Bo co thc tp tt nghip
Bo co thc tp tt nghip
LI NI U
Chu trnh nn kh c bn khi c p dng trc tip cho h thng lnh c gi nh l
h thng lm lnh trc tip. Khng kh trong phng c lm lnh trc tip qua dn
bay hi m khng c mi cht ti lnh no khc c s dng. H thng lm lnh trc tip
c s dng rng ri trong cc ng dng dn c, thng mi v cng nghip, Nhng khi
s dng cho nhng mc ch ln hn chng c nhng hn ch v ng dng, cng sut, hiu
sut. Khi ngi ta s s dng h thng lm lnh trung tm chiller hay cn gi l
h thng lm lnh gin tip vi mi cht lnh trung gian ph bin hin nay l
nc.Trong qu trnh tm him v h thng chiller em c thy Nguyn nh Vnh hng
dn tn tnh c th hon thnh tt nht bn bo co ny. Em xin chn trng cm n
thy !
Sinh vin thc hin
Nguyn Xun Thnh
MC LCLI NI U1CHNG 1: GII THIU CHILLER31.1. phn loi
chiller31.1.1. Chiller hp th31.1.2. Chiller nn hi5CHNG 2: CC H THNG
CHILER62.1. H thng 1 chiller62.2. H thng chiller song song72.2.1 H
thng c bn72.2.3. Cc b phn c bn82.2.3.1. Chiller82.3. H thng chiller
mc ni tip ( series chillers system )92.3.1 H thng c bn92.3.2. Cc b
phn c bn112.4. So snh Tiu th nng ln gia cc h thng.122.5. H thng 2
vng tun hon152.5.1. Cc b phn ca h thng .152.5.2. Bm bnh
ngng172.5.3. ng chung172.6. H thng bm s cp lu lng thay i18Ti liu
tham kho :20
CHNG 1: GII THIU CHILLER
1.1. phn loi chiller
C nhiu cch phn loi chiller, l da vo loi my nn s dng, cch thc gii
nhit, lnh vc phc v l thng mi hay cng nghipTuy nhin phn loi chiller
d dng nht l da vo chu k tun hon ca mi cht lnh. Theo cch ny ta c th
phn chiller lm 2 loi ch yu: chiller nn hi v chiller hp th.
1.1.1. Chiller hp th
Hu ht cc h thng lnh c s cho h thng HVAC l h thng chu trnh my nn
kh . Tuy nhin 1 s cng trnh nh l khu th ln, khu phc hp bnh vin, nhng
ni m c sn h thng phn phi hi nc ln ngi ta c th tnh n phng n s dng
chiller hp th.
1.1.1.1. C ch hot ng
Cp mi cht hp th u l H2O /LiBr. Mi cht lnh : LiBr Dung dch long :
L hn hp H2O /LiBr vi lng LiBr trong nc thpDung dch c : L hn hp H2O
/LiBr vi lng LiBr trong nc cao.H thng gm c 2 vng tun hon l vng tun
hon ca mi cht lnh v vng tun hon ca dung dch.Mi cht lnh dng lng qua
van tit lu i vo bnh bay hi. Mi cht lnh ha hi sau khi hp th nhit ca
nc i trong dn ng. Hi mi cht lnh i vo bnh hp th v b dung dch long
trong hp th. Dung dch long tr thnh dung dch c. Dung dch c c bm vo
bnh sinh hi . Bnh sinh hi c cp nhit v mi cht lnh trong bay hi ( Bnh
bay hi c cp nhit va bay hoi ht lng mi cht lnh ) . Hi mi cht lnh p
sut cao i vo bnh ngng t v b ly nhit tr thnh dng lng. Mi cht lnh dng
lng li qua van tit lu vo bo bay hi.
