Towards the Correct Measurement of Thermal Conductivity of Ionic Melts and Nanofluids

Abstract

Thermophysical properties of engineering fluids have proven in the past to be essential for the design of physical and chemical processing and reaction equipment in the chemical, metallurgical, and allied industries, as they influence directly the design parameters and performance of plant units in the of, for example, heat exchangers, distillation columns, phase separation, and reactors. In the energy field, the search for the optimization of existing and alternative fuels, either using neutral or ionic fluids, is an actual research and application topic, both for new applications and the sustainable development of old technologies. One of the most important drawbacks in the industrial use of thermophysical property data is the common discrepancies in available data, measured with different methods, different samples, and questionable quality assessment. Measuring accurately the thermal conductivity of fluids has been a very successful task since the late 1970s due to the efforts of several schools in Europe, Japan, and the United States. However, the application of the most accurate techniques to several systems with technological importance, like ionic liquids, nanofluids, and molten salts, has not been made in the last ten years in a correct fashion, generating highly inaccurate data, which do not reflect the real physical situation. It is the purpose of this paper to review critically the best available techniques for the measurement of thermal conductivity of fluids, with special emphasis on transient methods and their application to ionic liquids, nanofluids, and molten salts.

Special Issue of the 1st International Conference on Nanofluids (ICNf19)

“…This Editorial note was dedicated to the 1st International Conference on Nanofluids and the 2 nd European Symposium of Nanofluids (ICNf2019). After a short report about the conference, the successful invited submissions [7][8][9][10][11][12][13][14][15] to this Special Issue of Energies were introduced. We believe that the articles in this special issue, whose main parts were presented during the conference, will contribute significantly to the development of nanofluid science and challenges in heat transfer and energy applications.…”

“…The last two papers give an overview of the thermal and electroactive properties of graphene nanofluids [14], and both practical and theoretical recommendations about the measurement of the thermal conductivity of ionic melts and nanofluids [15], respectively. In [14], the authors focus on the development of graphene and reduced graphene oxide dispersed in aqueous and organic electrolytes, and the evaluation of their thermal and electrochemical properties.…”

“…Finally, in [15], the available techniques for the measurement of the thermal conductivity of fluids, including nanofluids, ionic liquids and molten salts, are critically analyzed, with special focus on transient methods.…”

“…Funding: The APC of papers [8,[10][11][12][13][14][15] was funded by the COST Action Nanouptake (CA15119).…”

The Balance between Energy, Environmental Security, and Technical Performance: The Regulatory Challenge of Nanofluids

“…Some degree of caution is also needed when navigating the literature on NFs and INFs, with results encompassing sets of totally different techniques of measurement, characterization, and preparation, without informing correctly about the errors associated to each of them (quality of the measurements and their uncertainty). There are experimental limitations, for example, in the transient hot-wire technique, not always fulfilled or accounted for [ 3 ]. This results in infinite comparisons and tables of data that are never validated [ 4 ], namely with respect to safety.…”