KHOA HOC - CONG NGHE NGHIEN ClhJ, TiNH TOAN NHIET CHO HE THONG SAY MIEN DONG QUY MO LANG NGHE OHA NQI Ngd Xudn Bgi', Tg Hong Bite' TOM TAT Miin dong Id mdt logi thuc phdm dgng sgi dugc sdn xudt tie bgi cu cdy dong riing Vdn di cdn nghien ciru hien Id ndng cao chdt lirong sdn phdm ddm bdo ve sinh an todn thirc phdm, tiet kiem ndng lugng vd bdo ve mdi truong qud trinh sdn xudt mien dong Viec tinh lodn thiit ki he thong sdy miin dong phu hgp quy mo ldng nghe la mgt viec ldm cdn thiet gop phdn xdy dimg nong thon mai a Viet Nam Bdi bdo trinh bdy kit qud nghien ciru vi tinh todn nhiel cho qud trmh sdy lu mgt hi thong sdy mien dong dugc thiit ki cd the chi tgo vd dua vdo dp dung a ldng nghe RESEARCH, MONITOR HEAT FOR ARROWROOT VERMICELLI DRYER SYSTEM AT VILLAGE SCALE HA NOI Ngo Xuan Dai', Ta Hong Duc^ SUMMARY Arrowroot vermicelli is a fibrous food that is produced from arrowroot flour, Matters on the current research is to improve the quality of products, ensure the safety of food, save expenditure energy and environmental protection in the production process of vermicelli The design of vermicelli drying system matching village scale in Hanoi is a necessary work to contribute to building new rural areas in Vietnam The paper presents results of research and computational heat for drying from a drying system which is considered vermicelli to designed and applied for manufacture Keywords: Arrowroot vermicelli, arrowroot, dryer system I BAT VANDE Vide lam khd mien dong bang phuang phap phoi ndng theo truydn thdng cd rdt nhidu nhupc didm nhu: Khdng chu dpng dupc kd hoach san xudt vi phu thpc vao thdi tidt San phdm mien dong phoi ndng ngoai trdi chu yeu tgi cac dia didm gdn dudng giao thdng va khdng che day nen de bi nhidm bin, vay khdng dam bao vd sinh an toan thuc phdm ddc bidt ddi vdi dgng banh trudc thai Vide phai nang tdn nhieu nhdn cdng va vide tim chd phai rat khd khan qua trinh dd thi hda nhanh dien tlch san phoi bi thu hep Vi vgy, vide lam khd mien dong bdng may sdy la rdt cdn thidt Ngudn nang lupng cung cap cho may sdy rat da dang nhu: ndng lugng didn, ' Vien Ca dien nong nghiap va Cong nghe STH TS Vi^n Ky thuat h6a hoc, Dai hoc Bach khoa HN nang Iugng tir chat ldng, tif khi, tu ngudn ndng lupng sinh khdi (ctii trau, ciii gd, ciii gd, cui cdng nghidp, phe phu phdm nong nghidp ), nang lupng mat trdi Ci nudc ta hien chua sir dung phd bidn thiet bi say mien dong nao Do vay tinh todn nhiet chinh xdc dd dam bao tiet kidm nhien lieu va dap img ydu cdu nhidt lugng cho qua trinh say la viec Idm quan trpng ciia vide thidt ke hd thdng say mien dong d lang nghe II PHlTOfNG PHAP NGHIEN CtTU Phuang phap kd thira: Kd thii'a cac tuu nghien cuu ve thidt kd may say, cac ddc tinh cua qua trinh say ciia cac tdc gia va ngoai nudc Phuong phap tinh toan thiet ke: Tinh toan qua trinh say dua tren thi I-d, mgt sd thdng TAP CHI CONG NGHIEP NONG THON - SO 19 - 2015 25 "57 KHOA HQC - CONG