Pressure Differential Systems

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Octavia Marshall
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1 Pressure Differential Systems German point of view to EN Considaration of the influence of aerostatic pressure differential in high rise buildings Dipl.-Ing. B. Konrath I.F.I. Institut for Industriel Aerodynamics GmbH Institut at the University of Applied Sciences Welkenrather Straße 120 Germany Aachen notified Test, Inspection and Certification Body no in accordance with Construction Products Directive October Miedrzyzdroje 1/22

Aerostatic pressure distribution aerostatic pressure difference inside/outside 150 140 130 120 110 100 building height (m) 90 80 70 60 50 40 30

2 Aerostatic pressure distribution aerostatic pressure difference inside/outside building height (m) winter 24/-20 C summer 24/35 C pressure (Pa) p therm = (ρ TR - ρ 0 ) g h TR (1) October Miedrzyzdroje 2/22

3 Aerostatic pressure distribution dp in-out eastside dp in-out westside dp theoretical flor ( - ) pressure difference (Pa) 0 measured and with equation (1) calculated pressure difference between staircase and ambient in a 38 storey tall building (ti = +20 C ta = 8 C) October Miedrzyzdroje 3/22

4 Aerostatic pressure distribution storey measured pressure differential (staircaise -ambient) pressure difference calculated from measured temperatures measuring points in staircase external measuring points pressure / Pa pressure differential between staircases and ambient for a 200 m high rise building (ambient temperature at ground level t = 5 C, measured and calculated (without wind influence) with equation (2)) October Miedrzyzdroje 4/22

5 Flow field around buildings Plate shaped high rise building, wind flow perpendicular to the longitudinal axis high suction on the leeward side due to flow displacement stagnation point in 2/3 of the height wake with strong three dimensional flow closing only in a large distance from the building strongly modelled horse shoe vortex resulting in high over speed at the edge regions at the ground level local flow separation at façades October Miedrzyzdroje 5/22

6 Flow field around buildings Plate shaped high rise building, wind flow parallel to the longitudinal axis reattaching flow separated flow (zones of highest suction) wake closes downstream in only a short distance from the building windward side (wind stagnation, i.e. over pressure) leeward side (suction) weakly modelled horse shoe vortex, thus a low over speed at the edge regions at ground level October Miedrzyzdroje 6/22

7 Flow field around buildings Tower high rise building separating flow, due to short length no reattachment at the building sides suction at leeward side is lower than at the plate shaped high rise with wind flow perpendicular to the longitudinally axis because the wake is less pronounced widely two-dimensional flow pattern with quick closing wake weakly modelled horse shoe vortex, thus small over speed at the edge regions at ground level due to displacement October Miedrzyzdroje 7/22

8 Flow field around buildings 200 windprofile u p M,100 = um,10 (100 /10) α = 7,3 m / s (2) height (m) speed (m/s) October Miedrzyzdroje 8/22

9 Flow field around buildings October Miedrzyzdroje 9/22

10 Flow field around buildings wind wind typical wind induced pressure differential for a high rise building with square cross section and windows opened at the windward and leeward side October Miedrzyzdroje 10/22

11 Pressure distribution in staircases ζ = p ρ v 2 v 2 pv = ρ V& 2 A (3) TR 2 staircase type 1: ζ = 25 staircase type 2: ζ = 56 October Miedrzyzdroje 11/22

12 Pressure distribution in staircases storey pressure difference staircase - ambient Zeta = 25 storey pressure difference staircase - ambient Zeta = pressure difference / Pa pressure difference / Pa building height 160 m, ambient temperature +30 C, inside temperature +22 C October Miedrzyzdroje 12/22

13 Pressure in lobby static pressure in safety lobbies and fire fighting lobbies influenced by other vertical shafts October Miedrzyzdroje 13/22

14 Pressure difference in smoke layer over-pressure relief lobby. V = α A 2 p ρ Tr (4) fire storey p therm = Tr g T ρ 1 T Tr RG h (5) staircase October Miedrzyzdroje 14/22

