^^^ i K H O A H Q C - C O N G N G H E
Jll&l &KkeJL qua. it^^hien aht Auy. tei
BBNQ HE THONG SRY DUNG N6NG lagfNG M6T TRGfl
KIEU HON HOP B6\ LL/U TLT NHI^N
I. DAT VAN DE
Nhilu logi ndng san dgng cii, qud, hgt sau khi thu hogch thudng phai phai, sdy dl dgt dg im thich hgp cho bdo qudn. Siy ndng sdn bdng di?n, than...
ddm bdo dugc cac yeu cdu vl chit lugng san pham, V? sinh, gidm chi phi lao ddng, khdng phy thugc vdo thdi tiet, nhung lai cd chi phi cao.
Ndng lugng biic xa mat trdi (ggi tdt Id ndng lugng mgt trdi) la ngudn ndng lugng gin nhu vd tan va la mgt trong nhimg logi ndng lugng thay the triln vgng. s i y bdng ndng Iugng mdt trdi cd the nang cao chit lugng san pham.
Tuy vgy, nang lugng mgt trdi khdng re, do cac thiet bj sir dyng ndng Iugng mat trdi hi?n cd hi?u sudt chua cao. Do do, hi?n nay vi?c nghien cuu chl tgo, nang cao hi?u qud cdc thilt bj su dyng ndng lugng mat trdi vd trien khai iimg dyng chiing vao thyc tl la vin dl cd tinh cap thilt.
Ci Viet Nam ngudn ndng lugng mgt h-di cd hiu nhu quanh ndm, tri s6 tong xg kha Idn td 100 den 175 kcal/cmVndm, dac bi?t cdc viing tir mien trung trd vao.
Tdi la m$t logi ndng san cd huang vi ddc biet cua huy?n ddo Ly San, tinh Qudng Ngai, da dugc cdng nhdn thuang hieu qudc gia, vdi sdn lugng hang ndm len din khoang 2.000 tdn. Den nay, ndng dan Ly Son vdn phoi logi tdi ndi tilng ciia minh sau khi thu hogch, nen khdng dam bao chdt lugng, thdi gian bao (judn ngdn vd thdi gian phoi Idn hon nhieu so vdi say.
^ siy tdi diing ndng lugng mgt fdi kieu hdn hgp doi luu ty nhien dugc chgn nghien cuu bdi nhihig Iy do sau:
- Huy?n ddo Ly Son Id noi cd cudng dg biic xa mdt trdi vd so gid ndn^ trong ndm hrang doi ldn, phii hgp vdi h? thing say dung nang lugng mat trdi.
Mdt khdc, hi?n nay nguIn di?n d Ly Son chi dugc cung cap cho chieu sdng vao budi tdi (5gid/2 ngay) cho nen sdy bdng ndng lugng mdt trdi la phii hgp.
_ - H? thong siy dimg ndng lugng mgt hdi kieu hdn hgp cd uu diem Id tdng khd ndng lam nong vat am, cd nang suat cao.
' TS. Tnrfmg E)^ hpc Nong ISm Hu^
* Ths. Tnremg Tning hpc Giao thflng v^n tai Hue 12
Dinh ViroTig Hing', Nguyen Xudn Trung'
- Thiet bj say diing ndng lugng mdt hdi cd cau tgo dan gian; xdy dyng, che tgo de dang bSng cdc vgt lieu sdn cd tai dia phuang.
H? thing thilt bj siy bdng ndng lugng mdt trdi da nghien curu yd iing dyng d mgt sd noi nhung hi?u sd thu nhi?t thip. Chiing tdi da nghien cihi dua ra h?
thdng say gom b^ thu nhigt vd buong say (cung Id bg thu nhi#t thd 2).
Xin gidi thi?u ket qua nghien cdu h? thong say nang suit 240kg/me dung cho quy md ndng hg san xuit va kinh doanh hanh, tdi tai Ly San.
