Abstracts and Key Words

HeatSourceandColdSourceInfluenceofInnerTubeArrangementandWallTemperatureofCasing-typePhase-changeHeatAccumulator

GUO Mengxue

Abstract： The horizontal casing-type phase-change heat accumulator is used as the research object which consists of the outer tube，four same inner tubes and the phase change material paraffin. The outer tube has a radius of 50 mm and a length of 480 mm，and the inner tube has a radius of 10 mm and a length of 500 mm. The outer tube is placed on the outside of the 4 inner tubes，and the heat transfer fluid is connected at both ends of the inner tube. The enclosed space between the outer tube and the inner tube is sealed with paraffin. Since the tube length is short，it is assumed that the heat transfer fluid inlet and outlet temperatures are substantially the same，and the heat accumulator is simplified to a two-dimensional model. The two-dimensional model was solved by COMSOL Multiphysics software. When the inner tubes are arranged in square，diamond 1 and diamond 2，the melting process and solidification process of paraffin were observed，and the effects of different arrangements on the heat transfer of the phase-change heat accumulator were analyzed. The square arrangement with best heat transfer effect was selected to simulate the influence of different inner tube wall temperatures on paraffin melting and solidification process，and the effects of different inner tube wall temperatures on heat transfer of phase-change heat accumulator were analyzed. The results show that when the inner tubes are arranged in different ways，the time required for the melting and solidification of paraffin in the square arrangement is the shortest; when the wall temperature of the inner tube arranged in square increases from 313 K to 323 K and 333 K，the complete melting time decreases by 43.57% and 57.14 %，respectively. When the inner tube wall temperature decreases from 293 K to 283 K and 273 K，the complete solidification time is shortened by 47.57% and 59.97%，respectively.

Keywords: phase-change heat accumulation; casing-type heat accumulator; arrangement mode of inner tube; inner tube wall temperature; numerical simulation

Heat-supplyNetwork，Cooling-supplyNetworkandSubstationApplicationofShear-pinTypeFixedSupportinLargeDiameterHeatingPipeNetwork

LIU Shiyu

Abstract： A kind of shear-pin type fixed support is proposed，and its structural design and strength calculation analysis are carried out. The performance test of the actual size of the support is carried out and the satisfactory results are obtained. This kind of shear-pin type fixed support has been applied for four years in the actual engineering，and all performance indicators meet the requirements of design and use.

Keywords: large diameter heating pipeline; shear-pin type fixed support; actual size test

SimulationofMulti-heatSource
NetworkingOperation
XU Zheng，XIANG Kezheng，HU Jingyang

Abstract： Taking 5 heat sources (heat sources A to E) in Qingdao area as the research object，and taking the heat source capacity at the end of 2020 as the condition，under the condition of no new heat source，the simulation software of multi-heat source networking is adopted. The feasibility of multi-heat source interconnection operation to meet the 2020 heat load is calculated and analyzed. By 2020，the residual heating capacities of heat sources A and B are 114 MW and 3 MW respectively. The heat sources C and D have no residual heating capacity，and the heat source E (using purchased heat supply) has a heating capacity gap of 80 MW. In order to make full use of the residual heating supply capacity of heat sources A and B，and reduce the purchased heat of the heat source E，the starting sequence is set to heat source A to heat source E. The simulation results show that the heat sources A to E networking operation can meet the heat load demand in 2020. According to the simulation results，the heat source circulating pump can be selected to adapt the operational requirements at different outdoor temperatures.

Keywords: multi-heat source networking; simulation; heating capacity

BuildingHeating，AirConditioning，VentilationandThermalEnvironmentCharacteristicsofGasConsumptionduringHeatingPeriodofRuralCoal-to-gas
UsersinBeijing

WANG Xun，QIAO Jia，JIANG Xin，CHAI Jiafeng

Abstract： During the heating period from 2017 to 2018，the gas consumption data of 2 800 household coal-to-gas residents for 14 villages (communities) in Beijing Huairou District，Miyun District，Pinggu District，Yanqing District and Tongzhou District (gas consumption during heating period of all users and daily gas consumption of some users) are measured，and the data on user information (building type，population，heating area and so on)，indoor temperature，outdoor average temperature and so on are investigated and collected. The box plot method is adopted to analyze the gas consumption distribution of unit heating area during heating period of users in different type buildings，and the outliers are checked. Compared with the villa users and building users，the gas consumption distribution of unit heating area during heating period of flat house users is more dispersed. There are 6 outliers in the flat house user data. The data of flat house users and villa users show a skewed distribution，and after checking the data of building users show a normal distribution. When the low calorific value of natural gas is 34.5 MJ/m3，the gas consumption indicator of unit heating area during heating period in building users is 8. 722 to 9.916 m3/m2.

