Heat Source and Cold Source

Study on Thermal Performance of Heat Engine and Heat Pump Combined Cycle with Pre-injector

ZHANG Chenghu，LIN Jiyou，TAN Yufei，LI Yaping

Abstract: In order to solve the contradiction between the net power generation efficiency and the comprehensive thermal economy of the traditional waste heat recovery power generation system，the organic Rankine cycle is combined with the jet heat pump，and the jet heat pump system is arranged on the inlet side of the organic Rankine cycle expander． The combined cycle of engine and heat pump with pre-injector is proposed． This system can supply heat to the heat user under the condition of ensuring power output． The influence of the main parameters of the system on the net power generation efficiency and system economy is studied． The performance limit of the combined cycle in the heat priority mode and the power priority mode is analyzed． The results show that when the net power generation efficiency and net power generation of combined cycle are better，the dynamic investment recovery period of the system is poor，and the optimal condensing pressure makes the system dynamic investment recovery period optimal． Compared with the basic ORC，under the premise of ensuring the economic benefits of cold sources，the power priority mode of the combined cycle can increase the power output capacity by 18．62%，the heat source utilization efficiency by 19．29%，and the exergy efficiency to 34．87%． Under the heat priority mode，the combined cycle can heat the cold source from 15 ℃to 59．38 ℃． When the combined cycle externally outputs 40 ℃/60 ℃secondary circuit hot water，the net power generation of the system is reduced by 3．8%，and the heat source utilization efficiency is increased by 30．66%．

Key words: waste heat power generation; combined cycle power generation; organic Rankine cycle;jet heat pump; parameter analysis

Influence of Distance between Glass Cover Plate and Photovoltaic Panels on Performance of PV/T System

ZHOU Qingshan，ZHANG Zhigang

Abstract: Through the thermal equilibrium analysis of photovoltaic panels and glass cover plate in PV/T system，the influence of the distance between photovoltaic panels and glass cover plate on the photothermal efficiency of PV/T system is discussed． According to the typical annual meteorological parameters in Tianjin，the heat dissipation and photo-thermal efficiency of photovoltaic panels in PV/T system are calculated under different distances between the panels and the plate and different photovoltaic panels temperatures，and the calculation results are analyzed． As the distance between the panels and the plate becomes larger，the photo-thermal efficiency of the PV/T system begins to increase rapidly． After reaching the maximum value，as the distance between the panels and the plate continues to increase，the photo-thermal efficiency decreases，and decreases to a certain extent and then increases． The trend of heat dissipation of photovoltaic panels in PV/T system is reversed． For the two photovoltaic panel temperatures (40 ℃and 50 ℃) ，the optimum distance between the panels and the plate decreases as the photovoltaic panel temperature increases． The optimum distance between the panels and the plate is 6 cm when the photovoltaic panel temperature is controlled at 40 ℃，and the optimum distance between the panels and the plate is 5 cm when the photovoltaic panel temperature is controlled at 50 ℃． Since the adjustment of distance between the panels and the plate can be easily realized，selecting a suitable distance between the panels and the plate has practical value for improving the photo-thermal efficiency of the PV/T system．

Key words: integrated photovoltaic/thermal( PV/T) system; distance between panels and plate;photo-thermal efficiency; glass cover plate; heat dissipation

Design and Economy of Wind Power Heating System Using Electrode Boiler

NIU Chuankai，LI Zhengwei

Abstract: Taking a heat source plant with heating area of 100 ×104m2in Gansu area ( mainly usingwind power for heating，using low-valley electricity for most of the heating period) as the research object，the equipment selection is performed based on load analysis． The process flow，the operation mode and the formulation of electricity price and heat price are introduced，and the economic evaluation and sensitivity analysis of the project are carried out． The heat source plant uses a combined heating system of the high-voltage electrode boiler with the additional hot-water heat storage device ( heat storage tank) ． According to the principle that the electrode boiler only operates during the low-valley electricity period ( that is，the total heat demand of the users in a typical day during the heating period is generated by the electrode boiler during the low-valley electricity period) ，and the heat demand of the users is borne by the heat storage tank during the off-peak electricity period，the design heat power of the electrode boiler and the effective volume of the hot water storage tank are calculated and selected． Adopting the multilateral trading method，the heat source plant low electricity price ( transferred by the wind power station based on the original low valley price) is set at 0．014 yuan / ( kW · h) ，and the heat price ( heat price sold by the heat source plant to the heating company) is set at 27 yuan/( m2·a) ． At this time，the dynamic payback period of the project is 9． 85 years，with a certain profit space． The transfer range of wind power station to the low-valley electricity price of the heat source plant is the most sensitive factor affecting the dynamic payback period，followed by the heat price．

