1、4687 Tests of Stairwell Pressurization Systems for Smoke Control in a High-Rise Building Ya n I i ng Wang ABSTRACT Field tests of stairwell and vestibule pressurization systems were performed in a 32-stovy high-rise building. Pres- sure diferences in the stairwell, and vestibule and average air velo
2、city were tested under various conditions. Test results indi- cate that indirectpressurization through a stairwell is feasible. Ignoring stack efect, the worst door-opening condition is that thejre doors of the top or bottom three adjoiningfloors of the building are open simultaneously. Pressurizati
3、on systems in combination with corridor smoke exhaust systems are advan- tageous in preventing the spread ofsmoke to the escape routes. Tests demonstrate that inappropriate stairwell and vestibule pressurization systems not only fail to ensure safe evacuation but also have serious safety issues. INT
4、RODUCTION Many field investigations have shown that smoke is recognized as the major killer in building fires. Researchers have conducted a study on the design of smoke-free escape routes with reliable techniques. Today, more and more coun- tries have fire codes that encompass stairwell and fire ele
5、vator vestibule pressurization systems (BS 1998; NFPA 2000). A huge amount of funding is being used in construction and maintenance of smoke control systems in high-rise buildings all over the world. Although the smoke control systems in high-rise buildings cost billions of dollars every year in Chi
6、na, the extent to which they are effective is still unknown. The reli- ability of pressurization system design data and actual opera- tion results, as well as the problems and consequences of smoke control system design, operation, and maintenance, need to be determined. Fusheng Gao TEST BUILDING In
7、 order to understand such problems, field tests were conducted in a high-rise building in Harbin, Heilongjiang Province, China. Tests demonstrate that not all smoke control systems in high-rise buildings ensure safe evacuation. Unsuit- able design can cause serious hidden danger. An oversized pressu
8、rization system may even hinder occupants from evac- uating safely. The tested building is a complex high-rise building including a four-star hotel and office rooms. The total construction area is 43,000 m2 (463,000 fi2). The building alti- tude is 114 m (374 ft). There is a total of 32 stones above
9、 ground and 3 stories below ground. The building has four parts. The first part, from the 1st to the 6th floor, is the “skirt part.” The second one, from the 7th to the 14th floor, includes hotel rooms. The third one, from the 15th to the 30th floor, comprises business offices. The last one, includi
10、ng the 3 1 st floor and the 32nd floor, has mechanical rooms. The typical floor plan of the tested building is shown in Figure 1. The schematic of the stairwells and vestibules is illustrated in Figure 2. The building has two smoke-preventing stairwells: Stairwell No. 1 and Stairwell No. 2. Stairwel
11、l No. 1 connects with Vestibule No. 1 (independent vestibule), and Stairwell No. 2 shares Vestibule No. 2 (joint vestibule) with the fire elevator. The area of each vestibule is approximately 9 m2 (97 fi2). The size of each stairwell door and vestibule door is 1 .O m by 2.0 m (3.3 ft by 6.6 fi). The
12、 fire elevator door is 1.5 m by 2.0 m (4.9ft by 6.6 ft). The effective leakage areas of each stairwell door (as well as vestibule door) and the fire elevator door are 0.0205 m2 (0.2207 fi2) and 0.0565 m2 (0.6082 ft2), respectively. Yanling Wang is a graduate student and Fusheng Gao is a professor in
13、 the School of Municipal and Environmental Engineering, Harbin Insti- tute of Technology, Harbin, Heilongjiang Province, China. 02004 ASHRAE. 185 Figure 1 Typical floor plan of the tested building. This building contains four pressurization systems: Stair- well No. 1, Vestibule No. 1, Stairwell No.
