Effect of Radiation on Mixed Convection Inside a Lid-Driven Square Cavity With Various Optical Thicknesses and Richardson Numbers

This work studies numerically the effect of the radiative heat transfer on the flow and thermal behaviors of the mixed convection in a lid-driven square cavity in the presence of radiatively emitting, absorbing, and isotropically scattering gray medium. The Boussinesq approximation has been used in modeling the governing equations, and the SIMPLE (semi-implicit method for pressure-linked equations) algorithm is used in coupling the velocity and pressure fields. The radiative transfer equation and the governing equations have been solved respectively by the discrete ordinates method and the finite-volume method in order to obtain the temperature, velocity, and heat flux distributions in the participating medium. The present numerical simulations are validated by comparison with several earlier studies. Then, the temperature and velocity distributions and Nusselt numbers have been analyzed in a broad range of optical thicknesses from 0 to 100 and Richardson numbers from 0.01 to 100. The results show that the radiation has a significant role on the flow and thermal behaviors in the lid-driven square cavity. As an example, we can refer to a sweep behavior that is detected in the velocity distributions of the lid-driven cavity.     

Coupled electromechanical analysis of MEMS-based energy harvesters integrated with nonlinear power extraction circuits

Microsystem Technologies - Application of piezoelectric materials in vibration energy harvesters is expanding rapidly, especially in MEMS-based devices, due to their uncomplicated fabrication...     

A pore network study of evaporation from the surface of a drying non‐hygroscopic porous medium

The phenomena occurring at the surface of a porous medium during drying in the capillary regime are investigated by pore network simulations. The impact of the formation of wet and dry patches at the surface on the drying rate is studied. The simulations indicate an edge effect characterized by a noticeable variation of saturation in a thin layer adjacent to the porous surface. Also, the results indicate a significant nonlocal equilibrium effect at the surface. The simulation results are exploited to test Schlünder's classical model which offers a simple closure relationship between the evaporation rate and the degree of occupancy of the surface by the liquid. In addition to new insights into the surface phenomena, the results open up new prospects for improving the continuum models of the drying process. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1435–1447, 2018     

Development of novel method for prediction of gas density in operational conditions

The performance of gas industries is extensively function of gas properties such as gas density. Due to this importance in the present work, a novel grid partitioning based fuzzy inference system method applied to predict gas density base on pressure, temperature and molecular weight of gas. To this end, the required experimental data are collected from reliable sources. Different comparison scenarios are used to evaluate the ability of model. The coefficients of determination (R²) for training and testing phases are calculated as 0.9985 and 0.9980 respectively. The determined indexes and graphical evaluations show that predicting model can estimate gas density in high degree of accuracy. According to the obtained results, the predicting model can be used as a simple and powerful software in gas industries to predict different processes.     

Filtered gradient active fuzzy neural network noise control in an enclosure backed by a clamped plate

The performance of conventional linear algorithms in active noise control applications deteriorates facing nonlinearities in the system mainly because of loudspeakers. On the other hand, fuzzy logic and neural networks are good candidates to overcome this drawback. In this paper, the acoustic attenuation of noise in a rectangular enclosure with a flexible panel and five rigid walls is presented both theoretically and experimentally using filtered gradient fuzzy neural network (FGFNN) error back propagation algorithm in which the secondary path effect is implemented in derivation of updating rules. Considering this effect in updating rules leads to faster convergence and stability of the active noise control system. On the other hand, the primary path in the investigated system comprises an identified nonlinear model of loudspeaker inside the aforementioned box, parameters of which vary with the input current. The loudspeaker is identified using series‐parallel neural network model identification method. As a comparison, the performance of filtered‐x least mean squares and FGFNN algorithms are compared. It is observed that FGFNN controller exhibits far better results in the presence of loudspeakers with nonlinear behavior in primary path.Copyright © 2012 John Wiley & Sons, Ltd.     

