Abstracts and Key Words

Smart Heating Columnof Harbin Institute of Technology Connotation and Goal of Smart Heating

FANG Xiumu, YANG Dayi,ZHOU Zhigang, LIU Jing

Abstract： The research on urban smart heating in China has just started, and there is still a lack of complete and correct understanding of the connotation and extension of smart heating. Intelligent heating is based on the heating physical equipment network, supported by the heating information Internet of Things. Through the intelligent decision-making system based on the intelligent heating platform, the auxiliary decision support is provided for the operation management personnel, forming a heating system form that reduces operating energy consumption while ensuring indoor comfort. Smart heating is a higher-level concept than intelligent heating. It makes full use of the form of creative thinking activities similar to those exhibited by the human brain to solve heating problems. Smart heating is based on the deep integration of digital, networked and intelligent information technology and advanced heating technology, takes the needs of users as the goal, takes low carbon, comfort and efficiency as the main characteristics, and takes self-perception, self-analysis, self-diagnosis, self-decision and self-learning as the technical characteristics. From the perspective of physical form, smart heating consists of three parts: physical equipment network, information Internet of Things and smart heating platform. The concept of smart heating contains the concept of intelligent heating. Smart heating is divided into generalized smart heating and narrow smart heating. The generalized smart heating is a new generation of heating technology which is based on people, with heating system as the carrier and information technology as the guide, and based on the deep integration of a new generation of artificial intelligence technology and advanced heating technology. The generalized smart heating includes narrow smart heating with information technology as the guide. The narrow smart heating consists of three parts: intelligent operation, intelligent management and talent cultivation. The overall goal of smart heating is: comfortable and satisfied users, safe and reliable system, efficient energy utilization and low carbon clean economy. The connotation of smart heating is discussed from the perspective of generalized smart heating and narrow smart heating, and the tasks and goals of each component of smart heating are also discussed. According to the actual situation in China, some suggestions on the way to realize the goal of smart heating are made. According to the analysis, the automation and informationization of heating system is the basis for the intelligentization of heating system. The intelligent levels of heating system can be divided into three vertical levels: primary intelligent system, constant intelligent system and open intelligent system. Smart heating is a new type of heating, smart heating technology is still not perfect, and the construction of smart heating is a gradual process. The historic opportunity brought by smart heating should be grasped to promote the collaborative innovation in production, education, research and utilization, and realize the innovative breakthroughs in heating technology and equipment. The construction of smart heating for enterprises should fully consider the balance between technical advancement and technical economy and formulate a reasonable smart heating construction scheme, and advance in stages and stratification.

Key words: centralized heating; smart heating; intelligent heating; heating system; goal; connotation

Goal of Smart Heating: to MeetHuman Thermal Comfort Needs

WANG Zhaojun

Abstract： Smart heating should aim at meeting human thermal comfort needs and provide comfortable indoor temperature for users. The concept of adaptive model for thermal comfort temperature of smart heating is proposed. As the core model of intelligent decision-making system, the adaptive model for thermal comfort temperature can be used to accurately predict heat load of heating system to realize the refined operation scheduling of heating system. According to the outdoor climate parameters, the severe cold area is divided into three heating stages. A new idea of using different room temperatures in different heating periods is put forward to meet human thermal comfort and adaptation needs. According to the thermal comfort requirements of different age groups in buildings with different functions in different heating stages, methods for constructing an adaptive model for thermal comfort temperature is proposed. The influence of high temperature on human thermal comfort and health is analyzed. From the time dimension and space dimension, how to set comfortable and healthy indoor temperature during winter heating period in the North China is discussed to achieve the goal of smart heating.

