Transient Hot-Wire (THW-L2)

The Transient Hot-Wire (THW-L2) is widely used for the accurate measurement of thermal conductivity for liquids and pastes.

Best For Liquids and Pastes

ASTM D7896-19

Standard Test

– 50°C to 100°C


Ambient Only


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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. The THW-L2 was designed with speed and operational simplicity in mind. With a single measurement of less than 2 seconds in duration, small volumes of liquids and pastes can be accurately and precisely measured for thermal conductivity. The THW-L2 utilizes a non-stationary measurement approach and rapid test times to limit convective effects for samples with a wide range of viscosities.

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    The THW sensor consists of a thin heating wire 60 mm in length, fully inserted into the sample to be tested. The sensor wire is heated using a constant current source (q), and the temperature rise is recorded by monitoring the change in electrical resistance of the wire. The slope (m) from the plot of temperature rise vs. logarithm of time is used in the calculation of thermal conductivity (λ). For liquid samples of high thermal conductivity, the lower the slope. For liquid samples of low thermal conductivity, the higher the slope.

    transient hot wire equation

    • Follows international standard: ASTM D7896-19
    • Portable, Economical, & Accurate
    • Results without the effects of convection
    • Easy to use
    • Optional thermoelectric dry bath for automated temperature testing
    Materials Liquids & 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 to 100°C
    Pressure Ambient
    Smallest Volume 15 ml
    Largest Sample Size Unlimited
    Standards ASTM D7896-19
    1 Requires cooling/heating apparatus.
    Testing Sensors
    Standard THW-L2 Sensor
    Standard THW-L2 Sensor

    The THW-L2 comes with the standard 60 mm sensor for the 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. Sample volumes as small as 15 ml can be tested. The easy to use THW software enables measurements to be controlled via a computer. When used in conjunction with the optional thermoelectric dry bath, the software can even automate thermal conductivity measurements with temperature.

    THW-L2 sensor

    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. Expanded polystyrene was measured with the THW-L2 and given a result of 0.031 W/m•K, which is within 5% of the literature values.

    Sample Measurements
    the sample
    The Sample

    Liquid samples of unlimited size can be tested with the THW-L2. With the small volume cell insert, volumes as low 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

    insert sample
    Insert Sample

    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

    run the experiment
    Run Experiment

    The instrument can be controlled through the front panel with the push of a button, or Windows-based computer software. Single temperature point measurements, as well as scheduled temperature intervals, may be performed using the easy to use THW software.

    Approximate Time: < 1 minute

    Exporting Results
    Exporting Results

    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

    Related Research Papers
    Find related research papers:

    Physical Properties of 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (mTBD)

    7-Methyl-1,5,7-triazabicyclo[4,40]dec-5-ene (mTBD) is an important industrial chemical that is commonly used as a catalyst. Prior to the research conducted by Baird et al, the only available data on this chemical pertained to its density and a single vapor pressure value that is provided on chemical safety data sheets…

    Investigation of the Thermal Conductivity and the Viscosity of Carbon Black Heat Transfer Nanofluids

    Seven distinct samples of nanofluids consisting of different concentrations of spherical graphitized carbon black in an ethylene glycol solution were analyzed to determine their thermal and rheological behavior. The thermal conductivity measurements were made at 20°C and 30°C with a transient hot wire instrument made by Thermtest called THW-L2…

    Thermal Conductivity of Solvents
    Thermal Conductivity of Solvents

    Thermal conductivities of four commonly used solvents that have similar physical properties.

    Thermal Conductivity of DIUF Water
    Thermal Conductivity of DIUF Water

    Thermal Conductivity of Deionized Ultra-filtered (DIUF) Water with the THW-L2 Transient Hot Wire

    Thermal Conductivity and Viscosity of Carbon Black Heat Transfer Nanofluids
    Thermal Conductivity and Viscosity of Carbon Black Heat Transfer Nanofluids

    Thermal Conductivity and Viscosity of Carbon Black Heat Transfer Nanofluids

    THW-L2 Accessories

    PCM Mould

    PCM Mould

    To cast PCM samples for the THW-L2.


    Thermoelectric Dry Bath

    Used for testing samples from -10 to 100 °C.


    One of our qualified team members will reach out to you to offer a price that fits your needs.

      Featured Webinar

      Thermal Conductivity of cutting fluids with the Transient Hot Wire

      Depending on the context and on which type of cutting fluid is being considered, these fluids may be referred to as cutting fluid, cutting oil, cutting compound, coolant, or lubricant. The main purposes of these fluids are to keep the object being cut at a stable temperature, maximize the life of the cutting tip, and prevent rust on machine parts and cutters.

      December 8, 2021


      Sofia Mylona


      Mitchell Robinson

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