By Arya Hakimian, Application Scientist
Introduction to Transient Line Source (TLS)
A Transient Line Source (TLS) is a method for measuring thermal conductivity. It involves using a line heat source to heat a material while measuring its temperature response over time. This technique is particularly valuable for testing soils, rocks, viscous liquids, and polymers. The TLS method conforms to ASTM D5334 and D5970.
Principle of Operation – TLS
The TLS is based on the transient heating of the material. A line source, which can be a thin wire or a slender rod, is embedded within the material whose thermal properties are to be measured. When an electrical current is passed through the line source, it heats up, and the heat diffuses into the surrounding material. By monitoring the temperature increase at the line source over a period of time, the thermal conductivity of the material can be calculated.
Handheld Devices vs Research Grade Instruments
A handheld TLS is an extremely portable, low-cost device that is excellent for scenarios such as field testing. While specifications may vary, most handheld options accommodate a thermal conductivity range of 0.1 to 5 W/mK and a temperature range of -40 to 100ºC. This offers a basic capability suited for minimally complex testing requirements. While this may suffice for some, individuals seeking a more robust lab instrument may encounter limitations with a handheld device.
C-Therm’s Trident system offers multiple methods for thermal conductivity characterization, including the TLS method. C-Therm’s TLS provides extended temperature testing capabilities from -55 to 300ºC. Additionally, Trident unlocks options for testing materials under different atmospheric conditions, such as high-pressure environments up to 3000 PSI or under a vacuum. The ability to test across a broader range of temperatures and under various pressures opens the doors for more novel material characterization, such as mimicking polymer melt conditions for applications in injection moulding processes or geological systems studied for geothermal or enhanced oil recovery (EOR) applications. C-Therm’s high-pressure TLS is also uniquely able to measure under hydrogen gas conditions, providing valuable testing capabilities for usage in metal hydride research.
Which is Right for you?
If portability and budget constraints are your top priority, a handheld TLS may be the best option. However, if you’re searching for a research instrument capable of testing under varying representative conditions such as temperature and pressure, C-Therm’s Trident instrument offers industry-leading performance trusted by groups around the world.
What Our Clients Have to Say?
“…The instrument has become very popular within our group for its quick easy reliable measurement and the support from C-Therm has exceeded our expectations. We recently upgraded the unit with the new robust TLS module for work on polymer melts.” – Jose Fonseca, Expert in Thermodynamics at Covestro
“The C-Therm MTPS and TLS sensors have provided us a fast, easy way to characterize the thermal conductivity of our different geological samples.” – Daniel Bohnsack,
Chair of Hydrogeology – Geothermal Energy Group at Technische Universität München
About the Author
Arya Hakimian is C-Therm’s resident Application Specialist. He has extensive experience in thermal analysis and materials characterization, and he holds a MSc in Chemistry and BSc in Medicinal and Pharmaceutical Chemistry from the University of New Brunswick.