热水供暖系统质量-流量调节流量优化系数的研究

质量-流量调节是热水供暖系统进行供暖调节的一种重要的方法,这种方法的突出优点在于在供暖调节的过程中不仅热网的供水温度随热负荷的减小而降低,同时热网的流量也随热负荷的减小而减小,这样可以大大节省热网循环水泵的电能消耗;但是为了防止水力失调,对直接连接的供暖用户,进入系统的流量不能太少,因此研究质量-流量调节过程中流量和热负荷的关系即流量优化系数十分必要。本论文通过分析给出了流量优化系数的取值范围,同时给出了与流量优化系数相对应的热网供回水温度的函数表达式。     

变流量运行供热系统流量调节下限分析

通过仿真模拟计算和试验,分析变流量运行供热系统进行水力工况分析时摩擦阻力系数公式的选取,建议选用湍流综合公式。以某市供热管网为例,分析变流量运行供热系统的流量运行下限。初调节后热用户水力失调度相差较小时,系统流量调节下限为9%;初调节后热用户水力失调度相差较大时,系统流量调节下限为27%。     

定流量与变流量系统冷水温度节能控制策略

分析了冷水温度对冷水机组COP的影响.讨论了定流量系统和采用变压差阀位控制的变流量系统的冷水温度调节和节能控制的最佳运行策略.     

质量—流量调节的模拟应用

主要针对质量—流量调节的原理及理论计算进行了分析,运用TRNSYS建立了模型,并进行了模拟计算,同时与变频调节的模拟结果作了分析对比,得出了质量—流量调节的节能性。     

计量供热系统变流量影响因素分析

基于对某分户计量供热小区变流量测试结果和住户调阀模式调查结果,分析了计量供热系统流量变化的主要影响因素.研究发现,开窗是恒温阀自动调节个体流量波动的最主要因素;住户频繁调节及长周期调节分别带来个体流量的短期阶跃变化和长周期变化;耦合作用使住户个体流量受其他住户调节行为影响,并削弱个体调节对整体流量变化的影响;同时发生率关系到个体流量变化对整体流量变化的综合影响.对该小区进行了流量变化概算,结果与测试结果较一致.     

区域供热分阶段改变流量水温调节

目前大型区域供热系统均是间接连接方式,其运行调节大都采用分阶段改变流量的质调节。进行水温调节的计算和绘出水温调节曲线是设计工作必不可少的一环。对此本文作如下讨论: 一、热网与用户直接连接的水温调节 分阶段改变流量的质调节,是在供暖期中按室外温度高低分成几个阶段。在室外温度较低的阶段中保持较大的流量,而在室外     

变流量间接供热系统的调节

通过分析变流量供热系统的特点，探讨了相应的供热调节方式。推导了一、二次网侧供回水温度及相对流量的调节公式，并结合算例给出了相应的曲线，就供热参数的控制进行了讨论。     

调压器流量系数实用性的实验研究

流量系数作为燃气调压器的一个重要参数,用来衡量燃气调压器的流通能力。流量系数是在燃气调压器调节元件处于最大开度位置时得到的,实际运行时调节元件并未处于最大开度。本文在了解流量系数由来的基础上,对流量系数的实用性进行了简要的分析,并通过实验对两种作用方式燃气调压器流量系数的实用性进行了比较,得到流量系数对间接作用式燃气调压器的选择更具有指导作用的结论。     

浅析供暖系统分阶段质调节流量比

本文从节能角度出发,对供暖系统采用分阶段变流量质调节进行了优化运行分析,确定其最佳流量比的计算方法。     

供暖系统定流量三通调节阀的应用研究

针对供暖系统的动态调节问题，提出三通调节阀的定流量调节形式。推导出支路定流量调节所满足的阻力关系式，测试了现有三通调节阀的阻力特性，分析了定流量三通阀的特征曲线。认为现有三通调节阀不能完全实现定流量的目的，最大流量偏差为27％，所得到的定流量调节特征曲线符合实际情况。     

An analysis of compartment fire doorway flows

A mathematical study is made to compute the doorway flow behavior due to fire in a room. Two approaches were taken, first a model attempting to include the effect of fire entrainment and vent mixing; second was a model based on an ideal point source plume fire—both in the zone model concept. Limiting analytic results were found for the latter to give insight into the physics. The results were compared to available flow data, and an approximate formula was developed to predict the doorway mass flow rate to within 20% for a wide range of fire conditions. CFD computations were also explored using FDS. Results are compared from FDS and the zone model with experimental data for a wide range of variables.     

