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Structural isomers of naphthalene-bridged disilanes were prepared via catalytic intramolecular dehydrocoupling of disilyl precursors using Wilkinson's catalyst. Interestingly, it was observed that interchanging the side groups on the silicon atoms altered the photophysical properties of the bridged disilanes. Herein, we report the first example of naphthalene bridged disilanes forming excimers in non-polar solvents. Cyclic voltammetry experiments and DFT calculations were performed to analyse the band gaps of the compounds and σ–π mixing in the bridged disilanes.

The thermal efficiency of the solar air heater (S.A.H.) is enhanced by introducing various artificial roughness geometries on the absorber surface. Artificial roughnesses in the form of a chamfered...

Heat transfer and fluid flow characteristics in roughened solar air heater duct with combined square and equilateral triangular ribs as roughness is investigated using experimental and computationa...

In this research work a setup is designed to incorporate Lauric acid as a phase changing material (PCM) in a solar air heater. This phase changing material (PCM) is carefully selected based on the application and manufacturing constraints. A thermal energy storage device (TESD) is manufactured and incorporated in solar air heater and experiments were carried out to compare the solar air heater with and without thermal energy storage device (TESD) to evaluate various parameters such as output temperature and pressure drop. Results revealed that the rise in the output air temperature decreases from 8.67 K to 4 K with the increase in the mass flow rate of air flowing through the solar air heater from 0.021 kg/s to 0.035 kg/s. Also with an increase in the mass flow rate, there is a decrease in the friction factor from 0.0119 to 0.00802. There is an average increment of 86.47% in the rise of output air temperature with TESD as compared to rise of the output air temperature without TESD with an average increment of 36.47% in friction factor. A computational analysis is also performed which gives insight into the working of solar air heater with thermal energy storage device (TESD). A computational domain of solar air heater with TESD is analyzed in CFD code FLUENT using various turbulence models such as k-ω SST, k-ω Standard, k-∊ Standard and k-∊ RNG. It is observed that results obtained from turbulence model k-є RNG model are in good agreement with the experimental results and hence used for the analysis of all the cases considered in this work. Keywords: Phase changing materials, Heat transfer, Energy storage device, Solar air heater, Friction factor

The mol­ecular and crystal structures of 2-iodo benzamide and 2-iodo-N-phenyl­benzamide are reported. In both crystals, N—H⋯O hydrogen bonds and C—I⋯π(ring) inter­actions stabilize the packing with additional C—H⋯π(ring) contacts found in the latter., The title compounds, 2-iodo­benzamide, C7H6INO (I), and 2-iodo-N-phenyl­benzamide, C13H10INO (II), were both synthesized from 2-iodo­benzoic acid. In the crystal structure of (I), N—H⋯O and hydrogen bonds form two sets of closed rings, generating dimers and tetra­mers. These combine with C—I⋯π(ring) halogen bonds to form sheets of mol­ecules in the bc plane. For (II), N—H⋯O hydrogen bonds form chains along the a-axis direction, while inversion-related C—I⋯π(ring) contacts supported by C—H⋯π(ring) interactions generate sheets of mol­ecules along the ab diagonal.

A solar air heater is a thermal system which uses artificial roughness in the form of repeated ribs on the absorber plate to enhance the heat transfer rate. Forced convection heat transfer of air in a solar air heater with reverse L-shaped ribs has been carried out experimentally and numerically. Thermal performance of solar air heater is studied with design variables such as relative roughness pitch (7.14 ⩽ P / e ⩽ 17.86), Reynolds number (3800 ⩽ Re ⩽ 18,000), heat flux (1000 W/m 2 ) and constant relative roughness height ( e / D = 0.042). A two dimensional CFD simulation is carried out with using CFD code, ANSYS FLUENT and RNG k – ɛ turbulence model, for solving turbulence terms in governing equations. The presence of reverse L-shaped rib shows a significant effect on heat transfer and friction factor characteristics, relative to change in relative roughness pitch ( P / e ) and Reynolds number ( Re ). Thermo hydraulic performance parameter (T.H.P.P) of 1.90 considering heat transfer augmentation with same pumping power, has been evaluated for optimum configuration of the roughness element (reverse L-shaped rib) for artificially roughened solar air heater. It has been found that the numerical results are in good agreement with the experimental results for the range of parameters investigated. Correlations for Nusselt number and friction factor have been developed as a function of roughness and flow parameters.

