Necessity of Carrying out Hot Smoke Tests in Atrium with Examples

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Air temperature criterion was watched as roof sprinkler was installed for suppression of fire. Sprinkler heads at some positions will be thermally lagged. The smoke temperature is estimated to be in the order of 55.[pic 5]

The building information is listed as follows:

Headroom

>12m

Geometrical Dimensions

Irregular or Extraordinary Large Size

Floor Area

2,565 m2

Hall Void Volume

51,355 m3

Smoke Clear Height

Design Fire

2.8m with 7MW Fire Load

Set-up in HST

4.5m with 2MW Fire Load

Number of Fire Tray

6 A1 Size as stated in Table 2.3 of AS 4391-1999

Type of Test Fuel

Denatured Industrial Grade Methylated Spririt (Grade 95)

Quantity of Test Fuel

96 Litres

Number of Measuring Points in Thermocouples Tree

14 (0m, 2m, 4m, 6m, 8m, 10m, 12m, 14m, 16m, 18m, 20m, 22m, 24m and 26m)

Measuring Intervals

5 seconds

[pic 6]

Figure 1 – Smoke Layer Interface Height by Temperature Profile

By means of carring out HST, the performanceof the dynamic smoke extraction system installed in the expansion project at HKCEC could be evaluated. As shown in Figure 1, the smoke layer was formed at above 7m while the accepted value under 2MW fire was 5m. This shows the result was satisfactory.

- Evaluation of Smoke Extraction System

One of the reasons of using HST as requested by the Authority for the evaluation of performance of smoke extraction system in atrium is there are majority of the smoke extraction systems were designed by means of either simple empirical formula or CFD. Nonetheless, due to lack of experimental supports and justifications, the actual performance of such system is in doubt especially in different hall geometry such as irregular shape.

Moreover, there are lots of variable parameters affecting the results of smoke movement study with CFD. In Hong Kong, hot smoke tests are required in those spaces with room head higher than 2m, with irregular geometric shape or with a space volume bigger than 28,000m3. A fire set up with fire load bigger than 1MW has to be used. The elevation of the smoke layer interface was commonly judged by visual inspection. In order to preserve accuracy of the test, vertical temperature profiles would be evaluated and recorded at positions from the fire source for determination of clear height of smoke layer with statistic data support. The interface layer height can be determined at points with rapid changes of air temperature. Such practice on measuring vertical temperature profile was demonstrated to be necessary for big halls or atrium.

As to evaluate functionality of smoke extraction system in atrium, HST becomes one of the statutory tests required by HKFSD as a systematic study as well as statistic data support for the performance of such system.

- References[pic 7]

1. Technical Issues on Atrium Hot Smoke Tests. Chow, W.K. 2005.

2. Fire Services Department, HKSAR. FSD Circular Letter No. 2/2002, Hot Smoke Test on Smoke Extraction System. HKSAR : s.n., 2002.

3. Australia Standard. AS-4391 Smoke Managmenet Systems - Hot Smoke Test. s.l. : Standards Australia, 1999.

4. Fire Services Department, HKSAR. Codes of Practice for Minimum Fire Service Installations and Equipment and Inspection, Testing and Maintenance of Installations and Equipment. 2005.

5. Atrium Hot Smoke Test in HKCEC. Chow, W.K. s.l. : Research Centre for Fire Engineering, 2009.

6. NFPA. NFPA-92B Standard for Smoke Management Systems in Malls, Atria, and Large Spaces. s.l. : An International Codes and Standards Organization, 2009.

7. Atrium Hot Smoke Tests in a Big Shopping Complex. Chow, W.K., et al. s.l. : J. Applied, 2005-2006.

8. Performance Evaluation of Atrium Smoke Exhaust Systems with Hot Smoke Tests. Chow, W.K. 2009.

9. Use of Computational Fluid Dynamics for Simulating Enclosure Fires. Chow, W.K. pp.300-334, 1995, Vol. 13.

10. Determination of the Smoke Layer Interface Height for Hot Smoke Tests in Big Halls. Chow, W.K. 2008.

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