THW-L1 Transient Hot Wire

The Transient Hot Wire (THW-L1) is widely used for the accurate measurement of thermal conductivity, thermal diffusivity, and specific heat capacity of liquids and PCMs.

Best for liquids and PCMs

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    THW-L1

    The THW-L1 following ASTM D7896-19, is widely used for the accurate measurement of thermal conductivity, thermal diffusivity, and specific heat of liquids and PCMs. This versatility is greatly expanded with the addition of Thermtest’s proprietary Temperature Platform (TP) which is appreciated by academic and commercial users alike.

    The Transient Hot-Wire (THW) has been used for the testing of liquids for more than 30 years, making it one of the most published methods for measuring thermal conductivity of liquids available

    Features

    THW-L1 Features
    • Follows international standard ASTM-D7896-19
    • Automated, powerful & accurate
    • Minimum effects of convection
    • Cell Pressure up to 35 bar
    • Integrated temperature control
    • Unique wire clamping for easy replacement

    The Transient Hot-Wire (THW-L1) Liquid Thermal Conductivity Meter is an advanced measurement system for primary measurements of thermal conductivity, thermal diffusivity, and specific heat instrument for measurement of liquids and PCMs in accordance with ASTM D7896-19.

    The THW-L1 was designed with speed and operational simplicity in mind. With a single measurement of 1 second in duration, small volumes of Liquids, Pastes, and Powders can be accurately and precisely measured for thermal conductivity, thermal diffusivity, and specific heat. The THW-L1 utilizes a non-stationary measurement approach and rapid test times to limit convective effects for samples with a wide range of viscosities.

    The THW sensor consists of a thin heating wire 40 mm in length and is completely 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.

    THW equation

    Specifications

    Materials

    Liquids and PCMs

    Measurement Capabilities

    Bulk Properties

    Thermal Conductivity

    0.01 to 2 W/m•K

    Additional Properties

    Thermal Diffusivity & Specific Heat

    Viscosity Range

    0.001 to 10,000,000 cP

    Measurement Time

    1 second | < 5 seconds

    Reproducibility

    ± 1%

    Accuracy*

    ± 5%

    Temperature Range†

    -150 to 300°C

    Pressure

    Up to 35 bar

    Smallest Volume

    20 mL

    Standard

    ASTM D7896-19

    *All performance data is verified with ASTM Type II Water (IAPWS)
    †Based on THW-L1 model used

    Transient Hot-Wire Models (THW)

    Models

    THW-L1

    THW-L1S

    THW-L1E

    Materials

    Liquids and PCMs

    Liquids and PCMs

    Liquids and PCMs

    Measurement Capabilities

    Bulk Properties

    Bulk Properties

    Bulk Properties

    Thermal Conductivity (W/m•K)

    0.01 to 2

    0.01 to 2

    0.01 to 2

    Additional Properties

    Thermal Diffusivity and Specific Heat

    Thermal Diffusivity and Specific Heat

    Thermal Diffusivity and Specific Heat

    Viscosity Range

    0.001 to 10,000,000 cP

    0.001 to 10,000,000 cP

    0.001 to 10,000,000 cP

    Measurement Time

    1 second | < 5 seconds

    1 second | < 5 seconds

    1 second | < 5 seconds

    Reproducibility

    ± 1%

    ± 1%

    ± 1%

    Accuracy*

    ± 2%

    ± 2%

    ± 2%

    Temperature Range

    10 to 200°C

    -50 to 200°C

    -150 to 300°C

    Pressure

    Up to 20 bar

    Up to 20 bar

    Up to 35 bar

    Smallest Volume

    20 mL

    20 mL

    20 mL

    Standard

    ASTM D7896-19

    ASTM D7896-19

    ASTM D7896-19

    External Cooling Apparatus Required

    No

    Yes

    Yes

    *All performance data is verified with ASTM Type II Water (IAPWS)

    Optional THW-L1 Accessories

    Paste and PCM Cell

    Paste and PCM Cell

    Special Phase Change Materials (PCM) with easy to load access. Unique spring design allows sample expansion and contraction, while ensuring sample is in constant contact with THW wire during measurement.
    Observation Cell

    Observation Cell

    THW-L1 observation sample cell is used for liquids, powder, and paste testing. The cell has convenient glass ports for observing what is happening with your sample. Typical applications are phase separation, boiling or particle settling to name a few

    Ambient Density Powder Cell

    Ambient Density Powder Cell

    The THW-L1 Ambient density Powder Cell is suitable for basic powder sample testing and ambient pressure.
    Variable Density Powder Cell

    Variable Density Powder Cell

    THW-L1 test cell with screw-type compression system for varying the density of powder samples. Can also be used to ensure powders stay in contact with THW wire.
    Vertical Cell Mount

    Vertical Cell Mount

    Convenient THW cell mount that can be attached to your THW-L1 for vertical sample loading. Ideal for the Paste/PCM and all Powder Cells.
    cooling options

    Cooling Options

    • Economy Circulator: Down to 0°C
    • THW-L1 Circulator: Down to -15 / -35 / -50°C
    • THW-L1E Only: Down to -100 / -150°C

    THW-L1 Applications

    Low back pressure was applied to the fluids, to allow measurements over their boiling point.

