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.

THW-L1 SPECIFICATIONS

MaterialsLiquids and Pastes
Measurement CapabilitiesBulk Properties
Thermal Conductivity0.01 to 2 W/m•K
Additional PropertiesThermal Diffusivity and Specific Heat
Viscosity Range0.001 to 10,000,000 cP
Measurement Time1 second
Reproducibility1%
Accuracy5%
Temperature Range-50 | -35 | 10 to 200°C
PressureUp to 20 bar
Smallest Volume20 mL
StandardASTM D7896-19

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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 20 bar, for testing liquids past their boiling points.

Approximate Time: 1 minute

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 10°C to 200°C. The lower range may be expanded to -50°C if needed.

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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