Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh1 SVTH: Bi Vn Vnh NHN XT CA GIO VIN HNG DN ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ...............................................................................................................Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh2 SVTH: Bi Vn Vnh NHN XT CA GIO VIN PHN BIN ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh3 SVTH: Bi Vn Vnh CHNG I : TNG QUAN V K THUT SY 1.1 Khi nim qu trnh sy1.1.1 Khi nim1.1.2 Phn loi phng php sy 1.1.3 Mc ch ca qu trnh sy 1.1.4 Nhng bin i c bn ca qu trnh sy 1.1.4.1 Cc dng dch chuyn v th dch chuyn m trong vt keo 1.1.4.2 Cc dng dch chuyn v th dch chuyn m trong vt xp mao dn 1.1.4.3 Cc dng dch chuyn m trong vt keo xp mao dn 1.1.4.4 Dch chuyn m i lu trong vt liu sy1.2 C cht thot m ra khi vt liu sy1.2.1 Qua trnh khuch tn ngoi 1.2.2Qu trnh khuch tn ni 1.2.3 Mi quan h gia qu trnh khuch tn ngoi v qu trnh khuch tn ni 1.3 Cc giai on trong qu trnh sy 1.3.1 Giai on nung nng vt liu1.3.2 Giai on sy ng tc 1.3.3 Giai on sy gim tc Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh4 SVTH: Bi Vn Vnh 1.4 Cc phng php v thit b sy 1.4.1 Cc phng php sy 1.4.2 Thit b sy1.5 Tng quan v sy nhit thp 1.5.1Gii thiu cc phng php sy lanh 1.5.2 Nguyn l lm vic ca h thng sy lnh 1.6 Cc thit b trong h thng sy lnh 1.7Mt s kt qu nghin cu v sy lnh ca cc tc gi trong v ngoi nc 1.7.1 Cc tc gi trong nc 1.7.2 Cc tc gi nc ngoi 1.8 So snh phng php sy lnh vi phng php sy nng nh my 1.9 nh gi v kt lunCHNG II : TM HIU V CNG NGH SY HNH L 2.1 Vt liu sy v tnh l ha ca vt liu sy 2.1.1 S cng ngh sy rau qu2.1.2nh hng ca qu trnh sy n cht lng sn phm 2.3 Cc c tnh ha l ca mt s rau qu giu vitamin ng dng phng php sy lnh2.4L thuyt sy rau qu 2.5 Mt s phng php sy rau qu Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh5 SVTH: Bi Vn Vnh 2.6 La chn phng php sy lnh theo hng nghin cu ca ti CHNG III : KHO ST THC TRNG V LA CHN PHNG PHP SY 3.1 Kho st my sy ti nh my 3.2 Nhim v thit k 3.3 Chn phng n thit k 3.4 Chon tc nhn sy v nng sut sy CHNG IV : TNH TON THIT K M HNH MY SY LNH S DNG BM NHIT 4.1 Gii thiu bi ton thit k v m hnh thit k4.2 Xy dng quy trnh cng ngh sy hnh 4.2.1. Gii thiu vt liu sy 4.2.1. Xy dng quy trnh cng ngh sy Hnh4.3 Xc nh cc thng s u vo ca vt liu 4.4 Tnh ton l thuyt ch sy hi lu hon ton 4.4.1 Xc inh cc im nt trn th sy 4.4.2 Tnh ton tc sy v thi gian sy 4.4.3 Tnh ton nhit qu trnh 4.5 Tnh ton l thuyt ch sy thi b tc nhn 4.5.1. Xc nh cc thng s im nt trn th sy Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh6 SVTH: Bi Vn Vnh 4.5.2. Tnh ton nhit qu trnh 4.6. Xc nh kch thc bung sy 4.7. Cn bng nhit cho qu trnh 4.8. Tnh ton qu trnh sy thc ch hi lu hon ton 4.9. Tnh ton qu trnh sy thc ch thi b tc nhn 4.10. Kt lun v ch sy 4.11. Tnh ton thit k v la chn thit b ph tr 4.11.1. Cc thng s nhit ca mi cht lnh 4.11.2. Tnh ton chu trnh bm nhit 4.11.3. Tnh ton thit k cc thit b trao i nhit 4.11.3.1. Dn ngng 4.11.3.2. Dn bay hi 4.11.4. Tnh chn my nn 4.11.5. Tnh chn ng ng dn mi cht 4.11.5.1. ng ng y 4.11.5.2. ng ng ht 4.11.6. Thit b hi nhit 4.11.7. Tnh ton tr lc v chn qut CHNG V : TRANG B T NG HA H THNG SY V TNH TON GI THNHKhoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh7 SVTH: Bi Vn Vnh 5.1 Trang b in 5.2 Tnh gi thnh sn phm 5.2.1 Chi ph nguyn liu, nhin liu 5.2.2 Chi ph lao ng 5.2.3 Chi ph khu hao 5.3 So snh cht lng v gi thnh hnh l sy nng v sy lnhCHNG VI : KT LUN V NGH 6.1 Kt lun 6.2 ngh TILIU THAM KHO Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh8 SVTH: Bi Vn Vnh Li cm n Hc tp l mt qu trnh lu di, mi giai on ng mt vai tr quan trng trongvichnhthnhnhncch,occamiconngi.Tnhngngy bc chn vo ging ng i hc cho n lc hon thnh lun vn ny, em nhncsquantmchdnvgiptntnhcaccthyc.Quaqu trnh thc hin lun vn tt nghip em xin by t long bit n chn thnh n: -Ban gim hiu trng i hc Nha Trang. -Tp th ging vin Khoa Cng ngh Nhit Lnh trng i hc Nha Trang. -Qu thy c tn tnh ch dy chng ti trong thi gian hc tp ti trng. -c bit, em xin chn thnh cm n Th.s L Nh Chnh trc tip theo di, tn tnh hng dn em trong thi gian thc hin ti. Tuy nhin, do hn ch v thi gian thc hin, ti khng trnh khi nhng thiu st. Mong nhn c s ch bo ca qu thy c v gp ca cc bn. Nha Trang, thng 3, nm 2012 Sinh vin thc hin ti Bi Vn Vnh Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh9 SVTH: Bi Vn Vnh TRNG I HC NHA TRANG CNG HA X HI CH NGHA VIT NAM Khoa Cng Ngh Nhit Lnhc Lp- T Do- Hnh Phc NHIM V N TT NGHIP H v tn: MSSV: Ngnh: Cng Ngh Nhit LnhNin Kha: 2008-2012 Tn ti: Kho st v tnh thit k my sy bm nhit tng si sy hnh ut khu nng sut kgm. I Thng tin thc hin ti: 1-S liu choo trc: M hnh sy lnh ca khoa Cng Ngh Nhit Lnh TrngiHcNhaTrangvkhostthcththngsynngti Cng Ty thy sn Bc liu ( KCN. Sui Du ) II Ni dung ti: 1-Tmhiucngnghsylnh,phngphpsy,ccthitbtrongh thng sy lnh. 2- Tm hiu k thut sy lnh trn mt s thc phm v rau qu trong nc v th gii. 3-Trnhbyccktqunghincuvsylnhtrongncvthgiit trc n nay. 4- La chn vt liu sy lnh, xy dng quy trnh cng ngh v x l vt liu trc sy v sau sy lnh. 5- L thuyt v sy rau qu v thc phm. 6- Tnh ton thit k m hnh my sy lnh s dng bm nhit. 6.1 Gii quyt bi ton sy lnh l thuyt v sy thc theo ch thi b tc nhn. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh10 SVTH: Bi Vn Vnh 6.2 Gii quyt bi ton sy lnh l thuyt v sy thc theo ch hi lu hon ton kh thi. 7- Tnh ton thit k v la chn cc thit b ph tr cho h thng sy. 8- Kho nghimm hnh my sylnh xc nh li cc thng s k thut ca m hnh. 9-Xcnhmt syutchnhnh hng ncht lng snphmsy lnh hai ch sy 10- So snh cht lng ca sy lnh v sy nng ti nh my 11- Kt lun rt ra t thc nghim. 12- Hiu qu kinh t Xy dng gi thnh 1kg rau sy 13- Cc bn v thit k III/ Ngy giao nhim v: 01/03/2012 IV/ Ngy hon thnh nhim v: 15/06/201 Nha Trang, thng 3 nm 2012 Gio vin hng dn THS. L Nh Chnh Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh11 SVTH: Bi Vn Vnh Li m u Vit Nam l mt nc nhit i c nhiu iu kin pht trin ngnh trng trt v ch bin rau qu. Tuy nhin, t l tn tht sau thu hoch l rt ln 25-30% [20]. Nguyn nhn chnh l do cng ngh ch bin v bo qun ca chng ta cn lchunnlmchorauqucaVitNamcgitrthptrongthtrng trongnccngnhxutkhu,iunynhhngtrctipnisngca ngi nng dn, v vy vic nghin cu a ra cc quy trnh cng ngh cng nh ng dng trin khai chuyn giao cc kt qu nghin cu, cc quy trnh cng ngh bo qun, ch bin rau qu, ng vai tr ht sc quan trng trong chin lc pht trin ngnh rau qu. Rauquhinnaychyucsdngdngti,nhbitrauqul loi sn phm c tnh thi v, thi gian thu hoch ngn, kh nng vn chuyn v bo qun hn ch, trong khi k thut bo qun rau qu ti vn ch da vo cc kinhnghinctruyn,mangtnhthcngchpv.Cngnghsyngdng trong ch bin rau qu kh c tin hnh t kh lu nhng cho n nay vn bc lnhiuhnchvcngnghchakhcphccchtlnguracasn phm, cha p ng c cc yu cu v c tnh ha l, mi, mu, thnh phn dinhdngnnkhpngchonhucutiuthvxutkhutrongvngoi nc. Vic u t nghin cu mt quy trnh cng ngh mi gii quyt nhng vn ny l thc s cn thit. Cng ngh sy lnh c xem l mt cng ngh mi, ra i t yu cu cp thit . u im ca cng ngh sy lnh l c th xy dng c tng quy trnh cng nghsyhplivitngloirau,c,qu.Snphmsygicnguyn mu sc, mi v, hn ch ti a tht thot dinh dng (khong 5%)[20], t tiu chunvsinhantonthcphmcaVitNamvccchtiukthut,cht lng sn phm tng ng mt s nc khc trn th gii.Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh12 SVTH: Bi Vn Vnh Vic pht trin cng ngh sy lnh c nhiu thnh tu. Tuy nhin, c mt quytrnhcngnghhonchnh,tiuviccthngsphhpnhtihi chngtaphitinhnhnghincusurnghn.csphncngti Kho st v tnh thit k my sy bm nhit tng si sy hnh l xut khu nng sut 100kg/mthc hindatrncs tmhiunhng nguyn lchung nht ca cng ngh sy lnh t c th xy dng nn quy trnh sy i vi tng loi rau qu khc nhau. gii quyt nhng vn , ti nghin cu nhng ni dung chnh sau: Tm hiu v cng ngh sy lnh, phng php sy v cc thit b trong h thng sy lnh. Tmhiukthutsylnhtrnmtsloirauqugiuvitamin,xy dng quy trnh sy lnh i vi Hnh l ct nh. Tnh ton thit k m hnh my sy lnh s dng bm nhit ch sy hi lu hon ton v ch thi b tc nhn. Tnh ton thit k my sy lnh v la chn cc thit b ph tr. Thc nghim nghin cu trn m hnh thc t. So snh hiu qu ca h thng sy lnh vi sy nng nh my. Vi nhng c tnh u vit, cng ngh sy lnh ha hn s l mt cng ngh tintin,cholnhvcsythcphmgiuvitamin,cthpdngrngrivi quy m ln p ng c v vn li ch kinh t v bo v mi trng. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh13 SVTH: Bi Vn Vnh CHNG I TNG QUAN V K THUT SY 1.1 Khi nim qu trnh sy 1.1.1 Khi nim Sylqutrnhtchm(hincvnc)rakhiVLS,trongVLSnhn nng lng m t trong lng VLS dch chuyn ra b mt v i vo mi trngtcnhnsy(TNS).Qutrnhsylqutrnhtruynnhit,truyncht xyrangthi.TronglngVLSlqutrnhdnnhitvkhuchtnmhn hp. Trao i nhit - m gia b mt VLS vi TNSl qu trnh trao i nhit v traoi milu lin hp.Qu trnhbntrongVLSchyuchunh hng cadnglinktmvictkhcavtliu,qutrnhbmtVLSchyu chu nh hng ca c cu trao i nhit m v cc thng s ca TNS cng nh VLS.1.1.2 Phn loi phng php syNgi ta phn bit 2 phng php sy :-Sy t nhin : Sy bng khng kh khng dc t nng, phng php ny thi gian sy di, kh iu chnh qu trnh v m cui ca vt liu cn kh ln nht l nhng quc gia c kh hu nhit i nh nc ta. -Sy nhn to : L qu trnh sy c s cp nhit t bn ngoi, ngha l phi dng n tc nhn sy c gia nhit nh khi nng, khng kh nng hoc hi Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh14 SVTH: Bi Vn Vnh 1.1.3 Mc ch ca qu trnh sySy khng ch l qu trnh cng ngh, trong cc tnh cht cng ngh lun lun thay i. Tnh cht cng ngh ca vt liu gm: tnh cht ho l, tnh cht c kt cu, tnh cht sinh ho. Qutrnhsynhmtngcngmtsctnhcngnghphcv nhiu mc ch khc nhau. Khi sy sn phm gm th nhm mc ch lm bn ca n tng ln tip tc gia cng; sy ht ging th phi lm t l v kh nng nymmcaoln;synngsnthcphmthgichngv,musc, nguyntvilngmtngcthigianboqun,gimcgithnhvn chuyn, gim c th tch kho bo qun. 1.1.4 Nhng bin i c bn ca qu trnh sy nghin cu v cng ngh sy, trc ht cn nghin cu v cc dng lin kt m, cc dng dch chuyn m v th dch chuyn m trong VLS nhm hiu r c ch dch chuyn m v nh hng phng php tc ng tng cng hoc hn ch dng dch chuyn m phc v cc yu cu cng ngh. Theo dng lin kt m vi ct kh ca vt, VLS chia thnh 3 nhm :vt keo, vt xp mao dn v vt keo xp mao dn. 1.1.4.1 Cc dng dch chuyn v th dch chuyn trong vt keo Lin kt m trong vt keo l lc hp th v lc khuch tn thm thu. Do , mt dng m lng j2k t l thun vi gradient p sut thm thu ttp V . Vi cha m thng thng ca vt trng n gii hn, p sut thm thu ( trng n ) l hm ca cha m M. Do ta c :( ) M a M M / p D p D j0 k 2 tt 2 p tt 2 p k 2V = V c c = V = (1.1) Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh15 SVTH: Bi Vn Vnh Vt keo l vt c cu trc mao mch phn t qu trnh khng ng nhit dch chuyn m lng dng mng c dng : gradient t k M k j0tm 2 o m 2 m 2V + V = (1.2) Dng m lng dch chuyn s bng :( ) t k M k a j j j0tm 2 o m 2 k 2 m 2 k 2 2V + V + = + = (1.3) Dch chuyn m dng hi c xc nh gn ng bi qu trnh khuch tn phn t. Mt dng phn t j1 t l nghc vi gradient ca( ) T / p1. Vi p1 l p sut ca hi m. Trong qu trnh on nhit p1 l hm ca cha m v nhit nn dng j1 s bng :t a M a j0tct 1 0 ct 1 1V V = (1.4) Dng dch chuyn m tng ( lng v hi ) xc nh theoM Vvt Vtrong vt keo s bng :t a M a j j j0tmk 0 mk 2 1V V = + = (1.5) Trong :m 2 k 2 ct 1 mkk a a a + + = (1.6) tm 2tct 1tmkk a a + = (1.7) 1.1.4.2 Cc dng dch chuyn v th dch chuyn m trong vt xp mao dn Dch chuyn lng mao dn (Khuch tn mao dn) trong vt xp mao dn, c cc mch ln (r > 10-5), gn lin vi lin kt c l. Trong vt xp cu trc a mao mch , dng m lng t l thun vi gradient th mao dn: Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh16 SVTH: Bi Vn Vnh V =k jmd 2