Keywords: rural area; coal-to-gas; heating load; gas consumption; heating gas index; box plot

InfluencingFactorsofBuriedAirDuct
onAirCoolingEffect
YANG Xiaoyu，ZHANG Shan，
LIU Sijia,ZHANG Lingling

Abstract： For the air pre-cooling condition of the tunnel air system，the calculation method of the original temperature of the stratum is introduced，and the mathematical model of air temperature at the outlet of the concrete buried air duct in daily continuous operation mode and daily intermittent operation mode is described. The influencing factors of the air temperature and air temperature drop at the outlet of the buried air duct (including the buried air duct center depth，the operation mode and the length of the buried air duct) are calculated and analyzed. With the increase of the buried duct center depth，the air temperature drop increases first and then decreases，there is the best center depth. The operation modes include the daily continuous operation mode (24 hours all day)，the daily intermittent operation mode 1 (8 hours every day) and the daily intermittent operation mode 2 (16 hours every day)，and the operation days of the three operation modes are all 30 d. The air temperature at the outlet of the buried air duct in the three operation modes increases with the extension of the operation time. The air temperature at the outlet of the buried air duct in the daily intermittent operation mode 1 is the lowest，the daily intermittent operation mode 2 is the middle，and the daily continuous operation mode is the highest. Compared with the daily continuous operation mode，the daily intermittent operation is conducive to the recovery of soil temperature. For the daily intermittent operation mode，short-term operation is more conducive to the recovery of soil temperature. The air temperature drop increases with the increase of the length of the buried air duct. When the buried air duct reaches a certain length，the amplification of the air temperature drop is no longer obvious，and the buried air duct has a reasonable length.

Keywords: tunnel air system; air pre-cooling; center depth; operation mode; length of buried air duct

ImportanceandEffectofGroundRadiantHeatingSystemCleaning

LIANG Yougao，ZHONG Jiasong

Abstract： The ground radiant heating system that has been used for 2 years is experimentally analyzed before and after cleaning. After using the heating system for a period of time，various factors cause the resistance to become larger，and the circulating water flow becomes smaller，thereby affecting the good matching operation between the gas heating and hot water combi-boiler and the heating pipeline. After cleaning the system，the resistance decreases，the system flow rate and the actual heat input of the gas heating and hot water combi-boiler are greatly improved，the heating system returns to a better working state，and the system cleaning effect is good. Therefore，it is very important to clean the heating system regularly.

Keywords: gas heating and hot water combi-boiler; heating system; cleaning; actual heat input; temperature difference between supply and return water

EconomicComparisonbetweenHouseholdGasHeatingSystemandAir-sourceHeatPumpHeatingSystem

MA Jie，QI Hanfei，F(xiàn)AN Jiwen，LI Shifang

Abstract： Taking three typical housing types of a residential building in Hangzhou as the research object，the economy of the two heating systems under different ladder gas prices is analyzed. The investment and investment’s net present value of the household gas heating system is lower than that of the air-source heat pump system，but the operation and maintenance costs are much higher. The constraints of the promotion of household gas heating systems are analyzed，and recommendations on the gas price mechanism for gas heating are made.

Keywords: household gas heating; air-source heat pump system; economy; heating and hot water combi-boiler

GasTransmission，Distribution，StorageandTransportationStudyonEvaluationIndicatorsofAgingPerformanceofGasPolyethylenePipeinService

LIN Dong，CEN Kang，PU Changxing，HU Xing，SHAO Chenchen

Abstract： Five gas polyethylene pipes with different service times are selected to detect oxidation induction time，melt mass flow rate，carbon black content and density. Through the comparison and analysis of the test data，the indicators suitable for evaluating the aging performance of gas polyethylene pipes in service are explored. The results show that the longer the pipe use time，the greater the change rate of oxidation induction time and melt mass flow rate，and the weaker the oxidation performance and flow performance of the pipe. The carbon black content of the pipe is limited by the processing conditions，and it may occur that the carbon black content of the pipe in service is greater than that of the new pipe. The density of the pipe is basically unchanged during the service，and the aging performance of the pipe cannot be characterized. The oxidation induction time and the melt mass flow rate are suitable for evaluating the aging performance of the pipe，while the carbon black content and density are not suitable for evaluating the aging performance of the pipe. The research results provide a reference frame for the reasonable determination of the evaluation parameters in the integrity test of polyethylene gas pipelines.

