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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

VISUALIZATION EXPERIMENT AND NUMERICAL SIMULATION OF A FLAT-PLATE CLOSED LOOP TWO-PHASE THERMOSYPHON OF SMALL DIMENSIONS

Get access (open in a dialog) DOI: 10.1615/IHTC16.her.022116
pages 4489-4499

Abstract

Flat-plate closed loop two-phase thermosiphon (CLTPT) could be used as an efficient heat spreader in electronic cooling. In this paper, a visualization testing apparatus of a flat plate CLTPT with mini channels was designed and fabricated. Its two-phase flow patterns and heat transfer performances under different filling ratios and heat loads were investigated using R245fa as working fluid. The experimental results show that with the increasing of heat load the two-phase flow in the loop sequentially experiences three main typical working modes: oscillation, circulation with direction reversal, and unidirectional circulation. The higher the filling ratio, the lower the heat load required for the transition to unidirectional circulation. The total thermal resistance at first decreases and then increases with the increasing of heat load. A numerical model based on volume of fluid (VOF) method with the special consideration of thin film evaporation and condensation of annular flow and slug flow was built to explore the characteristics of two-phase flow and phase change heat transfer of CLTPT. The numerically predicted two-phase flow patterns and heat transfer performances agree fairly well with experiment in unidirectional circulation mode. The rapid increment of condensation resistance was found to be the principal cause for the deterioration of thermal performance at high heat load for the case of high filling ratios. The results obtained and the numerical methods developed in this study are helpful for the optimization of flat plate CLTPT.