Discussion on Direction of Circular Flow of Reversed Return Hot Water System

Aiming at the central mechanical circulated hot water supply system recommended by the current code, the criteria of water flow direction in the pipes of transport and distribution is brought forward based on the hydraulic principle, followed by the analysing with charts of flow directions in the reversed return hot water system consisting of two, three and several vertical pipes in the working conditions of simple return and a little water distributing. There are several directions of circular flow, the only working condition of simple return and single water flow direction which applied in current hydraulic calculation of reversed return hot water supply system is incomplete, certain hydraulic precondition is necessary to ensure circular flow flowing in each vertical pipe as the assumed direction in the course of hydraulic calculation.     

GSM/GPRS Based Leakage Monitoring and Locating System of Tap Water Pipe Network in City Area

On the underground booster and leakage of the city water network pipe,a remote leakage monitoring and locating system based on GSM/GPRS is developed .The parameters of tap water pipe network ,i.e., flow, velocity, direction and pressure are collected by monitor terminal ,the data transmission is realized by GSM/GPRS network .Aiming at the feature of the underground booster and leakage of the water pipe, with the GIS technology and the signal processing methods ,such as negative P wave and flow detecting, accurate and prompt positioning of leakage location can be detected. The system can not only realize the leakage detection of low cost, city area, networking by GPRS network but also provide a emergency platform of tap water pipe network .The system has been used in practical tap water pipe network with excellent results.     

Selection and Construction of New Types of Water Supply Pipings

To overcome the disadvantages of traditional galvanized pipe, new types of water supply piping materials have been developed. Comparison and classification are made based on their characteristics such as thermal stability, resistance to pressure, expansion coefficient and thermal conductivity, resistance to water hammer, cost and easiness of installation. Furthermore, the characteristics were discussed according to their locations in buildings: distribution main line in each pressure zone, branch pipe in water closet and the main line. Finally, the conclusion about the principles for pipe selection according to its location in buildings is given.     

变流量冷冻水系统温差控制法的适用性

研究了末端设置通断控制阀的一次泵变流量系统在温差控制下的水力特性,并结合风机盘管与房间的非线性换热耦合特性,进一步探讨了温差控制的适用条件以及变温差控制温差值的设定方法。结果表明：末端设置通断控制阀的系统,当管网整体负荷分布均匀且各开启用户的负荷变化规律相近时,温差控制同样是较为适用的,此时系统的水力失调对室内温湿度的影响较小;采用变温差控制时,仅以不同的总负荷率分段设置温差值,并不能获得良好的室内温湿度控制效果,建议以优先保证风盘除湿能力和室内干球温度为原则设定温差值,相比于目前的方法,在同等的室内相对湿度波动下,室内温度的稳定性可以得到保证。     

Experimental Analysis on Power Consumption of Chilled Water Pump by Constant Pressure Difference Method with Bypass Valve

The power consumption of frequency conversion chilled water pump of an office building regulated by constant pressure difference method with bypass valve is studied experimentally. A model of power consumption of chilled water pump is proposed. The effects of pressure difference set point of bypass valve on instantaneous and annual power consumption of chilled water pump are analyzed. The simulation results are validated experimentally, which shows that there is a maximum water flow rate which increases with the increase of the pressure difference set point of bypass valve at equilibrium state. There are three pressure operation regions of the bypass valve: under pressure region, constant pressure region and over pressure region. The power consumption of frequency conversion chilled water pump is affected by the pressure difference set point of bypass valve significantly, and it would be minimized as the pressure difference set point of bypass valve is equal to the pressure difference between supply water and return water of the farthest user.     

Experimental and Theoretic Research on Unfree Inundation Water Efflux Flow Field and Circular Field in Rock Salt Well Water-Mining

Simulative experimental research and theoretic analysis on the characteristics of unfree inundation water-flow field and circular field in rock salt well water-mining have been done by glass equipment.The tracer particles spirally circumferentially ascend from bottom to stoma in the triangle vase flow field during the process of unfree inundation efflux flow by positive-cycle pouring water,and the tracer particles fast move up and down in the columnar flow field(jar) as the spouting interval,height of columnar flow field and diameter of the tracer particles are less.While contrary-circular pouring water is done,the water location of centric pipe flow water for the triangle vase is tangential with the down of telescopic pipe and steadily maintains the state.For the columnar flow field,water location is higher than the down of telescopic pipe while the circulation field is just formed and gradually drops until it is tangent with the down of centric pipe.Theory analysis and calculation show that the tracer particles spirally ascend owing to the competition between the up return rate(V_H) and the axial rate(V_m).The fanning orientation of pasting line is the vector sum between V_H and V_m.     

