98 KB3550 KB58 KB199920252007Bajcar, TomDular, MatevžHočevar, MarkoRotar, MajaSmrekar, JureŠirok, Brane15 straništevilka:5letnik:53str. 270-284ISSN:0039-2480COBISSID:10081307URN:URN:NBN:SI:doc-JIOJ57KWenslAssociation of Mechanical Engineers and Technicians of Slovenia et al.Zveza strojnih inženirjev in tehnikov Slovenije et al.Strojniški vestnikhladilni stolpinumerična analizaprenos snoviprenos toplotetermodinamične lastnostiIzboljšanje termodinamičnih lastnosti hladilnih stolpov na naravni vlek| Improvement of the thermodynamic properties in a natural-draft cooling tower|The velocity and temperature fields above droplet eliminators inside a natural-draft cooling tower of the Doel-3 powerplant (Belgium) were determined using the CTP (Cooling Tower Profiler) method. The measurements show regions of high velocities and low temperatures of air at the cooling tower circumference, leading to locally impaired heat and mass transfer. The established phenomenological relations enable the solution of this problem, which can be achieved by a variation of the fill height and the water mass-flow rate. The influence of these two parameters was analysed numerically. A 3D numerical simulation of a single-phase turbulent airflow wasperformed. Local values of the air velocity and air temperature were included in the numerical model through source terms. The numerical results present the analysis of local irregularities and their influence on the overall cooling-tower characteristics. Experimental and numerical results for the velocity and temperature fields in a cooling towerćs transverse section are presented, followed by a procedure for reducing irregularities in the cooling towerćs operation. This procedure includes the increase of the fill height and the rearrangement of the local cooling-water mass-flow rate in the cooling towerćs transverse section. In the numerical model these two parameters were modelled by a local modification of the source terms. Modifiedsource terms of the model lead to more uniform aero-thermodynamic properties in the tower and consequently to a higher cooling-tower efficiency. The paper presents a complete diagnostic method of local anomalies, based on the case of a representative Doel-3 cooling tower. The method is based on experimental and numerical modelling of the transport phenomena inside the cooling tower. It makes it possible to increase the efficiency of the cooling towerćs operation. The calculated mean heat-flux density was increased by 2.8% in this particular caseZ uporabo metode CTP (Cooling Tower Profiler) v hladilnem stolpu na naravni vlek elektrarne Doel-3 (Belgija) smo določili hitrostna in temperaturna polja zraka nad izločevalniki kapljic. Meritve so pokazale, da so na obodu prečnega prereza stolpa področja z velikimi hitrostmi in nizkimi temperaturami zraka, kar ima za posledico manjso učinkovitost v prenosu toplote in snovi. Postavljene pojavne povezave omogočajo resitev problema s spremembo visine polnila in prerazporeditvijo masnega toka vode. Vpliv omenjenih parametrov smo preverili s simulacijo. Narejena je bila trirazsezna numerična simulacija enofaznega turbulentnega toka zraka. Lokalne izmerjene vrednosti hitrosti in temperature zraka so bile v model vključene prek izvirnih členov. Rezultati prikazujejo analizo vpliva lokalnih nepravilnosti na skupno značilko hladilnega stolpa. Predstavljeni so rezultati meritev, simulacija hitrostnegain temperaturnega polja po prerezu stolpa. Podani so ukrepi za odpravo nepravilnosti v delovanju stolpa, ki vključujejo povečanje visine polnil na obodu stolpa in ustrezno prerazporeditev celotnega masnega pretoka vode po prerezu stolpa. V numeričnem modelu smo ti dve spremenljivki opisali z lokalno spremembo izvirnih členov, kar vodi k ustreznejsi porazdelitvi aerotermodinamičnih značilk in posledično k večji učinkovitosti hladilnega stolpa. Na primeru izbranega hladilnega stolpa Doel-3 je v prispevku predstavljena celovita diagnostična metoda lokalnih anomalij, ki temelji na eksperimentalnem in numeričnem modeliranju prenosnih pojavov v hladilnem stolpu. Opisana metoda omogoča povečevanje učinkovitosti delovanja hladilnih stolpov. Izračunana povprečna gostota toplotnega toka se je v tem dejanskem primeru povečala za 2,8 odstotkaTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaUniverza v Ljubljani, Fakulteta za strojništvo