Characterization of two-phase flow in a single rock joint

An experimental study using a triaxial apparatus was used to analyze the two-phase flow patterns in jointed rock specimens. Rock specimens having a single natural fracture were tested for two-phase flow of water and air. Triaxial tests were conducted to characterize the two-phase flow through fractured granite specimens at low confining pressures. It was found that for a relatively smooth joint (JRC<6), bubble flow pattern occurred within the rock joint when the gas velocity is below 15 m/s. The average velocity of water usually varied between 0.1 and 0.5 m/s for bubble flow patterns. In this velocity range, air bubbles were able to form along the joint walls or to be randomly displaced within the water phase. When the gas velocity inside the rock joint exceeded 22 m/s, the flow patterns took annular form for non-zero capillary pressures (i.e., injected gas pressure is not equal to injected water pressure). At elevated (>0.25 MPa) gas injection pressures, the gas occupied the main part of the fracture and the liquid was able to flow as an unstable film forming an annular flow along the joint. When the annular flow developed, the mixture flow pattern was independent of the air flow velocity. This was due to the fact that once the injected air velocity reached a critical value (i.e., 20 m/s), water velocity inside the joint was negligible for a given confining pressure and injected water pressure. Further increase in inlet air pressures developed a single-phase air flow with no water flow.     

Evaluation of low flow estimation techniques for ungauged catchments

Low flow indices are of interest for a number of water‐related applications. Conventionally, low flow indices are derived from continuous streamflow data; however, these data may not always be available for analysis. A number of techniques have therefore been developed for low flow estimation in ungauged catchments. These approaches vary in complexity and in the amount of initial data required to generate the low flow model. In the UK, software is available which assists in low flow estimation for ungauged catchments. However, certain desktop studies only require a simple evaluation of low flows, with specific low flow indices, such as the Q₉₅ index, being of interest. In this case, the use of such software may not be justified or required in the first instance. This paper demonstrates that a simple regression model is adequate for low flow estimation for multisite analysis where the order magnitude of the low flow index is of importance.     

供热系统中调节阀的研究与应用

依据调节阀流量特性的数学方程，导出了流量特性分别为直线型和等百分比型调节阀流通截面积的计算公式，指出了现有调节阀阀芯形状设计中存在的问题，分析了供热系统中调节阀的选用原则，认为应根据流通能力来计算选择调节阀的口径，而不是由连接管的管径来确定，并认为调节阀的安装地点不同，其计算公式中的系数有差别。     

工作流设计案例分析——房产管理系统中的工作流设计

工作流的设计概念应用到软件系统中,将工作过程分解成任务、角色,按照一定的规则来执行这些任务并对它们进行监控,可以提高办事效率、降低房产管理成本,提升企业经营管理水平和企业市场竞争力。房产管理系统中借鉴工作流的概念,可有效地提高管理人员的技术水平。     

虹口港、杨浦港地区旱流污水截流工程设计水量的论证

对虹口港、杨浦港地区近几年来产业结构调整 ,污染大户的外迁 ,工业废水量明显减少的情况进行调研 ,通过对现状污水量的采集 ,规划、现状水量的测定等进行了详细的分析和论述 ,比较客观合理确定虹口港、杨浦港地区旱流污水截流工程的设计污水量     

剧院舞台的防烟空气幕

通过对火灾烟气发生量及烟气流场的分析，建立了舞台空气幕计算的数学模型并求数值解。提出利用空气幕控制火灾烟气扩散的方法，以达到安全疏散观众的目的。     

数值模拟在泥石流流量计算中的应用

通过比对现有《铁路工程地质手册》中提供的经验型泥石流流量计算公式,将数值模拟技术应用于泥石流流量计算之中,引入更多流量控制影响因子,并针对泥石流的物质组成提出不同模拟计算方法,以便更接近实际地反映泥石流流量的真实状况,为泥石流的定性定量以及后续计算提出了一点建议。     

大比降高速水流排水管水力计算

大比降排水管水流通常为高速水流,其水力设计已经超过排水设计规范范畴。以实际工程为例,指出该类管道不宜按照有压管路或明渠均匀流计算公式进行水力计算,应按照掺气水流计算,这为实际工程设计提供了参考依据。     

On the fundamental equations of water hammer

The wide spectrum of practical problems that warrant water-hammer modelling has increased the importance of careful formulation of the fundamental equations of water hammer and critical analysis of their assumptions. To this end, this paper reviews the relation between state equations and wave speeds in single as well as multiphase and multicomponent transient flows, formulates the various forms of one- and two-dimensional water-hammer equations and illuminates the assumptions inherent in these equations. The derivation of the one- and two-dimensional water-hammer equations proceeds from the three-dimensional Navier?-?Stokes equations for a compressible fluid. The governing equations for turbulent water-hammer flows are obtained by applying ensemble averaging to the simplified form of the Navier?-?Stokes equations for water-hammer problems. Unlike time averaging, ensemble averaging is applicable to unsteady flows where the time scale of the transient is often much smaller than the time scales of the turbulence. Order of magnitude analysis, physical understanding and recent research findings are used throughout the paper to evaluate the accuracy of the assumptions made in the derivation of the one- and two-dimensional water-hammer equations.