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Vasudevan Raghavan

Bio: Vasudevan Raghavan is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Combustion & Laminar flow. The author has an hindex of 17, co-authored 130 publications receiving 1051 citations. Previous affiliations of Vasudevan Raghavan include University of Nebraska–Lincoln & Indian Institutes of Technology.


Papers
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Journal ArticleDOI
TL;DR: Yang et al. as discussed by the authors developed a comprehensive axisymmetric numerical model to study high pressure droplet evaporation and validated it against the most extensive microgravity experimental data available in the literature.
Abstract: A comprehensive axisymmetric numerical model has been developed to study high pressure droplet evaporation. In this model, high pressure transient effects, variable thermo-physical properties and inert species solubility in the liquid-phase are considered. First, the axisymmetric model has been utilized to explain the discrepancy between theoretical and experimental results on microgravity droplet evaporation that has been reported in the literature [J.R. Yang and S.C. Wong, Ref. 35]. In addition, this effort led to a thorough validation of the model against the most extensive microgravity experimental data available in the literature on droplet evaporation. Second, the validated model has been utilized to investigate spherically symmetric droplet evaporation for a wide range of ambient pressures and temperatures. The predictions show that the average droplet evaporation constant decreases with ambient pressure at sub-critical ambient temperatures, becomes insensitive to pressure at ambient temperatures a...

6 citations

Journal ArticleDOI
TL;DR: In this paper, the time dependent performance of extended surfaces subjected to fouling is addressed, where fins are used for augmenting boiling heat transfer, the interaction of local values of temperature excess, fouling resistance and surface characteristics of the deposit can be quite complex.
Abstract: The time dependent performance of extended surfaces subjected to fouling is addressed in this work. Where fins are used for augmenting boiling heat transfer, the interaction of local values of temperature excess, fouling resistance and surface characteristics of the deposit can be quite complex. Taking typical asymptotic fouling growth parameters from literature for reverse solubility salts, three kinds of fin geometry are analysed – rectangular, triangular and annular. For various values of the fin parameter mL, the temperature distribution and variation of fouling resistance are obtained as a function of time. To interpret the performance of a fouled fin, a new term `cleanliness efficiency' is introduced. The necessity of choosing an optimal value of mL for the fin is also highlighted here. It is shown that for all three fin configurations, cleanliness efficiency differs little, thus simplifying the geometry dependence. The approach set out in this work will help in the design of finned heat exchangers subjected to fouling and thereby minimise their overdesign.

6 citations

Journal ArticleDOI
TL;DR: In this article, a detailed numerical study of laminar cross-flow non-premixed methane-air flames in the presence of a square cylinder is presented, where flow, temperature, species and reaction fields have been predicted using a comprehensive transient three-dimensional reacting flow model with detailed chemical kinetics and variable thermo-physical properties.
Abstract: A knowledge of flame stability regimes in the presence of cylindrical bluff-bodies of various dimensions is essential to design non-premixed burners. The reacting flow field in such cases is reported to be three-dimensional and unsteady. In the literature, only a few experimental investigations with limited measurements are available. Therefore, in this work, a detailed numerical study of laminar cross-flow non-premixed methane–air flames in the presence of a square cylinder is presented. The flow, temperature, species and reaction fields have been predicted using a comprehensive transient three-dimensional reacting flow model with detailed chemical kinetics and variable thermo-physical properties, in order to get a good insight into the flame stabilisation phenomena. Further, analyses of quantities such as local equivalence ratio, cell Damkohler number, species velocity, net consumption rate of methane, which are not easily obtained through experiments even with detailed diagnostics, have been carried ou...

6 citations

Journal ArticleDOI
TL;DR: In this article, experimental and numerical analyses to investigate the thermal control of an innovative vortex tube based polymerase chain reaction (VT-PCR) thermocycler are described, and two-dimensional numerical simulations have been carried out using computational fluid dynamics (CFD) software FLUENT v.6.2.16.
Abstract: In this article, experimental and numerical analyses to investigate the thermal control of an innovative vortex tube based polymerase chain reaction (VT-PCR) thermocycler are described. VT-PCR is capable of rapid DNA amplification and real-time optical detection. The device rapidly cycles six 20μl 96bp λ-DNA samples between the PCR stages (denaturation, annealing, and elongation) for 30cycles in approximately 6min. Two-dimensional numerical simulations have been carried out using computational fluid dynamics (CFD) software FLUENT v.6.2.16. Experiments and CFD simulations have been carried out to measure/predict the temperature variation between the samples and within each sample. Heat transfer rate (primarily dictated by the temperature differences between the samples and the external air heating or cooling them) governs the temperature distribution between and within the samples. Temperature variation between and within the samples during the denaturation stage has been quite uniform (maximum variation a...

