CN116456798A - Z-type thermoelectric device and parameter optimization method thereof - Google Patents

Z-type thermoelectric device and parameter optimization method thereof Download PDF

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CN116456798A
CN116456798A CN202310255954.6A CN202310255954A CN116456798A CN 116456798 A CN116456798 A CN 116456798A CN 202310255954 A CN202310255954 A CN 202310255954A CN 116456798 A CN116456798 A CN 116456798A
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thermoelectric device
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罗丁
刘泽瑞
杨学林
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China Three Gorges University CTGU
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Abstract

A Z-type thermoelectric device and a parameter optimization method thereof are provided, wherein the Z-type thermoelectric device comprises an upper ceramic plate, a lower ceramic plate, a thermoelectric semiconductor, a first copper electrode, a second copper electrode and a conductor; the bottom surface of the upper ceramic plate is connected with the upper end surface of the first copper electrode, one side of the lower end surface of the first copper electrode is connected with the upper end surface of the thermoelectric semiconductor, and the other side of the lower end surface of the first copper electrode is connected with the upper end surface of the conductor; the lower end face of the thermoelectric semiconductor is connected with the upper end face of the second copper electrode, and the lower end face of the conductor is connected with the upper end face of the third copper electrode; the lower end face of the second copper electrode and the lower end face of the third copper electrode are respectively connected with two sides of the top face of the lower ceramic plate. The invention optimizes the traditional symmetrical PN thermoelectric semiconductor structure, and replaces the side with smaller thermoelectric figure of merit in the P-type semiconductor and the N-type semiconductor by using the fine copper guide, thereby effectively reducing the power loss of the P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor caused by different thermoelectric figure of merit and improving the overall thermoelectric conversion efficiency and the output performance.

Description

Z-type thermoelectric device and parameter optimization method thereof
Technical Field
The invention relates to a thermoelectric device, in particular to a Z-type thermoelectric device and a parameter optimization method thereof.
Background
With the maturity of various material fields and theories, the performance of thermoelectric materials is improved to a great extent, and thermoelectric technology is widely applied to the field of heat recovery, such as automobile exhaust waste heat recovery, industrial waste heat recovery and the like.
The thermoelectric semiconductor thermoelectric material most commonly used in the current thermoelectric refrigeration devices is bismuth telluride. And doping to obtain the P-type and N-type bismuth telluride blocks or device monomers. Bismuth telluride crystals have many performance characteristics, and the bismuth telluride crystals have natural dissimilarity, so that the bismuth telluride crystals become good thermoelectric materials. However, because the output voltage and the power of the single PN junction thermocouple are too low, the output voltage can reach the usable energy level only by cascading a plurality of PN junctions to form the thermoelectric power generation module. In the study of practical single PN junction thermocouples, there have been many proposals about optimization of materials and structures to improve the output power of each thermocouple and its conversion efficiency, wherein some novel configurations are not lacking, for example: annular thermoelectric devices, X-type thermoelectric structures, separated two-stage combined TEG-TEC systems. These structures have been greatly improved over conventional thermoelectric structures. However, these structural optimization methods are all based on the premise that the P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor are connected in series through copper electrodes, that is to say, the current flowing in the P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor is necessarily limited by the smaller side, and the structural dimensions and the same number of the P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor adopted are basically consistent, and the influence caused by the difference of materials of different thermoelectric semiconductors is not considered.
Considering that the parameters of thermoelectric materials of the P electrode and the N electrode are inconsistent, when the PN junction works under the same temperature difference, the current density generated by the P electrode and the N electrode is different, the current is limited due to the different doping concentrations in the materials, and the loss of power and the reduction of thermoelectric conversion efficiency are further caused, specifically:
because the seebeck coefficients, the thermal conductivities and the electric conductivities of the materials used for the P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor are different, if the materials are used under the same working condition, the current in the traditional thermoelectric device is limited to a smaller side, and the output power and the thermoelectric conversion efficiency of the thermoelectric device are reduced as a whole. This is disadvantageous for practical use of thermoelectric devices and further optimization is needed.
Disclosure of Invention
The invention provides a Z-type thermoelectric device and a parameter optimization method thereof, wherein when parameters of the Z-type thermoelectric device meet certain conditions, the power loss of a P-type thermoelectric semiconductor and an N-type thermoelectric semiconductor caused by different thermoelectric figures can be effectively reduced, and the overall thermoelectric conversion efficiency and the output performance are improved.
