The present work reports the findings from an experimental study on the effect of bypass inlet on the performance of flow boiling of water in a copper mini/micro-channel of dimension 2.5 mm wide x 0.6 mm deep x 25 mm long. The mass fluxes considered were 430 kg/m2 s, 640 kg/m2 s and 850 kg/m2 s and the heat flux was in the range 87–548 kW/m2. The results show a significant increase in heat transfer coefficient with the increase in bypass ratio for the subcooled boiling conditions and the enhancement decreases with the increase in the exit quality. An increase in pressure drop was also noticed due to the bypass inlet. The study indicates potential for further investigation and optimization. © 2019 Elsevier Ltd

Sateesh Gedupudi

Department of Mechanical Engineering

Drops

Heat flux

Heat transfer

Pressure drop

Exit qualities

Experimental investigations

Flow boiling

Flow boiling of water

INCREASE IN PRESSURE

MINI/MICRO-CHANNEL

On flow

Sub-cooled boiling

Bypass ratio

Fulltext

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IIT Madras

International Communications in Heat and Mass Transfer

Experiments were carried out to investigate the effect of surface characteristics on flow boiling heat transfer and pressure drop in a microchannel using degasified and deionized water as the working fluid. Test section consists of a 40 mm long, 0.5 mm wide and 0.24 mm deep microchannel machined in copper. Experimental results are reported for three different surface characteristics – fresh machined surface (case-1), the same channel surface when aged after repeated experimentation (case-2) and the surface obtained after cleaning the same aged surface with 0.1 M hydrochloric acid (case-3). Parameters considered include inlet temperature 95 °C, mass flux from 1000 to 2220 kg/m2 s and heat flux from 400 to 1200 kW/m2. Single-phase experiments have been performed to estimate the heat loss from microchannel and also to validate the experimental setup. The results indicate that the boiling heat transfer performance of case-2 is lower than that of case-1 and the performance of case-3 is higher than that of case-1. The main reason behind the reduction of two-phase heat transfer coefficient for case-2 as compared to case-1 is attributed to the increased wettability due to the thermal oxidation of the heating surface caused by the repeated experimentation. The enhanced boiling performance of case-3 is attributed to the increased nucleation site density. However, the change in the two-phase pressure drop is relatively small. The experimental results were compared with the available correlations in the literature to check the predictability of the correlations for the three cases. The degree of agreement (or disagreement) varies depending on the correlation and the surface characteristic. The reasons for the deviations are discussed. © 2018 Elsevier Ltd

International Journal of Heat and Mass Transfer

Influence of heating surface characteristics on flow boiling in a copper microchannel: Experimental investigation and assessment of correlations

An overview of passive techniques for heat transfer augmentation in microchannel heat sink

Hydrothermal performance of microchannel heat sink: The effect of channel design

International Journal of Thermal Sciences

Bubble dynamics and flow boiling characteristics in three different microchannel configurations

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Experimental investigation of the effect of bypass inlet on flow boiling in a mini/micro-channel

Journal	Data powered by TypesetInternational Communications in Heat and Mass Transfer
Publisher	Data powered by TypesetElsevier Ltd
ISSN	07351933
Open Access	Yes