Sateesh Gedupudi

Bio: Sateesh Gedupudi is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Heat transfer coefficient & Heat transfer. The author has an hindex of 10, co-authored 50 publications receiving 412 citations. Previous affiliations of Sateesh Gedupudi include Brunel University London.

Modelling pressure fluctuations during flow boiling in microchannels with inlet compressibility and resistance

Abstract: Confined bubble growth during flow boiling at low pressures in microchannels generates pressure fluctuations that may cause transient flow reversals that disturb the flow distribution in heat sinks formed of parallel channels joined by plena. A simple model is developed for the effects of upstream compressibility and flow resistance at the channel inlet on the magnitude of the pressure transient during the growth of one bubble in a single channel. Preliminary results are presented.

Effects of interplay of nanoparticles, surfactants and base fluid on the interfacial tension of nanocolloids

Abstract: A systematically designed study has been conducted to understand and clearly demarcate the degree of contribution by the constituting elements to the surface tension of nanocolloids. The effects of elements such as surfactants, particles and the combined effects of these on the interfacial tension of these complex fluids are studied employing pendant drop shape analysis method by fitting Young Laplace equation. Only particle has shown considerable increase in surface tension with particle concentration in a polar medium like DI water whereas only marginal effect particles on surface tension in weakly polar mediums like glycerol and ethylene glycol. Such behaviour has been attributed to the enhanced desorption of particles to the interface and a mathematical framework has been derived to quantify this. Combined particle and surfactant effect on surface tension of complex nanofluid system showed a decreasing behaviour with respect to the particle and surfactant concentration with a considerably feeble effect of particle concentration. This combined colloidal system recorded a surface tension value below the surface tension of aqueous surfactant system at the same concentration, which is a counterintuitive observation as only particle results in increase in surface tension and only surfactant results in decrease in surface tension. The possible physical mechanism behind such an anomaly happening at the complex fluid air interface has been explained. Detailed analyses based on thermodynamic, mechanical and chemical equilibrium of the constituents and their adsorption-desorption characteristics as extracted from Gibbs adsorption analysis has been provided.

Numerical Simulation and Experimental Observations of Confined Bubble Growth During Flow Boiling in a Microchannel With Rectangular Cross-Section of High Aspect Ratio

Abstract: Bubble nucleation and growth to confinement during flow boiling in microchannels lead to high heat transfer coefficients. They may also create pressure fluctuations that change the superheat driving evaporation and cause flow reversals that promote transient dry-out and uneven distribution of flow between parallel channels. The work described in this paper is part of a programme to develop models for these processes that will aid the design of evaporative cooling systems for devices operating at high heat fluxes. Video observations of water boiling in a single copper channel of rectangular cross-section, 0.38 × 1.6 mm and a heated length 40 mm, were performed. The top side of the channel was a glass window. Results are presented for a heat flux, averaged over the area of the three metal sides, of 210 and 173 W/m2 K for incompressible and compressible inlet flow conditions. The inlet pressure was about 1.12 bar and the mass flux was 747.5 kg/m2 s for both conditions examined. The results demonstrated the strong influence of compressibility on the mode of bubble detachment and growth and therefore on flow patterns, pressure fluctuations and heat transfer rates. The fluid mechanics of boiling in this size channel were also successfully investigated by 3-D numerical simulation for bubbles growing at a defined rate with a fixed inlet flow rate using the 3-D CFD code FLUENT 6 (no upstream compressibility). The study examined the fluid mechanics of bubble motion with heat transfer, but the mass transfer across the bubble-liquid interface was not simulated in the present work. A small vapour bubble was injected at the wall to ensure the bubble generation is under a quasi nucleation condition. Its growth was driven by an internal source of vapour, at a rate derived by analysis of the experimental measurements of growth. The simulation reproduced well the observed motion and shape of the bubble. The simulation was then extended to model bubbles generated and growing randomly in a 2-D channel.Copyright © 2009 by ASME