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Author: search.filters.author.Suhas, B.G.Subject: search.filters.subject.Bubble departure diameter

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    Bubble dynamics of water-ethanol mixture during subcooled flow boiling in a conventional channel
    (Elsevier Ltd, 2017) Suhas, B.G.; Sathyabhama, A.
    In this paper, bubble dynamics in subcooled flow boiling of water-ethanol mixture in horizontal rectangular channels is investigated through visualization. The subcooled flow boiling heat transfer coefficient of water ethanol mixtures are determined for various heat flux, mass flux and ethanol volume fraction. A new empirical correlation is proposed to predict the heat transfer coefficient of pure water based on the parameters like heat flux, bubble departure diameter, waiting period and the growth period. Two types of bubble behaviours are observed after nucleation: (i) Sliding for a distance along the bottom wall of the channel surface before lift-off and (ii) Lift-off from the bottom wall of the channel surface without sliding. Force balance analysis is carried out to determine the reason for bubble lift-off and bubble sliding. The bubble lift-off without sliding is observed at higher ethanol volume fraction, lower heat flux and higher channel inlet temperature. The bubble sliding and lift-off are observed at higher heat flux and lower channel inlet temperature for water and water-ethanol mixture of 25% ethanol volume fraction. However, the effect of mass flux on the bubbles sliding or bubble lift-off is not significant. © 2016 Elsevier Ltd
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    Experimental investigation of heat transfer coefficient and correlation development for subcooled flow boiling of water-ethanol mixture in conventional channel
    (American Society of Mechanical Engineers (ASME) infocentral@asme.org, 2017) Suhas, B.G.
    In this present work, bubble dynamics of subcooled ?ow boiling in water-ethanol mixture is investigated through visualization using a high-speed camera in horizontal rectangular channels. The heat transfer coef?cient of water-ethanol mixture during subcooled ?ow boiling is determined for various parameters like heat ?ux, mass ?ux, and channel inlet temperature. The effect of bubble departure diameter on heat transfer coef?cient is discussed. A correlation is developed for subcooled ?ow boiling Nusselt number of water-ethanol mixture. The parameters considered for correlation are grouped as dimensionless numbers by Buckingham p-theorem. The present correlation is compared with the experimental data. The mean absolute error (MAE) of Nusselt number of water-ethanol mixture calculated from the experimental data and those predicted from the present correlation is 10.39%. The present correlation is also compared with the available literature correlations developed for water. The MAE of Nusselt number of water predicted from the present correlation and those predicted with Papel, Badiuzzaman, Moles-Shaw, and Baburajan correlations is 41%, 19.61%, 29.9%, and 43.1%, respectively.  © 2017 by ASM.
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    Heat transfer and force balance approaches in bubble dynamic study during subcooled flow boiling of water–ethanol mixture
    (Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2018) Suhas, B.G.; Sathyabhama, A.
    In this paper, the subcooled flow boiling heat transfer coefficient of pure water, water–ethanol mixture and pure ethanol is determined experimentally in horizontal rectangular channels for various parameters like heat flux, mass flux and channel inlet temperatures. Flow visualization is carried out using high speed camera. The bubble departure diameter, growth period and waiting period of bubbles are determined. Correlations are developed for subcooled flow boiling Nusselt number of water–ethanol mixture based on force balance approach and heat transfer approach. The parameters considered for correlation are grouped as dimensionless numbers by Buckingham ?-theorem. The significance of each dimensionless number on heat transfer coefficient is discussed. The correlations developed for subcooled flow boiling heat transfer coefficient are validated with the experimental data. They are found to be in good agreement with the experimental data. It is found that the correlation based on force balance approach predicts the subcooled flow boiling Nusselt number well when compared with that of heat transfer approach correlation. © 2017 Taylor & Francis.