01758nas a2200181   4500008004100000022001400041245007500055210006900130260007100199300001400270490000700284520108000291100003001371700002101401700002301422700002201445856010901467       2009                        eng d  a0888-588500aSolid suspension and liquid phase mixing in solid-liquid stirred tanks0 aSolid suspension and liquid phase mixing in solidliquid stirred   a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcNOV  a9713-97220 v483 a<p>Stirred tanks are widely used in chemical process industries for catalytic reactions, dissolution of solids, crystallization, and so oil. In designing and optimizing such processes, suspension quality Of Slurry is an important parameter. Suspension quality depends upon complex interactions of impeller generated flow, turbulence, and solid loading. Most of the earlier work on solid suspension focuses Oil identifying critical impeller speed for just suspension of solids (N(js)). In this study, apart from N(js) aspects like cloud height and liquid phase mixing in solid-liquid suspensions were also studied A new way of characterizing solid-liquid suspensions and liquid phase mixing using nonintrusive wall pressure fluctuation measurements has been developed. Systematic experimental data on N(js), cloud height, power consumption, mixing time, and circulation time over a range of solid volume fraction and impeller speeds have been presented here. The results and discussion presented here will have useful implications for designing solid-liquid stirred tanks.</p>1 aSardeshpande, Madhavi, V.1 aSagi, Aparna, R.1 aJuvekar, Vinay, A.1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/solid-suspension-and-liquid-phase-mixing-solid-liquid-stirred-tanks-002207nas a2200205   4500008004100000022001400041245011300055210006900168260006800237300001400305490000700319520140200326653000801728653003101736653002801767100003001795700002301825700002201848856013101870       2010                        eng d  a0001-154100aHysteresis in cloud heights during solid suspension in stirred tank reactor: experiments and CFD simulations0 aHysteresis in cloud heights during solid suspension in stirred t  a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcNOV  a2795-28040 v563 a<p>Solid suspension in stirred tank reactor is widely used in process industries for catalytic reactions, dissolution of solids, crystallization, and so on. Suspension quality is a key issue in design and operation of stirred reactor and its determination is not straight forward. Cloud height measurements of solid suspension provide a relatively simple way to quantify quality of suspension. In this work, experiments were carried out to quantify variation of cloud heights with impeller speed and particle characteristics. These measurements were carried out using visual observations, image analysis, and ultrasound velocity profiler techniques. The obtained data demonstrated the existence of hysteresis in cloud heights with respect to impeller speed. Apart from possible applications in reducing power required for achieving desired solid suspension quality, the existence of hysteresis also provides a new way to evaluate computational fluid dynamics (CFD) simulations of solid liquid flows in stirred vessels. An attempt was made to capture observed hysteresis in cloud heights in CFD simulations. The simulated results were compared with the experimental data. The presented models and results (experimental and computational) will he useful for simulating complex solid liquid flows in stirred reactors. (C) 2010 American Institute of Chemical Engineers AIChE J, 56: 2795-2804, 2010</p>10aCFD10ahysteresis in cloud height10asolid velocity profiles1 aSardeshpande, Madhavi, V.1 aJuvekar, Vinay, A.1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/hysteresis-cloud-heights-during-solid-suspension-stirred-tank-reactor-experiments-and-cfd-001552nas a2200229   4500008004100000022001400041245007600055210006900131260007600200300001400276490000700290520075500297653000801052653002101060653002101081653002801102653000801130100003001138700002301168700002201191856010901213       2011                        eng d  a0008-403400aSolid suspension in stirred tanks: UVP measurements and CFD simulations0 aSolid suspension in stirred tanks UVP measurements and CFD simul  aCOMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USAbWILEY-BLACKWELLcOCT  a1112-11210 v893 a<p>Suspension of solids in stirred reactor is widely used for catalytic reactions, dissolution, etc. Quality of solid suspension is an important parameter required for the reliable design, optimum performance, and scale up of the system. Quality of suspension depends on local characteristics of solid velocity and hold up profiles. The present work was focused on investigating quality of solid suspension using ultrasound velocity profiler (UVP) measurements and CFD simulations. The slip velocity measurements carried out with UVP were used to evaluate different drag correlations used in CFD simulations. Results discussed in this work would be useful for extending the applications of CFD models for simulating large stirred slurry reactors.