Theoretical Analysis of a Shell and Tubes Condenser with R134a Working Refrigerant and Water-Based Oxide of Aluminum Nanofluid (Al₂O₃)

The article analyzes a shell and tube type condenser’s thermal performance using concepts of efficiency and effectiveness. Freon 134a is used as a coolant flowing through the shell. Water or water-based aluminum oxide nanoparticles are at relatively low saturation pressure in the tube. The condenser consists of 36 tubes divided into three central regions for analysis: superheated steam, saturated steam, and subcooled liquid. The three regions contain four tubes with three steps each, that is, 12 tubes. Region I, superheated steam, includes three horizontal baffles. Profiles of temperature, efficiency, and effectiveness are presented graphically for the three regions, with fixed refrigerant flow equal to 0.20 kg/s and fluid flow rate in the tube ranging from 0.05 kg/s to 0.40 kg/s. The experimental result for vapor pressure equal to 1.2 MPa and water flow equal to 0.41 kg/s was used as one of the references for the model’s physical compatibility.

Effects of R134a Saturation Temperature on a Shell and Tube Condenser with the Nanofluid Flow in the Tube Using the Thermal Efficiency and Effectiveness Concepts

The work’s objective is to analyze the influence of the saturation temperature of the R134a refrigerant on the thermal performance of a shell and tube type condenser, with water and aluminum oxide (Al2O3) nanoparticles flowing into the tube. For analysis, the heat exchanger is subdivided into three regions: subcooled liquid, saturated steam, and superheated steam. The shell and tube heat exchanger assumed as the basis for the study has 36 tubes, with rows of 4 tubes in line and three passes into the tube in each region. The parameters used to analyze the performance are efficiency and effectiveness, through variations of quantities such as saturation temperature, the nanofluid’s mass flow rate, fraction in the nanoparticles’ volume, and the number of passes in the tube in each region of the heat exchanger. The obtained results demonstrate that the efficiency is relatively high in all the analyzed situations. In each saturation temperature, the effectiveness can be increased by introducing fractions of nanoparticles in the water or increasing the number of passes in the tube.

Cl/S与Na相互作用对Shell气化炉合成气冷却器入口积灰机制的影响

Shell干粉煤加压气化是煤炭洁净高效利用的重要技术之一,由碱金属化合物引起的合成气冷却器入口积灰结垢是导致气化炉非正常停工检修的主要原因。以添加不同含量的Na、Cl和S的Shell气化炉飞灰为原料,利用自主设计的高温竖直炉中沉积探针模拟Shell气化炉合成气冷却器入口管路,通过对积灰进行内、外分层研究,探讨内外层积灰质量的变化,并结合ICP-MS、IC、SEM-EDS和XRD等表征手段对内外层积灰的理化性质进行比较分析,获得Na、Cl、S和Fe等不同元素之间的相互作用对积灰行为的影响。结果表明,内层积灰质量随时间延长而增大,含S化合物的添加会降低内外层积灰质量,且外层积灰质量会随着时间延长而减小。Na更多以铝硅酸盐形式在外层积灰中存在,促进积灰增长;Cl通常以碱金属氯化物的形式集中在初始黏性层;S的存在会减缓管路积灰;当Cl和S共同存在时,Fe易与灰中的Si、Al和Na形成多种低温共熔物促进内、外层积灰熔融。Shell气化炉合成气冷却器入口积灰形成机制为:飞灰颗粒组分在Na、Cl、Si和Al的共同作用下,于内层形成碱金属氯化物和铝硅酸盐共晶;同时Cl、S的存在促使Fe和Na迁移到这些共晶中,形成Fe-O-Si、Fe-O-S和Fe-Na-O-Al-S共熔体。进而,铝硅酸盐与多种低温共熔体相互熔融使灰颗粒尺寸增加,促进积灰的进一步生长。

