Current Biochemical Engineering (Discontinued) - Volume 6, Issue 2, 2020

Background: Enhancing the heat transfer rate in solar collectors is an essential factor for reducing the size of the system. Yet, various methods have been presented in the literature to increase the heat transfer rate from an absorber to the heat transfer fluid. The most important methods are: the use of evacuated receivers, addition of swirl generators/turbulators and use of various nanofluids as the heat transfer fluid. Objective: The current study reviews the achievements in the enhancement of solar collectors’ heat transfer process using various types of nanofluids. The review revealed that the most widely employed nanoparticles are Al2O3 and Carbon nanotubes (CNTs) and the most popular base fluid is water. Most of the investigations are performed on indirect solar collectors, while recently, the researchers focused on direct absorption methods. In the indirect absorption collectors, the thermal conductivity of the working fluid is essential, while in a direct absorption collector, the optical properties are also crucial. Optimization of the optical parameters along with the thermophysical properties of the nanofluid is suggested for the applications of solar collector.

Background: Friction Stir Welding (FSW) is an efficient process for solid-state joining of two different material without melting by using a non-consumable tool. FSW process was developed for the modification of metallic material microstructure. FSW requires a precise investigation of the process, microstructure, and the welds mechanical properties in order to be used in the fabrication of high- quality engineering components. Through the efforts of improving the weld's mechanical and microstructural properties and conveying the current knowledge of the friction stir to other applications, multiple new technologies have been developed over the time. One of the latest methods to fabricate high performance joints or Nanocomposites alloys is the addition of nano- reinforcements to the joint in Friction Stir Welding (FSW) or the metal matrix in Friction Stir Processing (FSP). Objective: In this study, an overview of the effect of nanoparticles on microstructural and mechanical properties of the FSW/ FSP joints is presented. The review revealed that the most widely employed additions are SiC, SiO2, Al2O3, and graphite nano-powders. Microstructural evolutions, such as grain size, second phase particles, and reinforcement distribution, usually are investigated using optical methods and Scanning Electron Microscopy (SEM). Furthermore, the mechanical properties of the joints, such as tensile strength, hardness, and wear performance, are also investigated. Based on most of the researches, microstructural evolution associated with adding nanoparticles led to improve the joints mechanical properties.

Background: The Fe3O4 nanoparticles have been highly regarded in recent years due to their unique properties and different applications. Magnetic separation capability of Fe3O4 nanoparticles provides an environmentally friendly procedure for the synthesis of this nanoparticle and its derivatives. Objective: There are many methods for synthesizing magnetic nanoparticles, and the properties of these nanoparticles are largely dependent on their synthesis method. Magnetite has many applications in various fields, one of the most important of which is the application of electrochemical sensors. These nanoparticles attached to the surface of different electrodes and used for the sensitive and selective electrochemical determination of trace amounts of several combinations. In this review paper, recently suggested synthesis methods of Fe3O4 and its derivatives and their electrochemical application are discussed.

Background: Rubber vulcanization is a consolidated chemical process to enhance the mechanical properties of the polymeric material by sulfur crosslinking of the polymer chains, such as rubber. Vulcanization Activators are important rubber processing additives that activate sulfur cure and improve the efficiency of sulfur-based cure systems. The most common activator is zinc fatty acid ester that is often formed in-situ by the reaction of fatty acid with zinc oxide. Although zinc is one of the less harmful heavy metals, according to European Council Directive 2004/73/EC, the reduction of zinc level in the environment has become an important task because of its toxic effect on aquatic organisms. The current study reviews the research achievements in the field of reducing the consumption of micronutrients of ZnO particles based on the use of nanoparticles instead of them in the polymer industry. Among the proposed methods, due to the less environmental effects of magnesium oxide, the use of MgO nanoparticles instead of zinc oxide has also achieved good results. Objective: The aim of this paper is considering suggested different methods on the reduction of using ZnO particles in related industries, the use of ZnO nanoparticles has had better results than its particles. In addition, due to the less environmental effects of magnesium oxide, magnesium oxide nanoparticles can be used instead of micronutrients of zinc oxide. Overall, the results of various investigations show that reducing the diameter of the zinc oxide particles reduces the amount required for curing the rubber and thus reduces its toxic effects. Also, the use of magnesium oxide nanoparticles instead of zinc oxide in different concentrations is investigated.

Background: Vegetable oil of Fatty Acid Methyl Esters (FAME) that is obtained by triglycerides of transesterification in the presence of methanol, recently, has been highly regarded by scholars for use in diesel engines. These oils can be used as biodiesels in diesel engines and have various benefits (these fuels are renewable, biodegradable, and nontoxic). Objective: In this work, many studies are reviewed in the field of using vegetable oils as biodiesel in diesel engines. Moreover, a simulation study is conducted to compare oxygen and peak pressure of a diesel engine fueled by three different biodiesels in comparison to diesel fuel. We have examined the chemical ignition delay time and kinetic viscosity of biodiesel in the combustion process of diesel engine and the effects of these factors are evaluated on air–fuel mixing and subsequent combustion.

Background: Electrochemical sensors are widely used for the determination of drugs and food compounds. In recent years, the amplification of electrochemical signals with nanomaterials, especially Carbon Nanotubes (CNTs) has created a major revolution in electrochemistry. Objective: The present mini-review paper focused on studying the role of CNTs as conductive mediators for the fabrication of highly sensitive electrochemical sensors. CNTs, with high conductivity and good ability for modification with other materials, are interesting candidates for improving the sensitivity of electrochemical sensors. CNTs or their derivatives are suggested for different applications in electrochemistry and especially analytical biosensors. This review is aimed to discuss the conductivity feature of CNTs in electrochemical sensors.

Background: The development of viable alternative fuel sources is assuming a new urgency in the face of climate change and environmental degradation linked to the escalating consumption of fossil fuels. Lignocellulosic biomass is composed primarily of high-energy structural components such as cellulose, hemicellulose and lignin. The transformation of lignocellulosic biomass to biofuels requires the application of both pretreatment and conversion technologies. Methods: Several pretreatment technologies (e.g. physical, chemical and biological) are used to recover cellulose, hemicellulose and lignin from biomass and begin the transformation into biofuels. This paper reviews the thermochemical (e.g. pyrolysis, gasification and liquefaction), hydrothermal (e.g. subcritical and supercritical water gasification and hydrothermal liquefaction), and biological (e.g. fermentation) conversion pathways that are used to further transform biomass feedstocks into fuel products. Results: Through several thermochemical and biological conversion technologies, lignocellulosic biomass and other organic residues can produce biofuels such as bio-oils, biochar, syngas, biohydrogen, bioethanol and biobutanol, all of which have the potential to replace hydrocarbon-based fossil fuels. Conclusion: This review paper describes the conversion technologies used in the transformation of biomass into viable biofuels. Biofuels produced from lignocellulosic biomass and organic wastes are a promising potential clean energy source with the potential to be carbon-neutral or even carbonnegative.