CN114398792B - Lithium ion battery pack thermal performance analysis method based on liquid-vapor cooling system - Google Patents

Lithium ion battery pack thermal performance analysis method based on liquid-vapor cooling system Download PDF

Info

Publication number
CN114398792B
CN114398792B CN202210058586.1A CN202210058586A CN114398792B CN 114398792 B CN114398792 B CN 114398792B CN 202210058586 A CN202210058586 A CN 202210058586A CN 114398792 B CN114398792 B CN 114398792B
Authority
CN
China
Prior art keywords
liquid
lithium ion
battery pack
cooling system
porous electrode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202210058586.1A
Other languages
Chinese (zh)
Other versions
CN114398792A (en
Inventor
汪秋婷
沈国瑜
李洪波
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Zhejiang Blue Box Aviation Technology Co ltd
Original Assignee
Zhejiang Blue Box Aviation Technology Co ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zhejiang Blue Box Aviation Technology Co ltd filed Critical Zhejiang Blue Box Aviation Technology Co ltd
Priority to CN202210058586.1A priority Critical patent/CN114398792B/en
Publication of CN114398792A publication Critical patent/CN114398792A/en
Application granted granted Critical
Publication of CN114398792B publication Critical patent/CN114398792B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/08—Thermal analysis or thermal optimisation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Data Mining & Analysis (AREA)
  • General Engineering & Computer Science (AREA)
  • Secondary Cells (AREA)
  • Software Systems (AREA)
  • Pure & Applied Mathematics (AREA)
  • Databases & Information Systems (AREA)
  • Computational Mathematics (AREA)
  • Mathematical Optimization (AREA)
  • Algebra (AREA)
  • Computer Hardware Design (AREA)
  • Evolutionary Computation (AREA)
  • Geometry (AREA)
  • Mathematical Analysis (AREA)

Abstract

The invention relates to a lithium ion battery pack thermal performance analysis method based on a liquid-vapor cooling system, which comprises the following steps: in the cooling system, the liquid coolant in the coolant supply pool is evaporated into steam or cooled into liquid according to the heat of the battery pack; establishing a one-dimensional electrochemical model; and establishing a three-dimensional heat conduction model. The invention has the beneficial effects that: the invention provides a novel closed loop type circulating cooling system which combines a liquid cooling pool and a steam cooling pool and is suitable for a pure electric vehicle/hybrid electric vehicle; the system combines a liquid coolant and a vapor coolant; the system of the present invention is used for battery thermal performance management; the invention also sets model parameters and operation parameters based on the miniaturized structure of the lithium ion battery pack, performs thermal performance analysis, and compares the thermal performance with the performance of the traditional liquid cooling system; the invention also designs a miniaturized structure of the lithium ion battery pack, and compared with the traditional radius interval design, the novel structure can obtain higher maximum temperature and average temperature.

