制冷系统设备机组化的发展趋向

DevelopmentTendencyofAggregationofRenfrigerationEquipment随着现代食品冻结装置的日益发展及人们工作生活节奏的不断加快，制冷系统设备机组作为替代传统制冷系统的一种新的结构型式，其优越性愈来愈得到人们的普遍认识。制冷系统设备机组，即把实现制冷循环所需的制冷压缩     

户式中央空调发展方向的探讨

本文描述了我国户式中央空调的发展现状，分析了三种户式中央空调各自的特点，提出了把风管式机组作为我国户式中央空调的发展方向。     

空调主机的选型及其它

本文资料摘自《暖通空调》的有关论文，其目的是想通过资料分析，正确选择空调的主机，更好的为国家建设服务。     

氟里昂压缩冷凝机组的构成及其工作原理

文章主要介绍氟里昂压缩冷凝机组的构成及其工作原理，进行分析，以便大家详细了解，促进氟里昂压缩冷凝机组的技术发展及技术进步。     

螺杆制冷压缩机组的安装与试运行

介绍JZKA31.5螺杆制冷压缩机组的结构特点及在安装中应注意的事项，试车的方法以及试运行情况。     

火电汽轮机基础设计及动力分析

本文对沙岭子３００ＭＷ汽轮发电机基础设计的介绍，简要说明了低频钢筋混凝土基础的原理，汽轮发电同分缸机组和合缸机组的差异，以及设计泊轮发电机组基础的步骤。     

洁净室控制系统设计

为了保证洁净室的洁净等级，洁净室控制系统应具有较高的可靠性和稳定性，本文以S7-300PLC为控制单元，介绍了每一个控制过程如何实现，完全能够满足洁净室控制系统使用要求。     

武汉地区中央空调系统冷热源的选择

通过对现有大型公共建筑中央空调系统冷热源类型和能耗的调查研究，比较了不同类型的冷热源型式；结合当前武汉地区能源状况，新政策以及当前的新技术，探索了武汉地区中央空调系统冷热源的选择。     

商用陈列柜选用机组探讨

随着便利店、超市和购物中心等的不断发展，商用陈列柜也得到了广泛的应用，陈列柜的低有耗对于保护环境、节约电力和降低动物费用等都有十分重要意义。文中分析了影响陈列柜冷冻负荷和冷冻能力的因素，阐明了温度以对冷冻负荷和冷冻能力的影响，对比了多台并联压缩机组和单台压缩机组的特点，为实际机组的选配和使用提供了方便。     

台州发电厂网络版计量管理系统应用效果初显

台州发电厂现有6台135MW机组、2台330MW机组，并正在扩建2台330MW机组。目前，全厂共有测量设备2万多台，如果采用传统的管理方式．就无法保证所有测量设备动态管理信息的实时准确．无法统计测量设备的检定情况。无法确保用于企业的计量标准器、安全防护、环境监测、贸易结算等强检测量设备的有效受控，以及生产现场关键工艺点、质量分析仪器等重要测量设备的测量数据的准确性。     

A simple dynamic model for eddy currents in a magnetic actuator

This paper presents a simple dynamic model of eddy currents in a magnetic actuator. The model is based on the application of Maxwell's equations to a homogeneous ferromagnetic conductive material. The resulting diffusion equation is solved in two dimensions for a cross-sectional cut through a rectangular bar; boundary conditions are imposed by a sinusoidally varying actuator coil current. The utility of the new modeling approach is illustrated by predicting the dynamic performance of a magnetic bearing actuator. The predictions are found to be in good agreement with measured values. The model provides a new and convenient method of modeling the relationships among voltage, current, force, and flux in magnetic circuits containing eddy currents     

Statistical Analysis of Macromolecular Chains in the Space Filled by Nanoparticles

The paper presents a combination of worm-like chain numerical models and one with a finite set of nano-particles. The primary objective of the models was to analyze the distribution of space in a system filled by particles. Information on the distribution of space was compared to properties of chains inside the set of particles. The set of nanoparticles was constructed with a tool generating a finite set of particles that is randomly distributed in a given space. The particles have a prescribed volume fraction and uniform size. First, the proportions of chains and particles were compared. The length of chain was expressed in terms of end-to-end length. It was then compared to the size of gaps between two particles. The volume of chain was compared to the volume of space delimited by the particles. Next, a set of 10,000 random chains was generated and these were introduced into the particle set. The contact of a chain with the surface of a particle resulted in the special structural elements of the chain: a chain connecting two different particles, a loop which begins and ends at the same particle, a part of a chain which is completely adhered to the particle surface, a chain attached to a particle with one free end, as well as completely free chains. The chains were classified under three classes: chains which were not in contact with particles, chains which were in contact with one particle, and chains which were in contact with two or more particles. A statistical representation of each class is presented. The contact between chain and particle can influence macroscopic properties such as those that are elastic.     

Artificial layer

The spreading of scalar waves through a structure called the artificial layer is investigated. The artificial layer is a clearance between a piston-type radiator and an acoustically hard grating. The main application of this structure is a matching layer for an ultrasonic transducer in a low-acoustic impedance medium (in air). The mathematical model of this artificial layer is constructed and reduced to explicit analytical expressions that are convenient in engineering practice. The errors of these analytical expressions are estimated with the help of a numerical solution of the problem in exact formulation. Two problems connected with the artificial layer are investigated numerically: a scalar wave spreading in a stepped waveguide with acoustically hard sides, and a scalar wave spreading through a grating of finite thickness. The artificial matching layer is investigated experimentally at radiation of ultrasonic waves in air.     

