EnergyAustralia’s Sydney Central Business District (CBD) cable tunnel network will form a looprn6.2 km in length. The 3.2 km long, 3.5 m, diameter city east cable tunnel (CECT) currently in design,rnwill complete the loop in 2014. This paper discusses the ventilation design of the CECT, consideringrnoperation for four functions:rn1. normal (unmanned),rn2. access (manned),rn3. purge, andrn4. emergency fi re modes.rnThe dominant design criterion which determines the required ventilation capacity for CECT is thernspecifi cation of an upper air temperature limits of 35°C (dry bulb) and 24°C (wet bulb) for mannedrnaccess, during all ambient weather conditions and cable heating loads. Simplistic static heat transferrnanalyses do not yield a suffi ciently accurate calculation of tunnel air temperature and humidity tornprovide a safe and yet economical design. The primary refi nement in the analysis discussed in thisrnpaper is associated with modelling of the system’s dynamic behaviour.rnOur means of analysis is through a thermo-fl uid-dynamic simulation of the interactions betweenrnthe diurnally and seasonally varying loads (cable heat generation, ambient air conditions andrngroundwater infl ow), tunnel airfl ow and the resulting tunnel air temperature and humidity. Thesernsimulations are validated using experimental data from the existing city south and city west cablerntunnels.rnFire life safety scenarios are also analysed and discussed in association with the ventilation design.rnVentilation strategies are developed for dealing with such emergency fi re situations.rnThe understanding and insight provided by the work offers the ability to optimise ventilation plantrnprovisions in future cable tunnels, particularly long and high energy density tunnels.
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