FDS5 Simulation Results for VESDA Performance in HKCEC 2MW Fire Test (For internal info only) AEG, Xtralis Jan. 2009

Objective Assess VESDA detection performance in the proposed HKCEC fire test Optimize VESDA system design, if required, to meet performance requirement from the fire consultant i.e. 90 sec response time in a worse case scenario

Test Building and Ventilation The atrium link area has dimensions as 81x92m, 15m high. The floor plan was shown below.

Test Building and Ventilation (cont.) Based on information received, following conditions have been retrieved with certain assumptions: The whole area is enclosed by walls; No natural and mechanical ventilations exist during the test; No openings on ceiling or wall, like doors and windows, will be considered; Materials for ceiling, walls and floor were assumed as concrete.

Current VESDA Design Total 8 VESDA VLP detectors were designed to protect the whole area; A typical detector covers 40x30m (dotted line in the drawing). Modelling investigation was conducted in this area for the typical VLP

VESDA System Parameters The typical VLP has 4 pipes with following parameters: –Installed 1.5m above floor –Pipe length: 4x55m approx. –Number of sampling hole: 4x5 (20) –Spacing: 7.3x7.3m –Average & max transport times: 32 & 57s –Thresholds: 0.05 and 0.2 % Obs/m as Alert and Fire 1, respectively

Simulation Domain A domain was set to cover an space as 30x38x15m, containing the area protected by the investigated VLP Except the wall at farthest end of sampling pipes, the other 3 sides are open. Resolutions of mesh in all directions are 0.2m.

The Fire Source & Locations 2MW liquid fire (methanol) was simulated; Fire source base 1x1m, 0.5m above the floor; 10s built-up time, then followed by constant peak HRR (2MW) Fire source locations (as marked in the drawing) –Location 1, far end of sampling pipe – worse case scenario; –Location 2, middle of 4 sampling holes (horizontally) – normal case scenario Assumption: the liquid fuel will be ignited first and then smoke (from a smoke machine) then be added in.

Predicted VESDA Performance VESDA’s response time is a sum of smoke propagation time (from the fire source travel to the sampling holes) and transport time (smoke travel inside the sampling pipe from the holes to detector) Estimated VESDA Fire1 alarm times are: –Worse case: 52s –Normal case: 41s Reasons for the predicted response time shorter than the max transport time inn the worse case scenario: –The fire source next to the wall; –Smoke from the 2MW fire propagates quick than travelling inside the pipe; –Smoke reached at multiple holes.

Limitations of the Predictions Actual VESDA system parameters; Variation of the fire source, combustion profile and location; Air flow and ventilation on the site; Accuracy of FDS modelling (+-20%) Conduct transport time test during the commissioning. Check/adjust the pipe network if the measured values are 20% greater than the computed.

Illustration – Obscuration Distribution Normal Case (Location 2) Worse Case (Location 1) At 10 secAt 30 sec Note: Black colour, 1%/m; Red colour, 10%/m.

Conclusion Within the proposed VESDA system design, simulation conditions, and all the assumptions, the testing objective for VESDA system CAN be achieved.