Accurately determining the resistance coefficient of a pipe network under operational conditions is a crucial step in constructing an accurate hydraulic model. In heating systems, the limited number of measurement points poses a challenge, as the identified resistance coefficient of each pipeline may be expected. A resistance coefficient identification scheme based on the Differential Evolution algorithm (DE) is proposed to address this. Through simulations of a real pipe network, it is observed that the resistance coefficients identified by DE exhibit an approximately normal distribution. Building upon this observation, the proposed scheme generates an optimal solution set through multiple runs of the DE. The final optimal solution is then deduced based on the characteristics of the normal distribution. An actual pipe network with 14 thermal inlets is employed to validate the scheme’s feasibility. It is found that the identification process can be terminated after 1088 runs of the DE. The absolute relative error between the calculated and observed flows remains below the impressive threshold of 1%. These results prove that the scheme can significantly improve the stability and uniqueness of the resistance coefficient identification results.
The hydraulic and thermal simulation methods of heating pipe networks are reviewed.The development process of steady-state hydraulic simula-tion solution,dynamic hydraulic simulation solution,steady-state thermal simulation solution,and dynamic thermal simulation solution is elaborated.The applica-tion and development trend of simulation in the back-ground of digital twins are analyzed.
The variation characteristics of daily natural gas supply are analyzed.The factors that affect the daily natural gas supply are selected.Through cor-relation analysis,it is determined that the main influen-cing factors of daily gas supply are:date type,daily minimum temperature,daily maximum temperature,daily average temperature,weather type,air quality in-dex,PM2.5 index,PM 10 index,daily average air pres-sure and daily average relative humidity.The variation law of daily natural gas supply under the influence of different influencing factors is discussed.The variation trend of daily gas supply is opposite to that of tempera-ture,and the daily gas supply is affected by tempera-ture in both sensitive and insensitive ranges.The influ-ence of daily average air pressure and daily average relative humidity on daily gas supply has a significant seasonal variation.The variation of daily gas supply is the same as that of daily average air pressure in spring and autumn,but it is opposite to that of daily average relative humidity in autumn and winter.The daily gas supply increases with the decrease in air quality.The daily gas supply has an increasing trend in snowy days,but a decreasing trend in blizzard days.The daily gas supply has a downward trend during statutory holidays,and the decrease increases with the extension of holiday time.
The characteristics of non-destructive testing technologies such as ultrasonic phased array,digital ray,ultrasonic guided wave and microwave,etc,as well as their application scenarios in urban gas pipe-lines are analyzed from the two perspectives of steel pipeline testing and PE pipeline testing.The testing effect of ultrasonic phased array and digital ray testing technology on PE electrofusion joints and heated-tool fusion joints is verified through experiments.The ultra-sonic phased array testing technology can be used for the detection of steel pipeline welds and PE pipeline electrofusion joints.It can effectively detect various de-fects in steel pipeline welds and PE pipeline electrofu-sion joints,and can detect metal and non-metallic in-clusion defects in PE pipeline heated-tool fusion joints.Digital ray testing technology can effectively detect va-rious defects in steel pipeline welds,as well as metal inclusion defects in PE pipeline electrofusion joints and heated-tool fusion joints.Ultrasonic guided wave tes-ting technology can quickly detect the defects of long distance steel pipelines,but it cannot effectively identi-fy defects in welds.Microwave technology can effec-tively detect defects such as incomplete fusion and in-clusions,etc,in PE heated-tool fusion joints,and the development of relevant standards will effectively pro-mote the use of microwave testing technology.
The determination of direct replace-ment parameters(replacement qualification standard,replacement pressure,replacement flow rate,replace-ment time and grounding resistance)is discussed.The selection of replacement release points is analyzed.The direct replacement process of urban natural gas pipe-lines(trunk pipeline,ring pipeline and branched pipe-line)is introduced.The safety precautions for direct replacement are summarized.
Micro-groove drag reduction technol-ogy is used in aerospace,pipeline transportation and sports.The relevant research of domestic and foreign scholars is summarized,the drag reduction mechanism of micro-groove drag reduction technology is intro-duced,and the research status is reviewed from the per-spectives of experiments and numerical simulations.The application of combined drag reduction and micro-groove drag reduction technology is introduced,and the research direction of micro-groove drag reduction tech-nology is prospected.
