[AC] [EL] 問﹕Super High Rise Building 响機電設計上有啲乜特別要留意？

答﹕

Design Temperature, 去到500米高Design Outdoor Temperature要預細一兩度。

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Stack Effect

Stack Effect 成因﹕

冬天﹕Building裡面熱空氣(Equipment / Human Load, or heating) 向上升，以致氣壓低；

出面室溫凍，空氣經由Lift Shaft 或 樓梯由低層向上扯；

夏天﹕剛好相反，由於室內開冷氣，冷氣係向下沉，高層氣壓低過低層氣壓，空氣由低

位扯出去；

Stack Effect 後果﹕

- 開Entrance Door, Lift Door difficulty, 兼且High frequency noises from gaps in the elevator doors 好似吹口哨咁；

- Energy consumption, also reverse flow; 

Stack Effect 解決方法﹕

Active - Pressurize lift lobby; temperature control of lift shaft; 

Passive - Builder 嘢多，e.g. Revolving door; Adding separation door between main entrance lobby and office passenger lift lobby; Lift machine room 門關實啲；

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Hydraulic Zoning

設計上有幾個考慮﹕

Hydraulic Loop 數量

少到冇得唔得？可唔可以Underground 放Chiller Plant 跟住一嘢行晒成棟樓？唔得，因為Chiller也好，泵也好，Terminal / Heat Exchanger也好都頂唔到呢個壓力，呢啲嘢大概極限只係20-25bar, 但10M 1bar計，打上五、六百米高冇可能唔分Loop.

引出第一個結論，就係冇可能唔分Loop, 之後就睇第二個問題

Chilled Water Temperature

分多幾Loop後意味住Chilled Water Temperature 上升。

之後再引伸多兩個問題

由得加Loop當冇事發生過得唔得？唔得，因為每多一LOOP，就多一個位energy consumption, 此其一；越多Loop後Chilled Water 溫度越高，Humidity Control 越難做，同時意味住要更大風量先Achieve 到Design condition, 即係要更粗Air Duct 殺低個Head Room;

另一個解決方法係降低supply chilled water temperature, 咁的話去到後啲既loop都維持得返chilled water temperature正常水平；但太低的話，又會影响個COP;

Separated Chiller Plant or Centralized Plant

雖然Separated Plant  可解決要用N個Hydraulic Loop 問題，但同時有其他劣勢，諸如部Chiller放咁高壞咗枱走問題，增加Vibration / Noise 响主要房間問題，增加Structural Loading etc.

Centralized Plant 响 operation, maintenance and energy optimization 上更有優勢；

Super High Rise Building Hydraulic Zoning Example:

如果唔拆loop, 改用Pressure Reducing Valve又得唔得？唔得，因為PRV只係用响open loop system, 如果用响close loop, 會唔夠壓力回水﹕

過咗Load之後唔夠壓力，呢一截就會變成死水；唔落的話啲equipment又頂唔到咁大Pressure.

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Central Pretreated Air System or Direct Fresh Air System

Central Pretreated Air System

- PAU located in mechanical floor and refugee floor, main riser in building core (Spatial)

- Reduce AHU room area on each floor (Spatial)

- Central treatment of noise & vibration

- Heat recovery

- Maintenance in mechanical floor

Direct Fresh Air System

- Fresh air can be adjusted according to individual zone

- Reduce riser size (Spatial)

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Lift

- 起碼要有一部大型既Lift由頂到兼有一定載重力由頂到底，用嚟運大型物件；此外要留意個Lift Shaft 會有Piston Effect, 可能要裝特別Louver / Ventilation

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Backup plan

用Air Cooled Chiller Backup sensitivity area

(鳴謝﹕K)