Abstracts and Key Words

Heat-supplyNetwork，Cooling-supplyNetworkandSubstationSimulationCalculationofLocalResistanceCoefficientofConfluenceTeewithLargerPipeDiameterCHEN Youqian，CUI Xuyang，YANG Di， LEI Wanning，HUANG Tao，BAI Chao， GAO Lin，YANG Junhong

Abstract： The Fluent software is used to analyze the effects of Reynolds number of main pipe，split ratio (mass flow ratio of side branch pipe to main pipe)，pipe diameter ratio (internal diameter ratio of side branch pipe to main pipe)，intersection angle (angle between side branch pipe and straight branch pipe) on local resistance coefficient of confluence tee and fluid velocity field in the tee. The research objects are the local resistance coefficient (called resistance coefficient 1) between the side branch pipe and the main pipe of DN 400 mm and above equal diameter and reducing tee，and the local resistance coefficient (called resistance coefficient 2) between the straight branch pipe and the main pipe. The variation range of Reynolds number of main pipe is 2×105to 106(the water velocity range of corresponding main pipe is 0.5 to 2.5 m/s)，the variation range of split ratio is 0.2 to 1.0，the variation range of pipe diameter ratio is 0.38 to 1.00，and the variation range of intersection angle is 30° to 90°. The influence of Reynolds number of main pipe: when the split ratio is constant，and the Reynolds number of main pipe is greater than 4×105，the resistance coefficients 1 and 2 basically do not change with the increase of Reynolds number of main pipe，that is，the local resistance coefficient enters the resistance square area. When the Reynolds number of main pipe is constant，the larger the split ratio is，the larger the resistance coefficients 1 and 2 are. When the split ratio is relatively large，especially when the split ratio is 1.0，a low-speed reflux area of large range appears in the upper part of the main pipe，and an obvious velocity gradient appears in the main pipe. The influence of pipe diameter ratio: when the split ratio is constant，the resistance coefficients 1 and 2 decrease with the increase of pipe diameter ratio. The larger the pipe diameter ratio is，the smaller the decrease in the resistance coefficients 1 and 2 is. When the pipe diameter ratio is greater than 0.8，the influence on the two is no longer significant. The smaller the split ratio is，the smaller the influence of the pipe diameter ratio is. When the pipe diameter ratio is 0.38，the water velocity in the oblique branch pipe is relatively high，and the water velocity distribution in the tee is very uneven. The larger the diameter ratio，the more uniform the pipe diameters of the straight branch，the oblique branch，and the main pipe，and the more uniform the velocity distribution，and the low-speed return area at the upper part of main pipe has also been reduced.. The influence of intersection angle: when the split ratio is constant，the resistance coefficients 1 and 2 increase with the increase of intersection angle. With the increase of the intersection angle，the low-speed reflux area in the upper part of the main pipe increases，and a significant speed gradient appears.

Keywords: confluence tee; local resistance coefficient; velocity field; numerical simulation

BuildingHeating，AirConditioning，VentilationandThermalEnvironmentEffectofFinArrangementonMeltingofPhaseChangeMaterialinRectangularCavityCHENG Suya，CHEN Baoming， GUO Mengxue，ZHANG Yanyong，LI Jiayang

Abstract： The rectangular cavity filled with paraffin (divided into a rectangular cavity without fins and a rectangular cavity with fins) was used as the research object to establish a mathematical model. The finite element software COMSOL Multiphysics was used to simulate the melting behavior of paraffin in the rectangular cavity，and the influence of different fin arrangements on the melting behavior of paraffin was analyzed，so as to screen the fin arrangement that help enhance the paraffin melting. The right wall of the rectangular cavity is the heating surface，and the other three walls are adiabatic surfaces. The fins of the rectangular cavity with fins are arranged inside the heating surface. On the premise that the number of fins (3 fins) and the same interval，the total length of fins in the rectangular cavity remains unchanged，and four fin arrangement modes are set. Arrangement mode 1: The length of each fin is 32 mm. Arrangement 2 mode: The lengths of the bottom-up fins are 41，32 and 23 mm，respectively. Arrangement 3 mode: The lengths of the bottom-up fins are 23，32 and 41 mm，respectively. Arrangement 4 mode: The lengths of the bottom-up fins are 29，38 and 29 mm，respectively. For the rectangular cavity without fins，under the action of natural convection heat transfer，the paraffin in the upper right corner melts first，then the melted part diffuses to the center of the rectangular cavity until the paraffin in the lower left corner of the rectangular cavity completely melts. Adding fins in rectangular cavity can improve the melting uniformity of paraffin and shorten the melting time of paraffin in rectangular cavity. The arrangement mode 2 has the best effect on improving the melting uniformity of paraffin in the rectangular cavity，and the time of complete melting of paraffin is the shortest. Under the same heating time，the liquid phase area ratio (ratio of liquid phase paraffin area to rectangle area) of paraffin in the rectangular cavity with fins is significantly higher than that in the rectangular cavity without fins. The heating time of paraffin in the rectangular cavity without fins is 3 522 s，and the heating times of paraffin in rectangular cavity with fins arranged in 1 to 4 are 1 874，1 674，2 082 and 1 910 s，respectively. The effect of the other three fin arrangement modes on the enhancement of paraffin melting in the rectangular cavity is evaluated with the equal-length fin arrangement mode 1 as the reference. Fin arrangement 2 has obvious enhancement effect on paraffin melting in rectangular cavity，and the enhancement effect is concentrated in the middle and later stage of melting process. Arrangement modes 3 and 4 play the opposite role.