Key words: wind power heating; electrode boiler; heat storage device; economic evaluation; sensitivity analysis

Building Heating，Air Conditioning Ventilation and Thermal Environment Experimental Study on Heat Transfer Performance of Passive House Radiant

Floor in Severe Cold Area

JI Yuchen，WANG Zhaojun，SU Xiaowen

Abstract: The experimental study on the heat transfer performance of a passive house model floor in Harbin area was carried out． The passive house is a ceiling radiant heating． The supply and return water temperature，the inner surface temperature of the building envelop and the air temperature were tested． The radiative heat transfer coefficient and surface heat transfer coefficient，radiant heat flux density，convective heat flux density and total heat flux density of the ceiling and the ground were calculated． The experimental model room is located on the third floor，only the south wall is the outer wall，the outdoor air temperature ranged from -8．9 to -2．1 ℃，and the supply water temperature ranged from 30．0 to 31．6 ℃． The experimental results show that when the outdoor temperature was-2．1 ℃，the neighbors were heated normally，but the model was not heated，the indoor air temperature can reach about 21 ℃． After the heating was turned on，the supply water temperature rose by 1 ℃in the range of 30．0 to 31．6 ℃，and the indoor air temperature rose by 1．3 ℃． The radiative heat transfer ratio was about 91．5%． In the calculation of the radiative heat transfer amount in the ceiling，the total heat flux density can be estimated based on the radiant heat flux density． The radiative heat transfer coefficient and the surface heat transfer coefficient increase with the increase of the supply water temperature，and the radiative heat transfer coefficient is one order of magnitude higher than the surface heat transfer coefficient． In ceiling radiant heating，the total heat flux increases with the rise of the ceiling surface temperature ( or supply water temperature) ． There is a strong linear relationship between total heat flux density and ceiling surface temperature．At the end of the paper，a video showing an application example of a passive house in a severe cold area is attached，which can be watched by scanning the QR code．

Key words: ceiling radiant heating; convective heat transfer; radiative heat transfer; heat flux density;dynamic heat transfer performance of floor; passive house

Research Progress on Heating with Direct-expansion Solar-assisted Heat

Pump System

MA Hui，YANG Fan Abstract: The characteristics，composition and working principle of the direct-expansion solar-assisted heat pump ( DX-SAHP) system are introduced． The differences between the system and conventional heat pump systems are analyzed． The common forms of DX-SAHP system for heating are elaborated． Combined with the research examples at home and abroad，the thermal performance and advantages of different forms of heating systems with DX-SAHP system in different regions are analyzed． Problems to be solved further in the DX-SAHP heating technology and economy are pointed out，and the research directions for strengthening solar collector-evaporator research，coupling heat storage technology and making full use of solar energy are proposed．

Key words: direct-expansion solar-assisted heat pump ( DX-SAHP) system; heating; solar radiation energy; thermal performance; economy

Gas Combustion，Gas Appliances and Gas Consumption Equipment

Integrated Condensing Heat Exchanger Suitable for Chinese Market

ZHONG Jiasong

Abstract: Fully premixed condensing gas heating and hot water combi-boilers widely used in EU countries adopt stainless steel coil heat exchangers ( integrated condensing heat exchanger) ． When used in China，stainless steel coils are clogged and corroded．The reasons are analyzed，and the integrated condensing heat exchanger suitable for the Chinese market is proposed，and the actual use effect is measured． The fine fly ash produced by gas combustion and the dust and sediment carried by gas and air collide and adhere under the action of acid condensate，which eventually leads to blockage of stainless steel coil． With the blockage of the gap between the stainless steel coil，drainage of acid condensate is hindered，resulting in increased concentration，which eventually leads to corrosion of the stainless steel coil surface． Overall considering the structures of stainless steel coil and finned tube，the advantages of both are combined，and stainless steel finned coil is developed to ensure that the particles in the flue gas can smoothly pass through the gap between the stainless steel finned coils，thus alleviating the occurrence of blockage and corrosion． The prototype of the fully premixed condensing gas heating and hot water combi-boiler with stainless steel finned coil heat exchanger ( hereinafter referred to as prototype) has been used for 2 years，the thermal efficiency of the prototype has been reduced，the carbon monoxide emission volume fraction and nitrogen oxide emissions index both have been increased slightly，but the overall performance is still ideal． The fin surface of the stainless steel finned coil has only a small amount of dust deposited，and there is no obvious local corrosion and blockage．