The technical scheme adopted by the invention is as follows:
a Z-type thermoelectric device comprising: the thermoelectric semiconductor comprises an upper ceramic plate, a lower ceramic plate, a thermoelectric semiconductor, a first copper electrode, a second copper electrode and a conductor;
the bottom surface of the upper ceramic plate is connected with the upper end surface of the first copper electrode, one side of the lower end surface of the first copper electrode is connected with the upper end surface of the thermoelectric semiconductor, and the other side of the lower end surface of the first copper electrode is connected with the upper end surface of the conductor;
the lower end face of the thermoelectric semiconductor is connected with the upper end face of the second copper electrode, and the lower end face of the conductor is connected with the upper end face of the third copper electrode;
the lower end face of the second copper electrode and the lower end face of the third copper electrode are respectively connected with two sides of the top face of the lower ceramic plate.
The length of the conductor in the horizontal direction is as follows: l (L) 2 +i×Δl, wherein: l (L) 2 Representing the initial length of the conductor, i representing the iteration parameter to be determined, al representing the length of each iteration calculation change.
The thermoelectric semiconductor has a horizontal length of L 1 The heights of the upper ceramic plate and the lower ceramic plate are H 1 The heights of the first copper electrode and the second copper electrode are H 2 The thermoelectric semiconductor has a height H 3 The conductor height is H 3 。
The first copper electrode forms a certain included angle theta with the conductor.
The conductor is a fine copper conductor.
The lengths of the first, second and third copper electrodes are L 0 +L 1 +L 2 The method comprises the steps of carrying out a first treatment on the surface of the The length of the upper and lower ceramic plates is 2 (L 1 +L 2 )+3L 0 The distance between the thermoelectric semiconductor and the fine copper conductor is L 0 。
The thermoelectric semiconductor is a P-type thermoelectric semiconductor or an N-type thermoelectric semiconductor. The thermoelectric semiconductor is one of the two selected according to the thermoelectric figure of merit of the actual P-type semiconductor and the N-type semiconductor, namely: the thermoelectric semiconductor is selected from the P-type semiconductor and the N-type semiconductor, which has a larger thermoelectric figure of merit.
The thermoelectric semiconductor is composed of P-type thermoelectric semiconductor and N-type thermoelectric semiconductor, and has thermoelectric figure of merit Z p 、Z n Determining and judging Z p And Z n Is a size relationship of (a):
if Z p ＞Z n A fine copper conductor is adopted to replace an N-type thermoelectric semiconductor;
if Z p ＜Z n A fine copper conductor is adopted to replace a P-type thermoelectric semiconductor;
if Z p ＝Z n The Z-type thermoelectric device has the same performance as the traditional symmetrical thermoelectric device, and a thin copper conductor is not required to replace a P-type thermoelectric semiconductor or an N-type thermoelectric semiconductor.
The invention assumes Z p ＞Z n When the thin copper conductor is adopted to replace an N-type thermoelectric semiconductor, the structural parameters of the Z-type thermoelectric device are determined:
determining parameters of the Seebeck coefficient, the output power of the traditional symmetrical thermoelectric device, the output power of the Z-type thermoelectric device, the optimal fine copper length and the included angle theta, and comprising the following steps:
s1: based on the thermal resistance network, the hot end temperature T of the thermoelectric semiconductor is calculated h And cold end temperature T c Because the copper electrode has higher heat conductivity, the temperature change in the heat conduction process of the copper electrode, namely the temperature T of the hot end of the thermoelectric semiconductor 2, is ignored h And cold end temperature T c Equal to the surface temperature of the corresponding copper electrode;
s2: separately calculating traditional symmetrical thermoelectricOutput power P of device pn Output power P of Z-type thermoelectric device z ；
S3: judging 1/2P pn And P z Determining the magnitude relation of the Z-type thermoelectric deviceConditions, wherein: s is S p 、S n Seebeck coefficients respectively representing the P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor;
s4: determining the length of the thin copper conductor;
s5: and determining an included angle theta.