(1.8) Th mao dn trong trng hp ng nhit t l thun vi cha m M. Trong iu kin khng ng nhit, dng m lng khch tn mao dn j2md c xc nh : t a M a k j0tmd 2 0 md 2 md 2V V = V = (1.9) a2md v tmd 2al h s khch tn lng mao dn v h s khch tn nhit ca lng mao dn. Ga tr ca chng ph thuc vo sc cng b mt, gc dnh t, nht ca lng , bn knh mao dn. Khi m ca vt vt gi tr ht m cc i th trong cc mao mch ln ca vt xp cha y nc , dch chuyn lng lc ny l do chnh lch th mao dn. Khc vi trng hp thm lng mao dn xy ra do vt tip xc trc tip vi cht lng (do p sut thy tnh), th mao dn l khng ng nht, lng lng c ht vo c gii hn v lng khng th in y ton b vt do b hn ch bi phn ct kh ca vt. Th mao dn vi phn t mao mch bng :||.|

\|o= 2 1 2r1r1 2 (1.10) Nh vy iu kin c th dch chuyn lng mao dn, gn vi s bay hi v ngng t lng, l s khc bit bn knh ca mao mch, r1= r2. Vi s tn ti ca qu trnh bay hi, dch chuyn hi m trong cc mao mch ln (r > 10-5),c xc nh theo quy lut khch tn phn t. Cn vi cc mao mch nh qu trnh ny xy ra theo quy lut chy trn. Ngoi ra, vi qu Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh17 SVTH: Bi Vn Vnh trnh bay hi lng trong vt xp, cn tn ti dch chuyn m i lu v m c gi l khch tn trt (hay l khch tn thy ng). Khi dng hi tng ng vi p sut tng p=const s gm dng khch tn phn t j1pt, dng khch tn i lu j1dl = k 1v . v dng chy trn j1ct. p sut bay hi p1 l hm ca cha m v nhit , p1=f(M,t). Vy nn, dng dch chuyn m c th th hin bng quan h :t a M a j j j j0tmd 1 0 md 1 ct 1 dl 1 pt 1 1V V = + + =(1.11) Vy dng m tng dch chuyn trong xp mao dn l :t a M a j j j0tMmd 0 Mmd 2 1V V = + =(1.12) Trong : Mmda v tMmda l h s khch tn m v h s khch tn nhit ca m mao dn, vi :

md 2 md 1 Mmda a a + = (1.13)