Key words: thermal comfort temperature; adaptive model; heating stage; thermal neutral temperature; smart heating

Construction of Heating IntelligenceEngines Based on Intelligent Algorithmsand Dynamic Simulation

ZHOU Zhigang, XUE Puning,LIU Jing, FANG Xiumu, ZHENG Jinfu

Abstract： Smart heating is a modern heating method based on district heating systems (DHSs) and an important direction for the future development of DHSs in China. As the cornerstone of smart heating, intelligent decision networks are crucial to achieve smart heating. Based on the effective integration of intelligent algorithms and dynamic simulation, a technical route to develop intelligence engines for DHSs is proposed. The application of intelligent algorithms and dynamic simulation in developing core modules of intelligent decision-making systems (optimization arrangement of monitoring points of heat-supply network, prediction of heat load, hydraulic simulation modeling and calibration of model parameters, thermal dynamic modeling and fault diagnosis of leakage of heat-supply network) is elaborated. This technical route can provide theoretical guidance for the development of intelligent decision networks.

Key words: smart heating; intelligence engine; intelligent algorithm; machine learning; dynamic simulation

Multi-step Ahead Recursive Predictionof Heat Load of Heating System Basedon Machine LearningXUE Puning, ZHOU Zhigang, JIANG Yi,CHEN Xin, FANG Xiumu, LIU Jing

Abstract： In order to predict dynamic profiles of short-term heat load for district heating systems (DHSs), a multi-step ahead recursive prediction strategy of heat load based on machine learning is proposed, which is an extension of the one-step ahead prediction model of heat load. The flow chart of multi-step ahead recursive prediction of heat load is introduced, which mainly consists of four steps: data preprocessing, data partitioning, model training, and model evaluation. Data preprocessing can be subdivided into three tasks, including feature selection, feature engineering, and feature scaling. In the model training, two machine learning models are introduced: support vector regression (SVR) and extreme gradient boosting (XGBoost). These two models are applied to build a one-step ahead prediction model of heat load, respectively. Based on these two trained prediction models, the dynamic profile prediction of short-term heat load can be achieved by using the proposed multi-step ahead recursive prediction strategy. In the case study, the operational data of the heat source in an actual DHS are selected as the data set. The research results show that the XGBoost-based multi-step ahead recursive prediction strategy outperforms the SVR-based multi-step ahead recursive prediction strategy in prediction accuracy and stability. Both two models are immune to the accumulation of errors at each time step. The proposed multi-step ahead recursive prediction strategy can accurately predict daily profiles of hourly heat load for DHSs.

Key words: district heating; heat load prediction; multi-step ahead prediction; machine learning

Study on Integrated Temperatureof Ambient Air

WANG Lei, FANG Xiumu

Abstract： Drawing on the integrated temperature of outdoor air, starting from the premise of direct measurement, taking the black temperature sensor as measuring element, comprehensive considering the outdoor dry bulb temperature, the visible short-wave radiation of the sun and the temperature sensor, the long-wave radiation of outer surface of the temperature sensor and the sky and surrounding objects, the ambient air integrated temperature is proposed for the operation adjustment of the heating system during the heating period. The theoretical calculation formula of the integrated temperature of ambient air is derived. The theoretical calculation results are compared with the measured value, the relative error between the measured value and the theoretical calculation results is checked, and it is determined whether the measured value can be used to replace the theoretical calculation results (that is, direct measurement of integrated temperature of ambient air). Under certain conditions, it is analyzed whether the measured value of the integrated temperature of ambient air is basically consistent with the change of the outdoor air integrated temperature, and the influencing factors affecting the different values. During the test, the average the theoretical calculation results of the integrated temperature of ambient air and the average value of the measured value are -5.11 ℃ and - 4.90 ℃ respectively, and the latter has a relative error of 4.1% for the former. The measured value of the integrated temperature of ambient air can replace the theoretical calculation results, and the integrated temperature of ambient air can be directly obtained from the measured value. In the case of cloudy days, the measured value of the integrated temperature of ambient air is basically consistent with the outdoor air temperature. In the case of sunny days, the measured value of the integrated temperature of ambient air and the outdoor air temperature increase with the increase of solar irradiance. The variations of the integrated temperature of outdoor air and the measured value of the integrated temperature of ambient air with time are basically the same. But when the time is the same, the values of the both are different. The main reasons are: the main bodies receiving the solar radiation are different, the main body receiving solar radiation for the integrated temperature of outdoor air is a large-area non-transparent envelope, and the main body receiving solar radiation for the integrated temperature of ambient air is a black surface temperature sensor; The integrated temperature of outdoor air ignores the long-wave radiation heat transfer of the outer surface of the envelope and the environment; when calculating the outdoor air temperature, the convective heat transfer coefficient of the outer surface of the enclosure does not consider the change with wind speed.