6 citations

Journal ArticleDOI
TL;DR: In this paper, the characteristics of laminar cross-flow methane-air diffusion flames in the presence of bluff bodies have been analyzed by using a high-definition digital camera.

6 citations


Cited by
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Book ChapterDOI
30 Dec 2011
TL;DR: This table lists the most common surnames in the United States used to be Anglicised as "United States", then changed to "United Kingdom" in the 1990s.
Abstract: OUTPU T 29 OUTPU T 30 OUTPU T 31 OUTPU T 32 OUTPU T 25 OUTPU T 26 OUTPU T 27 OUTPU T 28 OUTPU T 21 OUTPU T 22 OUTPU T 23 OUTPU T 24 OUTPU T 17 OUTPU T 18 OUTPU T 19 OUTPU T 20 OUTPU T 13 OUTPU T 14 OUTPU T 15 OUTPU T 16 OUTPU T 9 OUTPU T 10 OUTPU T 11 OUTPU T 12 OUTPU T 5 OUTPU T 6 OUTPU T 7 OUTPU T 8 OUTPU T 1 OUTPU T 2 OUTPU T 3 OUTPU T 4 29 30 31 32 25 26 27 28 21 22 23 24 17 18 19 20 13 14 15 16 9

1,662 citations

Journal ArticleDOI
TL;DR: In this paper, an attempt has been made to review the different approaches and techniques used to generate biodiesel from Jatropha curcas oil and the main factors affecting the biodiesel yield, for example the molar ratio of alcohol to oil, catalyst concentration, reaction temperature and reaction time are discussed.
Abstract: The demand for petroleum has risen rapidly due to increasing industrialization and modernization of the world. This economic development has led to a huge demand for energy, where the major part of that energy is derived from fossil sources such as petroleum, coal and natural gas. However, the limited reserve of fossil fuel has drawn the attention of many researchers to look for alternative fuels which can be produced from renewable feedstock. Biodiesel has become more attractive because of its environmental benefits and it is obtained from renewable resources. There are four primary methods to make biodiesel: blending, microemulsion, pyrolysis and transesterification. The most commonly used method is the transesterification of triglycerides (vegetable oil and animal fats) with alcohol in the presence of a catalyst. There is a growing interest in using Jatropha curcas L. oil as the feedstock for biodiesel production because it is non-edible and thus does not compromise the edible oils, which are mainly used for food consumption. Non-edible oils are not suitable for human consumption because of the presence of toxic components. Further, J. curcas L. seed has a high content of oil and the biodiesel produced has similar properties to that of petroleum-based diesel. In this paper, an attempt has been made to review the different approaches and techniques used to generate biodiesel from Jatropha curcas oil. The main factors affecting the biodiesel yield, for example the molar ratio of alcohol to oil, catalyst concentration, reaction temperature and reaction time are discussed. Lastly, the environmental considerations and economic aspects of biodiesel are also addressed.

524 citations

Journal ArticleDOI
Yanan Gan1, Li Qiao1
TL;DR: In this article, burning characteristics of fuel droplets containing nano and micron-sized aluminum particles were investigated, and five distinctive stages (preheating and ignition, classical combustion, microexplosion, surfactant flame, and aluminum droplet flame) were identified.

324 citations

01 Apr 1997
TL;DR: A detailed chemical kinetic model has been used to study dimethyl ether (DME) oxidation over a wide range of conditions, such as jet-stirred reactor (JSR) at I and 10 atm, 0.2 < 0 < 2.5, and 800 < T < 1300 K.
Abstract: A detailed chemical kinetic model has been used to study dimethyl ether (DME) oxidation over a wide range of conditions. Experimental results obtained in a jet-stirred reactor (JSR) at I and 10 atm, 0.2 < 0 < 2.5, and 800 < T < 1300 K were modeled, in addition to those generated in a shock tube at 13 and 40 bar, 0 = 1.0 and 650 :5 T :5 1300 K. The JSR results are particularly valuable as they include concentration profiles of reactants, intermediates and products pertinent to the oxidation of DME. These data test the Idnetic model severely, as it must be able to predict the correct distribution and concentrations of intermediate and final products formed in the oxidation process. Additionally, the shock tube results are very useful, as they were taken at low temperatures and at high pressures, and thus undergo negative temperature dependence (NTC) behavior. This behavior is characteristic of the oxidation of saturated hydrocarbon fuels, (e.g. the primary reference fuels, n-heptane and iso- octane) under similar conditions. The numerical model consists of 78 chemical species and 336 chemical reactions. The thermodynamic properties of unknown species pertaining to DME oxidation were calculated using THERM.

280 citations

Journal ArticleDOI
15 May 2017-Fuel
TL;DR: The most recent developments in the modelling of heating and evaporation of fuel droplets, the results of which were published in 2014-2017, are reviewed, and the most important unsolved problems are identified.

267 citations