Computational fluid-dynamics-based analysis of a ball valve performance in the presence of cavitation

In this paper, the ball valve performance is numerically simulated using an unstructured CFD (Computational Fluid Dynamics) code based on the finite volume method. Navier-Stokes equations in addition to a transport equation for the vapor volume fraction were coupled in the RANS solver. Separation is modeled very well with a modification of turbulent viscosity. The results of CFD calculations of flow through a ball valve, based on the concept of experimental data, are described and analyzed. Comparison of the flow pattern at several opening angles is investigated. Pressure drop behind the ball valve and formation of the vortex flow downstream the valve section are also discussed. As the opening of the valve decreases, the vortices grow and cause higher pressure drop. In other words, more energy is lost due to these growing vortices. In general, the valve opening plays very important roles in the performance of a ball valve.     

1,3-Migration of Trimethylsilyl Group from Carbon to Oxygen in Highly Sterically Hindered Silanol of the Type (Me 3 Si) 3 CSi(C 6 H 4 Me- p )MeOH and Reaction of the Related Iodide with Iodine Monochloride and Iodine Monobromide

The silanol (Me 3 Si) 3 CSi(C 6 H 4 Me- p )MeOH has been shown to isomerize to (Me 3 Si) 2 CHSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ) when it was kept at room temperature for 10 h in 0.2 M NaOMe/MeOH. Corresponding isomerizations of the above silanol (to give (Me 3 Si) 2 CHSi(C 6 H 4 Me- p ) (Me)(OSiMe 3 )) are complete after 26 h under reflux in pyridine. The reaction involve 1,3-migration from carbon to oxygen within a silanolate ion to give a carbanion, which rapidly acquires a proton from the solvent. Treatment of (Me 3 Si) 3 CSi(C 6 H 4 Me- p )MeOH with MeLi in Et 2 O/THF give, by the same rearrangement, the organolithium reagent (Me 3 Si) 2 CLiSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ) which on treatment with Me 2 SiHCl gives (Me 3 Si) 2 C(SiMe 2 H)Si(C 6 H 4 Me- p )(Me)(OSiMe 3 ) and (Me 3 Si) 2 CHSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ). When the experiment was repeated, but with Me 3 SiCl in place of Me 2 SiHCl, it gives exclusively (Me 3 Si) 2 CHSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ). Treatment of the organolithium reagent (Me 3 Si) 2 CLiSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ) with Mel gives exclusively (Me 3 Si) 2 CMeSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ). The related iodide (Me 3 Si) 3 CSi(C 6 H 4 Me- p )Mel reacts with ICI and IBr to give rearranged (Me 3 Si) 2 C(SiMe 2 X)Si(C 6 H 4 Me- p )Me 2 and unrearranged products (Me 3 Si) 3 CSi(C 6 H 4 Me- p )MeX, (X = Cl, Br) respectively. The rearranged bromide (Me 3 Si) 2 C(SiMe 2 Br)Si(C 6 H 4 Me- p )Me 2 reacts with a range of silver [I] salts AgY (Y = OOCCH 3 , SO 4 2 m ) and Mercury [II] salt HgY 2 (Y = OOCCH 3 , SO 4 2 m ) in glacial CH 3 COOH to give the corresponding species (Me 3 Si) 2 C(SiMe 2 OOCCH 3 )Si(C 6 H 4 Me- p )Me 2 . The reaction of the bromide with AgBF 4 in MeOH or i -PrOH give the corresponding rearranged products (Me 3 Si) 2 C(SiMe 2 Y)Si(C 6 H 4 Me- p )Me 2 (Y = --OMe, --OPr i ).     

SELECTIVE OXIDATION OF BENZYLIC ALCOHOLS USING CAN SUPPORTED ONTO SILICA GEL UNDER MICROWAVE IRRADIATION

Cerium ammonium nitrate (CAN) adsorbed on HNO ₃ /silica gel is a mild reagent for selective oxidation of benzylic alcohols to the corresponding aldehydes under microwave irradiation in solventless system.     

Palladium-Catalyzed Synthesis of Symmetrical Biaryls Under Microwave Irradiation and Conventional Heating

The activity of the [Pd{C₆H₄(CH₂N(CH₂Ph)₂)}(µ-Br)]₂ complex was investigated in the synthesis of symmetrical biaryls under both conventional and microwave irradiation conditions, and their results were compared. This complex is efficient, stable, and not sensitive to air or moisture and is a catalyst for the homo-coupling reaction of aryl iodides, bromides, and even chlorides. The products were produced in excellent yields in short reaction times using a catalytic amount of [Pd{C₆H₄(CH₂N(CH₂Ph)₂)(µ-Br)]₂ complex in N-methylpyrolidine (NMP) at 130 °C. In comparison to conventional heating conditions, the reactions under microwave irradiation gave better yields in shorter reaction times.     

Synthesis of Isobenzofuran-1(3H)-ones with the Aid of Silica-Supported Preyssler Nanoparticles

Silica-supported Preyssler nanoparticles appear to be a new and efficient solid acid catalyst for an economical, and environmentally benign one-pot synthesis of 3-substituted phthalides.     

NH2SO3H and H6P2W18O62 · 18H2O-Catalyzed,Three-Component,One-Pot Synthesis of Benzo[c]acridine Derivatives

We report here two simple methods for the synthesis of benzo[c]acridine derivatives from three-component, one-pot condensation of 1-naphthylamine, dimedone, and a variety of substituted aldehydes in the presence of a catalytic amount of NH₂SO₃H or H₆P₂W₁₈O₆₂ · 18H₂O under solvent-free conditions at 120 °C or in refluxing ethanol.     

Efficient,Rapid, and Regioselective Bromination of Phenols and Anilines with N-Bromosaccharin Using Tungstophosphoric Acid as a Heterogeneous Recyclable Catalyst

A simple, efficient, and rapid method for high-yielding regioselective mono bromination of phenols and anilines has been achieved by treatment with N-bromasaccharin in the presence of a catalytic amount of tungstophosphoric acid.     

Synthesis of Novel Chiral Ionic Liquid and Its Application in Reduction of Prochiral Ketones to the Corresponding Chiral Alcohols Using NaBH4

A novel chiral ionic liquid (CIL) based on nicotinium salt has been synthesized and used as an efficient asymmetric chiral catalyst for reduction of acetophenone derivatives with NaBH₄ in methanol at room temperature. The optically active alcohols were obtained in low to moderate enantiomeric excess in a short reaction time.     

Efficient Synthesis of Bis-Coumarins Using Silica-Supported Preyssler Nanoparticles

Reaction of aldehydes and 4-hydroxycoumarin in the presence of catalytic amount of silica-supported Preyssler nanoparticles led to synthesis of bis-coumarins in excellent yields.     

Brønsted Acidic Ionic Liquids: New,Efficient, and Green Promoter System for the Synthesis of 4(3H)-Quinazolinones

A simple, inexpensive, and efficient new synthesis of 4(3H)-quinazolinones from the reaction of 2-aminobenzamide with aroyl chlorides in the presence of two new halogen-free Brønsted acidic ionic liquids, 3-methyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate [(CH₂)₄SO₃HMIM][HSO₄] and 1-(4-sulfonic acid) butylpyridinium hydrogen sulfate [(CH₂)₄SO₃HPY][HSO₄], green and reusable catalysts, with excellent product yields under solvent-free conditions is reported. The products could be separated simply from the catalyst, and the catalyst could be recycled without noticeably decreasing the catalytic activity.