graduation project (thesis) opening report
(applicable to engineering and science majors)
subject name
subtitle
college (department)
professional
student name
XXXXXX, water supply and drainage engineering, School of Environmental Science and Engineering
2118
. Background of graduation project (thesis) (including literature review)
Since 1986, with the development of construction industry and the rapid development of building water supply and drainage specialty, it has become an indispensable and unique part of water supply and drainage.
during this period, the professional team has accumulated some experience and received professional training in design, construction and installation management personnel. In terms of technology, we have accumulated previous practical experience and learned from foreign new technologies, and the professional technology has made obvious breakthroughs and developments, especially the development of fire water supply system in building water supply and drainage. Organizationally, the National Building Water Supply and Drainage Engineering Standards and Technical Committee and the Building Water Supply and Drainage Committee of the Water Supply and Drainage Society of the Chinese Civil Society were established. In recent years, academic activities have been active and international technical exchanges have been strengthened. In 1996, the National Meeting of Young Engineers of Building Water Supply and Drainage was held, and the Sino-Japanese academic exchange meeting was held, and the international water supply and drainage conference (W PC) was attended to strengthen technical ties. In addition, the development of building water supply and drainage products and equipment in China also promoted the development of building water supply and drainage technology. The development of building water supply and drainage technology is related to scientific research, engineering practice (design and installation), product development and many other aspects. In recent years, the water supply and drainage of high-rise buildings are increasing day by day, such as Jinmao Tower (88 floors, 421m) and Shanghai World Finance Center (96 floors, 465m), which will be built in Pudong, Shanghai, promoting the development of water supply and drainage technology in buildings. In China, the basic work of scientific research in this field has been done less, but it has reached a certain level in work practice, especially in design. In product development, technology from advanced countries has also been continuously introduced. In order to organically combine the traditional water supply and drainage engineering with social sustainable development under the economic conditions of our country, our country is actively developing water industry as a new development of water supply and drainage engineering in the 21th century. It also requires the building water supply and drainage to be comfortable, hygienic, safe and reliable.
1 water supply
1. 1 water supply mode
In the water supply mode of residential quarters, it gradually develops into various forms. The traditional roof tank water supply system has the advantages of reliability and simplicity, reducing the peak value of water consumption to alleviate the contradiction between supply and demand of water, making full use of the pressure of municipal water supply network, saving investment and convenient maintenance. However, there are also some problems, such as easy pollution of water quality, insufficient water pressure, poor frost resistance, affecting the appearance of buildings and increasing structural load. According to the regulations of Shanghai, it is not appropriate to use water tank for multi-storey houses with a scale of more than 411 new residential areas, and water supply methods such as pools and pumps can be used.
in the water supply modes of high-rise buildings, there are generally series water supply modes and parallel water supply modes.
1. 2 pressurization facilities
In China's urban water supply network, the water pressure in the most unfavorable part of the network is ≮1. 1M Pa, and the water supply development speed of urban waterworks lags behind that of residential and public buildings. In addition, the aging of pipelines and the decline of pressure-bearing capacity require local pressurization and water storage and adjustment for most buildings. The commonly used pressurization facilities in China are water pump, pneumatic water supply equipment and variable frequency speed regulation water supply equipment, and the application of the latter two technologies has become increasingly mature.
1. 3 decompression method
In high-rise buildings, three methods are mainly used to vertically partition water supply: pressure reducing valve, water tank and water pump. At present, the most widely used is the pressure reducing valve, which overcomes the shortcomings of large land occupation, large noise, secondary pollution and high cost. In domestic water supply system, spring pressure reducing valve is usually used. The domestic water supply system requires the maximum hydrostatic pressure of sanitary ware to be ≯1. 6M Pa, the pressure of residential buildings, hotels, hospitals and other districts to be controlled at 1. 3- 1. 35M Pa, and the pressure of office buildings and other buildings that only move during the day to be controlled at 1. 35- 1. 45M Pa. In the fire water supply system, at present, proportional pressure reducing valves are mostly used to divide the fire water supply system in China. The hydrant water supply system controls the maximum hydrostatic pressure at the most unfavorable hydrant
≯1. 81M Pa, and the automatic sprinkler water supply system controls the working pressure in the pipe network ≯ 1.21mpa..
1. 4 water storage device
In the case of insufficient water supply from external pipe network, a reinforced concrete water storage tank is set, and white tiles should be laid on the bottom and inner wall. The regulating water tanks located on the roof are diversified in materials and processing methods, including galvanized, enamel, composite steel plates, and water tanks coated with plastic, glass fiber reinforced plastic and stainless steel, with the aim of overcoming the secondary pollution of water tanks, reducing the structural weight and inconvenient construction.