14、2, and Vestibule No. 2. Each stairwell pressurization system has a centrifugal supply fan with the capacity of 44,050 m3/h (25,920 cfm) on the 3 1 st floor. The fan supplies the outside air to the stairshaft through normally closed grilles in the vertical supply shaft on the -2nd (2nd underground),
15、Ist, 4th, 7th, loth, 13th, 16th, 19th, 22nd, 25th, and 28th floors of each stairwell. Each vesti- bule pressurization system has a centrifugal supply fan with the capacity of 36,700 m3k (2 1,600 cfm) on the 3 1 st floor. The vestibule of each floor is pressurized with air from the supply shaft throu
16、gh a normally closed grille on the wall of the vesti- bule. The smoke exhaust system has an exhaust fan with the capacity of 34,560 m3k (20,340 cfm) located on the 32nd floor, and exhaust grilles in the corridor of each floor. The schematic of pressurization systems and a smoke exhaust system is sho
17、wn in Figure 3, This building does not have a system for preventing overpressurization. CHINESE CODE FOR FIRE PROTECTION DESIGN OF TALL BUILDINGS (CCFTB) In the Chinese Code for Fire Protection Design of Tall Buildings (CCFTB) (Chinese Standard 1997), stairwellposi- tive pressure difference is defin
18、ed as the pressure difference between the stairwell and corridor, and vestibulepositivepres- sure diflerence is defined as the pressure difference between the vestibule and corridor. The code requires that the two posi- tive pressure differences be 50 Pa (0.2 in. H,O) and 25 Pa (O. 1 in. H20), respe
19、ctively. The average air velocity through any three open doors should be in the range of 0.7 ms (1.6 mph) to 1.2 m/s (2.7 mph) (Shavit et al. 1995; aote IS). 1 Vestibole No.1, 2 Smoke exhaust shaft, 3 Supply shaft for Vestibule No. 1, 4 Supply shaft for StiirweU No. 1, 5 Stairwell No. 1,6 Stairwell
20、No. 2,7 Vestibule No. 2, 8 Supply shaft for Vestibule No. 2,9 Supply shaft for SairweU No. 2,lO Fire elevator Figure 2 Typicaljloorplan of the stairwells and vestibules. Figure 3 Schematic of pressurization systems and smoke exhaust system. 186 ASHRAE Transactions: Research Table 1. Recommended Pres
21、surization System Airflow Rate Pressurization Airflow Rate Number of Supply Air System Condition Floors Served Injection Location (m3/h) (cfm) 20 Stairwell 25,000-30,000 14,700-17,700 20-32 Stairwell 35,000-40,000 20,600-23,500 20 Stairwell 16,000-20.000 9400-1 1,800 Stairwell pressurization system
22、alone Joint vestibule 12,000-16,000 7100-9000 Both stairwell and joint vestibule pressurization systems 20-32 Stairwell 20,000-25,000 1 1,800-14,700 Joint vestibule 18,000-22.000 10,600-13,000 20 Fire elevator vestibule 15,000-20,000 8800-1 1,800 20-32 Fire elevator vestibule 22,000-27,000 13,000-15
23、,900 Fire elevator vestibule pressurization system CCFTB also states that stairwell pressurization alone is enough if the stairwell links an independent vestibule. Both stairwell and vestibule pressurization systems are needed if the stairwell links a joint vestibule. Pressurization airflow rate can
24、 be calculated using Equations 1 or 2 or determined accord- ing to Table 1. Equation 1 is based on the requirement of posi- tive pressure difference in the escape routes. Equation 2 is based on average air velocity through the open fire door. If the calculated value does not agree with the value in
25、Table 1, the higher one is selected. measured, the selected section was divided into nine equal squares as measurement points. The objectives of the tests were (i) to understand and find the design and operation problems in the smoke control systems and (2) to study the relationship of the pressure
26、differ- ences in the stairwell and vestibule, and average air velocity and supply airflow rate, which will provide reference for improving the reliability of pressurization system design. Based on the objectives, the test was designed as the following two steps: where L, = A= AP= n= where L, = F= v=
27、 n= LI = 0.827 x A x x 1.25 x 3600 supply airflow rate, m3/h (ch) flow area (leakage area), m2 (fi?) pressure difference, Pa (in. H,O) exponent, n = 2 L, = F.v.nx3600 supply airflow rate, m3/h (ch) area of opened door, m2 (fi?) average air velocity, mis (mph) the number of opened doors CCFTB does no
28、t cover the methods for controlling overpres- sure. TEST DESCRIPTION The measured parameters in the test include airflow rate of the pressurization fan, supply air velocity through the grille, positive pressure differences in stairwell and vestibule, aver- age air velocity of the open door, inside t
29、emperature, and outside temperature. Each system supply airflow rate was measured in a steady airflow section on the horizontal straight duct after the fan. When supply airflow rate and average air velocity were 1. Constant Supply Airflow Condition. Keep the system unmodulated, and measure the airfl
30、ow rate and pressure differences in stairwells and vestibules to get the actual supply airflow rates and the pressure differences in stair- wells and vestibules. 2. Variuble Supply Airflow Condition. Modulate supply airflow rate, and measure the following parameters in Stair- well No. 1, Vestibule N
31、o. 1, Stairwell No. 2, and Vestibule No. 2: the pressure differences in the stairwells and vesti- bules with the fire doors closed, the pressure differences in the stairwell and vestibule and the average air velocity with the fire doors open, and the impact of smoke exhaust system operation on the p