Keywords: polyethylene pipe; aging performance; evaluation indicator

IntegrityEvaluationTechnology
ofDefectivePipeline
MA Bin，JIANG Feng，MA Xuqing

Abstract： Based on the Spangler-lowa method，combined with finite element modeling，statistical analysis，mathematical fitting and experimental verification and so on，the external load carrying capacity and internal pressure carrying capacity of the defective pipeline are studied. For the evaluation of the external load carrying capacity of the intact pipeline，the Spankler-lowa method was used to calculate the horizontal diameter deformation of the pipeline，and then the horizontal deformation rate of the pipeline was obtained. When the horizontal diameter deformation rate of the pipeline exceeds 3%，the pipeline is considered to be ineffective. Evaluation of external load carrying capacity of the pipeline with uniform corrosion defects is as follows:the pipeline with small diameters (outer diameter ≤ 700 mm) can be evaluated according to the minimum nominal wall thickness specified in GB 50028-2006; and the pipeline with large diameters (outer diameter > 700 mm) ) should be evaluated according to the calculation results of the Spangler-lowa method. The pitting defect has little effect on the deformation of the pipeline affected by the external load. However，considering the influence on the airtightness and other performance of the pipeline，the pitting perforation diameter of the gas pipeline specified in the evaluation cannot be not more than 50 mm. When evaluating the integrity structural strength of gas pipeline with surface corrosion defects，it is necessary to consider the pressure levels of gas pipelines respectively. For medium and low pressure gas pipelines，the effect of external load is mainly considered，and the deformation of pipeline is used as the evaluation basis of external load carrying capacity. For the sub-high pressure pipeline，the effects of internal pressure and external load are considered respectively，and the deformation and stress of the pipeline are used as the evaluation basis of the carrying capacity of the pipeline. For the high-pressure gas pipelines，the effect of the internal pressure is mainly considered，and the stress at the pipeline defects is used as the evaluation basis of internal pressure carrying capacity. For medium and low pressure and sub-high pressure gas pipelines with surface corrosion defects，it is necessary to evaluate the carrying capacity of the external load. The effects of the length，width，depth and position of the surface corrosion defect on the deformation of the pipeline are analyzed. The mathematical model for evaluating the external load carrying capacity of pipeline with surface corrosion defects has been studied innovatively，and the correctness of the mathematical model was verified by experiments. When selecting the internal pressure carrying capacity evaluation method，it is recommended to use the ASME B31G-2009 method to evaluate the internal pressure carrying capacity of gas pipeline with surface corrosion defects. This paper only focuses on the evaluation of pipeline strength with corrosion defects in the integrity evaluation of gas pipeline. It is suggested that the research objects should be broadened in the future，and the evaluation methods of pipeline integrity for other defects，such as cracks，dents and weld defects，should be carried out.

Keywords: city gas pipeline; integrity evaluation; defective pipeline; pitting; surface corrosion; carrying capacity

SimulationofGasQualityChangeatUserEndunderMixedTransmissionConditionofMulti-gasSourcePipeline

FENG Liang

Abstract： The dynamic mixed transmission condition of multi-gas source and multi-user pipeline is simulated and calculated by SPS software. The fluctuation ranges of methane volume fraction and net Wobbe index at the pipeline end power plant user are analyzed according to the parameters such as gas source quality composition，low calorific value and net Wobbe index. Under the current operating conditions，the fluctuation range is within the acceptable range of the power plant unit，and no gas quality adjustment is required.

Keywords: multi-gas source; gas quality fluctuation; simulation analysis; mixed transmission condition

DiscussiononSafetyTechnologyofLayingNaturalGasPipelineinCityUtilityTunnel

ZHANG Xuemiao，ZHANG Lin

Abstract： Problems of cracks in wall of utility tunnel，pipeline corrosion，damage of local anticorrosive layer，thermal deformation of pipeline，pipeline floating and so on are analyzed. It is proposed to adopt measures such as optimizing the structure of utility tunnel，using reinforced grade 3PE anticorrosive coating，protecting the local anticorrosive layer with light curing protective sleeve，installing square compensator，anti-floating design，natural gas compartment fireproofing and explosion-proof design to ensure the intrinsic safety of the project.