Description

Lithium ion battery pack thermal performance analysis method based on liquid-vapor cooling system
Technical Field
The invention belongs to the technical field of battery cooling, and particularly relates to a lithium ion battery pack thermal performance analysis method based on a liquid-vapor cooling system.
Background
Battery Cooling Systems (BCSs) maintain the operating temperature of the lithium ion battery below a set operating temperature or within a set operating temperature range. Lithium ion battery internal resistance is one of the main heat sources, and high temperature operation causes battery capacity fading, thermal runaway and electrolyte explosion. When the temperature of the battery is reduced to be within the optimal working temperature range, the internal resistance of the lithium ion battery is increased.
Currently, BCSs can be classified according to various criteria, such as the working principle or the cooling liquid phase, whether there is direct contact between the cooling liquid and the lithium ion battery, and the like. BCS can also be classified according to the material of the coolant, and most literature generalizes common classification methods to liquid-based, gas-based, and Phase Change Material (PCM) based. Another classification of BCSs is based on power-assisted active control systems and power-assisted passive control systems. The liquid BCS-based system is an active control system, the PCM-based BCS system is a passive system, and the gas BCS-based system can be an active system or a passive system.
PCM-based BCSs utilize cooling loads to achieve cooling (constant temperature or in a constant temperature range), which achieves higher package temperature uniformity than liquid-based and air-based systems. However, PCM-based BCS suffers from the following disadvantages: the volume of the material changes and the heat conductivity coefficient changes in the phase change process.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a lithium ion battery pack thermal performance analysis method based on a liquid-vapor cooling system.
The lithium ion battery pack thermal performance analysis method based on the liquid-vapor cooling system comprises the following steps:
step 1, in a cooling system, evaporating liquid coolant in a coolant supply pool into steam or cooling the steam into liquid according to the heat of a battery pack; the condensation wall condenses the steam into liquid and recovers the liquid to the coolant supply tank;
step 2, establishing a one-dimensional electrochemical model, wherein the one-dimensional electrochemical model comprises a liquid-phase porous electrode, a solid matrix and boundary conditions; calculating the change of the lithium ion concentration on the liquid-phase porous electrode along with time, the apparent current density, the potential, the boundary condition and the potential through a one-dimensional electrochemical model; calculating apparent current density, potential, boundary conditions and potential on the solid-phase porous electrode; calculating the electron conductivity, lithium ion concentration and diffusion coefficient of lithium ions on the solid substrate; simulating the behavior and performance of a liquid-vapor coolant-based closed loop circulating cooling system in the lithium ion battery pack;
step 3, establishing a three-dimensional heat conduction model, and calculating the heat generation rate, the radial heat conductivity coefficient, the axial heat conductivity coefficient and the specific heat capacity of the lithium ion battery according to an energy rate balance equation;
and 4, step 4: establishing a mass flow model to describe the thermal performance of the liquid-vapor coolant-based closed loop circulating cooling system, the mass flow model including a mass flow equation for the coolant expressed by equation (16), a momentum transfer equation expressed by equation (17), and an energy flow equation expressed by equation (18);
Figure BDA0003465267090000021
Figure BDA0003465267090000022
Figure BDA0003465267090000023
in the above formula, the first and second carbon atoms are,
Figure BDA0003465267090000024
is the flow velocity, P is the pressure, g is the gravitational constant, ρ is the refrigerant density, c p Is the specific heat capacity, T is the temperature, and k is the thermal conductivity;
step 5, setting model parameters and operation parameters, and carrying out thermal performance analysis on the lithium ion battery pack based on the liquid-vapor cooling system: setting the heat conductivity coefficient of the lithium ion battery, the type of the selected coolant and the type of the selected refrigerant; the influence of the cell spacing and the height of the liquid cooling pool and the vapor cooling pool on the maximum temperature of the battery pack was verified.
Preferably, the cooling system in step 1 comprises: a battery pack, a coolant supply tank, liquid and vapor cooling tanks, a condensation wall, and a vapor portion; the battery pack has a lithium ion battery pack miniaturized structure, all batteries in the battery pack are arranged in a rectangular shape, 2 spacing distances are kept among single batteries, and the length of 1 spacing distance is equal to the radius of a cylindrical battery; the battery pack is positioned above the liquid cooling pool and the steam cooling pool, the coolant supply pool is connected with the liquid cooling pool and the steam cooling pool, and the steam part is a space where gas in the cooling system is located; the condensation wall is the inner wall of the arc top of the cooling system; the coolant supply reservoir contains a liquid coolant and a vapor coolant.
Preferably, the cells in the battery pack are connected in series and then in parallel.
Preferably, the battery pack is a 18650 type cylindrical lithium ion battery.
Preferably, the step 2 specifically comprises the following steps:
step 2-1, the formula of the change of the lithium ion concentration of the liquid-phase porous electrode in the one-dimensional electrochemical model along with time is as follows:
Figure BDA0003465267090000025
in the above formula, b s Is the concentration of lithium ions in the liquid-phase porous electrode; t is time; epsilon is the volume fraction;
Figure BDA0003465267090000031
is a gradient operator; d s Is the salt diffusion coefficient; a is the interface area; j is a function of n The hole wall flux of the lithium ion is obtained;
Figure BDA0003465267090000032
represents the positive time zero; i all right angle 2 Is the apparent current density; subscript + and subscript-represent positive and negative electrodes, respectively; f is a Faraday constant and takes the value of 96487C/mol;
