18'NLN-118'7/2014
7 DANH GIA KHA NANG CAP NHIET CUA BO THU Bl/C XA MAT TR0I DANG MANG PARABOL TRONG DIEU KIEN THdl TIET QUA TP HO CHI MINH EVALUATING THE HEAT CAPACITY OF PARABOLIC TROUGH SOLAR COLLECTOR WORKING IN
CONDITIONS OF HO CHI MINH CITY
KS. NGO THieN TCr '. ThS VO KI^N QUOC, KS. VO HAI DyaNG, GS. TS LE CH( HIEP.
©H Bach Khoa TP. Hd Chi Minii Theo qui trinh khw mudi nw6c biin bing phuung phiip phun - t^ch Sm, nwdc biSn cin phii dwqc hSmndng d4n nhim do khoang 60 °C - 85 °C trwoc khi cip vao budng phun - fdcrt im. Nhim giii quySt y&u ciu n§u tren, nhdm nghien cwu dang nhim din mot s6 giii phap. trong d6 c6 giii phip sii dung bo thu dang mang Cic kit qui nghi&n cwu ly thuyit va thwc nghiem cho thiy. trong cic thing khoing tir thing 1din thing 4 twong O'ng v&i diiu ki$n th&i tiSt cua Tp HCM, bq thu dang ming c6 thi d^p Crng tit y§u ciu da neu vdi hieu suit khoang tw 60-68% Cic kit qui nghien cOv trinh biy trong bii bio li ca sd di nhom nghidn cO'U lya chon phuung in cip nhi$t cho td hop khu- mudi nw&c biSn bing phwong phip phun - tich im sau niy.
Bang cac ky h i | u sip di;ng
X, y, f: Ban kinfi, dp cao, tieu cy bp thu dang mang, m Qu: Nhi?t iLFcng c6 icli bp thu nhgn du'p'c, W rto: Hi^u suat quang hpc
tab • Nhiet dp be m^t 6ng filp thy, °C ta'. Nhi^t dp moi tryang xung quanh, °C tc: Nhiet dp png thuy tinh trong suot, °C ts'. Nhiet dp hieu dung cCia b l u trai, °C Gb : Cu-ong dp tia tryc xg, W/m^
Aa. Dien tich be mgt hu-ng tia tryc xg, m^
Aat, A,:: Dien tjch ong hip thu va ong thuy tinh trong su6t bac phu ong h^p thy, m
CR- Ty s6 tap trung
£ab, Ec: £>9 den bi m$t hip thu va be m^t dng thuy tmh Oab-c, ar.ab^:: H? SO ton that nhiet d6i lyu va btpc xg ty ong hap thy den ong thuy tinh, W/(m^.K)
ac-a,ar,c.a Hp SO t6n that nhi^t d6i \wu va buc xa ty ong thuy tinh ra moi truccng, W/(m^.K)
CT: i-ling so Stefan - Boltzmann
Rab, fie; Ban kinh ong hap thu. ban kinh ong thuy tinh, m
ID/kTVANOe
IVld hinh l^hy muoi bdng phifong phap phun - tdch Im Id md hinh san xuat nyo'c sach vdi dieu kidn nud'c bien tru-o'c khi vdo md hinh phai dii'p'c gia nhidt trong khoang tif 6(fC - 8^C [1], Be ddp O'ng ydu cau 36. nhdm tdc gia da su' dyng mo hinh bO thu dang mdng de gia nhidt nu'O'c vdi u-u diem nhidt d0 nydc dat dug'c d' nhidt do cao trong khoang thd'i gian ng^n vd cd the ho?t ddng song song kit hop nhdm dat hidu qua toi wu nhat B6 thu dang mdng Id loai bd thu tap trung md nhidt dd chat Idng lam vide cd the Idn ddn 250°C tuy vao loai mdi chat va tuy vdo myc dich sy dyng [2]
Ve nguydn tdc, nude trong md hinh bd thu dgng mdng phai \i nude bien, nhung do didu kidn chua cd sdn nguon nud'c bien phuc vy eho qua trinh thyc nghidm^ ndn nhdm nghidn cuu da su dung nude sinh hoat de tien hanh thyc nghiem Cdc thdng so nhidt vat ly cua nud'c bien va nude sinh hoat eho thay hodn todn cd the su dyng cae ket ludn rut ra ti> cae nghidn cuu nay cho trudng hop cua nude bien [3].
