دوماهنامه مهندسی شیمی ایران
پیاپی 124 (آذر و دی 1401)

Corrosion is one of the prevalent problems in industries such as oil and gas industry. This renders the corrosion prevention associated with the economic concerns. Due to the need for continuous operation of oil and gas industry processes and high maintenance costs, using corrosion inhibitors is one of the best approaches to deal with industrial corrosion. Nanoparticles with a higher specific surface area have a much higher adsorption coefficient than ordinary particles on the metal surface. For this reason, their use as an inhibitor has received much attention in recent years. Therefore, in this study, using different types of corrosion inhibitor nanoparticles has been reviewed. According to the aims of the present study on corrosions in the oil and gas industry, at first, different types of common corrosions in this industry have been introduced according to the metal or alloy used in each unit. Then, different nanoinhibitors and their applicability in different environments and operating conditions have been investigated. At the end of this study, various methods of synthesis and characterization of the performance of nanoinhibitors are discussed.</em> </em>

In this study, using Autodesk Moldflow software, the injection molding process of ventilator’s poly (lactic acid) split filters was studied and the effective characteristics of this process were investigated and compared in two samples of crystalline and amorphous poly (lactic acid). The injection pressure for the crystalline sample showed a larger value in the simulation, which was justifiable due to the higher melt viscosity of the crystalline sample than the amorphous sample. The results of this study also showed that the cooling time required for the sample was longer, which was attributed to the difference in temperature distribution between the two samples as well as the difference in their thermal conductivity. Shrinkage and air trapping are other important characteristics in the injection process. The results showed that they were higher for the crystalline sample, which was as expected due to the difference in melt viscosity of the samples and the relationship between crystallization susceptibility and compression of polymer chains. Also, the rheological and thermal properties of selected polymers were analyzed and their relationship with effective injection factors was explained. Finally, the specifications of the injection molding machine suitable for the production of polymer filters were introduced based on the information available in the software.

At present, the emission of carbon dioxide from the combustion of fossil fuels into the atmosphere is one of the biggest concerns for the future. In this regard, the development of clean energy produced from sunlight is one of the appropriate solutions for energy supply in the future. The process of photocatalytic reduction of carbon dioxide is a relatively new method that, collects and stores solar energy to value-added materials, while reduces the negative effects of greenhouse gases through the consumption of carbon dioxide. So far, various semiconductors have been used as photocatalysts in this process. Metal-organic frameworks with unique properties such as band and electron structure, adjustable light absorption and high carbon dioxide absorption are of great interest. In this study, different aspects of these materials and methods to improve their performance, such as the use of optical sensitizers, combination with conventional semiconductors, the use of molecular catalysts and functionalization with amine groups for adsorption of Carbon dioxide has been investigated.

Bioheat transfer plays an important role in analyzing living systems due to its ability to diagnose and treat the disease. Recently, CFD has been increasingly used in biomedical researches of coronary artery disease because of its high hardware and software performance that makes it possible to identify and treat the risk factors for coronary artery disease progression. The purpose of this paper was to investigate blood flow and heat transfer in normal state and in several cases of plaque with a real geometric model of a vessel in an artery by using a commercial Software. Blood is considered as a non-Newtonian and non-compressible fluid and viscosity is modeled using Carreau equations. Unlike many previous studies, the inlet velocity is considered to be transient (pulsatile) and heat transfer has been investigated with the assumptions of constant blood inlet temperature and constant vessels wall temperature and the outlet wall heat transfer has been calculated. A real geometric model in different plaque progressions has been studied as well. Plaque progression in the artery, increases the wall pressure and shear stress, which is very dangerous in cases of severe blockage and may cause high risk of rupture. Increased plaque also reduces the blood heat transfer to the artery’s walls. The results show that there is a change between 10-70% in the dynamic parameters after clogging, but there is no significant change in the outlet temperature.

The process of curing the epoxy resins with hardeners leads to an increase in crosslink density and the properties of the hardened resin are affected, depending on the curing conditions. To improve the final properties of epoxy resins, the use of organic and inorganic nanoparticles has been suggested. One of the recently attended nanoparticles is graphene oxide and its derivatives. In this paper, various models presented in the curing kinetics of epoxy/ graphene oxide hybrid compounds have been evaluated and the reasons for the deviation of laboratory and experimental results with modeling results have been explained. Also, comparison of each of these models with experimental results has shown that Sestak-Berggren and Kamal model has higher adaptation to experimental results than the other models and can be used as a reliable basis for describing the curing process of epoxy resins containing graphene oxide nanoparticles.

In the present study, a space thruster system type monopropellant has been modeled and designed so as to create a Five- Newton thrust force(propulsion) and specific impulse of 220 seconds, with the usage of adjusting motion or changing the position of the satellite. This model consists of two major parts including a catalytic reactor with hydrazine feed, 15% nickel catalyst based on gamma alumina and a convergent-divergent nozzle. The catalytic reactor model is a fixed bed, one-dimensional, steady state and adiabatic with heterogeneous decomposition reactions. The process functions by performing two heterogeneous decomposition reactions of hydrazine and ammonia and converting to light gases (hydrogen and nitrogen) with high temperatures. Subsequently, the thrust force will be obtained by the evolution of the gas from bed and nozzle. The catalyst is made up of wet impregnation method and the required characteristics are specified by quantitative, qualitative and thermal analysis tests. The outcomes of modelling include mass, energy, kinetic, physical and chemical variables in the space propulsion. It is also considered as one of the important advantages of designing the measurement and predicting the variables. So as to determine the performance and validity of the model, indicators such as the thrust force, specific impulse, bed pressure drop and the minimum of ammonia decomposition has been scrutinized with the same kinetic and operating conditions in the designing and experimental model (in atmospheric conditions and static). The obtained results are consistent and have been verified.