Singapore Fire Safety Engineering Guidelines 2015_1.pdf

Annex c4 ii it computes the mass momentum and energy

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Annex C4
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(ii) It computes the mass, momentum and energy conditions of the fire conditions for each of the cell within the grid or mesh as a function of time. Like the zone model, no field model is the best for all applications. Most of the field models are based on the similar fundamental principles but there is a significant variation features among the different field models. Understanding of the assumptions and its limitations for the particular model is required in order to select the appropriate field model to be used. Again, most importantly, the selected model must be validated with results comparing experiment data. (iii) Application and limitations: (1) No constraint in using field model for any geometry (2) Detail analyses required (3) Experience users with knowledge of fluid dynamics codes (4) Powerful computer required to run CFD (5) Large data storage for results (6) Long computing time (7) Results are grid dependant; i.e. Solution is less ideal for coarser and very fine grids or mesh (iv) List of Approved Field Models: Fire Dynamic Simulator (FDS) FLUENT Phoenics To seek consensus from SCDF for the use of other field models Annex C5
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Annex D Notification time (a) The following describes typical design notification times, depending on the types of alarm systems present and the evacuation strategies being adopted: (i) From C/VM2 document Cl 3.2.2 t n = 30 s for premises adopting standard evacuation strategies; For non-standard evacuation strategies (i.e 2-stage, management investigating, etc), t n will have to take into account any extended timeframe. (ii) From PD7974 Part 6:2004 Annex A If the building is fitted with automatic fire detection systems with immediate fire alarm, then t n = 0 s; If the building is fitted with automatic fire detection system involving a pre- alarm to building management, and thereafter either (1) a manually activated warning sounded throughout affected area, or (2) if pre-alarm is not cancelled after a fixed delay, then a general alarm will be sounded. In such cases, the notification time can be taken as: t n = 2 min to 5 min + time taken for voice alarm to be spoken twice. If the building is fitted with only local automatic alarm near the fire location, or is not fitted with any automatic alarm at all, occupants will be notified of fire only via manually activated general warning system. In such cases, notification time may be long: t n = long and unpredictable. (iii) From SS CP10 : 2005 Cl 1.4.3.3 Fire extinguishing alarm initiating devices. Flow switches, pressure switches and the like associated with fixed fire extinguishing systems that are used to initiate an alarm, shall be individually connected under separate alarm zones on the fire alarm panel. Flow switches used shall incorporate time-delay devices to avoid false alarm due to water surges.
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