperature of the thermoelectric device in the i-th module, T TEG,i is the equivalent temperature of the thermoelectric device of the i-th module; I is the output current of the thermoelectric power generation device; The total heat released by the thermoelectric device is: Q c =∑Q ci , i=1,2…,M.

7. The method according to claim 2, characterized in that The heat exchange model of the cooling medium in the water-cooling plate and the model of the temperature change of the water-cooling plate over time are constructed as follows: Among them, the thermoelectric device is divided into M modules, each module corresponds to a complete sandwich structure including collector, thermoelectric device, water cooling plate, Q CW,i is the heat absorbed by the cooling medium of the i-th module, Q ci Dissipate heat for the thermoelectric device of the i-th module; is the cooling medium flow rate, c l is the specific heat capacity of the cooling medium, is the average convection coefficient of high temperature flue gas, A lh is the convection heat transfer area between the collector and the high-temperature flue gas, R c,i is the thermal resistance of the water cooling plate in the heat transfer direction of the i-th module, T lin,i is the cooling water inlet temperature of the water cooling plate of the i-th module, T s,i is the outer wall temperature of the water cooling plate of the i-th module, T lo,i is the cooling water outlet temperature of the water cooling plate of the i-th module, where T lo,i =T lin,i+1 ;m s is the mass of the water cooling plate, c s is the specific heat capacity of the water-cooled plate; The total heat absorbed by the cooling medium is: Q CW =∑Q CW,i , i=1,2…,M.

8. The method according to claim 2, characterized in that The electrical output model of the thermoelectric device is constructed as follows: According to the hot and cold end temperatures of the thermoelectric device, the open circuit voltage of the thermoelectric device is calculated, the maximum power generation capacity of the thermoelectric power generation device is calculated, and the heating pot blower, cooling water pump and the external devices are connected to form an electrical circuit. The maximum power point is captured through the MPPT controller connected to the electrical output of the thermoelectric power generation device to complete the power output: Q E,max =I 2 R load Q E =Q E,max ·η P.S w Nρ·g·H·Q water P a =Q a ·ΔP a ΔP=Q E -P w -P a Among them, U is the open circuit voltage of the thermoelectric power generation device, N is the number of pn junction pairs of all modules, and I is the output current of the thermoelectric power generation device; the thermoelectric device is divided into M modules, and each module corresponds to a complete sandwich structure including a collector, a thermoelectric device, and a water cooling plate, R TE,i is the internal resistance of the thermoelectric device in the ith module, R load is the load resistance of the thermoelectric generator, Q E,max is the maximum power generation capacity of the thermoelectric power generation device, Q E is the output power of the thermoelectric power generation device after passing through the MPPT controller, η is the efficiency of the MPPT controller, P w is the power consumed by the cooling water pump, ρ is the density of the cooling medium, g is the acceleration of gravity, H is the head of the cooling water pump, Q water is the flow rate of the cooling water pump, P a is the power consumed by the heating pot blower, Q a is the air flow rate of the blower, ΔP a is the blower pressure increment, ΔP is the net output power of the thermoelectric power generation system; is the average Seebeck coefficient corresponding to the thermoelectric device of the i-th module, T c,i is the cold end temperature of the thermoelectric device in the ith module, T h,i is the hot end temperature of the thermoelectric device in the i-th module.

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