Key words: solar radiation; integrated temperature of ambient air; integrated temperature of outdoor air; operational regulation

Heat Source and Cold Source

Influence of Seepage on Soil TemperatureField and Heat Exchange Capacityof Ground Source Heat Pump

ZHANG Shan, ZHANG Bingbing, LIANG Ruobing

Abstract： In view of the problem that the soil heat imbalance causes the heat pump efficiency to decrease during the long-term operation of the ground source heat pump, the effects of groundwater seepage (hereinafter referred to as seepage) and the periodic operation of the heat pump on the surrounding soil temperature field and heat pump efficiency are investigated. A soil area with length and width of 40 m and depth of 140 m is established. Nine holes of 120 m depth with a center spacing of 5 m were drilled in the soil area, and they were arranged according to the 3×3 square array, double U-shaped buried pipes with a depth of 120 m were buried in the borehole. Based on the three-dimensional transient thermal-permeability coupled heat transfer model of the Feflow numerical simulation software, it is verified by the soil thermal response experiment that the results obtained by the Feflow software simulation are accurate and reliable. On this basis, the effects of absence of seepage, presence of seepage, change of seepage velocity (1×10-4m/s, 2.4×10-6m/s and 2.1×10-7m/s) and change of thickness of the seepage layer ( 5 m, 10 m and 15 m) on 120 days continuous operation of ground source heat pump under heating conditions are analyzed. According to the periodic operation mode of heating for 120 days, intermittent operation for 90 days, refrigeration operation for 90 days and intermittent operation for 60 days, the influence of ground source heat pump system on the temperature field of underground soil and the heat transfer per unit length of buried pipe is analyzed after 10 years of operation. The results show that the presence of seepage and the seepage velocity of greater than 1×10-7m/s are beneficial to recover the soil temperature around the buried pipe. Compared with the non-seepage condition, when the seepage layer is located at 38 to 42 m and the seepage velocity is 2.4×10-6m/s, the heat exchange capacity per unit length of the buried pipes after continuous operation for 120 days under heating conditions is increased by 54%. The seepage velocity has a significant influence on the heat exchange capacity per unit length of the buried pipes, the greater the seepage velocity, the more the heat exchange capacity per unit length of the buried pipes. When the seepage velocity is constant, the heat exchange capacity per unit length of the buried pipes increases with the increase of the thickness of the seepage layer, and for every 5 m increase in the thickness of the seepage layer, after 120 days of continuous operation under the heating condition, the heat exchange capacity per unit length of the buried pipes increases by 2 W/m. Under the periodic operation mode, there is no obvious cold and heat accumulation in the soil under the condition of seepage and non-seepage, but the seepage condition is more conducive to increase the heat exchange capacity per unit length of the buried pipes. At the end of the paper, there is a video showing the dynamic display of soil temperature field under seepage and non-seepage conditions, which can be watched by scanning QR code.

Key words: ground source heat pump; vertically burying pipe; numerical simulation; seepage; intermittent operation; Feflow software simulation

Application of MLP Neural Network toPrediction of Heating Indoor Temperature

PAN Shiying, DING Xin, CUI Yue,LYU Haozheng, WANG Tong, MA Lezhi

Abstract： Taking the heating users in Jinan City as the research object, using the heating medium flow, water supply temperature, return water temperature and outdoor temperature as input parameters, the indoor temperature prediction model based on MLP neural network is built by SPSS MODELER software, The construction of the predictive model and the results of the post-evaluation results are analyzed. The prediction effect verification result shows that the average relative error between the predicted indoor temperature and the measured indoor temperature is -2.27%, which basically meets the requirements.

