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THERMAL SCIENCE
International Scientific Journal
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NUMERICAL STUDY OF FLOW BOILING IN INCLINED LARGE LENGTH-DIAMETER MICROCHANNELS
ABSTRACT
The present study aims to numerically investigate the impact of inclination angle on the boiling heat transfer and pressure drop in rectangular micro-channel tubes with a large length-diameter ratio. The volume of fluid approach was utilized to model the two-phase flow in micro-channels using the CFD method. The effects of different inclination angles, aspect ratio and Reynolds number on heat transfer and pressure drop characteristics are analyzed by simulation. According to the latent heat percentage and saturation temperature differential, the mass transfer factor was calculated using the Lee model, which describes the mass and energy transfer throughout the boiling process. The convective heat transfer coefficients of the walls of structures at angles ranging from 0° to 90° (aspect ratios of 1.271, 1.017 and 0.763, respectively) were analyzed. It was found that with the decrease of aspect ratios, the convective heat transfer coefficients decreased by 16.64% and 11.56%, respectively. In order to keep the evaporator outlet superheat within 5°C, the inlet Reynolds number should not be lower than 3000. The study offers insightful information for designing and refining micro-channel evaporators in refrigeration systems, particularly for horizontal freezers with specific inclination angle arrangements.
KEYWORDS
large length-diameter ratio, inclination angle, aspect ratio, low-mass flow rate, CFD simulation, Flow Boiling Heat Transfer
PAPER SUBMITTED: 2025-04-06
PAPER REVISED: 2025-06-24
PAPER ACCEPTED: 2025-07-09
PUBLISHED ONLINE: 2025-08-02
DOI REFERENCE: https://doi.org/10.2298/TSCI250406142H
CITATION EXPORT: view in browser or download as text file
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© 2026 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence