In-Plane Thermal Conductivity Test for Sheet Materials
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Solution Overview
Problem
Conventional methods for testing the in-plane heat-conducting performance of sheet materials, particularly non-uniform and anisotropic materials, face challenges with poor accuracy and repeatability due to surface heat loss and the need for uniform heat flow, which is difficult to achieve especially in thin samples.
Innovation Solution
A steady-state test method involving continuous local heating of the sheet material at constant power, measuring surface temperature distribution, calculating temperature gradients, and estimating total heat flow power to determine in-plane thermal conductivity, allowing for testing even in small regions and reducing the influence of surface heat loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional steady-state test method is used to measure in-plane thermal conductivity of sheet material, then the thermal conductivity can be calculated from heat flow density and temperature gradient, but surface heat loss has a great influence on the test and it is difficult to ensure uniformity and continuity of heat flow in the sample, resulting in poor test accuracy and repeatability
Solution Approach 1:
The patent divides the sample into multiple measurement regions and uses multiple thermocouples to measure temperature gradients at different locations. By segmenting the measurement process, the method can identify and exclude regions affected by surface heat loss, thereby improving measurement accuracy without requiring uniform heat flow across the entire sample.
Solution Approach 2:
The patent focuses measurements on specific local regions within the sample where heat flow conditions are more favorable. By using multiple thermocouples at different positions and selecting measurement data from regions with better heat flow uniformity, the method achieves accurate thermal conductivity measurement without requiring the entire sample to have uniform heat flow.
2Device complexity
If the heat flow density in the sample is uniformly distributed on a heat transfer section, then the thermal conductivity calculation is simplified, but many measures need to be taken in control of sample preparation and test conditions, such as large sample heat transfer section size, enough distance from heat source, and surface insulation
Solution Approach 1:
Instead of requiring uniform heat flow across a large sample area, the patent segments the measurement into multiple local points using arrays of thermocouples. This allows accurate measurement of temperature gradients in small regions without needing to control the entire sample to have uniform heat flow, thereby simplifying test condition control while maintaining measurement accuracy.
Solution Approach 2:
The patent replaces the mechanical approach of ensuring uniform heat flow through careful sample preparation and positioning with a field-based approach using multiple temperature sensors. By measuring temperature gradients at multiple points and using computational methods to determine thermal conductivity, the method eliminates the need for complex mechanical control of heat flow uniformity.
3Adaptability or versatility
If a sheet sample is directly tested without preparing a thick sample that meets test requirements, then the heat-conducting performance of the material in actual application can be reflected, but the thickness direction of the sample has an extremely small size, total power of heat flow passing through the heat transfer section is extremely small, and surface heat loss has a great influence on the test
Solution Approach 1:
The patent uses multiple thermocouples arranged in arrays to measure temperature gradients at different locations within the thin sample. By segmenting the measurement process and using computational methods to aggregate data from multiple points, the method can accurately determine thermal conductivity even when total heat flow through the sample is very small, thereby enabling direct testing of thin samples without significant surface heat loss interference.
Solution Approach 2:
The patent combines measurements from multiple thermocouples at different positions and depths within the sample to obtain a comprehensive view of the temperature field. By merging data from multiple measurement points and using computational analysis, the method extracts accurate thermal conductivity information while minimizing the impact of surface heat loss that would otherwise dominate in thin samples.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method improves the accuracy and repeatability of thermal conductivity measurements by eliminating the need for uniform heat flow and reducing surface heat loss, enabling the evaluation of thermal conductivity distribution in non-uniform materials.
Implementation Method 1
continuously locally heating a to-be-tested sheet by an electrical heating device at constant power
Implementation Method 2
causing heat conduction in a plane direction
Implementation Method 3
calculating a temperature gradient of each point along a normal on the test line
Implementation Method 4
a heat sink of the heat flow having an open cavity
Data Source
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AI summary
The present invention discloses a steady-state test method for in-plane heat-conducting performance of a sheet test sample. In the present invention, the sheet sample is locally heated until a thermal equilibrium state is reached, and then a thermal conductivity is calculated according to a result of integration performed for a temperature gradient on a heat transfer section. The present invention is characterized in that heat flow is not required to be uniform, a test may be performed based on an extremely small region of the sheet sample, surface heat loss power is relatively small, and an influence of surface heat dissipation on test accuracy of the thermal conductivity is reduced. Meanwhile, the method is characterized by an apparent thermal conductivity within a small range of a sheet. Therefore, quantitative evaluation for spatial distribution of thermal conductivities of a non-uniform sheet can be obtained by changing the test region. Based on the same idea, the method is also applicable to a sheet material oriented to thermal anisotropy after being slightly modified.