</p>10aCFD10adrag coefficient10asolid suspension10asolid-liquid velocities10aUVP1 aSardeshpande, Madhavi, V.1 aJuvekar, Vinay, A.1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/solid-suspension-stirred-tanks-uvp-measurements-and-cfd-simulations-002272nas a2200205   4500008004100000022001400041245008000055210006900135260010200204300001400306490000800320520148800328653003301816653001501849653002101864653001801885100003001903700002201933856011101955       2012                        eng d  a0011-389100aComputational fluid dynamics modelling of solid suspension in stirred tanks0 aComputational fluid dynamics modelling of solid suspension in st  aC V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIAbINDIAN ACAD SCIENCEScJUN  a1539-15510 v1023 a<p>Solid suspension and mixing are crucial in many important processes, including multiphase catalytic reactions, crystallization, precipitation, etc. In recent years, various efforts have been made to numerically simulate solid-liquid flows in stirred vessels using computational fluid dynamics (CFD). In this article, we present a brief account of our group's efforts at developing and using CFD models for simulating solid suspension in stirred tanks. Computational models were developed and evaluated by comparing model predictions with our data as well as published experimental data. A variety of experimental techniques ranging from torque and wall pressure fluctuations to ultrasound velocity profiler were used. Efforts were made to develop appropriate sub-models for capturing influence of the prevailing turbulence and solid volume fraction on effective inter-phase coupling terms. A hysteresis in variation of the height of the cloud of suspended solid with impeller rotational speed was observed. The hysteresis, besides having applications in realizing better suspension at lower effective power consumption, also offers an attractive evaluation test for CFD models. A new way to carry out dynamic settling of solid cloud by sudden impeller stoppage has been developed. The approach, models and results presented here will be useful for extending applications of CFD models for simulating industrial stirred slurry reactors as well as further research in the field.</p>10acomputational fluid dynamics10ahysteresis10asolid suspension10astirred tanks1 aSardeshpande, Madhavi, V.1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/computational-fluid-dynamics-modelling-solid-suspension-stirred-tanks-002296nas a2200157   4500008004100000022001400041245007800055210006900133260007100202300001400273490000700287520168600294100003001980700002202010856010602032       2012                        eng d  a0888-588500aSimulation of settling of solid particles due to sudden impeller stoppage0 aSimulation of settling of solid particles due to sudden impeller  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAR  a4112-41180 v513 a<p>Stirred tank reactors (STRs), which are used in process industries (for a variety of operations, such as catalytic reactions, dissolution of a solid, crystallization, and so on), often involve handling of solid liquid (gas) systems. The solid suspension and the quality of the suspension are key issues in the design and operation of such stirred reactors. Despite extensive experimental work over previous decades, comprehensive understanding and reliable methods to predict the solids suspension and the quality of the suspension are not yet available. Advances in computational fluid dynamics (CFD) and new experimental techniques offer potentially effective ways of understanding solids suspension in stirred tanks. The present work highlights the potential of using transient measurements by way of the dynamic settling of solid particles because of the sudden stoppage of an impeller to evaluate CFD models. Sudden impeller stoppage results in significantly different conditions, in terms of the ratio of particle diameter to Kolomogorov length scale (d(p)/lambda), as well as the solids volume fraction experienced by solid particles. Therefore, experimental data under such sudden impeller stoppage offer a better way to evaluate the influence of prevailing turbulence and solids volume fraction on effective drag and therefore offer a more-stringent test to CFD models than steady-state profiles. Besides facilitating the development of computational models, the experimental and simulation studies of sudden impeller stoppage also provide useful data to gain insight into the behavior of the stirred tank after abrupt impeller stoppage due to sudden power failure.</p>1 aSardeshpande, Madhavi, V.1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/simulation-settling-solid-particles-due-sudden-impeller-stoppage-001922nas a2200229   4500008004100000022001400041245006100055210005900116260010200175300001400277490000700291520115300298653001201451653001201463653001801475653001801493653001801511653001901529100003001548700002201578856009201600       2013                        eng d  a0256-249900aTwo-phase flow boiling in small channels: a brief review0 aTwophase flow boiling in small channels a brief review  aC V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIAbINDIAN ACAD SCIENCEScDEC  a1083-11260 v383 a<p>Boiling flows are encountered in a wide range of industrial applications such as boilers, core and steam generators in nuclear reactors, petroleum transportation, electronic cooling and various types of chemical reactors. Many of these applications involve boiling flows in conventional channels (channel size &gt;= 3 mm). The key design issues in two phase flow boiling are variation in flow regimes, occurrence of dry out condition, flow instabilities, and understanding of heat transfer coefficient and vapor quality. This paper briefly reviews published experimental and modeling work in these areas. An attempt is made to provide a perspective and to present available information on boiling in small channels in terms of channel size, flow regimes, heat transfer correlations, pressure drop, critical heat flux and film thickness. An attempt is also made to identify strengths and weaknesses of published approaches and computational models of boiling in small channels. The presented discussion and results will provide an update on the state-of-the-art and will be useful to identify and plan further research in this important area.