II. TINH TOAN KHA NANG LAM K H 6 VA MOT S 6 THONG S 6 CUA THI6T B( SAY
L Tinh todn he thon^ sdy 1.1. Xdc djnh lugng dm cdn bdc hai H? thong siy dugc tinh toan vdi ndng suat 240kg/me vd nguyen li?u say Id tdi da qua phai ndng dat dg dm phan vd lya Id 13%, phan than cii la 60%.
Do khoi lugng ciia vd lya so vdi thdn cua cii tdi la khdng dang kl, de thugn Igi cho vigc tinh todn, ta coi cu tdi la mgt vgt dm vdi dg im trung binh ban dau la (0[ = 60% vd dg am sau say Id tO; = 55%.
Lugng im cin bic hoi mgt mS siy la:
W ^ = G ; i i Z ^ = 2 4 0 . - ^ 2 z 5 1 = 2 6 . 6 7 kg/me lOO-fOj 100-55 Lugng toi khd sau say thu dugc:
G2 = G , - W ^ = 213,33 kg/me
Chgn thdi gian say Id T = 16 gid, tuong line vdi hai ngay ndng cd nhi?t dg tmng binh 30°C. Toe dg siy tucmg iing Id 0,31 %/h.
Khac vdi siy cac logi hgt, siy tdi cd tdc dg say cao se xay ra hi^n tugng tdi "chin", mui tdi phong rgp len, do iugng nudc boc hai d phin thdn cii khdng chuyin dugc tdi Idp vd lya dk ra ngoai.
Lugng im trung binh can boc hoi trong mgt gid:
WH ^ ™ 26,67 16 1,67 kg/h 1.2. Tinh todn cdn bdng nhi^t - dm qud trinh say Do thj I-d ciia qud trinh say (hinh 1), trong do (1) Id trgng thai khdng khi trudc bg thu nhi?t, (2) la
TAP CHI CONG NGHIEP NONG THON • SO 2 - 2011
K H O A HQC - C O N G N G H E trang thdi khdng khi sau bg thu nhi?t va (3) la trgng
thai khdng khi cuii qud trinh siy.
9 = 1 0 0 %
= d2 da Hinh 1. DS thf I-d a) Trgng thdi khdng khi trudc bg thu nhi^t Tir so li?u vl khi hgu tinh Qudng Ngai, ta chgn nhi?t dg t, = 30''C, dg dm tuang ddi tpi = 75%; vdi dp suat bao hda ciia hoi nudc d 30''C la p^i = 0,0425bar, dp suit khdng khi am Id p = 0,9933 bar.
Dg chira am ciia khdng khi:
dl = 0,622 ^'^^' P-9\Ps\
= 0,021 kg/kgKK Entanpi cua khdng khi d dilm 0 Id : li = Cpkt, + d| (r + Cpht,) = 83,72 kJ/kgKK Trong dd:
Cpk » I kJ/kgKK - nhi?t dung rieng ciia khdng khi khd.
Cph « 1,93 kJ/kgKK - nhi?t dung rieng ciia hoi nudc.
r « 2500 kJ/kg - nhi?t am hda hai ciia nudc.
b) Trgng thdi khdng khi sau bg thu nhi^t Chgn nhi?t dg khdng khi khi ra khdi bg thu nhi?t Id t2 = 50°C; vdi dp suit bdo hda ciia hai nudc d SO^C Id ps2 = 0,1235bar. Gid thilt h? thong Id kin, lugng chira dm trudc va sau bg thu nhi?t la nhu nhau cd dl = dj.
Tatinh dugc:
h= Cptt2 + di (r + Cpht2) = 104,53 kJ/kgKK Dg am tuong doi cua khdng khi sau bg thu
nhi?t: 92= -100% = 26%
(0,622+ rfj);j,j
c) Trgng thdi khdng khi cudi qud trinh sdy (5 trgng thai ndy ta co I3 = I2, chgn nhi?t dg cudi qud trinh say ti = 38"C, vdi psj = 0,0663bar.
