مجله مهندسی مکانیک
سال پنجاه و دوم شماره 2 (پیاپی 99، تابستان 1401)

In this paper, mixed convection of water-Fe3O4 magnetic nanofluid in a channel containing open cavity is studied. Buongiorno’s non-homogenous model, assuming the effect of the Brownian and thermophoresis of nanoparticles is applied for modeling of nanoparticle migration in base fluid. The Boussinesq approximation is used for free convection modeling. The governing equations are solved using finite volume method and SIMPLE algorithm, numerically. First, a comparison is made between the results of the single-phase method and the present Buongiorno’s model. Furthermore, the effect of changes in various parameters such as Reynolds number (10, 100, 300 and 600), volume fraction of nanoparticles (0.02, 0.04 and 0.06) and Richardson number (0.01, 1 and 10) on heat and nanofluid flow, have been studied in detail. The results showed that with the addition of nanoparticles, the highest increase in heat transfer occurred in the low Reynolds numbers (10.62%). Due to the dominance of thermophoresis effect, nanoparticle volume fraction is low near the hot wall. In Reynolds 10, the thermophoresis has a greater impact on the local volume fraction of nanoparticles than in high Reynolds.

In this research, combined cycle of heat, cold and power production has been simulated and function of the combined cycle has been evaluated in terms of energy and exergy. Moreover, the effect of different parameters including the generator temperature, Pinch point temperature difference and superheated temperature difference on the efficiency of energy, exergy, output work, irreversilbilities and the coefficient of performance of ejector refrigeration cycle has been studied. The combined system proposed in this study includes organic Rankine cycles including pump, steam generator, compressor, turbine, heat exchanger, separator, mixer and ejector refrigeration cycle, which in order to generate power and meet the thermal and refrigeration needs, including heating, Cooling as well as spa is designed for consumption. The results imply that by increasing the input heat to the generator, thermal efficiency of the cycle mainly increases. Also, under the same experimental conditions, with an increase in the temperature of the condenser and the evaporator, thermal efficiency of the whole cycle, studied in this research, has an increasing trend. Highest exergy dissipation is in the heater and the generator. The results show that the generator and the turbine are the most effective equipment in the function of the whole system.

Constructing peak-shaving liquefaction units with 600 times reduction in volume of natural gas, is the most desirable way to store surplus natural gas in the warm seasons and using it in cold seasons of the year. In this research, along with selecting Shahid Rajaee power plant in Qazvin as case study, the natural gas liquefaction cycle with mixed refrigerant with the purpose of supplying the fuel of total unit of this power plant for 60 days was established; and subjected to technical analysis. Then the amount of initial investment and current costs of the natural gas liquefaction unit is calculated. The economic evaluation of the project based on the net present value method and 12 percent discount rate assumption indicates the payback period is 4.3 years. Sensitivity analysis about variation in discount rate and initial investment cost is another consideration in this study. The results show that even with an increase in the discount rate up to 40% or 50% increase in the initial investment cost, the construction of liquefaction unit is economically justified, but by considering that the life cycle of project is 20 years, such a payback period is not much desirable.

In this assay, we investigate the problem of Autonomous Underwater Vehicle (AUV) robust stabilisation including time-varying delay, time-variable uncertainty in modeling, and input amplitude constraint of actuators. Due to system singularity, the main aim is not only stabilisation but also include regularity, and impulse free response for the closed loop system. Encountering methods to model uncertainty, saturation constraint and time-delay are norm bounded method, polytopic method, and delay-dependent criteria respectively. Here a new theorem is introduced and then is proved for the close loop stabilisation through Bilinear Matrix Inequality (BMI). We compare the superiority of this technique by some significant literature via simulation examples from conservativism aspect. Method scope includes both retarded and neutral time-delay systems with multiple delays in states. In continue, for the first time against of conventional state space model methods, we obtain a new descriptor model of an AUV and investigate its robust stability in different conditions based on presented theorem.

TRIP and Q-P are the main methods to produce advanced high-strength steels (AHSS). These heat treatment methods are based on the penetration of carbon from martensite to retained austenite (γR) and therefore stabilization of γR. In the present study, a high strength steel containing Ti micro-alloy element heat treated by Q-P, TRIP and direct quenching (Q-T) followed by comparison of their microstructure and mechanical properties. The effect of these treatments on the microstructure and mechanical properties of the steel was studied and compared by by scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-hardness and metallography. The results showed that the sample performed by Q-P treatment has a good combination of ductility and strength compared to the sample treated by TRIP. The strength and ductility of the Q-P sample were reported to be 1070 MPa and 24%, respectively. The strength and ductility of the sample obtained from TRIP were reported 1160 MPa and 19%, respectively.

