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Research Subject: Nowadays, application of biosurfactants in microbial enhanced oil recovery (MEOR) have aroused much attention and several investigations have been conducted on this field. But their performance in comparison to synthetic surfactants in enhanced oil recovery has little been studied. Most of these researches are limited to comparison of one produced biosurfactant with only a chemical surfactant. To fill this gap, in this research, the potential use of a rhamnolipid type biosurfactant  in MEOR was compared to several conventional synthesized surfactants: SDS, SDBS, CTAB and DTAB.
Research Approach: Since the main goal of this research is the comparison between produced biosurfactant and conventional chemical surfactants in oil recovery, several flooding tests were conducted and involved mechanisms were investigated. All of tests were conducted in an oil wet glass micromodel saturated with heavy oil at ambient condition. Injected solutions were prepared at critical micelle concentration of surfactants. During the flooding tests, high quality pictures were taken with a camera connected to the computer to monitor the motion of injected solution in the micromodel.
 Main Results: 40% oil recovery was achieved after biosurfactant flooding while SDBS, SDS, CTAB and DTAB resulted 36%, 34%, 32% and 29% oil recovery, respectively. For mechanistic study, the surface tension (ST) and viscosity measurements were performed and contact angle was determined. The surface tension reduction, wettability alteration towards more water-wet condition and increasing the ratio of injected fluid viscosity to oil viscosity were dominant mechanisms. The rhamnolipid was more effective than other surfactants in reduction of surface tension and altering the wettability towards favorable water-wet conditions. It decreased the surface tension of water from 72 to 28 mN/m, which was the least comparing to other surfactants and increased the capillary number about 19.4 times greater than in water flooding. Additionally, it changed the contact angle from 106 to 6, 94.3%, the widest change among applied surfactants. 

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Iran is geographically located in the dry belt of the earth and this has led to a natural shortage of water. Isfahan province in the center of the country with a long-term average annual rainfall of about 150 mm is also severely limited water resources. Regardless of this, for about half a century, due to various reasons, water consumption in this province, which is mainly due to the establishment of large national industries and their chains, as well as agricultural development and population growth and urbanization, water consumption has increased greatly and lack the appropriateness of water resources and consumption has increased over time. Out of 35 plains of the province, 27 plains are forbidden or critically forbidden. Since no effective practical action has been taken to control this situation, various consumers have tried to compensate part of this mismatch by digging deep and semi-deep wells, both legally and illegally, using underground resources. The lack of replacement of groundwater aquifers and the continuous decline of their water level have caused the phenomenon of subsidence and their permanent destruction, so that even if there are sufficient water resources, these aquifers are no longer able to hold water. This causes the destruction of the most important foundation of the life in subsidence areas, which is the water sources, to be lost forever, which has many environmental, human and political consequences. Currently, subsidence threatens many parts of the province's infrastructure, such as national communication infrastructure such as Shahreza Road near Mahyar, Meshkat Road near Kashan, Bandar Abbas-Tehran Railway near Zavareh, Isfahan-Shiraz Railway near Mahyar and Marvdasht. Isfahan airport as well as other industrial, religious and historical infrastructures such as industrial towns of the province (Jafarabad industrial town of Kashan, Aran and Bidgol); Religious and tourist places (Imamzadeh Agha Ali Abbas, Naqsh Jahan Complex, and historical stairs of the province); Public places Naghsh 11 bsidence is spreading in almost all areas of Isfahan province, which threatens the survival of the province in various dimensions and it is necessary to think of serious practical measures in this area.

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In this paper, the efficiency of Proton membrane exchange (PEM) fuel cell system by using ejector for returning the additional fuel in the fuel supply circuit and comparison with conventional systems, with compressor in fuel supply circuit, are studied. For this purpose a semi - analytical developed model for calculating the amount of efficiency increment, as well as the amount of power saving as a result of employing ejector in the fuel cell return line is provided by extending the previous models. In this developed model the important stack design parameters and ejector design parameters are correlated by presenting a new dimensionless parameter. The results for a typical fuel cell show that the amount of efficiency increment at different values of current density is different and there is a maximum point for it. The amount of power saving as a result of employing ejector compared with fuel cell power is considerable and will increase with increasing the current density. These results indicate that the ejector for those applications that require high power (for instance the transport applications) is more efficient.