Shell煤气化工艺高温高压飞灰过滤器S1501分析及解决措施

S1501飞灰过滤器系统对Shell煤气化正常生产发挥着重要作用。介绍了S1501飞灰过滤器系统,分析了该系统发生故障的原因,并提出了解决措施。

Shell—Paques工艺在炼油厂脱硫系统的应用

本文介绍Shell—Paques工艺以及在炼油厂脱硫系统中的应用案例。从反应机理、原料要求、工艺流程及控制等方面与克劳斯工艺进行比较．显示出Shell—Paques工艺在硫磺回收规模不大的中小型炼油厂应用具有较大优势。

基于K-shell的超网络关键节点识别方法

将K-shell指标扩展到超网络中,避免了超网络中超度较大、但位于超网络边缘位置的节点对挖掘关键节点带来的影响。由于K-shell方法的局限性,导致节点排序结果过于粗糙。针对这一问题,结合超度和K-shell(ks)值利用欧式距离公式提出识别超网络关键节点的k^(d)_(s)指标,并利用蛋白复合物超网络进行验证。实验证明,k^(d)_(s)指标能够准确有效地识别超网络中的关键节点。

Vibration characteristics of FGM circular cylindrical shells filled with fluid using wave propagation approach

The vibration characteristics of a functionally graded material circular cylindrical shell filled with fluid are examined with a wave propagation approach. The shell is filled with an incompressible non-viscous fluid. Axial modal dependence is approximated by exponential functions. A theoretical study of shell vibration frequencies is analyzed for simply supported-simply supported, clamped-simply supported, and clamped-clamped boundary conditions with the fluid effect. The validity and the accuracy of the present method are confirmed by comparing the present results with those available in the literature. Good agreement is observed between the two sets of results.

Fast Prediction of Acoustic Radiation from a Hemi-capped Cylindrical Shell in Waveguide

In order to predict acoustic radiation from a structure in waveguide, a method based on wave superposition is proposed, in which the free-space Green＇s function is used to match the strength of equivalent sources. In addition, in order to neglect the effect of sound reflection from boundaries, necessary treatment is conducted, which makes the method more efficient. Moreover, this method is combined with the sound propagation algorithms to predict the sound radiated from a cylindrical shell in waveguide. Numerical simulations show the effect of how reflections can be neglected if the distance between the structure and the boundary exceeds the maximum linear dimension of the structure. It also shows that the reflection from the bottom of the waveguide can be approximated by plane wave conditionally. The proposed method is more robust and efficient in computation, which can be used to predict the acoustic radiation in waveguide.

Dyeing of S/J Cotton Knit Fabric with Natural Dye Extracts from Green Walnut Shells: Assessment of Mordanting Effect on Fastness Properties

In this study, aqueous extraction method is used because of its high extraction ratio, light fastness and also functional properties. In 1st phase, for dyeing S/J cotton knit fabric with green walnut power ferrous sulfate is considered as a mordant. In this study, three different mordanting methods such as pre-, meta-, and post-mordanting are conveyed the dyeing process with the state of metallic mordant and without metallic salt mordants. In 2nd phase, in dyeing for fixation ferrous sulfate was considered as mordants. Furthermore, the analysis and evaluation of each colour dyed material was done through following two terms for instance CIELAB (L*, a*, and b*) and K/S values. According to AATCC test methods, colour fastness to washing, crocking, perspiration of the dyed samples is determined whereas according to the ISO standard, the colour fastness to light was estimated and tested. When dyeing was carried out on S/J cotton knit fabric through considering optimum parameter like at 80&degC for 60 min and at pH 4 which showed optimum results. From the results we can see, very good wash fastness was obtained while there is no fading of the colour, whereas the outstanding and moderate level of colour fastness to light and crocking is achieved.

Neumann＇s method for boundary problems of thin elastic shells

The possibility of using Neumann＇s method to solve the boundary problems for thin elastic shells is studied. The variational statement of the static problems for the shells allows for a problem examination within the distribution space. The convergence of Neumann＇s method is proven for the shells with holes when the boundary of the domain is not completely fixed. The numerical implementation of Neumann＇s method normally requires significant time before any reliable results can be achieved. This paper suggests a way to improve the convergence of the process, and allows for parallel computing and evaluation during the calculations.

