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S.V. Prabhu

Bio: S.V. Prabhu is an academic researcher from Indian Institute of Technology Bombay. The author has contributed to research in topics: Heat transfer & Nusselt number. The author has an hindex of 31, co-authored 168 publications receiving 3766 citations. Previous affiliations of S.V. Prabhu include Nokia & Indian Institutes of Technology.


Papers
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TL;DR: In this article, the effect of geometrical parameters on the performance of the rotors in terms of coefficient of static torque, coefficient of torque and coefficient of power was investigated in an open jet wind tunnel.

295 citations

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TL;DR: In this article, the effect of jet-to-plate spacing and Reynolds number on the local heat transfer distribution to normally impinging submerged circular air jet on a smooth and flat surface was investigated.

277 citations

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TL;DR: In this paper, a helical Savonius rotor with a twist of 90° was proposed to decrease the variation in static torque from 0° to 360°, and the performance of the helical rotor with and without shaft was compared in an open jet wind tunnel.

258 citations

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TL;DR: In this paper, the optimal position of the deflector plate upstream to the water flow was investigated to find out the maximum power generated by a Savonius rotor with water as the working medium at a Reynolds number of 1.32 × 10 5.

241 citations

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TL;DR: The tangential momentum accommodation coefficient (TMAC) as discussed by the authors is the boundary condition for flow of gases in the slip and transition flow regimes, and its precise determination is important for several other applications as well.
Abstract: The value of tangential momentum accommodation coefficient (TMAC) is required while prescribing the boundary condition for flow of gases in the slip and transition flow regimes. The precise determination of its value is important for several other applications as well. This article reviews the experimental techniques employed by researchers over the decades to measure this coefficient and the values reported in the literature, with relevance to calculation of the slip velocity. The review shows that the value of TMAC is dependent on a number of parameters including nature of the gas, pressure of the gas, material of the surface, surface cleanliness and roughness, and surface temperature. For monatomic gases, the TMAC at about 0.93 is almost constant with respect to the Knudsen number, and this value can be employed for most commonly available surface materials. However, for nonmonatomic gases, TMAC decreases with an increase in Knudsen number; a correlation of TMAC with Knudsen number for this class of ga...

201 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, a pressure-dependent permeability function, referred to as the APF, was proposed for ultra-tight porous media, where the matrix pore network is composed of nanometre-to-micrometre-size pores.
Abstract: We study the gas flow processes in ultra-tight porous media in which the matrix pore network is composed of nanometre- to micrometre-size pores. We formulate a pressure-dependent permeability function, referred to as the apparent permeability function (APF), assuming that Knudsen diffusion and slip flow (the Klinkenberg effect) are the main contributors to the overall flow in porous media. The APF predicts that in nanometre-size pores, gas permeability values are as much as 10 times greater than results obtained by continuum hydrodynamics predictions, and with increasing pore size (i.e. of the order of the micrometre), gas permeability converges to continuum hydrodynamics values. In addition, the APF predicts that an increase in the fractal dimension of the pore surface leads to a decrease in Knudsen diffusion. Using the homogenization method, a rigorous analysis is performed to examine whether the APF is preserved throughout the process of upscaling from local scale to large scale. We use the well-known pulse-decay experiment to estimate the main parameter of the APF, which is Darcy permeability. Our newly derived late-transient analytical solution and the late-transient numerical solution consistently match the pressure decay data and yield approximately the same estimated value for Darcy permeability at the typical core-sample initial pressure range and pressure difference. Other parameters of the APF may be determined from independent laboratory experiments; however, a pulse-decay experiment can be used to estimate the unknown parameters of the APF if multiple tests are performed and/or the parameters are strictly constrained by upper and lower bounds.

479 citations

Journal ArticleDOI
TL;DR: In this paper, the performance, blade design, control and manufacturing of horizontal axis and vertical axis wind turbines are reviewed based on experimental and numerical studies and lessons learnt from various studies/countries on actual installation of small wind turbines were presented.
Abstract: Meeting future world energy needs while addressing climatic changes has led to greater strain on conventional power sources. One of the viable sustainable energy sources is wind. But the installation large scale wind farms has a potential impact on the climatic conditions, hence a decentralized small scale wind turbines is a sustainable option. This paper presents review of on different types of small scale wind turbines i.e., horizontal axis and vertical axis wind turbines. The performance, blade design, control and manufacturing of horizontal axis wind turbines were reviewed. Vertical axis wind turbines were categorized based on experimental and numerical studies. Also, the positioning of wind turbines and aero-acoustic aspects were presented. Additionally, lessons learnt from various studies/countries on actual installation of small wind turbines were presented.

383 citations

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TL;DR: In this paper, the authors present a review on the performance of Savonius wind turbines and present relevant information about their performance, bringing a discussion about the performance and benefits of using this type of turbines.
Abstract: This paper presents a review on the performance of Savonius wind turbines. This type of turbine is unusual and its application for obtaining useful energy from air stream is an alternative to the use of conventional wind turbines. Simple construction, high start up and full operation moment, wind acceptance from any direction, low noise and angular velocity in operation, reducing wear on moving parts, are some advantages of using this type of machine. Over the years, numerous adaptations for this device were proposed. The variety of possible configurations of the rotor is another advantage in using such machine. Each different arrangement of Savonius rotor affects its performance. Savonius rotor performance is affected by operational conditions, geometric and air flow parameters. The range of reported values for maximum averaged power coefficient includes values around 0.05–0.30 for most settings. Performance gains of up to 50% for tip speed ratio of maximum averaged power coefficient are also reported with the use of stators. Present article aims to gather relevant information about Savonius turbines, bringing a discussion about their performance. It is intended to provide useful knowledge for future studies.

337 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented dynamic behavior and simulation results in a stand-alone hybrid power generation system of wind turbine, microturbine, solar array and battery storage.

300 citations

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TL;DR: In this article, the evolution of infrared (IR) thermography into a powerful optical tool that can be used in complex fluid flows to either evaluate wall convective heat fluxes or investigate the surface flow field behavior.
Abstract: This paper deals with the evolution of infrared (IR) thermography into a powerful optical tool that can be used in complex fluid flows to either evaluate wall convective heat fluxes or investigate the surface flow field behavior. Measurement of convective heat fluxes must be performed by means of a thermal sensor, where temperatures have to be measured with proper transducers. By correctly choosing the thermal sensor, IR thermography can be successfully exploited to resolve convective heat flux distributions with both steady and transient techniques. When comparing it to standard transducers, the IR camera appears very valuable because it is non-intrusive, it has a high sensitivity (down to 20 mK), it has a low response time (down to 20 μs), it is fully two dimensional (from 80 k up to 1 M pixels, at 50 Hz) and, therefore, it allows for better evaluation of errors due to tangential conduction within the sensor. This paper analyses the capability of IR thermography to perform convective heat transfer measurements and surface visualizations in complex fluid flows. In particular, it includes the following: the necessary radiation theory background, a review of the main IR camera features, a description of the pertinent heat flux sensors, an analysis of the IR image processing methods and a report on some applications to complex fluid flows, ranging from natural convection to hypersonic regime.

277 citations