The influence of rotating domain size in a rotating frame of reference approach for simulation of rotating impeller in a mixing vessel

This paper presents simulation of rotating impeller in a mixing vessel by means of Computational Fluid Dynamics (CFD). A special emphasis is devoted to the study of influence of the choice of numerical model for simulation of rotation of impeller when mixing a Newtonian fluid in a vessel equipped with Rushton impeller, and operating under turbulent flow conditions. In order to determine the best simulation approach experimental validation of the selected problem is done by means of Particle Image Velocimetry (PIV) system. When using the rotating frame of reference approach, the stirring vessel geometry has to be split into a stationary and rotating part, and the questionarises where to position the interface between both regions in order to avoid numerical errors, originating in numerical approximations at the interface. To answer this question, a comparison between the CFD based numerical results and experimental results, was made

Velocity-field measurements around an isolated vapour bubble over an artificially produced nucleation site using the particle image velocimetry technique

V prispevku smo podali izsledke fizikalnih meritev hitrostnega polja v območju nad zarodnim mestom, ki je dejavno med potekom mehurčastega naravno konvektivnega vrenja. Po predstavitvi temeljnih mehanizmov prenosa v preučevanem režimu vrenja smo določili vodilne cilje potekajoče raziskave, opisali merilno progo ter podali nekatere osnovne značilnosti merilne tehnike MHSSD. Opisali smo potek meritev tokovnega polja, strnili rezultate preizkusa,nato pa povzeli sklepne ugotovitve. Delo prispeva h kolikostnem vrednotenju konvektivnih učinkov med oddaljevanjem parnih mehurjev od vrelne ploščice po ločitvi od zarodnega mesta.In this paper measurements of the velocity field in the region over a nucleation site that was active during nucleate pool boiling are presented. After the presentation of the principal transport mechanisms in the investigated boiling regime the main aims of the research are defined. The experimental rig is presented and some basic features of the PIV measurement technique are described. A procedure for flow-field measurements is described,the results are presented and we conclude with final statements. Thework contributes to a quantitative determination of the convective effects during the vapour-bubble removal process on heating a wafer after departure from a nucleation site

A thermohydraulic analysis of a liquefied-petroleum-gas revaporizer

Prispevek obravnava analizo obratovanja električnega uparjalnika za ukapljeni naftni plin. Na začetku je podan opis naprave in delovanje v ustaljenih obratovalnih razmerah. Nato je definiran cilj analize in vpeljan navidez osnosimetrični povez uparjalnika. Podane so vodilne enačbe toka newtonovske tekočine v območju sekundarne kapljevine za prenos toplote in toka skozi porozni grelnik. Definirani so robni pogoji na mejah računskega območja. Ločeno so podane osnovne karakteristike enačbe za vrednotenje prenosnih pojavov v posameznih delih uparjalnika. Poseben poudarek je namenjen razmeram konvektivnega uparjanja binarne zmesi v cevni vijačni spirali. Opisan je iterativni računski postopek, s katerim je doseženo končno obratovalno stanje naprave. Na koncu so predstavljeni dobljeni rezultati s komentarjem in sklepi. Za izbrane parametre je obratovalna točka uparjalnika znotraj predpisanih temperaturnih mej.This paper deals with the thermohydraulic characteristic of an electrical liquefied-petroleum-gas (LPG) revaporizer. To begin with both the revaporizer\u27s description and its working performances are presented. The main goals of the analysis are defined and the quasi-axisymmetrical revaporizer section is introduced. The governing equations for Newtonian fluid flow in the region of the secondary liquid and for flow through a porous heater are presented. The boundary conditions on the computational region boundaries are prescribed. Further basic empirical corelations for the evolution of the transport phenomena within the individual revaporizer zones are presented. Special attention is devoted to the convective boiling process of the binary mixture in helicaly coiled tubes. The iterative calculating procedure with which we finally reached the working state of the device is explained. At the end the achieved results are discussed with comments and conclusions included.The operating point of the revaporizer was to lie inside the prescribed temperature range for the selected combination of process parameters

Sodobni adsorbenti v obliki adsorpcijskih satovij

V prispevku je opisan proces adsorpcije, s katerim lahko vežemo pline ali kapljevine na trdne snovi. Poudarek je na najnovejših adsorpcijskih napravah, kjer nasutje aktivne snovi nadomestimo s satovjem. Takšne naprave odlikuje manjši tlačni padec in možnost hitre regeneracije