step 2-2, calculating the apparent current density i of the liquid phase porous electrode 2 And apparent current density i of solid-phase porous electrode 1 (ii) a Aj in formula (1) n Apparent current density i with liquid phase porous electrode 2 The relation of (A) is as follows:
Figure BDA0003465267090000033
Figure BDA0003465267090000034
in the above formula, k is the ionic conductivity of the electrolyte, phi 2 Is liquid phase porous electrode potential, R is general gas constant, T is temperature value, F is Faraday constant, F is activity coefficient ± Representing the activity coefficients of the positive electrode and the negative electrode;
calculating the apparent current density i of the solid-phase porous electrode 1 ：
Figure BDA0003465267090000035
In the above formula, phi 1 Is the solid phase porous electrode potential, σ is the electron conductivity of the solid matrix;
step 2-3, calculating the lithium ion concentration in the solid matrix of the electrode:
Figure BDA0003465267090000036
in the above formula, b Li Is the concentration of lithium ions in the solid matrix of the electrode; t is time; d Li Is the diffusion coefficient of lithium ions through the solid matrix of the electrode; r is the lithium ion radius;
step 2-4, establishing boundary conditions of the anode and the cathode, and calculating the conversion current density i 0 ；
The positive electrode and negative electrode correlation formula based on the Butler-Volmer kinetic expression is as follows:
Figure BDA0003465267090000037
in the above formula, j n The hole wall flux of the lithium ion is obtained; h is a transition system of different materialsCounting; b is a mixture of s Is the concentration of lithium ions in the liquid-phase porous electrode; b i Is the salt concentration in the ith layer; b Li Is the concentration of lithium ions in the electrode solid matrix; eta is the electrode potential; v oc Is an open circuit voltage;
calculating the lithium ion concentration conversion current density i 0 ：
i 0 ＝FH(b s ) 0.5 (b i -b Li ) 0.5 (b Li ) 0.5 (7)
2-5, establishing boundary conditions of the solid-phase porous electrode and the liquid-phase porous electrode:
Figure BDA0003465267090000041
in the above formula, the potential calculation formula of the solid-phase porous electrode and the liquid-phase porous electrode is:
η＝φ 1 -φ 2 (9)
in the above formula, phi 1 And phi 2 The potentials of the solid-phase porous electrode and the liquid-phase porous electrode are respectively represented.
Preferably, step 3 specifically comprises the following steps:
step 3-1, establishing an energy rate balance equation, wherein the three-dimensional temperature distribution of the battery at any time point t is expressed as follows through the energy rate balance equation:
Figure BDA0003465267090000042
in the above formula, x, y and z are coordinate axes of a three-dimensional coordinate system, i, j and k are imaginary parameters of a complex expression, and k is b Is the thermal conductivity, T, of the battery b Is the temperature of the battery, p b Is the density of the battery, c p,b Is the specific heat capacity of the battery, and t is time; the subscript b represents a battery cell and,
Figure BDA0003465267090000043
represents the heat dissipation rate of the BCS; according to heat source volumeRate of heat generation
Figure BDA0003465267090000044
The method is divided into two parts:
Figure BDA0003465267090000045
in the above formula, the first and second carbon atoms are,
Figure BDA0003465267090000046
indicating the volumetric heat generation rate of the cell due to the internal resistance of the current,
Figure BDA0003465267090000047
represents the volumetric heat generation rate of the battery generated by the chemical reaction inside the battery;
step 3-2, the calculation formula of the radial heat conductivity coefficient and the axial heat conductivity coefficient is
Figure BDA0003465267090000051
Figure BDA0003465267090000052
In the above formula, k r Is the radial coefficient of thermal conductivity, h is the height of the cell, L i Denotes the thickness, k, of the ith layer i Denotes the thermal conductivity, k, of the i-th layer a Axial thermal conductivity;
3-3, establishing an effective part calculation formula of the total specific heat capacity:
Figure BDA0003465267090000053
in the above formula, c p The effective part of the total specific heat capacity is cp, i is the specific heat capacity of the ith layer; the total mass density of the effective components of the battery is calculated by the following formula:
Figure BDA0003465267090000054
in the above formula, ρ i Is the ith layer density and the thickness is expressed as L i 。
The invention has the beneficial effects that: the invention provides a novel closed loop type circulating cooling system which combines a liquid cooling pool and a steam cooling pool and is suitable for a pure electric vehicle/hybrid electric vehicle; the system combines a liquid coolant and a vapor coolant; the system of the present invention is used for battery thermal performance management; the invention also sets model parameters and operating parameters based on the lithium ion battery pack miniaturized structure, performs thermal performance analysis, and compares the thermal performance with the performance of the traditional liquid cooling system.
The invention also designs a miniaturized structure of the lithium ion battery pack, and compared with the traditional radius interval design, the new structure can obtain higher maximum temperature and average temperature; the invention combines the lithium ion battery miniaturized structure and the liquid-vapor closed loop type circulating cooling system, and the temperature variation range in the high-strength circulation is kept within 4 ℃ and the highest temperature is kept within 35 ℃ in 80 percent of the circulation time period.
Drawings
FIG. 1 is a three-dimensional model diagram of a novel cooling system based on a liquid-vapor cooling pool;
FIG. 2-1 is a graph of maximum temperature of a lithium ion battery as a function of charge and discharge time for a 20% liquid refrigerant cell coverage;
fig. 2-2 is a graph of maximum temperature of a lithium ion battery as a function of charge and discharge time with 40% coverage of the liquid refrigerant battery;
FIGS. 2-3 are graphs of maximum temperature of a lithium ion battery as a function of charge and discharge time for a liquid refrigerant battery coverage of 80%;
fig. 3 is a graph of the difference between the heat absorbed by the liquid pool, the heat absorbed by the vapor, and the total heat removed for the miniaturized design and the radius-spaced design.
