c d S6 KY THUAT HA TANG . NANG LaciNG • MOI TRU6NG
THAP GIAI NHIET KHO (DRY COOLER)
MOT BIEN Tl/dNG NGUY HIEM CUA DIEU HOA KHONG KHI
PGS. TS. N G U Y I N OliC L 0 I Vien Nhiet Lanh DHBK Ha noi - Tel. 0982288995
Tom tit
Bdi viit phan tfch nhiJng nhi/dc diem nghiem trong cua thclp giSi nhiet kho khi dimg cho chiller dilu hoa khong khi (gmp- il Sufc) so vdi thap giai nhiet thong thi/dng va chi ra rjng thdp giai nhiet kho khdng phai la thilt bj ki thudt dilu hoa khdng khi vi Chiller rat nhay cSm vdi nhiet do. Neu iJng dung tai Hei Npi, nang suSt lanh giam khoang 15%, dien nSng tieu tin tang Ign din 58%, cac thong s6 van hanh xlu di rit nhanh. Thap giai nhiet kho chi cd the ufng dung de giai nhiet cho oSc dong cd, may phat, Id phan i/ng.. .la cac thilt bi it nhay ckm vdi nhiet do hdn.
Abstract
There exists a nevir application of the dry cooler for water cooled water chiller (gmp-il - Germany) thus this paper aims to analyze the disadvantages of the dry cooler compared to the normal cooling tower and to declare that the dry cooler Is not suitable for chiller in air conditioning technology and application. The use of the dry cooler for water cooled water chiller in Hanoi can reduce cooling capacity up to 15% and the can increase the energy consumption up to 58%. Furthermore, all operation characteristics become much worse. In practice, the dry coolers are only suitable tor cooling motors, generators, reactors e.g. effectively.
1. Md dau
Thap giai nhiet thdng thudng trong ky thuat d i l u hda khdng khi (OHKK) dupe hieu la mdt thilt bj dang thap, ed nudc phun t i / tren xudng va quat gid di ngudc ehilu td dudi len de lam mat nude giai nhiet ra td binh ngung nhd bay hoi mdt phin nudc t u i n hoan vao khdng khi (xem hinh 1). Nhiet dp nudc giai nhiet ra r i t thip, chi cao hon nhiet dp udt ngoai trdi 3 d i n 5°C.
« Hinh 1
Cdn mdt loai thap giai nhiet khae gpi la thap giai nhiet khd (dry cooler). Hinh 2 gidi thieu dry cooler.
Ngudi ta chi sir dung loai dry cooler niy delam mat eho may phat dien trong eac nhi may dien, mdt so loai Id phan ung trong cdng nghiep hda ehit, dgng
ca (vi du ddng cad td)... Ly do la vi nhiet dp nudc giai nhiet ra ciia loai nay r i t cao, eao hon so vdi thap giai nhiet thudng khoang 13°C. Odng ed, may phat, Id phan img... la cae thilt bj lam viec d nhiet dp cao, it nhay cam vdi nhiet dp nude giai nhiet. Dry cooler sd dung hieu qua eho eae thilt bj nay vi nudc t u i n hoan trong he thdng kin nen b l mat trao doi nhiet khdng bj ddng can, ling biin, gay an mon eung nhu khdng bj hao hut nude do bay hoi. Nhung dry cooler khdng bao gid dupe sd dung de lam mat cho he thdng OHKK vl he thdng OHKK r i t nhay cam vdi nhiet dp ngung tu.
Hinh 2
Tuy nhien, hien nay ed nht/ng cdng trinh OHKK Idn dupe chuyen gia nudc ngoai (gmp-il ciia Odc)
N G l / d l XAY Dl/NG SO THANG 8 & 9 • 2012
THAP GIAI NHIET KHO (DRY COOLER)...
thiet ke da sirdung thap giai nhiet khd thay cho thap giai nhiet thdng thudng vi mpt li do nao dd. So vdi thap giai nhiet thudng, hau qua eiia nd r i t tai hai, dd la nhiet dp ngung tu tang khoang 13°C, nang suit lanh giarp 15%, ton t h i t nang luong tang d i n 58%, chi phi d i u tutang len, dp an toan va dp tin cay thilt bi giam, tuoi thp thilt bj giam... Qua bai viet nay Chung tdi se phan tieh so sanh eac ehi tieu, thdng sd de chi/ng td r i n g thap giai nhiet khd khdng phai la thilt bi ciia ky thuat lanh va OHKK.