Determining the use condition of the Z-type thermoelectric device, comprising the following steps:
step 1: determining the output power P of a conventional symmetrical thermoelectric device pn And output power P of Z-type thermoelectric device z The effective thermoelectric semiconductor cross-sectional area of the Z-shaped thermoelectric device is half that of a traditional symmetrical thermoelectric device, and the ratio is 1/2P pn And P z Calculates 1/2P pn ＝P z When (1)Setting critical value +.>
Step 2: by determining when a thermoelectric device is selectedAnd a, determining which thermoelectric device is adopted; if it isThen a conventional symmetrical thermoelectric device is employed; if->Then a Z-type thermoelectric device is employed; if->The Z-type thermoelectric device has the same performance as the traditional symmetrical thermoelectric device, and both thermoelectric devices can be used.
Determining an optimal length of a thin copper conductor of a Z-type thermoelectric device, comprising the steps of:
(i) The method comprises the following steps Setting the value of the step length Deltal to enable
(ii) The method comprises the following steps The output power of the corresponding Z-type thermoelectric device when i=0 and i=1 is recorded as P respectively 0 And P 1 ；
(iii) The method comprises the following steps Judging P 0 And P 1 If P 0 ＜P 1 I=i+1, updating the fine copper length and substituting the next round of output power P i Up to p i ＞p i+1 Exiting the cycle; otherwise, updating the fine copper length to L 2 -ix Δl and substituting the next round of output power P i Up to p i ＞p i+1 And (3) exiting the cycle, reserving the value of the last time i, and calculating the length of the fine copper at the moment, namely the final determined length of the fine copper.
Determining an included angle theta when the maximum output power of the Z-type thermoelectric device is determined, and considering the influence caused by space occupancy and the distance between adjacent conductors, the included angle theta is E [45, 90], comprising the following steps:
a1: setting an initial angle theta 0 Setting a change value delta theta=1° of the included angle; let θ=θ 0 -j x Δθ, where j = 0,1,2, …,45;
a2: calculating the output power of the Z-type thermoelectric device when j takes different values;
a3: and comparing the output power under different included angles theta, and taking the value theta when the output power is maximum, namely the finally determined optimal included angle theta.
Determining a calculation method and boundary conditions required by calculating the output power, wherein the calculation method adopts a numerical discrete method, and the boundary conditions comprise a temperature boundary condition and a current boundary condition;
temperature edgeThe boundary conditions are as follows: the P-type thermoelectric semiconductor and the fine copper conductor are arranged to be insulated from the external environment, and the temperature of the lower bottom surface is arranged to be T c The upper top surface temperature is set to T h In addition, the following:
the temperature of the first contact surface B and the second contact surface F of the P-type thermoelectric semiconductor and the second copper electrode is the same, namelyThe heat conduction of the second copper electrode is equal to the sum of the heat conduction under the P-type thermoelectric semiconductor and the Peltier heat of the P-type thermoelectric semiconductor, and the heat conduction of the second copper electrode is +.>Wherein: z is the height of the first contact surface B and the second contact surface F;
the temperature of the first contact surface C and the second contact surface E of the P-type thermoelectric semiconductor and the first copper electrode are the same,the heat conduction of the first copper electrode is equal to the sum of Fang Daore and Peltier heat of the P-type thermoelectric semiconductor, and the first copper electrode is +.>Wherein: z is the height of the first contact surface C and the second contact surface E.
The current boundary conditions are: the left end face J of the external load R and the left end face A of the second copper electrode are grounded; the right end face I of the applied load R is placed in electrical contact with the right end face G of the third copper electrode.
The invention relates to a Z-type thermoelectric device and a parameter optimization method thereof, which have the following technical effects:
1) When the parameters of the P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor meet certain conditions, the invention can overcome the power loss caused by inconsistent thermoelectric semiconductor materials of the traditional thermoelectric device, improves the space utilization rate, and further improves the thermoelectric performance after certain parameter optimization.
2) Compared with the traditional symmetrical thermoelectric device, the invention takes the electric energy loss caused by the parameter difference of the P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor into consideration, wherein the P-type thermoelectric semiconductor or the N-type thermoelectric semiconductor is replaced by a fine copper conductor. The invention optimizes the traditional symmetrical PN thermoelectric semiconductor structure, and replaces the side with smaller thermoelectric figure of merit in the P-type semiconductor and the N-type semiconductor by using the fine copper guide, thereby effectively reducing the power loss of the P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor caused by different thermoelectric figure of merit and improving the overall thermoelectric conversion efficiency and the output performance.
3) To improve the problem that the current in the conventional thermoelectric device is limited to a smaller side, the output power and the thermoelectric conversion efficiency of the thermoelectric device are reduced as a whole. The invention further improves the overall output power by adopting a mode that the unipolar thermoelectric semiconductor is connected with the copper electrode in series under certain specific conditions.
