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Transient Hot-Wire (THW-L1)

The Transient Hot Wire (THW-L1) is a laboratory instrument for thermal conductivity, thermal diffusivity and specific heat instrument of liquids, and PCMs.

Best For Liquids and PCMs

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 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.

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Features

THW-L1 features

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.

  • 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
Specification
Materials Liquids and PCMs
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

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.

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

Related Research Papers
Find related research papers:

Thermal Conductivity of Suspensions of Carbon Nanotubes in Water

An investigation on the enhancement of the thermal conductivity of water with the addition of multiwalled carbon nanotubes, (C-MWNT). C-MWNT occupied 0.6% of the volume in the test sample for every…

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.

Transient Hot Wire (THW) Models Comparison

Models
Materials
Testing Modules
Other Materials
Thermal Conductivity
Sample Size
Additional Properties
Temperature Range
Pressure
Test Times
Data-Points
Thermal Conductivity Accuracy
Repeatability
Standards
External Cooling Apparatus Required
MP-1 with THW
Liquids, Pastes, and Powders
Bulk
Solids with TPS
0.01 to 2 W/m•K
20 mL
Thermal Diffusivity and Specific Heat
Room Temperature
10 to 200 °C | -50/-15/0 to 200 °C
-160/-45/-15/0 to 300 °C
Up to 35 bar*
1 second
400 points/second
2 %
1 %
ASTM D7896-19
No | Yes*
THW-L1
Liquids, Pastes, and Powders
Bulk
No
0.01 to 2 W/m•K
20 mL
Thermal Diffusivity and Specific Heat
10 to 200 °C | -50/-15/0 to 200 °C
-160/-45/-15/0 to 300 °C
Up to 35 bar*
1 second
100 points/second
2 %
1 %
ASTM D7896-19
No | Yes*
THW-L2
Liquids, Pastes, and Powders
Bulk
No
0.01 to 2 W/m•K
15 mL
No
-50 to 100 °C
Ambient
1 second | < 5 seconds
60 points/second
5 %
2 %
ASTM D7896-19
Yes
MP-2 with THW-L3
Liquids, Pastes, and Powders
Bulk
Solids with TPS, TLS
0.01 to 1 W/m•K
15 mL
No
Room Temperature
10 to 40 °C
Ambient
1 second
60 points/second
5 %
2 %
ASTM D7896-19
Yes
*Depending on the Model used

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

Request a Demonstration

We are happy to arrange a live demonstration for you!

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