2. Nguyen li c l u tao cua he thdng OHKK chiller vdi thap giai nhiet kho
Hinh 3 gidi thieu nguyen ly c l u tao eua he thdng OHKK ed chiller giai nhiet nude vdi thap giai nhiet khd.
HialiS
I—O^
He thdng gdm chiller 1 ( l a - May nen va ddng co, lb- Binh ngung tu, l e - Binh bay hoi), he thing FCU, AHU 2 va bom nude lanh 3, he thdng giai nhiet ngung tu gdm thap giai nhiet khd ed quat 5 va bom nude 4. Nhu vay nude giai nhiet t u i n hoan trong he thing kin, thu nhiet ngung tu d binh bay hdi rdi thai cho khdng khi nhd gian trao doi nhiet ed quat 5.
3. Ti'nh toan ch4 do van hanh vdl gia thilt OHKK d p 1 tai Ha Noi
3a. Chi do van hanh vdi thip giai nhiet thudng
Nhiet dp ngoai nha (TCVN 5687-2010 [4]) 1^=
37,8°C, dp am (pn= 53%. Tra dd thi l-d dUdc nhiet dp Udt ngoai nha 29,1°C. Khi chpn thap giai nhiet vdi he s l hieu chinh phti hpp ta dupe nhiet dp nude ra khdi thap de vao giai nhiet binh ngung la t„,= 32°C, nhu vay nudc giai nhiet ra t,^= 37°C. Nhiet dp ngung tu se khoang 42''C.
3b. Chi do van hanh vdi thip giai nhiet khd Nhiet dp va dp am ngoai nha nhu tren da neu.
Nhung day la gian kin nen khdng ldi dung dupe dp am t h i p cua khdng khi ngoai nha. Gmp-il chpn dp chenh nhiet dp trao doi nhiet hieu qua la 7°C de thilt k l thap giai nhiet khd va l i y trdn nhiet dp nude ra khdi gian sau khi dupfc lam mat la 45°C. Vay nhiet dp nude vao thap giai nhiet khd se la 50°C. Nhiet dp ngung tu trudng hpp nay se la 55°C, eao hon so vdi thap giai nhiet thudng la 13°C.
4. Nhu'ng thong sd chi'nh ciia he thdng DHKK He thdng OHKK gdm cac thilt bj ehinh nhu sau (xem hinh 5 trang 45):
8 to chiller may nen true vi't mdi c h i t lanh
R134a nang suat lanh mdi to 1060 kW, tong nang suit lanh 8480 kW d d i l u kien van hanh vdi thap giai nhiet khd nhu neu d mijcjBb va nhiet dp nude lanh vao binh bay hoi 14°C, ra 8°C, edng suit tieu thu tren true N1= 8x 277,4= 2219,2 kW.
Tong edng s u i t eiia bom nudc lanh so d p va thd d p N2= 8x 11 kW+ 4x 15 kW = 148 kW.
901 FCU ndi dng gid, 252 cassette, 16 FCU cabin, 53 FCU g i l u tudng vdi tong edng suit ddng CO l i p dat la N3= 367 kW.
Tong edng suat eua bom nude giai nhiet s d c l p va thdcap N4= 8x11 kW + 8x 22 kW = 264 kW.
Tong cdng s u i t ciia 24 thap giai nhiet khd N5=
24x 6x 0,6 kW = 86,4 kW.
5. So sanh hieu qua nang lu'Ong COP ciia chiller
Theo thilt k l thi day la to chiller true vit thdng dung nang suit lanh d d i l u kien tieu ehuan 350 RT, nhung tiiy theo san pham ciia tdng hang, nang suit lanh nay cd the thay doi khac nhau cpng trd vai %.
Hinh 4 gidi thieu 60 lieu eua chiller may nen true vit thdng dung mdi c h i t lanh R134a dung theo catalog ky thuat eiia hang Daikin, hoan toan tucmg dUdng vdi chiller cdng trinh da chpn de tinh toan.
True tung bieu diln he sd COP, cdn true hoanh
COP 6
5
4
3
? 5,65
- . ^ ^ 1 5
NSm ngoai phgm 1 vi lam vi§c 1
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37"C Hinli 4
45'C 50*C t NhpSt as nuac giai nhi^t "^
bieu dien nhiet dp nude giai nhiet ra khoi binh ngung. Qua dd thj tren, khi lam viee d eiing d i l u kien OHKK d p 1 d Ha Npi, vdi thap giai nhiet thudng, chiller ed COP= 5,65 kW/kW, cdn khi lam viee vdi thap giai nhiet khd COP eiia chiller chi cdn lai 3,58, giam m i t 37%.
