02464nas a2200241   4500008004100000022001400041245006600055210006500121260006800186300001400254490000700268520169600275653000801971653001401979653001801993653002102011653001702032100002302049700001902072700001502091700002002106856009602126       2008                        eng d  a0001-154100aFlow pattern in vortex diode: experiments and CFD simulations0 aFlow pattern in vortex diode experiments and CFD simulations  a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcMAY  a1139-11520 v543 a<p>Vortex diodes are used as leaky nonreturn valves in applications, where it is desirable to avoid valves with moving parts. Despite their use in practice for several decades, no detailed analysis of the flow inside the vortex diodes is available. A strategy was derived for the CFD simulations of the vortical flow in diodes. A good agreement was seen between pressure drop (Delta P) across the inlet-outlet ports from CFD simulations, and the experimental data for five diode sizes. The simulations showed that in the reverse flow situation tangential velocity was dominant and resulted in conservation of angular momentum in the chamber until it reaches the axial exit port. This vortical motion induced a significant pressure drop (Delta P-r). The axial velocity gradient over the chamber cross-section helps in inducing relaminarization of the flow. In the forward flow mode, the fluid gets distributed radially over the chamber and exits through the tangential port, yielding low Delta P-f. The analysis showed that the performance of a diode is strongly affected by diode geometry, size, aspect ratio, nozzle configuration and Reynolds number. Among different configurations, the nozzles with entry port size equal to diode yielded higher diodicity. Simulations showed that using angle of divergence for diffuser sections of nozzles of the order of 7 degrees exhibited higher diodicity than smaller angles. It was also observed that at higher flow rates significantly higher diodicity was obtained using axial nozzles with larger radius of curvature for expander section. The modeling methodology and results presented will be useful for evolving better designs of vortex diodes.</p>10aCFD10aDiodicity10apressure drop10arelaminarization10aVortex diode1 aKulkarni, Amol, A.1 aRanade, V., V.1 aRajeev, R.1 aKoganti, S., B.  uhttp://library.ncl.res.in/content/flow-pattern-vortex-diode-experiments-and-cfd-simulations01729nas a2200193   4500008004100000022001400041245004700055210004700102260007100149300001400220490000700234520111100241100002301352700001401375700002001389700002101409700002601430856007901456       2011                        eng d  a0888-588500aFractal impeller for stirred tank reactors0 aFractal impeller for stirred tank reactors  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUN  a7667-76760 v503 a<p>Stirred tank reactors are used for variety of applications at different scales of operation. The conventional impellers tend to develop regions having nonuniform energy dissipation rates in the stirred reactor. In this work, we propose a novel fractal impeller, which helps in reducing such nonuniformities and help develop a uniform randomness throughout the reactor. The impeller geometry is discussed in detail. Experimental measurements of the power consumption, mixing time, suspension quality, and the ability for gas dispersion were carried out, and the performance is compared with the conventional impellers. The impeller is seen to have a low power number, and it can generate a uniform suspension of particles even at relatively lower impeller speeds and can efficiently disperse gas into liquid to yield relatively higher gas hold-up values. The Fourier analysis of the power consumption time series data indicates that no specific prominent frequency events exist in the reactor, and the spectrum showed several frequency events to exist in the reactor with almost identical prominence.</p>1 aKulkarni, Amol, A.1 aJha, Neha1 aSingh, Abhishek1 aBhatnagar, Sumit1 aKulkarni, Bhaskar, D.  uhttp://library.ncl.res.in/content/fractal-impeller-stirred-tank-reactors-0