The issue of Simultaneous localization and mapping (SLAM) in dynamic environments is an important object in the navigation of autonomous robots, which has not yet been investigated much. In this paper, by presenting a new method, we track dynamic objects in the environment simultaneously with living static object. For this purpose, the EKFSLAM algorithm has been developed for dynamic environments in the way that simultaneous mapping and mapping of dynamic objects in the environment are solved in the form of a problem, which was previously done individually. Also, considering that the efficiency and performance of the developed Kalman filter algorithm depend heavily on the correct knowledge of the covariance matrix of observations, an adaptive Neuro-Fuzzy inference system (ANFIS) is used to adjust the measurement noise covariance matrices to ensure that the accuracy and consistency of the algorithm Than other older methods (SLAM and DATMO, FastSLAM, EKF) is guaranteed. The results of the experiments indicate that the proposed algorithm performs precise tracking

One solution to increase the heat transfer in a channel of solar air heaters is adding baffles along the air path. In this study, investigation on the characteristics of heat transfer and fluid flow in a rectangular channel with V-shaped baffles located at the top and bottom walls of the heater is studied. The parameters such as baffle arrangement, baffle pitch and baffle height at different Reynolds numbers are examined. Nusselt number, friction factor and thermal performance coefficient have been investigated as output parameters. The governing equations include continuity, momentum and energy. The standard k-ԑ model is used to simulate the turbulence model in the channel. The results indicate that by increasing the number of baffle rows, the airflow velocity increases, flow becomes more turbulent and consequently the heat transfer increases. In the study of different baffle pitches, it was found that the channel with baffles with a step of 50 mm has the highest thermal performance coefficient. Also, by increasing the baffle height at a constant heat transfer surface, due to the increase in the velocity of the flow passing through the baffles, the coefficient of performance increases by about 28%.

Methanol is unique as an alternative fuel due to its low pollution and transportation costs, which can be decomposed into synthetic gas by operating catalysts at 250-300 °C. The use of this fuel after synthesis in solid oxide fuel cell, which has been considered by researchers in recent years, can have unique properties. In the present work, in the form of a triple system of power generation, cooling, and heating using solar energy, methanol is first synthesized and converted into gases used in solid oxide fuel cell. The fuel cell system, which is actually combined with a gas turbine system to increase power generation, in addition to generating power, provides the heat needed to generate cooling in an absorption chiller. The results of energy and exergy analysis of the proposed system showed that by controlling the methanol flow rate and temperature, the conversion efficiency reaches over 60%. According to the results of exergy analysis, the irreversible losses of light to heat and heat losses in the solar decomposition reaction of methanol make up about 13% of the total input exergy.

Every year, more oil reservoirs experience pressure drop and production rate decreases. The water flooding process is one of these conventional methods to increase oil production. The velocity of the injected fluid into the porous medium under different physical conditions can extract different amounts of oil from the pores. Due to the spatial geometry and composition of the pores, the velocity of the fluid entering each pore has a wide range. In this study, the effect of fluid velocity in three pores with hydrophilic, hydrophobic and neutral wettability surfaces has been investigated. This was done using numerical simulation with ANSYS-Fluent software at the scale of a 1 mm pore containing medium viscosity oil. The results of this study show that for a pore with single output in the state of hydrophilic cavity and neutral wettability, all oil is removed from the pore at all speeds. But for a pore with two outlets, only if the surface of the hole is hydrophilic, all the oil is removed, and for the pore with neutral wettability, 78% of the oil volume is removed. For the pore with hydrophobic surface, less oil was removed from the pore by increasing the velocity of the inlet fluid and the recovery coefficient was achieved between 63.7% and 98.5%.

In recent years, metamaterials have attracted numerous research attentions due to their applications in low-frequency vibration suppression and noise reduction. In this paper, the effect of indirect interactions on the wave propagation in one-dimensional diatomic metamaterials is investigated. The governing equations of a cell are obtained and using Bloch’s theorem, wave dispersion relations of these materials are obtained and then dispersion curves are plotted. The band gaps of the infinite lattice model are calculated. Furthermore, the influences of various parameters including various stiffness ratios are examined. The numerical results show that the indirect interactions affect the shape of the dispersion curves, while the range of the band-gap slightly changes. In addition, the results reveal the appearance of extra band gap in the proposed metamaterial. Parametric study shows that the extra band gap can be tuned by controlling the stiffness of elastic foundation. These results pave the path to a new generation of metamaterials.