Description of reference numerals: battery 1, coolant supply tank 2, liquid cooling tank and vapor cooling tank 3, condensation wall 4, vapor portion 5.
Detailed Description
The present invention will be further described with reference to the following examples. The following examples are set forth merely to provide an understanding of the invention. It should be noted that, for a person skilled in the art, several modifications can be made to the invention without departing from the principle of the invention, and these modifications and modifications also fall within the protection scope of the claims of the present invention.
Example one
The first embodiment of the present application provides a liquid-vapor cooling system as shown in fig. 1, including: a battery pack 1, a coolant supply tank 2, a liquid cooling tank and vapor cooling tank 3, a condensation wall 4, and a vapor portion 5; the battery pack 1 is provided with a lithium ion battery pack miniaturization structure, all batteries in the battery pack 1 are arranged in a rectangular shape, 2 spacing distances are kept among single batteries, and the length of 1 spacing distance is equal to the radius of a cylindrical battery; the battery pack 1 is positioned above the liquid cooling pool and the steam cooling pool 3, the coolant supply pool 2 is connected with the liquid cooling pool and the steam cooling pool 3, and the steam part 5 is a space where gas in a cooling system is located; the condensation wall 4 is the inner wall of the arc top of the cooling system; the coolant supply tank 2 contains liquid coolant and vapor coolant. The batteries in the battery pack 1 are connected in series and then in parallel.
Example two
On the basis of the first embodiment, the second embodiment of the present application provides a method for analyzing thermal performance of a lithium ion battery pack based on the liquid-vapor cooling system in the first embodiment:
step 1, in a cooling system, evaporating liquid coolant in a coolant supply pool 2 into steam or cooling the steam into liquid according to the heat of a battery pack 1; the condensation wall 4 condenses the vapor into liquid and returns it to the coolant supply tank 2;
step 2, establishing a one-dimensional electrochemical model, wherein the one-dimensional electrochemical model comprises a liquid-phase porous electrode, a solid matrix and boundary conditions; calculating the change of the lithium ion concentration on the liquid-phase porous electrode along with time, the apparent current density, the potential, the boundary condition and the potential through a one-dimensional electrochemical model; calculating apparent current density, potential, boundary conditions and potential on the solid-phase porous electrode; calculating the electron conductivity, the lithium ion concentration and the diffusion coefficient of lithium ions on the solid substrate; simulating the behavior and performance of a liquid-vapor coolant-based closed loop circulating cooling system in the lithium ion battery pack;
step 2-1, the formula of the change of the lithium ion concentration of the liquid-phase porous electrode in the one-dimensional electrochemical model along with time is as follows:
Figure BDA0003465267090000071
in the above formula, b s Is the concentration of lithium ions in the liquid-phase porous electrode; t is time; epsilon is the volume fraction;
Figure BDA0003465267090000072
is a gradient operator; d s Is the salt diffusion coefficient; a is the interface area; j is a function of n The hole wall flux of the lithium ion is obtained;
Figure BDA0003465267090000073
represents the positive time zero; i.e. i 2 Is the apparent current density; subscript + and subscript-represent positive and negative electrodes, respectively; f is a Faraday constant and takes the value of 96487C/mol;
step 2-2, calculating the apparent current density i of the liquid phase porous electrode 2 And apparent current density i of solid-phase porous electrode 1 (ii) a Aj in formula (1) n Apparent current density i with liquid phase porous electrode 2 The relation of (A) is as follows:
Figure BDA0003465267090000074
Figure BDA0003465267090000075
in the above formula, k is the ionic conductivity of the electrolyte, phi 2 Is liquid phase porous electrode potential, R is general gas constant, T is temperature value, F is Faraday constant, and F is activity systemNumber f ± Representing the activity coefficients of the positive electrode and the negative electrode;
calculating the apparent current density i of the solid-phase porous electrode 1 ：
Figure BDA0003465267090000076
In the above formula, phi 1 Is the solid phase porous electrode potential, σ is the electron conductivity of the solid matrix;
step 2-3, calculating the lithium ion concentration in the solid matrix of the electrode:
Figure BDA0003465267090000077
in the above formula, b Li Is the concentration of lithium ions in the solid matrix of the electrode; t is time; d Li Is the diffusion coefficient of lithium ions through the solid matrix of the electrode; r is the lithium ion radius;
2-4, establishing boundary conditions of the anode and the cathode, and calculating the conversion current density i 0 ；
The correlation formula of the anode and the cathode of the electrode based on the Butler-Volmer kinetic expression is as follows:
Figure BDA0003465267090000078
in the above formula, j n The hole wall flux of the lithium ion is obtained; h is the conversion coefficient of the different materials; b s Is the concentration of lithium ions in the liquid-phase porous electrode; b i Is the salt concentration in the i-th layer; b Li Is the concentration of lithium ions in the electrode solid matrix; eta is the electrode potential; v oc Is an open circuit voltage;
calculating the lithium ion concentration conversion current density i 0 ：
i 0 ＝FH(b s ) 0.5 (b i -b Li ) 0.5 (b Li ) 0.5 (7)
2-5, establishing boundary conditions of the solid-phase porous electrode and the liquid-phase porous electrode:
Figure BDA0003465267090000081
in the above formula, the potential calculation formula of the solid-phase porous electrode and the liquid-phase porous electrode is:
η＝φ 1 -φ 2 (9)
in the above formula, phi 1 And phi 2 Respectively representing the electric potentials of the solid-phase porous electrode and the liquid-phase porous electrode;
step 3, establishing a three-dimensional heat conduction model, and calculating the heat generation rate, the radial heat conductivity coefficient, the axial heat conductivity coefficient and the specific heat capacity of the lithium ion battery according to an energy rate balance equation;
step 3-1, establishing an energy rate balance equation, wherein the three-dimensional temperature distribution of the battery at any time point t is expressed as follows through the energy rate balance equation:
