A theoretical and experimental study on flow boiling heat transfer and critical heat flux in microchannels

Author(s)

Cristiano Bigonha Tibiriçá

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2011-07-13

Examining board members

Gherhardt Ribatski; Jorge Luis Baliño; Jader Riso Barbosa Junior; Paulo Seleghim Junior; Jurandir Itizo Yanagihara

• Advisor: Gherhardt Ribatski

Abstract

This research comprises an experimental and theoretical study on flow boiling heat transfer and critical heat flux inside small diameter tubes based on data obtained in experimental facilities specially designed for this purpose. A broad literature review was carried out and the main methods to predict the heat transfer coefficient, critical heat flux and flow patterns were pointed out. The experimental results were parametrically analyzed and compared against the predictive methods from literature. For the first time, microchannels experimental results obtained by an unique researcher in distinct laboratories were compared and a reasonable agreement was observed. The importance of such a comparison is high-lighted for flow boiling inside microchannels due to the high discrepancies ob-served when results from independent laboratories obtained under similar experimental conditions are compared. Moreover, the experimental results obtained in the present study were used to develop correlations and models for the heat transfer coefficient and heat flux that takes into account the flow patterns observed in microchannels. The heat transfer coefficient and critical heat flux models were developed based on mechanistic approach. In addition, criteria to characterize macro to microchannel transition were proposed based in the occurrence of the stratified flow pattern and the liquid film symmetry under annular flow conditions. (AU)

• FAPESP's process: 07/53950-5 - A theoretical and experimental study on flow boiling heat transfer and critical heat flux in microchannels
• Grantee: Cristiano Bigonha Tibirica
• Support Opportunities: Scholarships in Brazil - Doctorate