建筑给排水中英文对照外文翻译文献_图文03

1、建筑给排水中英文对照外文翻译文献图文 03建筑给排水中英文对照外文翻译文献_图文 03建筑给排水中英文对照外文翻译文献（ 文档含英文原文和中文翻译）外文 :Sealed building drainage and vent systems an application of active air pressure transient control and suppression AbstractThe introduction of sealed building drainage and vent systems is considered a viable proposition for

2、 complex buildings due to the use of active pressure transient control and suppression in the form of air admittance valves and positive air pressure attenuators coupled with the interconnection of thenetwork's vertical stacks.This paper presents a simulation based on a four-stack network that i

3、llustrates flow mechanisms within the pipework following both appliance discharge generated, and sewer imposed, transients. This simulation identifies the role of the active air pressure control devices in maintaining system pressures at levels that do not deplete trap seals.Further simulation exerc

4、ises would be necessary to provide proof of concept, and it would be advantageous to parallel these with laboratory, and possibly site, trials for validation purposes. Despite this cautionthe initial results are highly encouraging and are sufficient to confirmthe potential to provide definite benefi

5、ts in terms of enhanced system security as well as increased reliability and reduced installation and material costs.Keywords: Active control; Trap retention; Transient propagation NomenclatureC+- characteristic equationsc wave speed, m/sD branch or stack diameter, mffriction factor, UK definition v

6、ia DarcyA h=4fLu2/2Dggacceleration due to gravity, m/s2Kloss coefficientLpipe length, mpair pressure, N/m2t time, sumean air velocity, m/sxdistance, mYratio specific heatsA hhead loss, mA ppressure difference, N/m2A ttime step, sAxinternodal length,mpdensity, kg/m3Article OutlineNomenclature1. Intro

7、duction air pressure transient control and suppression2. Mathematical basis for the simulation of transient propagation in multi-stack building drainage networks3. Role of diversity in system operation4. Simulation of the operation of a multi-stack sealed building drainage and vent system5. Simulati

8、on sign conventions6. Water discharge to the network7. Surcharge at base of stack 18. Sewer imposed transients9. Trap seal oscillation and retention10. Conclusion viability of a sealed building drainage and vent system1.Air pressure transients generated within building drainage and vent systems as a

9、 natural consequence of system operation may be responsible for trap seal depletion and cross contamination of habitable space 1. Traditional modes of trap seal protection, based on the Victorian engineer's obsession with odour exclusion 2, 3 and 4, depend predominantly on passive solutions wher

10、e reliance is placed on cross connections and vertical stacks vented toatmosphere 5 and 6. This approach, while both proven and traditional, has inherent weaknesses, including the remoteness of the vent terminations 7, leading to delays in the arrival of relievingreflections, and the multiplicity of

11、 open roof level stack terminations inherent within complex buildings. The complexity of the vent system required also has significant cost and space implications 8.The development of air admittance valves (AAVs) over the past two decades provides the designer with a means of alleviating negative tr

12、ansients generated as random appliance dischargescontribute to the time dependent water-flow conditions within the system. AAVs represent an active control solution as they respond directly to the local pressure conditions, opening as pressurefalls to allow a relief air inflow and hence limit the pr

13、essure excursions experienced by the appliance trap seal 9.However, AAVs do not address the problems of positive air pressure transient propagation within building drainage and vent systems as a result of intermittent closure of the free airpath through the network or the arrival of positive transie

14、nts generated remotely within the sewer system, possibly by some surcharge event downstream including heavy rainfall incombined sewer applications.The development of variable volume containment attenuators 10 that are designed to absorb airflow driven by positive air pressure transients completes th

15、e necessary device provision to allow active air pressure transient control and suppression to be introduced into the design of building drainage and vent systems, for both standard buildings and those requiring particularattention to be paid to the security implications of multiple roof level open

16、stack terminations. The positive air pressure attenuator (PAPA) consists of a variable volume bag that expands under the influence of a positive transient and therefore allows system airflows to attenuate gradually, therefore reducing the level of positive transients generated. Together with the use

17、 of AAVs the introduction of the PAPA device allowsconsideration of a fully sealed building drainage and vent system. illustrates both AAV and PAPA devices, note that the waterless sheath trap acts as an AAFig. 1. Active air pressure transient suppression devices to control both positive and negativ

18、e surges. Active air pressure transient suppressionand control therefore allows for localized intervention to protecttrap seals from both positive and negative pressure excursions. This has distinct advantages over the traditional passive approach. The time delay inherent in awaiting the return of a

19、 relievingreflection from a vent open to atmosphere is removed and the effect of the transient on all the other system traps passed during its propagation is avoided.2.Mathematical basis for the simulation of transient propagation in multi-stack building drainage networks.The propagation of air pres

20、sure transients within building drainage and vent systems belongs to a well understood family of unsteady flowconditions defined by the St Venant equations of continuity and momentum, and solvable via a finite difference scheme utilizing the method of characteristics technique. Air pressure transien

21、t generation and propagation within the system as a result of air entrainment by the falling annular water in the system vertical stacks and the reflection and transmission of these transients at the system boundaries, including open terminations, connections to the sewer, appliance trap seals and b

22、oth AAV and PAPA active control devices, may be simulated with proven accuracy. The simulation 11 provides local air pressure, velocity and wave speed information throughout a network at time and distance intervals as short as 0.001 s and 300 mm. In addition, the simulation replicates localappliance

23、 trap seal oscillations and the operation of active control devices, thereby yielding data on network airflows and identifying system failures and consequences. While the simulation has been extensively validated 10, its use to independently confirm themechanism of SARS virus spread within the Amoy

24、Gardens outbreak in 2003 has provided further confidence in its predictions 12.Air pressure transient propagation depends upon the rate of change of the system conditions. Increasing annular downflow generates an enhanced entrained airflow and lowers the system pressure. Retarding the entrained airf

25、low generates positive transients. External events may also propagate both positive and negative transients into the network.The annular water flow in thewet stack entrains an airflowdue to the condition ofno slip established between theannular water and air core surfaces and generates the expectedpressure variat