Keywords: rectangular cavity; paraffin phase change heat storage; equal-length fin; non-equal fin; melting

InvestigationonRuralAir-sourceHeatPumpUsersinHebeiProvinceMA Kunru，LI Xuefeng，LI Siqi

Abstract： For the pilot users (total of 412 households) of coal-to-electricity conversion in Shijiazhuang and Baoding rural areas (newly added air-source heat pump hot water units to prepare hot water，using original indoor radiators and pipes of rural users to realize heating)，the thermal habits，modification effects，and user satisfaction of rural users after the coal-to-electricity conversion were investigated，and the economic and environmental protection analysis of coal-to-electricity conversion was carried out. For the thermal habits: because the air source heat pump can be started and stopped flexibly by the user according to the comfort requirements，whether there is anyone in the home，the number of users using 24 h a day heating is declined. Most of the users who do not use auxiliary heating methods are relatively rich in economic conditions. When configuring air-source heat pumps，they have the economic ability to choose units with relatively high heating power，and their ability to cope with severe cold periods is relatively strong. Among the users who use auxiliary heating，the household conditions of users who use bulk coal and fuel wood are the least desirable. For the modification effect and satisfaction degree: the indoor temperature is 13 to 16 ℃ before the coal-to-electricity conversion，and the indoor temperature reaches 17 to 20 ℃ after the coal-to-electricity conversion，the indoor comfort is significantly improved. During the heating period，11 households reported air source heat pumps for repair，accounting for only 2.67% of the total users. 71.1% of users are very satisfied with the heating effect，and 22.1% are satisfied with it. The main reason for unsatisfactory heating effect is that it is difficult to achieve balance between heating effect and heating electricity bill. For economy and environmental protection: not only the purchase cost of air-source heat pump is favorable to rural users，but also the heating cost is greatly reduced on the basis of effectively improving the heating effect. The emission reduction effect of coal-to-electricity conversion is very obvious，if considering the centralized and efficient flue gas treatment in power plant，the emission reduction effect is more remarkable.

Keywords: rural clean heating; air-source heat pump; coal-to-electricity conversion

RenewableEnergyDistributedEnergySourceandCombinedCooling，HeatingandPowerPerformanceComparisonofMCCHPSystemandInfluenceofLoadVariationunderWinterandSummerConditionsQU Ying，WEI Fan，WANG Xiaoming

Abstract： Aiming at the performance characteristics of the MCCHP system，a system based on gas combustion engine and a dual-effect lithium bromide absorption heat pump was built，and the system model was established. Through mathematical simulation，the system performance of cold water backwater temperature in summer working condition，hot water backwater temperature in winter working condition，internal combustion engine speed and internal combustion engine load rate change is analyzed. The results show that the performance of the MCCHP system under the summer condition is higher than that under the winter condition，and the COP of the system under the summer condition is 2.2 times that under the winter condition. The reduction of the user hot and cold load and the reduction of the gas engine speed will cause the COP of the system to decrease，and the reduction range of the COP of the system is greater than the primary energy utilization rate. The low load rate operation of the gas combustion engine will cause the COP of the system to decrease，and the primary energy utilization rate is also slightly decreased.

