2020年4月28日星期二

[AC] 問﹕Refrigerant 主流有邊幾種?選擇時有乜考慮?

答﹕

R407C, R410a, R134a, R123

R22
講下故事,得個知字。已被淘汰,因為Ozone Depletion Potential ODP會破壞大氣臭氣層。其餘介紹嗰啲都唔會有呢個問題。

先以易燃及毒性考慮,ASHRAE有個表


R407C (A1)
混合成份。由於容量同壓力同R22比較接近,所以容易直接取代R22. 但個效能會稍為降低。由於係混合比例緣故一有少少漏就嚴重改變特性,要放盡再充過。中/大型Chiller會用到。亦會用响Heat Pump, 因為Condense 溫度較高,去到六十幾度,用R410a會太高磅,用R134a效能又唔夠。

R410a
(A1)
混合成份。容量及壓力都比R22高出唔少,但同時效能都比其高。所以設計上Comprssor等部件會更厚,但又同時可降低噪音。响啲細機如家用冷氣機會用到。

R134a
(A1)
單一成份。取代舊有R12. 容量及壓力都比R22低一截,所以機身等部件都要做大啲,相對效能亦冇R22高。但單一純種關係,漏咗唔洗放晒先入,可以逐小咁補,較啱大型機用。

R123 (B1)
效能高,液態唔驚漏,GWP都低。但有微毒性。大型機會用。


到2019年,人類再提高標準,响國際協議Kigali Amendment 對高Global Warming Potential GWP值既Refrigerant都選擇逐步淘汰。 R407C, R410a, R134a都係高GWP系列。

R134a (A1) --> R1233zd (A1) / R513A (A1)
R410a (A1) --> R32 (A2L)
R123 (B1) --> R1234ze (A2L)

其實據FSD同EMSD既文件見到,似乎唔太主張香港港呢啲高密度環境度轉用較易燃既Refrigerant, 所以上面灰咗嗰啲都係得個知字。

(鳴謝﹕K、紅豆;Source: 冷暖在線, https://www.emsd.gov.hk/filemanager/tc/content_767/pms2019-2.pdf)

[AC] [EL] [FS] 問﹕試講講Data Center Design 有啲乜要注意?

答﹕

[AC]

Design Condition:
In General, D.B.: 18, R.H.: Less than 60%; 當然亦都要睇件Datacom Equipment環境溫/濕度需求


Data Center 同 Non Data Center 既Chiller分開比,Data Center Area 要N+1 Redundancy;
Gas Purging System要有個手動Exhaust Fan, 因為如果起咗Total Flooding System的話,就要靠呢把Fan嚟清;

計Sensible Load方面,ASHRAE都有比個趨勢估算出嚟,見得出Scientific用既GPU比雲儲存散熱更高;Communication 係最低;
上述係講緊一隻42U櫃既散熱量,42U係咁既樣

1U就即係入一件



有Liquid-Cooled, 呢種玩法就要確保响Dew Point以上防Condense


有Air-Cooled, 通常都係由地板入


Air-Cooled用Computer Room Air Conditioning CRAC Unit


[EL]

詳見 https://elvissharing.blogspot.com/2020/03/el-how-to-plan-design-electricity.html , 都係啲無限備份玩法。

Electrical Busway, 响上面好似電車路軌咁攞電




UPS可能會用有Flywheel嗰種,Wiki話係online方式,養住隻轉緊既飛輪可以頂住30s 等Genset起動, 及見 https://elvissharing.blogspot.com/2020/04/el-uninterruptible-power-supply-ups.html


此外為咗避免EMI Interference, IT cables 走High Level; Power Cable 行Raised Floor;
要因應BEEO裝Digital Power Analyzer 計住電流、電壓、功率 (7.7 Metering & Monitoring Facilities, Main Circuit, Feeder & Sub-main Circuit)


[FS]

Total Flooding System, see https://elvissharing.blogspot.com/2020/04/fs-gaseous-extinguishing-system.html

Very Early Smoke Detection Apparatus, see https://elvissharing.blogspot.com/2020/04/fs-automatic-fire-alarm-system.html , 但留意呢個System係唔會用嚟踢著FM200, 只係為咗早啲知

