The Transient Hot Wire (THW-L1) is widely used for the accurate measurement of thermal conductivity, thermal diffusivity, and specific heat capacity of liquids, pastes, and powders.
Best For Liquids, Pastes, and Powders
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 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.
Features:
- 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
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 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, 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.
Specification
| Materials | Liquids, Pastes, and Powders |
| 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
Transient Hot-Wire Models (Non-Portable)
| 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)
Transient Hot-Wire Models (Portable)
| 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 |
Sample Measurements
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 Sensor
For testing with temperature, the liquid cell is inserted into the integrated temperature platform.
Approximate Time: < 1 minute
Run Experiment
The THW-L1 Software automatically controls isothermal steps of temperature from -150 to 300°C.
Approximate Time: < 1 minute
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
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%
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.
TRANSIENT HOT WIRE ACCESSORIES (OPTIONAL)
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.
Ambient Density Powder Cell
The THW-L1 Ambient density Powder Cell is suitable for basic powder sample testing and ambient pressure.
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.
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
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
- Economy Circulator: Down to 0°C
- THW-L1 Circulator: Down to -15 / -35 / -50°C
- THW-L1E Only: Down to -100 / -150°C