Keywords: micro distributed system; MCCHP system; primary energy utilization rate; COP; variable condition

ComparisonofOrganicRankineCycleWorkingFluidsofMediumTemperatureWasteHeatSourceZHANG Jianliang

Abstract： Based on the calculation model of Levelized Electricity Costs (LEC)，the subcritical cycle，supercritical cycle thermal efficiency and LEC of 7 working fluids (2-methylbutane，dichlorofluoroethane，acetone，n-heptane，benzene，octane and toluene) were investigated by the example，and the applicability of working fluids to organic Rankine cycle of medium temperature waste heat source was evaluated considering the environmental protection and safety of working fluids. The thermal efficiency of the subcritical cycle of the 7 working fluids increases with the increase of evaporation temperature，while the LEC decreases with the increase of evaporation temperature. The maximum thermal efficiency of supercritical cycle of 7 working fluids is higher than that of subcritical cycle，and the LEC is lower than that of subcritical cycle. The comprehensive performance of supercritical cycle is better than that of inlet pressure of 6.0 MPa under the condition that the inlet pressure of the expander is 5.5 MPa. Regardless of subcritical cycle or supercritical cycle，benzene and toluene show the best comprehensive performance in terms of thermal efficiency and LEC，and the comprehensive performance of dichlorofluoroethane is in the middle. Although the toxicity of benzene and toluene is low，but the flammability is high，there is a greater risk in the engineering application，which puts forward higher requirements for the sealing of pipes and equipment. Dichlorofluoroethane is not only environmentally friendly，but also has low toxicity and does not spread flame. At this stage，it is suitable as an organic Rankine cycle working fluid of medium temperature waste heat source.

Keywords: medium temperature waste heat source; organic Rankine cycle; subcritical cycle; supercritical cycle; working fluid

ReviewandProspectofNaturalGasDistributedEnergyDevelopmentinShanghaiGUO Jiasheng

Abstract： The development of natural gas distributed energy started earlier in Shanghai，and is at the leading level in China. The natural gas distributed energy projects that have been completed and under construction in Shanghai from 1999 to 2019 are sorted out，and analyzed from the perspectives of operation time，operation status，prime mover types，application scenarios and geographical distribution. The policy path of distributed energy development is summarized，and the natural gas utilization history of Shanghai is introduced. Suggestions for the follow-up projects are made from the aspects of energy price impact，technical equipment upgrading，productization of engineering projects，operation management specialization and continuous optimization of business environment. The development trend of natural gas distributed energy is prospected.

Keywords: Shanghai; natural gas distributed energy; policy pathway

GasCombustion，GasAppliancesandGasConsumptionEquipmentEffectofExcessAirCoefficientandArrangementsofNozzlesonNOGenerationPathWANG Ge，CAO Yanguang， HE Tianzhi，CAI Lei

Abstract： Numerical simulation is employed to study the NO generation path and key elementary reaction rates in a natural gas tunnel kiln. The influences of excess air coefficient and arrangements of nozzles (staggered arrangement of nozzles and relative arrangement of nozzles) on the NO generation path are analyzed. The results show that the main elementary reaction rates at excess air coefficient of 1.1 are lower than that of excess air coefficient of 6.0，resulting in less generation of NO. When excess air coefficient increases from 6.0 to 9.0，the reaction rate of the main elements for NO generation R251，R236，and R235 decreases and the NO generation decreases. When the nozzles are arranged in a staggered way，although the reaction direction of the R216 generating NO is opposite to the relative arrangement of the nozzles，the disturbance of the airflow in the kiln is enhanced，the main elementary reaction rate for NO generation increases，and the NO generation increases.

Keywords: tunnel kiln; numerical simulation; NO generation path; excess air coefficient; arrangement of nozzles

GasTransmission，Distribution，StorageandTransportationPracticeofRiskAssessmentofBuriedSteelGasPipelineZENG Rui

Abstract： Combined with an example，the risk assessment of buried steel gas pipelines is discussed. The workflow of risk assessment of buried steel gas pipelines is introduced. The comprehensive inspection is used to collect various pipelines data required for risk pre-assessment. The risk value is calculated by scoring the probability of failure and the consequences of failure，and the risk level is determined. After the rectification of safety hidden dangers，the risk reassessment is conducted and then the risk level is re-determined. Gas enterprises use the four-color marking method to mark the gas pipeline of geographic information system and control the risk.

孙思邈哈哈一笑：“老血不去，新血不生，没事！这三个娃娃头有点意思，老头子我再领着几位小兄小妹，陪他们玩玩，谷主你留好气力，去对付方乾那难缠的老小子。”一边抹去嘴边的血沫，长吟道，“若夫乘天地之正，而御六气之辩，以游无穷者，彼且恶乎待哉！变阵！”他一声断喝，其余六人重新步天踏斗，各归其位，内力一转，阵势甫变！

Keywords: buried steel gas pipeline; risk assessment; comprehensive inspection; risk control; four-color marking method

ConditionsforMixingofBio-naturalGasintoUrbanGasPipelineNetworkWU Yuanyuan，ZHANG Jiawei， CHANG Xuning

