But what if we could use solid materials instead of fluids as an economical and environmentally friendly way to cool down food, beverages, medicine, and even electronic devices?
It’s something that the Luxembourg Institute of Science and Technology (LIST) is looking into. Researchers at the institute make use of FLIR’s thermal imaging cameras to study the subject in depth.
The Luxembourg Institute of Science and Technology (LIST) is a research and technology organization located in the heart of Luxembourg’s new Research and Innovation Campus at Esch-Belval. The Campus brings together strong potential for innovation uniting university, research centers, joint laboratories, start-ups and incubators.
One of the departments at LIST is the Materials Research and Technology (MRT) group. This department is looking into ways to turn nanotechnology/nanomaterials into application-driven solutions.
One of the research themes is how solid materials exhibiting the electrocaloric effect can be used as cooling systems for, among others, electronic devices.
STUDYING THE ELECTROCALORIC EFFECT
The electrocaloric effect is a phenomenon where a polarizable substance undergoes reversible changes in temperature with the
application or removal of electric fields.
The electrocaloric effect in thin films could have the potential to be used for efficient refrigerators and cooling systems for high power electronic devices. Applying an electric field to an electrocaloric material raises its temperature, and decreasing the field lowers its temperature.
“AttheNanomaterialsandNanotechnologies Unit of PhD researchers, we have been building a prototype of an electrocaloric refrigerator in order to compare it to a conventional refrigerator,” says Romain Faye, researcher atLIST.“Theadvantageofthistechnologyis that electrocaloric refrigerators have a higher energy efficiency and they enable us to avoid the use of potentially harmful fluids.”
More specifically, researchers in the Ferroic Materials for Transducers group are using multilayer capacitors to test the cooling rate of the refrigerator. Multilayer capacitors consist of several tens to few hundreds of ceramic layers of about 10 to 40 microns separated by metal electrodes of several microns which are alternatively connected to 2 external terminals.
The cooling rate of the refrigerator can be easily increased through the electrocaloric effect by increasing the frequency of the electric field.
What is important in this process is the ability to exchange the created heat with the environment before removing the field. This way, it is possible to achieve a temperature that is colder than the ambient temperature.
“We want to exchange heat as quick as possible,” says Romain Faye. “We are trying to determine how this heat exchange process is limited by the material itself, for example in terms of thermal conductivity, or by the shape of the material. If the heat exchange is sufficiently fast, we could be able to switch the field on and off several times per second.”
EFFICIENT, DIRECT MEASUREMENTS
By measuring the electrocaloric effect, researchers at LIST hope to get better insights on the usability of this phenomenon for cooling applications.
“In the past, researchers have mainly been using indirect measurement, whereby the electrocaloric effect is deduced from the measurement of the polarization as a function of temperature and voltage, not from actual temperature measurements” says Romain Faye. “However, indirect measurements have not always resulted in correct interpretations. Therefore, our team has been looking into more efficient ways of direct, temperature-based measurement.”
The most common ways of direct measurement of temperature change are thermocouples and thermal imaging cameras.
Thermocouples are electric devices that measure changes in voltage associated with changes in temperature, while thermal imaging cameras measure changes in IR radiation associated with changes in temperature.
“Thermocouples have not proven to be practical for us,” says Romain Faye. “We are studying very fast temperature changes induced by electrical current, on very small surfaces. Thermocouples just do not offer the precision you need to make that kind of measurements. Thermal imaging on the other hand allows us to show fast heat exchange between materials and the environment in a visual way.”
THERMAL IMAGING OF CALORIC EFFECTS
Compact and high-frequency thermal imaging cameras, like the FLIR X6580sc can provide an accurate and sensitive imaging of caloric effects and thermal behavior of materials both temporally and spatially.
LIST has been studying the thermal behavior of oxide materials by using the FLIR X6580sc camera combined with a lens that allows them to obtain a 3x magnification. The measured thermal variations as a function of the applied electric field have a thermal sensitivity ranging from 20mK to 4K.
“We needed a thermal imaging camera that is able to measure very small temperature differences at a very high frequency,” says Romain Faye.
“The FLIR X6580sc managed to do exactly that. We are truly impressed by the performance of this camera.”
The FLIR X6580sc is a high-end thermal imaging camera for researchers and scientists that provides thermal images of 640 x 512 pixels and is able to record fast dynamic scenes up to 355 Hz.
The camera also provides excellent thermal contrast (with NETD = 20 mK).
LIST researchers have been coupling the FLIR X6580sc with FLIR’s ResearchIR software for thermal measurement, recording and real-time analysis.
The software allows them to record the temperature changes induced by the electric field and to make better distinctions in the image between what is induced by the electric field and what is image noise. This enables them to present the thermal images in even higher detail.
“The support from the FLIR team has been amazing,” says Romain Faye. “They have helped us to make an efficient camera setup and to adapt the camera settings to obtain the best results. And fortunately for us, thanks to the promising results we have booked with our FLIR camera, we will be starting a new follow-on research project within a few months.”
The research work that led to these results has been funded by the National Research Fund of Luxembourg (FNR) through the project COFERMAT FNR/P12/4853155.
For more information about thermal imaging cameras or about this application, please visit:
The images displayed may not be representative of the actual resolution of the camera shown. Images for illustrative purposes only.
Date original created: January 2018