Effect of MHD on Nanofluid flow, Heat and Mass Transfer over a Stretching Surface Embedded in a Porous Medium

The steady, laminar, mixed convection, boundary layer flow of an incompressible nanofluid past over a semi-infinite stretching surface in a nanofluid –saturated porous medium with the effects of magnetic field and chemical reaction is studied. The governing boundary layer equations (obtained with the Boussinesq approximation) are transformed into a system of nonlinear ordinary differential equations by using similarity transformation. The effects of various physical parameters are analyzed and discussed in graphical and tabular form. Comparison with published results is presented and we found an excellent agreement with it. Mainly, it found firstly, that an increase in magnetic parameter M decreases both the local Nusselt number and local Sherwood number. Secondly, a great order of the chemical reaction increases the Nusselt and Sherwood numbers

Performance analysis of hybrid PV-diesel-storage system in AGRS-Hassi R’mel Algeria

The main research paper focuses on the optimal hybrid system using HOMER software in the central plant of Hassi R’mel. Indeed, the system is composed of PV panels, a battery bank, and a diesel engine, all of which are used to supply an industrial load. Hence, the present work proposes a solution to optimize the power generated by the power sources, maximize the photovoltaic source use, and minimize the use of the battery bank and the diesel generator. Moreover, the solution aims to guarantee the safe operation of the system components and continuity in the load power supply. These objectives are performed by the minimization of a cost function, in which the power generation cost, the energetic balance, and the environmental parameters are taken into consideration. Among the five solutions, the most optimal system obtained is PV/Diesel/batteries /Grid. This system consists of 1200 KW PV, an 1100 KW diesel generator, 800 units of battery, and an 1100 KW converter. Therefore, to supply the station with 49% of electricity by PV and 51% by diesel while the reduction of emissions is 60%, and 708020 liters of diesel is saved. Applying the sensitivity analysis also showed that renewable resources have an impact on the sizing of PV. When solar radiation increases, the size of renewable energy decreases and the NPC decreases as well. It can, thus, be illustrated that the PV/diesel/battery system is not fully-optimal. This strategy is recommended for industrial system security since it can be used to ensure systems from an energetic and economic point of view

Vibration response simulation of a machine tool spindle system in non-stationary regime.

International audienceBearing and gear are one of the most important mechanical sources for vibration and noise generation in machine tool spindles. In this paper, we study the non-linear dynamic behavior of a machine tool spindle system in transient regime. Driving and driver rotors are, respectively, powered by a motor torque and loaded by the cutting force. They are supported by two identical Rolling Bearings (RBs). Gear excitation is induced by the motor torque and load variation in addition to the fluctuation of meshing stiffness due to the variation of input rotational speed. The dynamic parameters of RBs are modeled by stiffness and damping matrices computed by the derivation of the bearing forces. The equations of motion are solved iteratively using Newmark time integration method. The numerical results of the dynamic responses of the system come to confirm the significant effect of the transient regime on the dynamic behavior of a gear set

Energy and Exergy Analyses of a PWR-Type Nuclear Power Plant Coupled with an ME-TVC-MED Desalination System

International audienceElectricity–water cogeneration power plants are an important tool for advancing sustainable water treatment technologies because they provide a cost-effective and environmentally friendly solution for meeting the energy and water needs of communities. By integrating power and water production, these technologies can reduce carbon emissions and help mitigate the impact of climate change. This work deals with the energy and exergy analysis of a cogeneration plant for electrical power generation and water desalination using real operational data. The power side is a pressurized water reactor (PWR) nuclear power plant (NPP), while the desalination side is a multi-effect distillation (MED) system with a thermo-vapor compressor (TVC) plant coupled with a conventional multi-effect plant (ME-TVC-MED). A mathematical model was implemented in MATLAB software and validated through a comparison with previously published research. The exergy analysis was carried out based on the second law of thermodynamics to evaluate the irreversibility of the plant and the subsystems. In this study, the components of the sub-systems were analyzed separately to identify and quantify the component that has a high loss of energy and exergy. According to the energy and exergy analyses, the highest source of irreversibility occurs in the reactor core with 50% of the total exergy destruction. However, turbines, steam generators, and condensers also contribute to energy loss. Further, the thermodynamic efficiency of the cogeneration plant was obtained as 35.38%, which is more effective than other systems. In the ME-TVC-MED desalination unit, the main sources of energy losses are located in the evaporators and the thermo-compressor (about 50% and 36%, respectively). Moreover, the exergetic efficiency of the ME-TVC-MED unit was found to be low at 6.43%, indicating a high degree of technical inefficiency in the desalination process. Therefore, many opportunities exist to improve the performance of the cogeneration system. © 2023 by the authors

Identification and functional characterization of ten AP2/ERF genes in potato

International audienceEthylene-responsive element-binding factors (ERF) constitute one of the largest transcription factor families in plants. In this study, we describe the cloning and the characterization of ten cDNAs encoding ERF factors from potato. The alignment of their AP2/ERF (Apetala2/ethylene-responsive factor) domain led to the identification of six StERFs (Solanum tuberosum ERFs) and four StDREBs (dehydration responsive element binding). The phylogeny and the sequence characterization allowed the classification of these StERFs into five ERF families. Expression analysis by semi-quantitative RT-PCR of these genes revealed that most of them are induced by hormone treatment such as abscisic acid, ethephon, jasmonic acid and salicylic acid. However, salt stress induced the expression of all StDREB but only three StERF genes. These results suggest that these transcription factors are involved in salt stress response. The StDREB1 and StDREB2 genes showed strong increase in expression in response to drought stress. In an attempt to improve drought tolerance in potato, we overexpressed StDREB1 and StDREB2 in transgenic potato plants (S. tuberosum L. Group Tuberosum) cv. Belle de Fontenay (BF15) and Spunta, respectively. The level of drought tolerance of these transgenic lines was significantly greater than that of wild-type control plants as measured by relative water content H2O2 content, free proline and total soluble sugars. The results suggest that the StDREB1 and StDREB2 as AP2/ERF transcription factors may play dual roles in response to drought stress in potato