    Thermal Conductivity of Water

    thermal diffusivity of water THW-L1

    Thermal Conductivity deviations from reference values:
    Water < 2%

    Thermal DIffusivity of Water

    thermal diffusivity of water THW-L1

    Thermal Diffusivity deviations from reference values:
    Water < 2%

    Thermal Conductivity of Heptane

    Thermal conductivity Heptane

    Thermal Conductivity deviations from reference values:
    Heptane < 3%

    Thermal Diffusivity of Heptane

    thermal diffusivity of heptane

    Thermal Diffusivity deviations from reference values:
    Heptane < 2%

    Calculated Specific Heat Capacity deviations from reference values:
    Water < 2%
    Heptane < 5%

    Thermal Conductivity of Ethylene Glycol

    Thermtest THW-L1 Thermal Conductivity Ethylene Glycol

    Thermal Conductivity deviations from reference values:
    Ethylene Glycol < 1%

    Thermal Diffusivity of Ethylene Glycol

    thermal diffusivity of Ethylene Glycol graph

    Thermal Diffusivity deviations from reference values:
    Ethylene Glycol < 1%

    Calculated Specific Heat Capacity deviations from reference values:
    Ethylene Glycol < 2%

    Citation:
    Lemmon, E.W., Bell, I.H., Huber, M.L., McLinden, M.O. (2018). NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP, Version 10.0. National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg.

    Measurement Process

    The Sample

    The Sample

    The liquid is poured into the sample cell, the required volume is 20 ml. The THW-L1’s ability to limit convection, using short test times, allows accuracy measurements of a large range of samples, widely varying viscosities. The sample cell can then be back filled to pressures up to 35 bar, for testing liquids past their boiling points.
    Approximate Time: 1 min.
    Insert Sensor

    Insert Sensor

    For testing with temperature, the liquid cell is inserted into the integrated temperature platform.

    Approximate Time: < 1 min.

    Run experiment

    Run Experiment

    The THW-L1 Software automatically controls isothermal steps of temperature from -150 to 300°C.

    Approximate Time: < 1 min.

    THW-L1 Export Results

    Exporting Results

    Smart THW-L1 Windows Software verifies quality of results and recommends changes if needed. Results report can be generated, saved, and exported to excel. For convenience results may also be emailed.

    Approximate Time: 1 min.

    Transient Hot Wire (THW) Models Comparison


    mp-1 thw

    THW-L1

    thw-l2

    Models

    MP-1 with THW

    THW-L1

    THW-L2

    MP-2 with THW-L3

    Materials

    Liquids, Pastes, and Powders

    Liquids, Pastes, and Powders

    Liquids, Pastes, and Powders

    Liquids, Pastes, and Powders

    Testing Modules

    Bulk

    Bulk

    Bulk

    Bulk

    Other Materials

    Solids with TPS

    No

    No

    Solids with TPS, TLS

    Thermal Conductivity

    0.01 to 2 W/m•K

    0.01 to 2 W/m•K

    0.01 to 2 W/m•K

    0.01 to 1 W/m•K

    Sample Size

    20 mL

    20 mL

    15 mL

    15 mL

    Additional Properties

    Thermal Diffusivity and Specific Heat

    Thermal Diffusivity and Specific Heat

    No

    No

    Temperature Range

    Room Temperature

    10 to 200 °C | -50/-15/0 to 200 °C

    -160/-45/-15/0 to 300 °C

    10 to 200 °C | -50/-15/0 to 200 °C

    -160/-45/-15/0 to 300 °C

    -50 to 100 °C

    Room Temperature

    10 to 40 °C

    Pressure

    Up to 35 bar*

    Up to 35 bar*

    Ambient

    Ambient

    Test Times

    1 second

    1 second

    1 second | < 5 seconds

    1 second

    Data-Points

    400 points/second

    100 points/second

    60 points/second

    60 points/second

    Thermal Conductivity Accuracy

    2 %

    2 %

    5 %

    5 %

    Repeatability

    1 %

    1 %

    2 %

    2 %

    Standards

    ASTM D7896-19

    ASTM D7896-19

    ASTM D7896-19

    ASTM D7896-19

    External Cooling Apparatus Required

    No | Yes*

    No | Yes*

    Yes

    Yes

    *Depending on the Model used

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