THW-L2 Transient Hot-Wire

The Transient Hot-Wire (THW-L2) is a portable conductivity meter for the measurement of liquids.

Best for liquids

Features

The Transient Hot Wire (THW-L2) Liquid Thermal Conductivity Meter is an advanced measurement system for direct determination of the thermal conductivity of liquids and pastes in accordance with ASTM D7896-19. The THW-L2 was designed with speed and operational simplicity in mind. With a single measurement of less than 2 seconds in duration, small volumes of liquids and pastes can be accurately and precisely measured for thermal conductivity.

The THW-L2 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 60 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, the higher the slope.

Follows international standard: ASTM D7896-19
Portable, economical and accurate
Results without the effects of convection
Easy to use
Optional thermoelectric dry bath for automated temperature testing

Specification

Materials	Liquids
Measurement Capabilities	Bulk Properties
Thermal Conductivity	0.01 to 2 W/m•K
Measurement Time	< 2 seconds
Reproducibility	Typically better than 2%
Accuracy	Typically better than 5%
Temperature Range*	-50 to 100°C
Pressure	Ambient
Smallest Volume	15 ml
Largest Sample Size	Unlimited
Standard	ASTM D7896-19

* Requires cooling/heating apparatus.

Testing Sensor & Applications

Standard THW-L2 Sensor

The THW-L2 comes with the standard 60 mm sensor for testing of liquids and pastes. The sensor is fully inserted into an isothermal sample and measurements are made with the push of a button. In less than 2 seconds, results are displayed for thermal conductivity. Volumes as small as 15 mL can be tested. The easy to use THW software enables measurements to be controlled via computer. When used in conjunction with the optional thermoelectric dry bath, the software can even automate measurements of thermal conductivity with temperature.with temperature.

Thermal Conductivity of Nanofluids

The THW-L2 is capable of testing the thermal conductivity of almost any kind of liquid including nanofluids, nanopowders, emulsions and pastes using the same sensor and measuring cell. The sensitivity of the sensor can record even the smallest thermal conductivity changes when solid particles are settling inside a liquid mixture.

Optional Dry Bath

The optional dry bath allows for automated measurements of thermal conductivity with temperature (-10 to 90 °C or 0 to 100 °C). The THW software automatically controls the increments of temperature steps between the desired start and end temperatures to ensure isothermal conditions and test results are free of temperature drift effects. For wider temperature ranges, additional cooling/heating options are available.

Liquids vs. Temperature

Using the Thermoelectric Dry Bath, the Thermtest THW-L2 is capable of testing liquids over a wide temperature range. In this application, deionized ultra-filtered (DIUF) water was tested from 10 to 70 °C, using the THW-L2. All test results were within 5% of the literature values.

Measurement Process

The Sample

Using the THW-L2, liquid samples of unlimited size can be tested. With the small volume cell insert, volumes as small as 15 mL can be measured. The instrument’s ability to control convection using short test times allows accurate measurements of a wide range of samples with varying viscosities.

Approximate Time: 1 min.

Insert Sensor

Once the liquid has been poured into the sample holder, the sensor can be vertically inserted in place. For smaller sample volumes, position the small volume cell into the sample holder, prior to the addition of the sample and sensor.

Approximate Time: < 1 min.

Run Experiment

The instrument can be controlled through the front panel with the push of a button, or Windows-based computer software. Single temperature point measurements, as well as scheduled temperature intervals, may be performed using the easy to use THW-L2 software.

Approximate Time: < 1 min.

Exporting Results

Using the Windows based software users can save, print, and export test results to Microsoft Excel for further processing once testing is complete.

Approximate Time: 1 min.

Transient Hot Wire (THW) Models Comparison


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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THW-L2 Transient Hot-Wire

Features

Specification