Figure BDA0003465267090000082
in the above formula, x, y and z are all coordinate axes of a three-dimensional coordinate system, k b Is the thermal conductivity, T, of the battery b Is the temperature of the battery, p b Is the density of the battery, c p,b Is the specific heat capacity of the battery, and t is time; the subscript b represents the cell or cells,
Figure BDA0003465267090000087
the heat dissipation rate of the BCS is represented; heat generation rate by volume according to heat source
Figure BDA0003465267090000083
The method comprises the following two steps:
Figure BDA0003465267090000084
in the above formula, the first and second carbon atoms are,
Figure BDA0003465267090000085
indicating the volumetric heat generation rate of the cell due to the internal resistance of the current,
Figure BDA0003465267090000086
represents a heat generation rate of the battery generated by a chemical reaction inside the battery;
step 3-2, the calculation formula of the radial heat conductivity coefficient and the axial heat conductivity coefficient is
Figure BDA0003465267090000091
Figure BDA0003465267090000092
In the above formula, k r Is the radial coefficient of thermal conductivity, h is the height of the cell, L i Denotes the thickness, k, of the ith layer i Denotes the thermal conductivity, k, of the i-th layer a Axial thermal conductivity;
3-3, establishing an effective part calculation formula of the total specific heat capacity:
Figure BDA0003465267090000093
in the above formula, c p The effective part of the total specific heat capacity is cp, i is the specific heat capacity of the ith layer; the total mass density of the effective components of the battery is calculated by the following formula:
Figure BDA0003465267090000094
in the above formula, ρ i Is the ith layer density and the thickness is expressed as L i ；
And 4, step 4: establishing a mass flow model to describe the thermal performance of the liquid-vapor coolant-based closed loop circulating cooling system, the mass flow model including a mass flow equation for the coolant expressed by equation (16), a momentum transfer equation expressed by equation (17), and an energy flow equation expressed by equation (18);
Figure BDA0003465267090000095
Figure BDA0003465267090000096
Figure BDA0003465267090000097
in the above formula, the first and second carbon atoms are,
Figure BDA0003465267090000098
is the flow velocity, P is the pressure, g is the gravitational constant, ρ is the refrigerant density, c p Is the specific heat capacity, T is the temperature, and k is the thermal conductivity;
step 5, parameter setting and experiment setting: heat conductivity coefficient k of 18650 type lithium ion battery in the mixture of ethylene carbonate/dimethyl carbonate with the volume ratio of 1:2 0 The calculation formula is as follows,
Figure BDA0003465267090000101
in the formula, b s As the lithium ion concentration (mol/dm 3), the conductivity was in units of S/cm. The coolant of the present invention is R134a, and its thermophysical properties are shown in Table 1 below. The refrigerant used in the cooling system of the present invention is R134a. According to different charging and discharging cycles, the influence of the distance between the single batteries and the height of the liquid pool on the highest temperature of the battery pack is verified. The invention designs the charge-discharge cycle time to be 600s, and the charge is started from 300s at the discharge multiplying power of 6C,7C and 8C respectively, and the discharge is ended at 300 s.
TABLE 1 refrigerant R134a Performance Association tables from EES and COMSOL inlets
Parameter(s) Temperature range Equation of correlation
Coefficient of thermal conductivity 303-500 k(W/m.K)＝-1.86×10 -7 T 2 +0.0003T-0.0419
Density of 303-500 ρ(kg/m 3 )＝0.0002T 2 -0.3473T+114.21
Specific heat capacity 303-500 c p (J/kg.K)＝6×10 -6 T 2 -0.0036T+1.6002
Specific heat ratio 303-400 γ＝c p /c v ＝2×10 -5 T 2 -0.01212T+3.1468
Dynamic viscosity 303-400 μ(Pa.s)＝6×10 -8 T+8×10 -7
Experimental result 1:
fig. 2 is a graph showing the influence of changing design parameters and operation parameters on the maximum temperature of the lithium battery, where R represents the unit cell interval as a unit cell radius value, and 0.1R represents the unit cell interval as 10% of the cell radius value.
Fig. 2-1 shows that the maximum cell temperatures for the miniaturized structure design were 37.6C, 40.0C, and 42.9C, respectively, under the conditions of the charge magnifications of 6℃,7C, and 8C. The maximum temperature of the miniaturized cell structure is similar to that of the larger spacing cell structure when the liquid cell coverage is 20%. Under the condition that the charge-discharge multiplying power is 7C, the maximum temperature difference is 0.2 ℃. When the discharge rate is 6C, the maximum temperature difference between the miniaturized design and the large-interval design is small.
Fig. 2-2 shows the maximum temperature of the li-ion cell as a function of 600s cycles at 40% liquid cell coverage. Similar to the case of coverage of 20%, the maximum temperature difference between the two designs increases as the charge-discharge rate increases. For miniaturization design, when the liquid coverage is 40%, the cyclic charge mode is switched to the cyclic discharge mode, and the maximum temperature can be decreased by 0.8 ℃, 1.3 ℃ and 2.0 ℃ within 50s (the charge-discharge rates are 6C,7C and 8℃, respectively).
Fig. 2 to 3 show that the maximum temperature of the battery with the liquid coverage of 80% was reduced to 32.6C, 33.5C and 35.0C when the charging rates were 6℃,7C and 8C, respectively. When the liquid coverage was 60%, the temperature drop values increased to 1.0 ℃, 1.5 ℃ and 2.3 ℃.
Experimental results 2:
fig. 3 shows a graph of the difference between the heat absorbed by the liquid pool, the heat absorbed by the vapor and the total heat removed for the miniaturized design and the radius-spaced design. With 20% cell coverage, the difference between the two designs increases in liquid pool and vapor supply as the circulating current increases. Under the conditions that the charge and discharge multiplying power is 6C,7C and 8C respectively, the contribution result of the steam cooling effect on the total cold load is that the miniaturization design is smaller than the radius interval design. As shown in fig. 3, the difference in the steam cooling effect increases as the charge/discharge rate increases. However, in the miniaturized design, the cooling effect of the liquid pool is greater than that of the radial interval design, and the difference only increases with the increase of the charge-discharge rate.