Five kinds of spoiler structures(V-shaped flange angle,V-shaped flange height,cylindrical flange hole diameter,angle between inverted V-shaped flange and horizontal direction,number of pressed con-vex hulls,each spoiler structural parameter has 4 lev-els)are selected,and the factor-level combination scheme is designed by orthogonal experimental meth-od.The flue gas side convective heat transfer coeffi-cient(evaluation of fin heat transfer capacity)and comprehensive performance evaluation factor(compre-hensive consideration of fin heat transfer capacity and resistance characteristics)of each scheme are simula-ted and calculated.The range method is used to deter-mine the main factors affecting the convective heat transfer coefficient on the flue gas side and the level combinations with the best comprehensive performance.The main factors affecting the heat transfer capacity of the fins are the number of pressed convex hulls,the V-shaped flange height,and the V-shaped flange angle.The secondary factors are the angle between the inverted V-shaped flange and the horizontal direction,and the cylindrical flange hole di-ameter.The level combinations with the best compre-hensive performance are V-shaped flange angle:Level 3,V-shaped flange height:Level 2,cylindrical flange hole diameter:Level 3,angle between inverted V-shaped flange and horizontal direction:Level 2,num-ber of pressed convex hulls:Level 4.The fin resist-ance and fin thermal efficiency of the best comprehen-sive performance scheme are 23.93 Pa and 90.42％respectively.
Based on the statistical data of gas accidents from 2019 to 2022,the characteristics of gas accidents are analyzed.The causes of user accidents and pipeline network accidents are analyzed,and pre-ventive measures are proposed.
Combining CiteSpace software with VOSviewer software,a statistical analysis is conducted on literature related to gas pipeline integrity manage-ment in both Chinese and English from CNKI and Web of Science databases.The key words co-occurrence network is formed,and the research hotspots at home and abroad are analyzed.The visual knowledge graph is drawn to obtain 7 domestic and 9 international hots-pot evolution paths.The development trend of future research is analyzed,and some suggestions are put for-ward for gas enterprises.The research on the integrity management of urban gas pipelines focuses on risk as-sessment and smart gas,etc.in China,while the inter-national research focuses on risk analysis,risk manage-ment,leak detection,failure probability,model re-search,etc.There are 7 hotspot evolution paths in do-mestic research,including gas pipeline network,risk assessment,integrity research,operational risk re-search,safety management research,evaluation method research,and comprehensive inspection research.There are 9 hotspot evolution paths in international re-search,including regional heating,sustainability,risk assessment,corrosion defects,urban areas,life cycle as-sessment,urban mining,modeling,and leakage diffu-sion.From the research path,it is found that the integ-rity management of gas pipelines needs to be strength-ened in data management,maintenance,and efficiency evaluation research.
Taking the solar air collector with vortex channel as the research object,the thermal per-formance and economy of five kinds of coated collectors are analyzed by simulation method.The research ob-jects are black nickel coating,black chromium coating,cobalt oxide black coating,cermet thin film coating and titanium oxynitride blue film coating.The effect of the coating on the thermal performance of the collector is relatively small,and the influence on the investment re-covery period of the collector is relatively obvious.The heat gain cost per unit air of five kinds of coated col-lectors is lower than the conventional electricity price.Considering the thermal performance and economy of the collector,the black nickel coating is the ideal choice.
The installed capacity and grid con-nection scale of wind power in northern China are con-stantly increasing,but the policy of"determining power by heat"during the heating period limits the flexible peak shaving of combined heat and power generation u-nits.While wasting a lot of energy,it also causes a cer-tain amount of wind abandonment,which is contrary to the"double carbon"strategic development goal.It is one of the effective ways to save energy and reduce car-bon emissions by using heat and power integrated peak-shaving technology to promote regional energy systems to achieve heat and power synergy and provide renew-able energy with grid space.The methods of integrated peak shaving,carbon emission reduction and renewable energy consumption promotion for combined heat and power generation units and the relevant current re-search status at home and abroad are reviewed.The modeling and optimization methods of heat and power integrated peak shaving schemes are discussed.The advantages,disadvantages and applicability of different schemes are analyzed and summarized.The matching heat and power integrated peak shaving schemes are put forward according to the energy characteristics of different regions.
Beidou high precision positioning technology and laser methane leakage detection tech-nology are integrated to establish the Beidou high pre-cision gas leakage detection system.The architecture,equipment and technical principle of the detection sys-tem are introduced,and the system performance testing and verification is conducted.The detection system has the advantages of high sensitivity,accuracy,efficiency and stability.