Today, due to the need for data centers, the issue of energy supply required by these centers is very important. Much of the energy consumed in data centers is related to the need for continuous cooling. Therefore, it is necessary to study air distribution, as one of the most important factors in energy saving, greenhouse gas production and increasing cooling. In this research, the data center has been simulated using Design Builder software (DB), and once the air has been distributed from the floor and once from the ceiling. This study was conducted in Mashhad over a period of one year and the results such as energy consumption, server room temperature, initial costs for each system and carbon dioxide emissions, which is one of the most destructive greenhouse gases, were compared. The simulation results showed that under exactly the same conditions with proper distribution of air in data centers can reduce room air temperature to increase room cooling and equipment, energy consumption, energy costs as well as greenhouse gas emissions and production costs. By using the floor air distribution plan, there is an average temperature reduction of 4.5 celsius degrees, 91.5 kWh of energy reduction, 55.5 kg of carbon dioxide emissions, and as a result, there is a $ 90.78 cost reduction compared to the roof air distribution plan per year.

One of the efficient air conditioning systems is ground source heat pumps. The main problem of this type of pumps is the high cost of their installation. By choosing the suitable arrangement of ground heat exchangers, the number of piles and cost can be reduced by increasing the rate of heat transfer to the surrounding. In this research, the thermal performance of the ground heat exchanger with triple helix arrangement is investigated. To this aim, a three-dimensional transient CFD model of the ground heat exchanger and the surrounding soil is developed. In order to evaluate the performance, the results of the triple helix arrangement with the single helix arrangement were compared. In addition, the effect of two involving parameters, including helix pitch and diameter on the performance of the system is examined. The results show, by using the triple helix arrangement, the heat exchange rate is increased about 28% more compared to the single helical arrangement. It was found that the helix pitch has the greatest impact on the system performance and by reducing it, the system performance is improved.

This article presents the results of a numerical study on natural convection heat transfer in a square enclosure filled with a non-Newtonian power-law fluid. Two square obstacles with a constant temperature are placed inside the enclosure. The horizontal walls of the enclosure are thermally insulated, and the vertical walls are at a constant temperature . The flow inside the enclosure is assumed to be two-dimensional, laminar, steady-state, and incompressible. The governing equations for the power-law fluid flow are solved numerically with a finite volume approach using a computer program in FORTRAN using the SIMPLE algorithm. To ensure the accuracy of the simulation, the computer code results are compared with the results of other researchers. The influence of pertinent parameters such as the Rayleigh number , the power-law index , the size of obstacles , the distance between obstacles and the obstacles distance from bottom wall of enclosure on the flow and temperature fields and the heat transfer rate of the enclosure is studied. For different power-law indexes, the results show that the average Nusselt number increases as the size of obstacles increases, and that the average Nusselt number decreases as the distance between obstacles decreases. When the obstacles are placed on the vertical walls, as the distance between the obstacles increases, the heat transfer rate decreases for n=1 and n=0.8 and increases for n=1.4. For power-law indexes below unity, a significant increase in the average Nusselt number is observed as the Rayleigh number increases.

In this study, a new cycle of cogeneration power, heating and cooling integrated with fresh water production system by multi-effect desalination method and solar system has been evaluated. Energy and exergy analyzes have been used to evaluate system performance. In order to generate power, the gas cycle has been used as the main stimulus and the organic Rankin cycle has been used as the downstream cycle. The results of this study show that due to the addition of the solar system in the vicinity of the organic Rankin cycle, the increase of the organic Rankin cycle efficiency improves from 38.778% to 44.592% to 5.813%. In addition, at constant cooling rates, the cooling performance increased by 1.275 percent from 1,596 to 1,617. Also, due to the high production capacity of the gas turbine cycle compared to the production capacity of the Rankin cycle, the addition of the solar system to the base cycle (without the solar system) increases the thermal efficiency and exergy by 0.638 and 0.085%, respectively. Also, distillate flow rate increases 726.8 Ton/h by using reverse osmosis system.