4) The invention is based on a numerical solution method, judges the condition that the structure can be adopted to improve the power, further optimizes based on the condition, proposes the derivative configuration of the structure, and finally determines the optimal parameters of the Z-type thermoelectric device. When the selected P-type thermoelectric semiconductor and N-type thermoelectric semiconductor materials meet certain conditions, the overall output power and thermoelectric performance can be improved.
Drawings
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
fig. 1 is a schematic diagram of a Z-type thermoelectric device when θ=90°.
Fig. 2 is a boundary condition stereo parsing design diagram.
Fig. 3 is a flow chart of parameter selection for a Z-type thermoelectric device.
FIG. 4 is a graph showing the power of the Z-type thermoelectric conductor as a function of the length of fine copper.
Fig. 5 is a schematic diagram of a Z-type thermoelectric device with θ at an angle.
Fig. 6 is a three-dimensional geometry of the Z-type thermoelectric module when θ=90°.
Detailed Description
The technical scheme of the invention is described below with reference to the accompanying drawings, specific thermoelectric devices and material parameters thereof:
as shown in fig. 1, a Z-type thermoelectric device comprises an upper ceramic plate 1, a lower ceramic plate 1', a thermoelectric semiconductor 2, a first copper electrode 3.1, a second copper electrode 3.2, a third copper electrode 3.3, and a conductor 4,
the bottom surface of the upper ceramic plate 1 is connected with the upper end surface of the first copper electrode 3.1, one side of the lower end surface of the first copper electrode 3.1 is connected with the upper end surface of the thermoelectric semiconductor 2, and the other side of the lower end surface of the first copper electrode 3.1 is connected with the upper end surface of the conductor 4.
The lower end face of the thermoelectric semiconductor 2 is connected with the upper end face of the second copper electrode 3.2, and the lower end face of the conductor 4 is connected with the upper end face of the second copper electrode 3.3.
The lower end face of the second copper electrode 3.2 and the lower end face of the third copper electrode 3.3 are respectively connected with two sides of the top face of the lower ceramic plate 1'. The conductor 4 is a fine copper conductor. Among the currently known materials, the copper conductor is the optimal material with high thermal conductivity and low thermal conductivity, and the fine copper conductor is selected, so that the consumption is reduced by selecting the fine copper in consideration of the fact that a certain temperature difference exists between the cold end and the hot end of the conductor.
The upper and lower end surfaces corresponding to the thin copper conductor are respectively connected with the lower end surface of the first copper electrode 3.1 and the upper surface of the third copper electrode 3.3, the length in the horizontal direction and the longitudinal depth of the thin copper conductor cannot be changed along with the height, and the thin copper conductor is characterized in that the initial length L in the horizontal direction 2 Should not exceed the thermoelectric semiconductor length L 1 A kind of electronic deviceThe height and thickness of the thermoelectric semiconductor 2 are consistent with each other, and the first copper electrode 3.1 forms an angle theta with the conductor 4, the angle theta being 45, 90]Initial angle θ 0 The angle between the two is changed by the magnitude of Δθ=1° until the minimum angle is reached.
The thin copper is connected with the thermoelectric semiconductor in series, wherein the length of the thin copper is L 2 +i×Δl，L 2 Representing the initial length of the fine copper, i being the iteration parameter to be determined, Δl representing the step size calculated per iteration.
The thermoelectric semiconductor 2 has a horizontal length L 1 The heights of the upper ceramic plate 1 and the lower ceramic plate 1' are H 1 The heights of the first copper electrode 3.1 and the second copper electrode 3.2 are H 2 The thermoelectric semiconductor 2 has a height H 3 The height of the conductor 4 is H 3 。
The conductor 4 is fine copper, and the first copper electrode 3.1 forms a certain included angle theta with the conductor 4.
Step one, in the process of simulating a thermal field and an electric field, the control equation set in a steady state is established by considering the Joule heat, the Thomson effect and the Peltier effect simultaneously, namely:
in the above equation: q, j are the heat flux density vector, joule heat and current density vector, respectively, and λ, α, σ and V represent the thermal conductivity, seebeck coefficient, electrical conductivity and electrical potential, respectively.