1. 5 water-saving technology
There are not many fresh water resources per capita in China, and water pollution makes water saving a very important task. In building water supply and drainage, it is mainly to promote water-saving accessories and waterways in buildings. Water-saving fittings include hydraulic flushing water tank fittings, second-gear flushing toilet fittings, counterweight reverse check valve of roof water tank, hydraulic multi-function valve and sanitary ware fittings for water supply, which can have the functions of current limiting, automatic temperature adjustment and high temperature limitation. The improvement of accessories also focuses on saving water and preventing water leakage. In the design of reclaimed water in buildings, sewage and wastewater are diverted, and the wastewater is reused after biochemical treatment, which is used for flushing toilet water and supplementing water with circulating cooling water. In order to save water and protect the environment, Beijing, Shenzhen and other cities in China have explicitly requested wastewater reuse.
1. 6 Design second flow calculation of domestic water consumption
From 1991 to 1995, China conducted a new study on urban domestic water consumption quota. The historical data of 55 cities and the test data of 77 residential quarters in China are collected, and the recommended values of domestic water consumption and comprehensive domestic water consumption of residents in different cities and regions are put forward.
Two formulas of square root and percentage of simultaneous use are given in Code for Design of Water Supply and Drainage in Buildings. In recent years, when the law of water use conforms to the characteristics of water use in developed countries, it is proposed to calculate the design second flow rate and hot water design second flow rate according to the American Hunt method (probability method).
1. 7 water supply by quality
In building a modern living residential environment and a high-quality living community, people put forward higher requirements for drinking water quality. In order to improve the quality of drinking water, our country initially treated drinking water by small household water purifier, and its main way was adsorption and filtration with activated carbon, but it was difficult to control the replacement of filter materials when it was used. In recent years, the concept of "high-quality drinking water" has emerged, which refers to water that can meet the quality standard of direct drinking water, including ultra-pure water, pure water, distilled water, mineral water and advanced treatment water. The source of high-quality drinking water comes from urban tap water or underground mineral water, and its treatment processes include ion exchange, ultrafiltration, membrane filtration, distillation, disinfection and sterilization. There are two ways of water supply: barreled supply and pipeline quality supply. Barreled supply is to set up centralized high-quality water supply stations in residential areas and send them to residents' homes or take them by themselves, which is the majority at present. A pipeline water supply system with different quality has been built in Shanghai residential district. The technology adopts ozone oxidation, activated carbon adsorption, pre-coated membrane fine filtration, micro-electrolysis and ultraviolet sterilization, which can remove organic substances harmful to human body, especially carcinogenic, teratogenic and mutagenic substances, while retaining minerals and trace elements beneficial to human body in water. High-quality drinking water is sent to every kitchen after purification, with variable frequency and constant pressure water supply system and circulation at the end of the pipeline.
1. 8 Vibration isolation and noise prevention
Some progress has been made in the vibration isolation technology of water pumps. In addition to horizontal pumps, the vibration isolation components of vertical pumps have been solved, and rubber isolators and spring isolators have been developed. Flexible rubber joints are also used in the water pump pipeline to prevent the transmission of vibration and noise < P >. Now, large-diameter soft joints, flexible elbows and reducer joints have been developed, which increase the functions of an accessory and facilitate the design, layout and installation of the pipeline.
on the outlet pipe of the water pump, it is required to install a silencing check valve and prevent water hammer and noise. The control of water flow velocity in domestic water supply pipe is that when the pipe diameter is less than or equal to ≤25mm, the water flow velocity is controlled at 1. 8 ~ 1.2m? s; When the pipe diameter >: At 25mm, the flow rate is controlled at ≯2. 1m? s。
2 hot water
2. 1 heating methods and equipment of hot water
the heating methods of hot water include direct heating and indirect heat exchange. Among the heating equipment using hot water boilers, there are mainly gas-fired hot water boilers and oil-fired hot water boilers. Generally speaking, the efficiency of primary heat exchange is higher than that of secondary heat exchange. At present, the fully automatic and efficient hot water boiler developed in China has basically solved the safety problem of hot water boiler located upstairs, so it is suitable for areas without heating pipe network in southern China. In direct heating, the use of solar energy has also made some progress. In the past two years, domestic hot water supply, heating methods and equipment have been discussed many times.
in the indirect heating mode, steam and hot water are the main heat media used. The theory of heat exchange equipment has been developed to a certain extent, and the concept of "turbulent heating" has been put forward for the design of volumetric water heating, that is, increasing the flow rates of heat medium and heated water to improve the heat release coefficient of heat medium to the pipe wall and the heat release coefficient of the pipe wall to the heated water to improve the heat transfer effect. In the secondary heating equipment, there are diversion type volumetric heat exchanger, semi-volumetric heat exchanger and semi-instantaneous heat exchanger. In the design, it has been realized that the safety and advancement of the equipment, as well as the one-time investment and floor space of the equipment, should be considered comprehensively to select the heating equipment reasonably and economically.
