review on the cooling of energy conversion and storage systems using thermoelectric modules

Exploitation of sustainable energy sources requires the use of unique conversion and storage systems,such as solar panels,batteries,fuel cells,and electronic equipment.Thermal load management of these energy conversion and storage systems is one of their challenges and concerns.In this article,the thermal management of these systems using thermoelectric modules is reviewed.The results show that by choosing the right option to remove heat from the hot side of the thermoelectric modules,it will be a suitable local cooling,and the thermoelectric modules increase the power and lifespan of the system by reducing the spot temperature.Thermoelectric modules were effective in reducing panel temperature.They increase the time to reach a temperature above 50℃ in batteries by 3 to 4 times.Also,in their integration with fuel cells,they increase the power density of the fuel cell.

Analysis of Turbulent Flow on Tidal Stream Turbine by RANS and BEM

Nowadays,concerns arise because of the depletion of fossil fuel resources that forced scientists to develop new energy extraction methods.One of these renewable resources is tidal energy,where Iran has this potential significantly.There are many ways to obtain the kinetic energy of the fluid flow caused by the moon’s gravitational effect on seas.Using horizontal axis tidal turbines is one of the ways to achieve the kinetic energy of the fluid.Since this type of turbine has similar technology to horizontal axis wind turbines,they may be an appropriate choice for constructing a tidal power plant in Iran.This paper presents the numerical simulation and momentum method of a three-bladed horizontal axis tidal turbine.To validate the thrust and power coefficients for a fixed pitch angle at the blade tip speed ratio of 4 to 10 are compared with experimental results.In this modelling,the rotating geometry simulation has been used.Results show that using a numerical method and blade element momentum,we can predict the horizontal axis tidal turbine’s thrust with an error of less than 10%.The numerical method has better accuracy in higher speed ratios,and it is appropriate to predict the behaviour of fluid in collision with turbines and its wake effects.

Long-term effects of main-body's obliquity on satellite formation perturbed by third-body gravity in elliptical and inclined orbit

A new non-simplified model of formation flying is derived in the presence of an oblate main- body and third-body perturbation. In the proposed model, considering the perturbation of the third- body in an inclined orbit, the effect of obliquity （axial tilt） of the main-body is becoming important and has been propounded in the absolute motion of a reference satellite and the relative motion of a follower satellite. From a new point of view, J2 perturbed relative motion equations and considering a disturbing body in an elliptic inclined three dimensional orbit, are derived using Lagrangian mechanics based on accurate introduced perturbed reference satellite motion. To validate the accuracy of the model presented in this study, an auxiliary model was constructed as the Main-body Center based Relative Motion （MCRM） model. Finally, the importance of the main-body＇s obliquity is demonstrated by several examples related to the Earth-Moon system in relative motion and lunar satellite formation keeping. The main-body＇s obliquity has a remarkable effect on formation keeping in the examined in-track and projected circular orbit （PCO） formations.

Modeling CO_(2)Emission in Residential Sector of Three Countries in Southeast of Asia by Applying Intelligent Techniques

Residential sector is one of the energy-consuming districts of countries that causes CO_(2)emission in large extent.In this regard,this sector must be considered in energy policy making related to the reduction of emission of CO_(2)and other greenhouse gases.In the present work,CO_(2)emission related to the residential sector of three countries,including Indonesia,Thailand,and Vietnam in Southeast Asia,are discussed and modeled by employing Group Method of Data Handling(GMDH)and Multilayer Perceptron(MLP)neural networks as powerful intelligent methods.Prior to modeling,data related to the energy consumption of these countries are represented,discussed,and analyzed.Subsequently,to propose a model,electricity,natural gas,coal,and oil products consumptions are applied as inputs,and CO_(2)emission is considered as the model’s output.The obtained R^(2) values for the generated models based on MLP and GMDH are 0.9987 and 0.9985,respectively.Furthermore,values of the Average Absolute Relative Deviation(AARD)of the regressions using the mentioned techniques are around 4.56%and 5.53%,respectively.These values reveal significant exactness of the models proposed in this article;however,making use of MLP with the optimal architecture would lead to higher accuracy.