Ta tinh dugc:
(P3 =
:^a__^£i^= 0,026 kg/kgKK r+C^t,
-100% = 60%
(0,622-F^3)/7,3 d) Tieu hao khdng khi ly thuyet
Tieu hao rieng khdng khi trong qua trinh siy ly thuyet dugc xac djnh:
lo = = 200 kgKK/kg im d^-d,
Gid thiet h? thong la kin thi lugng khdng khi khd can thiet de say 240kg tdi tir dg am 60% den dg im 55% la:
Lo=WJo = 5334kgKK Vgy, tong the ti'ch khdng khi am qua bg thu nhiet la:
V = L.Vo = 5072,6 m^
Luu lugng ddng khi di qua bg thu nhiet Id:
Vo = 5072,6 m' / 16 h = 317,04 m^/h = 0,088 mVs Khoi lugng rieng cua khdng khi trong budng siy Id:
p = ., 99333^ = 1,07 kg/m^
287 + 462 -^1(273 + /,) e) Tieu hao nhi?t cho qud trinh sdy
Tieu hao nhi?t rieng trong qua trinh say ly thuyet dugc tinh theo cdng thdc:
qo = Wh - Ii)= 4162 kJ/kg dm Tieu hao nhiet trong qua trinh say ly thuyet Id:
Q = qo-W™= 111000,5 U L3. Tinh todn bg thu nhiet vd budng sdy Vdi h? thdng siy ndy, ngoai bg thu nhiet, buong say dugc coi nhu bg thu nhiet thir hai. Do dd, di?n tich thu nhi?t bao gom cd dign tich ciia bg thu nhi?t va buong sdy. Gia thilt h? thong Id kin, tieu hao nhi?t trong qua trinh say Q ciing chinh Id lugng nhi?t hihi ich ma ddng khi nhgn dugc Qg. Di?n tich thu nhi?t dugc tinh theo cdng thuc sau:
Ac = 7./r
Chgn hi?u sudt chung cua bg thu nhiet va buong say Id rjc = 0,3. Tir tinh toan ciia phan mem HOMER version 2.76, ta cd IT = 5763 kWh/mVngay. Di?n tich thu nhi?t la:
111000,5
TAP CHf CONG NGHIEP NONG THON - SO 2- 2011 13
K H O A H Q C - C O N G N G H E Di?n tich budng sdy can dam bdo ndng sudt 240
kg/me, vdi kich thudc thiia ddt sdn cd tgi dja dilm ngliien ciru, ta chgn:
- Di?n tich buong say: 12,6m^.
- Di?n tich bd thu nhi?t: 19,42m^
Tir ket qud tinh toan tren, cd the :ao ra thiet bj say tdi cd cQ bdng ndng lugng mat trdi vdi 2 bg phan thu nhi?t cd khd nang mang lai hieu qua.
III. THIET KE, CHE T^O, XAY DylVG THIET B! SAY SMT-0,1LS
So do thilt kl dugc thi hien tren hinh 2.
Hinh 2. Sa do cau tgo h? thong sdy toi SMT- OILS l.B9thunhi§t;2. BOph^ndikchinhnhietdgia. Bu^ngsay;
4 Mai kinh trong suet; 5. Gia siy; 6. Qugt ciu; 7 L6 thoSt 1. Bg thu nhiet
Khdng khi dugc nung ndng khi di qua bg thu nhi?t nhd hi?u dng nha kinh.
Bg thu nhi?t la mgt hgp xay bdng ggch, trat vira, cd nip dgy bdng kinh trong suot day 5mm, mgt day la tam hap thy bdng fibro-cement dugc son den md, nhdm tang khd nang hip thu nhiet. Dudi mdt day cd Idp cdch nhigt bang xop day 2cm. Bg thu nhi?t cd di?n tich 13,68 m^ do tam fibro-cement cd dgng lugn sdng nen di?n tich tam thu nhi?t la 19,42 m^
BO thu nhi?t dugc dgt hudng ve phia Nam va nghieng 25° so vdi mgt phdng ngang. Khoang each gi&a mdt kinh va tim thu nhi?t 20cm.