*Email: [email protected] vn
2. CO S d LY THUYDT V i BO THU DiOiNG MANG Ve mdt nguydn IJ, bd thu dang mdng Idm vide chtj yeu vdi cdc tia tryc xa, sau dd phan xa tdp trung tai dudng tap hp'p ode tidu diem Tgi dudng tdp hp'p cdc tidu diem, lap 6ng hap thy bdng ddng ddn nude dup'c son den nhdm tdng kha ndng hap thu eudng do buc xa, ben ngodi ong hap thy 3\jeqc bao bpc bdng ong thuy tinh tgo hidu ung nhd kinh vd han che t6n that nhipt ra mdi trud'ng. V4 nguydn tic, hfy thu dang mdng cdn phdi du-pc xoay theo mat tr^i nhdm dam bao cac tia tryc xa ed the dup'c phan chilu tot nhdt den bd mdt hap thy cua bd thu.
Can chu y den mdt thdng so mang tinh ddc thii cua loai bd thu ndy, dd Id ty so giua didn tich be mdt hung cde tia true xg A^ va didn tieh be mat tiep nhdn Ar. ta goi dd Id ty s6 tap trung CR (Concentration Ratio) [4] Ty sd tdp trung CR ddi vdi md hinh bd thu dang mdng dupe chgn trong khoang tu 10 - 30 [5]
2.1. Cac thong so (rang mo hinh bg thu dang ming
Bd thu dang mdng Id loai bO thu tdp trung cd bidn dang thoa phuong trinh sau'
4 . / '
(1)D^fa vao nhu cau sau 3 gio 14m viec flau (ti> 8h a§n 11 h) vdi lu'ong nwOc 40 lit u-ng vdi nhl^t 39 ySu cau nam trong khoang 60 - 85 °C, ta tim dypc kich thLfdc b6 thu dang mSng nhu- hinh 1.
Hinh 1. CAc kich thiKK ftp f/iu d^ng mang
NLN* 118-7/2014*19
0 hinh 1 Id bd thu dang mang vdi cdc kich thudc cy the nhu tren hinh ve, ong hap thy dat tai d u d n g tidu diem cua bd thu. Tai thi nghidm ndy, bd thu dang mdng d u p c xoay theo mdt trdi c u 15 phut/Ian bdng thu cdng (xoay bdng tay) de ddn buc xa mdt trdi tdp trung tai d u d n g tidu diem.
1 Nuucvao;
2 BQ thu d^ng mang.
3 Nifoc ra:
4: Thung chu'a
Hinh 2. Nguy&n 1^ ho9t dgng cua bp thu d^ng mang Qud trinh Idm ndng n u d e d u p e the hidn qua hinh 2, nude ben trong ong ddng sau khi nhdn buc xa tdp trung tiF bd thu mdng. nhidt dp n u d e tang len Idm eho khoi lupng ndng cCia n u d e giam, nude nhidt dd eao se di len trdn vd n u d e nhidt do thap cd khoi luang rieng Idn han se di xu6ng d u d i tao thdnh ddng dot luu t y nhidn tuan hodn khdp kin. Sau thdi gian Idm vide thI nhipt dp n u d e trong thCing ehCra sd dupe tdng Idn vd dat dup'c nhidt dd nhdt dinh.