Performance improvement in stepped solar still modified by sponge layer

In this paper,the experimental investigation on the performance improvement of conventional stepped solar still is conducted.The steps are covered by the porous material to improve the performance of the conventional device and increase the evaporation rate.All the parameters,including the temperature on the glass surface,the water temperature inside the evaporation zone,and the amount of water produced in both conventional and modified stepped solar stills are measured and compared.The efficiency of two devices and their exergy efficiency have been calculated.Finally,the economic analysis of both devices has been done to check the economic feasibility of the modified device.The amount of freshwater generated during one day was 2244.4 and 3076.2 mL/m^(2),respectively for the conventional and modified stepped solar stills.As a result,the amount of water produced in one day by modified stepped solar still is 35.5% more than the conventional one.Also,the costs for the conventional and modified stepped solar stills have been calculated as 0.0359 and 0.029$/(L·m^(-2)),respectively.

Exergy Analysis of Charge and Discharge Processes of Thermal Energy Storage System with Various Phase Change Materials:A Comprehensive Comparison

Thermal energy storage(TES) is of great importance in solving the mismatch between energy production and consumption.In this regard,choosing type of Phase Change Materials(PCMs) which are widely used to control heat in latent thermal energy storage systems,plays a vital role as a means of TES efficiency.However,this field suffers from lack of a comprehensive investigation on the impact of various PCMs in terms of exergy.To address this issue,in this study,in addition to indicating the melting temperature and latent heat of various PCMs,the exergy destruction and exergy efficiency of each material are estimated and compared with each other.Moreover,in the present work the impact of PCMs mass and ambient temperature on the exergy efficiency is evaluated.The results proved that higher latent heat does not necessarily lead to higher exergy efficiency.Furthermore,to obtain a suitable exergy efficiency,the specific heat capacity and melting temperature of the PCMs must also be considered.According to the results,LiF-CaF_(2)(80.5%:19.5%,mass ratio) mixture led to better performance with satisfactory exergy efficiency(98.84%) and notably lower required mass compared to other PCMs.Additionally,the highest and lowest exergy destruction are belonged to GR25 and LiF-CaF_(2)(80.5:19.5) mixture,respectively.

Comprehensive investigation of stress intensity factors in rotating disks containing three-dimensional semi-elliptical cracks

Initiation and propagation of cracks in rotating disks may cause catastrophic failures. Therefore, determination of fracture parameters under different working con- ditions is an essential issue. In this paper, a comprehensive study of stress intensity factors （SIFs） in rotating disks containing three-dimensional （3D） semi-elliptical cracks subjected to different working conditions is carried out. The effects of mechanical prop- erties, rotational velocity, and orientation of cracks on SIFs in rotating disks under cen- trifugal loading are investigated. Also, the effects of using composite patches to reduce SIFs in rotating disks are studied. The effects of patching design variables such as mechanical properties, thickness, and ply angle are investigated separately. The modeling and analytical procedure are verified in comparison with previously reported results in the literature.

Utilization of Machine Learning Methods in Modeling Specific Heat Capacity of Nanofluids

Nanofluids are extensively applied in various heat transfer mediums for improving their heat transfer characteristics and hence their performance.Specific heat capacity of nanofluids,as one of the thermophysical properties,performs principal role in heat transfer of thermal mediums utilizing nanofluids.In this regard,different studies have been carried out to investigate the influential factors on nanofluids specific heat.Moreover,several regression models based on correlations or artificial intelligence have been developed for forecasting this property of nanofluids.In the current review paper,influential parameters on the specific heat capacity of nanofluids are introduced.Afterwards,the proposed models for their forecasting and modeling are proposed.According to the reviewed works,concentration and properties of solid structures in addition to temperature affect specific heat capacity to large extent and must be considered as inputs for the models.Moreover,by using other effective factors,the accuracy and comprehensive of the models can be modified.Finally,some suggestions are offered for the upcoming works in the relevant topics.