[MISC]

Water Leakage Detection (Linear Type)


Structured Cabling System
有Copper Cable & Fiber, 兩者各有優勢所以响Data Center度會混合嚟用。放線方式有國際標準或ER要求。
Optical Fiber: 輕、距離遠、速度快;
Copper Cable: 更可靠、响Data Center裡面功率低散熱少耗電少;

Cat5, Cat5e, Cat5 分別


(鳴謝﹕紅豆;Source: 2019 ASHRAE Handbook Application - Chapter 20)

2020年4月27日星期一

[Renew./Inno.] 問﹕火神山醫院响工程上有啲乜亮點?

答﹕

响建築Layout上既規劃,令醫護人員逗留既地方及出入通道唔會同病人嗰啲唔會交疊。亦係唔可以隨便徵用酒店/旅館既原因。


應用Design for Manufacturing and Assembly DfMA 及 Modular Integrated Construction MiC (外國有啲叫Prefabricated Prefinished Volumetric Construction PPVC), 詳見 https://elvissharing.blogspot.com/2020/04/renewinno-dfma-prefabrication.html
重點係加大重複構件數量,減少特殊構件數量,咁先容易高效批量生產。

Site Formation 整層HDPE, 再用鋼管墊起,一嚟防水二嚟可以下面走風火水電



逐級負壓系統,見 https://elvissharing.blogspot.com/2020/03/ac-isolation-room-mvac.html

(Source: BIMBOX https://bimbox.top/4914.html)

[Renew./Inno.] 問﹕DfMA / Prefabrication Components / MiC 分別係啲乜嚟?

Design for Manufacturing and Assembly DfMA 係一個概念嚟,顧名思義,著重考慮組件製造及裝配過程,以便响廠房完成預製再去地盤安裝,減少現場施工工序。Prefabrication Components and MiC 係兩個做法去實現DfMA呢個概念。
就好似Apps Store係一個概念,但就有N種實現方式,如Google Play Store, Apple Store etc.

响工場做好舊嘢先一口氣掟落地盤度裝有諸多好處,做過地盤就知,地盤立立亂,做好先掟落嚟响地盤工序少咗,House keeping又好咗,又唔洗咁多人同時响地盤安全度都高咗,工場做質量控制亦都易,成本/時間效益都好咗因為批量式生產。但都有難題,首先係運過嚟個Trasportation, Tower Crane等要配合到,仲有啲Alignment要好精準,砌過Facade就知件事既難度,更何況如果係成個MiC module咁砌。

Prefabrication Components - e.g. Prefabricated Facades / Staircases / Manhole etc., 只係某少部份用Prefabrication, 其餘大部份都係using conventional construction methods


Modular Integrated Construction - 一件頭過成個Modules咁响地盤度砌,包括風火水電都係包埋响個Module入面,再睇下Module之間啲風火水電等點接駁


電接駁


渠接駁


有啲Project 既DfMA用上述以外既方式嚟實現,如淨係做一組Cooling Tower Modularization. 用BIM做好設計圖後成組掟落地盤。


關於BS嘅MiMEP/emMiC, CIC網頁有好好嘅參考 https://mic.cic.hk/en/UsefulInfo/5

(Source: CIC; https://www.bca.gov.sg/Professionals/Technology/others/PPVC_Guidebook.pdf)

2020年4月23日星期四

[AC] 問﹕試簡介一下Chilled Ceiling System.

答﹕

先分Chilled Ceiling System & Chilled Beam System

Chilled Ciling System, 就咁Laid啲Pipe响個Metal False Ceiling度,Cools Room by Natural Convection & Radiation, max. output only 70W/m² (*100ft/ton大概係380W/; 200ft/ton大概係190W/)



Chilled Beam System又分兩種,一種係Passive, 一種係Active
Passive 同Active 最大分別係,後者會比Pre treated Primary Air, 去到160W/



最重要設計考慮係唔好滴水,即係只要任何物件,包括個Fin, Ceiling Panel etc.個Surface Temperature高過Design個Dew Point, 就唔怕室內落雨。

上面堆資料見到,Primary Air 12, 入水15℃, Dew Point 13.5℃, 就避到滴水。

用呢種嘢好處係全部都係因為少咗Fan帶嚟,慳電、靜、慳維修,Ceiling Depth要求都少咗;
壞處係有水管响頭頂經過有機漏水,同埋如果啲Sensor / Control 做得唔好就兜頭落雨。此外Cooling Capacity都唔係高。

順帶一提仲有種係行Low Temperature Chilled Ceiling System, 個水溫用7, 但唔多案例,淨係得中國有相關Standard. 