</p>10aBoiling10adry-out10aheat transfer10ainstabilities10asmall channel10atwo-phase flow1 aSardeshpande, Madhavi, V.1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/two-phase-flow-boiling-small-channels-brief-review-001501nas a2200193   4500008004100000245005900041210005900100260019200159520069300351653001701044653002101061653001801082653002601100100003001126700002301156700002201179700001301201856009301214       2015                        eng d00aTwo phase flow boiling pressure drop in small channels0 aTwo phase flow boiling pressure drop in small channels  aSARA BURGERHARTSTRAAT 25, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbIUTAM, Dept Sci Technol India; Ministry Earth Sciences; CSIR; Natl Sci Fdn, USA; Intel Ansys Fujitsu & TSI IndiacDEC3 a<p>Two-phase pressure drop, flow instability and boiling regime identifications are an essential step in the design of a variety of plant in the power and process industries. Despite the wide spread applications, significant experimental data on flow boiling in small channel is not available. In the present work, experimental set-up was designed for studying boiling flows in 19 mm ID tube and identifies flow regimes at various mass and heat flux conditions by varying inlet fluid temperature. The steady-state pressure data was collected and flow regimes identified using pressure drop and pressure fluctuations inside the channel. (C) 2015 The Authors. Published by Elsevier B.V.</p>10aflow boiling10aflow instability10apressure drop10aregime identification1 aSardeshpande, Madhavi, V.1 aShastri, Parikshit1 aRanade, Vivek, V.1 aSahu, KC  uhttps://library.ncl.res.in/content/two-phase-flow-boiling-pressure-drop-small-channels-002033nas a2200217   4500008004100000022001400041245009700055210006900152260009500221300000900316490000700325520122400332653000801556653001701564653001901581653001801600100003001618700002301648700002201671856012201693       2015                        eng d  a0263-876200aVoid fraction measurement using electrical capacitance tomography and high speed photography0 aVoid fraction measurement using electrical capacitance tomograph  a165-189 RAILWAY TERRACE, DAVIS BLDG, RUGBY CV21 3HQ, ENGLANDbINST CHEMICAL ENGINEERScFEB  a1-110 v943 a<p>Gas-liquid flows are encountered in variety of industrial applications including boilers, distillation towers, chemical reactors, oil pipelines, nuclear reactors etc. The measurement of two-phase flow parameters such as flow regime and void fraction is considerably important and play an important role in characterization of the hydrodynamic behavior of such gas-liquid two phase systems. The void fraction is a dimensionless quantity and is often termed as ``holdup or fraction'' in two-phase flows. According to industrial applications; it is essential to develop measurement technique for void fraction measurement which can work in hot and opaque systems. Therefore, an attempt was made here to establish electrical capacitance tomography (ECT) facility for measuring void fraction and flow regimes as well as develop suitable data processing methodologies. In the present work, focus was to measure void fraction using ECT technique and compares it with conventional and high speed photography technique. Therefore, that will give guidelines of using ECT technique for hot and opaque systems like boiling flows. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier BM. All rights reserved.</p>10aECT10aFlow regimes10aTwo phase flow10aVoid fraction1 aSardeshpande, Madhavi, V.1 aHarinarayan, Sagar1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/void-fraction-measurement-using-electrical-capacitance-tomography-and-high-speed-102178nas a2200229   4500008004100000022001400041245009200055210006900147260009900216300001200315490000700327520132100334653000801655653001601663653003101679653002701710100003001737700001801767700001501785700002201800856012601822       2016                        eng d  a0955-598600aMixing studies in unbaffled stirred tank reactor using electrical resistance tomography0 aMixing studies in unbaffled stirred tank reactor using electrica  aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcMAR  a110-1210 v473 a<p>Unbaffled stirred tanks are extensively used in chemical process industries for variety of applications including semi-batch reactions. In un-baffled stirred tanks, impeller rotation generates a vortex and reactants are added into this vortex. There is a growing interest towards understanding the mixing performance of such unbaffled stirred vessels. The present work is aimed at providing experimental results on mixing time and solid particle distribution inside an unbaffled vessel using electrical resistance tomography (ERT). A methodology for using ERT for characterizing vortex and mixing in unbaffled stirred vessel was established. The ERT was used to measure the mixing time with and without solid particles (glass beads, 250 mu m) in a stirred reactor. In this study, ERT technique was effectively applied for imaging solid-liquid flow and developed suitable data processing methodologies. It observed that estimated liquid phase mixing time for Un-baffled vessel was more as compared to baffled vessel. Radial solid concentration profiles showed Gaussian distribution inside the vessel. The presented methodology of using ERT and experimental results will be useful for designing and estimating mixing and solid distribution in unbaffled stirred tanks. (C) 2016 Elsevier Ltd. All rights reserved.