The Transient Hot Wire (THW-L2) Liquid Thermal Conductivity Meter is a portable measurement system for direct determination of the thermal conductivity of liquids and pastes. The THW-L2 follows international standard ASTM D7896-19, and was designed with speed and operational simplicity in mind.
Designed with speed and operational simplicity in mind, the Transient Hot Wire (THW-L2) Liquid Thermal Conductivity Meter is an advanced measurement system for direct determination of the thermal conductivity of liquids and pastes in accordance with ASTM D7896-19. In less than 2 seconds, a single measurement of small volumes of liquids and pastes can be accurately and precisely measured for thermal conductivity. Using a non-stationary measurement approach, the THW-L2 uses rapid test times to limit convective effects for samples with a wide range of viscosities. The THW sensor consists of a 60 mm heating wire that is fully inserted into an isothermal sample. A constant current source (q) is used to heat the sensor wire and the temperature rise is recorded by monitoring the change in electrical resistance of the wire. The slope (m) is determined from the plot of temperature rise vs. logarithm of time and is used in the calculation of thermal conductivity (λ). Liquid samples of high thermal conductivity will have a lower slope, while liquid samples with low thermal conductivity will have a higher slope.
| Materials | Liquids and Pastes |
| Measurement Capabilities | Bulk Properties |
| Thermal Conductivity | 0.01 to 2 W/m•K |
| Measurement Time | < 2 seconds |
| Reproducibility | Typically better than 2% |
| Accuracy | Typically better than 5% |
| Temperature Range 1 | -50°C to 100°C |
| Pressure | Ambient |
| Smallest Volume | 15 ml |
| Largest Sample Size | Unlimited |
| Standards | ASTM D7896-14 |
1 Requires cooling/heating apparatus.
The THW-L2 comes with the standard 60 mm sensor for testing of liquids and pastes. The sensor is fully inserted into an isothermal sample and measurements are made with the push of a button. In less than 2 seconds, results are displayed for thermal conductivity. Volumes as small as 15 ml can be tested. Measurements can also be controlled by a computer with the easy to use THW software.
Using the included THW-L2 software and optional dry bath, automated measurements of thermal conductivity with temperature (-10 to 90°C or 0 to 100°C) have never been more convenient. The THW software automatically controls the increments of temperature steps between the desired start and end temperatures to ensure isothermal conditions and test results are free of temperature drift effects. For wider ranges of temperature, additional cooling/heating options are available.
The THW-L2 is capable of testing low thermal conductivity, compressible insulations, without the liquid sample holder. Samples with minimum dimensions of 65 mm in length and 2 mm in thickness can be tested in a horizontal configuration, with the sensor sandwiched between the samples. Using the THW-L2, expanded polystyrene was measured as 0.031 W/m•K, which is within 5% of the literature values.
1
Using the THW-L2, liquid samples of unlimited size can be tested. With the small volume cell insert, volumes as small as 15 mL can be measured. The instrument’s ability to control convection, using short test times, allows accurate measurements of a wide range of samples, with varying viscosities.
Approximate Time: 1 minute
2
Once the liquid has been poured into the sample holder, the sensor can be vertically inserted in place. For smaller sample volumes, position the small volume cell into the sample holder, prior to the addition of the sample and sensor.
Approximate Time: 1 minute
3
The instrument can be controlled through the front panel with the push of a button, or through a Windows based computer software. Single temperature point measurements, as well as scheduled temperature intervals may be performed using the THW software.
Approximate Time: 1 minute
4
Using the Windows based software, users can save, print, and export test results to Microsoft Excel, for further processing once testing is complete.
Approximate Time: 1 minute
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