Claims (5)

1. A lithium ion battery pack thermal performance analysis method based on a liquid-vapor cooling system is characterized by comprising the following steps:
step 1, in a cooling system, evaporating liquid coolant in a coolant supply pool (2) into steam or cooling into liquid according to the heat of a battery pack (1); the condensation wall (4) condenses the steam into liquid and recovers the liquid to the coolant supply tank (2);
step 2, establishing a one-dimensional electrochemical model, wherein the one-dimensional electrochemical model comprises a liquid-phase porous electrode, a solid matrix and boundary conditions; calculating the change of the lithium ion concentration on the liquid-phase porous electrode along with time, the apparent current density, the potential, the boundary condition and the potential through a one-dimensional electrochemical model; calculating apparent current density, potential, boundary conditions and potential on the solid-phase porous electrode; calculating the electron conductivity, the lithium ion concentration and the diffusion coefficient of lithium ions on the solid substrate; in particular, the method comprises the following steps of,
step 2-1, the formula of the change of the lithium ion concentration of the liquid-phase porous electrode in the one-dimensional electrochemical model along with time is as follows:
Figure FDA0003926613930000011
in the above formula, b s Is the concentration of lithium ions in the liquid-phase porous electrode; t is time; epsilon is the volume fraction;
Figure FDA0003926613930000012
is a gradient operator; d s Is the salt diffusion coefficient; a is the interface area; j is a function of n The hole wall flux of the lithium ion is obtained;
Figure FDA0003926613930000013
represents the positive time zero; i.e. i 2 Is the apparent current density; subscript + and subscript-represent positive and negative electrodes, respectively; f is a Faraday constant and takes the value of 96487C/mol;
step 2-2, calculating the apparent current density i of the liquid phase porous electrode 2 And solid phase polyApparent current density i of the pore electrode 1 (ii) a Aj in formula (1) n Apparent current density i with liquid phase porous electrode 2 The relation of (A) is as follows:
Figure FDA0003926613930000014
Figure FDA0003926613930000015
in the above formula, k is the ionic conductivity of the electrolyte, phi 2 Is liquid phase porous electrode potential, R is general gas constant, T is temperature value, F is Faraday constant, F is activity coefficient ± Representing the activity coefficients of the positive electrode and the negative electrode;
calculating the apparent current density i of the solid-phase porous electrode 1 ：
Figure FDA0003926613930000016
In the above formula, phi 1 Is the solid phase porous electrode potential, σ is the electron conductivity of the solid matrix;
step 2-3, calculating the lithium ion concentration in the solid matrix of the electrode:
Figure FDA0003926613930000021
in the above formula, b Li Is the concentration of lithium ions in the solid matrix of the electrode; t is time; d Li Is the diffusion coefficient of lithium ions through the solid matrix of the electrode; r is the lithium ion radius;
step 2-4, establishing boundary conditions of the anode and the cathode, and calculating the conversion current density i 0 ；
The positive electrode and negative electrode correlation formula based on the Butler-Volmer kinetic expression is as follows:
Figure FDA0003926613930000022
in the above formula, j n The hole wall flux of the lithium ion is obtained; h is the conversion coefficient of the different materials; b s Is the concentration of lithium ions in the liquid-phase porous electrode; b i Is the salt concentration in the i-th layer; b is a mixture of Li Is the concentration of lithium ions in the solid matrix of the electrode; eta is the electrode potential; v oc Is an open circuit voltage;
calculating the lithium ion concentration conversion current density i 0 ：
i 0 ＝FH(b s ) 0.5 (b i -b Li ) 0.5 (b Li ) 0.5 (7)
2-5, establishing boundary conditions of the solid-phase porous electrode and the liquid-phase porous electrode:
Figure FDA0003926613930000023
in the above formula, the potential calculation formula of the solid-phase porous electrode and the liquid-phase porous electrode is:
η＝φ 1 -φ 2 (9)
in the above formula, phi 1 And phi 2 Respectively representing the electric potentials of the solid-phase porous electrode and the liquid-phase porous electrode;
step 3, establishing a three-dimensional heat conduction model, and calculating the heat generation rate, the radial heat conductivity coefficient, the axial heat conductivity coefficient and the specific heat capacity of the lithium ion battery according to an energy rate balance equation;
and 4, step 4: establishing a mass flow model to describe the thermal performance of the liquid-vapor coolant-based closed loop circulating cooling system, the mass flow model including a mass flow equation for the coolant expressed by equation (16), a momentum transfer equation expressed by equation (17), and an energy flow equation expressed by equation (18);
Figure FDA0003926613930000024
Figure FDA0003926613930000031
