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Picture 1. Thermtest MP-2 Thermal Conductivity Meter
Thermal conductivity MP-2 users benefit from the convenience and accuracy gained when using primary testing methods. The MP-2 controller auto-detects the connected sensor and loads corresponding testing parameters. Measurements are easily performed with the smart on-board software and transferred to computer with an included Windows utility program.
Picture 2. Thermtest THW-L3 Sensor and Sample Cell
The Transient Hot Wire-L3 sensor is one of the many sensors offered with the Thermtest Portable Measurement Platform (MP-2). This sensor offers simple yet accurate measurements of liquids, pastes, and powders from 0.01 to 1 W/(m·K) via the transient hot-wire method, and has a temperature range of 10°C to 40°C. The THW-L3 adheres with an internationally recognized standard of testing by complying with ASTM D7896-19. This sensor has a 5% accuracy and a 2% reproducibility of measurement, making it a highly accurate and precise instrument for measuring the thermal conductivity of liquids, pastes, and powders.
The THW-L3 has a detect current setting that determines the appropriate amount of current to apply based on a test measurement. By reading the result of the test measurement, a current will be set that results in an optimal temperature rise of the sample during testing. The accompanying sample holder can be filled with ~15ml of any liquid, and the sensor can subsequently be inserted into the sample holder. An alternative method of measuring the thermal conductivity of a liquid sample is to insert the THW-L3 directly into the vessel containing the sample.
Picture 3: Measurement Platform-2 (MP-2) with the THW-L3 sensor and sample cell
The THW-L3 sensor was first calibrated with deionized ultra-filtered (DIUF) water at room temperature, and then five measurements were taken to verify the calibration. The sample and sensor were then placed in a dry bath and cooled to 10°C. Once isothermal conditions were reached, five measurements were taken with the THW-L3 sensor. The dry bath was then heated to 20°C, 30°C, and 40°C, and the sensor and sample were allowed to become isothermally stable at each temperature before measurements were taken. The results were then compared to literature values of water.
Picture 4: Set-up used to measure DIUF water with dry bath, Thermtest THW-L3 sensor, and MP-2.
The Thermtest THW-L3 sensor has a 5% accuracy and a 2% reproducibility of measurement, making it a highly accurate and precise instrument for measuring the thermal conductivity of liquids, pastes, and powders.
Table 1: Average values of thermal conductivity of DIUF water measured with the Thermtest THW-L3 sensor and reference values.
Sample | Temperature (°C) |
Measured λ (W/mK) |
Reference λ (W/mK) |
Accuracy (%) |
RSD (%) |
---|---|---|---|---|---|
DIUF Water | 10 | 0.583 | 0.579 | 0.73 | 1.07 |
20 | 0.589 | 0.589 | 1.51 | 1.05 | |
30 | 0.614 | 0.614 | 0.00 | 1.67 | |
40 | 0.649 | 0.628 | 3.27 | 0.73 |