Abstract
This study focuses on the preparation, thermophysical and rheological characterization of phase change material nanoemulsions as latent functionally thermal fluids. Aqueous dispersions with fine droplets of cetyl alcohol (with a melting temperature at ~321 K) were prepared by means of a solvent-assisted method, combining ultrasonication with non-ionic and anionic emulsifiers. Eicosyl alcohol (melting at ~337 K) and hydrophobic silica nanoparticles were tested as nucleating agents. Droplet size studies through time and after freeze–thaw cycles confirmed the good stability of formulated nanoemulsions. Phase change analyses proved the effectiveness of eicosyl alcohol to reduce subcooling to a few Kelvin. Although phase change material emulsions exhibited thermal conductivities much larger than bulk cetyl alcohol (at least 60% higher when droplets are solid), reductions in this property reached 15% when compared to water. Samples mainly showed desirable Newtonian behavior (or slight shear thinning viscosities) and modifications in density around melting transition were lower than 1.2%. In the case of phase change material nanoemulsions with 8 wt.% content of dispersed phase, enhancements in the energy storage capacity overcome 20% (considering an operational temperature interval of 10 K around solid–liquid phase change). Formulated dispersions also showed good thermal reliability throughout 200 solidification–melting cycles.
Highlights
Over last decades, the scarcity of natural energy resources and the effects of energyrelated issues, such as global warming or ozone depletion, have assumed a major role in policy agendas around the world [1]
Such multiphase colloidal structures contain bilayers made of hexagonally-packed crystals of surfactants and fatty alcohols, which give rise to a creamy texture of the sample [62], which is uninteresting for heat transfer applications
The sample composition was optimized in order to obtain phase change materials (PCMs) with small droplets, good fluidity and stability through time and after the freeze–thaw cycles
Summary
The scarcity of natural energy resources and the effects of energyrelated issues, such as global warming or ozone depletion, have assumed a major role in policy agendas around the world [1]. “Energy Roadmap 2050” is committed to reach European Union’s targets of 80–95% reduction in greenhouse gas emissions relative to 1990 levels by 2050. Meeting those objectives requires decoupling economic growth from fossil fuel-based technologies by lowering the energy consumption and fostering the transition to renewables [2,3]. Implementation and possible utilization of latent heat approaches at large scale rely on their appropriate integration in thermal facilities In this sense, phase change material nanoemulsions (PCMEs), in which PCMs are dispersed as nanometric-sized droplets in heat transfer fluids, have emerged as a promising option [7]. Since PCM emulsions exhibit fluid-like behavior (even when droplets are solid or while undergo solid–liquid transition), they can be pumped and can work as both heat transfer and storage media without an additional heat exchanger [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