tmd 2tmd 1tMmda a a + = (1.14) Ngoi ra, cn c dch chuyn m lng v hi do lc thm mao dn (c nghin cu trong l thuyt thm). Gi thit dng thm lng v hi c lp nhau, c th vit :iiii i ip) ( kv j Ve = =i=1,2 (1.15) 1.1.4.3 Cc dng dch chuyn m trong vt keo xp mao dn Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh18 SVTH: Bi Vn Vnh Qa trnh dch chuyn m trong vt keo xp mao dn c xc nh bng cc hin tng dch chuyn khc nhau v c phn tch trong vt keo v vt mao dn trn. Nu b qua nh hng ca lc trng trng th s chuyn m trong VLS do cc lc nhit ng khc nhau v cc lc nhit ng ny u l hm ca cha m M v nhit t, do chng c th biu din quat , M V V . Dch chuyn m qua vt keo xp mao dn c xc nh bng cng thc :) t M ( a t a M a j0 M 0tM 0 MV o + V = V V = (1.16) Trong : Ma v tMa l h s khch tn v h s khch tn nhit ca m,o l h s khch tn nhit tng i, tM Ma / a = o . mk Mmdmk k Mmd mdtmktMmdtMmk Mmd Ma aa aa a aa a a+ o + o= o+ =+ = (1.17) Cc h s khch tn m aM vo l hm ca cha m v nhit . c trng cho s thay i ca h s aM vi cha m khc nhau c xc nh theo dng lin kt m v dng dch chuyn m (lng v hi). Vi vt xp mao dn in hnh , h s aM tng khi cha m tng, v vi cha m ln thi h s aM khng i. Nu qu trnh l dch chuyn m lng th h s aM s tng hoc khng i ph thuc vo ng cong phn b hang xp theo ng knh. H s aM ca cc vt liu c xc nh bng thc nghim di dng bng s hoc cng thc. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh19 SVTH: Bi Vn Vnh 1.1.4.4 Dch chuyn m i lu trong vt liu syTrong qu trnh sy cng cao, nu nhit ca vt liu sy ln hn 100OC th phn p sut hi nc bo ha p1 s ln hn p sut khng kh ca TNS. Khi , dng dch chuyn m do khch tn trong vt xp c thay th bi dng dch chuyn m i lu. Gradientp sut tng) p (Vxut hin khi nhit ca vt liu sy ln hn 100OC, tuy nhin nu qu trnh c thc hin bng vic t nng bn trong(v d sy cao tn) th) p (Vxut hin ngay c khi nhit b hn 100OCS tn ti ca) p (Vgy nn dng dch chuyn m i lu ca hn hp kh hi trong mi trng xp , nn khi tnh dng nhit dch chuyn m ( lng, hi ) tng qut cn b sung dng dch chuyn ny. Mt dng hi dch chuyn bi dng ny l :p k p k v jp 10 1 1V = V = = (1.18) Vi = /1 10l nng tng i ca hi nc , kp l h s dng nng phn t[17] :) d 1 /( kd k k10 p+ = =(1.19) Vi d l dung m ca khng kh. Dng m tn ti gradient p sut tng bng :p k t a M a jp 0tM 0 MV V V = (1.20) Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh20 SVTH: Bi Vn Vnh Biu thc (1.20) cha k n dch chuyn lng di tc dng ca lc trong trng v gradient p sut thy tnh ( dng lng qua mi trng xp ). Cng ca dng dch chuyn m thm i lu ln hn nhiu ln dng dch chuyn m di tc ng ca lc mao dn v khch tn. Qa trnh ny thng c nghin cu c lp vi qu trnh dch chuyn m trong VLS. 1.2 C cht thot m ra khi vt liu syMun lm kh phi t nguyn liu trong mi trng khng kh m, nc dch chuyn vo mi trng khng kh, c s chnh lch vt cht ( th vt cht ). Hot ca nc trong nguyn liu phi m bo di hot ng ca vi sinh vt hot ng. Khi lm kh xy ra qu trnh nc tch ra khi vt liu : nc t b mt nguyn liu dch chuyn vo mi trng kh. y l iu kin kin quyt qu trnh lm kh xy ra. Ngoi ra lm kh phi c qu trnh dch chuyn m t cc lp pha trong i ra cc lp b mt. s dch chuyn m t trong ra ngoi hnh thnh khi m v nc t trung tm nguyn liu dch chuyn ra b mt v lp xung quanh m bo m lp trung tm bng cc lp xung quanh. Qu trnh thot m ra khi vt liu trong qu trnh sy c chia lm 2 giai on : 1.2.1 Qua trnh khuch tn ngoi L qu trnh dch chuyn m t lp b mt ca vt liu sy vo mi trng khng kh xung quanh. ng lc ca qu trnh ny l do chnh lch p sut hi trn b mt ca vt m v p sut ring phn hi nc trong mi trng khng kh. Lng nc bay hi : Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh21 SVTH: Bi Vn Vnh (

)Hoc (

) (1.21) Trong :Ps : p sut ring phn hi nc trn b mt Ph : p sut ring phn khng kh k : H s bay hi F : Din tch b mt bay hi

: Gradient m Lng bay hi trn mt n v din tch t l thun vi gradient chnh lch m gia nguyn liu v mi trng xung quanh. S chnh lch xy ra : nc t b mt dch chuyn vo mi trng xung quanh lm m lp khng kh tng ln, ng thi lm lng m trn b mt VLS gim i. Gradient m gim , qu trnh bay hi chm li. Nu m b mt cn bng vi mi trng khng kh th qu trnh ngng bay hi, nhng m ca hai lp khng kh k tip chnh lch nn hm m ca khng kh th nht khch tn sang lp th hai v m t trong VLS khch tn sang lp khng kh th nht. Gradient m ph thuc vo tnh cht ca mi trng lm kh : nhit , p sut , s lun chuyn ca khng kh v ph thuc vo b mt nguyn liu : nhn, hnh dng, kch thc b mt. 1.2.2 Qu trnh khuch tn ni Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh22 SVTH: Bi Vn Vnh L qu trnh dch chuyn m t lp bn trong ra lp b mt ca vt m. ng lc ca qu trnh ny l do chnh lch nng m gia cc lp bn trong v cc lp b mt, ngoi ra qu trnh khch tn ni cn xy ra do chnh lch nhit gia cc lp bn trong v cc lp b mt. (