6 day cung d n phai nhin manh rang, t i t ea cae chiller thdng thudng cd gidi han nudc giai nhiet ra tdi da la 45°C, nen vung ti/ 45 d i n 50°C la n i m ngoai viing lam viee eho phep, va dudng net ddt eiia COP la dudng ngoai suy, khdng ed trong catalog.
6. So sanh tieu thu nang lu'p'ng
Oe so sanh tieu thu nang luong, chiing tdi t i l n hanh tinh ehi sd tieu thu nang lUdng rieng PIC (Power Input per Capacity) vdi P1C= 1/COP va tinh ra % de d l theo ddi.
Nhu vay tieu thu nang lupng dien ciia trudng hdp thap giai nhiet kho tang them khoang 58% so vdi NGl/dl XAY Dl/NG SO THANG 8&9 • 2012
Bang 1
Nhiet do flUdc giii nhi$t r a t ^ , X
COP kW lanhAW m
PIC(=1/C0P) kW difn/kW lanh
% dien tieu t6n khi lay tai 37°C a 100%
37
5,65 0,1770 100
40
5,15 0,1942 110,0
45
4,38 0,2283 129,0
50°C (ngoai suy) 3,58 0,2793 157,8%
t h a p giai nhiet t h d n g t h u d n g . N e u gia t h i l t he thdng van hanh d i y tai va thdi gian 10 g i d mpt ngay thi dien nang tieu thu tang t h e m khoang 11.300 k W h , phat thai t h e m vao mdi trudng mpt lupng khi nha kinh la 11,3 t i n CO2 mdi ngay (theo s6 lieu c i i a N g a n hang t h i gidi trong D u an phat trien Doanh nghiep v u a va n h d d V i e t Nam).
C h u n g ta d i u b i l t , may d i l u hda khdng khi la thiet bj tieu ton dien nang nhieu nhat eiia tda nha.
Chi p h i dau t u d a Idn n h u n g tien dien tieu ton de van hanh n d edn Idn hon r i t n h i l u . N l u van hanh den h i t tuoi thp c i i a may thi t i l n dien ed the g I p hang ehuc, hang tram lan v d n dau t u ban d a u . T h e o [9], ehi phi d i u tuban d i u chilm khoang 4-10%, chi phi bao dudng chiem 1-2% con lai la chi phi tien dien 90^95%. Chinh vi vay, tiet kiem dupc mpt vai phan tram dien nang da cd y nghTa thi tiet kiem den 58%
nhu trudng hpp d day thuc su ed y nghTa rat to Idn.
7. So sanh nang suit lanh, tinh lai sd chiller yeu cau
Theo catalog may, van hanh vdi thap giai nhiet khd, nang suit lanh mdi chiller la 1060 kW. N l u sir dung thap giai nhiet thdng thudng nang suit lanh se tang khoang 15% len 1219 kW. Sd chiller yeu c l u se la n(;h= 8.1060/1219= 6,96 to. Nhu vay khi diing thap giai nhiet thdng thudng chi d n 7 chiller, cd the giam bdt dUdc mpt chiller. T i l t kiem dupe mpt chiller ddng nghTa vdi viec tiet kiem dupc toan bp cae may va thiet bi di kem de phuc vu eho nd nhu bom nude ndng, bdm nudc lanh, thap giai nhiet, dudng dng, van, cac thilt bj tuddng...
8. Sd dung Thap giai nhiet kho la trai vdi QCXDVN 09:2005 [1]
Quy chuan Xay dung Viet Nam QCXDVN 09:2005 la quy e h l b i t bude ddi vdi mpi cdng trinh xay dung ed dien tich td 300m^ trd len, trong dd bang 5.2 quy dinh chiller giai nhiet nude true vit nang suit lanh ldm hdn va bing 1055 kW (350 RT) thi COP phai dat tdi thieu 5,50. Khi sir dung vdi thap
^ ai nhiet khd thi khdng bao gid cd the dat dupe gia trj nay.
Tieu chuan Viet nam TCVN 5687-1992 [2], tieu ehuan ciia Lien Xd cu, tieu chuan ve OHKK eiia Trung Qude [3] va tieu ehuan eiia nhilu nude tren t h i gidi d i u quy dinh nhiet dp nude vao giai nhiet eho binh ngung tdi da la 32 d i n 33°C tUdng dng vdi nude giai nhiet ra la 37 d i n 38°C ehd khdng bao gid
THAP GIAI NHIET K H " f " " V COOLER)...
len tdi 50°C nhu phudng an thilt k l da neu.