Keywords: natural gas pipeline; utility tunnel; settlement joint; light curing protective sleeve; square compensator; anti-floating

LiquefiedNaturalGasComparisonofLargeLNGBimetallicWallandTrimetallicWallFull-containmentTanks

FAN Haijun，ZHU Jinhua，DAI Xingwang，NIU Zheng

Abstract： Considering the high cost and complicated manufacturing and installation process of full-containment tank using concrete sub-container in large LNG receiving stations，aimed at LNG storage tanks with nominal volume of 5×104m3or less in urban peak shaving and liquefaction plant projects，a more cost-effective metal wall full-containment tank is designed according to the requirements ofDesignandManufactureofSiteBuilt，Vertical，Cylindrical，F(xiàn)lat-bottomedSteelTanksfortheStorageofLiquefiedNaturalGases(GB/T 26978-2011) and other standard specifications. Although there is a definition of metal wall tank in relevant standards，there is no precedent in foreign countries for this kind of tank，and there are few examples in our country. Taking a 25 000 m3full-containment tank under construction in a certain place as an analysis object，the structural type，thermal insulation performance，construction technology，construction period and cost of LNG bimetallic wall full-containment tank and trimetallic wall full-containment tank are compared and analyzed. The advantages and disadvantages of the two structures are analyzed. All the indicators of the bimetallic wall full-containment tank and the trimetallic wall full-containment tank can meet the requirements of the metal wall full-containment tank in the standard specifications. There is no significant difference in the floor space，construction cost and construction period between the bimetallic wall full-containment tank and the trimetallic wall full-containment tank. The trimetallic wall full-containment tank has certain advantages over the bimetallic wall full-containment tank in terms of thermal insulation performance and construction technology，and is more safe，reliable and energy-saving.

Keywords: LNG storage tank; bimetallic wall; trimetallic wall; full-containment tank; structure; thermal insulation performance

OptimizationofPressureControlTechnologyofLNGStorageTankinReceivingStation

ZHANG Zhen，ZHANG Bingbing，ZHU Hong，ZHANG Yan

Abstract： The commonly used control modes of LNG storage tank pressure are analyzed. Taking the Dalian LNG receiving station as an example，the control mode of mutual coordination between the top feeding and the bottom feeding in the unloading condition is discussed，and the relative openings of the bottom feeding valve and the top feeding valve are adjusted to control the tank pressure. In non-unloading condition，the operating pressure of the tank is increased to reduce the static evaporation rate of the tank，and the energy consumption of the BOG compressor is saved.

Keywords: LNG tank pressure; boil-off gas (BOG); unloading; receiving station

ComparisonStudyonDesignLoadCombinationofLNGStorageTankinEuropeanandAmericanCodes

CHEN Shengsen，ZHANG Chao，CHEN Tuanhai

Abstract： The provisions on load combination in the two code systems are explained，the load combination schemes and load factor of the LNG tank design are determined，and the consistency and difference in the load combination conditions and the load factors of the key loads between the two code systems are analyzed. It is verified by example，and the results show that the calculation results of the load combination schemes determined by the two codes are in good agreement，and the change trend of the results is exactly the same，but there are certain differences in the extreme value region. When designing with the European standard，the reinforcement results of the cap and the wall are too large. When designing with the American standard，the design results of the pile foundation and the dome are too large. The maximum difference of the outer tank structure is less than 25%，and the maximum difference of the pile foundation structure is less than 5%.

Keywords: LNG storage tank; load combination; European code; American code

EfficientUtilizationofLiquefiedNaturalGasinInnerMongoliaAutonomousRegion

HE Xiaodong，WANG He，GAO Zishu，YANG Yuli，WU Huimin，HE Xiaozhong

Abstract： The current situation of natural gas supply and consumption in Inner Mongolia，the consumption structure and the economy of LNG used in heavy trucks and intercity buses in the road transportation field is analyzed. It is pointed out that LNG is highly economical in the utilization of heavy trucks and intercity buses，and it is the main way for the LNG industry to be efficient，healthy and long-term development.