Step two, as shown in FIG. 2, setting the temperature boundary condition of the Z-type thermoelectric device, setting the P-type thermoelectric semiconductor, the fine copper and the external environment as heat insulation, and setting the temperature of the lower bottom surface as T c Upper top surface temperature settingPut as T h ：
(1) The temperature of the first contact surface B and the second contact surface F of the P-type thermoelectric semiconductor and the second copper electrode 3.2 is the same, and the following conditions are satisfied:
the sum of the heat conduction of the second copper electrode 3.2 and the heat conduction below the P-type thermoelectric semiconductor and the Peltier heat is equal, and the following conditions are satisfied:
wherein H is 1 +H 2 The first contact surface B and the second contact surface F are shown in height;
(2) The temperature of the first contact surface C and the second contact surface E of the P-type thermoelectric semiconductor and the first copper electrode 3.1 are the same, and the following conditions are satisfied:
the sum of the heat conduction of the first copper electrode 3.1 and the heat conduction above the P-type thermoelectric semiconductor and the Peltier heat is equal, and the following conditions are satisfied:
wherein H is 1 +H 2 +H 3 The representation represents the C, E plane height;
(3) Regarding the boundary conditions of the respective wall surfaces, the current boundary conditions are satisfied, that is, the left end face J of the additional load R and the left end face a of the second copper electrode 3.2 are set to be grounded; the right end face I of the applied load R is arranged in electrical contact with the right end face G of the second copper electrode 3.3.
Step three, as shown in fig. 3, a Z-type thermoelectric device and a method for determining parameters thereof, which calculate based on a thermal resistance network according to a thermal equilibrium equation and boundary conditionsHot side temperature T of thermoelectric semiconductor h And cold end temperature T c The method comprises the steps of carrying out a first treatment on the surface of the Because the heat conductivity of the copper electrode is higher, the temperature change in the heat conduction process of the copper electrode, namely the temperature T of the hot end of the thermoelectric semiconductor, is ignored h And cold end temperature T c Equal to the surface temperature of the corresponding copper electrode; the method specifically comprises the following steps:
(1) Setting k as the iteration number, s representingIs the value of delta s, delta s is the change value of P-type thermoelectric semiconductor or N-type thermoelectric semiconductor during each iteration calculation, delta s is the value of delta s, delta s is the change value of delta s>
(2) When k=0, it willThe initial value is set as s 0 And each cycle s k ＝s k-1 +Δs；
(3) Order thep k Represents the output power, P, of a traditional symmetrical thermoelectric device after iterating k times z Representing the output power of the Z-type device;
(4) When k=0, if Δp 0 K=k+1, updating s k ＝s k-1 +Δs is re-substituted into the calculation of the new output power until Δp after k cycles k > 0, exit the loop and preserve the last result s k Meter a=s k 。
Step four, determining the optimal length of the fine copper, and the result is shown in fig. 4, wherein the specific steps are as follows:
(1) Setting the value of the step length Deltal to enable
(2) The output power of the corresponding Z-type thermoelectric device when i=0 and i_1 is recorded as P respectively 0 And P 1 ；
(3) Judging P 0 And P 1 If P 0 ＜P 1 I=i+1, updating the fine copper length and substituting the next round of output power P i Up to p i ＞p i+1 Exiting the cycle; otherwise, updating the fine copper length to L 2 -ix Δl and substituting the next round of output power P i Up to p i ＞p i+1 And (3) exiting the cycle, reserving the value of the last time i, and calculating the length of the fine copper at the moment, namely the final determined length of the fine copper.
Step five, the model is as in fig. 5, and θ when the output power is maximum is determined:
(1) The P-type thermoelectric semiconductor has unchanged height, and the included angle theta between the copper electrode and the fine copper is changed. Taking the influence of space occupancy and the distance between adjacent conductors into consideration, and taking theta epsilon 45, 90;
(2) Setting an initial angle theta 0 Setting a change value delta theta=1° of the included angle; let θ=θ 0 -j x Δθ, where j = 0,1,2, …,45; calculating the output power of the Z-type thermoelectric device when j takes different values; and comparing the output power under different included angles theta, and taking the value theta when the output power is maximum, namely the finally determined optimal included angle theta.