Figure FDA0003926613930000032
in the above formula, the first and second carbon atoms are,
Figure FDA0003926613930000033
is the flow velocity, P is the pressure, g is the gravitational constant, ρ is the refrigerant density, c p Is the specific heat capacity, T is the temperature, and k is the thermal conductivity;
step 5, setting model parameters and operation parameters, and carrying out thermal performance analysis on the lithium ion battery pack based on the liquid-vapor cooling system: setting the heat conductivity coefficient, the selected coolant type and the selected refrigerant type of the lithium ion battery; the influence of the cell spacing and the height of the liquid cooling pool and the vapor cooling pool (3) on the maximum temperature of the battery pack was verified.
2. The method for analyzing the thermal performance of the lithium ion battery pack based on the liquid-vapor cooling system as claimed in claim 1, wherein the cooling system in the step 1 comprises: a battery pack (1), a coolant supply tank (2), a liquid cooling tank and a vapor cooling tank (3), a condensation wall (4), and a vapor portion (5); the battery pack (1) is provided with a lithium ion battery pack miniaturization structure, all batteries in the battery pack (1) are arranged in a rectangular shape, 2 spacing distances are kept among single batteries, and the length of 1 spacing distance is equal to the radius of a cylindrical battery; the battery pack (1) is positioned above the liquid cooling pool and the steam cooling pool (3), the coolant supply pool (2) is connected with the liquid cooling pool and the steam cooling pool (3), and the steam part (5) is a space where gas in a cooling system is located; the condensation wall (4) is the inner wall of the arc top of the cooling system; the coolant supply tank (2) contains a liquid coolant and a vapor coolant.
3. The method for analyzing the thermal performance of the lithium ion battery pack based on the liquid-vapor cooling system as claimed in claim 2, wherein: the batteries in the battery pack (1) are connected in series and then in parallel.
4. The method for analyzing the thermal performance of the lithium ion battery pack based on the liquid-vapor cooling system as claimed in claim 3, wherein: the battery pack (1) adopts a 18650 type cylindrical lithium ion battery.
5. The method for analyzing the thermal performance of the lithium ion battery pack based on the liquid-vapor cooling system as claimed in claim 1, wherein the step 3 comprises the following steps:
step 3-1, establishing an energy rate balance equation, wherein the three-dimensional temperature distribution of the battery at any time point t is expressed as follows through the energy rate balance equation:
Figure FDA0003926613930000034
in the above formula, x, y and z are coordinate axes of a three-dimensional coordinate system, i, j and k are imaginary parameters of a complex expression, and k is b Is the thermal conductivity, T, of the battery b Is the temperature of the battery, p b Is the density of the battery, c p,b Is the specific heat capacity of the battery, and t is time; the subscript b represents the cell or cells,
Figure FDA0003926613930000041
represents the heat dissipation rate of the BCS; generating heat according to volume of heat source
Figure FDA0003926613930000042
The method is divided into two parts:
Figure FDA0003926613930000043
in the above formula, the first and second carbon atoms are,
Figure FDA0003926613930000044
indicating the volumetric heat generation rate of the cell due to the internal resistance of the current,
Figure FDA0003926613930000045
represents the volumetric heat generation rate of the battery generated by the chemical reaction inside the battery;
step 3-2, the calculation formula of the radial heat conductivity coefficient and the axial heat conductivity coefficient is
Figure FDA0003926613930000046
Figure FDA0003926613930000047
In the above formula, k r Is the radial coefficient of thermal conductivity, h is the height of the cell, L i Denotes the thickness, k, of the ith layer i Denotes the thermal conductivity, k, of the i-th layer a Axial thermal conductivity;
3-3, establishing an effective part calculation formula of the total specific heat capacity:
Figure FDA0003926613930000048
in the above formula, c p An effective portion of the total specific heat capacity, c p,i Is the specific heat capacity of the ith layer; the total mass density of the effective components of the battery is calculated by the following formula:
Figure FDA0003926613930000049
in the above formula, ρ i Is the ith layer density and the thickness is expressed as L i 。
CN202210058586.1A 2022-01-11 2022-01-11 Lithium ion battery pack thermal performance analysis method based on liquid-vapor cooling system Active CN114398792B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210058586.1A CN114398792B (en) 2022-01-11 2022-01-11 Lithium ion battery pack thermal performance analysis method based on liquid-vapor cooling system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210058586.1A CN114398792B (en) 2022-01-11 2022-01-11 Lithium ion battery pack thermal performance analysis method based on liquid-vapor cooling system