Example:
PAU駁住某堆Chilled Beam; Chilled Water 經Heat Exchanger派比Chilled Beam;


(鳴謝﹕紅豆)

2020年4月22日星期三

[AC] [EL] 問﹕醫院Hospital Design 上有啲乜要留意?

答﹕

[AC]

一啲地方如Magnetic Resonance Imaging MRI Room 個Sensible Heat 會好大;
科普下﹕MRI 睇軟組織,即係對水同脂肪既嘢係清楚啲;CT原理係X光一樣,但唔係平掃可切片,MRI係CT高級版;PET-CT 主要係睇癌症轉移,食啲F-18混葡萄糖結構既嘢落肚後,衰變正電子,撞電子後出兩個方向既Gamma Way Detect成像;以上呢堆都可以3D成像;一般係平掃一張、側掃一張,Axial嗰張就Depends; X光只可以平掃;


Operation Room 
- Possitive Pressure;
- min. 20 ACH;
- min. 4 Outdoor ACH;
- min. Filter Efficiency: MERV-14
- Exhaust 都要經Filter

Protective Environment (PE) (Immunocompromise 抵抗力弱,Leukemia 白血病, Burns,HIV etc.)
Possitive Pressure;
- min. 12 ACH;
- min. 2 Outdoor ACH;
- min. Filter Efficiency: HEPA (我估應該係指EU H13, 即係MERV 17)



*要裝個Device monitor住裡面同出面個Pressure Difference

Airborne Infection Isolation (空氣傳染病隔離)
- Negative Pressure (-2.5Pa);
- min. 12 ACH;
- min. 2 Outdoor ACH;
- min. Filter Efficiency: MERV-14
* All Room Air Exhausted Directly to Outdoors
Also refer: https://elvissharing.blogspot.com/2020/03/ac-isolation-room-mvac.html

普遍溫濕度都要控制,大概响21-24度,60% R.H. 內。
好多唔同病房可能有唔同Requirements, For Example, 
Upper Respiratory Disease, minimum 30% R.H.; 
Burn Patients, room temperatures up to 32°C db and relative humidity up to 95%;

用Air Cooled Chiller 相對會可靠啲;

睇DH本Guideline個要求似乎係所有地方既空氣都唔Recirculate

如果又唔用Thermal Wheel Recover 的話,個Ventilation Load 就係Outdoor嗰點同Design 嗰點
Filter Standard
ASHRAE 52.2 Minimum Efficiency Report Value MERV 17 大概係等於EU H13, 即係≧ 0.3µm 的話可以隔到99.97%;

AHU會先經一隻MERV 6 Disposable Panel Pre Filter


再經MERV 13 Disposable Bag Main Filter


之後再睇下經唔經HEPA

Ultra Low Particulate Air ULPA係比 High Efficiency Particulate Air HEPA再高一個檔次 (MERV 17 係HEPA, MERV18係ULPA);
*用0.3µm做參考既原因係再大粒啲,可以靠物理阻隔;再細粒啲,又可以靠靜電力黏住;係呢種Size最難隔所以攞嚟做參考標準
同時亦睇到,換氣次數越高,達到Removal Efficiency 99% 既時間就越短

Design上要留意呢啲Filter個Pressure Drop會好大

Reference: 
ASHRAE 170 Ventilation of Health Care Facilities; 
2019 ASHRAE Handbook Application - Chapter 9; 
HTM 03-01(MVAC); 
Guidelines for Healthcare Engineering System of Private Hospitals - Department of Health

[EL]