Key words: MLP neural network; heating indoor temperature; prediction

Economy of Combined Heating of ElectricBoiler and Phase-change HeatStorage Heat Exchanger

CHEN Hongzhe, ZHU Neng, YANG Kun,YANG Shan, MA Shengming

Abstract： The process flow of combined heating system of electric boiler and phase-change heat storage heat exchanger (hereinafter referred to as the combined heating system) is introduced. Based on the load analysis, the equipment selection of the combined heating system (using only valley power) was carried out in a residential area with heating area of 5×104m2in Zhangjiakou. The net present value and dynamic payback period were selected as evaluation indexes to evaluate the economy of the combined heating system. When the heat price is calculated according to the central heating price of 29.55 yuan/(m2·year) for Zhangjiakou residents, and the valley electricity price is 0.15 yuan/(kW·h), the net present value of the combined heating system is 117. 93×104yuan/year, the dynamic payback period is 13 years, and the project economy is ideal. When the other conditions remain the same, and the service life is 30 years, the valley electricity price corresponding to the net present value of 0 is 0.168 yuan/(kW ·h), that is, the valley electricity price is 0.168 yuan/(kW·h), which is the critical electricity price of the economic feasibility of the scheme. When the valley electricity price is higher than 0.168 yuan/(kW·h), the heat price should be appropriately increased.

Key words: electric boiler; phase-change heat storage heat exchanger; economy analysis; sensitivity analysis

Technology and Economyof Cogeneration System UsingSteam Ejector

YU Honghao, LI Fei, XU Dinghua,SU Zhanhang, ZHAO Jian

Abstract： Combined with engineering examples, it is proposed to use a steam ejector (hereinafter referred to as an ejector) to recover waste heat from two generator sets with a rated power generation capacity of 660 MW. The medium-pressure cylinder is used for steam extraction, and the low-pressure cylinder is exhausted to improve the exhaust level of the low-pressure cylinder, thereby achieving stepwise heating of the return water of heat-supply network. The process flow and equipment selection of the cogeneration system are analyzed. For the typical heating period, the total coal consumption, the coal consumption for heating and the coal consumption for power generation of the cogeneration system during the heating period are measured. Taking the thermoelectric distribution system of the same scale (traditional coal-fired boiler room for heating, power plant for power generation) as the comparative object, the coal saving amount of the cogeneration system is calculated, and the coal saving amount of the cogeneration system is 87.32 × 104t.

Key words: cogeneration; steam ejector; waste heat recovery

Gas Combustion, Gas Appliancesand Gas Consumption Equipment Experimental Analysis of InfraredRadiation Spectrum of DomesticGas Cooking Appliance

GAO Naiping, AN Wei, WEI Dunsong, PENG Shini

Abstract： An experimental test method for distinguishing between atmospheric and infrared cooking appliances based on the spectral characteristics of flame radiation is proposed. The experimental test system was built by infrared Fourier spectrometer, and the radiation spectra of the three types of cooking appliances were tested and analyzed. The spectral characteristics of the three types of cooking appliances in the waveband of 2.5 to 15 μm were obtained, and the effects of different test modes and gas supply pressures on the test spectrum were studied. The infrared radiation spectra of atmospheric and infrared cooking appliances are only significantly different in the waveband of 2.5 to 10 μm. Only the vertical test mode can effectively distinguish the radiation spectra of the two types of cooking appliances. The radiation spectra of atmospheric and infrared cooking appliances have strong radiation peaks in two wavebands of 2.6 to 3.1 μm and 4.1 to 4.7 μm. In addition to the above-mentioned radiation peaks, the radiation spectrum of the atmospheric cooking appliance is weaker in other wavebands, and the energy emitted in these two wavebands exceeds 80% of the total radiant energy. In addition to the radiation of high temperature gas, the infrared cooking appliance is superimposed with a solid continuous re-emission heated by gas. As the gas supply pressure increases, the position of the flame spectrum radiation peak of the atmospheric cooking appliance does not change, and the spectral radiation force of the radiation peak increases. In addition to the increase of spectral radiation force of the radiation peak of the combustion gas, the infrared cooking appliance has a significant increase in the continuous radiation in the waveband of 3 to 10 μm. The accurate distinction between atmospheric and infrared cooking appliances, or the mixed and improved forms of the two types of cooking appliances should be comprehensively judged by the shape and structure of the cooking appliances, the combustion organization, and the spectral characteristics of the infrared waveband.