A solar air heater is experimentally investigated by many researchers to study the effect of operating and geometrical parameters on heat transfer and fluid flow characteristics. The availability of highly advanced computer hardware and development in numerical methods, encouraging the future researchers to carry out the simulations of solar air heater using various roughness geometries with different ranges of operating and geometrical parameters. CFD is emerging as an efficient tool to detect the optimum configuration of rib for its maximum thermo hydraulic performance before carrying out actual experimentation. This article discusses different approaches used to investigate the thermal performance of solar air heater. The computational approach, i.e. CFD methodology is discussed using the reference of commercial CFD software ANSYS FLUENT. The main aim of the article is to present a detailed review of the literature that deals with the application of CFD in the design of solar air heater. The paper has a concise summary of each reviewed article in the form of, type of computational domain (2D/3D), turbulence model used, type of CFD commercial software used, range of operating and geometrical parameters and best results obtained from CFD. The article also tabulated the optimum values of relative roughness pitch ( P / e ) and relative roughness height ( e / D ) for maximum heat transfer enhancement in roughened solar air heater duct.

An experimental and two-dimensional computational fluid dynamics (CFD) analysis of a solar air heater has been carried out using chamfered square rib as artificial roughness on the absorber plate. The relative roughness pitch (P/e = 7.14–17.86), chamfer angle (α = 0°–40°), Reynolds number (Re = 3800–18,000) and relative roughness height (e/D = 0.042) are chosen as design variables for analysis. A uniform heat flux of 1000 W/m2 is maintained on the surface of absorber plate. CFD code, ANSYS FLUENT 14.5 with renormalization group k-e model was chosen. An enhancement in Nusselt number and friction factor with decrease in relative roughness pitch (P/e) is presented and discussed with reference to experimental and CFD analysis. The effect of chamfer angle and Reynolds number on enhancement of Nusselt number and friction factor is also presented. Optimum configuration of roughness element for artificially roughened solar air heater has been determined in terms of thermo-hydraulic performance parameter. The chamfer angle of 20° on square rib and relative roughness pitch of 7.14 provide best thermo-hydraulic performance of 2.047 considering the maximum heat transfer and minimum pressure drop.

The performance characteristics of a solar heater and heat exchangers can be effectively improved by using artificial roughness in different forms, shapes and sizes. Artificial roughness is provided in the form of different geometries such as ribs, dimple shape roughness, wire mesh, baffles, delta winglets etc. To determine the effect of these geometries on thermal performance of solar heaters and heat exchangers, several experimental and numerical studies have been carried out by various researchers. In this paper, an attempt has been made to review various roughness element geometries employed in solar air heaters and heat exchangers in terms of heat transfer, friction factor and flow simulation techniques. Correlations developed for heat transfer and friction factor for different roughness geometries by various investigators in solar air heaters are presente.

The cross-flow heat exchanger is a special type of heat exchanger involving the exchange of heat in the case of two fluids flowing in an orthogonal direction. The heat exchanger often comprises of a number of cylinders carrying hot fluid, along with the colder fluid flowing across/over the tubes or cylinders. The system also comprises of additional fins across the tube cross-section along with delta winglets so as to generate the additional turbulence for increasing the rate of heat transfer. The addition of vortex generators helps in promoting system miniaturization. Moreover, the implementation of the passive techniques in cross-flow heat exchangers significantly escalates the pumping power requirement. Thereby, the objective of this paper is to carry out a review on the recent developments and their potential candidature for improving the thermal performance of heat exchanger. The latest state-of-the-art developments are deeply discussed with its evaluating parameters and some recommendations are made for further investigation in this area.

This study reports the effect of embelin (1) on cutaneous wound in streptozotocin (STZ)-induced diabetic rats. The effect was studied using excision, incision, and dead space models. In diabetic rats, topical application of embelin 5% (w/w) ointment showed a significant increase in wound contraction and better epithelialization, thereby facilitating the healing. Embelin was also active by the oral route (25 and 50 mg/kg) in the incision and dead space wound models. In incision wound model, wound granulation tissues were removed on 8th post-wounding day, and the hydroxyproline, hexosamine, total protein, and DNA contents were determined. In STZ diabetic rats, topical and oral applications of embelin showed an increase in hydroxyproline, hexosamine, total protein, and DNA contents. It also showed a significant increase in wound breaking strength. Embelin significantly increased granuloma tissue weight and breaking strength in dead space model. These results indicated that embelin accelerated wound healing in diabetic rat.

The current study was carried out with an attempt to separate similarly structured title drugs by liquid chromatography. Spectrophotometric techniques were generally insufficient under these conditions because of the spectral overlapping of drugs with similar functional groups. The pharmaceutical drugs prazosin, terazosin, and doxazosin contain the same parent quinazoline nucleus, thus making it especially difficult to separate the former two drugs because of their very similar structures. A simple and sensitive method for the routine determination of these drugs in pharmaceutical formulations was attempted. We found that the mobile phase consisting of A: ACN–diethylamine (0.05 ml), B: methanol, and C: 10 mM Ammonium acetate separated these drugs effectively. Separations were carried out on a new Kromasil C18 column (250 × 4.6 mm, 5.0 μm) at 254 nm wavelength. The calibration curve was found to be linear in the range of 2–500 μg/ml. The stated method was then validated in terms of specificity, linearity, precision, and accuracy. Additionally, the proposed method reduced the duration of the analysis.