An experimental investigation on heat transfer enhancement in circular jet impingement on hot surfaces by using Al2O3/water nano-fluids and aqueous high-alcohol surfactant solution

The present article reports the heat transfer characteristics of a vertical stainless steel foil of 0.15 mm thickness (SS304) by circular impinging jets of various fluids such as pure water, nano-fluids (Al₂O₃-water, ф = 0.15%, 0.6%), and aqueous high-alcohol surfactant (HAS, i.e., 2-ethyl-hexanol, 100–400 ppm) studied using an infrared thermal imaging camera (A655sc, FLIR System). The enhancement in the heat transfer rates for Al₂O₃-water nano-fluids with ф = 0.15%, ф = 0.60%, and aqueous surfactant solution (150ppm) is found to be 140%, 207%, and 117% higher compared to pure water results, respectively. The surface characteristics of the foil after jet impingement by various fluids are also studied using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and surface wettability.     

Synthesis and characterization of polylactic acid (PLA) using a solid acid catalyst system in the polycondensation method

In this study, synthesis of poly(l(+) lactic acid) was carried out by using an acid catalyst. Neat chlorosulfonic acid reacts with cellulose to give cellulose sulfuric acid in which sulfuric acid is immobilized on the cellulose surface via bond formation. Cellulose sulfuric acid was used as a catalyst in a quantity of 1.0 wt.% calculated on the monomer. Polycondensation was carried out over a period of 24 h. The resulting poly(l(+) lactic acid) was characterized by Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) thermogravimetric analysis (TGA), ¹H and ¹³C nuclear magnetic resonance (NMR), and gel permeation chromatography. The molecular weight of poly(l-lactic acid) reached as high as 14,875.     

Cooperative Effect of Noncovalent Interactions on Tetrel Bonding in Halogenated Silanes

Tetrel bond, a weak noncovalent interaction between the σ-hole of a Group IV element (silicon in our case) and the cloud of an electronegative element (oxygen in our case) is the focus of this work. The percentage strengthening of tetrel bond has been investigated by optimizing 16 binary complexes of halogenated silane and water of general formula SiX_nH_4−n−H₂O and 16 ternary complexes, of general formula NaX−SiX_nH_4−n−H₂O, where X=F, Cl, Br and I and n=1, 2, 3 and 4 at various levels of theory defined within the formalism of density functional theory (DFT). With the addition of NaX, tetrel bond between Si and O in SiX_nH_4−n−H₂O gets strengthened up to 49 %, owing to cooperativity effect exerted by hydrogen bonding between X and H in the ternary complex NaX−SiX_nH_4−n−H₂O. In the series of complexes studied here, overall stabilization due to cooperativity lies between 10 kJ/mol to 170 kJ/mol. This large extent of reinforcement due to cooperativity has never been showcased before. The exceptional stabilization and reinforcement owe its genesis to the transformation of the ternary complex into a cluster orchestrated by the H-bonding in most of the cases and covalent bonding in few of the cases.     

Influence of K<Subscript>2</Subscript>Ti<Subscript>6</Subscript>O<Subscript>13</Subscript> on dielectric and barrier properties of polymer

Polymer composite comprising polyvinylidene fluoride (PVDF) and potassium hexatitante (K₂Ti₆O₁₃) was synthesized by solution casting. The effect of K₂Ti₆O₁₃ on surface, thermal, and electrical properties of polymer composite were investigated. The addition of K₂Ti₆O₁₃ with polymer leads to thermal degradation and transition of polymer composite from semi-crystalline to amorphous phase. The optimum results of contact angle for different loading wt% of K₂Ti₆O₁₃ were directly correlated with the surface morphology. Our experimental results confirmed the incorporation of K₂Ti₆O₁₃ in polymer by SEM micrographs. The evaluated dielectric properties (ε' = 424; tan δ = 2.14 at 130 °C and 100 Hz frequency for 20 wt% loading of K₂Ti₆O₁₃) for polymer composite are higher in compared to pure polymer. The enhancement in dielectric constant and changing the surface properties of polymer composite can be used for the development of electrochemical storage device applications.     

TLC Based Method for Standardization of Pongamia pinnata (Karanj) Using Karanjin as Marker

Pongamia pinnata Linn. (Papilionaceae) seeds have gained great commercial and industrial importance owing to their high oil content. Presently, there is no appropriate TLC based method available for standardization of P. pinnata. A simple, robust and reproducible TLC method for the determination of Karanjin is reported in the seeds of P. pinnata. The method involves separation of components by TLC on pre-coated silica gel G 60 F₂₅₄ plates developed on toluene: ethyl acetate (7:3 v/v) and detection at 260 nm in absorbance mode. The sensitivity of the method was found to be 100 ng. The linearity range was 50–300 ng. Four samples of P. pinnata from different geographical locations were tested for their karanjin content using the developed method. The proposed method was found to be robust, precise, and accurate, it therefore holds potential for detection, monitoring and quantification of karanjin in Pongamia pinnata.

     

Fuel spray visualization and its impingement analysis on in-cylinder surfaces in a direct-injection spark-ignition engine

Abstract  

Experiments are performed to investigate the effects of fuel spray on in-cylinder mixture preparation and its impingement on cylinder walls and piston top inside a direct-injection spark-ignition engine with optical access to the cylinder. Novel image processing algorithms are developed to analyze the fuel impingement quantitatively on in-cylinder surfaces. The technique is useful to optimize the fuel pressure, injection timing and the number of injections to minimize the fuel impingement on in-cylinder surfaces. E85, which represents a blend of 85% ethanol and 15% gasoline (by volume) is used in this study. Two types of fuel injectors are used; (i) low-pressure production-intent injector with fuel pressure of 3 MPa, and (ii) high-pressure production injector with fuel pressures of 5 and 10 MPa. In addition, the effects of split injection are also presented by maintaining the same amount of fuel used in single injection. It is found that the split injection is an effective way to reduce the overall fuel impingement on in-cylinder surfaces while maintaining a reasonably good air–fuel mixture in the cylinder.     

Synthesis,characterization and application of zinc oxide nano particles for removal of hexavalent chromium

The present study was conducted to evaluate the adsorption efficiency of synthesized nano zinc oxide (n-ZnO) for the removal of hexavalent chromium (Cr⁶⁺). The synthesized sample was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Batch experiment results revealed that low dose (4 g L^?1) of n-ZnO was highly efficient at the initial metal concentration of 9 mg L^?1 in acidic conditions (pH 2) at 50 °C for the contact time of 90 min. A Langmuir adsorption isotherm model was found to be best fitted indicating a homogeneous surface and the adsorption followed pseudo-second order kinetics. Intra-particle diffusion was not a rate limiting factor in the present study. Thermodynamic study revealed that the adsorption process was endothermic and spontaneous at all the studied temperatures with increasing randomness.