Browsing by Author "Escobar, RA"

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    Methodology for predicting oxygen transport on an intravenous membrane oxygenator combining computational and analytical models
    (ASME, 2005) Guzman, AM; Escobar, RA; Amon, CH
    A computational methodology for accurately predicting flow and oxygen-transport characteristics and performance of an intravenous membrane oxygenator (IMO) device is developed, tested, and validated. This methodology uses extensive numerical simulations of three-dimensional computational models to determine flow-mixing characteristics and oxygen-transfer performance, and analytical models to indirectly validate numerical predictions with experimental data, using both blood and water as working fluids. Direct numerical simulations for IMO stationary and pulsating balloons predict flow field and oxygen transport performance in response to changes in the device length, number of fibers, and balloon pulsation frequency. Multifiber models are used to investigate interfiber interference and length effects for a stationary balloon whereas a single fiber model is used to analyze the effect of balloon pulsations on velocity and oxygen concentration fields and to evaluate oxygen transfer rates. An analytical lumped model is developed and validated by comparing its numerical predictions with experimental data. Numerical results demonstrate that oxygen transfer rates for a stationary balloon regime decrease with increasing number of fibers, independent of the fluid type. The oxygen transfer rate ratio obtained with blood and water is approximately two. Balloon pulsations show an effective and enhanced flow mixing, with time-dependent recirculating flows around the fibers regions which induce higher oxygen transfer rates. The mass transfer rates increase approximately 100% and 80%, with water and blood, respectively, compared with stationary balloon operation. Calculations with combinations of frequency, number of fibers, fiber length and diameter, and inlet volumetric flow rates, agree well with the reported experimental results, and provide a solid comparative base for analysis, predictions, and comparisons with numerical and experimental data.
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    Multi-length and time scale thermal transport using the lattice Boltzmann method with application to electronics cooling
    (PERGAMON-ELSEVIER SCIENCE LTD, 2006) Escobar, RA; Ghai, SS; Jhon, MS; Amon, CH
    The lattice Boltzmann method (LBM) is used to investigate one-dimensional, multi-length and -time scale transient heat conduction in crystalline semiconductor solids, in which sub-continuum effects are important. The implementation of this method and its application to electronic devices are described. A silicon-on-insulator transistor subject to Joule heating conditions is used as a case study to illustrate the essence of the LBM. We compare our LBM results, for the diffusive to the ballistic transport regimes, with various hierarchical methodologies of heat transport such as the Fourier, Cattaneo, and ballistic-diffusive transport equations. (c) 2005 Elsevier Ltd. All rights reserved.