2. 2 design and calculation of hot water supply
in the place of comprehensive hot water supply, we have a reasonable understanding of the calculation of the maximum hourly hot water consumption. The calculation of heat medium consumption can reflect the relationship between hot water production capacity of outlet heating equipment, heating capacity of heat medium and heat storage capacity. There are also the maximum limit method for calculating the heat of the system and the simple calculation method for circulating water.
in the system design, attention should be paid to maintaining the balance and stability of water supply pressure and water temperature, so as to achieve the purpose of comfortable and economical water use. In the pressure balance of cold and hot water, attention should be paid to controlling the head loss, paying attention to the setting position of water heating equipment, and reasonably selecting the vertical partition of cold and hot water. In the control of stable water temperature, choose the appropriate automatic temperature regulating device of water heating equipment and handle the mechanical circulation system of hot water well.
2. 3 Energy saving in hot water system
The problem of energy saving in hot water supply system has been raised to a new position, and its energy saving measures include: increasing feed water temperature, reducing water temperature, adopting mixing faucet or thermostat, reducing heat loss, selecting high-quality insulation materials, improving heating mode, and selecting efficient heat exchange equipment.
2. 4 water quality treatment of hot water
is mainly to prevent hot water from scaling, damage equipment and pipelines, and reduce heat transfer efficiency. When the water consumption is large and the water quality is poor, the water quality of the centralized hot water supply system should be softened before heating. In addition to dosing treatment, electrostatic treatment technology, electronic treatment technology and magnetization treatment technology should be used to ensure the stability of hot water quality in circulation.
in addition, the problem of Legionella in hot water has also attracted attention. China has improved the volume and structure of water heaters or storage tanks, and adopted certain conditions to inhibit the growth of bacteria and Legionella.
3 drainage
3. 1 design theory of drainage riser water capacity
The popularization and application of plastic drainage pipes have deeply discussed the design theory of drainage riser water capacity. There are three viewpoints: one is the theory of gravity flow around water film, which assumes that the pressure fluctuation of water flow in the riser is not large and will not damage the water seal of the appliance, thus resulting in the load limit value of the design flow of the riser; The second is to deny the formula for calculating the gravity flow of circulating water film. Under the condition of circulating water film flow, the energy equation of riser airflow movement is established, and the resulting riser displacement results are contradictory. Thirdly, it is considered that the gravity flow state around the water film is a highly assumed water flow state for the purpose of flow calculation, which is conservative and feasible for calculation, but not comprehensive for establishing the energy equation of air flow movement. In this respect, there is still a lack of a large number of experiments and practices in China to verify it. The key to control the water flow capacity of the riser is the pressure in the riser, which is related to the above factors such as displacement, roughness coefficient of the pipe wall and water flow speed.
3. 2 Drainage and ventilation technology
The main purpose is to provide the escape of gas in drainage and achieve the function of ventilation; Prevent the negative siphon and positive splash of water seal in the drainage system to ensure the circulation of air; Keep the drainage smooth and quiet quickly. Its ventilation modes include internal (external) ventilation and through-conduction ventilation. The development of ventilation valve and single riser drainage system with special fittings has been carried out. The ventilation valve is used to supplement air and prevent the gas inside the pipeline from entering the room, and it is now in the stage of engineering practice. The design specification for the drainage system of special fittings single riser has been issued, and the water passing capacity of the riser has been increased and the number of risers has been reduced. But this product is now limited to cast iron products.
3. 3 Roof rainwater drainage problem
Through years of practical engineering experience, the roof rainwater drainage technology has been comprehensively understood and systematically studied. In the design, it is clear whether the water flow state in the pipeline system is pressure flow drainage or gravity flow drainage, and these two design methods are included in China's < P > Specification for Roof Rainwater Drainage Design.
3. 4 local treatment and disinfection of small domestic sewage
domestic sewage treatment equipment for buildings has been set up in a certain range in southern China, which also puts forward new requirements for the design of water supply and drainage for buildings. There are some differences between domestic sewage from buildings and urban sewage, and the discharge standard after treatment has its own characteristics. In the treatment process, contact oxidation, A2O method and SBR process are often used to reduce BOD, COD and ammonia nitrogen. The treatment structure can be located in the outdoor underground or underground room of the building, and the material is concrete, FRP or steel structure. Construction sewage treatment also needs to consider odor emission treatment.
In sewage disinfection, chlorine tablets are widely used in south China. In the northern area, chlorine dioxide synergistic disinfection device is used to produce ClO _ 2 mixed gas by electrolysis.
3. 5 sanitary ware
The improvement of living standard puts forward new requirements for sanitary ware, which pays more attention to comfort, reliability, quietness and energy saving, and now there are also various high-standard and leisure sanitary ware. A lot of knowledge abroad