Hnh 1.1. S h thng my lnh hp th
1.1.1.2. u nhc im ca h thng lnh hp th.
u im :S dng ngun nhit c nhit khng cao ( 80 oC 150oC ) hot ng. H
thng c th tn dng c nhit tha t qua trnh t l hi , t ph thi, hay nng
lng ti to nh nng lng mt tri...H thng c t chi tit chuyn ng , kt cu
ch yu l cc thit b trao i nhit trao i cht, b phn chuyn ng duy nht l
bm dung dch.Trong cc vng tun hon khng c du bi trn nn b mt thit b
trao i nhit khng b bm du lm gim hiu sut trao i nhit.Khng s dng mi
cht lnh gy hiu ng nh knh hay thng tng ozon.Nhc im:Gi thnh t hn 50%
so vi chiller my nn hi.Din tch lp t ln hn so vi my lnh nn hn (khong
50% )COP ch t 1.0 n 1.1
1.1.2. Chiller nn hiChiller nn hi s dng in nng vn hnh my nn lm
ngun nng lng truyn ng cho qu trnh tun hon ca mi cht trong chiller.
Theo ta c cc loi chiller c cng sut khc nhau s dng cc loi my nn khc
nhau.u im ca chiller nn hi :Kch thc nh hn so vi chiller hp th.C
nhiu cng sut la chn.Chim din tch khng gian t hn chiller hp th.COP
cao (chiller gii nhit nc my nn pit tng 4.2, MN ly tm l 6.1 )Nhc
im.Gy n , rung ln hn chiller hp thS dng mi cht lnh gy ra hin tng nh
knh.
CHNG 2: CC H THNG CHILER
2.1. H thng 1 chiller
Cu hnh ng nc lnh cho 1 chiller c th hin trong hnh 1.1
Hnh 2.1: H thng c bn 1 chiller
S dng 1 bm nc lnh duy nht Chiller cung cp nc lnh cho AHU/ FCU H
thng ny ph hp cng sut nh . H thng c u , nhc im sau. u im : Chi ph u
thp.Thit k n gin. Nhc im :Vi h thng my nn n th bt c b phn no gp vn
( My nn , bm, Bnh ngng t th chiller s ngng lm vic nh hng n cung cp
lnh. Nhiu khi iu l khng th chp nhn c.H thng 1 chiller t c s dng
trong thc th. Sau y em xim php c trnh by nhng h thng multichillers
thng gp trong thc t.S dng nhiu chillers ghp vi nhau ta c th iu chnh
ti lnh ty theo nhu cu s dng ( ch ti lnh 50 % hoc nhiu hn ) . Nc lnh
vn c cung cp nu nh trong trng hp 1 chiller b hng Trong trng hp nhng
ni yu cu v ch nhit m chnh xc nh trung tm my tnh, bnh vin, phng
nghin cu ... Th chiller d phng nhiu khi c s dng phng 1 chiller no
trong h thng multi chillers khng chy , hoc cn sa cha .My nn ca
chiller l my nn trc vt do khi m ti lnh gim xung thp hn 30 % cng sut
ca chiller th hiu sut ca h thng cng gim . H thng nhiu chiller c th
khc phc c nhc im ny ca h thng 1 chiller.2.2. H thng chiller song
song
Nhng bt li khi s dng 1 chiler duy nht nh ch thch hp vi h thng
cng sut nh, kh m bo c n nh lu di do chc chc c nhng lc my phi dng li
bo dng, sa cha , hay khi ch ti nng nn th hiu sut s dng khng cao. Do
cung cp s d phng v ci thin cht lng iu khin , hiu sut s dng trong
thit k h thng HVAC. Hu ht cc nh thit k s yu cu nhiu hn 1chiller. H
thng chiller mc song song v ni tip c a ra.
2.2.1 H thng c bn
Hnh 2.2. S nguyn l hot ng c bn ca h thng chiller song songVng
tun hon ca nc lnh :Nc lnh (chiller water supply ) 44oF c bm n cc
AHU/FCU. Nc ra (WR) khi cc AHU/ FCU c nhit 55 oF li c bm qua 2
chillers lm lnh. Vng tun hon ca nc lm mt bnh ngng :Nc c nhit 85 oF
c bm vo bnh ngng ca chiller. Sau khi ra khi chiller nc c nhit 95 oF
qua thp gii nhit c lm mt xung 85 oF. Nc 85 oF li tip tc tun hon lm
mt bnh ngng.