Forming limit diagram (FLD) is a criterion to determine the formability of metal sheet during various forming processes. The Marciniak-Kuczynski instability theory is one of the most widely used methods to determine the FLD. The plastic behavior of the materials has great influences on the accuracy of the predicted diagrams by the Marciniak-Kuczynski model. In this study, the novel constitutive models which are a combination of the Swift and Voce models are proposed to predict the forming limit diagrams. The constant parameters of each hardening models are calculated by using the stress-strain diagram obtained from uniaxial tension tests. Finally, the forming limit diagrams of the aluminum sheet by employing the Yld2000-2d yield function and different hardening models were plotted. The comparison between the calculated diagrams and the experimental results shows that although the Kim-Tuan, Ghosh and Swift models compute the FLD to an acceptable level, the forming limit diagram predicted by modified Kim-Tuan is in better agreement with experimental results. Therefore, the modified Kim-Tuan relationship and its coefficients are proposed as an ideal hardening model to determine the forming limit diagram of the AA5754-O.

In this paper, dynamic modeling of a soft micro robot equipped with shape memory alloy (SMA) actuator is presented. Due to the structure of the soft micro robots, these robots have various applications. Since the shape memory alloys have features such that biocompatibility, high power, small dimensions and working silently, they are suitable for the micro robots. Because there is not a dynamic model for the soft robots equipped with shape memory alloy, here a dynamic model of a micro robot equipped with SMA is introduced. To this end, the motion equations of the robot and actuator’s structural equations are extracted. In dynamic modeling of the soft robot, Cosserat theory is used and Liang and Roger’s model is used for the SMA modeling. Also, modeling of free and forced convection heat transfer in the heating and cooling processes has been done. Then, the dynamic behavior of the micro robot is simulated and its electrical current effect and fluid velocity on the robot's dynamic behavior have been investigated. The simulation results show that the proposed model simulates correctly the behavior of the micro robot.

In the present study, heat transfer enhancement of a non-Newtonian nanofluid by different arrangements of double fins in a corrugated channel was numerically investigated. Finite volume method is used to solve governing equations of flow and energy with assumptions of 2D, steady-state, and single phase. The fluid flow is in the hydraulically laminar regime and the channel is under a constant heat flux. A set of case studies are conducted for a corrugated channel model to analyze the influence of the main contributing factors; Reynolds number, nanofluid volume fraction, the different fin configurations, on the flow field and the heat transfer characteristics as well. . Results indicate that using non-Newtonian fluid of water+0.5%CMC instead of water fluid leads to enhance heat transfer. The numerical results showed that implementing configuration D in a corrugated channel leads to heat transfer rate compared to other configurations. Besides, for configuration D, raising the Reynolds number from 200 to 1000 and the nanofluid volume fraction from 0.5% to 1.5% cause the mean Nusselt number and performance evaluation index to increase about 9.85% and 9.09%, respectively.

Method of power and hydrogen gas production by solar energy and water electrolysis has received attention in recent years, because hydrogen and oxygen gases are separated from water without any pollution, the mentioned method has net-zero carbon emissions, known as green hydrogen. In this study, solar cells are used to supply power for the proton exchange membrane (PEM) electrolysis and the liquefaction sections. Bandar Abbas city is selected for the proposed process. The novelties of this study are based on two points, first proposing an integrated process of solar power generation and separation and liquefaction of hydrogen gas without pollution and with higher efficiency compared to other similar cycles. The capacity of solar arrays is 6,000 kW, while the production capacity of the electrolysis section is 438 kg/h of oxygen gas and 55 kg/h of hydrogen gas. The specific energy consumption (SEC) of the liquefaction cycle is 5.07 kWh/kg. The highest rate of exergy destruction goes to the electrolysis section, followed by heat exchangers as the second rank.

This study is aims to perform three-dimensional simulation gas turbine internal cooling system for stationary and rotating mode at the middle region of four-pass smooth channels to assess fluid flow and turbulent heat transfer. The geometry of bend has been changed to U-shape turn and the guide vane in the bending region is Installed in order to enhance higher overall performance the cooling channel. The results of the governing equations are obtained using the Reynolds stress turbulence model. cooling channels are simulated in three different Reynolds numbers ranges from 20,000 to 60,000 and the rotation number of 0/13. The effect of the guide vanes on the U-shaped bend region, in addition to reducing the separation bubble area and circulation fluid in the upstream bend flow, it causes more uniform flow structure in the bend region and subsequent passage. So that the correction of bend and the use of flow guide vane to the base geometry in the case stationary of pressure drop and the coefficient of thermal performance decreases by about 13.4% and increases by 22.5%, respectively. The effect of the guide van on the amount of heat transfer in the rotating state is not noticeable, but due to the reduction of pressure drop, it increases the coefficient of thermal performance up to 9.4%.

