两种池沸腾强化换热管的传热性能实验研究

对两种用于池沸腾换热的强化管在蒸发温度为5℃的工况下进行了水平管外传热性能的实验研究.两种管子为管内外双侧强化管,管外表面同属于TURBO-B类的强化换热管,但表面形状有区别.利用威尔逊图解法确定这两种管型的管内外换热系数的关联式,同时,根据实验测得的数据对这两种管型的换热性能进行比较.结合金相显微镜拍摄的外观形状,分析尺寸结构对强化换热管的换热性能的影响.结果得出:在相同工况下,准三角形形状的管内螺纹换热性能要比梯形好,且管内螺纹数越多,换热性能越好;在一定热流密度范围内,管外换热系数随着热流密度的增加而变大,这主要与管子外表面结构的凹穴半径、凹穴开口尺寸、次级表面通道的宽度和形状等因素有关,且翅顶表面刻画的浅槽有利于池沸腾换热.     

JSP数据库连接池的设计

探讨了JSP数据库连接池的设计思想和实现方法,在连接池的调度管理下,连接池动态地保持一定量的,并且保持不大于一定使用次数的空闲连接,使Web访问数据库的性能达到最佳。     

MBR膜处理控制系统的实现

该文围绕MBR膜处理系统工艺,主要介绍了该控制系统的结构、组成、硬件配置和软、硬件设计。该系统以西门子S7—300系列PLC为控制核心,通过以太网与上位机通信,实现命令输入以及图形显示,通过PROFIBUS—DP现场总线与8个PLC功能子站进行数据通信,从而实现对整个系统的控制。PLC编程软件采用SIMATICSTEP7V5．4＋SP4,上位机软件采HMISCADAIFIX4．0组态软件。     

基于Iu_Flex的MSC Pool技术分析

本文简要介绍了MSC Pool技术的基本原理．分析了MSC Pool所用到的关键技术．重点讨论D接口信令的流量和MSC Pool的组网规划．指出了MSC Pool可能存在的安全隐患。     

A fortran program for Monte Carlo simulation of oil-field discovery sequences

We have developed a program for performing Monte Carlo simulation of oil-field discovery histories. A synthetic parent population of fields is generated as a finite sample from a distribution of specified form. The discovery sequence then is simulated by sampling without replacement from this parent population in accordance with a probabilistic discovery process model. The program computes a chi-squared deviation between synthetic and actual discovery sequences as a function of the parameters of the discovery process model, the number of fields in the parent population, and the distributional parameters of the parent population. The program employs the three-parameter log gamma model for the distribution of field sizes and employs a two-parameter discovery process model, allowing the simulation of a wide range of scenarios.     

Effect of nanoparticles on CHF enhancement in pool boiling of nano-fluids

To investigate the characteristics of CHF (Critical Heat Flux) enhancement using nano-fluids, pool boiling CHF experiments of two water-based nano-fluids with titania and alumina nanoparticles were performed using electrically heated metal wires under atmospheric pressure. The results showed that the water-based nano-fluids significantly enhanced CHF compared to that of pure water. SEM (Scanning Electron Microscopy) observation subsequent to the pool boiling experiments revealed that a lot of nanoparticles were deposited on heating surface during pool boiling of nano-fluids. In order to investigate the role of the nanoparticle surface coating on CHF enhancement of nano-fluids, pool boiling CHF of pure water was measured using a nanoparticle-coated heater prepared by pool boiling of nano-fluids on a bare heater. It was found that pool boiling of pure water on the naonoparticle-coated heater sufficiently achieved the CHF enhancement of nano-fluids. It is supposed that CHF enhancement in pool boiling of nano-fluids is mainly caused by the nanoparticle coating of the heating surface.     