Examples:
the thermoelectric semiconductor materials used for the conventional PN-type thermoelectric device and the Z-type thermoelectric device for comparison in this example are BiSbTeSe-based materials, and thermoelectric material parameters of BiSbTeSe-based P-type thermoelectric semiconductor, N-type thermoelectric semiconductor, and copper conductor are listed in tables 1 and 2, respectively:
TABLE 1 thermoelectric material parameters of BiSbTeSe-based P-type thermoelectric semiconductor and N-type thermoelectric semiconductor
It can be seen from table 1 that thermoelectric material parameters of the BiSbTeSe-based P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor are parameters related to temperature T, wherein: t taking down the bottom temperature T c And upper top surface temperature T h Since the thermoelectric figure of merit is closely related to the seebeck coefficient, the thermal conductivity, and the electrical conductivity, the present invention selects which of the two should be replaced by fine copper according to the thermoelectric figure of merit corresponding to a certain temperature T.
TABLE 2 conventional PN junction dimension parameters and other parameters
Table 2 provides dimensional references for the dimensional parameters of conventional PN junction symmetric thermoelectric devices, for example, the Z-type thermoelectric semiconductor dimensions and other parameters for which the geometry dimensions are selected as examples of single P-type thermoelectric semiconductors.
TABLE 3Z-type thermoelectric semiconductor dimension parameters and other parameters for the example of a single P-type thermoelectric semiconductor
Table 3 gives the Z-type thermoelectric semiconductor dimension parameters and other parameters for the example of a single P-type thermoelectric semiconductor, providing data support for calculation of the thermal resistance network and calculation of the output power.

Claims (10)

1. The Z-shaped thermoelectric device is characterized by comprising an upper ceramic plate (1), a lower ceramic plate (1'), a thermoelectric semiconductor (2), a first copper electrode (3.1), a second copper electrode (3.2), a third copper electrode (3.3) and a conductor (4);
the bottom surface of the upper ceramic plate (1) is connected with the upper end surface of a first copper electrode (3.1), one side of the lower end surface of the first copper electrode (3.1) is connected with the upper end surface of the thermoelectric semiconductor (2), and the other side of the lower end surface of the first copper electrode (3.1) is connected with the upper end surface of the conductor (4);
the lower end face of the thermoelectric semiconductor (2) is connected with the upper end face of the second copper electrode (3.2), and the lower end face of the conductor (4) is connected with the upper end face of the third copper electrode (3.3);
the lower end face of the second copper electrode (3.2) and the lower end face of the third copper electrode (3.3) are respectively connected with two sides of the top face of the lower ceramic plate (1').
2. A Z-type thermoelectric device according to claim 1, wherein: the first copper electrode (3.1) and the conductor (4) form a certain included angle theta, and the theta is 45 and 90.
3. The Z-type thermoelectric device according to claim 1, wherein: the conductor (4) is a fine copper conductor.
4. The Z-type thermoelectric device according to claim 1, wherein: the thermoelectric semiconductor (2) is a P-type thermoelectric semiconductor or an N-type thermoelectric semiconductor, and one of the P-type semiconductor and the N-type semiconductor having a larger thermoelectric figure of merit is used as the thermoelectric semiconductor (2).
5. The Z-type thermoelectric device according to claim 4, wherein: the thermoelectric semiconductor is composed of P-type thermoelectric semiconductor and N-type thermoelectric semiconductor, and has thermoelectric figure of merit Z p 、Z n Determining and judging Z p And Z n Is a size relationship of (a):
if Z p >Z n A fine copper conductor is adopted to replace an N-type thermoelectric semiconductor;
if Z p <Z n A fine copper conductor is adopted to replace a P-type thermoelectric semiconductor;
if Z p ＝Z n The Z-type thermoelectric device has the same performance as the traditional symmetrical thermoelectric device, and a thin copper conductor is not required to replace a P-type thermoelectric semiconductor or an N-type thermoelectric semiconductor.
6. The Z-type thermoelectric device according to claim 5, wherein: z is Z p >Z n When the thin copper conductor is adopted to replace an N-type thermoelectric semiconductor, the structural parameters of the Z-type thermoelectric device are determined: the Seebeck coefficient, the output power of the traditional symmetrical thermoelectric device, the output power of the Z-type thermoelectric device, the optimal fine copper length and the included angle theta parameter comprise the following steps:
s1: based on thermal resistance network, meterCalculating the hot end temperature T of the thermoelectric semiconductor (2) h And cold end temperature T c Temperature T at the hot end of the thermoelectric semiconductor (2) h And cold end temperature T c Equal to the surface temperature of the corresponding copper electrode;
s2: respectively calculating the output power P of the traditional symmetrical thermoelectric device pn Output power P of Z-type thermoelectric device z ；
S3: judging 1/2P pn And P z Determining the magnitude relation of the Z-type thermoelectric deviceConditions, wherein: s is S p 、S n Seebeck coefficients respectively representing the P-type thermoelectric semiconductor and the N-type thermoelectric semiconductor;
s4: determining the length of the thin copper conductor;
s5: and determining an included angle theta.
