Gii thiu H Thng H Trung Tm ChillerA. Tng Quan: Da vo mt t tm hiu v ngnh lnh. V mnh mun gip cho cc bn khng phi trong ngnh lnh c ci nhn n gin hn v h thng iu Ha Chiller ta nh (nht l dn k thut in, bo tr c in ta nh). H thng iu ha trung tm Water chiller l s kt hp mt cch khoa hc c tnh ton hot ng nhp nhng ca cc thnh phn trong h thng, m phn m nhim chnh li l cc k s ngnh t ng c tm hiu v lnh. Vit Nam do ti liu cn hn ch trong khi a s ci ti liu v H Chiller li bng Ting Anh. M dn k thut phn nhiu li t c duyn vi ngoi ng, bi vy m h thng iu khin v iu ha trung tm chiller vn t c c hi tip xc vi a s dn ngnh k thut lnh. Cui cng, mnh vit theo phong cch "hiu sao ni vy", nh vy s n gin d hiu hn cho ngi c l c nh vn bn t trong sch ra.B. M T H Thng:H thng c bn gm 5 phn c bn:1. Cm trung tm nc water Chiller.2. H Thng ng ng nc lnh v bm nc lnh.3. H Thng ti s dng Trc Tip: AHU, FCU, PAU, PHE .v.v.4. H Thng ti s dng Gin Tip: H Thng ng ng gi thi qua phng cn iu ha, Cc van iu chnh ng gi, ming gi: VAV, Damper.v.v.5. H Thng Bm v tun hon nc qua Cooling Tower (nu c) i vi chiller gii nhit nc.

1. M hnh h thng hot ng nh sau:C 4 Vng Tun Hon cho h thng nh sau: Vng tun hon mu : L vng tun hon nc nng bm vo cooling tower thy nhit ny ra mi trng. Vng tun hon mu xanh: L vng tun hon gas lnh trong cm water chiller. Vng tun hon mu tm nht: L vng tun hon nc lnh c bm n AHU, FCU, PAU, PHE .v.v. Vng tun hon mu vng: L vng tun hon ca h thng ng gi thi vo phng c iu ha.

2. M hnh h thng thc t nh sau:

3. Cc Thit B Trong H Thng:A. Cm Water cooled chiller :

L trung tm ca h thng, Tiu th in nng ln nht, gi thnh cao nht so vi thit b khc. c sn xut hng lot cng nghip theo nhng cng sut nh sn ti cc nc c nn cng ngh cao, t phn phi ring l ra theo cc cng trnh ta nh ln nc ngoi. Vic chn la v hm lng tnh ton n gin so vi cc thnh phn cn li ca h thng. c chn theo nng sut lnh yu cu (ly n gin 15m2bng 1 tons loi iu ha thng). Loi my nn gas, loi Gas, Hiu sut lm vic (cp gim ti, chy bin tn.v.v.). Hoc mt s yu cu km theo: gn bm nhit, cht ti lnh glycol .v.v. Cc thng hiu hng u th gii: Trane, Carrier, York, Mc Quay, Hitachi,Climaveneta, Dunham - bush.v.v.B. H thngbm vng ng nc lnh :

Bm Nc: chu trch nhim bm nc lnh qua Chiller n ti s dng trc tip (Nc lnh sinh hot trao i qua tm PHE, AHU, FCU, PAU.v.v.). Hiu sut cao hn nu mi chiller c ring mt bm cho mnh, bm l loi bm dng cho nh cao tng c n nh, ct p khng cao lm (v cn bng tun hon kn gia ct p i v ct p v). Lu lng nc t bm qua chiller lun phi c gi n nh, khng tng hay gim cng sut lu lng bm bng bin tn nu khng c s kt hp c khoa hc ca h thng. Chn cng sut bm: da vo ct p nc v lu lng nc (lu lng c sn theo thng s Chiller chn). Vic Tnh Ton ct p Bm nc c phn phc tp do cc thng s ton nhiu (lu lng nc, di ng ng, cao, st p qua co, ct, T, AHU, FCU, PAU .v.v.). Mt d c tnh ton bng tay lm thuyt minh d thu, nhng a s vn da vo phn mm phn tch tnh ton a ra kt qu tt nht. ng ng: Thng l ng thp en c bc cch nhit vi ng nc lnh. ng thp en hay ng ng vi ng ng nc nng dn ra cooling tower. Hin nay ngi ta bt u thit k sang ng nha PPR cho h thng chiller, mt s cng trnh dng ng loi ny hin ang s dng rt tt. Vic la chn kch thc ng ng da vo lu lng m n chuyn ch:ng ng nh qu dn n tn tht p sut nc ln ng thi ng ng phi chu p sut cao hn khi lm vic. ng ng qu ln dn n tng gi thnh do thi cng v gi ng ng. Ty theo lu lng m ta chn kch thc ng ng, tra theo catalog nh sn xut.

