The lab folks at PureTemp have had a keen interest in the T-history method since our days as a tech startup with a small budget. T-history is a relatively simple, low-cost way to determine the heat of fusion, specific heat and thermal conductivity of phase change materials.
New research on the topic turned up in one of our automated searches earlier this month: “Characterizing phase change materials using the T-History method: On the factors influencing the accuracy and precision of the enthalpy-temperature curve.” The lead author, Pepe Tan, is a pursuing a Ph.D. at Chalmers University of Technology in Sweden. I contacted him to find out more.
Q: What prompted your interest in studying the T-history method?
A: “When I started my Ph.D. at Chalmers, T-history was a good complement to the available DSC instrument in our research group. And it was a nice opportunity to collaborate with ZAE Bayern and learn the method. While implementing the method, we found it was very worth studying certain aspects of it in parallel, because of how different the method has been presented so far in the scientific community.”
Q: Do you envision T-history replacing DSC for characterizing and validating PCMs as an industry standard? If not for PCM validation, perhaps for application engineering and thermal modeling?
A: “I definitely consider T-history and DSC as complementary methods since their limitations for finding the intrinsic PCMs properties are still subject to research. With this uncertainty, any measurement available from different sources would be useful for the engineer to carefully estimate the actual behavior of the PCM in its application.”
Q: When do you believe T-history will be studied and validated sufficiently to become adopted as a commercially available piece of equipment?
A: “To reach that goal, a systematic assessment of different implementations of the method (setup and data evaluation) would be necessary. But spending this effort also depends on the current needs for accurate PCM properties in typical applications.”
Q: Will the mathematical model of the method become open-source and available for laboratories?
A: “The data evaluation method in the paper should be seen as one proposal on how to calculate the enthalpy from real experimental data. And it is presented in detail, so that it can be recreated.
“The challenge in our experiments was to negate the noise amplification when differentiating the temperature over time data. But this could be done in many different ways, which will in turn affect the enthalpy results. We made the raw experimental data available so that other data evaluation methods can be tested.”
Q: What do you view as the most significant challenge with T-history? How does this compare to the challenges associated with DSC?
A: “That would be to perform a rigorous measurement uncertainty analysis in order to specify a reliable limit for accuracy and precision in terms of an uncertainty. Since this strongly depends on the individual implementation of the method and the chosen data evaluation, the DSC is in my opinion one step ahead.”
Q: Is T-history capable of accurate and precise measurement with thermal conductivity additives or nucleating agents?
A: “This depends on the material and the actual implementation of the method. And this would be an example where the possibility to use complementary methods that utilize different sample sizes like DSC and T-history will be helpful to filter out the intrinsic material behavior. The larger sample sizes of the T-history setup should increase the chance to actually have representative samples, meaning samples containing a representative amount of the nucleating agent and/or the thermal conductivity additives."
Q: What are your postdoctoral plans?
A: “I expect to graduate by June 2020. At the moment, I plan to wait and see what options are available when the graduation date comes a bit closer.”