) (1.22) Trong :D : H s khch tn ni F : Din tch khch tn

: Gradient m H s khch tn ni (D) ph thuc ch yu v thnh phn, tnh cht nguyn liu, gin tip ph thuc vo yu t mi trng. Qua nghin cu ta thy rng m dch chuyn t ni c nhit cao n ni c nhit thp. V vy, ty theo phng php sy v thit b sy m dng m dch chuyn di tc dng ca nng m v dng m dch chuyn di tc dng ca nhit c th cng chiu hoc ngc chiu vi nhau. Nu hai dng m dch chuyn cng chiu vi nhau s lm thc y qu trnh thot m , rt ngn thi gian sy. Nu 2 dng m dch chuyn ngc chiu nhau s km hm s thot m, ko di thi gian sy. 1.2.3 Mi quan h gia qu trnh khuch tn ngoi v qu trnh khuch tn ni Khch tn ni v khch tn ngoi c mi quan h cht ch vi nhau, qu trnh khch tn ngoi l qu trnh khi u v quyt nh n giai on u ca qu trnh sy v qu trnh khch tn ni l ng lc ca qu trnh khch tn ngoi. Tc l qu trnh khch tn ngoi c tin hnh th qu trnh khch tn ni mi Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh23 SVTH: Bi Vn Vnh c tip tc v nh th m ca nguyn liu mi c gim dn. Tuy nhin trong qu trnh sy ta phi lm cho 2 qu trnh ny cn bng vi nhau, trnh trng hp khch tn ngoi ln hn qu trnh khch tn ni. V khi s lm cho s bay hi trn b mt xy ra mnh lit lm cho kh b mt, hn ch s thot m, khi xy ra hin tng phi khc phc bng cch m ( sy gin on ) mc ch l thc y qu trnh khch tn ni. 1.3 Cc giai on trong qu trnh sy c im ca qu trnh sy i vi vt th c m tng i cao, nhit sy v tc chuyn ng ca khng kh khng qu ln xy ra theo ba giai on l giai on lm nng vt, giai on sy tc khng i, giai on tc sy gim dn. i vi cc trng hp sy vi iu kin khc th qu trnh sy cng xy ra ba giai on nhng cc giai on c th an xen kh phn bit hn. 1.3.1 Giai on nung nng vt liuGiai on ny bt u t khi a vt vo bung sy tip xc vi khng kh nng cho ti khi nhit vt t c bng nhit k c. Trong qu trnh sy ny ton b vt c gia nhit. m lng trong vt c gia nhit cho n khi t cnhitsingviphnpsuthinctrongmitrngkhngkh trong bung sy. Do c lm nng nn m ca vt c gim cht t do bay hi m cn nhit ca vt th tng dn cho n khi bng nhit k c. Tuy vy, s tng nhit trong qu trnh xy ra khng u phn ngoi v phn trong vt. Vngtrongvttnnhitkcchmhn.ivivtdsythgiai on lm nng vt xy ra nhanh. 1.3.2 Giai on sy ng tc Ktthcgiaiongianhit,nhitvtbngnhitkc.Tiptc cung cp nhit, m trong vt s ha hi cn nhit ca vt gi khng i nn Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh24 SVTH: Bi Vn Vnh nhit cung cp ch lm ha hi nc. m s ha hi lp vt liu st b mt vt, m lng bn trong vt s truyn ra ngoi b mt vt ha hi. Do nhit khng kh nng khng i, nhit vt cng khng i nn chnh lch nhit giavtvmitrngcngkhngi.iunylmchotcgimca cha m vt theo thi gian cng khng i, c ngha l tc sy khng i. Trong giai on ny bin thin ca cha m theo thi gian l tuyn tnh. m c thot ra trong giai on ny l m t do. Khi m ca vt t n tr stihnUk=Ucbmaxthgiaionsytckhngichmdt.ngthi cng l chm dt giai on thot m t do chuyn sang giai on sy tc gim. 1.3.3 Giai on sy gim tc Ktthcgiaionsytckhngimtdobayhiht,cnli trong vt l m lin kt. Nng lng bay hi m lin kt ln hn m t do v cng tng ln khi m ca vt cng nh. Do vy tc bay hi m trong giai on ny nh hn giai on sy tc khng i c ngha l tc sy trong giai onnynhhnvcnggimitheothigiansy.Qutrnhsycngtip din, m ca vt cng gim, tc sy cng gim cho n khi m ca vt gimnbngmcnbngviiukinmitrngkhngkhmtrong bungsythqutrnhthotmcavtngngli,cnghatcsybng khng. 1.4 Cc phng php v thit b sy Sy c th c chia ra hai loi: sy t nhin v sy nhn to.- Sy t nhin: qu trnh phi vt liu ngoi tri, khng c s dng thit b.-Synhnto:ccphngphpsynhntothchintrongccthitb sy.Cnhiuphngphpsynhntokhcnhau.Cncvophngphp Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh25 SVTH: Bi Vn Vnh cung cp nhit c th chiara cc loi: sy i lu, sy bc x, sy tip xc, sy thng hoa, sy bng in trng dng cao tn, sy in tr 1.4.1 Cc phng php sy 1.4.1.1 Phi v sy bng nng lng mt tri Sy bng cch phi nng (khng c s dng thit b sy) c s dng rng ri nht trong ch bin nng sn Trong cc phng php phc tp hn (sy bng nng lng mt tri), nng lng mt tri c thu nhn gia nhit tc nhn sy hoc s dng nng lng mt tri sy trc tip. 1.4.1.2 Sy i lu Nguyn l hot ng :Khngkhnnghockhilcdnglmtcnhnsycnhit, m, tc ph hp, chuyn ng chy trm ln vt sy lm cho m trong vt sy bay hi ri i theo tc nhn sy. Khngkhcthchuynngcngchiu,ngcchiuhocctngang dngchuynngcasnphm.Syilucththchintheom(gin on) hay lin tc. Trn hnh v di l s nguyn l sy i lu bng khng kh nng. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh26 SVTH: Bi Vn Vnh 1 Qut; 2 Caloriphe; 3 Bung sy Hnh 1.1: S h thng sy i lu. Sn phm sy c th ly ra khi bung sy theo m hoc lin tc tng ng vinpvo.Caloriphe2tnngkhngkhcthlloicaloriphein, caloriphe hi nc v.v... Kt cu thc ca h thng rt a dng, ph thuc vo nhiu yu t nh : ch lmvic,dngvtsy,psut lmvic,cch nungnng khng kh,chuyn ng ca tc nhn sy, s lm vic, cu trc bung sy... i vi qu trnh sy chi ph nng lng l yu t chnh nh hng n hiu qu kinh t sn xut, v vy khi thit k, cn ch n cc bin php lm gim s tht thot nhit, tit kim nng lng.V d : - Cch nhit bung sy v h thng ng dn. - Tun hon kh thi qua bung sy - S dng thit b trao i nhit thu hi nhit t khng kh thot ra un nng khng kh hoc nguyn liu vo. - S dng nhit trc tip t la t kh t nhin v t cc l t c c cu lm gim nng kh oxit nit. -Sythnhnhiugiaion(vd:kthpsytngsivisythng hoc sy phun kt hp vi sy tng si). - C c trc nguyn liu lng n nng cht rn cao nht c th. 1.4.2 Thit b sy1.4.2.1 My sy thng quay - Cu to: Gm thng hnh tr 1 t dc khong 6 8 so vi mt phng nmngang.C2vnhaitrttrnccconlnta4khithngquay.Khong cch gia cc con ln c th iu chnh c, thay i gc nghing ca thng. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh27 SVTH: Bi Vn Vnh Thngquaycnhlpchttrnthnthng,bnhrng2nkhpvibnh rng 3 ni vi mt thng qua hp gim tc. Thng quay vi vn tc khong t 18 vng/pht. Bnh rng t ti trng tm ca thng. Mysythngquaylmvicpsutkhquyn.Tcnhnsycthl khngkhhaykhil.Thngthvtliusyhaytcnhnsychuynng cngchiutrnhsyqukhvtcnhnsykhimangtheovtliusy nhiunhsyngcchiu.Vntccakhngkhhaykhilitrongthng khong 23 m/s. Vt liu ut qua phu 10 ri vo thng u cao v c chuyn ng trong thng nh nhng m chn 11. m chn va phn b u vt liu theo tit din thng,vaxotrnvtliu,valmchovtliutipxcvitcnhnsytt hn.Vtliusysaukhisykhc araca6nhvt ti7 arangoi. Cn khi l hay khng kh thi ra c cho qua xyclon 8 gi li nhng ht vt liu b ko theo ri thi ra ngoi tri qua ng khi. trnh cc kh thi chui qua cckhehcamysy,lmnhhngnsckhocngnhn,ngitat qut ht 5 b sung cho sc ht ca ng khi v to p sut m trong my sy. Mysythngquaycsdngrngritrongcngnghiphocht,thc phm sy mt s ho cht, qung Pi-rt, phn m, ng cc ng - u im: +Qatrnhsyunvmnhlit,tipxcgiavtliusyvtc nhn sy tt. + Cng lm vic tnh theo lng m kh cao, c th ti 100 (kg/m3h) + Thit b cu to gn, chim mt bng nh. - Nhc im: Vt liu d b v vn.- Ch : + Nu sy bng khi l th dn khi l vo my bng ca 9. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh28 SVTH: Bi Vn Vnh + ng knh thng quay thng c qui chun ( D = 1,2; 1,4; 1,6m t l gia chiu di v ng knh thng khong : 3,57) Hnh 1.2 : My sy thng quay 1.4.2.2 Thit b sy kiu phun bi (sy phun) a. Loi thp:- Cu to: Gm c thp cao 5, nh thp c vi phun 3 c nh hoc quay. Dungdchchab1cnhitthchhpnhbm2bmlnnhthpv phun qua vi thnh sng m. - Sn phm ly ra y thp gin on hay lin tc. - Thp c th cao n 60m. Hnh 1.3: Thit b sy phun kiu thp. b. Loi thng: em chanKhoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh29 SVTH: Bi Vn Vnh - Cu to: Gm mt thng hnh tr 1 c y nn. Np trn c t mt 2 ni vi u vi phun 3 c tc quay rt ln 2000 6000 vng/pht. Caloriphe si 4 t nng khng kh. Sn phm thu hi xyclon 5, cn khng kh thi ra ngoi nh qut 6. Hnh 1.4: Thit b sy phun kiu thng. c. C ch ca qu trnh, cc phng php phun bi v ng dng: -Cch:Vicphunchtlngthnhbimtrongphngsyvqutrnh tin hnh rt nhanh n mc cha kp t nng vt liu ln qu thi hn cho php thvtliukh.Snphmthucdngbtmnnnsaukhngcn nghin tn na. Cng sy tng t l thun vi s tng ca b mt tip xc gia VLS v TNS; tc l ph thuc vo phn tn ca cht lng thnh bi. Cc phng php phun bi: +Lytm:Chochtlngivomtdaquaynhanhkhong2000 6000 v/pht, c th phun huyn ph v cht lng nht thnh bi. + C kh: Nh vi phun, trong cht lng c y bng bm vi p lc 200 at. - phun u v to tia nh, cc vi phun c c nhiu l nh vi ng knh 0,5 mm. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh30 SVTH: Bi Vn Vnh -Loinykhngthuntinividungdchhuynphvccdungdch nht. + Dng kh nn: Nh cc vi phun trong cht lng c y bng khng kh nn vi p sut 2,5 6 at. -Ch:Trong 3loitrn, thngdng loi lytmvnc hiu qucao nht nhng c nhc im l tiu hao nng lng nhiu nht. - ng dng: My sy phun c dng sy cc dung dch nh : bt c ph, ca cao, sa b, 1.4.2.3 Thit b sy tng si - Cu to: Hnh 1.5: Thit b sy tng si. - Nguyn tc lm vic: Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh31 SVTH: Bi Vn Vnh Qut1akhngkhvotrnvikhil(haykhngkh+khil) phng 2 ri vo bn di phng sy 3, qua li phn phi 4 ri tin hnh sy vt liu. Vtliucho vophu v nh vt ti 5 avo pha trn bung sy.y chnggphnhpkhnngitdilnvtothnhtngsi.Vtliukh c thi qua tm chn 6 sang thng cha 7 ri ra ngoi. Cn nhng ht nh b dng kh cun theo s c thu hi bi xyclon 8. Tc nhn sy c th l khng kh, khi l hoc khng kh + khi l. - u nhc im: + u im: Cng sy mnh lit, cho php sy nhit cao hn nhit cho php v thi gian tip xc ngn. Hiu qu s dng nhit cao, c kh nng iu khin t ng. Loi ny ang c s dng rng ri. + Nhc im: Khng sy c vt liu c m qu ln, cc to, d v. + Tr lc thu lc ln, thit b mau hao mn. 1.4.2.4Mt s thit b sy khc a. Thit b sy bng bng ti: Gmmtphnghnhchnht,trongcmtvibngtichuynng chm nh cc tay quay. Cc bng ny ta trn cc con ln khi b vng xung, bngnylmbngsibngtmcaosu,bngkimloihaylikimloiv chuyn ng vi tc khong 0,3 0.6 m/pht. Loi thit b ny c th dng sy rau qu, ng cc, than - Cu to: Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh32 SVTH: Bi Vn Vnh Hnh 1.6: Thit b sy bng bng ti. b. Thit b sy bng kh thi. Hnh 1.7: Thit b sy bng kh thi. -Dng sy vt liu dng ht nh hay tinh th. -Vt liu vo my v c dng kh c tc 10 20 (m/s) cun theo ln ngthngngdit1020(m/s).sauvophnggimtcri vo xyclon thu hi sn phm. -Thi gian sy rt ngn t 5 7 (s). Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh33 SVTH: Bi Vn Vnh -uim:Bmttipxckhln,nnqutrnhsyrtmnhlit,thi gian sy nhanh nn cho php sy nhit cao. Thit b cu to gn, n gin. -Nhc im: Kh iu chnh qu trnh, tn nhiu nng lng. c. Sy bng tia bc x. Hnh 1.8: Thit b sy bng tia bc x. - Nnglngbcxtiahngngoiphtracthtruynchovtliumt lng nhit ln v t c tc bay hi m cao hn so vi sy i lu v tip xc. - Sy bc x thng dng sy b mt sn trong cng nghip ch to my, sy hng dt, giy cht do, cc sn phm g, thc phm d. Sy trc. - C th gm mt hay hai trc. My sy c cng sy cao (c th 60 70 kg/m2h). - Sy c cc vt liu nho, km bn vng nhit cao. Tit kim c nhin liu v t mt nhit. Nhc im l m cui ca sn phm kh cao. e. My sy chn khng. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh34 SVTH: Bi Vn Vnh My sy lm vic chn khng c u im so vi my sy lm vic p sut kh quyn l: sy c vt liu khng chu c nhit cao hay d b oxy ho, vt liu d b bi hay vt liu thot ra dung mi qu cn thu hi v vt liu d n. f.My sy thng hoa: Ngitasyvtliutrngthingbngtrongmitrngchnkhng cao 0,1 1 (mmHg). Mc ch l to s chnh lch nhit gia vt liu sy v ngun nhit bn ngoi. Ngi ta dng bm chn khng ht hi m v to chn khng. u im ca loi my sy ny l sn phm thu c c cht lng cao. Vt liu sy khng b bin cht, bo v vitamin nh lc ti. g. Thit b sy kiu thng ng: Hnh 1.9: Thit b sy kiu thng ng. - Gmmt thng hnh tr t c nh, bn trong c mt trc gn nhiu da quay v khong cch gia cc da bng nhau. S lng da v tc quay ca da ph thuc vo vo tnh cht ca vt liu v yu cu k thut. Trn thnh thng c gn nhng phu hng vt liu. Qu trnh sy ngc chiu. