Abstracts and Key Words

SpecialColumnforSmartHeating,GasSupplyandBuildingEnergySaving ofHarbinInstituteofTechnology

ExperimentalResearchonEjector HeatExchangeSystemwithLarge TemperatureDifference

ZHANG Chenghu，LIN Jiyou，LI Yaping，TAN Yufei

Abstract： To solve the problems of the expansion and reconstruction of the heating network and ultra-long-distance heating in the field of district heating，based on the ejector heat pump，two kinds of ejector heat exchange systems with large temperature difference in parallel type and series type are proposed. Based on mathematical modeling and organic working fluid optimization，an experimental prototype of parallel type ejector heat exchange system with 170 kW total heat exchange of water in the primary network was built. The start-up and shut-down characteristics and the thermal performance under rated and variable working conditions were experimentally studied. The results show that the parallel type system is more adaptable to variable working conditions. The start-up and shut-down times of the parallel type ejector heat exchange system with large temperature difference are both 15 minutes，and the start-up and shut-down process is simple with a quick response. Under the rated conditions that the water mass flow of the primary network is 0.60 kg/s，the water mass flow of the secondary network is 3.75 kg/s，the return water temperature of the secondary network is 44.33 ℃，and the supply water temperature of the primary network is 110.61 ℃，the experimental prototype can increase the supply water temperature of the secondary network to 55.38 ℃ and greatly reduce the return water temperature of the primary network to 39.48 ℃，which can realize the heat exchange process with large temperature difference. Under the variable conditions that the water mass flow of the primary network is 0.60 kg/s，the water mass flow of the secondary network is 3.75 kg/s，and the return water temperature of the secondary network is 44.33 ℃，the heat exchange capacity of the ejector heat exchange system with large temperature difference increases significantly with the increase of the supply water temperature of the primary network.

Keywords: district heating; heat exchange with large temperature difference; ejector heat pump; start-up and shut-down characteristics; variable condition characteristics

StudyonCorrectionMethodforAbnormal OperationDataofHeatingNetwork

GUO Jiachang，LAN Yun，XUE Puning，ZHOU Zhigang，LIU Jing

Abstract： In order to solve the problem that the erroneous data in the heating data interferes with the in-depth mining analysis，a three-step method of data correction for anomaly detection，anomaly classification，and anomaly replacement is proposed. The simulation data set of the theoretical model constructed is used to improve the data foundation，and the simulation data set of abnormal operating conditions is constructed with the parameter change rate. The first step is to establish an anomaly detection model based on the isolated forest algorithm，which shows good anomaly detection performance on the sample set. The second step is to build an anomaly classification model based on the BP neural network. Using the simulation data set of abnormal operating conditions as a training sample，the classification accuracy of the tested model can reach more than 90%. The third step is to replace the data record determined as "measurement abnormality" with the conditional mean on the time series. The operating data uploaded by a heating station in a heating system were corrected，which proved the feasibility of the data correction method.

Keywords: heating network; data anomaly; hydraulic calculation model; isolation forest; BP neural network; data correction

EconomicalOptimalConfiguration ofIndustrialWasteHeatRecovery andReserveSystem

WANG Jinda，ZHOU Zhigang，LIU Jing，ZHAO Jianing，ZHENG Jinfu

Abstract： In-depth study on the problem of economic optimal configuration of clean renovation of existing district heating system is conducted. The system renovation scheme of industrial waste heat recovery by using low-cost power is given. The operation optimization scheduling of the renovation system is analyzed. Based on the incremental comparison method，a two-layer optimal configuration model of waste heat recovery and storage equipment is proposed. Based on case calculations，the proposed economic optimal configuration model is verified. The results show that compared with the genetic algorithm，the pattern search has the faster convergence speed and higher computational stability when solving the two-layer optimal configuration model. The reasonable configuration of waste heat recovery reserve equipment can obtain considerable comprehensive income in heating period.

Keywords: time-of-use electricity price; waste heat recovery; optimal configuration; genetic algorithms; pattern search

ResearchonDefrostingJudgmentIndex andStandardofLNGAmbientAir TemperatureVaporizer

REN Lemei，JIAO Wenling

Abstract： In order to reasonably determine the switching operation cycle (defrosting cycle) of LNG ambient air vaporizers (AAVs)，the defrosting judgment index and standard are studied based on the heat transfer model of LNG AAVs. From the perspective of heat transfer and frost layer growth in the tube，tube wall and outside，the heat transfer models of vaporizers under non frosting and frosting conditions are established. The influence of ambient temperature on heat transfer characteristics of vaporizers is analyzed. Energy demand，frosting heat loss coefficient，frosting area loss coefficient and frost coverage rate and so on are defined，and the defrosting judgment index system for switching operation of LNG AAVs is established，which is composed of energy demand，frosting heat loss coefficient，frosting area loss coefficient，frost coverage rate and operation time. The reference operating conditions of vaporizers are put forward，and the standard for defrosting judgment index of LNG AAVs is discussed. The defrosting judgment standard of vaporizers is evaluated combined with engineering example. The energy demand，frosting heat loss coefficient，frosting area loss coefficient and frost coverage rate have important reference significance in the determination of vaporizer defrosting judgment and defrosting cycle.

