价值工程在热网结构优化中的运用

价值工程是以提高产品价值和有效利用资源为目的,寻求用最低的寿命周期成本,可靠地实现使用者所需功能,以获得最佳的综合效益的一种管理技术.价值尺度公式V(价值)=F(对象功能)/C(成本),说明价值与成本成反比,与功能成正比.价值工程是在20世纪初创立的全面质量管理中发展起来的,与一般的强调项目可行性的投资决策理论不同,是研究如何以最少的人力、物力、财力和时间获得必要的功能的技术经济分析方法,强调的是产品的功能分析和功能改进.

多热源环状管网热源位置的优化分析

多热源环状管网热源分布位置、热网结构、热负荷分布及密度等都影响到热网的造价和运行费用。本文以哈尔滨市开发区热网为背景,着重分析了多热源环状管网中热源位置变化时,对系统造价和运行费用的影响。基于开发区现有管网,提出了六种不同热源位置的方案,对每种方案利用已有程序分别进行了水力计算,以及造价和运行费用计算,从而提出对于多热源环状管网在条件允许时,应尽可能使热源均匀分布,以减少系统的造价和运行费用,不仅对环状管网的新建或改扩建工程有一定的借鉴意义,而且对枝状管网也有参考价值。

Microstructures and properties of Cu/Ag(Invar) composites fabricated by powder metallurgy

The Ag(Invar)composite powder prepared by ball milling was used to fabricate the Cu/Ag(Invar)composites.Microstructures and properties of the composites were studied after sintering and thermo-mechanical treatment.The results indicatethat during ball milling,micro-forging weld and work-hardening fracture result in that the average particle size of the Ag(Invar)powder increases rapidly at first,and then decreases sharply,finally tends to be constant.Compared with the Cu/Invar ones,thesinterability of the composites is greatly improved,resulting in that the pores in them are smaller in amount and size.After thethermo-mechanical treatment,the Cu/Ag(Invar)composites are nearly fully dense with the optimum phase composition and elementdistribution.More importantly,Cu and the Invar alloy in the composites distribute continuously in a three-dimensional(3D)networkstructure.Cu/Invar interface diffusion is effectively inhibited by the Ag barrier layer,leading to a great improvement of themechanical and thermal properties of the Cu/Ag(Invar)composites.

An Explicit Solution for Thermal Calculation and Synthesis of Super-structure Heat Exchanger Networks

For the optimal design of a heat exchanger network,the inlet and outlet stream temperatures of each heat exchanger in the network should be known.An explicit analytical solution of stream temperatures of an arbi-trary connected heat exchanger network was introduced,which is suitable for the thermal calculation of heat ex-changer networks.For the heat exchanger network synthesis,this solution was further developed and coupled with the stage-wise superstructure heat exchanger networks.The new calculation procedure reduced the computer mem-ory requirement dramatically.On the basis of this solution,a mathematical model for synthesis of heat exchanger networks with genetic algorithm was formulated,which is always feasible and no iteration is needed.Two examples were calculated with the proposed approach and better results were obtained.

Network Structure Expert System and Operation Optimization

It is proposed that double level programming technique may be adopted in synthesis strategy. Optimization of heat exchanger network structural configuration (the master problem) may be solved at the upper level, leaving the rest operating conditions( the slave problem) being optimized at the lower level. With the uniqueness in mind, an HEN synthesis expert system may be employed to address both the logical constraints and the global operation parameters′ optimization using enhanced sequential number optimization theory.Case studies demonstrate that the synthesis strategy proposed can effectively simplify both the problem solving and the synthesis process. The validity of the strategy recommended is evidenced by case studies′ results compared.

蒸汽管网数值模拟研究

建立了蒸汽管网模型,结合工程实例,验证了模型可满足工程精度要求。分析了蒸汽管网主管管径、调峰热源压力、热网结构对蒸汽质量损失率(凝结水沿程排放质量占供汽总质量的比例)的影响。