</p>10aERT10aMixing time10aRadial solid concentration10aUnbaffled stirred tank1 aSardeshpande, Madhavi, V.1 aKumar, Gaurav1 aAditya, T.1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/mixing-studies-unbaffled-stirred-tank-reactor-using-electrical-resistance-tomography-002059nas a2200217   4500008004100000022001400041245007100055210006900126260006700195300001200262490000700274520131500281653000801596653001701604653002701621653001901648100003001667700002001697700002201717856010201739       2016                        eng d  a0008-403400aTwo-phase flow boiling in 19mm tube: experiments and CFD modelling0 aTwophase flow boiling in 19mm tube experiments and CFD modelling  a111 RIVER ST, HOBOKEN 07030-5774, NJ USAbWILEY-BLACKWELLcMAY  a872-8850 v943 a<p>Boiling flows are encountered in a wide range of industrial applications such as boilers, nuclear reactors, electronic cooling, and various types of chemical reactors. Heat transfer coefficients, flow boiling regimes, flow instabilities, pressure drops, and conditions like dry-out are some of the key issues in every boiling flow study. It is observed that a limited experimental database is available for the 19mm ID channel diameter, i.e. a typical tube diameter of steam generator. Therefore, in the present work, the experimental setup was designed for studying boiling flows in a 19mm ID tube in such a way that different flow regimes occurring in a steam generator tube (from pre-heating of sub-cooled water to dry-out) could be investigated by varying inlet conditions. The reported results cover a reasonable range: 8-27kW/m(2) and 2.9-5.9kg/m(2)s heat and mass flux conditions, respectively. A basic computational flow model was also developed to facilitate interpretation of the obtained data. The presented design of the experimental setup and the approach of mimicking different types of steam generator tubes as well as presented experimental and simulated results are useful for gaining insight into complex boiling flows in tubes, and provide a sound basis for further work in this area.</p>10aCFD10aFlow regimes10atwo-phase flow boiling10avapour quality1 aSardeshpande, Madhavi, V.1 aRaymond, Barlev1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/two-phase-flow-boiling-19mm-tube-experiments-and-cfd-modelling02133nas a2200157   4500008004100000245005900041210005800100260000800158300001200166490000700178520162400185100003001809700002301839700002201862856009101884       2016                        eng d00aTwo-phase flow boiling pressure drop in small channels0 aTwophase flow boiling pressure drop in small channels  cOCT  a636-6490 v613 aTwo-phase flow boiling in small channels finds a variety of applications in power and process industries. Heat transfer, boiling flow regimes, flow instabilities, pressure drop and dry out are some of the key issues related to two-phase flow boiling in channels. In this work, the focus is on pressure drop in two-phase flow boiling in tubes of 19 mm diameter. These tubes are typically used in steam generators. Relatively limited experimental database is available on 19 mm ID tube. Therefore, in the present work, the experimental set-up is designed for studying flow boiling in 19 mm ID tube in such a way that any of the different flow regimes occurring in a steam generator tube (from pre-heating of sub-cooled water to dry-out) can be investigated by varying inlet conditions. The reported results cover a reasonable range of heat and mass flux conditions such as 9-27 kW/m(2) and 2.9-5.9 kg/m(2) s respectively. In this paper, various existing correlations are assessed against experimental data for the pressure drop in a single, vertical channel during flow boiling of water at near-atmospheric pressure. A special feature of these experiments is that time-dependent pressures are measured at four locations along the channel. The steady-state pressure drop is estimated and the identification of boiling flow regimes is done with transient characteristics using time series analysis. Experimental data and corresponding results are compared with the reported correlations. The results will be useful for understanding key aspects of flow boiling in small channels. (C) 2016 Elsevier Inc. All rights reserved.1 aSardeshpande, Madhavi, V.1 aShastri, Parikshit1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/two-phase-flow-boiling-pressure-drop-small-channels02689nas a2200121   4500008004100000245009600041210006900137260008800206520209200294100003002386700002902416856012202445       2017                        eng d00aDirect steam generation for process heat applications in compound parabolic collector (CPC)0 aDirect steam generation for process heat applications in compoun  aPalma, SpainbINTL Solar Energy Soc, Wiesentalstr 50, Freiburg, 79115, GermanycJUL3 aIn recent years, CPC (Compound Parabolic Collector) is gaining its acceptance for temperature range higher than non-concentrating stationery solar collectors like flat plate collectors but lower end of temperature range of concentrating solar collectors like PTC (parabolic trough concentrators). Generally, pressurized hot water or thermal oil is used as a working fluid in the CPC. The elimination of solar tracking in CPC provides flexibility for installation and lower price point compared to other concentrating technologies with tracking. 