2.2. Hieu s u d t n h i ^ t cua b o thu d ^ n g mang T u tdi lidu [6], ta cd cdc cdng thCre xde dinh hidu sulit bd thu dang mdng
Hd so trao doi nhidt bii'c xa giOa dng thuy tmh trong suot vd bdu trdi:
«,,,.„ =e^.a.(T^ +T^).(T- +T^).^^'
, W / ( m ^ K) (3)
1+-
W/(m^.K) (2) Hd so bupc xa duo'c tuyen tinh hda ar.atn: gi&a be mdt hap thu vd ong thuy tinh trong sudt'
Nhidt lupng t6n that di tLf be mat hdp thy den Idp phu trong su6t, Qai^c.
a » - , = ' i ^ •(«,»-,•+«,,„-,-, )-(7;. - T.)' w c )
Nhiet lu'p'ng ton that tO lop phu trong suot ra mdi tru'dng b6n ngo^i, Qc-a'a . „ = 4 . - C a . - „ +a,...-„)-(7'c -T,l W Cf che do lam vlec 6n dmh:
NhiSt lu'p'ng c i Ich b6 thu n h | n d u g c \i:
Hieu suat bo thu dang mang:
(5)
(6) (7)
3. MO HINH THg'C NGHIEM BO THU DANG MANG Til' ket qua tinh toSn ta duv/c bang so li&u c^c kich thu'dc ch^ tao cua b6 thu dang m i n g d bang 1.
Bang 1' CAc l<ich thu^c cOa bC thu dang mcing Be rpng mang, m
Tieu Cl/ mang, m Goc nghieng mang, do Chieu d a i m ^ n g , m ChiSu cao mSng, m C h i l u ddi dng hSp thu, m Ou'O'ng kinh ngoSi 6ng h^p thg, m Ov/cfng kinh trong ong h^p thu, m Du-cyng kinh 6ng thuy tmh, m
1,2 0,36 15
1,5 0,25
1.5 0,042
0,04 0,055
Hinh 3. M6 hinh tip thu dang m6ng 0 hinh 3, bd mdt bd thu dang mdng cd thd d u p c bao phu b i n g nhidu loai vat lidu nhu: g i l y bae hodc guang phan xa., tdp trung ndng lupng den ong h i p thy dan nude ddt tai d u d n g tidu diem cua bp thu dang mdng hinh 4.
(8)
Hinh 4 NSng lu^g m^t trtn tap trung t^i duimg iiSu diim cOa b0 thu d^ng mdng
4. K £ T Q U A V A T H A O LUAN
Nhdm tdc gia b i t d I u do dac t h y c nghidm t u thdng 10/2013 - 04/2014 n h i m ddnh gid tinh hi0u qua cua md hinh bp thu dgng mdng. Qud trinh t h y c nghidm d u p c tien hdnh t?i BO mdn Cdng Nghd Nhidt Lanh - Khoa C o Khi - DH Bdeh Khoa TpHCM Ci^ng vdi md hinh, nhdm tdc gia s u dyng thiet bj Teste 735 de do nhidt dp tai cde vi tri cCia md hinh. Lupng n u d e trong qua trinh thyc nghidm id 40 lit,
Tgi cdc dieu kidn thdi tidt cua Tp.HCM, so lidu do cudng dd buc xa (CDBX) mdi lan 5 phut t u 8h den 16h. Tren c d s o rat nhieu ket qua do dac thuc nghidm trong khoang thdi gian ti> thang 10/2013 - 04/2014. V d i mye dich minh hpa, nhdm tdc gid trinh
2 0 * NLN-118* 7/2014
bay cac kdt qua do dac d u p c trong ngay 24/03/2014 de khao sat gia tn nhidt dp tai eac vi tri trdn md hinh va hidu sudt cua bd thu dgng mang.
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nnpm
Hinh 5 Bo thi nhlet dp (gi cic vi tri theo cudng d9 bOc xa va thbi gian trong ngay
Tai hinh 5, nhidt dp nude ban dau la 28,5°C vd dupe tien hdnh gia nhidt sau khoang thdi gian 3 gid ddu (8h - 11h). Luc 11 gid, nhiptdp nude ra la63,5°C vd ben trong la 62,8°C. O'ng vdi nhidt dp nay ta cd the s u dung ket hop md hinh bd thu dang mang vdi md hinh khu muoi bdng phuong phap phun - tach am.
Nude hoi ve sau qud trinh k h u mudi d u o c cap trd lai bp thu de tiep tyc qud trinh gia nhidt.
