山东建筑大学毕业设计外文文献及译文外文文献：Sealed building drainage and vent systemsan application of active air pressure transient control and suppressionAbstractThe introduction of sealed building drainage and vent systems is considered a viable proposition for 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 the networks vertical stacks. This paper presents a simulation based on a four-stack network that illustrates 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 exercises 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 caution the initial results are highly encouraging and are sufficient to confirm the potential to provide definite benefits 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 equations cwave speed, m/s Dbranch or stack diameter, m ffriction factor, UK definition via Darcy h=4fLu2/2Dggacceleration due to gravity, m/s2 Kloss coefficient Lpipe length, m pair pressure, N/m2 ttime, s umean air velocity, m/s xdistance, mratio specific heats hhead loss, m ppressure difference, N/m2 ttime step, s xinternodal length, m density, kg/m3Article OutlineNomenclature 1. Introductionair pressure transient control and suppression2. Mathematical basis for the simulation of transient propagation in multi-stack building drainage networks 3. Role of diversity in system operation 4. Simulation of the operation of a multi-stack sealed building drainage and vent system 5. Simulation sign conventions 6. Water discharge to the network 7. Surcharge at base of stack 1 8. Sewer imposed transients 9. Trap seal oscillation and retention 10. Conclusionviability of a sealed building drainage and vent system1.Air pressure transients generated within building drainage and vent systems as a 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 engineers obsession with odour exclusion 2, 3 and 4, depend predominantly on passive solutions where reliance is placed on cross connections and vertical stacks vented to atmosphere 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 relieving reflections, and the multiplicity of 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 transients generated as random appliance discharges contribute 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 pressure falls to allow a relief air inflow and hence limit the pressure 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 transients generated remotely within the sewer system, possibly by some surcharge event downstreamincluding heavy rainfall in combined sewer applications. The development of variable volume containment attenuators 10 that are designed to absorb airflow driven by positive air pressure transients completes the 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 particular attention to be paid to the security implications of multiple roof level open 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 of AAVs the introduction of the PAPA device allows consideration of a fully sealed buildin