Nonlinear Characteristic Modeling of Servo Value on Hydraulic Bending Roll System''s Dynamic Characteristic

Nonlinear characteristic of servo value is the important factor influencing hydraulic system, the model of electro-hydraulic servo pressure control system is designed. In this model, flux-equation of servo valve is specially applied and some non-linear characteristics are considered. Furthermore, SIMULINK toolbox of MATLAB language software is applied to solve mathematic model and simulation curves of some variables are obtained. The calculation results are in good agreement with the experimental results.     

Analysis of a New Distributed-Pump Scheme Applied in District Heating Network

It is helpful for energy efftciency to use distributed pumps instead of valves to regulate hydraulic balance in a district heating system (DHS). A new scheme of distributed pump-system is presented based on performance comparison of hydraulic regime and power saving of single-heat-source dendritic pipeline networks with regulating valves and/or distributed pumps. Supposing that the new scheme was employed in multi-sources looped-pipe network, theoretical analysis and case study were carried out to evaluate off-design performances including hydraulic self-regulation, supply water temperature stability and power-saving potential. The results indicated that the proposed scheme would contribute to minimizing power consumption, retarding water temperature change, and would be convenient to adjust the quality and quantity independently in the looped-pipe heat supply networks.     

A Study Transient on Predictive Calculation Method of on Underground Ventilation Network

The authors developed a computer program of transient predictive calculation method on underground ventilation network. The program approximated a field data set of seasonal cyclic changes of air Temperature and humidity at the inlet to the sine curves, and included sensible heat conduction from rock to air current. The temperature of rock around and airway was calculated by finite difference method. The prediction method can be used to calculate the variation of flow rates, temperatures and humidities of air flow in the airways along underground network.     

Load dynamic matching of supply and demand side based on the utilization of urban sewage heat energy

Flowing dynamic characteristics and its temperature dynamic characteristics of a three-level sewage pipe network in Chongqing were analyzed. A mall's building whole year load was simulated. In the adverse condition of wastewater flow, the market construction peak discharge heat was compared with the sewage heat load, the balance between the most adverse flow and the building demand was found. Explored supply and demand matching method between urban sewage and city building load in flow adverse condition to take full advantage of the urban sewage cold and hot resources. the composite system was adeptcd to make up the most unfavorable flow time of sewage average heat load and the construction load difference; it also puts forward principle of load sharing and control strategy aimed at compound system.     

Discussion on the Hydraulic Calculation Method of Loop Heating Pipe Network

The authors definitely make out the concept of loop main pipeline, supplying main pipeline and ramiform branch line, as well as the order of their hydraulic calculation. Then they puts forward the principia of how to study out the direction of loop main pipeline and presents the method of making flux initial distribution. The matrix of loop main pipeline hydraulic square dispersion is set up. The node referenced pressure is defined and the equation of how to calculate it is deduced. A software is developed to calculate the loop main pipeline hydraulic square dispersion. The method of calculating ramiform branch margin impetus is given.     

Research on Reliability of Water Delivery Pipeline System

In this paper,the reliability calculation models of water delivery pipeline system with setting up communicating tubes are studied by net decomposition method.The calculation results show that the reliability of water delivery pipeline system may be lowered or increased with increment of the communicating tube number,and the influence of reliability variety of tubulation of delivery main pipeline and T branch pipe is a sensitive factor influencing the reliability of the system.Therefore,the research results have the important leading meaning to the design,the choice of subassembly,the construction installation,maintenance management of the water delivery pipeline system,and looking for path with the biggest reliability of the system.     

THE COMPREHENSIVE HYDRAULIC TESTING SET WITH A LOAD SENSING SYSTEM

This paper introduces the comprehensive hydraulic testing set for many kinds of hydraulic elements with hydraulic drive, hydraulic regulation and hydraulic loading. It has rational structure compact arrangement, reliable characteristics and advanced technique. In order to reduce the energy loss in the hydraulic system of the testing set, 1 ad sensing control is used. The static and dynamic characteristics of the load sensing system are analysed with the method of numeral simulation on computer. the testing witk load sensing control results show energy may be saved obviously and the heat load in hydraulic system may be reduced effectively, then testing quality is improved and the volume cf oil case is lessened. The lead sensing valve design is satisfied with simplifying structure so that it may be used reliably for the fixed flow hydraulic system of the testing set or other machines.     