Keywords: Inner Mongolia; efficient utilization of LNG; LNG truck; vehicle LNG

GasEquipmentandMaterialsApplicationofNB-IoTCommunicationTechnologytoSmartGasMeter

SHAO Zehua

Abstract： The development status of wireless communication technology for smart gas meter is explained. The characteristics of NB-IoT communication technology applied in smart gas meter are analyzed. It is pointed out that the existing problems of smart gas meter using NB-IoT communication technology (lack of necessary transaction authentication mechanism，lack of professional processing capability of gas data and insufficient technical maturity). The above-mentioned problems are solved through the built-in gateway in the smart gas meter. The structure of the smart gas meter with the built-in gateway and the structure and function of the gateway are indicated. The built-in gateway has information security protection function，can perform communication authentication and transaction authentication. It has professional gas data processing capability，which can ensure the synchronization of the upgrade of smart gas meter application program with the upgrade of the telecom operator network. The information exchange process between smart gas meter and gas company server is discussed.

Keywords: smart gas meter; NB-IoT; gateway; wireless communication technology

GasEngineeringConstructionandDevelopmentCaseStudyonLargeHorizontalDirectionalDrillingCrossingQiantangRiverProject

SHEN Yue，QIAO Heng，QIAO Zhiguo，HUANG Jian

Abstract： The hydrogeological conditions，design parameters，pre-approval，construction process selection and construction organization scheme are introduced. The problems encountered during construction and the solutions are discussed，and the experience is summarized. The pipeline horizontal directional drilling crossing construction video is attached at the end of the paper.

Keywords: large horizontal directional drilling crossing; trenchless; Qiantang River; construction organization

GasEnterpriseManagementQuantitativeCalculationofPersonalRiskofToxicGasesBasedonGridMethod

ZHANG Xixiang，ZHANG Qiang，ZHANG Huabing，CHENG Wanzhou，WEI Ranran，YANG Yufeng，WANG Xin，GAO Dongdong，LI Mingyue

Abstract： Based on the quantitative calculation of personal risk of toxic gases based on grid method by the Netherlands Academy of Applied Sciences (TNO)，the dividing principle of the grid of personal risk calculation，the selection of failure events，and the methods for determining the joint distribution probability of meteorological grade and wind direction and the frequency of events are introduced. The calculation model of death probability and the calculation steps of personal risk value are also introduced. Taking the CO leakage of gas pipeline as an example，the personal risk calculation is carried out.

Keywords: quantitative risk assessment; grid method; personal risk; toxic gas; leakage

ControlofKeyParametersandDesignofMeteringDeviceforGasPipelineReplacement

ZHANG Yuxing，MA Xuqing，HE Yi

Abstract： The safety control elements and parameter control methods of the direct replacement method for city gas pipelines are discussed. It is concluded that the replacement speed is an important parameter that affects the replacement safety and efficiency. The mobile metering device suitable for sub-high pressure and below pipeline replacement was designed，and the field tests were performed. The results show that under the test conditions，the gas emission is approximately equal to the pipeline volume. It is suggested that the conversion coefficient between gas emission and pipeline volume is analyzed and obtained by multiple replacement engineering field tests.

Keywords: gas pipeline replacement; parameter control; mobile metering skid; direct replacement method; replacement speed

FeasibilityStudyofPlasmaArcCuttingTechnologyunderPressurizedGasEnvironment

HU Yiyong，LI Xiaxi，LI Song，LIANG Wenhu，LI Zhuowei，WAN Ronghui

Abstract： A plasma arc cutting technology under pressurized gas environment is proposed，the plasma arc cutting test scheme under pressurized gas environment is designed，and the feasibility test of hole cutting operation of pressurized gas pipeline is carried out. The pressurized gas environment is simulated by the mixture of nitrogen and natural gas，the gas pressure ratio increases from 0% to 100% with an interval of 10%. The experimental results show that the plasma arc cutting test can be successfully completed under the mixed gas environment with different gas pressure ratios，and the cutting edges of the test workpiece are uniform and smooth，which proves that the plasma arc cutting technology is feasible for hole cutting under the pressurized gas environment. At the end of the paper，the plasma arc cutting test video under pressurized gas environment is included，which can be watched by scanning the QR code.

Keywords: pressurized gas environment; plasma arc; cutting technology; gas pressure ratio