Nowadays, the use of thermoelectric as one of the methods of recovering waste heat energy has received much attention. In this research, while presenting a new thermal energy recovery system in the molten slag of steel Industry, thermodynamic analysis of the proposed system from the perspective of energy and exergy is also presented. Then the effect of various parameters including Seebeck coefficient on the performance of the proposed system is investigated. The results of modeling in both power cycle and thermoelectric cycles have been validated by previous research. The results of thermodynamic analysis show that the largest contribution to the exergy destruction of the proposed system is related to the heat recovery system. According to the results, the production capacity of the heat recovery system from the total production capacity is about 49% and the efficiency of the first law of thermodynamics for the proposed system is 24.7% and the efficiency of the second law of thermodynamics is 32.88%. Economic analysis indicates that with thermoelectric generator cost of 1 $/W the payback rate of investment is less than 2 years.

Thin-walled structures have always been considered by designers as components with excellent energy absorption and high strength to weight. These structures are made in different shapes and geometries. Conical tubes are one of the types of thin-walled structures that deform the plastic and absorb energy under loading in different ways. The energy absorbed through plastic deformation depends on various factors such as the geometry of the tube, the volume, the angle of applied load and the materials. In this paper, a comprehensive study has been performed on thin-walled conical tubes as energy absorbers using numerical simulations. For this purpose, the effect of various parameters including the presence of the cap at the end of the tube, annular and longitudinal grooves, the creation of holes on the tube wall and loading angle has been investigated on the crushing mode and energy absorption. The results show that although the presence of annular, longitudinal grooves and creating holes on the tube wall leads to reduced energy absorption, but it causes a stable collapse and reduces the maximum crushing load and prevents the suddenly applied load to occupants and the main part of structures Also, the results showed that the number of holes did not have a significant effect on the collapse and the behavior of the load-displacement curve; while the shape of the hole geometry affects the collapse mode and the mean crushing load.

An existing solution for using tactical solid fuel rockets for space purposes is to add a blast tube to the nozzle. Equipping the nozzle with a blast tube, in addition to creating space to add the required subsystems, also makes it easier to stabilize and control the system. To get the best performance from a nozzle, various changes must be made to the nozzle structure.In the present study, the existing nozzle is first analyzed from a geometric and aerodynamic point of view using numerical solution in order to achieve performance and efficiency. Then in order to add the blast tube, two new geometries of the mentioned nozzle are designed and according to the prevailing conditions, the changes in velocity, pressure and temperature of the flow through the nozzle have been studied. The results show that the addition of blast tube causes a decrease in total pressure of less than 2%, which is acceptable considering the benefits obtained.

Mixing different or identical fluids together plays an important role in many microstructures, so it is important to study the quality of mixing in microchannels. Numerical study of oxygen and nitrogen mixing in passive three-dimensional micromixer was performed by finite element method and the effect of Reynolds number, type, number and width of mixing units and obstruction in the flow path on mixing quality and pressure drop was investigated. While most previous studies have been on the mixing of liquids, in this study the mixing of gases in simple micromixers, as well as micromixers with mixing units, has been investigated. For this purpose, two new types of micromixers named A and B with new and multiple mixing units have been introduced. Mass performance evaluation of the new model's A and B with helical mixing units, compared to the base model without the mixing unit shows that the new models have a higher performance than the base model as micromixer A with five mixing units, in Reynolds 110, compared to the base model. Improves mixing quality 2 times and 1.25 times better than Model B. Also, the effect of the depth of cubic barriers in micromixer B with five mixing units indicates the improvement of mixing quality compared to the unobstructed model in higher Reynolds. As in Reynolds 110 model B with five mixing units, the mixing quality is about 95%.

NiTi shape memory alloy stents can be used for peripheral artery due to the reduction of problems such as improper dynamic behavior, low torsional capability and insufficient radial strength. In this paper, the finite element method used to study the metallurgical, mechanical and clinical behavior of NiTi shape memory alloy stents for application in peripheral artery by applying radial strain according to the standard .Material properties model of NiTi shape memory alloy was based on Helmholtz free thermodynamic energy (Auricchio model) and phase change equation of martensite transformation based on Liang and Rogers model. With changing the Af temperature from 293 to 303 K, NiTi shape memory alloy stents have better mechanical and clinical performance due to the applied force to the artery, optimal radial strength, and complete hysteresis loop depending on superelastic behavior, less stress and more strain. This numerical study can provide a good way to study the mechanical behavior of stents used in the peripheral artery with respect to the effects of metallurgical and mechanical properties.