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh35 SVTH: Bi Vn Vnh - Khngkhcqutchnhaquacaloriphesirivothngsyt di ln. Vt liu sy vo ca trn, ri xung da. Do da quay, vt liu vng ra thnh thng ri li xung da di nh phu hng liu. C nh th, vt liu sy v tc nhn sy s tip xc vi nhau khi ra khi my sy,vt liu kh t yu cu. Tc nhn sy c qut ht ph a sang xyclon thu hi sn phm dng bi nh. thu hi trit sn phm, ngi ta cho dng kh nng i vo thit b thu hi t trc khi ra ngoi. - Vic b tr hai qut l cn thit m bo cho tc nhn sy thng c tr lc v lu thng trong ton h thng. - Thit b sy kiu thng ng tn t nng lng hn my sy thng quay v t chim mt bng hn. - Nhc im l vt liu d b v vn nhiu. 1.5 Tng quan v sy nhit thp 1.5.1 Gii thiu cc phng php sy lanh1.5.1.1 Lch s hnh thnh v pht trin ca bm nhit Bm nhit c qu trnh pht trin lu di, bt u t khi Nicholas Carnot xutnhngkhinimutin.Mtdngnhitthngthngdichuyntmt vngnngnmtvnglnh,Carnotaralplunrngmtthitbcth csdngongcqutrnhlbmnhit.unhngnm1850, LordKelvin pht trincclthuytvbmnhitbnglp lun,cc thitb lmlnhcthcsdnggianhit.Snphmbmnhitutinc bn vo nm 1952. T khi xy ra cuc khng hong nng lng vo u thp k 70, bm nhit li bc vo mt bc tin nhy vt mi. Hng lot bm nhit mi kch c cho cc ng dng khc nhau c nghin cu ch to, hon thin v bn rng ri trn th trng. Ngy nay, bm nhit trnn rt quen thuc trong cc lnh vc iu ha khng kh, sy, ht m, un nc Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh36 SVTH: Bi Vn Vnh Hnh 1.10 S nguyn l h thng bm nhit1.5.1.2 Gii thiu cc phng php sy lnh Trong phng php sy lnh, ngi ta ra chnh phn p sut hi nc gia vt liu sy v tc nhn sy bng cch gim phn p sut trong tc nhn sy nhgimlngcham.phngphpsylnh,nhitbmtngoinh hn nhit bn trong vt, ng thi do tip xc vi khng kh c m v phn p sut hi nc nh nn lp b mt cng c phn p sut hi nc nh hn pha bntrongvt.Nikhci,ygradientnhitvgradientpsutccng du nn gradient nhit khng km hm qu trnh dch chuyn m nh khi sy nngmngcli,nctcdngtngcngqutrnhdchchuynmtrong long vt ra ngoi bay hi lm kh vt. Khi , m trong vt liu dch chuyn ra bmtvtbmtvomitrngcthlnhnhaynhhnnhitmi trng hoc cng c th nh hn 0o. Qu trnh truyn nhit thc hin c thng qua s thay i pha lm vic ca mi cht lnh. Mi cht lnh trong gin bay hi hp th nhit v bay hi nhit Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh37 SVTH: Bi Vn Vnh thp v p sut thp. Khi hi mi cht lnh ngng t nhit cao, p sut cao ti dn ngng t, n thi nhit p sut cao hn. Khi s dng trong qu trnh sy, h thng sy s dng bm nhit lm lnh khng kh ca qu trnh n im boha,vsaungngtnc(khm),dolmtngkhnngsyca khng kh. Trong qu trnh ny ch tun hon mc nhit thp (nhit hin v nhit n) t khng kh. Cu trc ca dn bay hi v dn ngng t c b tr nh hnh v (hnh 1.11) Hnh 1.11 Hai phng thc trao i nhit thng qua bung sy. Hnh 1.12 S qu trnh sy theo hai phng thc trao i nhit Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh38 SVTH: Bi Vn Vnh Trong trng hp th nht (hnh 1.11 a), my sy lnh hot ng va nh mt my kh m va nh mt b gia nhit khng kh. Trong cch b tr th hai (hnh 1.11 b), dn bay hi c xen vo dng khng kh m trong khi khng kh sch li c a ton b vo dn ngng t. Vic sp xp theo kiu ny, nhit n (cng vi mt lng ln nhit hin) c hi lu bng cch kh m kh thi v truyn cho tc nhn sy qu trnh thng qua dn ngng t. M hnh ny thch hp khi khng kh mi trng kh ( m tng i thp), nhng n li khng kinh t, bi v dng kh thi tng t nh khng kh bn trong. Trong c hai m hnh trn,khthitbungsycthchiluliindnbayhinghal khng kh c th tun hon ton b hay tng phn. Ta c th qu trnh sy nh hnh 1.12 tng ng vi hai trng hp b tr trn hnh 1.11 1.5.2 Nguyn l lm vic ca h thng sy lnh Khc vi phng php sy nng, trong phng php sy lnh, ngi ta to ra chnh phn p sut hi nc gia vt liu sy v tc nhn sy bng cch gim phn p sut trong tc nhn sy nh gim lng cha m. phng php sy lnh, nhit b mt ngoi ca vt nh hn nhit bn trong vt, ng thi do tip xc vi khng kh c m v phn p sut hi nc nh nn b mt cng c phn p sut hi nc nh hn pha bn trong vt. Ni khc i, y gradient nhit v gradient p sut c cng du nn gradient nhit khng km hm qu trnh dch chuyn m nh khi sy nng m ngc li, n c tc dng tng cng qu trnh dch chuyn m trong lng vt ra ngoi bay hi lm kh vt. Khi m trong vt liu dch chuyn ra b mt v t b mt vo mi trng c th ln hn hoc nh hn nhit mi trng hoc cng c th nh hn 0oC. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh39 SVTH: Bi Vn Vnh Hnh 1.13 S h thng sy lnh 1.6 Cc thit b trong h thng sy lnh Bm nhit l mt thit b dng bmmt dng nhit tmc nhit thp ln mc nhit cao hn, ph hp vi nhu cu cp nhit. My lnh cng l mt loi bm nhit v c chung mt nguyn l hot ng, cc thit b ca chng v c bnlgingnhau.chphnbitmylnhvibmnhitmcchsdng. My lnh gn vi vic s dng ngun lnh thit b bay hi cn bm nhit gn vivicsdngngunnhitthitbngngt.Dosdngngunnhitnn bm nhit hot ng cp nhit cao hn. a) Mi cht v cp mi cht Michtvcpmichtcabmnhitcyucunhmylnh.Mtvi yu cu c bit hn xut pht t nhit si v ngng t cao hn, gn ging nh ch nhit cao ca iu hakhng kh, ngha l cho n nay ngi ta vn s dngccloimichtnh:R12,R22,R502vMRchomytuabin.Gny ngi ta ch n vic s dng cc mi cht mi cho bm nhit nhm nng cao nhit dn ngng nh: R22, R113, R114, R12B1, R142 b) My nn lnh Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh40 SVTH: Bi Vn Vnh Cng nh my nn lnh, my nn l b phn quan trng nht ca bm nhit. Tt c cc dng my nn ca my lnh u c ng dng trong bm nhit. c bit quan trng l my nn piston trt, my nn trc vt v my nn tuabin. Mt my nn bm nhit cn phi chc chn, tui th cao, chy m v cn phi c hiu sut cao trong iu kin thiu hoc ti. c) Cc thit b trao i nhit Cc thit b trao i nhit c bn trong bm nhit l thit b bay hi v thit bngng t. My lnh hp th c thm thit b sinh hi v hp th. Ging nh my lnh,thitbngngtvbayhicabmnhitcngbaogmccdng:ng chm,nglngngcdng,ngngvngkiutm.Ccphngphptnh ton cng ging nh cc ch iu ho nhit . d) Thit b ph ca bm nhit Ttcccthitbphcabmnhitgingnhthitbphcamylnh. Xut pht t yu cu nhit cao hn nn i hi v tin cy, cng ngh gia cng thit b cao hn. y cng l vn t ra i vi du bi trn v mkn cc loi trong h thng. Do bm nhit phi hot ng ch p sut v nhit gn st vi gii hn ti a nn cc thit b t ng rt cn thit v phi hot ng vi tin cy cao phng nga h hng cc thit b khi ch lm vic vt qu gii hn cho php. i vi van tit lu, bm nhit c ch lm vic khc my lnh nn cng cn c van tit lu ph hp. e) Thit b ngoi vi ca bm nhit Thit b ngoi vi ca bm nhit l nhng thit b h tr cho bm nhit ph hp vi tng phng n s dng ca n. Thit b ngoi vi ca bm nhit gm mt s loi sau: Cc phng n ng lc ca my nn nh: ng c in, ng c gas, ng c diesel hoc ng c givv Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh41 SVTH: Bi Vn Vnh Cc phng n s dng nhit thu dn ngng t. Nu l si m th c th s dng dn ngng trc tip hoc gin tip qua mt vng tun hon cht ti nhit, c th s dng sy, nu n, ht mMi phng n i hi nhng thit b h tr khc nhau. Ccphngncpnhitcho dn bayhi.Trnghps dngdnlnh ngthivinngthphadnbayhicthlbunglnhhocchtti lnh. Ngoi ra cng c th s dng dn bay hi t ngoi khng kh, dn bay hi s dng nc ging l mi trng cp nhit. Cng c nhng phng n nh dn bay hi t di nc, t di t hoc s dng nng lng mt tri. Cc thit b iu khin,kim tra t ng s hot ng ca bm nhit v cc thitb h tr.ylnhngthit bt ng iu khinccthit b ph tr ngoi bm nhit ph hp vi hot ng ca bm nhit1.7 Mt s kt qu nghin cu v sy lnh ca cc tc gi trong v ngoi nc Vic s dng bm nhit trong cng nghip cng nh dn dng sy, si, ht m, iu ha khng kh, c nghin cu v ng dng rt nhiu trn th gii. Sau y l tng quan mt s cng trnh nghin cu :1.7.1 Cc tc gi trong nc Tc gi Phm Vn Ty v cc cng s tin hnh nghin cu v ng dng thnh cng h thng bm nhit sy lnh ko Jelly, ko Chew, Caramel, ko Cng ti cng ty bnh ko Hi H [19]. Nm 1997, 1998 cc tc gi thit k ln lt hai h thng lnh theo nguyn lbmnhitnhitthpkiumun.sykoJellyvinngsut1100 kg/ngy v 1400 kg/ngy hin nay vn cn c s dng cho phng sy lnh s 2 v s 3 Nh my thc phm Vit Tr- Cng ty c phn bnh ko Hi H. Thng Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh42 SVTH: Bi Vn Vnh snhitkhngkhbungsy22-280C,m30-40%.Snguynlh thng nh hnh 1.14 Hnh 1.14 S nguyn l h thng bm nhit kiu mun MththngmyhtmhtrchodychuynsnxutkoCaramem caCngHaLinBangccitotmyiuhakhngkhcchophn xng ko caramem v h thng bm nhit ht m cng sut lnh 120.000 Btu/h s dng 4 my lnh Trane TTK 530 cng sut mi my l 30.000 Btu/h hin nay ang s dng cho phng bao gi ko cng thuc X nghip Cng ty CP Bnh ko HiHclpttnm1999.Quathctsdng,thyrngngoiu im r tin (gim khong 50% vn u t) v tit kim nng lng (in nng tiu th gim gn 50%) so vi phng n dng my ht m, cc h thng ht m vsylnhnyhotngnnh,lintcvgimchiphbodng.Tuy nhin, n cn c nhc im l cng knh, s dng nhiu qut v ng c xen k, trong h thng nhiu bi bt nn phi bo dng ng c li phi thc hin trong khng gian hp, kh thao tc. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh43 SVTH: Bi Vn Vnh khcphcnhngnhcimtrnnm2005 nhmtcgi thitk chtomysylnhchophngsylnhs1theonguynlbmnhitkiu nguyn khi BK-BSH18A. So vi cng ngh dng cc bm nhit kiu m un th BK-BSH18A c thit b x l khng kh c ch to dng t hp gn c th t ngoi nh, trong nh hay trong bung sy v tc khng kh c th thay i ph hp vi yu cu ca vt liu sy khc nhau. Vics dngbmnhit nhit thp htmvsylnh c nhiuu im v rt c kh nng ng dng rng ri trong iu kin kh hu nng m ph hp vi thc t ti Vit Nam, mang li hiu qu kinh t- k thut ng k. Bm nhit sy lnh c bit ph hp vi nhng sn phm cn gi trng thi, mu, mi, chtdinhdngvkhngchophpsynhitcao,tcgiln.Cch thng ht m v c bit l cc h thng sy lnh c cu trc lun thay i ph thuc vo c tnh ca vt liu sy, cu trc ca dn lnh s dng, nn khng cmtcutrcchungchottcccitngsy,tuynhinvncchung nguyntcvphngphptnhtonthitk.Do,cnphitiptcnhng nghin cu c bn, y v cc qu trnh, cc gii hn k thut v cc vn t ngiuchnhkhngchlinhonnhitvmcatcnhnsycng nh ca vt liu sy. 1.7.2 Cc tc gi nc ngoi MacioN.Kohayakawavcccngs[19]tinhnhnghincunh hngcaccyutnh:vntcgiVar,chiudycavtliuLnhs khuchtnqutrnhsyDeftronghthngsyxoibngbmnhit.Micht lnhsdngtronghthnglR22.Hthngsyxoisdnghaidnngng trong gia nhit cho khng kh. Nhit khng kh trong qu trnh th nghim thay i t 40oC n 56oC. Vn tc gi thay i t 1,6 m/s n 4,4 m/s, chiu dy vt liu sy thay i t 5,8 mm n 14,2 mm. Khi lng vt liu sy mi m l 300g,thigiansyl8h/m.Davoccquanhlthuyttnhtonhs Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh44 SVTH: Bi Vn Vnh khuch tn, s dng phng php quy hoch trc giao v kt hp vi s liu thc nghim, cc tc gi xy dng c phng trnh hi qui xc nh h s khuch tn Def nh sau:Def=4,2625-0,61922.Var+0,380538.Var2+1,012517.L0,90343.Var.L(1.23) Phng trnh (1.23) cho thy rng nh hng ng thi ca hai thng s cng nhmcnhhngcachngnhskhuchtnDef.y,nhhng ca tc gi Var l ln nht, sau n chiu dy ca vt liu sy. Phng trnh (1.23) cng cho bit nh hng ln nhau gia hai thng s thng qua mi lin h cho nhau gia chng. Tuy nhin, phng trnh ny khng cp n nh hng ca nhit , m sy mc d nh hng ca chng l ln n h s khuch tn. iu ny cng c chnh tc gi khng nh trong nghin cu ca mnh. Do vy, cn c nhng nghin cu nh gi v nh hng ca cc yu t ny. PhaniK.Adapa,GregJ.SchoenauvShahabSokhansanj[19]tinhnh nghin cu l thuyt v thc nghim qu trnh sy bng bm nhit i vi cc vt liu c bit. Cc tc gi tin hnh thit lp cc quan h tnh ton l thuyt qu trnhsylpmng.Cctcgithitlpphngtrnhcnbngnnglng, cn bng cht, truyn nhit v truyn m gia vt liu v khng kh cho mt phn t th tch vt liu sy nh sau: Phng trnh truyn m ( )eMk M Mtc= c (1.24) Trong : M - m cn bng ca vt liu sy ti thi im t Me - m cn bng ca vt liu sy, c xc nh bng thc nghim t - thi gian sy, s k-hngssy[1/s],cxcnhnhsau:( ) k=0,2865.exp 0,179.Ta(1.25) Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh45 SVTH: Bi Vn Vnh Gii phng trnh (1.24) ta xc nh c m ca vt liu khi sy ti thi im t nh sau:

( )00. .kt kte eM M M M e e= + (1.26) Vi M0 : m ca v liu sy ti thi im t0 = 0 Phng trnh cn bng cht .paGW Mx G yc c= c c (1.27) Vi:W - cha hi ca khng kh x - chiu dy ca vt liu sy Gp - lu lng vt liu sy chuyn ng qua bng ti, kg/m.s Ga - lu lng khng kh chuyn ng qua bng ti, kg/m2.s y - qung ng dch chuyn ca vt liu sy, m Giiphngtrnh(1.27),thuccngthcxcnhsthayicacha hi W theo chiu dy vt liu sy (gi thit tnh cht ca vt liu sy lng u theo phng dch chuyn y):

0. .PaG MW W xG yc= c(1.28) Phng trnh cn bng nng lng

( ) ( ) ( )( ). . / .. .cv a pw a gaa pa pwh G G W x T TTxG C C W+ c c c= c+(1.29) Trong : Ta - nhit ca khng kh sy, 0C Tg - nhit ca vt liu sy, 0C hcv - h s truyn nhit th tch, kJ/m3.ph.K Cpa - nhit dung ring ca khng kh kh, kJ/kgK Cpw - nhit dung ring ca hi nc, kJ/kgK Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh46 SVTH: Bi Vn Vnh Gii phng trnh (1.29), xc nh c nhit khng kh ti u ra:

( )( / ).0.d a xa g g aT T a T T = + Trong : ( ). .a pa pwa G C C W = + . .cv a pwWd h G Cx| | |\ .c= +c Ta0 - Nhit khng kh ti v tr ban u x0 = 0, 0C

(

(

)(

(

(

)

))(

)

(

))(1.30) Trong : Lg - nhit n ha hi ca nc trong vt liu sy, kJ/kg Cpg- nhit dung ring ca vt liu sy, kJ/kgK Cpl- nhit dung ring ca nc, kJ/kgK Gii phng trnh (1.30) ta s tm c s thay i nhit ca vt liu sy :

((

) ((

)