15 Pressure difference in smoke layer pressure distribution vs door height fire room temerature 100 C in flow vs door height fire room temerature 100 C 2 2 1,5 1,5 height / m 1 height / m 1 0,5 0,5 neutral level in half height neutral level at the top 0-4,0-2,0 0,0 2,0 4,0 6,0 pressure difference / Pa neutral level in half height neutral level at the top 0-3,0-1,0 1,0 3,0 air speed / m/s. 2 Tr therm = Tr g T 2 3 / p ρ 1 h = h TTr V α b 2g 1 TRG (5) 3 TRG (6) October Miedrzyzdroje 15/22

16 Consideration in EN :2003 Main driving forces on pattern of movement buoyancy experienced by hot gases on the fire storey, thermal expansion of hot gases in the fire zone, stack effect throughout the building wind pressure forces and HVAC systems. October Miedrzyzdroje 16/22

17 Consideration in EN :2003 Demand: door pressure difference min. p = 50 Pa reasonable general demand: F 100 N reasonable pressurization demand (subordinated to the opening force): 15 Pa p 65 Pa Caution if wide and/or tall doors on escape ways are used!!!! October Miedrzyzdroje 17/22

18 Consideration in German high rise guidelines Demands of the German building regulations und high rise guidelines: over-pressure in staircase necessary staircase volume flow rate safety staircase volume flow rate min. p = 15 Pa max. p = 100 N / 2m² V & = m³/h 1, 5 V& = k b h m³/h airflow from lobby to the fire storey under consideration of out flow of fire gases October Miedrzyzdroje 18/22

Possibilities for calculation Computer software for multizone buildings (zone-link-models) Consideration of 3D-modeling based on the fundamental equations different leakages, fan characteristic

19 Possibilities for calculation Computer software for multizone buildings (zone-link-models) Consideration of 3D-modeling based on the fundamental equations different leakages, fan characteristic curve, flow components characteristic curve, etc. 140 Druckdifferenzen Höhe (m) TR-außen TR-außen (RS) TR->SCH TR->SCH (RS) Lobby->Flur Lobby->Flur (RS) Druck (Pa) Pressure difference in a 150 m high building October Miedrzyzdroje 19/22

20 Technical notes At buildings with small height a pressurization with simple systems is possible. An active pressure control system is normally not necessary. Medium-rise buildings need active controlled pressurization systems. Buildings with heights of 100 m and more must have a pressurization concept which considers the influences of other vertical shafts to the horizontal pressure distribution. Normally the pressure control of the other shafts has to be considered. Active control systems, possibly large out flowing areas will become necessary, must work quickly so that the door opening forces after closing are small. Facades must close automatically in case of fire to control the pressure situation inside the building. October Miedrzyzdroje 20/22

21 Conclusions Aerostatic and aerodynamic effects play a big part on the pressurization of staircases. For buildings with small height the stack effect has not to be taken into account. Pressure differences depending on natural wind have to be considered. The effect on low rise buildings however is less strong. At buildings with a height above 60 m the building concept must consider the physical effects. Pressurization control is usually necessary. At buildings with an height of 100 m and more a general view to the whole building with quick working active pressure control systems is unavoidable. The EN : does not take into account the fundamentals of physics. The EN : does not include a test regulation as a requirement for CE marking. October Miedrzyzdroje 21/22

22 Thank You very much for Your Attention. Dziękuję bardzo za uwaga. If you have any questions I will do my best to answer them. October Miedrzyzdroje 22/22

23 I.F.I. Institut for Industriel Aerodynamics GmbH Institut at the University of Applied Sciences Welkenrather Straße 120 Germany Aachen notified Test, Inspection and Certification Body no in accordance with the Construction Products Directive October Miedrzyzdroje 23/22

Fire safety of staircases in multi-storey buildings The results of measurements in Buildings and Simulations

Fire safety of staircases in multi-storey buildings The results of measurements in Buildings and Simulations Grzegorz Kubicki, Ph.D. Department of Environmental Engineering, Warsaw University of Technology