The main purpose of this study is the economic analysis of the system of combined cooling, heating and power- organic rankine cycle CCHP-ORC so that the supply of building energy needs for cold climates in one year with a new strategy that the year is divided into 24 parts of fifteen days. The prime mover is a gas turbine system that provides part of the heat and electricity needed by the building. Excess heat from the prime mover is recovered and given to organic rankine cycle to generate electricity. The study system was optimized by genetic algorithm with a total of 29 design parameters, including gas turbine capacity, absorption and electric chiller capacity, electric cooling ratio, auxiliary boiler capacity and 24 partial loads for gas turbines throughout the year and minimum total annual cost (TAC) Selected as the objective function. The results show that the annual cost and emission costs in the CCHP-ORC system are 2.2% and 14.7% lower than the CCHP system, respectively. The exergy efficiency of CCHP-ORC system is 40.93% which is 5.9% higher than CCHP system.

This paper is focused on selecting of nominal local models (NLMs) to design the multi-model based controller for nonlinear systems. Also gap metric is used as a powerful tool to measure the distance between local linear models. In order to decompose the nonlinear system into smaller number of NLMs, selecting of NLMs and designing the local controllers are integrated. The designed local controllers for the primary sub-regions may be able to stabilize other local models of the next sub-regions while the traditional successive search methods disregard the efficacy of the former NLMs and corresponding local controllers. Therefore, these methods suffer from the redundancy problem and complexity of the multi-model controller. It is shown that improving of NLMs selection procedure by considering the efficacy of local controllers in the entire operating range can intensely reduce the number of NLMs and local controllers. Therefore, improving the decomposition procedure, screening the efficacy of the local controllers in the entire operating range, and reducing the number of local controllers are the main advantages of the proposed decomposition procedure in this paper. To evaluate the effectiveness of the proposed method, a highly nonlinear process, pH neutralization, is simulated. The results prove the effectiveness of the proposed method in set-point tracking and disturbance rejection while the number of NLMs is half in comparison to other traditional successive search methods.

In this research, the dielectric barrier discharge plasma driven channel flow has been proposed for use as a thruster in the propulsion’s applictions and has been experimentally studied. Measurments of the thrust and consumed power with different values of barrier thicknesses and electrodes’ lenghths have been performed. The data of the mentioned parameters have been taken in order to quantify the effects of operating voltage on the effectiveness parameter of thruster, showing a peak-shaped profile for the effectiveness with maximum value of 0.19 mN/W at the profile summit. Also, a power law analysis has been used to derive relationships for the effectiveness, thrust and consumed power in terms of the applied voltage. It has been found that the thruster’s power is proportional to the voltage with exponent of 4, and the thrust is function of voltage with exponent of 2.2 and 5.8 for the glow and filamentary regimes, respectively. Finally, it has been shown that the effectiveness can be correlated to applied voltage with exponent of 1/8 and -1.8 for the glow and filamentary regimes, respectively.

In this study, the effect of sun tracking on the performance of an evacuated tube solar cooker is experimentally investigated. For this purpose, sun tracking is manually performed in time intervals of 5 min. Moreover, in another experiment, the solar cooker is placed towards the south with a tilt angle of 30º. In this research, the evacuated tube solar cooker is utilized to boil water. In addition, the comparison of the performance of the solar cooker in the fixed and movable situations is conducted from the energy and exergy viewpoints. The results indicate that the time required to boil 800 gr of water in the experiment in which the solar cooker is in the fixed situation is 2 h and 25 min. However, the sun tracking by the solar cooker reduces the mentioned time by about 1 h and 5 min (44.83%). Using sun tracking, the energy and exergy efficiencies of the solar cooker also increase about 4.92% and 0.57% in order.

At this work, 3D combustion of coal pulverised particles in the MILD state has been simulated by OpenFOAM open ‎source code. The target of this work is the study of partially stirred reactor combustion model in simulating of coal particles MILD combustion. This model can consider the finite rate chemistry. According to studies, there have been no reports on this subject so far.This numerical study is done with criterion of IFRF experimental results and the conservative equations are solved simultaneously. Interaction between phases by Euler-Lagrange approach, interaction between turbulence and combustion in continous phase by Partially stirred reactor, production/consumption of species by 4 step Jones and Lindstedt global mechanism has been modeled. Results show that forenamed models specially partially stirred reactor can estimate the velocity, temperature, and species in MILD combustion of coal particles truely. Accuracy of temperature is better than species. Global kinetic could be one reason of this case.

