Fluid Flow and Boiling Heat Transfer in Mini Channels
01 Jan 2010-Vol. 6, pp 203-210
TL;DR: In this article, an experimental investigation is carried out for fluid flow and boiling heat transfer characteristics of mini channels with tube diameters ranging from 1-3mm to 3mm and the results reveal that there is an unmistakable effect of tube diameter on fluid friction and onset of boiling during sub cooled boiling in tubes of mini channel dimensions.
Abstract: Two phase flows in mini channels occur in many industrial applications such as electronic cooling, compact heat exchangers, compact refrigeration systems and in micro propulsion devices. Due to its significance, research on two phase flow in mini channels has become attractive. However, in recent times a controversy exists whether flow in minichannel is different from macro flow because there are still substantial disagreements among various experimental results. In the present study an experimental investigation is carried out for fluid flow and boiling heat transfer characteristics of mini channels with tube diameters ranging from 1–3mm. The tubes were made of SS with water as the working fluid. The variation in friction factor and Nusselt number with decrease in tube diameter for single phase flow was systematically studied. The point of Onset of Nucelate Boiling (ONB) was identified based on wall temperature profile. The effect of heat flux and mass flux on two phase pressure drop with three different tube diameters during sub cooled boiling were investigated. The results reveal that there is an unmistakable effect of tube diameter on fluid friction and onset of boiling during sub cooled boiling in tubes of mini channel dimensions.Copyright © 2010 by ASME
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TL;DR: In this paper, the effect of tube diameter on two-phase frictional pressure drop was investigated in circular tubes with inner diameters of 0.6, 1.2, 2.6 and 3.4 mm using air and water.
35 citations
24 citations
01 Dec 2010
TL;DR: In this article, the effect of superficial velocity of liquid and gas on elongated bubble length is experimentally studied using water and air as the working fluid inside mini channels of tube diameters less than 3mm.
Abstract: The effect of superficial velocity of liquid and gas on elongated bubble length is experimentally studied using water and air as the working fluid inside mini channels of tube diameters less than 3mm. A high speed CMOS camera is used to identify the slug length. The reduction in tube diameter results in squeezing of bubbles and thereby results in elongated bubble flow pattern distinguishing it from slug flow pattern. At low superficial gas velocities inside mini/micro channels, such pattern dominates which is the subject of interest in the present study. The experimental set-up used in this study is designed for adiabatic co-current flow of air-water mixtures in round horizontal tubes. Both the liquid and gas streams flowed separately through a bank of rota meters and Coriolis mass flow meters before entering the gas-liquid mixer. The gas-liquid mixer installed upstream of the test section (the observation zone), ensures that the two phases get thoroughly mixed before entering the test section. Flow patterns were observed and the video graphs were recorded in a computer and subsequently analyzed frame by frame with appropriate image processing technique to determine various flow regimes. The decreasing tube diameter results in the elongated bubble flow pattern over a wider range in the flow regime map of mini channels which would be of a slug flow pattern in conventional tube diameters. The region of slug flow is differentiated from elongated bubble flow based on flow visualizations. The analysis of measured length of elongated bubble acts as a good indicator for identifying the change of flow regime in mini channels.
1 citations
References
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TL;DR: In this paper, the authors measured the pressure drop for a steam and water flow inside several heated tubes at two different laboratories (Chalk River Laboratories and Ecole Polytechnique).
21 citations