32、ressure differences in the stairwells and vestibules and the average air velocity. A series of tests were conducted under nonfire conditions in September 2002. The outside air temperature was in the (1) (2) range-of 18.5“C to 22.7“C (657F to 73.3“F) and the inside air temperature was between 2 1.9“C
33、 and 25.4“C (7 13F and 78.1“F) during the field test. Therefore, the stack effect was ignored in the tests. TEST OF PRESSURE DIFFERENCES IN STAIRWELLS AND VESTIBULES Tests Under Constant Supply Airflow Rate 1. Stairwell No. I und Vestibule No. 1. Vestibule No. 1 only connects with Stairwell No. 1. W
34、hen the pressurization systems for Stairwell No. 1 and Vestibule No. 1 operate simultaneously, the pressure differences in the stairwell and ASHRAE Transactions: Research 187 Table 2. Pressure Differences in Stairwell No. 1 and Vestibule No. I Under Constant Supply Aimow Rate Floor Pressure Differen
35、ce Between Stairwell Pressure Difference Between Pressure Difference Between Stairwell and Vestibule Vestibule and Corridor and Corridor Pa (in. H20) Pa (in. H20) Pa (in. H20) Measurement Average Measurement Average Measurement Average 15th 155 (0.62) 134 (0.54) 289 (1.16) 16th 206 (0.83) 185 (0.74)
36、 133 (0.53) 125 (0.50) 339 (1.36) 310 (1.25) 17th 194 (0.78) 109 (0.44) 303 (1.22) the vestibule will be too high. Accordingly, only the pres- surization system for Stairwell No. 1 was operated in the tests. When the supply airflow rate was not adjusted, the actual supply airflow rate measured 46,24
37、0 m3/h (27,210 cfm) (design supply airflow rate) for the total or 1320 m3/h (780 cfm) for each floor. Table 2 lists the pressure differ- ences in the stairwells and vestibules of the 15th, 16th, and 17th floors when all the fire doors were closed. The results indicate: The positive pressure differen
38、ces were higher than the required value by CCFTB when Vesti- bule No. 1 pressurization system did not operate. The design pressurization supply airflow rate was high because the average pressure differ- ence between the stairwell and corridor was as high as approximately 300 Pa (1.2 in. H20). Even w
39、hen the pressurization system for Vesti- bule No. 1 did not operate, the pressure differ- ence between the vestibule and the corridor exceeded 100 Pa (0.4 in. H20). The result dem- onstrates that indirectly pressurizing the vesti- bule through the stairwell is feasible. During the measurement, the h
40、igh positive pres- sure difference made the fire doors in the stair- well and vestibule extremely difficult to open. Two people exerting full power could open only one door. If the Vestibule No. 1 pressurization system operates during a fire, the doors cannot be opened and, consequently, occupants c
41、annot be safely evacuated. 2. Stairwell No. 2 and Vestibule No. 2. The measured actual stairwell supply airflow rate was 41,340 m3/h (24,330 cfm) when the Stairwell No. 2 pressurization system was oper- ated with the design supply airflow rate. The average posi- tive pressure differences in the stai
42、rwell and vestibules in some floors were 75 Pa (0.30 in. H20) and 18 Pa (0.07 in. H20), respectively. Compared with Stairwell No. 1, the positive pressure differences of Stairwell No. 2 and Vesti- bule No. 2 dropped significantly. The main reasons are as follows: Although the Vestibule No. 2 pressur
43、ization system did not operate, the closed supply air grilles of Vestibule No. 2 obviously leaked. E- Pressore difference betwe& stainve and eonidor,Pa (BO) Pl- Pressore difference between vestibule and eomdor,Pa(.EO) E- corridor relative preawre Werenee, O Pa .EO) AlFPrR, Pressure difference betwee
44、n ehllwd and veslibule,Pa(inBiO) Figure 4 Pressure diferences with some grilles in Vestibule No. 2 open. Occupants frequently entered and left Stairwell No. 2 and Vestibule No. 2. The fire elevator was often run as a working elevator by the workers. Hence, the doors were loosely closed and partial s
45、upply airflow was lost. The positive pressure differences should be higher than the measured values if the above reasons did not exist. The results also show that the required pressure differences can be satisfied without the vestibule pressurization system if the stairwell pressurization system sup
46、plies a sufficient airflow rate. When the pressurization systems for Stairwell No. 2 and Vestibule No. 2 operated simultaneously, the vestibule posi- tive pressure differences immediately rose. Figure 4 presents some pressure differences under these conditions: (1) the supply airflow rate of Stairwe
47、ll No. 2 andvestibule No. 2 were 43,340 m3/h (25,510 cfm) and 34,110 m3/h (20,070 cfm), respectively, (2) all the fire doors were closed, and (3) the supply air grilles of the 15th, 16th, and 17th floors of the vesti- bules were open. The negative pressure differences between the stairwell and the v
48、estibule show that a large vestibule 188 ASHRAE Transactions: Research supply airflow rate will cause a higher positive pressure differ- ence in the vestibule than in the stairwell. The differences will then dnve air back to the stairwell. The average pressure difference was -31 Pa (-0.12 in. H20) b
49、etween the stairwell and vestibule of the three floors and 254 Pa (1 .O2 in. H20) between vestibule and corridor. If the corridor pressure was assumed to be zero, the average positive pressure differences in stairwell and vestibule were 223 Pa (0.90 in. H20) and 254 Pa (1 .O2 in. H20), respectively, which are much larger than the recommended values in CCFTB. It was found in the test that the large vestibule positive pressure differences caused the fire elevator door to stay open. Therefore, the fire elevator cannot be run as usual, and the vestibule fire door cannot be opened by one p