Abstract： The quality requirements and interchangeability of bio-natural gas mixed into the urban gas pipeline network are analyzed. The effects of impurities and pollutants in bio-natural gas on the use safety of gas appliances and the health of personnel are discussed. In order to comply with the quality requirements for the second class of natural gas inNaturalGas(GB 17820-2018)，the bio-natural gas entering the urban gas pipeline network should meet at least the standards of the second class stipulated inStandardforQualityofBiomethane(NB/T 10136-2019). Liquid water and liquid hydrocarbons are not present in bio-natural gas under pressure and temperature conditions at the junction. Before the bio-natural gas is mixed into urban gas pipeline network，interchangeability evaluation work should be carried out to meet the requirements of the gas appliance in use. The content of impurities and pollutants in bio-natural gas should be strictly controlled，so as not to affect the use safety of gas appliances and the health of personnel.

Keywords: bio-natural gas; urban gas pipeline network; quality; interchangeability

GasPipelineProtectiveCulvertCrossingSubwayinImmersedAreaZHANG Yunyang

Abstract： Combined with engineering examples，in view of city gas pipeline protective culvert crossing subway in immersed area (referring to area with higher groundwater level)，the requirements of the standard for the design of protective culverts are analyzed. The key design points of semi-filled protective culvert are proposed. The cross section form of semi-filled protective culvert is given. The calculation method of anti-floating design of protective culvert in immersed area is discussed.

Keywords: town gas pipeline crossing subway; protective culvert; semi-filled; fully immersed state; anti-floating design; immersed area

LiquefiedNaturalGasSimulationofLow-temperatureColdStorageGroupBasedonLNGColdEnergyUtilizationHE Junyan，YU Kezhi

Abstract： Based on the scheme of low-temperature cold storage group utilizing LNG cold energy，Aspen Hysys simulation software is used to build a complete process，compare and select 13 refrigerants，compare series and parallel connections，and analyze economic benefits. It is found that No.1 (R23)，3 (R170)，8 (R508A)，11 (50% R170+50% R744)，12 (45% R290+55% R744) and 13 (29% R290+71% R744) refrigerants are all optional. Among them，No. 11 and No. 13 refrigerants have better refrigeration effect，and No. 12 refrigerants have the best refrigeration effect. The scheme of using LNG cold energy to provide a cold source for the low-temperature cold storage group is suitable for adopting all parallel ways of different low-temperature cold storage.

Keywords: LNG cold energy; cold storage group; Aspen Hysys software; refrigerant

DesignandResearchonaZero-dischargeLNGTankContainerZHANG Xiaoxue，TANG Xiaowei， WANG Yang，WANG Haiwei，ZHANG Jian

Abstract： Aiming at the problems of energy waste and environmental pollution caused by the large amount of bog produced and emptied by LNG tank container during transportation and storage，a zero-discharge LNG tank container was developed using external refrigeration equipment of high-power Stirling refrigerator as the cold source. The structure and principle of the tank container are introduced. The LNG tank container with refrigerator can effectively realize the liquefaction and recovery of BOG to avoid the release of BOG. The heat absorbed by the tank container is calculated. Pro II software is used to simulate and calculate the pressure rise of the tank container when the refrigerator is not started or started. When the refrigerator is not started，the temperature and pressure in the tank container gradually rise over time. When the refrigerator is started，the tank container pressure fluctuates periodically，first decreasing and then increasing. The influencing factors of the tank container pressurization are analyzed，and the effects of the starting and stopping pressure of the refrigerator and the initial filling rate on the pressurization rate of the tank container are discussed. When the starting pressure is the same，the tank pressure will change periodically under different starting and stopping pressures. The smaller the starting and stopping pressure difference，the shorter the change period of the tank container pressure. The operation cost is the lowest when the starting and stopping pressures of the refrigerator are 0.79 and 0.70 MPa. The larger the initial filling rate is，the slower the pressurization speed of the tank container，and the longer the starting and stopping cycle of the refrigerator. Combining with the engineering example，the economic analysis of zero-discharge LNG tank container is carried out. The static investment payback period of the zero-discharge LNG tank container renovation project is 423 days，and the annual operation net income is about 7.77× 104yuan.

AnalysisofMainFactorsAffectingAdvancementofCoal-to-gasPointSupplyProjectGAO Limin

Abstract： The reasons for the slow advancement of the coal-to-gas point supply project are analyzed from the aspects of standard specification，institution and supply. The specification specially adapted to the point supply project is lagging behind，the natural gas policy is incomplete，and the natural gas supply gap is large. Suggestions are made.

