THW-L1
LIQUID THERMAL CONDUCTIVITY INSTRUMENT
TRANSIENT HOT WIRE
ASTM D7896-19
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.
FEATURED CAPABILITIES
FEATURED TRANSIENT HOT WIRE CAPABILITIES
The Transient Hot Wire (THW-L1) Liquid Thermal Conductivity Meter is an advanced measurement system for direct determination of the 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 and pastes 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 20 bar
- Integrated temperature control
- Unique wire clamping for easy replacement
THW-L1 SPECIFICATIONS
| Materials | Liquids and Pastes |
| 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 |
| Reproducibility | 1% |
| Accuracy | 5% |
| Temperature Range | -50 | -35 | 10 to 200°C |
| Pressure | Up to 20 bar |
| Smallest Volume | 20 ml |
| Standard | ASTM D7896-19 |
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
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%
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.