A numerical investigation of CO2 dilution on the thermochemical characteristics of a swirl stabilized diffusion flame

The turbulent combustion flow modeling is performed to study the effects of CO_2 addition to the fuel and oxidizer streams on the thermochemical characteristics of a swirl stabilized diffusion flame. A flamelet approach along with three well-known turbulence models is utilized to model the turbulent combustion flow field. The k-ω shear stress transport(SST) model shows the best agreement with the experimental measurements compared with other models. Therefore, the k-ω SST model is used to study the effects of CO_2 dilution on the flame structure and strength, temperature distribution, and CO concentration. To determine the chemical effects of CO_2 dilution, a fictitious species is replaced with the regular CO_2 in both the fuel stream and the oxidizer stream. The results indicate that the flame temperature decreases when CO_2 is added to either the fuel or the oxidizer stream. The flame length reduction is observed at all levels of CO_2 dilution. The H radical concentration indicating the flame strength decreases, following by the thermochemical effects of CO_2 dilution processes. In comparison with the fictitious species dilution, the chemical effects of CO_2 addition enhance the CO mass fraction. The numerical simulations show that when the dilution level is higher, the rate of the flame length reduction is more significant at low swirl numbers.

Feasibility study of symmetric solution of molecular argon flow inside microscale nozzles

The computational cost of numerical methods in microscopic-scales such as molecular dynamics(MD) is a deterrent factor that limits simulations with a large number of particles. Hence, it is desirable to decrease the computational cost and run time of simulations, especially for problems with a symmetrical domain. However, in microscopic-scales, implementation of symmetric boundary conditions is not straightforward. Previously, the present authors have successfully used a symmetry boundary condition to solve molecular flows in constant-area channels. The results obtained with this approach agree well with the benchmark cases. Therefore, it has provided us with a sound ground to further explore feasibility of applying symmetric solutions of micro-fluid flows in other geometries such as variable-area ducts. Molecular flows are solved for the whole domain with and without the symmetric boundary condition. Good agreement has been reached between the results of the symmetric solution and the whole domain solution. To investigate robustness of the proposed method, simulations are conducted for different values of affecting parameters including an external force, a flow density, and a domain length. The results indicate that the symmetric solution is also applicable to variable-area ducts such as micro-nozzles.

Highly stable Ga-doped ZnO/polystyrene nanocomposite film with narrow-band cyan emission

In the present study,a simple method for the preparation of a luminescent flexible gallium doped zinc oxide(GZO)/polystyrene nanocomposite film was developed.The prepared GZO powder was characterized through different optical and structural techniques.The XRD study revealed the existence of a wurtzite structure with no extra oxide peaks.Elemental-mapping,EDX,FTIR and XPS analyses were used to confirm the presence of elements and the several groups present in the structure.Under excitations of UV,the prepared hybrid nanocomposite showed a strong cyan emission with narrow full width at half the maximum value(20 nm)that has not been reported before.X-ray and laser-induced luminescence results of the hy-brid film revealed novel blue-green emission at room temperature.The prepared composite film showed a strong scintillation re-sponse to ionizing radiation.The strong emissions,very weak deep-level emissions,and low FWHM of composite indicate the de-sirable optical properties with low-density structural defects in the GZO composite structure.Therefore,the prepared hybrid film can be considered to be a suitable candidate for the fabrication of optoelectronic devices.

Evaluation of Unsaturated Layer Effect on Seismic Analysis of Unbraced Sheet Pile Wall

This paper is built upon the previous developments on lateral earth pressure by providing a series of analytical expressions that may be used to evaluate vertical profiles of the effective stress and the corresponding suction stress under steady-state flow conditions. Suction stress profile is modeled for one layer sand near the ground above the water level under hydrostatic conditions. By definition, the absolute magnitude of suction stress depends on both the magnitude of the effective stress parameter and matric suction itself. Thus, by developing the Rankine’s relations in seismic state, the composing method of active and passive surfaces in sides of unbraced sheet pile is examinated and the effects of soil parameter on those surfaces are evaluated by a similar process. The relations described the quantitative evaluation of lateral earth pressure on sheet pile and the effects of unsaturated layer on bending moment and embedded depth of sheet pile in soil.

