An 1D hydrodynamic model has been simulation and developed for gas hold-up and liquid circulation velocity prediction in air-lift reactors. model is based on momentum balance equations and has been adjusted to experimental data collected on a pilot plant reactor equipped with two types of gas distributors and using water as the liquid phase.The model equations described previously constitute a set of non-linear equations which are solved by an iterative procedure (v.b) (c plus). This model has also been combined with mass transfer and the kinetics of a chemical reaction to yield a complete model of the performance of a reactor.

Ophthalmomyiasis is pathology of eye due to presence of fly larva, which rarely occurs in the world, and most cases has been reported in developing countries. These days incidence of Ophthalmomyiasis has been decreased in Iran. Most cases of Ophthalmomyiasis caused by presence of fly Larvae Oestrus Ovis.In summer 2011, a fourty year old rural woman with a good hygine presented to Ophthalmology department of Rouhani Hospital. She had no background of any disease.After physical examination EXTERNAL Ophthalmomyiasis was diagnosed. all seven larva has been removed, Topical antibiotic and corticosteroid were prescribed for daily use. Two days later in follow up the eye was asymptomatic.

An airlift reactor with the EXTERNAL LOOP (EXL ALFR) is a widely used modified version of a Bubble Column Reactor (BCR). An EXL ALFR can also be used for a three-phase system with the solid phase in a packed or fluidized form. An EXL ALFR provides design flexibility for conventional chemical reactions as well as biological reactions. Shear is an important factor for the reactors handling immobilized enzymes. In the current investigation, the effect of the design variables, like gas hold-up, the velocity of circulating liquid, and the distribution of bubble dimension, was compared for an EXL ALFR and an EXTERNAL LOOP airlift reactor with a packed bed (EXL ALFR-PB). Particle Image Velocimetry (PIV) was employed for the liquid axial velocity in the downcomer of the reactors, and the computational fluid dynamic with the Population Balance Model (CFD-PBM) was employed. The minimum percentage of errors of 2.3% and 1.2% and the maximum of 4.2% and 3.4% were obtained for the experimental and predicted values of gas hold-up in the EXL ALFR and EXL ALFR-PB, respectively. For the velocity of the circulating liquid, the predicted and experimental values of their minimum percentage error were 1.1% and 0.5% and a maximum of 4.3% and 4.5% in EXL ALFR and EXL ALFR-PB, respectively.  Also, the pressure drops calculated from the Ergun equation and CFD simulation had a 0 to 4% difference, indicating good agreement.

Background and Objective: In This study the impacts of operating conditions such as aeration rate, the downcomer-to-riser cross-sectional area ratio (Ad/Ar), and liquid phase properties on the hydrodynamics and volumetric mass transfer coefficient in three-phase airlift reactors was investigated. Method: Experiments were conducted in EXTERNAL LOOP air-lift reactor with downcomer to riser cross-sectional area ratio (AD/AR=0. 14) and internal air-lift reactors with downcomer to riser cross-sectional area ratios 0. 36 and 1. Air and Water were used as gas and liquid phases, respectively and activated sludge is used as the solid phase. Findings: The liquid circulation velocity, gas holdup and mass transfer coefficient increased with an increase in the superficial gas velocity, decrease the sludge concentration and decrease downcomer to riser cross-sectional area ratio. The maximum amount of gas hold up, 0. 178 in EXTERNAL air-lift reactor with 1%(w/w) activated sludge in superficial gas velocity 0. 24(m/s) was observed. A model to predict the effect of activated sludge concentration, the superficial gas velocity and the downcomer-to-riser cross-sectional area ratio on the mass transfer activated sludge airlift reactors provided which with the experimental results are in good agreement. Discussion and Conclusion: The evaluation of internal and EXTERNAL reactors performance at different concentration and superficial gas velocity show that the air-lift reactor with EXTERNAL LOOP has better performance in comparison with internal airlift reactors.

A common method for controlling a group of parallel converters in decentralized control strategy structure in an island microgrid, the use is the droop-down characteristics of frequency ω-P and voltage E-Q. However, the problem with using this method is that the reactive power is not properly distributed (in proportion to the capacity of the micronutrients) between the micronutrients, which may lead to overload in the converters. Microgrids may also suffer from dynamic stability problems such as power fluctuations, which can be increased by switching between active and reactive power control. To avoid this problem, the X / R ratio of transmission lines is an important parameter that should be carefully considered in the design of micronutrient controllers. By linearizing and simplifying conditions, the control system conversion function model becomes a single input-single output system, which is efficient enough to show the relationship between control parameters such as slope of droop characteristics and derivative sentences, virtual impedance, and voltage controllers. Using this model, stability conditions for different parameters are analyzed. Also, to improve power distribution stability, common droop strategies are modified by adjusting the slope as well as adding nonlinear sentence sections. This approach reduces the coupling between active and reactive power control and reduces the dependence of power distribution on grid parameters such as the X / R ratio. To evaluate the reliability of the proposed model, the simulation results in a sample island microgrid in MATLAB software are presented.