Keywords: liquefied natural gas; ambient air vaporizer; defrosting judgment index; defrosting judgment standard; defrosting cycle

SimulationStudyonLeakageDiffusion ofUrbanDirectlyBuriedGasPipeline alongSoil

CHANG Huan，TAN Yufei，WANG Xuemei，XIAO Rong，ZHANG Xingmei

Abstract： A three-dimensional mathematical model of the diffusion in soil after small-hole leakage in urban medium-pressure natural gas pipeline was established. The diffusion process of leaked natural gas in loam was simulated numerically by CFD software，and the variation laws of natural gas velocity and mass fraction in different soils were compared and analyzed. The study results show that the velocity field and pressure field of leaked natural gas in loam reach stable distribution state in a very short time (within 100 s). There are large velocity gradient and pressure gradient near the leakage hole，and the diffusion speed of natural gas is very slow at the place far away from the leakage hole. Near the leakage hole，the natural gas diffuses convectively under the action of the pressure difference and the volume fraction difference，forming a vertical asymmetric high concentration area，and the volume fraction above the pipeline is greater than that below the pipeline. In the loam area far away from the leakage hole，only molecular diffusion is caused by the difference in volume fraction，natural gas diffuses concentrically. With the increase of the leakage time，the danger radius and the danger area in the soil are gradually expanding. In loam，when the pipe diameter is 100 mm，the pressure is 0.4 MPa and the leakage hole diameter is 10 mm，the danger radius is about 0.4 m at 100 s，1.2 m at 30 min，and 1.5 m at 60 min. The change in the volume fraction of natural gas is Gaussian distribution along the direction of pipe length，and the volume fraction above the leakage hole is the highest. It is suggested that when locating the leakage point of directly buried natural gas pipeline，the drilling position should be 0.5 m above the pipeline. There is a power function relationship between the alarm time of natural gas in loam and the lateral diffusion distance. According to the fitting formula，the leakage time of natural gas pipeline can be predicted in reverse，which provides theoretical basis for risk assessment of gas accidents. Soil types play a key role in the process of natural gas leakage and diffusion. The diffusion rate of natural gas in different types of soil from high to low is silty sand，loam and clay.

Keywords: natural gas; directly buried pipeline; soil，leakage diffusion; numerical simulation

LegislationandTechnologiesofMethane EmissionReductioninU.S.Oil andGasIndustry

WANG Yingfan，XU Xiangang，DONG Jiankai，XIE Donglai，YANG Hanling

Abstract： Aiming at the problem of methane emission from the oil and gas industry in the United States，a number of laws and regulations and emission reduction technologies at the federal level of the United States are introduced. Taking Colorado as an example，the specific policies and regulations at the state level in the United States，as well as the implementation of the policies and regulations and the results achieved are introduced. Ten methane emission reduction technologies and their emission reduction effects are briefly introduced. The comprehensive use of these ten technologies can make the total methane emission reduction ratio of all production link of natural gas reach 89.1%. The legislation，measures and technologies of methane emission reduction in U.S. oil and gas industry can provide reference for China's oil and gas industry.

Keywords: the United States; oil and gas industry; methane emission reduction; greenhouse gas emission; legislation; emission reduction technology