Combined method of complex coacervation and electrospray for encapsulate preparation

Encapsulate beads composed of alginate and chitosan as shell and bovine serum albumin (BSA) as core were prepared by combined method of complex coacervation and electrospray. The main objective of this work was to produce mono‐sized and spherical capsule of chitosan‐alginate with controlled sizes of capsules and shell. However, the effects of applied voltage, flow rate, and molecular weight of chitosan were investigated on the size, size distribution, membrane thickness of the prepared capsules, as well as the release rate of BSA. The results revealed that by the method developed in this study, it was possible to produce spherical capsules with controlled size and narrow size distribution. Increasing the voltage and decreasing the flow rate reduced the radius of capsule and its shell thickness from 2.09 mm to 750 μm and from 1.31 mm to 490 μm, respectively. Furthermore, the molecular weight of chitosan had no significant effect on the capsules' size and the release rate of BSA, whereas the rate of BSA release was increased with increase of the voltage. The later effect would be due to the increase of shell porosity at the higher voltages. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A comparative study on the free volume theories for diffusivity through polymeric membrane in pervaporation process

In this work, free volume theories are coupled with a thermodynamic model and generalized Fick's law to develop a mass transfer model based on solution‐diffusion mechanism for pervaporation process with a hydrophobic polymeric membrane. The Wesselingh, Fujita and Vrentas‐Duda's theories are used to calculate concentration‐dependent diffusion coefficient of permeants inside polydimethylsiloxane membrane. The sorption and pervaporation experiments on aqueous ethanol solutions are performed to validate the sorption and pervaporation models. The results reveal that the proposed models are able to predict influences of feed concentration and temperature as well as permeate‐side pressure on partial fluxes through the membrane. The comparative investigation indicated that Wesselingh's free volume theory underestimated the diffusion coefficients inside the membrane and the accuracy of the model used this theory is very low for prediction of the permeation flux. Generally, Fujita and Vrentas‐Duda's theories are found to be much more accurate especially for dilute aqueous feed solutions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40581.     

Environmental impacts of desalination on the ecology of Lake Urmia

Lake Urmia, the second largest hypersaline lake by area in the world, has fluctuated in salinity over time, but in recent years, it has reached a maximum of 340 g/L. The lake is the main habitat for the endemic Iranian brine shrimp, Artemia urmiana, and is a protected aquatic environment. Efforts have been made by the Iranian government to enhance the diversity of its wildlife. One approach has been to look for a method to reduce the salt content of the lake. We investigate the feasibility of this by first considering the water chemistry of Lake Urmia and then the various technologies used to extract salt from marine and brackish waters. Average concentrations of Na, Mg, K, Ca, Cl, SO₄, and HCO₃ were 125 g/L, 11.3 g/L, 2.63 g/L, 0.55 g/L, 216 g/L, 22.4 g/L, and 1.38 g/L, respectively, and cations and anions were balanced, However, Lake Urmia waters have a ‘very high’ salinity hazard and a high sodium adsorption ratio (SAR). Moreover, the saturation index (SI) for each of the major cations was greater than zero, indicating that the water in Lake Urmia is supersaturated, and precipitation is likely. The extraction of available salts from the lake for the use in petrochemical industries is economically feasible. However, technologies based on removing salts by distillation or reverse osmosis and then using this fresh water to dilute lake salinity are problematic. A better strategy would be better to allow more fresh water to reach the lake rather than creating fresh water through reverse osmosis and distillations processes. While concerns have been raised about the salinity tolerance of A.urmiana, it has successfully tolerated various salinity ranges from 166 to 340 g/L, and so the species is not threatened, unless the lake desiccates. Because the lake is saturated with salts, it seems unlikely that salinity could increase much higher.     

Clarification of pomegranate juice by microfiltration with PVDF membranes

Microfiltration was used to clarify pomegranate juice using two polyvinylidene fluoride membranes with pore sizes of 0.22 and 0.45 μm. Changes were studied in the chemical properties of the juice after passing through each membrane. Characteristics such as turbidity changed for both membranes (more than 95%). The permeate flux decreased over time as a result of membrane fouling. The degree of decline in the membrane with pore size of 0.22 μm was greater than another one. In both membranes, fouling resistance increased over time from 5 × 10⁹ m²/kg to 4.43 × 10¹⁰ m²/kg for 0.22 μm and to 1.29 × 10¹⁰ m²/kg for 0.45 μm after 45 min. This increase had a sharp slope in the first stages of the testing. Fouling index changes over time showed similar behavior. Scanning electron microscopy images showed that the cake layer had the greatest impact on membrane fouling after processing by preventing turbid components from entering pores.