2.2.3. Cc b phn c bn
2.2.3.1. Chiller
Cng sut ca tt c chiller bng cng sut ca h thng cng thm d phng.Hai
hay nhiu chiller c th ging khc nhau ty theo thit k v iu kin ti
chnh.C th chn chiller gii nhit nc hoc gii nhit gi2.2.3.2. BmBm
trong h thng dng bm nc lnh v nc lm mt. Bm c loi lu lng khng i c loi
lu lng thay i.2.2.3.3. Thp gii nhit Thp gii nhit bng nc c dng lm mt
bnh ngng ca h thng2.2.3.4. Trnh t hot ng ca h thng.Vi h thng lu lng
khng i. Khi h thng ch cn hot ng vi 50 % cng sut th ta cn ngng hot
ng ca 1 chiller. Ch vi 1 chiller m p ng c nh cu ti nh vy th r rng
hiu sut ca h thng nh mong mun. Vn y l ti 50% ti nc hi ( WR) 49 oF
vn qua chiller ngng hot ng m bo lu lng khng i. Chiller hot ng c t
nhit nc ra l 44 oF s ha trn vi nc 49 oF qua chiller khng hot ng
thnh nc c nhit 46,5F. Nc 46,5F cp cho cc AHU/FCUNu h thng hot ng ng
cch, khi nc ra khi dn lnh m ln th h thng s iu khin van thay i lu
lng nc chy qua dn lnh. Vn y l nu nc qua dn lnh m hn cho php s nh
hng n vic kh m cho khng gian iu ha ( Nhin hin tha vn c ly i bng vic
thay i lu lng qua dn lnh )Cc gii php a ra khc phc : Gii php 1 : Chy
c 2 chillers nhng nh vy hiu qu nng lng khng cao v tht s khng cn
thit. Gii php 2 : Cch khc l t li lm gim nhit nc ra ca chiller ang
hot ng c c nhit nc ha trn nh mong mun. Nhng cch c nhng kh khn : Kh
iu khin Chiller lm vic ch ti nng n dn n lm gim hiu sut ca my. Gy ra
mt n nh ca h thng Gii php 3 :Thm 1 van in t (isolation valves ) ngn
dng chy qua chiller khi n khng hot ng nhng gii php ny khng c khuyn
dng cho h thng lu lng khng i. Nguyn nhn l ta khng th m bo chc chn l
bm s c th bm lu lng nc lnh cung cp cho cc khu vc tiu th nu nh tt c
cc nc lnh u i qua 1 chiller. Vn khc na l p ng c lu lng khng i khi 1
my dng hot ng th tc nc s tng iu nh hng n cc kt cu c kh. Khng c lu
lng nh thit k th ta khng th chc chn rng tt c nhng ti lnh ring l nhn
lu lng nc lnh yu cu. Trong trng hp my bm tht s c kh nng cung cp c
lu lng nc khng i nh ban u ca 2 chillers th li c kh nng vt qu di lu
lng nc qua chiller cho php , kt qu l gy ra nhng nguy him tim tng
cho chiller v ngi vn hnh.Gii php an ton nht trong 3 phng p trn l
phng n 1 vn hnh c 2 chiller bt c lc no nc lnh c yu cu , tuy nhin n
lm tng vn u t cho bm nc lnh v ng ng tng chi ph vn hnh.