ResearchonOptimizingControl StrategyofHeatingSystem inCollegesandUniversities

WANG Ruixin，ZHOU Zhigang，JING Qiang，CHEN Xuejiao

Abstract： Aiming at northern colleges and universities，based on the steady-state heat transfer model，a simulation model of heating system including heating station，secondary network and building was developed. Combined with the characteristics of campus buildings in different periods of time，the optimization method of room temperature control during the start and stop of heating system and the use of buildings was proposed. The simulation model was used to simulate and analyze the effect of the optimized control strategy. Based on the steady-state heat transfer model，the simulation results of the developed heating system simulation model are credible. Under the control strategy 1 (heating started at 3:00，heating stopped at 22:00，the flow of the secondary network was fixed，and the electric control valve at the consumer heat inlet kept initial opening unchanged during the use period of the building from 8:00 to 22:00)，the indoor temperature of the teaching building met or even exceeded the requirement of 18 to 20 ℃ during the use period of the building on the severe cold day (from 8:00 on January 8 to 8:00 on January 9，2020) and the last cold day (from 8:00 on March 10 to 8:00 on March 11，2020). After stopping the heating at 22:00，the indoor temperature decreased slowly after a rapid decrease，which was mainly due to the thermal inertia of the building. Due to too early start of heating，the indoor temperature during the non-use period of the building was relatively high. The indoor temperature reached 19.5 and 21.8 ℃ at 8:00 on January 9 and 8:00 on March 11，respectively. There was a serious problem of excessive heating. Compared with the control strategy 1，the start-stop strategy of the control strategy 2 (the heating time was 5:00，and the heating stop time was 21:00 on the severe cold day. The heating time was 7:00，and the heating stop time was 19:00 on the last cold day. The flow of the secondary network was fixed，and the electric control valve at the consumer heat inlet kept the initial opening unchanged during the use period of the building) was optimized，and the heating was stopped in advance and the heating was delayed，which could still meet the indoor temperature requirements during the use period of the building. The indoor temperature during the non-use period of the building was also obviously reasonable. The thermal inertia of the building ensured a limited drop in the indoor temperature after the heating was stopped. When the heating started on the severe cold day，the indoor temperature was 16.6 ℃; when the heating started on the last cold day，the indoor temperature was 17.9 ℃. Compared with the control strategy 2，the control strategy 3 (start-stop optimization strategy and room temperature control of the electric control valve at the consumer heat inlet: The heating time was 5:00，and the heating stop time was 21:00 on the severe cold day. The heating time was 7:00，and the heating stop time was 19:00 on the last cold day. During the use period of the building，the opening of the electric control valve at the consumer heat inlet was adjusted to keep the indoor temperature at 18 to 20 ℃) could control the indoor temperature during the use period of the building within the required range. Adopting the start-stop optimization strategy and the room temperature control of the electric control valve at the consumer heat inlet not only keep the indoor temperature within the required range during the use period of the building，but also use the thermal inertia of the building to ensure a limited drop in the indoor temperature after the heating is stopped，which is beneficial to reduce heating energy consumption.

Keywords: college and university heating system; control strategy; simulation model; linear regression algorithm

HeatSourceandColdSource

DiscussiononCleanHeating TechnologyRouteinHotSummer andColdWinterArea

ZHANG Zhigang

Abstract： The ways of clean heating in hot summer and cold winter areas are analyzed. Combined with engineering examples，the cooling and heating loads are calculated，and a clean cooling and heating technology solution for cooling and heating sources is given.

Keywords: hot summer and cold winter area; clean heating; central heating and cooling; energy source station

LiquefiedNaturalGas

BubbleBehaviorandTwo-phase FlowPatternConversion inLNGVaporizerTube

XU Shaojie，GAO Wenxue，YAN Rongsong，WANG Yan，YANG Lin，ZHANG Huan

Abstract： In order to reveal the characteristics of flow boiling in the tube of LNG ambient air vaporizer，the bubble behavior and the two-phase flow pattern conversion was studied. The object of study is a vertical aluminum alloy finned tube，which is equivalently simplified as a vertical empty tube with a height of 5 m，an inner diameter of 0.02 m，and an outer diameter of 0.026 m. The LNG inlet flow rate in the tube is 0.05 to 0.2 m/s，the inlet temperature is 111 K to 126 K，the heat transfer coefficient of the outside surface of the tube varies from 100 to 300 W(m2·K)，the ambient temperature is 300 K，and the ambient pressure is 101.325 kPa. The ICEM 19.0 was used to establish a two-dimensional model of the vertical empty tube and the quadrilateral structured grid was divided. The Fluent 19.0 software was used to simulate the heat transfer in the computational domain of liquefied natural gas or natural gas in the tube and the computational domain of the tube wall solid. The effects of different LNG inlet velocity，inlet temperature and heat transfer coefficient of the outside surface of the tube on the bubble behavior and two-phase flow pattern distribution and conversion during boiling were studied. Fluid volume method was used to track and capture the gas-liquid two-phase interface，and the S. Hardt model characterizing boiling process was introduced into the calculation process by user-defined method. The research results show that bubble aggregation and sliding along the hot wall surface are important movement forms under the action of surface tension，buoyancy，and shear stress between gas and liquid. The increasing temperature of the LNG inlet can reduce the ratio of single liquid phase flow in two-phase flow and increase the churn flow and fog flow region; When the LNG inlet flow rate increases，the bubble and slug flow areas decrease rapidly，and the churn flow area increases slightly. The increase of heat transfer coefficient on the outside surface of the tube can significantly increase the proportion of the churn flow. Compared with increasing LNG inlet temperature and inlet flow rate，the heat transfer efficiency of the ambient air vaporizers can be improved by improving the surface heat transfer intensity outside the tube.