Keywords: coal-to-gas; point supply; standard specification; institution; supply

GasVehicle，ShipandGasFuelingStationCalculationofBasicStateEquationandThermalPhysicalParametersofStandardHydrogen

LI Jianxun

Abstract： In the field of hydrogen refueling stations，hydrogen is generally regarded as standard hydrogen. Taking standard hydrogen as the research object，the calculation of the basic state equation and thermal physical parameters (compression factor，specific enthalpy and specific entropy) of standard hydrogen are analyzed. The variation trend of thermal physical parameters with pressure at different temperatures is given.

Keywords: standard hydrogen; basic state equation; thermal physical parameters

EngineeringPracticeofCommercialHydrogenRefuelingStationDI Wei，LIU Wei，LIU Fei，LI Yulei

Abstract： Based on the engineering example of Rugao hydrogen refueling station，the engineering practice experience of commercial hydrogen refueling station is summarized，involving project approval，main standards and specifications，design and construction，safety control system，commissioning and trial operation，hydrogen quality management and so on.

Keywords: commercial hydrogen refueling station; engineering practice; hydrogen quality management

GasSourceandProcessingUtilizationErosionSimulationandStructureImprovementofSandyNaturalGasThrottleValve

QIAN Dongliang，TIAN Huifang

Abstract： In the oil and gas well surface equipment，natural gas contains mud and sand，and the pipeline transport medium is gas-solid two-phase flow. Inside the throttle valve，erosion damage will occur under the continuous impact and cutting action of the gas-solid two-phase flow (especially the sand particles therein). Based on conical throttle valve and wedge throttle valve，three improved structural forms are proposed: conical throttle valve of round table valve core，wedge throttle valve of round table valve core and wedge throttle valve of three section valve core. Taking the above-mentioned five types of throttle valves with a size of DN 50 mm as examples，a geometric model was established using Pro/E 5.0 software，and modeling analysis was performed using ANSYS Fluent 14.5 software. Natural gas is used as the continuous phase，sand is used as the discrete phase，RNGk-εturbulence model is used for the continuous phase，discrete phase model is used for the discrete phase，and erosion rate formula defined in ANSYS Fluent 14.5 is used for erosion rate model. The conclusions are as follows: Under the condition of gas-solid two-phase flow，erosion damage inside throttle valve is unavoidable. The locations of erosion damage inside the throttle valve are the facing wall of the valve core，the junction of the valve core and the throttle hole，and the inner wall surface of the outlet pipe section. The software simulation results are consistent with the field erosion failure. To some extent，the three modified valve core structures have changed the movement track of sand particles，reduced the erosion of the inner wall of the outlet pipe section，and played a certain protective role in the main area of throttle valve erosion control. In addition to adopting methods to improve the structure of the valve core，the erosion damage inside the throttle can also be slowed down by adopting measures such as erosion-resistant materials，coating protection，installation of hard alloy sleeves，and installation of anti-sprint short joints.

Keywords: oil and gas well surface equipment; throttle valve; gas-solid two-phase flow; sandy natural gas; erosion rate

GasInformatizationComprehensiveManagementofIndoorDataforGasResidents

SHAN Luwei

Abstract： Aiming at the development trend of indoor information diversification of residential users，a comprehensive consideration of user needs is proposed to provide integrated technical solutions for user data collection and processing. The concentrator is responsible for the collection，storage and uploading of all indoor data，and receives instructions from the comprehensive data management platform at any time. Relying on the existing management system of settlement and service of gas company to carry out value-added business development，the gas management，flammable gas monitoring and management，fire safety，water supply management，heating management and so on are designed and integrated in the data integrated management platform.

Keywords: indoor data; comprehensive management; Internet of things gas meter; residential user

GasEnterpriseManagementManagementDilemmaandCountermeasureofHighConsequenceAreaofUrbanGasPipeline

WANG Chen

Abstract： The identification of high consequence area of urban gas pipeline is introduced，the dilemma in the management of high consequence areas is analyzed，and the concept of management unit of high consequence areas is proposed. The management and control countermeasures for pipelines in high consequence areas are analyzed from the aspects of strengthening source control，focusing on the intrinsic safety of the pipeline，improving the level of technical prevention and application，and improving emergency response capabilities.

Keywords: urban gas pipeline; high consequence area; control; dilemma; risk; countermeasure

OverseasGasResearchonForeignGasTheftandControl

ZHANG Xiongjun，LIU Xingwei， ZOU Geyang

Abstract： The per capita natural gas consumption and prices of some countries in 2018 are given. The main body of theft，common theft behavior，theft loss，control costs and control measures for foreign gas are investigated and analyzed.

Keywords: foreign; gas theft; unaccounted-for gas; control