[en] In this doctoral thesis the transport properties in ternary mixtures are analysed. The general objective of the work, is the determination of the thermodiffusion, molecular diffusion and Soret coefficients in ternary mixtures. On the one hand, we measure the thermodiffusion coefficients in both binary and ternary mixtures, by the thermogravitational technique. On the other hand, we ascertain the molecular diffusion coefficients in binary and ternary mixtures by the sliding symmetric tubes (SST) technique. The Soret coefficients in both binary and ternary mixtures are determined by the combination of the results for the thermodiffusion and molecular diffusion coefficients. In this work, we develop a new experimental methodology to determine the molecular diffusion coefficients in ternary mixtures by the SST technique. This, together with the measurement of the thermodiffusion coefficients, makes possible the determination of the Soret coefficients in ternary mixtures. Specifically, we measure these coefficients for the six compositions of the ternary mixture formed by 1,2,3,4‐Tertrahydronaphtaline (THN), Isobutylbenzene (IBB) and n‐Dodecane (nC12), related to the project DCMIX1. In addition, in the framework of this project, we have conducted the first benchmark in ternary mixtures, in collaboration with other five teams at international level. In this benchmark work each team measures the transport coefficients of the mixture THN‐IBB‐nC12 at mass fraction of 0.80‐0.10‐0.10 and at 25°C, by different experimental techniques and in different gravity conditions. The results show a good agreement in general, which comes as a great breakthrough in the study of the thermodiffusion phenomenon in ternary mixtures. In addition, we determine the thermodiffusion coefficients of the ternary mixture composed by 1‐Methylnaphtalene (MN), Toluene (Tol) and n‐Decane (nC10) at eight different compositions and at 25°C. The study of these two ternary mixtures results in a combination rule which enables the prediction of the thermodiffusion coefficients in ternary mixtures from the thermodiffusion coefficients of the corresponding binaries. Moreover, we continue with the study of binary mixtures. Specifically, we analyse 13 binary systems composed by MN, Tol and nCi (for i = 6, 8, 10, 12, 14 and 16), at 25°C. We measure the thermodiffusion coefficient of these systems at different mass fractions (77 mixtures) by the thermogravitational technique. Additionally, we determine the molecular diffusion coefficients by the SST technique for the equimass composition of these 13 binary mixtures. With the experimental results in binary mixtures, we analyse the effect of different properties of the mixtures, such as viscosity or molecular weight, on the thermodiffusion, molecular diffusion and Soret coefficients.

[eu] Tesi‐doktoretza honetan garraio propietateak aztertu dira nahasketa hirutarretan. Lanaren helburu orokorra, nahasketa hirutarretan termodifusioko, difusio molekularreko eta Soret koefizienteak zehaztea da. Alde batetik, termodifusioko koefizienteak neurtu dira teknika termograbitazionalaren bidez, nahasketa bitarretan eta hirutarretan. Bestetik, difusio molekularreko koefizienteak zehaztu dira sliding symmetric tubes (SST) teknikaren bidez, bai nahasketa bitarretan bai hirutarretan. Soret koefizienteak zehaztu dira temodifusio eta difusio molekularreko koefizienteen konbinaziotik. Tesi‐doktoretza honetan metodologia esperimental berri bat garatu da, nahasketa hirutarretan difusio molekularreko koefizienteak zehazteko SST teknikaren bidez. Honek, temodifusioko koefizienteen neurketarekin batera, Soret koefizientearen zehaztapena nahasketa hirutarretan ahalbidetu du. Konkretuki, koefiziente hauek neurtu dira DCMIX1 proiektuaren nahasketa hirutarraren sei konposaketarako. Nahasketa hau 1,2,3,4‐Tertrahidronaftalinak (THN), Isobutilbentzenoak (IBB) eta n‐Dodekanoak (nC12) osatzen dute. Gainera, proiektu honen egituran, lehenengo benchmark‐a nahasketa hirutarretan burutu da, beste bost nazioarteko taldeekin. Lan honetan, THN‐IBB‐nC12 nahasketaren garraio koefizienteak zehaztu dira 0,80‐0,10‐0,10 kontzentraziorako eta 25°C‐etan, hainbat teknika esperimentalen bitartez eta grabitate baldintza ezberdinetan. Emaitzak bat datoz, aurrerapen garrantzitsua ekarriz termodifusio fenomenoaren ikerketari. Gainera, termodifusioko koefizienteak neurtu dira 1‐Metilnaftalenoak (MN), Toluenoak (Tol) eta n‐Dekanoak (nC10) osatzen duten nahasketarako, zortzi kontzentrazio ezberdinetarako eta 25°C‐etan. Bi sistema hauen termodifusioko koefizientearen ikerketak, korrelazio berri baten garapena bideratu du. Korrelazio honek, nahasketa hirutarren termodifusioko koefizienteak, nahasketa bitarren koefizienteetatik kalkulatzea ahalbidetzen du. Bestalde, nahasketa bitarren ikerketarekin jarraitu da. Konkretuki, 13 sistema bitarrak aztertu dira, MN‐k, Tol‐k eta nCi‐k (non i = 6, 8, 10, 12, 14 eta 16) osatuta, 25°Cetan. Termodifusioko koefizienteak neurtu dira hainbat kontzentrazioetara (guztira 77 nahasketa), teknika termograbitazionalaren bitartez. Halaber, difusio molekularreko koefizienteak neurtu dira 13 sistema hauetarako, 0,50‐eko kontzentrazio masikoan. Azkenik, Soret koefizienteak zehaztu dira 13 nahasketa hauetarako. Nahasketa bitarretan lortu diren emaitza esperimentalak erabili dira nahasketen propietateek (adibidez, biskositatea edo masa molekularra) termodifusioko, difusio molekularreko eta Soret koefizienteetan daukaten eragina aztertzeko.