C. H Thng AHU (Air handling unit), FCU (Fan Coil Unit), PAU (Primary Air Unit) hay MAU (Make Up Air):AHU, FCU, PAU bn cht ging nhau nhng khc mc ch s dng.-- AHU:l b x l nhit mh thng ng gitrung tm v chia ra lm nhiu ng gi ph i vo khng gian iu ha. Nh vy mt AHU c th c nhiu lp lc bi, nhiu dn coil ng ng (nc nng hoc lnh) theo iu kin x l yu cu v dng cho mt khng gian ln.-- FCU:th dng cho nhiu phng nh hay khu vc nh ni m h thng ng gi ca AHU khng th ti c, hay vi yu cu mt vi phng nm trong khu vc vi yu cu nhit v m khc vi AHU ang lp s dng. FCU khng x l nhit m tt bng AHU (do kch thc sn xut hn ch). Nn vi yu cu i hi cao ta bt but s dng thm b x l PAU (lc, lm lnh,gia nhit, tch m hay to m) c lp bn ngoi v ni ng gi cho nhiu FCU bn trong.-- PAU:Lun cp gi kh hn khng kh trong khng gian iu ha. Kh y ni n cha hi ( hay kh), khng phi m tng i ( v gi sao khi ra coil FCU th c m tng i cao 85~95%).Lun cp gi nhit cng thp ( >9 nu dng VAV, > 11 nu dng CAV) khi c th, khi ny s gim c size ca FCU hay Indoor Unit.

** M Hnh AHU:Ty theo nh sn xut m AHU c cu trc khc nhau

L thit b trao i nhit trung gian gia nc lnh hoc nc nng vi khng kh cn c iu ha. y l thit b c yu cu hm lng tnh ton v t ch ring bit nh: sn xut theo t hng cc thng s: lu lng gi, nhit , m trc v sau yu cu ca phng iu ha. H thng t iu khin, kt ni c lm ring ti cc cng ty gia cng c in lnh. Hay ni cch khc l s kt hp ca 2 hay mt cng ty chuyn v sn xut gia cng AHU v chuyn v thit k, thi cng iu khin lnh ta nh. gim li mt s quy trnh tnh ton v h thng iu khin, nh cung cp AHU cho ra mt s phn mm tnh chn ring cho hng ca h. Bi vy khi c cc thng s yu cu, ta ch cn m phn mm tra v chn loi AHU ph hp nht cho h thng. H cung cp lun gii php iu khin v kt ni, nhn tn hiu t my tnh trung tm (BMS ca ta nh).** ng ng Nc Lnh Vo AHU:Do khng phi lc no cc coil AHU cng hot ng y ti m do qu trnh thit k lun d tr cng sut lnh vi mc cao nht. iu ny dn ti cc ti lun hot ng ch non ti, v cc phng php tng hiu qu khi chy ch non ti ra i ang dn c ci tin. Cc gii php theo bc herot trn HVAC nh sau: Van 2 Ng (two way valve control). Van 3 Ng(three way valve control). Face and bypass damper control. Primary-Secondary (H thng 2 vng nc ). Variable Primary Flow (VPF)( H thng lu lng thay i vi on ng by pass).1.Van 3 Ng (three way valve control):Lu lng nc lin tc. Tn hao p lc nc qua h thng ln, dn n hao in my bm nc. Vic ha trn nc hi v nc lnh cp khng tt nh mong mun.

2. Van 2 Ng v bypass (two way valve control and bybass):Thay i lu lng nc cp, p lc c gii phng qua van bypass do sp p t trn bm cng nh i v tit kim in my bm.

3. Face and bypass damper control(B mt ca gi dng Bypass):- Nh qua h thng ca gi iu chnh c, gip cho mt lng gi thi qua bypass damper khi chy non ti.- Va tit kim c ng bybass, m st p nc t nn tit kim in cho my bm, nhng gi thnh v iu khin loi ny c hn 2 loi trn.