On Axially Symmetric Vibrations of Fluid Filled Poroelastic Spherical Shells

Employing Biot’s theory of wave propagation in liquid saturated porous media, waves propagating in a hollow poroelastic closed spherical shell filled with fluid are studied. The frequency equation of axially symmetric vibrations for a pervious and an impervious surface is obtained. Free vibrations of a closed spherical shell are studied as a particular case when the fluid is vanished. Frequency as a function of ratio of thickness to inner radius is computed in absence of dissipation for two types of poroelastic materials each for a pervious and an impervious surface. Results of previous works are obtained as a particular case of the present study.

Shell煤气化S1201积料原因分析与防范措施

shell煤气化中S1201积料原因进行分析,介绍了解决积料问题的处理办法。

Shell煤制甲醇之Lurgi低温甲醇洗出口H_2S超标浅析

介绍了Shell粉煤气化制甲醇工艺中低温甲醇洗系统流程及实际运行情况。对装置运行H2S超标问题进行分析、采取有效改造措施、技术操作优化调整。解决净化气H2S超标对合成催化剂的影响,保证装置的安全稳定运行。

Topology Chemical Process Research on the Condensing and Growing Phase Multi Micro Oil Droplets Based on Hydrodynamics

The hydrodynamic research about the droplet condensing of the multi phase liquid state on the surface of the coal glass and water discusses the deepening process of convex shape curve and the formation of S shape, and puts emphasis on describing the diagram formation method of the later. In the induction period the active diagram of the micro droplet is decided by pH value forming as convex shape diagram or S shape diagram. When pH value is above 4.0, the damage of convex shape diagram cannot be recovered, in that case produce S shape activity diagram. When pH value is equal to or above 12.0, the hard surface with alkali liquid state loses adhesion, so that the micro droplet condensing of the multi phase liquid state stops completely. The research result shows that the water cleaning conditions of getting rid of the oil micro droplets can be decided by the pH value.

Infrared light-emitting diodes based on colloidal Pb Se/Pb S core/shell nanocrystals

Colloidal Pb Se nanocrystals(NCs)have gained considerable attention due to their efficient carrier multiplication and emissions across near-infrared and short-wavelength infrared spectral ranges.However,the fast degradation of colloidal Pb Se NCs in ambient conditions hampers their widespread applications in infrared optoelectronics.It is well-known that the inorganic thick-shell over core improves the stability of NCs.Here,we present the synthesis of Pb Se/Pb S core/shell NCs showing wide spectral tunability,in which the molar ratio of lead(Pb)and sulfur(S)precursors,and the concentration of sulfur and Pb Se NCs in solvent have a significant effect on the efficient Pb S shell growth.The infrared light-emitting diodes(IR-LEDs)fabricated with the Pb Se/Pb S core/shell NCs exhibit an external quantum efficiency(EQE)of 1.3%at 1280 nm.The ligand exchange to optimize the distance between NCs and chloride treatment are important processes for achieving high performance on Pb Se/Pb S NC-LEDs.Our results provide evidence for the promising potential of Pb Se/Pb S NCs over the wide range of infrared optoelectronic applications.

Nonlinear vibration of corrugated shallow shells under uniform load

Based on the large deflection dynamic equations of axisymmetric shallow shells of revolution, the nonlinear forced vibration of a corrugated shallow shell under uniform load is investigated. The nonlinear partial differential equations of shallow shell are reduced to the nonlinear integral-differential equations by the method of Green＇s function. To solve the integral-differential equations, expansion method is used to obtain Green＇s function. Then the integral-differential equations are reduced to the form with degenerate core by expanding Green＇s function as series of characteristic function. Therefore, the integral-differential equations become nonlinear ordinary differential equations with regard to time. The amplitude-frequency response under harmonic force is obtained by considering single mode vibration. As a numerical example, forced vibration phenomena of shallow spherical shells with sinusoidal corrugation are studied. The obtained solutions are available for reference to design of corrugated shells .