Publications (2)

Publication Number Publication Date
CN114398792A CN114398792A (en) 2022-04-26
CN114398792B true CN114398792B (en) 2022-12-16

Family

ID=81230748

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210058586.1A Active CN114398792B (en) 2022-01-11 2022-01-11 Lithium ion battery pack thermal performance analysis method based on liquid-vapor cooling system

Country Status (1)

Country Link
CN (1) CN114398792B (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109033619A (en) * 2018-07-24 2018-12-18 浙江大学城市学院 A kind of transient temperature model modelling approach of 18650 type lithium battery discharge cycles
CN111460664A (en) * 2020-04-01 2020-07-28 吉林大学 Nonlinear cooling optimization method for new energy automobile power battery

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2974922B1 (en) * 2011-05-04 2013-04-26 IFP Energies Nouvelles OPTIMIZED METHOD FOR THE THERMAL MANAGEMENT OF AN ELECTROCHEMICAL STORAGE SYSTEM
CN108829929A (en) * 2018-05-09 2018-11-16 中国科学院宁波材料技术与工程研究所 A kind of method for building up and device of lithium ion battery needle thorn model
CN108984955A (en) * 2018-08-09 2018-12-11 江西江铃集团新能源汽车有限公司 Battery of electric vehicle packet temperature management analysis method

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109033619A (en) * 2018-07-24 2018-12-18 浙江大学城市学院 A kind of transient temperature model modelling approach of 18650 type lithium battery discharge cycles
CN111460664A (en) * 2020-04-01 2020-07-28 吉林大学 Nonlinear cooling optimization method for new energy automobile power battery

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
18650型锂电池放电过程的瞬态热模型与电压模拟;汪秋婷等;《科技通报》;20200229(第02期);49-53 *
Porous-Electrode Theory with Battery Applications;JOHN NEWMAN等;《JOURNAL REVIEW》;19750131;25-41 *
State of Health Estimation for Lithium-ion Battery Based on D-UKF;Wang Qiuting等;《International Journal of Hybrid Information Technology》;20151231;第9卷(第7期);55-70 *
三维锂离子单电池电化学-热耦合模型;张立军等;《电源技术》;20160720(第07期);31-35+159 *
锂离子电池组气体散热结构设计与仿真;马强等;《电源技术》;20200920(第09期);26-31 *

Also Published As

Publication number Publication date
CN114398792A (en) 2022-04-26

Similar Documents

Publication Publication Date Title
Gao et al. Thermodynamic understanding of Li-dendrite formation
Rao et al. Experimental investigation on thermal management of electric vehicle battery with heat pipe
Wang et al. Heat transfer in the dynamic cycling of lithium–titanate batteries
Huo et al. Investigation of power battery thermal management by using mini-channel cold plate
Wang et al. Molecular design of a metal–organic framework material rich in fluorine as an interface layer for high-performance solid-state Li metal batteries
Choudhury et al. Engineering current collectors for batteries with high specific energy
CN110676420A (en) Lithium ion battery's lithium diaphragm of mending
Muñoz-Torrero et al. A critical perspective on rechargeable Al-ion battery technology
CN112750982A (en) Laminated lithium metal battery negative electrode material, preparation method thereof and lithium metal secondary battery
Yang et al. Calendering effect on the electrochemical performances of the thick Li-ion battery electrodes using a three dimensional Ni alloy foam current collector
Guo et al. Battery thermal management system with heat pipe considering battery aging effect
CN115072703B (en) Composite anode material and preparation method and application thereof
Yang et al. Capacity fade characteristics of lithium iron phosphate cell during dynamic cycle
Ren et al. Thermal issues of vanadium redox flow batteries
CN113488110B (en) Electrochemical-thermal coupling model and high-capacity lithium battery simulation method based on model
CN114398792B (en) Lithium ion battery pack thermal performance analysis method based on liquid-vapor cooling system
Zhang et al. Effects of air cooling structure on cooling performance enhancement of prismatic lithium‐ion battery packs based on coupled electrochemical‐thermal model
CN113493911B (en) Method for forming corrosion-resistant coating, corrosion-resistant member having corrosion-resistant coating formed thereon, heat exchanger, and fuel cell system
Wu et al. Combining Janus Separator and Organic Cathode for Dendrite‐Free and High‐Performance Na‐Organic Batteries
Das et al. Impact of electrode surface/volume ratio on Li-ion battery performance
Guo et al. Preface: Special Topic on Rechargeable Battery Technology
Murashko et al. Optimization of the passive thermal control system of a lithium-ion battery with heat pipes embedded in an aluminum plate
Burheim et al. Thermal gradients and thermal conductivity in PEM fuel cells, compared to li-ion batteries and super capacitors
US20150050529A1 (en) Elevated Temperature Li/Metal Battery System
Ndokaj et al. Performance of Gaensel Energy Group's Nikel Storage Cells: Case Study

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant