[en] In this doctoral thesis, mass transport phenomena have been analyzed. These phenomena have becomed a central aspect to study due to their wide application in different fields. In order to experimentally determine properties such as density, thermal expansion coefficient, and mass expansion coefficient, a high-pressure density meter has been setup. A calibration process has been established that relates the period of vibration of the system to the density of the fluid. The calibration parameters vary depending on the fluid being analyzed and the temperature and pressure conditions in which it is studied. The dynamic viscosity under high pressure conditions has been determined through a high pressure viscometer. The values obtained for the thermophysical properties under high pressure conditions have been compared as far as possible, with other published results, thus showing the suitability of the two installations (densimeter and high pressure viscometer). Through the thermogravitational technique used by means of the cylindrical configuration column, the thermodiffusion coefficient has been determined under high pressure conditions. The results obtained have provided the elaboration of quantitative correlations that allow determining the thermodiffusion coefficient of binary mixtures composed of normal alkanes under high pressure conditions. In collaboration with the Laboratory of Fluides Complexes et leurs Réservoirs of the University of Pau et Pays de l'Adour, the optical technique has been used to determine the molecular diffusion coefficient of two binary systems under high pressure conditions. Through the indirect method that consists of combining the results of the thermodiffusion and molecular diffusion coefficients, the effect of pressure on the Soret coefficient in binary mixtures has been analyzed.

[eu] Honako doktorego tesian, masa garraio fenomenoak aztertu dira. Arlo desberdinetan duten aplikazio zabala dela eta aztertuko garrantzitsuak diren alderdi nagusiak bilakatu dira eta. Dentsitatea, tenperatura hedapen koefizientea eta masa hedapen koefizientea bezalako propietateak esperimentalki neurtzeko, presiopean lan egiten duen dentsimetro bat egokitu da. Kalibrazio prozesu bat eratu da non sistemaren bibrazio-aldia fluidoaren dentsitatearekin lotzen duen. Kalibrazio parametroak, hau da erreferentzi fluidoak, aztertzen ari diren nahasketaren, tenperatura eta presio baldintzen arabera aldatzen dira. Presiopean lan egiteko gai den biskosimetro bat zehaztu da biskosidade dinamikoa presio altutan nehurtu ahal izateko. Presiopean lortutako propietate termofisikoetarako balioak, ahal den neurrian argitaratutako beste emaitza batzuekin alderatu dira; honen bidez bi instalazioen egokitasuna frogatu da: dentsimetroa eta presio altuko biskometroa. Konfigurazio zilindrikoaren zutabearen bidez erabilitako termograbitazio teknikari esker, termodifusio koefizientea presio altutako baldintzetan neurtu da. Lortutako emaitzek, alkano normalez osatutako nahasketen termodifusio koefizientea presio altuko egoeratan zehazten duten korrelazio kuantitatiboak garatu dira Lortutako emaitzek presio altuko baldintzetan alkano normalez osatutako nahasketa bitarreko termodifusio koefizientea zehazteko aukera ematen duten korrelazio kuantitatiboak landu dituzte. Iparraldean dagoen Pau et Pays de l'Adour unibertsitatean Fluides Complexes et leurs Réservoirs Laborategian teknika optikoa erabili da presio altuko baldintzetan bi sistema bitarrek duten difusio molekularreko koefizientea zehazteko. Termodifusioaren eta difusio molekularraren koefizienteen emaitzen konbinazioan datzan zeharkako metodoaren bidez, presioak Soret koefizientean izan duen eragina aztertu da nahasketa bitarretan.