Keywords: LNG; ambient air vaporizer; flow boiling; two-phase flow pattern; bubble behavior; surface heat transfer coefficient

GasVehicle，Ship andGasFuelingStation

BOGRecoveryProcess SchemeofLNGFillingStation

GAO Limin，YUAN Hui，GAO Wei

Abstract： Taking the BOG recovery process scheme of a three-stage LNG filling station technical renovation project as an example，the BOG quantity of LNG filling station and the BOG quantity of LNG tank truck are calculated，the process scheme is designed，and the process flow and main equipment are introduced. Suggestions: if the station area needs heating，BOG recovery skid can be set to recover BOG for heating and domestic hot water in the station; if the station area does not need heating，BOG will not be recovered. If the LNG filling station can be set to recover BOG in the station; CNG compressor can also be set recover BOG in the station. It is open to question whether the LNG filling station can recover BOG from external tank trucks. On the one hand，the general layout and traffic organization in the station should be considered; on the other hand，the equipment spacing should meet the specification requirements.

Keywords: LNG filling station; LNG tank truck; BOG recovery; BOG quantity

GasInformatization

InformationSecurity ofIoTIntelligentGasMeterSystem

SU Longfeng，WANG Binbin

Abstract： The information security framework of the IoT intelligent gas meter system is introduced. The information security of the IoT intelligent gas meter system is discussed from 4 dimensions of equipment security strategy (IoT intelligent gas meter，server environment and firewall)，platform application security strategy (HTTP/HTTPS，anti-crawler mechanism and data desensitization)，key system security strategy (system architecture，key life cycle，key generation and other management functions，and application scenarios of the key system)，IT operation and maintenance personnel standard management.

Keywords: Internet of Things (IoT); intelligent gas meter; information security; key system; operation and maintenance; security strategy

GasEnterpriseManagement

AMethodforQuicklyLocating LeakageofGasPipelineNetwork andDeterminingLeakageAmount

XING Linlin，XIE Donglai，QI Lirong，HAN Jinli

Abstract： A foreign method for rapid leakage location and leakage volume determination of gas pipeline network is introduced. The method was developed by the team of Professor Von Fisher from Colorado State University in the United States，and has been tested and applied in many cities in the United States. The equipment required by this method，leakage detection and location method，leakage quantification method and classification，research and development process and method verification process are discussed. The application prospect of this method in China is analyzed，and improvement suggestions are put forward.

Keywords: gas pipeline network; leakage detection; leakage point location; leakage quantification; rapid detection

AffordabilityofNaturalGasPrice forRuralCoal-to-gasUsersinBeijing

ZHAO Lichun，YAN Hongbo，WANG Ze，F(xiàn)ENG Jicheng，HAO Furong，LIU Xujing

Abstract： Besides the price of alternative energy (the main influencing factors of natural gas bearing prices determined by the isothermal bearing method)，residents' affordability of natural gas prices is closely related to their purchasing and consumption ability. Natural gas isothermal bearing method and expenditure limit method are adopted to evaluate the affordability of natural gas prices for rural coal-to-gas users in Beijing. The natural gas bearing price determined by the isothermal bearing method is 4.21 yuan/m3. Based on the disposable income per capita of urban and rural residents in Beijing in 2015，natural gas expenditure is considered at 5% of disposable income per capita，and the natural gas bearing price determined by the expenditure limit method is calculated to be 3.40 yuan/m3. The reason for the low natural gas bearing price determined by the expenditure limit method is that the disposable income per capita of residents is relatively low.

Keywords: rural area; coal-to-gas; natural gas price; affordability

InspirationofDomesticandForeign UtilityAccessonReformofGasService

SONG Yu，JIN Ying，TANG Yichun，YIN Xiaoping

Abstract： The existing problems of Shanghai gas access business environment are analyzed. The current status of domestic (Beijing and Shenzhen) non-residential customers' utility access and foreign (Tokyo，Singapore and UK) non-residential customers' gas access is discussed from the aspects of application materials，procedures，time，costs，and customer experience. The experience of utilities and administrative departments is summarized.

Keywords: gas access; business environment; gas service; utility access