| The building drainage system not only affects the comfort of the living environment,but also poses a threat to the health of the occupants.The SARS virus in2003 and the COVID-19 in 2020 both indicate the possibility of virus and pathogens being transmitted by the building drainage system,which has attracted more and more attention.Due to the complicated influence factors of high-rise and ultra high-rise residential buildings,there are still many contradictions between the existing theoretical research and experimental results.The influence mechanism of ventilation and inner wall characteristics on drainage capacity is still unclear,leading to improprieties of the design and selection of drainage systems.Therefore,this thesis takes the drainage system of high-rise residential buildings as the research object,studies and analyzes the drainage transient characteristics of the drainage system of high-rise residential buildings through theoretical analysis and full-scale experimental methods.The research content and results of the thesis are as follows:Firstly,this article adopts a theoretical research method to study the mechanism and conditions of maintaining the safe and stable water-air two-phase flow inside the drainage stack after the water discharged from the horizontal branch.Based on Newton's second law,pipeline fluid mechanics,Bernoulli equation and energy equation,a pressure fluctuation influence model of critical drainage discharge rate was established under parameters changes including the ventilation mode,inner wall characteristics and building height.The dimensionless theoretical relationship between the water pressure limit value and the water seal loss value is derived.A physical model is established for the growth,deformation and rupture of air column under the cooperation of gravity and interfacial shear stress.Secondly,an experimental analysis of different vent pipe diameters and different lifting heights was performed in a vented drainage system at the 60-meter-high Xuanshi Tower in the National Building Drainage Piping Experimental Center in Gaoping,Shanxi Province.Under constant flow test method,the diacharge capacity of double stack drainage system with yoke pipe lift height 1.5 m,1.0 m and 0.5 m respectively are tested following the "Standard for Testing the Drainage Capacity of the Rise of Residential Living Drainage System".The lifting height of yoke pipe had a negligible impact on the maximum discharge capacity of the drainage system.The vent pipe diameters of DN50 and DN75 were tested separately.The full-scale experimental results show that the maximum discharge rate of a system with a larger vent pipe diameter is significantly higher than a system with a smaller one.Thirdly,the H-joint connected drainage system with a dedicated vent pipe was experimentally analyzed for different vent pipe bottom connection methods and different top vent styles.The experimental results show that the form of auxiliary ventilation installed on the first floor(the end of the vent pipe is connected to the horizontal main pipe)can greatly improve the diacharge capacity of the drainage system,and,in this system,the different ventilation methods at the top have no significant effect on the discharge capacity of the system.Fourthly,pipe offset experiments were performed on the double stack drainage system with anti-backflow H-joint.The experimental results show that the installation of S-shaped offset pipes for drainage stack and vent pipe will greatly reduce the discharge capacity of the system,reducing its maximum drainage flow rate by 69.23%.The S-shape offset pipe mainly affects the system pressure on the upper floors of the installation location,resulting in severe positive pressure fluctuation on the upper floors.Installing an anti-backflow H-joint above the S-shaped offset pipe can alleviate the positive pressure of the system to a certain extent.Fifthly,a comparative experiment of the vent pipe diameter,the connection method of the bottom of vent pipe,and the top ventilated methods was performed on the circuit ventilated drainage system.The experimental results show that different top ventilation methods have a great impact on the circuit vented drainage system.A standard circuit vent building drainage system with both ends of drainage stack and vent pipe vented to atmosphere has better performance than the systems with single pipe end vented system,namely the system with only vent pipe vented and the system with only drainage stack vented respectively.For the circuit ventilated drainage system with both extension vented,the vent pipe bottom connected to the horizontal main can double the water discharge capacity than the bottom connected the the drainage stack.The maximum discharge capacity of the drainage system in the case of vent pipe diameter DN100 is about 2.3 times of the case of vent pipe diameter DN50,and 1.2times of the case of vent pipe diameter DN75.DN75 is the most economical diameter for vent pipe in this circuit ventilated drainage system.In this paper,the limited pressure data,water seal loss data,discharge flow rate and ventilation flow data obtained from the experiment are recalculated to verify the air flow theoretical research method.The pressure fluctuation effect model fits the data well,from which it can be concluded that the pressure fluctuation in the drainage system is related to the system installation structure.The local head loss caused by different installation structures plays a vital role in the pressure fluctuation of the drainage system.The fitting results of dimensionless water seal loss and pressure limit value are more accurate.The fitting results show that there is a linear relationship between the pressure limit value and the dimensionless water seal loss in the negative pressure region of each system.The experimental data of each system indicate that the drainage system ventilation rates are linearly related to the drainage flow rates. |
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