China's gas distributed energy has gone through three stages:the first stage,from 2010 to 2040,is the traditional gas distributed energy stage,with natural gas distributed energy as the main source.The second stage,from 2020 to 2050,is the low-carbon gas distributed energy stage,mainly consisting of re-newable energy and natural gas distributed energy.The third stage,from 2030 to 2060,is the zero carbon gas distributed energy stage,mainly consisting of hydrogen distributed energy and renewable energy.The energy development in various regions of China is uneven,and various stages and technological forms of gas distributed energy will coexist for a long time.
In view of the joint construction of the pressure isolation heating station and the relay pump station in long-distance heating network,the branch setting schemes of the relay pump station are analyzed.Combining engineering examples,the techni-cal economy of the schemes is compared.It is advisa-ble to use branch points to lead out in front of the relay pump station,which is technically and economically su-perior to branch points leading out behind the relay pump station.
在Matlab中搭建变风量空调系统自动控制程序,在DeST软件中对建筑进行建模,将计算得到的房间自然室温、建筑热特性系数作为自动控制程序的输入参数,进行房间温度、送风参数、空调负荷、设备能耗计算.结合案例,对典型房间室内温度、空调冷负荷、送风量、空调箱风机耗电功率进行模拟分析.室内温度、空调冷负荷、送风量、空调箱风机耗电功率变化趋势基本一致,变风量空调系统自动控制程序调节效果良好.空调箱风机平均耗电功率为0.26 kW,与采用定风量空调系统相比,变风量空调系统可节省约44.6％的空调箱风机能耗.
针对集装箱建筑供暖、生活热水需求,以热负荷自给自足为目标,搭建离网式PV/T集热器联合空气源热泵供热系统(简称联合供热系统).以单个集装箱房为例,限定联合供热系统发电量不满足耗电量时间,采用Hooke-Jeeves算法,以最小费用年值为目标,对联合供热系统配置进行优化.优化后联合供热系统发电量不满足耗电量的时间37.9 h,可基本实现热负荷自给自足.优化后,主要设备容量保持不变或有不同程度降低,各项系统性能指标合理.与优化前相比,费用年值减少12.2％.
为了加强工业生产安全事故的预警,定量评价事故风险,以国内651起工业生产安全事故为研究对象,建立了工业生产安全事故蝴蝶结模型.根据贝叶斯网络工业生产安全事故风险评估模型预测事故计算概率.首先,计算各节点事件的条件概率,通过软件Genie3.0构建模型并计算,得到国内工业生产安全事故发生的计算概率为12.50％.其次,通过模型诊断得到导致事故发生的主要原因,生产或维修过程人为错误B1和工业生产过程故障B2是主要原因,其中违章操作C1是导致生产或维修过程中人为错误B1的主要原因,工艺条件不畅C5是导致工业生产过程故障B2的主要原因.
为有效提高城镇燃气管网的抗震性能与安全运行能力,从易损性理论出发,结合国内外相关标准,分析城镇燃气管网震害失效影响因素.通过构建地震影响失效、管道腐蚀或老化失效、管道设计失效、管道施工失效、第三方损伤失效、误操作失效故障树,梳理管道震害事故之间的逻辑关系,建立城镇燃气管网地震易损性评估指标体系.应用序关系法,计算指标体系中的指标权重,形成完整的评估体系.给出城镇燃气管网地震易损性值计算方法,结合相对易损性值区间,评定城镇燃气管网地震易损性等级.
高层、超高层建筑燃气管道受热膨胀、不均匀沉降、风荷载、地震荷载的影响大,对高层、超高层建筑燃气管道应力控制措施进行研究.推荐在补偿器安装时进行温度修正,考虑安装温度的影响.引入管竖直出地面处、引入管与立管水平连接处、水平管跨越建筑物之间的沉降缝处,均为燃气管道受沉降影响最大的位置.中低压引入管埋地部分推荐采用PE管,在引入管的水平段上设置柔性连接管.室外水平燃气管道不应穿过建筑物的沉降缝(或伸缩缝、抗震缝等),尽量避免跨越建筑物设缝的位置.管道抗风与抗震方面,应保证管道稳管体系的有效性,使管道能够与建筑物墙体牢固连接,在受迫振动时达到协同变形.考虑采用抗震性能更优的不锈钢管道材料.
