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Author: search.filters.author.Sathyabhama, S.Subject: search.filters.subject.Flow boiling heat transfer

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    Numerical investigation on subcooled boiling heat transfer coefficient of water-ethanol mixture by CISCAM technique
    (Korean Society of Mechanical Engineers, 2023) Suhas, S.B.; Mangrulkar, C.K.; Umashankar, K.K.K.; Sathyabhama, S.
    The subcooled flow boiling (SFB) of a water-ethanol mixture are relevant in operating heat-dissipating devices, such as smaller catalytic reactors, electronic apparatus, and hybrid electric vehicle battery components. The operative temperature should always be at a sustainable value to evade the failure or breakdown of these heat-dissipating devices. To cool these devices, a water-ethanol mixture is used as a coolant. The forced convective as well as SFB heat transfer coefficients (HTCs) for the water-ethanol mixture are estimated numerically using the volume of fluid method in a rectangular channel with dimensions of 15 mm×15 mm×150 mm. During SFB, the liquid-vapor interaction is examined by solving the bubble void fraction (BVF). For the discretization process, the Crank-Nicholson implicit method (scheme) is used, and the convective equation for the BVF is converted to an algebraic equation. The corrector predictor equation procedure is used for solving the BVF. The thermodynamic and thermophysical parameters related to subcooled boiling are estimated upon the incorporation of the bubble void fraction (α) using the mixture rule. These parameters are then incorporated into the x-momentum equation as well as into the energy equation for finding the fluid temperature, velocity, and pressure drop values. From the estimated values of temperature, subcooled flow boiling HTC is obtained. The estimated values of HTC can predict well compared with that of empirical equations. Moreover, mass flux plays a vital role in the forced convective region, while heat flux has a crucial role in the SFB region for the improvement of HTC. © 2023, The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature.
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    Experimental investigation on flow boiling characteristics of the ethanol–water mixture in conventional channels
    (Springer Science and Business Media Deutschland GmbH, 2023) Krishnegowda, M.; Sathyabhama, S.
    The flow boiling heat transfer characteristics of the ethanol–water mixture (25%/75% by volume) and its pure constituents was experimentally investigated in conventional channels. The experiments were conducted for different ranges of mass flux, heat flux, subcooled inlet temperature and two different aspect ratios (AR). Flow patterns recorded by high-speed camera indicated that the bubble waiting and the growth period are minimum for the mixture and maximum for the ethanol, resulting in a higher heat transfer coefficient (HTC) for the mixture and lower HTC for ethanol in both the channels. For all the working fluids, high HTC was observed for the channel of AR = 1.25 in the forced convective region, whereas in the subcooled boiling region, high HTC was observed for the AR = 0.2 channel. The average subcooled HTC obtained for the 25% ethanol–water mixture was 15.75% and 38.85% higher than that of water and ethanol respectively for the AR = 0.2 channel. However, it was 18.11% and 41.2% higher than that of water and ethanol for the AR = 1.25 channel. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.