NGH$ sd tdn thdt nhidt dua trdn cac tdi lidu tham khdo Mgt sd kdt cdu d\ra vao thirc td va cdc tu van cua chuydn gia m KET QUA VA THAO LUAN 3.1 So- dh qua trinh thay dhi trying thdi cua tac nhSn say Khdng ngoai trdi tai didra A (hinh 1) cd trgng thdi xdc djnh bdi (To; (po) dugc qugt II hut qua bd trao ddi nhidt I Trong bg trao ddi nhiet, khdng dugc gia nhidt ddn trang thdi d diem B xac dinh bdi cap thdng sd (Tj; cpi) va dugc qugt ddy vdo budng sdy III Trong budng sdy, tac nhan sdy thuc hidn qua trinh say ly thuyet Q day, Tl la nhidt vao budng say dugc quyet dinh bdi tinh chdt vat ly ciia vat lidu sdy va che cdng nghd say Tdc nhdn say khdi budng say d diem C cd trang thai dupc xac dinh bdi (T2; 92), dd T2 dugc chpn trudc theo cdng nghe P-A I— 3.2 Tfnh toan can bang vat chat Tir thuc xi phan tich am ciia nguyen lieu miSn dong dku vao la 65%, va dp Sm san phSm miin dong Uio la 14%, chpn nang su4t diu la 100 leg san phim kho/m^, nhiet siy cho miSn dong la 45°C, thoi gian siy la 2,5 gio/me Trong sufit qu^ trinh say, xem nhu khong c6 hi?n tupng mit m^t vSt chit, do lupng chat kho tuyft d6i coi nhu khong thay doi 3.2.1 Phuang Irinh cdn bdng vdt chdt G, = G2 + (D.t (kg) Trong do: Gl: khoi lupng mign dong dira vao may siy, kg G2: kh6i luong miin dong kho khoi may say, kg (o: Luong im b6c hoi gio, kg/h t: Thai gian siy, h Lupng chit kho tuygt dai dua vao thifa bi say la: „ „ lOO-^j ,„„ 100-14 „^ , G^=G,x i = 100x = 86 kg ' 100 100 ^ 3.2.2 Khoi luang mi&n dong (nguyen lieu) dua vdo thiel bi sdy Voi nang suit siy: 100 kg miin dong kho/me, Hinh Sa dd qud Irinh thay ddi trang Ihdi tdc nhdn sdy lupng nguyen lieu miin dong nguyen lieu cho mpt me siy xac djnh duoc la [1]: Qua trinh say ly thuyet la qua trinh siy dugc G , = G , l ^ = 0 l H £ ^ = 243kg ' ^\-W^ 100-65 thuc hien tren mpt thiSt hi siy ly tuong Vi vay, Trong Wa la dp im miin dong kh6 = 14% ngucri ta xem qua trinh sfy ly tuong la qua trinh dang entanpy (doan B-C), day chinh la dac tnmg Dp im cua mien dcng uot Wi = 65% 3.2.3 Luang dm bay hai gia CO ban ciia qua trinh sdy ly thuydt (hinh 2) G,-G, 243-100 „ , , ^ ffl = —' - = = 57,2 kgam/h I 2,5 3.3 Tfnh toan qua frinh say ly thuyet 3.3.1 Xdc dinh cdc thdng sd khdng moi Irudng (diem A) Moi truimg co ap suit B = 760 mmHg Tren 41-.8iifcl:j d6 thj I-d, trang thai khong moi truomg tai diim A dupc xac djnh bod cap thong s6 (To; (po) Hinh Trang thdi cm tdc nhdn sdy Iren th] I-d qud trinh sdy ly thuyit = (20°C; 85%) Cac thong si Iupng chiia im (do) 26 TAP CHf CONG NGHIEP NONG THON - SO 19 - 2015 KHOA HOC - CONG NGHE va entanpy (Io) co thi tmh theo cac cdng thiirc giai tich hoac xac dinh true tiep tren thi I-d Trong tinh toan du6i ddy, de thuan lpi cho viec dung ngon ngtt lap trinh sau fhi phuong phap giai tich dupc sir dung Vol cong thiic thuc nghiem ctia Antoine[2]: - Ap suat bao hoa cua khdng ling vol To = 20''C: = e x p ^ ! -4026,42 ; ^ ^ ^ f ^ 1^ _=^^e_x fp ^ I 4026,4 - ^ = ^ | ^ } = 0,0233 bar 235,5+ r„ J ™''l 235,5 - Luong chua am cua khong moi trucmg ben ngoai dupc xac dinh theo cong thiic [I]: rf„ = , x - g i i ^ = 0,621x "•85x0,0233 ^ B-^.xn„ M _ 0,85x0,0233 750 - Entanpy cua khong To = 20°C [1]: ^=C^xro+rf.x(r + C^xrJ (kJ/kgkk) kgim/kgkk Trong do: Cpk - nhiet dtmg rieng cia khong kho, kJ/kgkk.K Cpa - nhiet dung rieng ciia hoi nuac, kJ/kg im.K r - nhiet an hoa hoi, kJ/kg im.K Liy Cpk = 1,004 (kJ/kgkk.K)vaCp.= 1,842 (kJ/kg im.K) var = 2500 (kJ/kgim.K) [3],tac6: /„ =I,004x20 + 0,0124x(2500 + l,842x20) = 51,5 kJ/kgkk 3.3.2 Xdc dmh trgng Ihdi khdng sau xac dinh boi cap thong s6 (Ti; di) = (Ti; do) qua Irao ddi nhiel vao budng sdy (diem B) = (45°c* 0124 kg/kgkk) Do qua trinh nhan nhiet ciia khong v *ã i .* ằãô - I L - I I ^, • • ^ , •* Xac dinh duac am khong ipi va bo trao doi nhiet la qua trinh co lupng chiia am ^^^^^ ,_ ^ ^ y^.^^ ^ ^^^ y ^ ^,^ ^^.^^ khong doi uen d,= siy nhu sau: Nhu vdy trang thai khdng d diem B dugc Ap suat bao hoa tuong tiing vdi nhiet dp Tl = 45 C la: f,^ 4026,62 f,^ 4026,62 ^ „.,, , ?., =exp-^12 • ^ = exp-^12 ^ = 0,073 bar " ^[ 235,5 + 7; J *^1 235,5 + 45] Dp am tuong ddi cua tac nhdn say sau khdi trao ddi nhiet: ^ x 0,0124 •S"'' _ 750 _n-,-,o/ ' Pj, X (0,621+ rf,) 0,073 X (0,621+ 0,0124) ' Entanpy cua tac nhan say khoi bp trao doi nhigt: I,=C^>'T,+d,x{r + C^xT,} (kJ/kgkk) /, =I,004x45 + 0,0124x(2500 + l,842x45) = 72,l kJ/kgkk 3.3.3 Xdc dtnh thdng so aia khong kht sau I-d boi cap thong sfl (T2; I2) Do qua trinh siy ly khoi budng sdy (diem C) thuyit la qua trinh dang entanpy nen I2 = li = Trang thai ciia tac nhan siy a diim C sau 72,1 (kJ/kgkk) Nhiet dp ctia tac nhan siy T2 sau qua trinh siy ly thuyet dupc xac dinh tren d6 thi qua trinh siy dupc chpn truoc cho t6n thit TAP CHi CONG NGHIEP NONG THON - SO 19 - 2015 27 KHOA HOC - CONG NGHE nhiet tac nhan siy mang di la be nhat phu Nhu v&y s8 phai xac dinh cac thong so hop voi quy trinh cong nghg va d6ng thoi phai lai cua tac nhan say la: lupng chiia am d2 va dp dam bao khong xay hign tupng dpng suong am tuong d6i 92 Sau tinh dupc 92, tiin hanh Noi each khac nhigt dp T2 duoc chon cho kiim tra lai digu kign lp2= (55 ± 10)%, niu chua tren d6 thi I-d dp im tuong d6i ciia tac nhan say thoa man, phai chpn lai nhigt dp tac nhan say sau khoi buing siy (|)2 nim duai duong cp khoi bu6ng say T2 va tinh lai = 100% Dg dam bao kha nang siy, co thg chpn Vai T2 = 33°C, va I2 = Ii = 72,1 kJ/kgkk thi: T2 theo diiu kien dg 92 = (55 ± 10)%, chon so bp T2 = 33°C Lupng chiia im d2 sau qua trinh siy ly thuyit: rf, = C^xfj 72,1-1,004x33 : 0,0152 kgam/kgkk 2500 + 1,842x33 Ap suit bao hoa tuong ilng nhiet dp T2 = 33°C la: L P., =expi\2 " ^\ 4026,42 f ^ = exp'^12 4026,42] „ „ , , ^ ^ = 0,05 bar 235,5 + r J 235,5 + 33j Dp im tuong dii cua tac nhan say sau khoi buong say: 760-X 0,0152 Bxd, 750 = 0,484 *'' P„x{0,62\ + d,) 0,05 X (0,621+ 0,0152)' Nhu vay (p2 = 48,4% da dam bao thoa man digu kien