Hlnh 3. Mgi cdt ngang bp thu nhi?l 1. Thanh ben; 2. T ^ thu nhi^t; 3. M§t kinh 4. X6p cich nhi?t ; 5. Vich d&; 6. Thanh dO ngang Bg thu nhi?t dugc ddt hudng vl phia Nam vd nghieng mgt gdc 25" so vdi mat phdng ngang.
Khodng each giira mdt kinh vd tim thu nhi^t 20cm.
14
2. Buong say
Budng say la noi diln ra sy trao doi nhi?t - im giiJa tdc nhan say vd vat siy. Buong siy can kin dl tranh that thoat nhi?t; cd ciia ra vao vd cua sd (kinh) ddng kin trong khi siy. Khdng khi dugc nung ndng d bg thu nhiet di vao tir ngang mdt sdn va thoat ra d Id thodt cd Idp qugt cau doi lim tren mai buong say.
Buong siy dugc xay bdng ggch Id, trdt v5a; mai dugc Idp kinh ddy 5mm dl sir dyng hi?u dng nhd kinh tir bdc xa mat trdi. Cd thi coi buong siy la bg thu nhi?t thir hai.
3. Gia say
Gia siy dugc chl tao bdng thep khdng ri hode thep mg kem de trdnh anh hudng den chit Iugng san pham say. Mgt gid siy gom nam khay siy xip tdng, each nhau mgt khodng 300mm, dam bao khdng cdn trd qua trinh nhgn nhi$t va thoat am. Mgt khay siy cd di?n tich l,56m^ ldm bang ludi th^p khdng ri, khdng khi ndng di tir phia dudi khay len dl dang.
Chan gia sdy dugc ldp banh xe dl thudn ti?n thay doi vj tri cdc gia siy trong buong siy. Cd ba gid say vdi tong di^n tich cac khay siy la 23,4 m^.
4. Bg phan dieu chinh nhi^t dg budng say Nhi?t dg trong buong sdy dugc dilu chinh bdng each tdng hay gidm luu lugng khdng khi nong di vdo, nhd sy thay doi gdc md cua bg thu nhi?t tit 0°
den 90°. Ban dem, cda nay dugc ddng Igi dl tranh hoi dm vao buong say.
5. Cac thiet bi khac
De nang cao hi?u qua siir dyng, h? thdng say SMT - OILS cdn dugc ldp ddt thiet bj sdy cuong hire bdng khdi Id (dot bdng than t l ong) dl sir dyng say hdnh, rong biln,... ve miia mua. Vi§c ldp dgt cac thiet bj ndy khdng anh hudng den vi?c siy bdng ndng lugng mdt trdi trong miia ndng.
IV. KET QUA 1. Ket qua thi nghi?m 1.1. Dia diem thi nghi$m
Thi nghigm tgi: Trung tdm Kilm nghi?m thulc, my pham, thyc pham Thira Thien Hul va thdn Ddng, xa An VTnh, huygn Ly San, tinh Quang Ngai gom 3 thi nghi?m vdi logi tdi Ly Son, mdi thi nghi?m 3 mdu:
- s i y trong 1 ngdy, tdi da dugc ndng hg phcri ndng tur 10 -12 ngdy trudc dd, mdi mau nang trung binh 20g.
- Say trong 1 ngay, tdi tu me say, mdi mau ndng trung binh 20g, bao quan trong hgp nhya kin.
- s i y tron^ hai ngay, vdi 240kg tdi da dugc ndng hg phai nang tir 10 -12 ngay. Tdi dugc rdi deu tren mudi hai khay say cua ba gid say, mdi khay TAP CHf CONG NGHIEP NdNG THON - SO 2 - 2011
KHOA HQC - CONG NGHE 20kg, chia lam bon ting (1- cac khay say tren, 2, 3
va 4- cdc khay siy dudi cung). Khay say tren cimg khdng cd tdi dugc che Igi bdng bao PP de trdnh dnh ndng tryc tiep vao cii tdi d tdng 1, gay "chin".
Cdc sd lieu dugc thu thap mdi gid mgt lan, bdt diu tir 7 gid va kit thiic vdo 16 gid, tuong ung vdi thdi gian nang trong ngay.