Key words: full premix; condensing gas heating and hot water combi-boiler; integrated condensing heat exchanger; coil heat exchanger

Numerical Simulation of Condensing Heat Exchanger of Gas Heating and Hot Water Combi-boiler

LIANG Zhancheng

Abstract: For condensing heat exchanger of gas heating and hot water combi-boiler ( shell and tube heat exchanger，flue gas shell，water tube，corrugated heat exchange tube) ，F(xiàn)luent software is used to simulate the flue gas temperature field，heat transfer coefficient，inlet and outlet flue gas pressure drop of condensing heat exchanger under different flue gas inlet angles，and according to the simulation results，the best flue gas inlet angle is analyzed． When establishing the geometric model，two cases are considered on the inner wall of the condensation heat exchanger shell，one is the plane inner wall，the other is the corrugated inner wall ( hereinafter referred to as the plane inner wall heat exchanger，the corrugated inner wall heat exchanger) ． There are flue gas retention zones on the right side of the two heat exchanger flue gas inlets ( away from the outlet side) ． Since the corrugation fills the gap between the heat exchange tube and the shell，the corrugated inner wall heat exchanger does not have the flue gas short circuit of the heat exchanger with plane inner wall ( part of the inlet flue gas does not exchange heat with the cold water in the tube，and flows to the flue gas outlet) ． The flue gas temperature at the outlet of the corrugated inner wall heat exchanger is significantly lower than that of the plane inner wall exchanger，indicating that the heat transfer performance of the corrugated inner wall heat exchanger is better． The heat transfer coefficients of the two heat exchangers increase with the increase of flue gas inlet angles． Under the condition of the same flue gas inlet angle，the heat transfer coefficient of the corrugated inner wall exchanger is greater than that of the plane inner wall ex-changer． The pressure drop of the two heat exchangers increases with the increase of the increase of flue gas inlet angles． Under the condition of the same flue gas inlet angle，the pressure drop of the plane inner wall heat exchanger is less than that of the corrugated inner wall exchanger． The optimum flue gas inlet angles of the plane inner wall exchanger and the corrugated inner wall heat exchanger are 15° and 30° respectively．

Key words: gas heating and hot water combiboiler; condensing heat exchanger; heat transfer coefficient; flue gas pressure drop; flue gas inlet angle

Gas Transmission，Distribution，Storage and Transportation

Design of BOG Recovery System in City Gate Station

TANG Weihua

Abstract: As a gas storage and peak-shaving facility，LNG facilities are widely used in city gate stations． In response to the BOG recovery problem，the process flows of the LNG gasification station and the LNG filling station in the gate station are modified． The existing water bath-type BOG heater is used，and the buffer tank and BOG compressor are added． The overall scheme，process flow and equipment selection of BOG recovery system are put forward，and the static investment payback period of the modification project is analyzed．

Key words: gate station; BOG recovery system; LNG gasification station; LNG filling station;BOG compressor

Liquefied Natural Gas

Design and Research of V-type No-ballast Water Small LNG Carrier

HU Qinghua，LIU Jianshuo

Abstract: Marine ballast water causes marine pollution and invasion of alien species，which will bring serious environmental problems to the sea areas and cause the spread of parasites and pathogens． In order to realize the non-ballast water operation of small LNG carriers，referring to the design concept of Japanese Vtype non-ballast water ship，combined with the structural characteristics of the small LNG carrier C-type cargo tank and the specification requirements of LNG carriers，the design of V-type hull，double engines and double propellers，and double-layer bottom double-layer shell is adopted． Taking the 2 ×104m3LNG carrier as an example，the linear design，liquid cargo system design and power system design are discussed． The operation method of the ship to meet the navigation requirements is introduced，and the development prospects of the non-ballast water LNG carrier are analyzed．