Key words: domestic gas cooking appliance; combustion diagnosis; infrared radiation spectrum; spectral experiment; radiation intensity; flame radiation

Influence of Environmental Factorsin Thermal Efficiency Test of GasCooking Appliance

WANG Xin

Abstract： According to the relational expression between the heat balance and the thermal efficiency of gas cooking appliance, the influence of environment factors on various heats in the heat balance is analyzed. The heat absorbed by water and pot is not related to environmental factors. When the ambient temperature rises, the gas temperature also rises, the chemical heat brought in by the gas decreases, and the physical heat brought in by gas and the physical heat brought in by the air become larger. Environmental factors have a negligible effect on the heat loss caused by incomplete combustion of the gas and the heat absorbed by the dissociation of polyatomic gases at high temperatures. Environmental factors have little effect on the physical heat taken away by the flue gas, and can be ignored. As the ambient temperature rises, the amount of heat released into the environment decreases. When the ambient temperature and gas temperature increase, the thermal efficiency of gas cooking appliance increases. The influence of the ambient temperature on the thermal efficiency of gas cooking appliance is greater than the influence of the gas temperature on the thermal efficiency of gas cooking appliance. The thermal efficiency test is carried out at the ambient temperature meeting the requirements of the standards. The thermal efficiency difference between the ambient temperature 24.83 °C and the ambient temperature 15.3 °C is 1.48%, which directly affects the energy efficiency rating of gas cooking appliance.

Key words: thermal efficiency test of gas cooking appliance; heat balance; environment temperature; energy efficiency rating

Gas Transmission, Distribution,Storage and Transportation

Medium-Low Pressure Gas IntelligentPressure Regulation System

LU Chao, CHEN Hailong, CHENG Xiaowei,PENG Guangjuan, ZHOU Ruizhi

Abstract： The composition of intelligent pressure regulator and medium-low pressure gas intelligent pressure regulation system is introduced. The medium-low pressure gas intelligent pressure regulation system is based on intelligent pressure regulator, and it is composed of pressure transmitter, valve position switch, inlet and outlet ball valve with valve position switch, PLC controller and so on. It has remote monitoring function and fault self-diagnosis function, flow simulation function and so on.

Key words: intelligent pressure regulator; intelligent pressure regulation system; remote monitoring; fault self-diagnosis; flow simulation

Numerical Simulation of Gas LeakageDiffusion in Gas Compartmentof Utility TunnelZHANG Chenghu, TIAN Guansan

Abstract： In order to analyze the leakage rate of the circular orifice of the gas pipeline, a gas compartment model with a length of 200 m, a width of 2 m and a height of 3 m was established. The mechanical air inlet and air outlet were respectively set at the two ends of the gas compartment, and the numerical simulation was performed by Fluent software. The law of gas leakage diffusion in the gas compartment is analyzed when the horizontal distances between the leakage hole and the air outlet are 0.1 m, 50 m, 100 m, 150 m and 199.9 m respectively. The farther the leakage hole is from the air outlet, the larger the diffusion range after gas leakage, and the higher the risk. The leakage diffusion area is mostly in an explosion hazard state. Suggestions to reduce the risk of gas compartment are proposed.

Key words: gas compartment; leakage diffusion; utility tunnel; numerical simulation

Liquefied Natural Gas Remote Monitoring Transformation Schemeof LNG Gasification Station

TAN Lina, LI Xinqiang

Abstract： The management mode of routine duty of LNG gasification station is introduced. Taking a chemical plant gasification station as an example, the existing problems during the operation are pointed out. The remote monitoring transformation scheme of the LNG gasification station is discussed. From the aspects of gasifier, pressure regulating system, liquid level monitoring, alarm system and remote transmission monitoring system, the remote monitoring degree can be improved, the duty time can be shortened, and the operation workers can be reduced.