Aerodynamic efficiency should be desirable to achieve long endurance. It is possible to increase its aerodynamic efficiency by optimizing the airfoil. After researching the optimization methods, a gradient algorithm has been used to perform the optimization. In this paper, GOE 493 airfoil is optimized for use in medium altitude UAVs with long endurance. The flow around the airfoil is made of structure mesh and ICMCFD software have been used. For computational fluid dynamics of turbulent flow, after examining different turbulence models and comparing their results with experimental results, the k-kl-omega model and finite volume method with coupled algorithm have been used. After research, the adjoint algorithm has been used for this optimization. The objective function in this optimization has been aerodynamic efficiency. The results for the optimized airfoil show that the aerodynamic efficiency in the cruise mode is doubled compared to the initial state.KEYWORD: Airfoil, Aerodynamic Efficiency, Optimization, Adjoint Algorithm

In previous studies on the INVELOX system, the effect of turbine blades embedded in the venturi section has not accounted. In addition, the design and modeling of an optimal wind turbine in accordance with the geometry and aerodynamic conditions of the venturi section has not been done. Therefore, in this paper, using the BEM (blade element momentum) theory and considering Prandtl's tip and hub loss factors, and also turbulent wake correction, a semi-analytical code has been developed. First of all, an optimal wind turbine according to geometrical and operational assumed INVELOX system is designed. In the continuation, modeling and performance study of geometric parameters of the designed wind turbine has been done. The validation results show that the developed code agrees accurately with the previous experimental, numerical, and analytical results, and therefore the geometry designed for the blades will be reliable. In addition, the application of Glauert and Burton's corrections has been evaluated in this manuscript. Based on the research findings, it is concluded that under the same conditions, Burton's correction yields more conservative results than Glauert's correction. So that assuming 3 blades and a wind speed of 11 meters per second m/s and taking into account Prandtl's tip and hub loss factor, the maximum power coefficient and blade tip speed corresponding to Burton's correction are 0.335 and 7.178, respectively, and corresponding to Glauert's correction, are 0.385 and 7.825, respectively. The provided substrate can be used to optimize the blade shape and structure of the INVELOX wind turbine system.

Solid particles migration in liquid phase through microchannels is considered to be the most important issue in microfluidic systems. Converging-Diverging microchannels are being used in manufacturing the microfluidics tools such as micro-switches, micro-sensors and micro-filters. In this research, 3-D numerical simulation based on Eulerian-Eulerian approach was performed on solid-liquid two-phase flow in a converging-diverging microchannel with 200 μm height. The size of particles used in this research is 20μm with density of 1.05 gr/cm3. The results showed that the most particle accumulations occured in the regions close to the walls before and after the nozzle, but in the converging part of the nozzle, the amount of particles even near the walls decreased due to the increase in flow velocity. Furthermore, increasing the Reynolds number leaded to increase in the amount of particles accumulated at the throat and reached its maximum value. Compared with similar studies, this study investigates the effect of converging-diverging geometry of the channel on particle sedimentation. The results show that using converging-diverging channel provides the possibility to prevent the destructive phenomenon of channel blockage.

Thermoregulatory models based on thermoreceptors have attracted the attention of researchers in recent years due to their conformity with the basis of human thermal perception. For this reason, various models have been presented such as STB, ITB, MSTB and JOSTB. In the present study and in continuation of previous studies, an individual multi-segment thermoregulatory bioheat (IMTB) model has been introduced which can evaluate the temperature of various segments of the body by considering the effects of individual parameters such as height, weight, age and gender. In this study, the body is subdivided into 17 segments, 3 layers and the blood circulatory system consists of arteries, veins and superficial veins. Also, the effects of individual parameters on physiological parameters, thermoregulatory mechanisms and heat transfer of the body have been investigated. Finally, the performance of the new model in predicting local and mean skin temperature was validated against different experimental data. The results indicate that by considering the individual parameters, the new model can precisely predict the local skin temperature with mean absolute error of 0.4℃.

In this experimental research, the performance of the close single turn pulsating heat pipe (CPHP) with distilled water as base fluid and distilled water including microparticles (micro-coppers) have been investigated. To evaluate the effect of different parameters on the CPHP performance, several characters like input powers, filling ratio and concentrations of micro-coppers were studied. Findings from experiments indicate that the multiphase flow regime inside the pipe was slug-plug in low powers but it approached to an annular flow in higher value of heat inputs. Furthermore, it is required to mention that the thermal resistance of the device with micro-coppers has decreased with enhancing in the concentration of micro-coppers and input powers and it has the minimum value (0.61degC/W) at filling ratio of 60%, at input power of 60W. Finally, according to any errors of each parameters and by using Holman methods, the maximum uncertainty of experiments was calculated about 8%.