Key words: V-type ship; non-ballast water ship; small LNG carrier; LNG cargo system; C-type independent cargo tank

Calculation of Relief Valve Back Pressure

and Natural Gas Release Pipeline

at LNG Plant Station

LI Jianxun，XING Shaojun

Abstract: The determination of back pressure of relief valve should be related with the natural gas release pipeline． The BWRS equation is used to establish the mathematical model． The equations are constructed by the pressure relations of each pipeline，the temperature relations of each pipeline，the specific enthalpy relations of the initial and end nodes，and the pressure relations of the end nodes． Newton-Laffson method is used to solve the problem，and the density，temperature and pressure of each node are obtained． Furthermore，it is analyzed that the back pressure of the relief valve is determined by many factors，such as the amount of release，the composition of natural gas，the pressure and temperature of natural gas in front of the relief valve，the ambient temperature，the length and diameter of each section of the release pipeline．

Key words: relief valve; back pressure; release pipeline; EAG heater; BWRS equation; LNG storage tank

LNG Investment Operation Scheme and Economic Analysis

LIU Chunming，WU Mouliang，LI Juan，CHEN Jinfang，CAI Lei

Abstract: The investment operation scheme of cooperation with existing coastal LNG terminal to build storage tanks and distribution of through pipeline transportation，tank trucks and small LNG ships is discussed，and economically compared with the conventional LNG business model． The economy of two transportation modes，LNG tank trucks and small LNG ship transportation is compared and analyzed． In the case of a fixed transportation distance and a certain construc-tion scale，the average total cost of the proposed scheme is 0．447 yuan/m3，while that of conventional LNG business model is 0．82 yuan/m3． Self-construction of facilities such as coastal LNG storage tanks can avoid the cost and part of the window period，and the economy has been greatly improved． Under the condition that the transportation distance of LNG tank trucks and small LNG ship transportation is both fixed at 550 km，when the annual transportation volume of small LNG ships is 19．57 ×104t，the two modes of transportation are economically equivalent; when the annual transportation volume is less than 19．57 ×104t，the economy of tank trucks transportation is better than that of shipping． Under the condition that the annual turnover of coastal LNG storage tanks is 200 ×104tons，and the annual transportation volumes of LNG tank trucks and inland river small LNG ships are 40 × 104tons and 50 ×104tons，respectively，the transportation of small LNG ships has a remarkable economic advantage as the transportation distance exceeds 252 km．

Key words: LNG terminal; inland river LNG transportation; small LNG ship transportation; tank truck transportation; economy

Gas Source and Processing Utilization

Waste Heat Recovery System and Simulation Analysis of Large and

Medium-sized Biogas Project

YANG Boran，CHEN Zhiguang，QIN Chaokui

Abstract: According to the research on mesophilic fermentation system of large and medium-sized biogas project，the total heat consumption was calculated according to the meteorological conditions in Harbin and other regions． On this basis，in order to reduce the heat loss of the biogas tank discharge，a waste heat recovery system for sewage source heat pump was designed． The Dymola software was used to simulate the waste heat recovery efficiency of the system model，and the working conditions of the sewage source heat pump throughout the year were evaluated． For the Harbin area，the COP of the sewage source heat pump system is 2．7 to 3．0，and the superheat degree is about 3 K in the feed and discharge cycle with a period of 4 h． The heat pump system works stably，and the heating performance coefficient is high． For the Harbin area，from November to March，the auxiliary heat source needs to be opened always; from June to August，the compressor partial load operates; in April，May，November and October，the opening time of auxiliary heat source is determined according to the total heat consumption and heat pump heating capacity． In the Harbin area，when heat pump system with compressor power of 20 kW is used，the total heat consumption can be compensated by 72% in coldest January，but the hourly non-guarantee rate is relatively high，and an auxiliary heat source is required． When heat pump system with compressor power of 33 kW is used，the heating capacity and the total heat consumption are roughly the same，which can basically meet the mesophilic fermentation，but the heat provided by the heat pump is more than twice the amount of heat required in June to August，and the COP is lower than the compressor power of 20 kW．

