Berger Bioucas FE, Koller TM, Fröba AP (2024)
Publication Language: English
Publication Type: Journal article, Original article
Publication year: 2024
Book Volume: 232
Article Number: 125901
DOI: 10.1016/j.ijheatmasstransfer.2024.125901
In continuation of a previous study, the objective of the present work is to deepen the understanding of the effective thermal conductivity of microemulsions. Here, the focus is to analyze how the effective thermal conductivity is influenced by variations in temperature and concentration, which result in variations in the morphology of the dispersed phase represented by micelles. For this purpose, a microemulsion system consisting of water, n-decane, and the non-ionic surfactant n-decyltetraoxyethylene (C10E4) was investigated from (283 to 313) K over a broad composition range in the water-rich and oil-rich regions as well as in the region with equal volumes of water and oil. The results of the effective kinematic viscosity from capillary viscometry and the translational diffusion coefficient of the micelles from dynamic light scattering suggest that small changes in the temperature and composition lead to distinct changes in the microemulsion structure. It is demonstrated that in all studied regions, the effective thermal conductivity determined with a steady-state guarded parallel-plate instrument in an absolute way with expanded uncertainties of about 2 % is not significantly affected by a variation in temperature at a defined composition. The effective thermal conductivity increases or decreases with increasing volume fraction of the dispersed water or n-decane phase up to about 0.11. This behavior is well represented by the Hamilton-Crosser model assuming spherical micelles. Such agreement is not given for the region with same volumes of water and n-decane, where an inversion of the continuous and dispersed phases takes place and pronounced deviations from spherical micelles are present. Here, the average values of the effective thermal conductivities calculated from a serial and a parallel resistance model and, in particular, the co-continuous model of Wang et al. can describe the measurement results reasonably well.
APA:
Berger Bioucas, F.E., Koller, T.M., & Fröba, A.P. (2024). Effective thermal conductivity, effective viscosity, and particle diffusion coefficient of microemulsions consisting of water, n-decane, and a non-ionic surfactant in different regions of the phase diagram. International Journal of Heat and Mass Transfer, 232. https://doi.org/10.1016/j.ijheatmasstransfer.2024.125901
MLA:
Berger Bioucas, Francisco E., Thomas Manfred Koller, and Andreas Paul Fröba. "Effective thermal conductivity, effective viscosity, and particle diffusion coefficient of microemulsions consisting of water, n-decane, and a non-ionic surfactant in different regions of the phase diagram." International Journal of Heat and Mass Transfer 232 (2024).
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