Thermal behavior and energy storage of a suspension of nano-encapsulated phase change materials in an enclosure

The energy storage capability of a suspension of Nano-Encapsulated Phase Change Material (NEPCM) nanoparticles was addressed in an enclosure during the charging and discharging process. The nanoparticles contain a Phase Change Material (PCM) core, which are capable to absorb a notable quantity of thermal energy on melting. There is a heat pipe in the cavity at the bottom corner, which is enhanced by a layer of metallic matrix. The natural convection flow occurs due to a temperature gradient during the charging or discharging process. The particles of NEPCM move with the natural convection flow and contribute to heat transfer & storage of thermal energy. The regulating equations for the heat transfer & flow of the NEPCM suspension were established & converted in the non-dimensional type. The finite element method (FEM) was utilized in resolving the equations. The results show that there was a rise in the rate of heat transfer & storage of total energy with a rise in nanoparticles volume fraction. The decrease of the Stefan number from 0.2 to 0.6 increases the total stored energy by 25%. The fusion temperature is another important parameter in which its behavior depends on the charging or discharging process.     

Application of the theory of Markov chains to theoretical study of processes in a circulating fluidized bed

Abstract

The objective of the study is to develop a simple yet informative model to investigate the features of the process of particulate flows formation in a circulating gas-solid fluidized bed. The proposed model is based on the theory of Markov chains. The riser is presented as a chain of perfectly mixed cells. The conversion of particles of a source material into particles of an end product occurs in these cells due to this or that chemical or thermo-physical process. The transportation of material over the chain is controlled by a matrix of transition probabilities. The return flow that comes from a separator is routed to the downer, which is described as a plug flow apparatus that has a time delay between the inflow and outflow issuing from it. The outflow is routed back into the riser. The numerical experiments were carried out for the batch fluidization. It is found that the batch circulating fluidization only has advantages over the dense bed under a small time delay in the downer and a relatively high gas flow velocity in the riser. The results of laboratory tests performed at the circulating fluidized bed demonstrated a good qualitative correlation with the theoretical data.     

Deformation of erythrocytes and aggregates during sedimentation under microgravity

The basic unit of an aggregate is an erythrocyte which possesses viscoelastic properties. To determine the changes in the shape of erythrocytes during sedimentation in microgravity field the present work is carried out. Fresh well mixed erythrocytes suspensions in plasma at 8% hematocrit are placed in a glass chamber. The entire experimental setup is mounted in a module and placed in a capsule. The online data on the sedimentation of the cells under normal and microgravity are recorded by a video microscopic system. The data are analysed by a PC/AT based image processing system. The results show that the erythrocyte undergoes a process of shape deformation and its sedimentation velocity decreases during microgravity. The erythrocyte from a nearly elliptic shape is transformed to nearly circular shape. A similar change in the projected area of the aggregate is also observed. This is further supported by a varying pattern of sedimentation velocity from normal to microgravity duration. The observed change in the erythrocyte membrane may contribute in the loosening of the large aggregates leading to formation of smaller size aggregates.     

Transmission and radiation in a slab waveguide coupled to a whispering-gallery resonator: volume-integral-equation analysis

The excitation of a whispering gallery resonator by a surface wave guided in a dielectric slab is analyzed with a rigorous volume-integral-equation approach. The analysis is based on the Green's function concept and the application of the entire-domain Galerkin technique through expansion of the electric field in the resonator in terms of cylindrical wave functions. The algorithm developed yields highly accurate results for the transmission and reflection coefficients in the waveguide. The radiated far field is computed, and the effect of the excitation of a whispering gallery mode on the radiation pattern is studied.     

Frequent Failures of Motor Shaft in Seawater Desalination Plant: Some Case Studies

The failure of a shaft from a motor in a pump or a compressor has been a phenomenon of common occurrence in seawater desalination plants. The origin of the problem in majority of cases is either the inability of the material to withstand the level of dynamic stresses to which shaft is subjected during operation and/or inadequacy of the design. The shortcoming in the design may be responsible for initiating localized corrosion which ultimately leads to failure of the component. The mode of failure of the shaft could be stress-related failure such as stress corrosion cracking, mechanical fatigue or corrosion fatigue, and/or localized corrosion such as crevice corrosion. This paper describes some recent case studies related to shaft failures in seawater desalination plants. The case studies include shearing of a shaft in brine recycle pump in which a combination of environment, design, and stresses played important role in failure. In another case, ingress of chloride inside the key slot was the main cause of the problem. The failure in a high pressure seawater pump in a SWRO plant occurred due to cracking in the middle of the shaft.     

The drift resonance and isolation of charged particles in a toroidal magnetic trap modeled using the Newton-Lorentz equation and a set of the drift equations of motion

The motion of a charged particle in a toroidal-helicoidal magnetic field was modeled. The drift resonance of the particle with a magnetic perturbation and the phenomenon of particle trapping on an inhomogeneity of this field were studied using two approaches, based on solving a set of the drift equations or the exact Newton-Lorentz equation of motion. The two approaches exhibit a good quantitative coincidence in describing the drift resonance and show a qualitative agreement in describing the motion of a trapped particle. The approach based on the exact equations of motion reveals some new features in the phenomenon of particle trapping, which are of importance from the standpoint of determining the neoclassical transfer coefficients.