2.3. H thng chiller mc ni tip ( series chillers system )
H thng cc chiller mc ni tip nhau l 1 phng thc khc vn hnh nhiu my
chiller. Phng php ny gii quyt bi ton ha trn ca h thng chiller mc
song song. H thng ny n gin trong thit k v vn hnh.2.3.1 H thng c
bnVng tun hon ca nc lnh :Nc lnh (chiller water supply ) 44oF c bm n
cc AHU/FCU. Nc ra (WR) khi cc AHU/ FCU c nhit 52 oF li c bm qua
chiller 2 . qua chiller 2 nhit gim xung 46.5 oF nc tip tc i vo
chiller c lm lnh xung 44 oF .Vng tun hon ca nc gii nhit bnh ngng :H
thng gii nhit bnh ngng bao gm bm bnh ngng , H thng ng, thp gii
nhit. Nh trong hnh th hin nc c bm vo bnh ngng ca chiller c nhit 84F
sau khi ra khi chiller c nhit 95F . Nc c nhit 95F i qua thp gii
nhit xung nhit 84F. C nh vy lm thnh 1 vng khp kn. Nu c 2 chiller c
cng cng sut th s c 2 ng ng song song khc nhau cung cp nc cho bnh
ngng. Chiller 1 (Heat chiller ) c xc nh 45% ti v chiller 2 (lag
chiller ) l 55 % ti ca h thng. C iu ny l v chiller 1 cung cp nc lnh
44F (ch setpoint) . Nhit nc ra ca chiller xp x 48.5F i vo chiller
1. Ch lm lnh ca chiller 1 nng n hn do cn lu lng nc qua bnh ngng ln
hn. Ta gi y l cch lnh gim hnh thang, n cho cng sut lnh ln hn.Hnh
[3.1] th hin hai chiller ghp ni tip. Lu lng nc i qua c hai chiller
l 100 % . s c tn tht p sut trn bnh bay hi ca chiller. Vng nc ca h
thng c th c lu lng khng i hoc thay i. H thng lu lng thay i lm tng
thm phc tp ca h thng nhng tit kim c chi ph bm. H thng lu lng thay i
c gi l h thng 2 vng tun hon (primary/secondary system ) v thit k lu
lng s cp thay i ( Variable primary flow design ) .
Hnh 2.3: H thng ni tip chiller c bnVi h thng lu lng khng i, di
nhit ca nc lnh chiller thay i theo ti. Di nhit thit k ca chiller s
thp hn di nhit ca mi FCU/AHU. V d nh di lm vic ca chiller l 8F
trong khi ca cc dn lnh trong FCU/AHU l 10F Vi h thng chiller mc ni
tip th khi tc dng chy tng th ng thi tr khc thy lc cng tng. H thng
ny nn xem xt chn chiller c bnh bay hi kiu One Pass Shell gim tn tht
p sut mc cho php2.3.2. Cc b phn c bn 2.3.2.1 chillerKhi lc chn h
thng chiller ni tip vic lc chn chiller cn xem xt k cng. c bit nn cn
thn vi chiller nh v lin qua n tr khng ca bnh bay hi. Tn tht p sut
thng c thit k c th chp nhn c vi tc dng chy khong 2.4gpm/ton. Khi tc
tng n 4.8gpm/ton th tn tht tng ng k. Khi tc dng chy l 2.4 gpm/ton
tn tht p sut qua bnh bay hi l 10ft, khi tc dng chy l 4.4gpm/ton th
tn tht l 40ft. Tng ln gp 2 ln ( tn tht ma st t l vi bnh phng tc ).
Vi cc chiller ln bnh bay hi c thit k ln hn c tr khng cc b thp hn so
vi cc chiller nh.
Hnh 2.4 Thit b trao i nhit kiu ng v ( One - Pass Shell ,Two-pass
Shell )Nu nh ta ghp ni tip 2 chiller c bnh bay hi ng v kiu One -
Pass Shell th tn tht p sut c th so snh c vi kiu Two-pass Shell .Hai
kiu trao i nhit khc nhau v ng i ca nc nh th hin trong hnh 3.2Cc
chiller s khng c ch hot ng ging nhau . lead chiller (Chiller 1
trong hnh 3.1 ) c yu cu thang ch hot ng khc lag chiller (Chiller 2
trong hnh 3.1 ) . Ch lm lnh ca lead chiller su hn . Vic lu chn
chiller phi lm sao tha mn c cng sut lnh cho h thng lnh bt c thi im
no vi hiu sut s dng cao nht.Di nhit nc lnh thay i th h chiller ni
tip s b nh hng nhiu hn so vi h song song. Khi di nhit tng, h
chiller ni tip cho hiu sut tt hn h chiller song song.
