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

Best For Liquids, Pastes, and Powders

ASTM D7896-19

Standard Test
Method

-150 °C To 300 °C

Temperature
Range

Up To 35 Bar

Pressure
Range

The THW-L1 following ASTM D7896-19, is widely used for the accurate measurement of thermal conductivitythermal diffusivity, and specific heat of liquids
and pastes. 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:

  • 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 pastes 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.

 

 

Specification

Materials Liquids, Pastes, and Powders
Measurement Capabilities Bulk Properties
Thermal Conductivity 0.01 to 2 W/m•K
Additional Properties Thermal Diffusivity and Specific Heat
Viscosity Range 0.001 to 10,000,000 cP
Measurement Time 1 second | < 5 seconds
Reproducibility ± 1%
Accuracy* ± 2%
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 (Non-Portable)

Models THW-L1 THW-L1S THW-L1E
Materials Liquids, Pastes, and Powders Liquids, Pastes, and Powders Liquids, Pastes, and Powders
Measurement Capabilities Bulk Properties Bulk Properties Bulk Properties
Thermal Conductivity 0.01 to 2 W/m•K 0.01 to 2 W/m•K 0.01 to 2 W/m•K
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
Repeatability ± 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)

Transient Hot-Wire Models (Portable)

Models THW-L2 THW-L3 THW-S
Materials Liquids, Pastes, and Powders Liquids, Pastes, and Powders Liquids, Pastes, and Powders
Measurement Capabilities Bulk Properties Bulk Properties Bulk Properties
Thermal Conductivity 0.01 to 2 W/m•K 0.01 to 1 W/m•K 0.01 to 2 W/m•K
Additional Properties No No No
Viscosity Range 0.001 to 10,000,000 cP 0.001 to 10,000,000 cP N/A
Measurement Time 1 second | < 5 seconds 1 second 1 to 5 seconds
Repeatability ± 2% ± 2% ± 2%
Accuracy ± 5% ± 5% ± 5%
Temperature Range -50 to 100°C 10 to 40°C 10 to 40°C
Pressure Ambient Ambient N/A
Smallest Volume 15 mL 15 mL Min. Sample Size: 50 mm x 10 mm
Standard ASTM D7896-19 ASTM D7896-19 N/A
External Cooling Apparatus Required Yes Yes N/A

Sample Measurements

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 minute

insert the sample
Insert Sensor

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

Approximate Time: < 1 minute

Run Experiment
Run Experiment

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

Approximate Time: < 1 minute

Export Results to excel
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 minute

Applications

Output results of THW-L1 are thermal conductivity, thermal diffusivity and calculated specific heat. Low back pressure was applied to the fluids, to allow measurements over their boiling point.

 

Thermal Conductivity of Water
thermal conductivity of water

Deviations from reference values:
Water < 2%

Thermal Conductivity of Heptane
Thermal Conductivity of Heptane

Deviations from reference values:
Heptane < 3%

Thermal Diffusivity of Water
Thermal Diffusivity of Water

Deviations from reference values:
Water < 2%

Thermal Diffusivity of Heptane
Thermal Diffusivity of Heptane

Deviations from reference values:
Heptane < 2%

Calculated Specific Heat Capacity

Deviations from reference values:
Water < 2%
Heptane < 5%

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

Thermal Conductivity of Ethylene Glycol
thermal conductivity of Ethylene Glycol

Deviations from reference values:
Ethylene glycol < 1%

Thermal Diffusivity of Ethylene Glycol
thermal Diffusivity of Ethylene Glycol

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.

TRANSIENT HOT WIRE ACCESSORIES (OPTIONAL)

THW-L1 PCM Cell

Paste / 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.

THW-L1-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.

THW-L1 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.

thw 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.

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

 

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