THW-L1
LIQUID THERMAL CONDUCTIVITY INSTRUMENT

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 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.

Transient Hot-Wire (THW) Models

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)

Portable THW Models

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

Optional THW-L1 Sample Cells

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.

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.

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.

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.

Optional THW-L1 Accessories

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.

Vertical cell mount attached without sample
Vertical cell mount attached without sample.
Vertical cell mount with sample loaded.
Vertical cell mount with sample loaded.
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

Sample Measurements

1

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

step 2 insert sensor to thw-l1

2

INSERT SENSOR

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

Approximate Time: < 1 minute

3

RUN EXPERIMENT

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

Approximate Time: 1 minute

4

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

THW-L1 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

Deviations from reference values:
Water < 2%

THERMAL CONDUCTIVITY OF HEPTANE

Deviations from reference values:
Heptane < 3%

THERMAL DIFFUSIVITY OF WATER

Deviations from reference values:
Water < 2%

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

Deviations from reference values:
Ethylene glycol < 1%

CALCULATED SPECIFIC HEAT CAPACITY

Deviations from reference values:
Ethylene glycol < 2%

THERMAL DIFFUSIVITY OF ETHYLENE GLYCOL

Deviations from reference values:
Ethylene glycol < 1%

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.

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