2.3.2.2. Trnh t hot ng ca h thng
H thng chiller ni tip c th u tin ti cho chillers. Khi ti tng ,
lead chiller s tng t 0 % n 100 % cng sut p ng ti .Ch khi lead
chiller chy y ti ( Khong 45 % ti ca c h thng ) lag chiller mi c khi
ng.C 3 phng php vn hnh lag chiller: Phng php 1 :t nhit cho pha
chiller thng lu (UCH ). Ci t UCH ch khi ng khi chiller h pha h lu
(DCH) y ti ( 45 % ti ca h thng ). UCH s chi ti cn li ca h thng (45
% n 100 % ti ca h thng ).Trng hp m DCH gp vn khng lm lnh c v l do
no y, th UCH khng m bo nhit nc cung cp cho AHU / FCU . Tr khi ci t
li ch lm lnh nc ca UCH. Phng n 2 :Di chuyn cn bin nhit ca UCH v DCH
cho nhau. B iu khin se u tin cho UCH chy trc . Ch khi no UCH chy y
ti m h thng cha cng sut lnh th lc DCH mi khi ng cn bng ti . Phng n
3 :Dng b iu khin cho php lin kt c 2 chiller vi nhau. Ty theo iu kin
ti m chy chiller no trc . chiller no chy trc y ti th chiller th 2
mi c khi ng cn bng ti. Vi phng php ny th hng nm tit kim khong 2 %
chi ph vn hnh h thng.
2.4. So snh Tiu th nng ln gia cc h thng.
Ta c biu hnh trn % cng sut v % tiu th in hng nm ca thit b chnh
trong h thng chiller .
Hnh 2.5 Biu ca h thng chiller n
Hnh 2.6 Biu ca h thng chiller ghp song song
Hnh 2.7 Biu ca h thng chiller ghp ni tip
Bng so snh cng sut in ca cc thit b in c trong h thng chiller vi
lu lng khng i.H thngChiller,kWBm,kWThp gii nhit, kWQut AHU,
kWTng,kW
Chiller n44010040185765
Chiller ghp song song44010040185765
Chiller ghp ni tip44010040185765
Bng so snh tiu th in hng nm ca cc thit b in c trong h thng
chiller vi lu lng khng i.H thngChiller,kWh/nmBm,kWh/nmThp gii nhit,
kWh/nmQut AHU, kWh/nmTng,kWh/nm
Chiller n258,344175,68916,597334,237784,867
Chiller song song258,344175,68916,597334,237784,867
Chiller ni tip237,607160,76219,243334,237751,849
Nhn xt :Qua biu v s liu thng k c c th thy v cng sut ti ca c 3 h
thng l nh nhau.H thng chiller ni tip tit kim nng lng hn h thng
chiller n v chiller song song.
2.5. H thng 2 vng tun hon
Hnh 2.8. H thng 2 chiller mc song song 2 vng tun honPump :
BmPrimary loop : Vng s cpSecondary : Vng th cpInvertor pump : Bm
bin tnPiping bridge : Cu ngHnh 5.1 Th hin h thng 2 chiller mc song
song 2 vng tun hon. Vng s cp gm c bm , chiller , van check . Vng th
cp gm c bm c iu khin c lu lng , n bm nc lnh cung cp cho cc AHU/FCU.
Hai vng c cch ly thy lc bng cu ng. Cu ng l b phn chung ca c 2 vng
tun hon. Cu ng c thit k sao cho c tn tht nh nht . Do lu lng ca vng
ny khng nh hng n vng kia.2.5.1. Cc b phn ca h thng .2.5.1.1.