Key words: biogas project; heat pump system simulation; waste heat recovery of discharge; mesophilic fermentation

Gas Engineering Construction and Development

Green Development Concept of Urban Gas Municipal Infrastructure

GAO Wenxue，YANG Lin，LI Yanqiang，

WANG Yan，XU Shaojie

Abstract: In order to accelerate the green development process of urban gas supply projects，the green development concept of urban gas municipal infrastructure is discussed． China＇s green development concept and its application research in various industries are introduced，the evolution process of major gas sources of urban gas at home and abroad is summarized，and the development history of the urban gas municipal infrastructure is expounded． The vision of urban gas municipal infrastructure is presented: through scientific and technological innovation，developing and popularizing new technologies of urban gas supply engineering，improving gas utilization efficiency，promoting economic construction and ecological environment coordinated development，promoting gas production and consumption revolution，and constructing a clean，lowcarbon，safe and efficient urban gas supply system． The development goals of urban gas municipal infrastructure under the concept of green development are put forward: proposing the green evaluation index of urbangas supply project in accordance with the national conditions in China，and constructing the technical index system of urban gas municipal infrastructure; promoting the standardization of green evaluation of urban gas municipal infrastructure; gradually realizing the green construction，green technology application and smart management in the whole life cycle of urban gas supply engineering planning，design，construction and operation; paying attention to material recycling，speeding up the sustainable，comprehensive and complementary application of renewable energy and other new energy sources，promoting the interconnection of urban gas supply network，and realizing the high efficiency utilization of urban gas supply． The basic attributes of urban gas municipal infrastructure are defined: clean low carbon，guaranteed supply，safe and reliable，cost-effective，and intelligent control．

Key words: urban gas; municipal infrastructure; green development concept; vision; development goal; basic attributes

Gas Enterprise Management

Five-step Cycle Method for Urban Gas Pipeline Integrity Management

ZHANG Wanjie

Abstract: The concept，historical evolution，technical standards and characteristics of urban gas pipeline integrity management are explained． The difference between urban gas pipeline and long-distance pipeline is clarified． The process of urban gas pipeline integrity management is given． The key steps of five-step cycle method suitable for urban gas pipeline integrity management are analyzed，namely data collection and management，unit identification，risk assessment，risk control and effectiveness evaluation．

Key words: urban gas pipeline; long-distance pipeline; integrity management; five-step cycle method

Ways to Improve Welding Quality of PE Gas Pipe

QIAO Tao，XI Dan

Abstract: The product quality and performance of fully automatic welding machine of a gas company( including fully automatic hot-melt welding machine and fully automatic electrofusion welding machine) ，related personnel quality and operational standardization，welding record integrity，destructive testing and sampling scheme are investigated． The ways to improve the welding quality of PE gas pipeline are analyzed．

Key words: PE gas pipe; welding quality; fully automatic hot-melt welding machine; fully automatic electrofusion welding machine

Gas Standards and Codes

Inheritance and Reform of Mandatory Standards for Gas Engineering Construction in China

LIU Bin，LI Zheng，YAN Haipeng，LI Yanqiang，DU Jianmei，CHEN Yunyu

Abstract: The construction of a gas technical regulation system with Chinese characteristics，which is guided by laws and regulations，targeted by mandatory specification and supported by recommended standards，is the implementation path of China＇s gas engineering construction standards reform． The development process of mandatory standards for engineering construction is explained，and the problems existing in the mandatory standards for gas engineering construction are analyzed． Combined with the relevant contents of mandatory regulations for gas engineering construction，the positioning and function，the scope of application and the content structure of the full text mandatory specification and the relationship with the current standards are analyzed．

Key words: gas engineering construction; mandatory standards; reform; full text mandatory specification

Gas Informatization

Scheme of Gas Purchase and Sale Difference Management System

JIANG Zhaowei，ZHANG Haijun，

CUI Enhuai，XU Liang

Abstract: The management system of gas enterprise purchase and sale difference is built． It mainly includes basic data management，daily management，purchase and sale difference management and data query and analysis function module． The computing models and forecasting methods of purchase and sale difference，and historical data processing flow are analyzed．

Key words: purchase and sale difference; purchase and sale difference rate; management system