7. The Z-type thermoelectric device according to claim 6, wherein:
determining the use condition of the Z-type thermoelectric device, comprising the following steps:
step 1: determining the output power P of a conventional symmetrical thermoelectric device pn And output power P of Z-type thermoelectric device z The effective thermoelectric semiconductor cross-sectional area of the Z-shaped thermoelectric device is half that of a traditional symmetrical thermoelectric device, and the ratio is 1/2P pn And P z Calculates 1/2P pn ＝P z When (1)Setting critical value +.>
Step 2: by determining when a thermoelectric device is selectedAnd aThe magnitude relation determines which thermoelectric device is adopted; if it isThen a conventional symmetrical thermoelectric device is employed; if->Then a Z-type thermoelectric device is employed; if->The Z-type thermoelectric device has the same performance as the traditional symmetrical thermoelectric device, and both thermoelectric devices can be used.
8. The Z-type thermoelectric device according to claim 6, wherein:
determining an optimal length of a thin copper conductor of a Z-type thermoelectric device, comprising the steps of:
(i) The method comprises the following steps Setting the value of the step length Deltal to enable
(ii) The method comprises the following steps The output power of the corresponding Z-type thermoelectric device when i=0 and i_1 is recorded as P respectively 0 And P 1 ；
(iii) The method comprises the following steps Judging P 0 And P 1 If P 0 <P 1 I=i+1, updating the fine copper length and substituting the next round of output power P i Up to p i ＞p i+1 Exiting the cycle; otherwise, updating the fine copper length to L 2 -ix Δl and substituting the next round of output power P i Up to p i ＞p i+1 And (3) exiting the cycle, reserving the value of the last time i, and calculating the length of the fine copper at the moment, namely the final determined length of the fine copper.
9. The Z-type thermoelectric device according to claim 6, wherein: determining an included angle theta when the maximum output power of the Z-type thermoelectric device is determined, and considering the influence caused by space occupancy and the distance between adjacent conductors, the included angle theta is E [45, 90], comprising the following steps:
a1: setting an initial angle theta 0 Setting a change value delta theta=1° of the included angle; let θ=θ 0 -j x Δθ, where j = 0,1,2, …,45;
a2: calculating the output power of the Z-type thermoelectric device when j takes different values;
a3: and comparing the output power under different included angles theta, and taking the value theta when the output power is maximum, namely the finally determined optimal included angle theta.
10. The Z-type thermoelectric device according to claim 6, wherein: determining a calculation method and boundary conditions required by calculating the output power, wherein the calculation method adopts a numerical discrete method, and the boundary conditions comprise a temperature boundary condition and a current boundary condition;
the temperature boundary conditions are: the P-type thermoelectric semiconductor and the fine copper conductor are arranged to be insulated from the external environment, and the temperature of the lower bottom surface is arranged to be T c The upper top surface temperature is set to be, h in addition, the following:
the temperature at the first contact surface (B) and the second contact surface (F) of the P-type thermoelectric semiconductor and the second copper electrode (3.2) is the same, namelyThe heat conduction of the second copper electrode (3.2) is equal to the sum of the heat conduction under the P-type thermoelectric semiconductor and the Peltier heat, and the heat conduction is +.>Wherein: z is the height of the first contact surface (B) and the second contact surface (F);
the temperature of the first contact surface (C) and the second contact surface (E) of the P-type thermoelectric semiconductor and the first copper electrode (3.1) are the same,the sum of the heat conduction of the first copper electrode (3.1) and the Peltier heat of the P-type thermoelectric semiconductor Fang DaoreEqual (I)>Wherein: z is the height of the first contact surface (C) and the second contact surface (E);
the current boundary conditions are: the left end face (J) of the external load R and the left end face (A) of the second copper electrode (3.2) are grounded; the right end face (I) of the external load R is arranged in electrical contact with the right end face (G) of the third copper electrode (3.3).
CN202310255954.6A 2023-03-16 2023-03-16 Z-type thermoelectric device and parameter optimization method thereof Pending CN116456798A (en)

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