1.2. Kit qud thi nghidm
a) Dg dm tuang ddi cua cu ldi truac khi sdy Bdng I. Dg kn tuong dli ciia cu toi trudc khi sdy rr
1 2 3 4
Mau Mau 1 Mlu 2 Mau 3 Tmng binh
D9 im thSn cu <%) 59,02 60,15 60,23 59,08
D9 am vd lya (%) 12,93 12,87 13,12 12,97 b) Nhi^t dg khdng khi trong qud trinh sdy
Hinh 4. Nhi^t dg khdng khi vdo vd ra bg thu nhi^t Nhu vdy, dg chenh Ifch nhi?t dO ldn nhit la n^S^C va nhd nhit la 2°C. Vdi tim hip thy bdng vat ligu fibro-cement, kha ndng nang nhi?t ciia bg thu nhigt la khdng cao, tuy vgy, lgi phii hgp vdi yeu cdu cua vgt siy.
1-
Ngty iaj07II010
- " " ^ ^
-^^^t^,\*3Hinh 5. Nhiet do khong khi trong budng sdy Ta nhan thay:
- Nhi?t dg khdng khi d vj tri dudi khay 4 thip han nhigt dg khdng khi ra bg thu tit 0,5°C den 3,5°C.
- Nhi?t dg khdng khi d vj tri giita khay 2 va 3 chenh lech vdi nhi?t dd khdng khi ra bg thu tir -3°C din 3°C.
- Nhiet dg khdng khi d vj tri tren khay 1 cao han nhigt dg khdng khi ra bg thu tiir 0°C tdi S^C.
- Sy gia tdng chenh l?ch nhi?t dg ldn nhdt xdy ra trong khoang ba gid, bat dau tir giira trua.
Nhu vgy, cd tbi ndi, mgt lugng ldn ndng lugng mdt trdi qua mdi budng say dugc nen va thanh buong siy hap thy. Mgt phan lugng nhigt ndy tda ra vao ban d6m, thyc te den khodng 20 gid nhigt dg trong budng siy mdi cdn bdng vdi nhigt do mdi trudng. Sy chenh l?ch nhigt do cua cdc khay sdy Id khdng ldn, vi vgy, khdng anh hudng nhilu din dg ddng deu ciia me say.
c) Thay ddi dg dm khdng khi trong qud trinh sdy Sy chenh Igch dg am giira mdi trudng vd buong siy khdng Idn, dg im trong budng say nhd ban mdi trudng. Dieu nay chung td qud trinh thoat am diln ra chgm. Vdi toe do siy nhd, theo tinh todn la 0,3%/h, qua trinh chuyin im tu phan than cii ra vd lua diln ra binh thudng, dam bao chit lugng san phdm siy.
Hinh 6. Dd dm tucmg ddi cda khong khi mdi trudng vd trong buong say
TAP CHl CONG NGHIEP NONG THON - SO 2- 2011 15
KHOA HQC - CONG NGHE
d) Thay ddi dg dm phdn vd trong qud trinh sdy
Hinh 7. Dd dm tuang doi phdn vd lua T a nhgn thdy:
- S y c h e n h l?ch d g am giita c a c k h a y s i y ve cudi q u a trinh s i y la k h d n g d a n g k l , sdn p h a m say t u o n g doi d d n g deu.
- Q u a m g t d e m n g u n g s i y , i m tir p h a n than cu t i l p t y c c h u y i n ra p h i n vd lya. Q u a trinh n a y ket thiic khi p h a n thdn cii dgt dd i m can bdng.
e) Dd dm tuang doi cua cu tdi sau khi sdy Bdng 2. DO dm tuong dli ciia cii tdi sau khi sdy TT
1 2 3 4
Mdu Mau 1 M^u2 Mau 3 Tmng binh
DO dm than cu (%) 54.08 54,31 55.27 54.55
DO Sm v6 lya (%) 6,72 6,89 7,11 6,91 g) Trgng lugng tnrdc vd sau khi sdy T r g n g l u g n g t r u d c khi say: 240 k g T r g n g lugng sau khi s i y : 217,2 k g T r g n g l u g n g i m m i t di: 22,8 k g
2 . N h a n xet
San p h a m s i y c d d g a m d d n g d e u , k h d n g bj n h i l m b i n , d a m bdo y e u c a u d e b a o q u a n lau dai.