Key words: LNG gasification station; liquid level monitoring; alarm; remote monitoring; on duty

Gas Source and Processing Utilization Numerical Simulation of StructureOptimization of Double TangentialCirculating Gas Distributor

CAO Jialu, ZHOU Junyi,TANG Jianfeng, SHI Ye

Abstract： Double tangential circulating gas distributor is widely used in packed tower because of its low pressure loss, good gas distribution effect, small entrainment of liquid foam and excellent comprehensive performance. However, there are some problems in double tangential circulating gas distributor, such as low local gas flow rate and obvious reflux phenomenon. Therefore, the comprehensive performance of gas distributor should be improved by structural improvement. The Fluent software is used to simulate the flow field distribution of the double tangential circulating distributor, and the reasons of the unevenness are analyzed. In the model, the inner diameter of the tower section is 6 000 mm, the inlet diameter is 1 220 mm, the height of inner cylinder is 1 500 mm, the width of annular roof is 500 mm, the height of the nearest guide vane from the flow distribution plate is 450 mm, and the height of other guide vanes is increased by 150 mm. The thickness of the inner cylinder, annular roof and guide vanes of the distributor is 10 mm, the width of the guide vanes and the flow distribution plate is the same as the width of the annular passage, and the height of the flow distribution plate is consistent with the height of the inner cylinder. Based on the upper end face of the distributor, the length of upper tower and lower tower is 2 500 mm, and this model is called the benchmark model. Based on the benchmark model, the air holes on the distributor roof are added, the width of the distributor roof is adjusted and the position of the distributor roof is adjusted, and the optimized internal flow field distribution is simulated to provide the direction for the structural optimization design of the distributor. Adjusting the width of the distributor roof can effectively reduce pressure loss of the distributor and improve gas uniformity. When the annular roof of the distributor is completely removed, the pressure loss and gas distribution unevenness of the distributor decrease by 29.24% and 15.90% respectively compared with the unadjusted, and the comprehensive performance of the distributor is obviously improved. Therefore, the removal of the distributor roof can be taken as an important direction for the structural improvement of the distributor. Opening holes in distributor annular roof can reduce pressure loss of the distributor to a certain extent and improve gas uniformity. The pressure loss of the roof and the gas distribution unevenness after opening holes reduce by 18.04% and 9.10% compared with no opening holes. Therefore, the opening holes in annular roof can be used as a reference direction for the structural improvement of the distributor. Adjusting the position of the distributor roof has a positive effect on reducing pressure loss of the distributor, but it has a limited effect on improving the effect of gas distribution. The pressure loss of the distributor and the gas distribution unevenness decrease by 13.27% and 4.62% respectively compared with the unadjusted, and the effect of this structural improvement method is not ideal.

Key words: packed tower; double tangential circulating gas distributor; numerical simulation; structure optimization; roof

Gas Enterprise Management Post-evaluation of LNG Reserve StationBased on G1 Weighting DeterminationMethod and Matter-elementAnalysis Method

LIANG Rui, ZHAO Liang

Abstract： The project post-evaluation index system of LNG reserve station of city gas is constructed from the aspects of goal realization, implementation process, production operation, economic benefit, social and environmental impact, sustainability and so on. G1 weighting determination method and matter-element analysis method are selected to construct a project post-evaluation mathematical model for LNG reserve station of city gas. The order relationship of evaluation index is determined according to G1 weighting determination method, the relative importance degree between adjacent evaluation indexes is assigned, and the index weights are calculated. The classical domain matter-element, the node domain matter-element and matter-element to be evaluated are determined. The correlation function value and membership vector are calculated, and the evaluation level is determined. The project post-evaluation of four LNG reserve stations of city gas is carried out combined with engineering cases.

Key words: LNG reserve station; project post-evaluation; G1 weighting determination method; matter-element analysis method