The Effect of Evaporative Formations in Increasing the Salinity of the Water Resources in Mahdasht-Eshtehard Region (Iran)

Considering the underground water resources salinity problem in Mahdasht to Eshtehard region of southern Alborz Province, we attempted to deal with the relationship between the water sources features especially salinity with the geology of the mentioned range in terms of petrology and structural properties. For this purpose after determining the study range, field investigation was performed to identify the geological formations and the distribution thereof as well as the faults locations using existing geological maps. Using a fourteen year period statistics (2009-2014), the static water table, the discharge rate, annual exploitation and the plain’s underground water level elevation (GIS) were analyzed and evaluated. Water samples were taken from 18 wells and chemical analysis determining the quality of water was used. The concentration contour maps of chloride, sulfate, sodium and total soluble solids together with the faults performance analysis showed that the highest salinity concentration relates to northeastern part of the plain. Concentration and qualitative results, the regional water quality can be classified in moderate to disagreeable in terms of potability and saline for agricultural use. The study findings showed that the high evaporative masses’ erosion rate and gypsum and saline sediment transport from the northeast Neogene formations have developed saline field in the plain and immethodical exploitation of water sources has considerably reduced the water quality and increased the salinity.

Probabilistic stability of uncertain composite plates and stochastic irregularity in their buckling mode shapes:A semi-analytical non-intrusive approach

In this study,the mechanical properties of the composite plate were considered Gaussian random fields and their effects on the buckling load and corresponding mode shapes were studied by developing a semi-analytical nonintrusive approach.The random fields were decomposed by the Karhunen−Loève method.The strains were defined based on the assumptions of the first-order and higher-order shear-deformation theories.Stochastic equations of motion were extracted using Euler-Lagrange equations.The probabilistic response space was obtained by employing the nonintrusive polynomial chaos method.Finally,the effect of spatially varying stochastic properties on the critical load of the plate and the irregularity of buckling mode shapes and their sequences were studied for the first time.Our findings showed that different shear deformation plate theories could significantly influence the reliability of thicker plates under compressive loading.It is suggested that a linear relationship exists between the mechanical properties’variation coefficient and critical loads’variation coefficient.Also,in modeling the plate properties as random fields,a significant stochastic irregularity is obtained in buckling mode shapes,which is crucial in practical applications.

Optimization of the mechanical performance and damage failure characteristics of laminated composites based on fiber orientation

In this study,the effect of fiber angle on the tensile load-bearing performance and damage failure characteristics of glass composite laminates was investigated experimentally,analytically,and numerically.The glass fabric in the laminate was perfectly aligned along the load direction(i.e.,at 0°),offset at angles of 30°and 45°,or mixed in different directions(i.e.,0°/30°or 0°/45°).The composite laminates were fabricated using vacuum-assisted resin molding.The influence of fiber orientation angle on the mechanical properties and stiffness degradation of the laminates was studied via cyclic tensile strength tests.Furthermore,simulations have been conducted using finite element analysis and analytical approaches to evaluate the influence of fiber orientation on the mechanical performance of glass laminates.Experimental testing revealed that,although the composite laminates laid along the 0°direction exhibited the highest stiffness and strength,their structural performance deteriorated rapidly.We also determined that increasing the fiber offset angle(i.e.,30°)could optimize the mechanical properties and damage failure characteristics of glass laminates.The results of the numerical and analytical approaches demonstrated their ability to capture the mechanical behavior and damage failure modes of composite laminates with different fiber orientations,which may be used to prevent the catastrophic failures that occur in composite laminates.

地热能在预热中的应用综述

考虑到化石燃料的环境污染和成本波动等问题,发展可再生能源技术是未来可持续能源供应的必要和必然。与太阳能和风能相比,地热能在一天中的所有时间都是可利用的。这种可再生能源适用于供暖、制冷、淡水和电力的清洁供应。地热能除了作为主要能源直接用于发电外,还可以作为辅助热源用于预热,减少温室气体排放,节约燃料。在这些系统中,利用地热热源的热量进行蒸汽预热。此外,地热能可用于其他能源系统,如制氢装置,用于预热电解过程中消耗的水。针对利用地热能进行预热的优势,综述了地热能预热系统的应用研究。通过这一研究可以看出,利用地热能进行预热在节约燃料和提高性能方面具有很大的潜力。上述系统的性能取决于系统的配置、钻孔规格和地热源温度等因素。通过实施优化,可以进一步改进这些系统。

Cellulose-based composite scaffolds for bone tissue engineering and localized drug delivery