K E T LU^iN
H e t h d n g say S M T - O I L S c d cdu t a o dem gian, t i l t kiem c h i phi n d n g l u g n g , g d p p h i n b a o ve mdi t r u d n g v d n d n g c a o c h i t I u g n g san p h i m s i y . Dong thdi, h ? t h o n g s i y n d y phii h g p v d i d i l u ki?n khi h a u , kinh t l , ky thugt ciia h u y ? n ddo Ly S o n ndi ri§ng va c a c viing t r o n g tdi khdc d nam m i e n Trung ndi c h u n g . •
T A I L i e u THAM K H A O DO Minh Cuimg. 2008 Nghien clhi qu& trinh siy h^t nOng san bang thi^t bi s^y sir dyng nfing liii?ng mjt tr&i kieu doi Iuu tv nhien. Lu§n vfin th?c si ky thuSt. Truimg D91 hpc Nong lam HuO.
Pham Le Dan, D ^ g Qu6c Phu. 2005. Co so ky thu^t nhiet.
NXB Giao dye.
H o ^ g Duong Hiing. 2007. N5ng lu(;ng mSt trtri IJ thuydt va irng dyng. NXB Khoa hgc va kJ thu§t.
Nguyin van May. 2007. GiSo trinh KJ ihugt sSy nong san th\rc phdm. NXB Khoa hgc va ky thu§t.
Nguyin COng VSn 2006. Nang lu(?ng mjt trin quS trinh nhi?t vk (ing dyng. NXB Khoa hgc va ky thu$t.
Bukola 0 . Bolaji and Ayoola P. Olaiusi. Perfonnance Evaluation of a Mixed-Mode Solar Dryer. Technical Report. AU J.T. 11(4): 225-231 (Apr. 2008)
Ajay Chandak & Sunil K. Somani, Deepak Dubcy PRINCE. Design of Solar Dryer with Turboventilator and fireplace. Intemational Solar Food Processing Conference 2009.
A.O. Fagunwa, O.A. Koya, and M.O. Faborode.
Development of an Intermittent Solar Dryer for Cocoa Beans.
Agricutural Engineering Intemational: the CIGR Ejoumal, Manuscnpt number 1292. Vol. XI. July, 2009.
P.H. Hien, L.Q. Vinh, T.T.T. Thuy. T.V. Tuan. 2009.
Development of solar- assisted dryer for food and farm crops.
Food & Process Engineering Institute Division of ASABE. Vol.
52(4): 1255-1259.
Arun S. Mujumdar. 2007. Hanbook of Industrial Drying.
CRC Press.
P E R F O R M A N C E E V A L U A T I O N O F A M D C E D - M O D E S O L A R D R Y E R W I T H T U R B O V E N T I L A T O R Dinh Vuong Hung, Nguyen Xuan Tnmg.
SUMMARY
This paper presents the design, construction and performance evaluation of a mixed-mode solar dryer with turboventilator for galic preservation. In the dryer, the heated air from a separate solar collector is passed through a grain bed, and al the same time, the drying cabinet absorbs solar energy directly through the transparent roof. The results obtained during the test period revealed that the temperatures inside the dryer and solar collector were much higher than the ambient temperature during most hours of the day-light. The temperature rise inside the drying cabinet was up to 32% for about three hours immediately after 12.00h (noon). The drying rate and system efficiency were 0.62 kg/hand57.5%respectively. The rapid rate of drying in the dryer reveals its ability to dry food items reasonably rapidly to a safe moisture level.
Ngudi phan bifn: G&TSKR P h ^ VSn Lang
TAP CHl' CONG NGHI$P N 6 N G THON - SO 2 - 2011