Uncertainty about the musculoskeletal modeling results is one of the main issues that are less investigated by users. Although the results of these models are accurate enough for gait activities, high errors were reported for activities with deep knee bending like squatting tasks. Recently, by updating the wrapping surfaces in a powerful musculoskeletal model (Rajagopal), an updated version for deep squatting (Catelli) has been released. But high average errors are reported in simulations using this model for CAMS subjects. Opensim software and Opensim-Matlab API were used. In this study, the effect of uncertainty in the muscle pathways of a scaled version of the Catelli model on the knee contact force was studied using the probabilistic Monte Carlo approach. 43.7±19.02% confidence bounds of KCF error during a squat cycle and 159±77% in deep squat were computed. Therefore, more corrections in muscle pathways parameters in the model specified for simulating squat motion could improve the results.

In this study, thermohydrodynamic analysis of three lobe noncircular journal bearings with power law fluid model and the evaluation of the design and lubrication parameters such as power law index, rotor velocity and preload effects on the pressure and temperature of the oil, load carrying capacity, attitude angle and heat transfer in the bearing shell is provided. For this purpose, the governing Reynolds and energy equations of incompressible lubrication are modified based on power law theory and analyzed simultaneously with 3D heat transfer equation in the bearing shell. According to the limited length of investigated bearings and lack of exact answer, the equations are solved numerically using the generalized differential quadrature (GDQ) method. Results show that increasing the power law index and the rotor speed or decreasing the bearings noncircularity, intensify the temperature and reduce the oil viscosity and increase the difference between the obtained value of thermal and isothermal pressure and load. In addition, increasing the lubricant temperature by upgrading power law properties enhances the temperature of the inner bush surface and the rate of heat transfer to environment.

In this paper, the effects of size on spherical cell membrane under hydrostatic pressure and heat field are investigated using strain gradient theory. Two most important parameters related to the cellular niche are mechanical forces and thermal fields. Thermal and mechanical fields affecting the cell are used in the food industry to inactivate microorganisms. The governing equations are obtained using the minimum potential energy principle and finally the governing equations are solved numerically. The effect of size parameters, heat field and hydrostatic pressure were investigated. The results indicate that the effects of small-sale cannot be ignored and predict the hardening properties compared to classical theory. In addition, increasing the heat field and hydrostatic pressure increases the displacement. The results of this research can be used for food industry and tissue engineering.In addition, increasing the heat field and hydrostatic pressure increases the displacement. The results of this research can be used for food industry and tissue engineering.

Intelligent fault detection diagnosis methods are one of the common topics in recently investigations. In this paper, a new hybrid technique is presented based on discrete wavelet transform (DWT) and multi – class support vector machine (Multi-SVM). The considered vibrational signals are collected in three conditions: normal, chipped tooth and worn teeth. These signals are decomposed using DWT methods with different wavelet base functions and the most appropriate level of decomposition are selected by the cross - correlation concept. The feature vector for each sample is extracted using different time domain statistical functions. «One – against - one» support vector machine (SVM-OAO) is utilized for detecting the gearbox conditions. The condition recognition of a gearbox is depended on the extracted features type and setting the SVM parameters. Therefore, in this study, particle swarm optimization (PSO) is used for identifying the most sensitive features to the defect and its type and determining the optimal parameters of SVM method. The obtained results show that the identification accuracy of the gearbox conditions is significantly increased with improving the feature matrix and the SVM classifier method.

In this paper, the effect of wake phenomenon on the performance of 2 and 3 bladed tidal current turbines have been investigated. Computational fluid dynamics analysis using ANSYS-FLUENT has been conducted. Initially, turbines were evaluated at the different values of the tip speed ratio and the maximum power coefficient was estimated. Then, the wake distance was evaluated for this maximum power coefficient. Results showed that at the tip speed ratio of 5, the maximum power coefficient for both turbines was achievable which were 0.35 and 0.28 for a 3 and 2-bladed turbines, respectively. Also, the wake phenomenon in 2-bladed turbine terminated earlier than 3-balded, so that; at a distance after the turbine which was equal to the thirteen times more than the turbine diameter, the flow velocity returned to 87% and 81% of initial flow velocity for 2 and 3-bladed turbines, sequentially. Considering the results, 3-bladed turbines are justified to use when there is no restriction for the area of the tidal farm while the maximum power extraction is the main objective. Conversely, 2-bladed turbines seem to be more appropriate where the tidal farm area is the particular of importance.