Ngay 24/3/2014
Hinh 6. Hi$u suat theo gio cua bg thu d$ng m6ng Do s u thay doi c u d n g dp b u e xa theo g i d d i n d i n s u thay doi hidu sudt cua bd thu dang mdng hinh 6 Ttf 8 h - 1 1 h hidu sudt tdng ddn tif 45 % - 6 0
%, t u l l h - 16h hidu sudt khdng thay doi nhieu chi dao ddng trong khoang t u 60 - 68 %.
*/ *•/ -V V -V -V -V V ^
Hinh 7. Nhi$t dO nw&c ra tu- thing 01 ~ 04/2014
Tai hinh 7 Id s u thay doi nhidt dd nude ra trong ngdy vd duoc khao sdt qua cde ngdy ti> 15/01 - 03/04/2014, Ta thdy, nhidt dd cao nhat trong thdng 1 ndm trong khoang 58 - 67 °C. Thdng 2,3,4 nhidt dp tuong iJng 68,5°C; 80,1 °C, 76,3 °C.
5. K^T LUAN
Qua cde sd lieu k i t qua tinh todn vd do dac thuc nghidm t u thdng 10/2013 den thdng 04/2014, nhdm tac gia ed mpt s6 kdt Iuan n h u sau: t u thdng 10- 12/2013 thdi diem dd tai TpHCM trdi n h i l u mdy, thdnh phan tdn xa Idn ndn md hinh bd thu dang mdng hoat ddng hdu n h u khdng hidu qua T u thdng 01 - 04/2014, bdu trdi trong xanh vd ed d u p c mdt so kdt qua rdt kha quan, IVld hinh bd thu dgng mdng cd hidu sudt khd eao 60 - 68 %. Do dd, vide ung dyng bd thu dang mdng vdo md hinh k h u muoi bdng p h u a n g phdp phun - tdch am Id mdt trong nhung giai phap ed the x e m xdt ddn. Ngodi ra, ta cdn cd the s u dung md hinh ndy cho nhieu nhu eau khdc nhau tuy vdo m y c dich s u dyng,
ABSTRACT
The process of solar powered desalination based on humidirication/dehumidification shows that the sea water should be heated to 60 °C - 85 °C before send- ing to the humidification/dehumidification chamber In order to solve the problem, several options including also the parabolic trough solar collector are under the consideration It is determined by the theoretical and experimental results that, in conditions of HCMC from January to April, the parabolic trough solar collector can satisfy the mentioned-above demand with the efficiency ranging from 60 % - 68 %. The results shown in the paper are taken as the basic inputs in order to select the final option of heating the later desalination system.
TAI LIEU THAM K H A O
[1] EHAmer, H Kotb, GH.Mostafa, A.R.EI-Ghalban - Theo- retical and experimental investigation of humidiUcation dehumidification desalination unit - Mechanical Power Engineer- ing Department, Faculty of Engineenng, Menoufiya University, ShebinEI-Kom, Egypt, 2009, pp 949 - 959,
[2] Dirk Krueger, Alfred Heller, Klaus Hennecke and Karsten Duer - Parabolic Trough Collectors For District Heating Systems At High Latitudes - Solare Energietechnik, Deutsches Zentrum fQr Luft- und Raumfahrt eV. (DLR), Linder HOhe, 51170 Koln, Ger- many, 2000, pp 1 - 2
[3] Mostafa H. Sharqawy, John H, Lienhard V and Syed M Zubair - Thermophysical Properties of Seawater. A Review of Existing Con-elations and Data. Desalination and Water Treat- ment, 2010, p,9.
[4] John A Duffie, William A. Beckman - Solar Engineenng Of Thennal Processes. John Wiiey & Sons, Inc, 1980, pp 333 - 336
[5] BS Magal - Solar Power Enngineenng - Department of Mechanical Engineenng Indian Institute of Technology Bombay, 1994,pp1l3-115
[61 L6 Chi Hi#p - May Unh Hip Thu Trong Ky Thu$t Bliu Hda Khdng KhI-UXB Dai hpc Quoc Gia TpHCM, 2008, pp 402 - 404.
Phan bien: PGS. TS Nguyen DCiv Lgi
