Cryogenic Thermal Conductivity Measurement Device
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Solution Overview
Problem
Current methods for measuring thermal conductivity, especially at cryogenic conditions, are inadequate for testing thin samples, require complex sample preparation, and involve high costs due to the need for pressure loads and contamination issues in cryogenic environments.
Innovation Solution
A device comprising test modules with a cooling circuit, multi-layer insulation, and temperature sensors that allow for thermal conductivity measurements under high vacuum at a wide range of temperatures, including cryogenic conditions, using a modular design with adaptable sample holders and reusable insulation to minimize heat loss and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fiber isolation is used in cryogenic chambers, then thermal insulation is achieved, but contamination of the chamber and difficulty in mounting/dismounting occur
Solution Approach 1:
The patent removes the fiber isolation material from the cryogenic chamber environment entirely. Instead, it uses a vacuum-insulated double-walled chamber design where the sample is suspended between two parallel plates within the vacuum space, eliminating the need for fiber-based thermal isolation that causes contamination.
Solution Approach 2:
The patent introduces a vacuum space as an intermediary medium between the sample and the chamber walls to provide thermal insulation. This vacuum barrier replaces the fiber isolation material, achieving thermal protection without the contamination issues associated with fibers in the cryogenic environment.
2Measurement precision
If comparative method with calibrated material is used, then thermal conductivity measurement is achieved, but complex sample preparation and pressure load requirements increase test complexity and cost
Solution Approach 1:
The patent employs a self-service approach where the system automatically characterizes the sample without requiring external reference materials or complex calibration procedures. The dual-plate configuration with integrated heating and temperature sensing allows direct measurement of thermal conductivity through the sample itself, eliminating the need for comparative methods with calibrated materials.
Solution Approach 2:
The patent divides the measurement system into independent functional modules: a heating element, temperature sensors, and a vacuum-insulated chamber. This segmentation allows for simplified sample preparation where samples are simply placed between the parallel plates without requiring complex mounting procedures or pressure loads.
3Measurement precision
If steady-state heat flux method is used, then thermal transmission properties are measured, but the method is inadequate for testing thin samples
Solution Approach 1:
The patent applies local quality by creating a localized measurement zone between the two parallel plates where the thermal gradient is concentrated. This focused approach allows accurate measurement of thin samples by confining the heat flux measurement to a small, well-defined region, improving the adaptability for testing various sample thicknesses including very thin materials.
Solution Approach 2:
The patent transitions from traditional through-the-thickness plate measurement to a parallel-plate configuration where samples are positioned horizontally between two plates. This dimensional change allows for better accommodation of thin samples and enables measurement of materials that would be difficult to test with conventional vertical plate methods.
4Adaptability or versatility
If multiple samples are tested sequentially with fiber isolation, then various samples can be measured, but mounting and dismounting operations become difficult and time-consuming
Solution Approach 1:
The patent removes the fiber isolation material that complicates sample mounting and dismounting. The vacuum-insulated chamber design allows samples to be easily placed and removed from between the parallel plates without the need to navigate around or remove fiber insulation, significantly reducing the time required for sample changes while maintaining the ability to test various sample types.
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
Enables accurate and efficient thermal conductivity testing of various samples at cryogenic temperatures with reduced contamination, heat loss, and cost, allowing for low conductivity measurements and easy reuse across different sample sizes.
Implementation Method 1
the base of the set-up can be cooled, for example, with nitrogen (-196 °C), hydrogen (-253 °C) and helium (-269 °C)
Implementation Method 2
the sample heater is specifically isolated from the rest of the interior of the casing through multi-layer insulation
Implementation Method 3
the temperature sensors are thermocouples
Implementation Method 4
a plurality of heaters that heat the sample and the casing
Data Source
Figure 1
Figure 2
AI summary
The device for measuring the thermal conductivity of samples comprises: one or more test modules (2), the or each test module (2) comprising a casing (4) and a module base (12) for a sample (5); a cooling circuit (3) for cooling the one or more test modules (2); a plurality of heaters (9) that heat the sample (5) and the casing (4); a plurality of temperature sensors (8) that measure the temperature of the sample or samples (5) and casing or casings (4); and control means (10) that receive the power fed to the heaters (9) and the temperature measured by the temperature sensors (8) for measuring the thermal conductivity of the sample or samples (5). It permits to carry out conductivity tests of various samples under high vacuum at a wide range of temperatures, especially at cryogenic conditions.