Iranian Journal of Chemical Engineering (IJChE)

Abstract The aim of the present work was to evaluate the effect of soy protein isolate (SPI)-gum arabic (GA) composite on the stability of beverage emulsion prepared as the orange oil-in-water (O/W) emulsion. Response surface methology (RSM) was used to study the influence of the two independent variables, each at three levels (homogenization speed
as x1 (1500, 15700, and 30000 rpm) and GA:SPI ratio as x2 (1, 0.6, and 0.2) on the two dependent variables namely, size of the emulsion droplet (EPS) as y 1 and emulsifying activity (EA) as y 2 . The results were discussed on the two empirical models obtained. Analysis of variance (ANOVA) showed a high coefficient of determination (R2 ) value of 0.937 and 0.979 for EPS and EA, respectively, ensuring a satisfactory adjustment of the second-order regression model with the experimental data. The negative sign for the regression coefficient of x1, indicated that size of the emulsion droplet increased with the decreased level of factor x1 from 30000 to 1500 rpm, while EA increased with increased levels of factor x1 . Thus, GA: SPI ratio with the lowest amount of GA along with the homogenization speed at high level, gave the smallest size of emulsion droplet (1μm). This size corresponded to the high emulsifying activity and stability. Sodium chloride and freeze-thaw cycling are two environmental factors affecting emulsion stability. Results of freeze-thaw cycling test showed a large decrease in the EA of the sample prepared with a low level of SPI:GA ratio and no dependence of the EA on the NaCl concentrations in the range of the tested levels was observed (50-150 mM). Long-term storage stability test (storing the emulsion samples at 4, 16, and 30ºC each for 8 days) showed the size of the emulsion droplet increased with the storage time. Results of use of SPI as a readily available plant source of protein for preparation of the encapsulant for orange oil-emulsion were encouraging, especially when one considers the dependence of the beverage industry on the unreliable source of supply of GA. RSM was successfully applied for the modeling of the emulsion preparation.

Abstract In this work, the effects of air stream direction in the channels of indirect evaporative cooler (IEC) on system performance have been investigated. In addition, the dependence of system performance on outdoor air temperature and relative humidity has been studied to determine the allowable conditions for proper operation of the system, with respect to thermal comfort criteria. For this; the different types of IECs were investigated using the CFD technique. Several codes were defined in MATLAB for modeling the parallel flow, counter flow and cross flow layout. The CFD program was validated against theoretical data from the literature and good agreement between the prediction and measurement was achieved. The calculated results show that when the air relative humidity is lower than 70%, the system can prepare a good indoor condition even at 50oC, and a higher performance is achieved by using the IEC with counter current configuration. The results showed that IECs can be successfully used in hot and humid climates to fulfill the indoor thermal comfort conditions.

Abstract One of the important aspects of distillation control design is the choice of a good control structure since improper choice of manipulated/controlled variable pairing can lead to poor control performance. In this paper, comparison and selection of structures is mainly based on the plant condition number. Columns with reflux ratios less than unity or greater than five show large condition numbers. For the ratio structures, the results show that double-ratio structures such as the (D/(L+D))(V/B)-structure have smaller values of the relative gain array element (λ11 ) compared with single-ratio structures, such as the (D/(L+D))V-structure. In addition, the relative values of λ11 corresponding to the values of minimized condition number (γmin), instead of condition number (γ), provides a better basis for comparison. It has also been shown that the maximum singular value (σmax) of the relative gain array (RGA) is a good criteria between ratio and non-ratio structures, and also between various ratio structures selection. At a constant reflux ratio, columns with smaller values of σmax show small values of γmin . Finally, a frequency-based analysis is performed for the selection of the appropriate structure. The analyses show that although the DV-structure has a relatively small value of condition number with respect to other structures, the value of λ11 is far from unity. In contrast, ratio structures have λ11 values near unity. Frequency-based behavior of ratio structures show small oscillations at higher frequencies (> 1 rad/min), while the conventional LV-structures show large oscillations for smaller values of λ11 at higher frequencies.

Abstract Production optimization ensures that wells and facilities are operating at their peak performance at all times to maximize production. This paper describes a procedure, to develop Inflow Performance Curves, Tubing Performance Curves and Choke Performance Curves, for one of the Iranian southern oil wells, from the results of a multiphase flow simulator (PIPESIM). The goal of this project is to optimize the production from one of the southern Iranian oil fields. Increasing the choke size leads to maximizing production, and causes an optimum reduction in wellhead pressure and bottomhole flowing pressure. Controlling flow patterns in all sensitivity analysis play a major role in selecting the proper variables. Using 7in. OD tubing size rather than 95/8 in. casing size and selecting 9/16 in. choke size rather than 7/16 in., the wellhead pressure between 700 to 1180 psia will be the result and optimum range in selected well No. 305b. The results show a successful experience in optimization of well No.305b and the production can be increased from 2000 BOPD to 3150 BOPD.

Abstract A satellite with a passive thermal control system mainly uses thermal coatings and paints to maintain temperatures within safe operating limits. Satellite coatings, exposed to harsh space environments such as ultraviolet (UV) radiation and atomic oxygen (AO), undergo physical damage and thermal degradation, which must be considered by the satellite thermal designer for design optimization and cost reduction. In this paper, we have briefly reviewed the effects of space environment effects on degradation of satellite coatings. To study the consequences of paints degradation on the thermal performance of satellites with passive thermal control, a small cubical satellite in Low Earth Orbit (LEO) has been considered. The satellite’s bottom surface faces the Earth, and the top surface faces deep space. The satellite’s lateral sides are covered with solar panels, and the top surface, which acts as the satellite radiator, is covered with white paint. The satellite orbit is sun-synchronous with an inclination angle of 99º. Three radiator coatings (Chemglaze A276 and SG121FD white paints, and AZW-11LA ceramic white coating) have been used in turn, and the satellite has been thermally analyzed for each case. In these analyses, beginning-of-life and end-of-life optical properties have been used to predict the satellite temperatures, before and after degradation of the coatings. The analyses results show the importance of stability of optical properties of the thermal coatings for the long-term thermal control of satellites. On considering the rate of thermal performance degradation, lower production cost, and ease of application on satellite surfaces, SG121FD white paint is recommended as a suitable satellite radiator paint for use in satellite thermal control applications, with the same design requirements, mission life and orbital parameters as the satellite considered in this study.

Abstract In this study a mathematical model is developed in order to simulate fluorination reaction of uranium dioxide which leads to the production of uranium hexafluoride. The model considers homogeneous reaction for intermediate solid and a heterogeneous one for unreacted shrinking core. Also, this study tries to clearly show the shortcoming of some of the well-known models that take heterogeneous reactions for both solids. In fact, one may not trust the accuracy of those models due to the importance of diffusion phenomena into the intermediate solid and the reaction taking place within it. On the other hand, neglecting the undeniable effects of some operating conditions such as temperature and particle sizes on gas concentration distribution and reaction rates may introduce large deviations. In this study, the governing equations are developed on the basis of the mass conservation law and solved numerically. Besides, for the first time,
some dimensionless equations and groups are introduced to predict reaction rates and amounts of the main and intermediate products for use in numerical procedures. Comparing the model results with corresponding experimental ones represents the desirable preciseness of the model. After validation of the model, the effect of some operating variables such as temperature and initial size of the particle are investigated on the reaction rates and conversions.