Natural bone constitutes a complex and organized structure of organic and inorganic components with limited ability to regenerate and restore injured tissues,especially in large bone defects.To improve the reconstruction of the damaged bones,tissue engineering has been introduced as a promising alternative approach to the conventional therapeutic methods including surgical interventions using allograft and autograft implants.Bioengineered composite scaffolds consisting of multifunctional biomaterials in combination with the cells and bioactive therapeutic agents have great promise for bone repair and regeneration.Cellulose and its derivatives are renewable and biodegradable natural polymers that have shown promising potential in bone tissue engineering applications.Cellulose-based scaffolds possess numerous advantages attributed to their excellent properties of non-toxicity,biocompatibility,biodegradability,availability through renewable resources,and the low cost of preparation and processing.Furthermore,cellulose and its derivatives have been extensively used for delivering growth factors and antibiotics directly to the site of the impaired bone tissue to promote tissue repair.This review focuses on the various classifications of cellulose-based composite scaffolds utilized in localized bone drug delivery systems and bone regeneration,including cellulose-organic composites,cellulose-inorganic composites,cellulose-organic/inorganic composites.We will also highlight the physicochemical,mechanical,and biological properties of the different cellulose-based scaffolds for bone tissue engineering applications.

一种改进螺旋双管换热器传热性能的叶片半圆锥形紊流器

本文提出了一种内部具有叶片及半圆锥形双孔紊流器的螺旋双管换热器。研究了紊流叶片角θ和紊流叶片数N对传热性能的影响。结果表明:热分层在θ=180°时达到最佳;在最小质量流率(m=8×10^(-3)kg/s)条件下,叶片倾角为180°的紊流器的换热系数比不含紊流器、及叶片倾角为240°和360°的紊流器分别高130.77%、25%和36.36%。N=12的综合性能表现最好。在最大质量流率下(m=5.842×10^(-2)kg/s),N=12时的换热系数比无紊流器、叶片数为6和9时的换热系数分别提高了54.76%、27.45%和6.56%。

Conceptual Design Process for LEO Satellite Constellations Based on System Engineering Disciplines

Satellite design process is an interdisciplinary subject in which the need for collaboration among various science and engineering disciplines is evident.Meanwhile,finding an optimal process for conceptual design of a satellite,which can optimize time and cost,is still an important issue.In this paper,based on system engineering approach,an optimal design process is proposed for LEO satellite constellations.In the proposed method,design process,design sequences,and data flow are established.In this regard,the conceptual design process is divided into two levels of mission(or constellation)and system(or satellite)as well as 15 main activities based on the mission profile,previous experiences of the authors,and existing literature.Then,the relationships between these activities have been determined by considering the importance of relationships according to their priority.Finally,these relations are optimized based on design structure matrix(DSM).By utilizing this approach,system design process of a telecommunication satellite constellation in LEO is formulated in conceptual design phase.Performance and capability of the proposed approach in optimal design process of the satellite constellation are investigated by comparing the outcome with existing results in the literature.

Exergetic sustainability evaluation and optimization of an irreversible Brayton cycle performance

Owing to the energy demands and global warming issue, employing more effective power cycles has become a responsibility. This paper presents a thermo-dynamical study of an irreversible Brayton cycle with the aim of optimizing the performance of the Brayton cycle. Moreover, four different schemes in the process of multi-objective optimization were suggested, and the outcomes of each scheme are assessed separately. The power output, the concepts of entropy generation, the energy, the exergy output, and the exergy efficiencies for the irreversible Brayton cycle are considered in the analysis. In the first scheme, in order to maximize the exergy output, the ecological function and the ecological coefficient of performance, a multi-objective optimization algorithm (MOEA) is used. In the second scheme, three objective functions including the exergetic performance criteria, the ecological coefficient of performance, and the ecological function are maximized at the same time by employing MOEA. In the third scenario, in order to maximize the exergy output, the exergetic performance criteria and the ecological coefficient of performance, a MOEA is performed. In the last scheme, three objective functions containing the exergetic performance criteria, the ecologi-cal coefficient of performance, and the exergy-based ecological function are maximized at the same time by employing multi-objective optimization algorithms. All the strategies are implemented via multi-objective evolu-tionary algorithms based on the NSGAII method. Finally, to govern the final outcome in each scheme, three well- known decision makers were employed.