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| Author(s): |
Isabela Ignácio Silva
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Ilha Solteira. 2021-09-09. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Engenharia. Ilha Solteira |
| Defense date: | 2021-08-06 |
| Advisor: | Elaine Maria Cardoso; Jeferson Diehl Oliveira |
| Abstract | |
The constant search for techniques that optimize the heat transfer process, including phase change, makes it necessary to understand the vapor bubble dynamics in the boiling process. Thus, the present work aims to study the heat transfer mechanisms and dynamics of the vapor bubble in the nucleate boiling regime by using experimental tests on a plain copper surface with an artificial cavity and analyzing the stages of growth and departure of the vapor bubble. The working fluid analyzed was HFE-7100 in saturated conditions. Aspects of the formation and growth of vapor bubbles − the diameter and frequency of bubble departure − were studied by analyzing experimental data obtained by an optical sensor and visualizing the boiling phenomenon. Besides, the present study involved the characterization of the tested surface using scanning electron microscopy (SEM) and Stereo techniques. The diameters (Dd) and frequencies (f) of bubbles obtained were compared with models and correlations found in the literature. The correlations of Lim and Bang (2020), Kim and Kim (2006) e Kutateladze and Gogonin (1979) proved to be satisfactory to predict the experimental results regarding the bubble departure diameter. Through the regression of experimental data and based on the model of Kim and Kim (2006), a correlation was proposed to predict the departure diameter of vapor bubbles for 10 ≤ Ja ≤ 90 and with a deviation lower than 1% compared to experimental data. Furthermore, an increase in the heat flux and, consequently, in the wall superheat led to an increase in the bubbles departure frequency. Optical Flow analysis identified the velocity and vorticity fields caused by micro convection − predominant heat transfer mode in nucleated boiling. (AU) | |
| FAPESP's process: | 19/13895-2 - Experimental study of vapor bubble dynamics on a surface with artificial cavities |
| Grantee: | Isabela Ignácio da Silva |
| Support Opportunities: | Scholarships in Brazil - Master |