Mechanical Engineering Technologies and Applications

In this work, a numerical investigation related to the turbulent forced convection of a water-Al2O3 nanofluid in slot jets impinging on multiple hot components fixed on the lower wall, using different nanoparticle shapes (spherical, blades, bricks, cylindrical and platelets), was carried out. The standard k-ε turbulence model with wall enhanced treatment and two-phase mixture model were used to analyze the fluid flow and heat transfer. The outcomes revealed that the increase in the Reynolds number (Re) and volume fraction of nanoparticles (φ) with all nanoparticle shapes enhanced the heat transfer rate. The platelets nanoparticle's shape significantly contributes to increasing the heat transfer rate compared with other forms. Also, we have found that the two-phase mixture model gives a higher average Nusselt number (Nu) values compared to the single-phase model, and the maximum values of (Nu) is located around the last block due to the second jet's dominance (J2) compared to the first jet (J1). We have compared our results with those found in the literature.

This document examines the experimental application of the gas scavenging membrane distillation (SGMD) process and its advantages and disadvantages. SGMD is the least used configuration in membrane distillation (MD), and it is more expensive to build. Scavenging Gas Membrane Distillation (SGMD) is used to treat complicated solutions with volatile molecules to separate. In this study, heat and mass transport mechanisms, as well as modeling and simulation studies, are systematically reviewed. In SGMD, the main operating parameters are supply temperature, supply flow rate, gas temperature, and gas flow rate. Furthermore, the performance of SGMD is discussed and highlighted. Potential applications and areas in which SGMD could excel are mentioned. Finally, future research opportunities in SGMD are identified. A hollow fiber scavenging gas membrane distillation (SGMD) module is examined in this study. Our SGMD distillation unit has been modeled by mathematical equations and simulated by a runtime program on Matlab software to evaluate the effects of heat transfer and mass transfer. Also, we have found that the heat and mass transfer in our SGMD desalination system is defined by the temperature evolution in the vaporization chamber and the inert gas velocity of the gas. The model predicts a small error of 3.6% with the experimental data reported in the literature, indicating the reliability of simulated results

This work presents the integration of multilayer neural network with an expert system for the automatic choice of the design process of multi-spindle drilling housing. An intelligent design system approach is developed to integrate various phases of the mechanical process including neural network subclasses and MLANN. This solution reduces the time during the design preparation process and to improve production. The automatic choice is carried out in three steps: Firstly, we started with the formulation of training base experiments of the experts of the field as well as the necessary knowledge of expertise, and which is among the general criteria for the choice of the design process. The second step was devoted to the creation of many multi layers NN1…NNm for the choice of the design mode. The final step is related to the application of the outputs as results and an input for chaining by the expert system. This chaining is based on several models based chaining (input data collection) from the neural network results and processing (output results). The results are the kinematics schema of the multi spindle drilling housing.

Solar Energy can be exploited to produce heat and/or electricity. PV/T panels are a good application to produce both photovoltaic and Thermal energies by recovering heat lost with a heat removal fluid (water or air). This induces an improvement of the energetic efficiency of the panel since it is the addition of electrical and thermal outputs. The object of this work was to design a new hybrid solar collector based on the superposition of the thermal and electrical functions instead of their overlay as previously done in most existing systems. Indeed, while thermal energy production requires high fluid operating temperatures, PV electrical energy production needs relatively low operating temperatures. The main goals are to study the effectiveness of our PV/T prototype in terms of thermal energy produced. Moreover, the present system improves the promotion of agro-food micro-enterprises by the integration of miniaturized machines with dryers in remote areas where electric connectivity is not available. In these sites, the farmers can dry the various agricultural products using the prototype we have realized. However, we dealt with an experimental analysis to study the influence of external and internal parameters on the thermal and electrical performance of a photovoltaic thermal hybrid collector PV/T. The system consists of a photovoltaic-thermal (PV/T) air collector of 1.37 m2 . A fan was used to force the convection. Based on the experimental results, it was observed that the thermal and electrical energy was increased when mass flow rate and solar radiation were increased. The thermal and electrical efficiency generated by the system was calculated as 65% and 12.5%, respectively. It was also observed that the outlet air temperature increased. 

