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Master's Dissertation
DOI
https://doi.org/10.11606/D.18.1998.tde-19062024-121840
Document
Author
Full name
Gherhardt Ribatski
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1998
Supervisor
Committee
Jabardo, Jose Maria Saiz (President)
Pagliuso, Josmar Davilson
Yanagihara, Jurandir Itizo
Title in Portuguese
Estudo da transferência de calor em ebulição nucleada de refrigerantes halogenados
Keywords in Portuguese
ebulição nucleada
misturas refrigerante/óleo
refrigerantes halogenados
superfícies intensificadoras
Abstract in Portuguese
A otimização do projeto de evaporadores inundados para aplicações frigoríficas requer a adequada determinação do coeficiente de transferência de calor em ebulição nucleada. Este trabalho, através da literatura aberta, visou um extenso estudo do coeficiente de transferência de calor, revelando dois tipos de correlações: (1) estritamente empíricas, baseadas no ajuste da curva à bancos de dados experimentais; (2) semi-empíricas, baseadas em modelos físicos, mas com ajuste de coeficientes numéricos aos dados experimentais. Foram verificadas significativas discrepâncias entre as correlações, refletindo o ponto de vista do autor com relação ao mecanismo físico da ebulição nucleada ou tendências particulares dos dados experimentais. Em adição à pesquisa bibliográfica, foi realizada uma análise preliminar do procedimento de Cooper com o desenvolvimento de uma correlação para refrigerantes halogenados. Esta foi determinada utilizando dois diferentes bancos de dados compostos por refrigerantes de baixa pressão, tais como R-11, R-113 e R-114. Tal procedimento, necessitou o desenvolvimento de correlações para as propriedades de transporte dos refrigerantes escritas em termos da temperatura e pressão reduzidas. Estas são caracterizadas pela simplicidade e precisão, adequando-se à diferentes refrigerantes pela simples alteração de coeficientes numéricos. Finalmente, analisou-se dois importantes aspectos na ebulição nucleada de refrigerantes: os efeitos do óleo de lubrificação do compressor e as superfícies intensificadoras da transferência de calor
Title in English
Study of nucleate pool boiling heat transfer of halogened refrigerants
Keywords in English
enhancement surfaces
halogened refrigerants
mixtures refrigerants/oil
pool boiling
Abstract in English
The optimized design of flooded evaporators for refrigeration applications requires na adequate determination of the mucleate pool boiling heat transfer coefficient of the refrigerant. This study has been focused on na extensive analysis of the aforementioned heat transfer coefficient. A literature survey has revealed two types of correlations: (1) strictly empirical, based on experimental data bank curve fitting; and (2) semi-empirical, based on physical model but with numerical coefficients fitted with experimental data. Significant discrepancies have been noted between correlations, reflecting either the point of view of the author regarding the physical mechanism of nucleate boiling or particular trends of experimental data. In addition to the literature survey , a preliminary analysis of the Coopers procedure has been performed with the development of a correlation for halogen refrigerants, based on data obtained elsewhere from two different experimental set ups involving low pressure refrigerants such as the R-11, R-113 and R-114. This procedure requires correlations of the transport properties of the refrigerants written in terms of reduced pressure and temperature. Correlations developed in this study are straightforward, accurate and fitted to different refrigerants by simply changing numerical coefficients. Finally, an analysis of two important aspects of the nucleate boiling phenomena of refrigerants has been performed, namely those related to effects on the heat tran_sfer coefficient of the compressor lubrication oleo and heat transfer enhancement devices.
 
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Publishing Date
2024-06-19
 
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