A Numerical Study of Quasi-Nucleate Boiling in Mini- and Micro Channels

In this paper, a numerical study of quasi-nucleate boiling in horizontal mini- and micro-channels is carried out. The numerical simulation which is based on the multiphase model of volume of fluid (VOF) method available in commercial CFD software (Fluent 6.1.18) aims to study the corresponding flow behaviors of nucleate bubbles generated from the tube walls in mini/micro channels so as to understand the surface dominated effect of micro/mini channels on nucleate bubbles and heat transfer. In the present simulation, water enters a 2D channels with a uniform velocity of 0.2m/s. In order to examine the effects of channels size on bubbles flow and heat transfer, numerical simulations for three types of rectangular channels which have the same length of 30mm but different channel height respectively at 5mm, 0.5mm and 0.2mm are carried out. To have the nucleate effect or a quasi-nucleation condition, bubbles are generated approximately by injecting a small vapour bubble timely through an inlet located on the heated wall as the nucleate centre; meanwhile a transient vapour mass flow, based on the boiling parameters, is applied to approximate the bubble growth. While, the boiling parameters used in the simulation, such as bubble frequency, departure diameter and so on, are obtained by the calculations of correlations available from previous experimental studies.