9. So sanh cac chi tieu khac
Khi sd dung thap giai nhiet khd, nhiet dp ngung tu tang 13°C, ap suit ngung tu tang khoang 40%
so vdi khi diing thap giai nhiet thdng thudng nen hit sdc khong an toan vi nguy co rd ri mdi chat, tham chi no vd thilt bj, tudi thp giam manh do phai van hanh d d i l u kien khie nghiet, nhiet dp dau boi tron tang tuong img se lam d i u nhanh lao hda, boi tron kem... Dp tin cay va dp an toan thilt bj cung giam.
Khdng ai cd the khing dinh mdc dp anh hudng lau dai se nhu t h i nao ddi vdi eong trinh.
Khi sir dung thap giai nhiet thudng se cd nht/ng nhudc diem eiia loai thap nay la binh ngung co the bi ddng can, ling bun, han gi va an mdn trong 6ng trao doi nhiet ciia binh ngung, cung nhu phai tieu tdn mpt luong nude nhit djnh de bay hdi va xa can de duy tri chat lupng nudc khdng doi. Nhung tat ca nhCrng nhude diem dd d i u cd the khic phuc mot each de giang, vi du cd the sir dijng cac loai hoa chat phii hpp de loai trd viee ddng can, an mon va ehdng sU phat trien nam mdc, vi trimg, vi khuan...
Viee ve sinh bao dudng djnh ky 3-6 thang/lln cho binh ngung va thap giai nhiet la qua quen thuoc cf Viet Nam hien nay. Khi sd dung thap giai nhiet thudng cho cdng trinh nay can phai tieu ton khoang 30mVh nude khi chay d i y tai la khdng dang ke so vdi nhirng gi ma thap giai nhiet thdng thudng mang lai.
10. Kit luan
Vdi nhi/ng phan tich d tren chiing ta thiy, thap giai nhiet khd chi i/ng dung hieu qua de giai nhiet cho nhirng thilt bj lam viec d nhiet dp cao nhu cac dpng cd, may phat dien, eac Id phan irng hda hoc...
chd khdng the sd dung de giai nhiet cho chiller giai nhiet nudc trong he thdng OHKK. Oat thap giai nhiet khd vao he thdng OHKK la dat nhim chd.
Sd dung thap giai nhiet khd cung la trai vdi QCXDVN 09:2005 hien hanh. Vi vay cac nha thilt k l , l i p dat he thdng OHKK d n phai tranh xa thap giai nhiet khd. Va thue t l la hien nay d Viet Nam cung chua cd he thdng OHKK trung tam nude nao sd dung thap giai nhiet khd. Sis dung thap giai nhiet khd eung la di ngudc lai chinh sach t i l t kiem narig lupmg va bao ve mdi trudng eiia Chinh phii va Qu6c hpi nude Viet nam [5,6,7,8].Q
1ai lieu tham khao
1. Bo Xay Di/ng Quy chuan Xiy di/ng Viet nam QCXDVN 09:2005, Cac cong trinh xay dung sddung nang iuong cd hieu qui. NXB Xay di/ng.
2. TCVN 5687-1992 Thdng gid dieu hda khdng khi, sUdi im, NXB Xay difng.
3. GB 50019-2003 National Standard of the People's Republic of China: Code lor Design of Heating Ventilation and Air Conditioning
4. TCVN 5687-2010 Thdng gid va Dieu hda khong khi. NXB Xay di/ng.
5. Nghi dinh s6 102/2003/NO-CP: Sddung nang Mng tiit kiem va hieu qua.
N C a d l XAY Dl/NG SO THANG 8&9 • 2012
T H A P G I A I N H I E T K H O ( D R Y C O O L E R ) .
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6. Nghi djnh s6 21/201 l/Nfl-CP: Sd dijng ning lugng tiit kiem vi DUng, 2007.
hieu qua. 9. De tai NCKH: B2008-01 -154: Ning cao Hieu qua Sd dung Ning 7. Luat Suf dung NSng li/flng Tiet kiem va Hieu qua so 50/2010/QH12. Mng, giim phit thai khi nhi kinh trong cac toa nha cao ting d Viet nam.
8. Bg Xay difng: Ouy chuan Xiy dung Viet nam. Tap 1,2, NXB Xay 6/2012.
NCadl XAY Dl/NG SO THANG 8&9 • 2012