Steam is one of the universally accepted working fluid for process heat applications due to availability, nontoxic and high heat carrying capacity. Many industrial sectors such as food and beverages, textile, chemical processes etc utilize steam as a working fluid for process heat applications. Direct steam generation as a working fluid through a CPC has various operational, integration and cost advantages. The use of CPC for direct steam generation at saturation steam temperature range 105-145 degrees C (equivalent saturation pressure 0.5-3 bar (g)) can cater for low temperature process heat demand. Solar radiation intensity changes with the time of the day leading to change in heat flux for steam generation. There arc challenges for handling two phase flow (steam generation) in 'U' shaped metal tubes due to pressure drop, flow instabilities and control of steam dryness fraction under vatying solar heat flux. 

The focus of the present research work is to analyze a CPC system for direct steam generation. This paper discusses an experimental setup and challenges for direct steam generation. The experimental measurements will he focused on behavior of the thermal flow pattern inside the inclined metal tube at various heat flux conditions throughout the day, measurement of local heat transfer coefficients and corresponding vapor quality. Experimental data analysis and understanding will be useful to develop direct steam generation engineering schemes and its integration approach with various end-use applications.1 aSardeshpande, Madhavi, V.1 aSardeshpande, Vishal, R.  uhttps://library.ncl.res.in/content/direct-steam-generation-process-heat-applications-compound-parabolic-collector-cpc02105nas a2200157   4500008004100000245008900041210006900130260000800199300001200207490000800219520153600227100003001763700001701793700002201810856011501832       2017                        eng d00aElectrical resistance tomography for gas holdup in a gas-liquid stirred tank reactor0 aElectrical resistance tomography for gas holdup in a gasliquid s  cOCT  a476-4900 v1703 aGas-Liquid flows in stirred tank reactors (STR) are used in many significant industrial operations such as hydrogenation, absorption, stripping, oxidation, hydrogenation, ozonation, chlorination, fermentation, etc. Gas-Liquid STRs are expected to perform several functions such as mixing, dispersing gas into liquid, mass and heat transfer and reactions. Gas hold up distribution and various flow regimes are the key parameters affecting performance of gas-liquid STRs. Various techniques such as visual analysis, photography, light attenuation, optical probe method are used to understand gas hold-up distribution within stirred tanks. Most of these techniques have some limitations with respect to measurement of gas hold up distribution. Electrical Resistance Tomography (ERT) is an upcoming technique for obtaining both qualitative and quantitative data on multiphase process units non-invasively and non-intrusively. In this work, an attempt was made to establish and validate the ERT technique for characterizing gas-liquid flows in a laboratory scale STR using the Rushton turbine impeller. ERT was used to study gas holdup and to identify flow regimes. The results were compared with the visual measurements as well as previously published correlations. The effect of gas flow rate, impeller speed on the mean gas holdup is discussed. The methodology and results presented in this work will be useful to effectively apply ERT for characterizing gas-liquid flows in stirred tanks. (C) 2017 Elsevier Ltd. All rights reserved.1 aSardeshpande, Madhavi, V.1 aGupta, Suraj1 aRanade, Vivek, V.  uhttps://library.ncl.res.in/content/electrical-resistance-tomography-gas-holdup-gas-liquid-stirred-tank-reactor