Method for testing anisotropic heat diffusion coefficient of power battery at same time

A technology of thermal diffusivity and power battery, applied in the direction of material thermal conductivity, material thermal development, etc., can solve the problems of large influence of test accuracy calculation model, poor recognition parameter accuracy, and inaccurate simulation model, so as to save the cumbersome process , the effect of improving accuracy and reliability

Active Publication Date: 2016-10-26
CHINA FIRST AUTOMOBILE
3 Cites 5 Cited by

AI-Extracted Technical Summary

Problems solved by technology

The transient method has a short test cycle and simple test equipment structure, but for anisotropic substances, only the specific heat capacity and thermal diffusivity in one direction can be tested first, and then the thermal diffusivity in other directions can be calculated through calculation. The test accuracy is greatly affected by the calculation model. Big
Power batteries have anisotropic heat transfer characteristics due to the diversity of composition materials and str...
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Method used

The method for testing power battery anisotropic thermal diffusivity of the present invention can draw anisotropic thermal diffusivity through calculation, the test process is easy to operate, and a single test result can al...
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Abstract

The invention discloses a method for testing anisotropic heat diffusion coefficient of a power battery at the same time. The method includes following steps: S10, recording surface temperature of a power battery sample when the power battery reaches heat balance; S20, using a constant-temperature heating source which is already at the temperature of Tw to heat other surfaces perpendicular to the laminating direction of the power battery sample; S30, sampling temperature signals on a face where a heat-insulating clamp contacts with the power battery sample, wherein coordinate distribution of temperature testing points is (x1, y3, 0), (x2, y3, 0), (x3, y1, 0) and (x3, y2, 0), x2=mx1, y2=ny1, m>1, and n>1; S40, setting time when temperature of a certain testing point is increased to preset temperature as t, and reading temperature of other testing points according to t; S50, calculating anisotropic heat diffusion coefficient of the power battery sample in X, Y and Z directions. The anisotropic heat diffusion coefficient can be obtained by only collecting the surface temperature of the battery, and the troublesome processes of teating inside temperature of the battery and building a battery heat transfer model are omitted.

Application Domain

Material thermal conductivityMaterial heat development

Technology Topic

Test batterySignal on +8

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  • Method for testing anisotropic heat diffusion coefficient of power battery at same time
  • Method for testing anisotropic heat diffusion coefficient of power battery at same time
  • Method for testing anisotropic heat diffusion coefficient of power battery at same time

Examples

  • Experimental program(1)

Example Embodiment

[0027] Example 1
[0028] This embodiment provides a method for testing anisotropic thermal diffusion coefficient of a power battery, which includes the following steps:
[0029] S10. Put the power battery sample in a constant temperature box at room temperature, and record the surface temperature T of the power battery sample after reaching thermal equilibrium 0.
[0030] In this embodiment, the power battery sample can be clamped with an adiabatic clamp, and the power battery sample is allowed to stand in a 25°C thermostat. The recorded equilibrium temperature is 25.2°C. Since the equilibrium temperature is read by the temperature sensor, there may be errors.
[0031] S20, the temperature is T w The constant temperature heating source heats other surfaces perpendicular to the lamination direction of the power battery sample 2. In order for the power battery sample to have an obvious heating effect, T w Should be better than T 0 At least 10°C higher. In order to reduce the influence of contact thermal resistance, the constant temperature heating source should be close to the power battery sample 2, or the contact surface between the constant temperature heating source and the power battery 2 should be coated with thermal conductive paste or thermal conductive mud.
[0032] In this embodiment, when the temperature of the surface of the power battery sample is 25.2°C, the temperature of the constant temperature heating source may be 35°C.
[0033] S30. Collect a temperature signal on the contact surface of the adiabatic fixture 1 and the power battery sample 2. The coordinate distribution of temperature test points is (x 1 ,y 3 ,0), (x 2 ,y 3 ,0), (x 3 ,y 1 ,0) and (x 3 ,y 2 ,0). Since the square battery has a symmetrical structure, x 1 , X 2 To be less than half of the total size in the x direction at the same time, y 1 , Y 2 It must be less than half of the total size in the y direction at the same time. The collected temperature signal is a function of time t. In order to get a more accurate time value, the acquisition frequency should be less than or equal to 0.1s. The acquisition can be stopped when the temperature rise of all acquisition signal points is greater than or equal to 2°C.
[0034] In this embodiment, the coordinates of the temperature test point may be (10, 20, 0), (20, 20, 0), (15, 50, 0) and (15, 100, 0), and the unit is mm. Acquisition data record curve such as figure 2 As shown in the figure, the temperature signal of each temperature test point changes with time. The acquisition time is 1000s, and the acquisition frequency is 0.1s.
[0035] S40, fixed time variable, take the time when the temperature of a test point rises to half of the maximum temperature as t 1/2 At the same time, there is a relationship between the sampling point coordinates: x 2 = 2x 1 , Y 2 = 2y 1. The selected test point temperatures are T(x 1 ,y 3 ,t 1/2 ), T(x 2 ,y 3 ,t 1/2 ), T(x 3 ,y 1 ,t 1/2 ), T(x 3 ,y 2 ,t 1/2 ).
[0036] Take the time t when the temperature of test point 1 rises to half of the maximum temperature 1/2 =51s, read the corresponding temperature of the four test points at this moment.
[0037] S50. Calculate the anisotropic thermal diffusivity in the X direction, Y direction and Z direction of the power battery sample.
[0038] In this embodiment, under the first type of boundary conditions, the temperature distribution function of the two-dimensional unsteady heat conduction of the short square cylinder can be expressed as the product of the corresponding two one-dimensional problem solutions, and the following formula can be obtained:
[0039] T ( x 1 , y 3 , t 1 / 2 ) - T w T ( x 2 , y 3 , t 1 / 2 ) - T w = e r f ( K ) e r f ( 2 K )
[0040] Where erf(K) is the Gaussian error function The K value can be obtained by looking up the table, and then the anisotropic thermal diffusion coefficient in the X direction can be calculated Similarly, the anisotropic thermal diffusion system in the Y direction Since the test object is a laminated battery, it is considered that the Z direction has the same thermal conductivity as the Y direction, so the anisotropic thermal diffusion system in the Z direction α z =α y.
[0041] In the method for testing the anisotropic thermal diffusion coefficient of a power battery of the present invention, the anisotropic thermal diffusion coefficient can be obtained by calculation, the test process is easy to operate, and the single test result can also achieve engineering application effects. By controlling the variables x, y, t for multiple measurements, the accuracy and reliability of the entire analytical method in practical applications can be greatly improved.
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