- Equipment requiring 3 phase supply, permanently connected to a separate sub-circuit; (HBN 10-02)
- Genset full 100% backup;
- Critical care areas (Life Support / Complex Surgery / Critical Medical Equipment / Lighting / IT System / Medical Gas / Call System(有個call operator, 好似接線生咁)/ CCMS), UPS supply; (如果出現Earth Fault 都跳UPS, 應該即係Isolated Power Supply, 唔知有冇理解錯). UPS refer https://elvissharing.blogspot.com/2020/04/el-uninterruptible-power-supply-ups.html
- Night Lighting, 每個病床位5 lux, 夜晚睇嘢唔會影响到其他病人;
- Light Design reference CIBSE Lighting Code

Reference: 
HTM 06-01 (EL);
Health Building Notes HBN 10-02: Day Surgery Facilities;

[PD]

Plumbing
1. Separate water supply system (Twin Tank) provided for General water supply (Lav.) / water supply for medical equipment system
2. UV steriliser / Revise Osmosis RO water system provided for medical equipment water supply. Must be off tank water supply. (即係有個儲水箱?)

Drainage
3. Grey epoxy coated cast iron drainage pipe to enhance the durability and corrosion resistance for chemical discharge.
4. Separate drainage stack for medical / general lav discharge, Two pipe system shall be used. (洗手盆、浴缸等用一條落;馬桶有固體既用另一條Drain落)

[Gas] (Medical Gas Pipeline System MGPS; Dental Air and Vacuum System DAVS)

- Source 要分Primary, Secondary & Reserve;
- Pipe size are selected to ensure pressure loss below 5%;
- T&C都係試Gas 種類,Quality (particulate contamination), Quantity, System Function, valve function, 嗰啲嘢;
- Medical Gas 設計見下表,都係類似Fire Hydrant, 邊個位邊度一開就要見要幾多Pressure幾多Flow

Medical Air 就好似蒸餾水咁,一啲好乾淨既空氣;
Helium 用嚟醫Respiratory?;
Nitrogen 係用响空氣手術刀;
Oxygen唔洗講掛;
Nitrous Oxide 麻醉Anaes.用;
Vacuum 唔係氣體嚟,純綷係用嚟幫手抽走一啲嘢如Nitrous Oxide;

Reference:
HTM 02-01 Medical Gas;
Cap. 295 Dangerous Goods Ordinance;

[Pneumatic Tube System]
快速將啲Blood Sample / Documents 由一個地方經氣動裝置去到另一個地方,大概傳到5kg, 以5 meter per second

--------------------------------------------------------------------------------------------------------------
2019年後,有條新法例 Cap. 633 Private Healthcare Facilities Ordinance 通過 (舊有Cap. 165 醫院、護養院及留產院註冊條例及Cap. 343 診療所條例由新呢條Cap.633取代(唔知有冇理解錯))
呢條條例將醫院分為三類﹕1. Hospitals, 可以Lodging or childbirth; 2. Day Procedure Centres, 可以Medical Procedures without Lodging; 3. Clinics, Medical Procedures or Lodging都唔得
*Medical Procedures including 外科、內窺鏡、化療、放療、麻醉 etc.
--------------------------------------------------------------------------------------------------------------

(鳴謝﹕紅豆,K;Source: Guidelines for Healthcare Engineering System of Private Hospitals - Department of Health)

2020年4月21日星期二

[EL] 問﹕Uninterruptible Power Supply UPS 可以分為幾多種?

答﹕

1. Offline / Standby, 供電嗰陣一頭叉住舊電,一頭比電,到冇市電嗰陣就轉用電池


2. Line Interactive, 類似 Offline / Standby, 當大既Voltage轉變時用電池;轉變唔大嗰陣就用隻Autotransformer嚟調電壓,咁舊電既損耗就冇咁大。


3. Online / Double Conversion, 由市電入嚟開始已經唔係直接比A.C., 而係先變直流再兵分兩路,一路比Equipment, 一路差住舊電。即係响供電期間UPS係全程介入,保障上係最好。
* Rectifier係由AC轉DC; Inverter係由DC轉AC;


仲有種係Data Center 會用既Flywheel形式,又叫Dynamic UPS,Wiki話係Online式嚟,見 https://elvissharing.blogspot.com/2020/04/ac-el-fs-data-center-design.html


(Source: Wikipedia)