Značilnice vrelnega procesa na bifilnih površinah

doktorsko delo

Jure Voglar (Author), Iztok Golobič (Mentor)

Abstract

Vrenje je zaradi kompleksne interakcije vplivnih parametrov še vedno slabo razumljen mehanizem prenosa toplote. Iz tega razloga se raziskovalci trudimo na podlagi eksperimentalnih opazovanj pridobiti jasnejši vpogled v naravo samega procesa. Oblikovane značilnice vrelnega procesa, ki izhajajo iz populacije izmerjenih temperaturnih polj grelne površine, nam dajejo podrobnejši vpogled v vrelno dogajanje tako na integralnem kot tudi na lokalnem nivoju. Oblike porazdelitev temperatur grelne površine in njihove vrednosti populacijskih parametrov nam na integralnem nivoju podajajo pomembne informacije o učinkovitosti vrelnega procesa. Na lokalni ravni pa smo z analizo aktivnih nukleacijskih mest lahko ovrednotili prispevka k temperaturam in gostotam prenesenega toplotnega toka tako v času čakanja kot tudi v času rasti in odtrganja mehurčka. Značilnice vrelnega procesa nam omogočajo analizo vrelnega dogajanja tako na homogenih kot tudi na bifilnih oziroma selektivno lasersko teksturiranih grelnih površinah. Lasersko teksturirana območja so superhidrofilna in imajo prisotne jamice na mikrometrski velikostni skali. Te mikrojamice v skladu z nukleacijkim kriterijem služijo kot aktivna nukleacijska mesta. Pokazali smo, da je optimalna perioda med lasersko teksturiranimi deli površine grelnika pri vrenju vode enaka njeni kapilarni dolžini. Oblikovane bifilne grelne površine nam omogočajo izboljšan prenos toplote v primerjavi z neobdelanimi površinami grelnikov.

Keywords

disertacije;mehurčkasto vrenje v bazenu;izboljšan prenos toplote;bifilne površine;infrardeča termografija;kapilarna dolžina;značilnice vrelnega procesa;

Data

Language:	Slovenian
Year of publishing:	2019
Typology:	2.08 - Doctoral Dissertation
Organization:	UL FS - Faculty of Mechanical Engineering
Publisher:	[J. Voglar]
UDC:	542.467:536.24:544.344.016.2(043.3)
COBISS:	16820507
Views:	776
Downloads:	241
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Characteristics of boiling process on biphilic surfaces
Secondary abstract:	Due to the complex interaction of the influential parameters, the boiling process is still poorly understood mechanism of heat transfer. For this reason, researchers are trying to gain a clearer insight into the nature of the process on the basis of experimental observations. The characteristics of boiling process arising from the population of the measured temperature fields of the heater surface give us a more detailed insight into the boiling process both at the integral and the local level. Shapes of the heater wall-temperature distributions and their values of the population parameters give us an important level of information on the efficiency of the boiling process at the integral level. At the local level, by analyzing active nucleation sites, the contribution to the temperatures and heat fluxes both during the waiting time and during the growth and bubble detachment time was evaluated. Characteristics of boiling process enable us to analyze the boiling process both on homogeneous as well as on biphilic or selective laser-textured heater surfaces. Laser textured areas are superhydrophilic and have cavities with diameters on a micrometric level. These micro-cavities, in accordance with the nucleation criterion, serve as active nucleation sites. We have shown that the optimum period between the laser-textured parts of the heater surface during boiling of water is equal to its capillary length. The biphilic heater surfaces enhance the boiling heat transfer compared to the untreated heater surfaces.
Secondary keywords:	dissertations;nucleate pool boiling;enhanced heat transfer;biphilic surfaces;infrared thermography;capillary length;characteristics of boiling process;
Type (COBISS):	Doctoral dissertation
Study programme:	0
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Fak. za strojništvo
Pages:	XXVIII, 133 str.
ID:	11234383