Development and Investigation on Duty Valve Drived Hydraulic Brake Servo System

A duty valve drove hydraulic brake servo system of HEV(hybrid electric vehicle) power transmission test rig is studied.The brake performance depends on the responses of the pressure control.A PI controller is designed through analyzing the working characterizes of the hydraulic brake system and duty valve by using rapid control prototype(RCP) tool-dSPACE,all the model and control code are successfully download to the AutoBox,and rapid control prototype experiment shows that the benefits of developing duty valve drove hydraulic brake servo system with good performance has been achieved.     

丘陵地区特色经济作物喷灌技术应用研究

在丘陵地区推广喷灌技术应用于经济作物灌溉,有利于中国节水农业的稳步发展和欠发达地区的农业结构调整。笔者针对中国丘陵地区自然特点和面临的水资源短缺严峻状况,通过分析总结国内外喷灌技术和设备的发展特点和经验基础,阐述了喷灌在中国丘陵地区经济作物的应用研究进展,提出了中国丘陵地区经济作物喷灌技术设计要点和发展方向建议。喷灌技术在丘陵地区应用前景广阔,形成适宜丘陵地区的集动力设备、压力流量调节管网、低压喷头、水肥一体化装置和智能控制设备于一体的喷灌系统是喷灌技术在丘陵地区应用和发展的趋势。     

插装式电液比例流量放大阀特性分析

插装阀具有通流量大、结构简单和成本低等优点,广泛应用于液压系统中。笔者针对一种主级基于流量放大原理、先导级采用单级伺服比例方向阀的两级插装比例节流阀特性进行分析,建立了该比例节流阀的简化数学模型,获得了简化条件下的特性关系式。以此为基础,在SimulationX软件环境中建立该液压阀的仿真模型,利用实验数据对模型正确性进行验证,运用验证后的仿真模型对比例阀性能特性进行分析。结果表明：该液压阀输出流量静态特性存在死区,阶跃响应存在时间滞后,主阀流量放大倍数并不是常数,性能影响因素与主阀反馈槽预开量、面积梯度、级间过渡容腔体积以及先导阀通流能力等相关。     

Selection of Hot Water Circulating Pump Related Parameters

In multistoried or the high-rise civil constructions the full-time machinery hot water circulation supply system design,whether the design parameters for the flow and the lift of circulating pump are appropriate or not,will be related to continuously,safe,stably running of the hot water supply system.This paper introduces parameter selections of hot water circulating pump both at home and abroad.Based on the difference of these selection means it analyzes the calculating means of the flow and the lift of circulating pump.Whether the circulator flow should join the additional circulating flow or not is the focal point in the argument.In China's present "Code for design of building water supply and drainage" the additional circulating flow is considered not flowing through the circulating pump,so in calculation the additional circulating flow does not contain the circulator flow.By analysis of the water distribution operating mode and various ring circuits difference,as well as considering that for the very small circulator flow it is more difficult to use the valve regulation and to achieve balance between various ring circuits resistance loss,inaccessible absolute circulation in the same regulation,short circuit and so on,the circulator flow should be the sum of circulating flow and additional circulating flow.To calculate lift head the additional circulating flow should be considered through the calculating loop.     

THE OPTIMAL DESIGN AND ENGINEERING APPLICATION OF DISTRIBUTION

This paper introduces the metod of optimal design of municipal water distribution,The main points are the theory,mathematical model,program frame figure and example in practice of the optimal method of hydraulics.The program is applicable to the design and calculation of the pipe network in a city. It gives a simple and convenient calculation method for multiple-scheme design and scheme cmparison of water supply system.     

Numerical Simulation on Drying Characteristics of a Combined Microwave-convection Process

Combined microwave-convection drying characteristics are investigated by numerical simulation. Combined microwave-convection drying has advantage of swift drying and sterilization. Based on qualitative analyses on the mechanism of combined microwave-convection drying, the differential equations are established and the numerical simulation method is described. The humidity, vapor pressure and temperature, along the radius in a spherical pill, are calculated by the numerical simulation during drying process. The calculation results show the relationship between humidity, vapor pressure, temperature and drying time, and that drying process is greatly influenced by input microwave power. The calculation results are good consistent with the experimental datum.