In this study, a thermodynamic cycle simulation of a four-stroke spark-ignition engine was conducted to predict the engine performance. The single-zone model was built based on the Wiebe function for the mass fraction burned and Woschni’s model for the convective heat loss. The first law of thermodynamics was applied to describe the engine behavior versus the crank angle. These formulas determine in-cylinder pressure, temperature, mean effective pressure, and effective power. This study was performed to evaluate the effects of the combustion duration on the engine performance characteristics. Simulations were carried out on a 98 cm3 four-stroke SI engine set up at 3600 rpm corresponding to the maximum torque (5.7 Nm). In this study, it was found that under the same operating conditions, accelerating the combustion does not always increase the power delivered by the engine. The best engine performance in terms of compromise between heat losses and power delivered was obtained for the combustion duration corresponding to 60° CA. 

Burning fossil fuels produces a great part of our energy production today and probably it will still do for at least the next few decades. Combustion is encountered in many practical systems such as heaters, power plants, aeronautic engines, buildings, etc. The growing expectations on increasing efficiency and reducing fuel consumption and pollutant emissions make the design of combustion systems much more complex and the science of combustion a rapidly expanding field. Comprehension and analysis of complex physical mechanisms start with the study and control of temperature and species in flame is an important challenge for industrial and environmental issues. We focus our study on a Kerosene, Methane and Gasoil flame simulated with detailed chemistry. The mathematical model is based on the enthalpy conservation between two states, and this model is used with the first law of thermodynamics to define enthalpies of reaction and adiabatic flame temperatures at constant pressure [1, 4]. To reach this objective, we must know the products of complete hydrocarbon combustion and all species of combustion products after dissociation and their molar fractions and equilibrium equations of dissociation reactions. Also, we calculate the elementary equilibrium reactions enthalpy and entropy by using (Bonni Mc Bride et al.) coefficients [2, 3] to compute thermodynamic functions such as specific heat, enthalpy and molar entropy. The obtained system of equations is resolved by Newton Raphson method. Among the obtained results are: To reduce the pollutants (CO2 , CO) and the fuel consumption, the mixture of fuel-air must be lean, therefore, the equivalence ratio must be lower than the unit. According to this study, if the fuel consumption is reduced via the equivalence ratio from 1.1 to 0.95, the combustion temperature remains constant, however, the production of CO will be reduced by 25%.

In this work, the laminar natural convection problem for a Newtonian fluid confined between two concentric ellipses is solved numerically. Two cases of heating are assumed, an inner wall at high temperature (TH ) and an external one at low temperature (TC ), then the opposite. Starting from the case of two circles (ellipses with equal diameters) and arriving at two ellipses, 25 geometries are studied for each type of heating, which gives 50 geometries in total. The effects of Rayleigh number (Ra), aspect ratio in addition to the ellipses orientations are investigated. The dynamic and thermal fields as well as the geometry average Nusselt number calculation (Nuavg=(Nuavo+Nuavi)/2) are analyzed. Nuavg values are ranked at the end in a descending order to show which geometry offers the largest heat exchange rate and vice versa, that is something very useful in practice. It should be noted that a good choice of the geometry shape may lead to have a more homogeneous thermal field, a result which goes against the stratifying effect of natural convection that has sometimes to be avoided.

Solar Chimney Power Plant (SCPP) is a large scale setup designed for generating green power from the thermal solar energy. In this work, a theoretical SCPP model was developed to study the impact of the main design parameters on the SCPP performance. Based on the Manzanares prototype, the proposed model was verified and validated with the experimental data. The thermodynamic characteristics of the SCPP were analyzed by varying the chimney height, the chimney radius and the collector radius. Results show that the chimney height presents an important effect of the air flow behavior. Otherwise, the proposed model has a good agreement to predict the SCPP performance.

Packed columns are considered useful to a great extent in the distillation of natural gas, and liquid volume fraction is a critical parameter for their design. This study aimed to develop a geometrical model of a packed column with one cone spray to simulate the injection. Here, the commercial software FLUENT 6.3 was employed. CFD simulations using the mixture model coupled with several turbulence models were used to analyze the porosity effect on the fluid profiles. The results show that the decrease of the packed porosity resulted in a greater dispersion of the liquid, indicating the anisotropic behavior in the bed. Furthermore, the effect of different turbulence models was analyzed in order to study the atomizing of the liquid phase accurately. The numerical results were obtained to provide further insight into the mechanism of the distillation with volatile components.

In this study, the influence of the shape on the characteristics of a Savonius wind rotor was studied in numerical simulations and experimental measurements. Particularly, we compared the features of the Savonius rotor with a new design rotor consisting of a four-stage configuration. We used “Solid Works Flow Simulation” to display the local characteristics in various transverse and longitudinal planes. The Navier-Stokes equations and the standard k-ε turbulence model were solved in the numerical model. A finite volume discretization method was applied to solve these equations. The experimental measurements were conducted in an open wind tunnel to validate the numerical model.