4. Primary-Secondary (H thng 2 vng nc):- Nh cc bn thy th h ny c chia thnh 2 vng nc, vng s cp - Primary ch dng cung cp nc i qua cm Chiller nn thng ch cn nhng bm vi ct p nh. Cm S cp ny bt buc phi l Bm vi tc c nh v khi ny cng ngh sn xut Chiller cha cho php lu lng nc qua Chiller thay i c, lu lng ny bt buc phi l Hng s, nu lu lng thay i th h thng lp tc ngt Chiller v Bo li H thng.- Vng nc Th cp-Secondary vi mc ch l phn phi nc lnh vo cng trnh, n ti tiu th... th s dng cc Bm Bin Tn c kh nng thay i gim v cp c vn tc Bm==> chnh l gim in nng Tiu th.- Khi ny h thng phi c ng Bypass duy tr lu lng nc qua Chiller l c nh, lu l ng Bypass ny khng c van no chn c (may ra c th gn c Van 1 chiu chn nc t u ht ca bm Pri dn qua u ht ca Bm Secondary).- h thng ny c kh nng tit kim nng lng cho h thng Bm tun hon khi dng Bin tn y, nhng chng ta phi thm c mt h thng bm khc, km theo l tiu tn bit bao nhiu chi ph ph kin km theo n.

5. Variable Primary Flow VPF ( H thng lu lng thay i vi on ng by pass):

- Khi ny ch cn mt h Bm duy nht i qua Evaporator ca Chiller vi cc Bm dng Bin tn iu khin.- Khi gim ti th Chiller cng Bm nc u c kh nng gim ti, khi ny phi dng mt ng ng Bypass vi van iu chnh trn (nhn s qua th c tng ging ht nh H thng th 2 ni trn nhng thc tnh th nguyn l khc hon ton). Van Bypass ny vi mc ch duy tr lng nc qua Chller khng c thp hn mt gi tr Minimum m Chiller c.- Khi ny cc dn Coil cng phi s dng h thng Van 2 ng c th dng cm bin Delta P (cm bin hiu p sut) iu khin cc Bm.- Vic tnh ton ng ng Bypass ny phi p ng c lu lng nh nht ca Chiller ln nht trong h thng, thng thng khi chn la mt Chiller th nh sn xut s phi cung cp cho bn gi tr Minimum ny.- Theo nghin cu ca t chc ASHRAE th h thng VPF ny c kh nng:1. Gim nng lng tiu tn trn ton h thng n 3% mi nm2. Gim chi ph u t khoang 4-8% do gim c s lng bm so vi h s 3, v tit kim khng gian, Co, Tee, Fitting km theo n.3. Gim chi ph vng i, bo tr khong 3-5%4. Gim nng lng cho h Bm nc lnh t 25-50%5. Gim nng lng Chiller n 13%- Nhng thng s trn y u c c s chng minh vi nhng tnh nng ca h thng VPF s tm lc sau y: c kh nng ko dn di cng sut Chiller p phi hot ng ch y ti vi hiu sut cao nht, gim s ln ng m h Chiller lm tng tui th, tng tin cy...D. H Thng ng Gi: Ha trn gi ti v gi hi, lng gi ha trn ny s c a vo AHU hay FCU x l theo yu cu v nhit , m ca khng gian iu ha. C nhiu phng php tnh ton ng gi. Nhng phng php s dng ph bin l phng php ma st ng iu. Tnh ton khng qu my phc tp do d dng trong la chn s lng ming gi v kch thc tng on nhnh. thng s ch yu l lu lng gi v n yu cu iu d dng tra ra c. M iu kh khn nht l th hin trn bn v 2D hoc 3D ra thng s chnh xc nht cho nh u t. Ngoi ra cn c h thng ng gi khc nh ng gi hi, ng gi thi, ng gi tng p cu thang .v.v.E. H thng kt ni iu khin Chiller:Ti liu iu khin AHU. Tng phn thit b: Chiller, AHU, FCU, PAU, Van 2 3 Ng.v.v. iu hot ng c lp bi b iu khin DDC. V DDC c th nhn tn hiu t cm bin (cm bin nhit , m, lu lng gi v nc, nng CO2.v.v.), c lp trnh iu khin sn bng my tnh v c tch hp cng truyn thng. DDC c kt ni vi h thng my tnh ch qua cc chun giao tip (cng giao tip truyn thng RS232, RS485.v.v.) kt ni c vi nhau. Qua my tnh ch c th nhn bit cc h thng no ang hot ng v tnh trng hot ng. Do my tnh c thm chc nng phn quyn iu khin m my tnh ch c th tc ng can thip vo d liu c lp trnh sn trn DDC iu khin thit b theo nhu cu ca ngi qun l ca my tnh ch. Vic lp trnh, iu khin v m bo cc thit b c th giao tip c vi nhau (bi tnh hiu s i hi cc thit b phi c chung mt chun giao tip nh giao tip nh HTML, Lon Works, BAC Net, OPC, AdvanceDDE, modbus, ODBC.v.v) kt ni vi my tnh vi phn mm BMS vit ring cho cng trnh ta nh. a s l do mt cng ty iu khin v s dng mt dng hng iu khin chuyn dng ring ca hng (VD: thit b delta.v.v.).