Free vibration of layered cylindrical shells filled with fluid

The vibration of the layered cylindrical shells filled with a quiescent, incompressible, and inviscid fluid is analyzed. The governing equations of the cylindrical shells are derived by Love＇s approximation. The solutions of the displacement functions are assumed in a separable form to obtain a system of coupled differential equations in terms of the displacement functions. The displacement functions are approximated by Bickley-type splines. A generalized eigenvalue problem is obtained and solved numerically for the frequency parameter and an associated eigenvector of the spline coefficients. Two layered shells with three different types of materials under clamped-clamped （C-C） and simply supported （S-S） boundary conditions are considered. The variations of the frequency parameter with respect to the relative layer thickness, the length-to-radius ratio, the length-to-thickness ratio, and the circumferential node number are analyzed.

Collective Excitations in Spin-2 Bose-Einstein Condensates

The Green＇s functions and the correlation functions in spin-2 Bose-Einstein condensates at finite temperature are defined and the generalized Dyson-Beliaev equations are introduced. We discuss the spin conservation in z direction and decouple the Green＇s functions and the generalized Dyson-Beliaev equations according to different spin conservations in z direction. The anomalous vertex functions are introduced and the self-energies are separated into the proper self-energies and the improper self-energies. The generalized Dyson-Beliaev equations are decoupled according to separation of the self-energies. We calculate the Green＇s functions step by step in the Bogoliubov approximation and discuss the collective excitations in spin-2 Bose-Einstein condensates in the polar, ferromagnetic, and cyclic cases, respectively.

METHOD OF GREEN’S FUNCTION OF CORRUGATED SHELLS

By using the fundamental equations of axisymmetric shallow shells of revolution, the nonlinear bending of a shallow corrugated shell with taper under arbitrary load has been investigated. The nonlinear boundary value problem of the corrugated shell was reduced to the nonlinear integral equations by using the method of Green＇s function. To solve the integral equations, expansion method was used to obtain Green＇s function. Then the integral equations were reduced to the form with degenerate core by expanding Green＇s function as series of characteristic function. Therefore, the integral equations become nonlinear algebraic equations. Newton＇ s iterative method was utilized to solve the nonlinear algebraic equations. To guarantee the convergence of the iterative method, deflection at center was taken as control parameter. Corresponding loads were obtained by increasing deflection one by one. As a numerical example,elastic characteristic of shallow corrugated shells with spherical taper was studied.Calculation results show that characteristic of corrugated shells changes remarkably. The snapping instability which is analogous to shallow spherical shells occurs with increasing load if the taper is relatively large. The solution is close to the experimental results.

Characterization of Unsaturated Polyester Filled with Waste Coconut Shells, Walnut Shells, and Carbon Fibers

This study aims to evaluate the erosion behavior and the hardness of hybrid composites made of varying amounts of coconut shells,walnut shells,and carbonfibers dispersed in a polyester matrix.MINITAB(L16)Taguchi experiments were used to determine the optimal combination of parameters.In particular,an erosion device con-sisting of a motor with a constantflow rate of 45 L/min,a pump with a diameter of 40 mm,a nozzle with a dia-meter of 5 mm,and a tank made of“perspex glass”55 cm long,30 cm tall,and 25 cm wide was used.The tests were conducted by varying the sample-to-nozzle distance,the pattern angle,and the sand particle size.The results have revealed that the presence of 7.5%by weight of waste coconut shell,for conditions corresponding to 90°angle,sand size 425μm,stand distance 30 cm,gives the best wear resistance(3.04×10^(-5) g/g).Thefiller content and sand particle size affect the erosive rate,with the angle playing a secondary role.The distance between the sample and the nozzle has a weaker effect on erosive wear.The hardness results show that the models(UP-5%carbonfiber-2.5-3.5-4.5-5.5-6.5-7.5 wt.%waste coconut shell)give the best values for prayer compared to the samples(UP-5 wt.%carbonfiber-2.5-3.5-4.5-5.5-6.5-7.5 wt.%waste walnut shell).