ChillerH thng cho php nhiu hn 2 chiller . Cc chiller c ghp c th c
sn sut t nhiu hng , c kch thc khc nhau, cng sut khc nhau. Min l khi
ghp vo th c cng sut cung cp cho cho ti. Yu cu duy nht l tt c cc
chiller phi lm vic vi cng 1 di nhit l lnh nc.2.5.1.2. Bm nc lnh s
cp H thng bm ring bit cho mi chiller. H thng bm c ng gp chung v bm
d phng.2.5.1.3. H thng bm ring bit cho mi chiller
Hnh 2.9. H thng bm ring bit cho mi chiller Vi cu hnh ny ta vi mi
chiller ta lp 1 bm . Trng thi hot ng ca bn tng ng vi trng thi hot
ng ca chiller m n cp lu lng. H thng in ca bm s c lin ng vi h thng
in ca chiller sao cho khi bm hot ng th mi hot ng.
2.5.1.4. H thng bm c ng gp chung v bm d phng
Hnh 2.10. H thng c bm c ng gp chung v bm d phng
H thng c thm bm d phng nh trong hnh 5.2 l bm 4. Vi h thng ny cc
bm c th cung cp lu lng cho bt c chiller no . trong trng hp c 1 bm
no b hng th bm thay th s c dng thay th bm 1 cch m gin. gia ng gp v
mi my chiller c 1 van in t ( isolation valve ) c nhim v ngn khng
cho nc i qua khi chiller tng ng ngng hot ng. Nhc im ca h thng bm ny
l chi phc tp v chi ph cao.2.5.2. Bm bnh ngng Nu nh chiller c lm mt
bng nc, mi chiller s c 1 bm cho bnh ngng v thp gii nhit. 2.5.3. ng
chung ng chung cho php cc bm hot ng nhng tc dng chy khc nhau. iu ny
l cn thit v tc ca cc bm s cp khng thay i c trong khi tc ca bm th cp
li thay i.2.5.3.1. Lu lng vng s cp th cp
Hnh 2.11. Lu lng ca vng s cp th cpBm th cp c nhin v duy tr chnh
lch ct p cn thit ca h thng . Lu lng ca vng th cp lun lun phi bng
hoc ln hn lu lng vng s cp vng s cp p ng uce yu cu. Khi lu lng vng s
cp ln hn th cp n s bypass qua ng chung v u ht ca bm. Khi lu lng vng
s cp nh hn lu lng vng th cp, 1 phn nc t vng th cp s qua ng chung ha
trn vi nc cp.2.5.3.1. kch thc ng chung
Kch thc ca ng c thit k theo tc dng chy ca bm ln nht trong h
thng. Tr khng thy lc khng c vt qu 0.3m H20.
2.6. H thng bm s cp lu lng thay i
tit kim chi ph vn hnh ta c th dng h thng bm m mi bm c b iu khin
hoc s dng bin tn iu khin lu lng.Khi s dng bin tn h thng c th tit
kim c khong xp x 15 20% nng lng.Lu lng qua chiller thay i theo s
bin i ca h thng ti. Nh trong hnh 5.4 h thng c 1 van bypass dng duy
tr lu lng ti thiu tng ng 30 % lu lng qua chiller ln nht .
Hnh 2.12. H thng bm s cp lu lng thay i H thng phi c 1 gii hn hot
ng nht nh khi s bin ng ca ti l qu nhanh v s thay i lu lng c th dn n
s bin i ca nhit nhit nc lnh cung cp. S gii hn ny l la chn kh thi
nht v iu khin nhit nc cung cp trong di nh rt kh khn v phc tp. Tiu
ch c bn cho h thng ny l : Lu qua mi chiller cn phi c duy tr trong
di 0,085 0,311 m3/s . bit c chnh xc tt nht l s dng 1 cm bin lu lng
cho mi chiller. Nu nh tc nc qua chiller thay i qu nhanh, b iu khin
c th khng p ng kp. Do s thay i ca ti cn phi c gii hn khng nhiu hn
30 % mi pht.
Ti liu tham kho :HVAC Waterchillers and Cooling Towers
Fundamentals Application and Operation_2ndedition by Herbert W.
StanfordChiller plant design by Herbert W. StanfordStandand of
American Society of Heating, Refrigerating, and Air-Conditioning
Engineers (ASHRAE)Primary Secondary Chilled Water Systems By Steven
C. Severini, P.E., Member ASHRAE
SVTH: Nguyn Xun Thnh MSSV : 20106125 Page 2