快堆钠池传热流动三维模型与数值模拟

针对快中子增殖反应堆钠池的流动传热特点，以质量、动量、能量守恒定律为基础，建立有关快堆钠池流动传热的三维数学模型。池内流动域中障碍物对流动和传热的影响采用空隙率和穿透率的概念来描述；钠池与其围护结构的传热关系采用耦合计算方法求解。编写了基于压力校正法和交错网格的三维流动传热模拟计算程序ＦＡＳＴＯＲ－３Ｄ。该程序通过了若干经典算例的验证计算，并应用于实际的三维钠池流动传热模拟，获得了大量的预测数据。附属软件ＤＶ以色彩表达流场、温度场等三维物理量的大小强弱，实现了大批量数据的可视化分析。     

Analysis of radionuclide retention in water pools

An analysis is presented of the removal of aerosol particles and gaseous fission products from steam-noncondensable gas mixtures rising through water pools. The pool is divided into a gas injection zone, a bubble rise zone and a pool surface zone. The formulation of the governing conservation equations is relatively general with a quasi-steady one-dimensional formulation for the gas phase, and an unsteady, well stirred, formulation for the liquid phase. An associated computer code for performing the calculations, SUPRA, is described. Results of parametric calculations are given for conditions expected in a BWR severely degraded core accident sequence. Parameters studied include aerosol particle size and distribution, mass fraction of noncondensable gas, gas mass flow rate, quencher submergence depth, and pool water temperature.     

Review on pool boiling heat transfer of carbon dioxide

Although application of carbon dioxide as working fluid in many fields of refrigeration technology has been recommended very often in the recent past, the data on nucleate boiling heat transfer of carbon dioxide in free convection are very scarce in the open literature and new investigations are almost entirely focussed on forced convective flow boiling. In the interpretation of the respective results, heat transfer to carbon dioxide is often characterized as being superior to other refrigerants due to the outstandingly favourable thermophysical properties of carbon dioxide for boiling heat transfer. Different from this view, the discussion of recent results on pool boiling heat transfer of carbon dioxide in this review demonstrates that the high heat transfer coefficients measured for carbon dioxide in comparison to hydrocarbon or halocarbon refrigerants are mainly due to the fact that application of carbon dioxide is mostly envisaged for conditions where reduced saturation pressure p*=p_s/p_c (p_c, critical pressure) is higher than for common refrigerants.

In the first part of the review, the three main influences—by heat flux, saturation pressure and fluid properties—on pool boiling of carbon dioxide are discussed using recent measurements for CO₂ by Kotthoff et al. [S. Kotthoff, U. Chandra, D. Gorenflo, A. Luke, New measurements of pool boiling heat transfer for carbon dioxide in a wide temperature range, Proceedings of the Sixth IIR-Gustav Lorentzen Conference, Glasgow, 2004 [paper 2/A/3.30]; see also S. Kotthoff, U. Chandra, D. Gorenflo, Neue Messungen zum Behältersieden von Kohlendioxid in einem grösseren Temperaturbereich, DKV-Tagungsbericht 22 (2004) [Bd.II. 1] 233–256 and other organic substances (Gorenflo et al.) [D. Gorenflo, S. Kotthoff, U. Chandra, New measurements of pool boiling heat transfer with hydrocarbons and other organics for update of VDI—Heat Atlas calculation method, Proceedings of the Sixth IIR-Gustav Lorentzen Conference, Glasgow, 2004 [paper 1/C/1.00]; Kotthoff and Gorenflo, [S. Kotthoff, D. Gorenflo, Influence of the fluid on pool boiling heat transfer of refrigerants and other organic substances, Proceedings of the IIR-Commission B1 Conference, Vicenza, 2005 [paper #TP-98]. In the second part, a comparison is given with the few former data available and with new results of Loebl and Kraus [S. Loebl, W.E. Kraus, Pool boiling heat transfer of carbon dioxide on a horizontal tube, Proceedings of the Sixth IIR-Gustav Lorentzen Conference, Glasgow, 2004 [paper 1/A/1.20]; S. Loebl, W.E. Kraus, Zum Wärmeübergang bei der Verdampfung von Kohlendioxid am horizontalen Rohr, DKV-Tagungsbericht 22 (2004) [Bd.II.1] 219–232 on the influence of the heating wall (material and surface roughness). Finally, analogies between nucleate pool boiling and new flow boiling data are shown for those domains of flow boiling in which nucleation provides the dominant contribution to heat transfer and convective effects are of secondary importance.     

数据库连接池的分析与实现

在分析直接通过JDBC连接数据库这种连接方式的基础上,指出了传统数据库连接技术中存在的运行效率低、软件移植性和复用性差等不足之处。文中研究了数据库连接池技术,并在工程应用中加以实现。该技术方案有效地解决了在企业级应用中数据库连接的效率问题、应用程序代码的移植问题和数据库连接的封装问题。