))(1.31) y: ( )0. . . ; . .cv a g cv pw a a plW Wf h T G L g h C C Gx x| | |\ .c c= = + c c ( ). .p pg plh G C MC = + 1.8 So snh phng php sy lnh vi phng php sy nng nh my Sy l qu trnh tch nc v hi nc ra khi vt. Tuy nhin, sy l mt qutrnhcngnghihisaukhisy,vtliuphimbochtlngcao, tiu tn nng lng t v chi ph vn hnh thp. C hai phng php sy: a) Phng php sy nng ti nh myTrong phng php sy nng, tc nhn sy v vt liu sy c t nng. Do tc nhn sy c t nng nn m tng i gim dn n phn p sut Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh47 SVTH: Bi Vn Vnh hi nc Pam trong tc nhn sy gim. Mt khc do nhit ca vt liu sy tng ln nn mt hi trong cc mao qun tng v phn p sut hi nc trn b mt vt cng tng theo cng thc: = orpp = exp)`r ohp o 2(1.32)Trong Pr -p sut trn b mt ct mao dn, N/m2 Po - p sut trn b mt thong, N/m2 - Sc cng b mt thong,N/m2 h - mt hi trn ct dch th trong ng mao dn, kg/m3 0 -mt dch th, kg/m3 Nh vy trong h thng sy nng c hai cch to ra chnh phn p sut hi nc gia vt liu sy v mi trng: Gim phn p sut ca hi nc trong tc nhn sy bng cch t nng. Tng phn p sut hi nc trong vt liu sy. Tm li, nh t nng c tc nhn sy v vt liu sy hoc ch t nng vt liu sy m hiu s gia phn p sut hi nc trn b mt vt Phb v phn p sut hinctrongtcnhnsyPhtnglndnnqutrnhdchchuynmt trong lng vt liu sy ra b mt v i vo mi trng. Do, hthng synngthngcphnloitheo phngphp cung cp nhit: H thng sy i lu Vt liu sy nhn nhit bng i lu t mt dch th nng m thng thng l khng kh nng hoc khi l. H thng sy i lu gm: h thng sy bung, h thng sy hm, h thng sy kh ng. H thng sy tip xc Vtliusynhnnhittmtbmtnng.Nhvytronghthngsy tip xc, ngi ta to ra chnh lch p sut nh tng phn p sut hi nc Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh48 SVTH: Bi Vn Vnh trn b mt vt liu sy. H thng sy tip xc gm: h thng sy l, h thngsy tng H thng sy bc x Vt liu sy nhn nhit t mt ngun bc x dn m dch chuyn t lng vtliu syrabmt v tbmtvomitrng.yngi ta tora chnhphnpsuthincgiavtliusyvmitrngbngccht nng vt. H thng sy dng dng in cao tn hoc dng nng lng in t trng Khi vt liu sy t trong mi trng in t th trong vt xut hin cc dng in v chnh dng in ny s t nng vt. u im ca phng php sy nng ti nh my-Thi gian sy bng cc phng php sy nng ngn hn so vi phng php sy lnh. -Nng sut cao v chi ph ban u thp. -Ngunnnglngsdngchophngphpsynngcthlkhi thi,hincnng,hayccngunnhittdum,than,rc thi,...cho n in nng. -Thi gian lm vic ca h thng cng rt cao. Nhc im-Ch sy c cc vt sy khng cn c cc yu cu c bit v nhit . -Sn phm sy thng hay b bin mu v cht lng khng cao.-V nh my dng in tr sy nn lng nhit ta ra l rt ln, qun tnh nhit cao kh iu chnh nhit -Chi ph in nng cao -Snphmsaukhisychtlngkhngngu,xyratnhtrng nguyn liu b chy do qun tnh nhit ln cao. b) Phng php sy lnh Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh49 SVTH: Bi Vn Vnh Trongphngphpsylnh,ngitatorachnhpsuthinc gia vt liu sy v tc nhn sy bng cch gim phn p sut hi nc trong tc nhnsyPhnhgimchamd.Miquanhcthhintheocng thc: Ph= dd B+ 621 , 0.(1.33) Trong B - p sut mi trng (p sut kh tri). Khi,mtrongvtliudchchuynrabmtvtbmtvomi trng c th trn di nhit mi trng (t > 0 oC) v cng c th nh hn 0 oC. c)So snh phng php sy lnh v phng php sy nng tin hnh so snh thc nghim phng php sy lnh vi phng php sy nng, cc loi rau c thc phm v dc liu nh c rt, c ci, hnh l, da, mt, nhn, mng ct, hnh ty, hn hp dch p gng v bt avicel, c sy thnghimvikhongthngsnhitsyt=250Cn400C,tcgi =2,2-4m/s . Kt qu sn phm sau th nghim c cc c im v mu sc, mi v, hm lng cht dinh dng v trng thi vt sy c bo ton hn hn cc cng ngh sy nng truyn thng, ngay c khi so snh vi k thut sy hin i bng tia hng ngoi. iu chng t nhng c im u vit ca cng ngh sy lnhtrongvicngdngsynhngloirauqugiuvitamin,cgitrdinh dng cao trong thc t [19]. Di y l bng so snh cc phng php sy khc nhau vi phng php sy lnh s dng bm nhit nhit ca Vin Cng Ngh Thc Phm, s Cng Nghip H Ni da trn cc tiu ch v cht lng sn phm, gi thnh sn phm, thi gian sy, chi ph u t, chi ph vn hnh v bo v mi trng, phm vi ng dng, vv Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh50 SVTH: Bi Vn Vnh Bng1-1 nh gi so snh cht lng sn phm sy bng bm nhit sy lnh vi phng php sy nng truyn thng v sy hng ngoi [Vin Cng Ngh Thc Phm, s Cng Nghip H Ni] Th t Phng Php sy Ch tiu so snh Sy nng Sy thng hoa v chn khng Sy lnh s dng my ht m kt hp my lnh 1 Cht lng sn phm (mu sc, mi v, vitamin) Km hn rt nhiu Tt hnBng nhau 2Gi thnh sn phmThp hnt hn nhiut hn 3Thi gian syNgn hnNgn hnLn hn hoc bng 4Chi ph u t ban uthp hnCao hn Cao hn 5Chi ph vn hnh, bo dngr hnt hn nhiut hn 6 Kh nng iu chnh nhit tc nhn sy theo yu cu cng ngh Kh hnKh hnKh hn 7V sinh an ton thc phmkm hnTt hnBng nhau 8Bo v mi trngkm hnNh nhauKm hn 9Phm vi ng dngRng hnHp hnHp hn 1.9 nh gi v kt luna) So vi sy lnh s dng my ht m chuyn dng kt hp my lnh Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh51 SVTH: Bi Vn Vnh Sy lnh s dng bm nhit nhit thp t ra u th vttri v chi ph utbanu,gimtiuhaoinnng.ViiukincaVitNamthnn dngphngphpsylnhsdngbmnhitnhitthp.Trongthct, mtsnhmynhpdychuyncngnghsysdngmyhtmchuyn dng kt hp vi my sy khng t hiu qu v chuyn sang dng bm nhit nhit thp. b) So vi sy thng hoa v sy chn khng Cht lng sn phm ca hai phng php ny thng tt hn sy lnh s dng bm nhit nhit thp nhng cc ch tiu quan trong 2 v 5 li km hn nnchpdnghaiphngphpnykhiyucuvchtlngsnphmcao (ch tiu 1, 7), cn li nn s dng phng php sy lnh bng bm nhit nhit thp. c) So snh vi sy nng Nhn chung, c mt s vt liu sy lnh khng c hiu qu nh sy g, cc loi hoa qu c v dy th buc phi s dng sy nng. i vi cc vt liu cn li,nuvtliusynhycmvinhit,dmtmu,dmtmi,chtdinh dng, gi thnh sn phm c th trng chp nhn v thi gian sy khng i hi phi nhanh th nn sy bng phng php sy lnh s dng bm nhit nhit thp. Nh vy, phng php sy lnh bng bm nhit nhit thp t ra c hiu qu, nht l i vi mt s sn phm c th (nhy cm vi nhit ) Do , ty vo tng trng hp c th, xem xt cc ch tiu trong bng trn, ch tiu no l quan trng th quyt nh phng php sy ph hp. d) Kt lun u im ca cng ngh sy lnh c th xy dng c tng quy trnh cng ngh sy hp l i vi tng loi rau, c, qu. Sau khi sy, nng sn, thc phm gi c nguyn mu sc, mi v, thnh phn dinh dng tht thot khng ng Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh52 SVTH: Bi Vn Vnh k,ttiuchunvsinhantonthcphmcaVitNamvccchtiuk thut,chtlngsnphmtngngmtsnckhctrnthgii.Vit Nam l mt nc c kh hu nng m, v th my sy lnh l cng ngh c bit phhpviccloinngsn,thcphm,mbocchtlngcngnh hm lng dinh dng, mu sc, mi v cho sn phm. i vi cc sn phm nh ccrt,thl,hnhhayccloikochocolate,koCaramen,Jelly...Mi trng ch bin nhng sn phm ny yu cu v nhit khng c qu cao v m phi nh hn 45-50%. Tnh mi ca cng ngh ny l qu trnh sy c thc hin nhit thp, to mi trng nhit cng chiu vi mi trng mtngcngsy.Ngoira,cngnghnycnhiuuimkthut khcnh:htmnhngkhnglmtngnhitmitrngnhmyhtm thngthng,sykhcccsnphmkhngchophplmkhtrongmi trng nhit cao. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh53 SVTH: Bi Vn Vnh CHNG II TM HIU V CNG NGH SY HNH L 2.1 Vt liu syTt c cc sn phm u chu bin i trong qu trnh sy v bo qun sau . Yu cu t ra i vi qu trnh sy l bo v ti mc tt nht cht lng, hn ch nhng h hi trong qu trnh sy, bo qun ng thi nng cao hiu qu kinh t mt cch ti u nht. Xt v c bn nhng thay i trong qu trnh sy c th chia ra : -Nhng thay i l hc: st m, gy, v, -Nhngthayiha l: trng thi tnhchtca nhngkeocaophn tb thay i. -Nhngthayi ha sinh: do soxi hacacht bo, phnng smmu phi enzim, phn ng enzim, -Nhng thay i do vi sinh vt Nhng thay i lm thay i cu trc mu sc mi v, gi tr dinh dng v cnh hng ntnh hi nguynca snphmsaukhisy.Ccphng php sy khc nhau c nhng u im v nhc im trong qu trnh sy cc sn phm rauqu.Trong,phngphpsynngpngcccyucuvnng sut,thigiansynhnglikhngpngttccihivchtlngsn phm. Ngc li, i vi cc sn phm sy yu cu nhit thp i hi phi c quy trnh sy ph hp hn. Cng ngh sy lnh l mt cng ngh mi c dng giiquytccvnkhngthgiiquytivicngnghsynng.T nghin cu thc nghim chng minh nhng u im vt tri ca cng ngh sy lnh trong qu trnh xy dng quy trnh sy i vi cc loi rau c qu c gi tr kinh t. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh54 SVTH: Bi Vn Vnh 2.1.1 S cng ngh sy rau quRau qu (phi thch hp cho qu trnh sy) Lm sch (kh, t) La chn phn loi (theo kch thc) Gt sa Ct, thi (ty theo yu cu) Chn, hp (ty theo yu cu) X l ha hc (nu cn) ChCh p SySyC c Lm nguiLm nguiC c Sy Phn loiPhn loiPhn loi p bnhNghin nh ng ging ging gi Sn phmSn phm dngSn phmdng nguynbn mngdng bt Hnh 2.1 S cng ngh sy rau qu Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh55 SVTH: Bi Vn Vnh 2.1.2nh hng ca qu trnh sy n cht lng sn phm a) nh hng n cu trc Thay i v cu trc ca cc vt liu l mt trong nhng nguyn nhn quan trng lm gim cht lng sn phm. Bn cht v mc ca cc bin php x l rau qu trc khi sy u c nh hng n cu trc ca cc sn phm sau khi hi nguyn. Nguyn nhn l do s h ha ca tinh bt, s kt tinh ca xenluloza v shnhthnhccsccngbntrongdokhcbitvmccvtrkhc nhau. Kt qu la s to thnh cc vt nt gy, cc t bo b nn p vn vo vnh vin, lm cho sn phm c b ngoi b co ngt, nhn nheo. Trong qu trnh lm t tr li sn phm ht nc chm, khng th ly li hnh dng nh ban u. Cc sn phm khc nhau c s dao ng v mc co ngt v kh nng hp th nc tr li. Sy nhanh nhit cao lm cho cu trc b thay i nhiu hn so vi sy vi tc va phi nhit thp. Trong qu trnh sy, cc cht ha tan di chuyn theo nc t bn trong ra b mt ngoi ca sn phm. Qu trnh bay hi lm c c cc cht tan b mt, kt hp vi nhit khng kh (c bit khi sy tri cy, c, tht,) gy ra cc phn ng l ha phc tp ca cc cht tan b mt ngoi nn lp v cng khng thmc. Hin tng ny gi l hin tng cng v(casehardening),lmgimtcsyvlmchosnphmcbmt kh,nhngbn trongthm.Vvycnkimsot nhitsytrnhchnh lchmqucaogiabntrongvbmtsnphm.ivikthutsylnh hon ton c th gii quyt c vn ny. H thng sy lnh c nhit tng ithpchonnqutrnhkhcabmtvtliuschmhntrongkhim c ly ra nhiu bng s chnh lch phn p sut hi ngoi b mt v bn trong vt liu sy. b) nh hng n mi v Nhit lm tht thot cc thnh phn d bay hi ra khi sn phm v vy phn ln cc sn phm sy b gim mi v. Mc tht thot ph thuc vo nhit Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh56 SVTH: Bi Vn Vnh v m ca vt liu sy, p sut hi nc v ha tan ca cc cht bay hi trong nc. Nhng sn phm c gi tr kinh t cao nh vo c tnh mi v (nh giav)cncsynhitthp.Mtssnphmcktcuxptoiu kin cho oxi khng kh d dng tip xc vi sn phm, gy ra cc phn ngoxi hachttanvchtbotrongqutrnhboqunlmthayimivcasn phm. Tc ca qu trnh gy h hng ph thuc vo nhit bo qun v hot canc.Phnlnrauquchchamtlngnhlipit.Tuynhin,soxi haccchtbokhngnotoracchydroperoxitthamgiavoccphnng polime ha, phn ng tch nc hoc oxi ha to thnh aldehit, Kenton v cc axit gy mi i thui kh chu. c) nh hng n mu sc C nhiu nguyn nhn gy ra s mt mu hay thay i mu trong sn phm sy, nh l: S thay i cc c trng b mt ca sn phm gy ra s thay i phn x nh sng v mu sc. Nhit v s oxi ha trong qu trnh sy gy ra nhng bin i ha hc i vicarotenoitvclorophyl,cngnhhotngcaenzim polyphenoloxidazagynnssmmutrongqutrnhboqunccsn phm rau qu. Cthngnngacnhngthayinybngccphngphpchn hp hoc x l tri cy bng axit ascorbic hoc SO2. d) nh hng n gi tr dinh dng Ccsliuvsthtthotccchtdinhdngcacctcgithng khng thng nht, c th do s khc bit ng k trong cc qu trnh chun b sy, nhit v thi gian sy, cng nh iu kin bo qun. rau qu, tht thot dinh dngtrongqutrnhchunbthngvtxaqutrnhsy.Vd,thtthot Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh57 SVTH: Bi Vn Vnh vitamin C trong qu trnh chun b to sy (dng khi) l 8% do qu trnh ct gt, 62% do chn hp, 10% do qu trnh nghin pu r v 5% do qu trnh sy. Vitamin c ha tan trong nc khc nhau v khi qu trnhsy din ra, mt vi loi (v d: vitamin B2 riboflavin) t trng thi bo ha v kt ta khi dung dch, nh vy chng t b tn thng. Mt s khc, v d: axit ascorbic, ha tan ngay c khi m ca sn phm h xung n mc rt thp, chng phn ng vi cc cht tan vi tc cng lc cng cao hn trong qu trnh sy. Vitamin C cng rt nhy cm vi nhit v oxy ha. V th trnh nhng tht thot ln cn sy trong thi gian ngn, nhit thp, bo qun m thp v nng kh oxi thp. Thiamin (Vit B1) cng nhy cm vi nhit, tuy nhin cc vitamin khc ha tan trongnc bnvinhit voxyhahnvtntht qutrnhsyhimkhi vt qu 5-10%, ngoi tr tht thot do qu trnh chn hp. S tn tht cc vitamin c th hn ch ng k hoc ngn nga hon ton khi sdngccphngphpsynhanhvnha(nhsyphun),cbitbng phng php sy thng hoa i vi cc nguyn liu nghin nt, nguyn cht dng ct nh.Cc cht dinh dng nh cht bo (v d: cc axit bo khng thay th c vccvitaminA,D,E,K)phn lnchatrong phn chtrn ca sn phmv chngkhngbcctrongkhisy.Tuynhinncldungmicacckim loi nng, l nhng cht xc tc ca qu trnh oxy ha cc cht dinh dng khng no. Khi nc b mt, cht xc tc tr nn hot ng hn v lm tng tc oxy ha.Ccvitamintantrongchtbobbinimtikhitipxcviperoxit c sinh ra do s oxy ha cht bo. gim tht thot trong qu trnh bo qun ngi ta h thp nng oxy, nhit bo qun v loi tr nh sang tip xc vi sn phm. e) nh hng n s hi nguyn sn phm (rehydration) Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh58 SVTH: Bi Vn Vnh Sn phm sau khi sy khng th tr li tnh trng ban u khi lm t tr li. Sau khi sy, t bo b mt p sut thm thu, tnh thm thu ca t bo b thay i, cc cht tan di chuyn, polysacarit kt tinh v protein t bo b ng t, tt c gp phn vo s thay i cu trc, lm tht thot cc cht d bay hi v y u lNhit trong qu trnh sy lm gim kh nng hydrat ha tinh bt v tnh n hi ca thnh t bo, lm bin tnh protein, gim kh nng gi nc ca chng. Tc v mc thm nc tr li c th c dng nh ch s nh gi cht lng sn phm sy. Nhng sn phm sy trong nhng iu kin ti u, t h hi hn s thm t tr li nhanh hn, hon ton hn. 2.2 Cc c tnh ha l ca mt s rau qu giu vitamin ng dng phng php sy lnhBt k mt loi nng sn phm no, trong thnh phn ca n u c cha cc nhm hp cht hu c nh protein, gluxit, lipid, vitamin, axit hu c v cc cht khong, cc sc t v.v vi t l khc nhau. Do mun bo qun tt tng loi snphmcnnghincukthnhphnha hcvnhngbin ica n ditcngcaccnhntbnngoi.Thngthngtrongthnhphnca chng c cha nhng hp cht sau: a)Nc Tuyt i a s nng sn phm u c cha mt lng nc nht nh, n thayitytheo hnh thi giiphu v trngthi keoa nctrong t bo sn phm. C nhng loi cha nhiu nc nh rau qu ti cha 65-95% nc, ht lng thc cha tng i t hn t 11-20%. Nhng nhn chung trong t bo cc loi nng sn phm u c cha cc dng nc sau y: (theo phn loi ca vin s P.A Rebinde) Nc lin kt ha hc Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh59 SVTH: Bi Vn Vnh cc trng bngquan h nhlng rtchnhxcgia snphmv nc.ylloilinktrtbnvng.Vd:Na3CO3.3H2O.Numuntch lngncnyphibngcchemnunglnhocbngcctngtchahc khc. Nc lin kt ha l Kt hp vi vt liu khng theo mt t l nht nh. N bao gm c nc hpth,ncthmthu,nccutrc.Muntchlngncnyracntiu hao mt nng lng bin n thnh th hi. Dng nc ny km bn hn. Loinykt hp visn phmkhng theomtlng nhtnh,chnh l lngnctdotrongsnphmyldngkmbnvngnht.Nc chuyndchtrongsnphmdngthlng.Muntchraphibngcchsy kh nhit 105oC. Hm lng nc trong sn phm cao hay thp c nh hng ln n cht lng v kh nng bo qun ca chng. i vi nhng sn phm c hm lng nc cao, vic bo qun kh khn hn v nc chnh l mt mi trng thun li vi sinh vt hot ng, lm cho cht lng sn phm b gim xung b) Nhng hp cht c Nit v s bin i trong qu trnh bo qun Protein l hp cht cha Nit ch yu trong nng sn phm v n l thnh phn dinh dng ch yu ca nhng sn phm c ht. N c gi tr dinh dng cao. Cc loi sn phm khc nhau, hm lng protein cha trong chng khc nhau. La cha 7-10%, ng 10-12%, cao lng 10-13%, u H Lan 22-26%, u tng 36-42%, crt 2% cc loi qu ch di 1% (Tt c tnh theo % trng lng cht kh). Trongthnhphnproteincmtyccnhm:albumin,prolamin,glutein, globulin. Trong albumin c cha cc axt amin khng thay th Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh60 SVTH: Bi Vn Vnh Prolamin c nhiu trong cc cy ha tho, c bit thnh phn protein cha trong ht ng th nhm ny ch yu chim ti 50% l zein ca ng. Globulincchanhiutronghtcdu,htcyhunhutng, proteintrongutng.Proteintrongutngc8axitaminkhng thay th. Glutelin cng l protein c trng ca ht cy ha tho, c bt ngi ta ch ti gluten ca la m. rauquhmlngproteinrtt,chchimkhong1-2%,thngch yu cc loi rau cao cp nh supl, crt, khoai ty tuy vy n c gi tr dinh dng rt cao. Trong qu trnh bo qun, ni chung Nit tngs hu nh khng thayihocthayirtt,nhngNitproteinhatanthayikhnhiu, chng phn gii thnh cc axit amin lm cho hm lng axit amin tng ln. Do lng Nit protein gim xung v Nit phiprotein trong qu trnh ny cng tng ln mt cch r rt. Trong nhng cng trnh nghin cu ca Gasiorowski v ht lamboquntrngthitimtrongcckhoknhonton,ngpht hin thy s tng ln ca hm lng Nit phiprotein sau 15 tun l bo qun. 2.4L thuyt sy rau qu 2.4.1 Quy trnh x l trc khi sy Syrauquthngthngcthchin3dngchyu:dngnguyn (hocming);dngbnmngvdngbthocnhtng.Tutheodngsn phm, cng ngh sy rau qu c s chung nh sau: Rau qu ti sau khi ra sch c loi b phn khng tiu chun, c phn c theo kch thc, lm sch, ct ming. Sau rau qu c chn (hp), x l ho cht. Tip theo, cc hnh thc sn phm khc nhau c ch bin theo cc s khc nhau. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh61 SVTH: Bi Vn Vnh - Trongkhichn(hp),dotcdngcanhitvmnntnhchtholca nguyn liu b bin i c li cho s thot nc khi sy. ng thi vi sinh vt b tiu dit v h thng enzim trong nguyn liu b mt hot tnh, hn ch ti a kh nng bin mu trong khi sy rau qu v rt ngn thi gian sy. Ngoi ra qu trnh chn lm gim ht m ca rau qu kh. - Trong cng nghip sy rau qu, ngn nga qu trnh oxy ho lm bin mu rau qu khi sy, ngi ta s dng cc cht chng oxy ho nh axit sunfur, axit ascobic,axitxitricvccmuinatricaaxitSunfur(nhsunfit,bisunfit, metabisunfit, ...) x l ho cht cho rau qu trc khi sy.2.4.2 . Cc yu t nh hng n qu trnh sy Yu t nh hng nhiu n cht lng sn phm rau qu kh l nhit sy. Nu nhit sn phm trong qu trnh sy cao hn 60 oC th prtin b bin tnh. Nu loi rau qu t thnh phn protin th nhit t nng sn phm c th ln n 80-90 oC. Nu tip xc nhit trong thi gian ngn nh sy phun th nhit sy c th ln n 150 oC. i vi sn phm khng chn nh chui, u th c th sy nhit cao, giai on u 90-100oC, sau gim dn xung. Qu trnh sy cn ph thuc vo tc tng nhit ca vt liu sy. Nu tc tng nhit qu nhanh th b mt mt qu b rn li v ngn qu trnh thot m. Ngc li, nu tc tng chm th cng thot m yu. b) m khng kh Mun nng cao kh nng ht m ca khng kh th phi gim m tng i ca n xung. C 2 cch lm gim m tng i ca khng kh [19] *Tng nhit khng kh bng cch dng calorife. *Gim nhit khng kh bng cch dng my ht m. Thngthngkhivolsy,khngkhcm10-13%.Num ca khng kh qu thp s lm rau qu nt hoc to ra lp v kh trn b mt, lm Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh62 SVTH: Bi Vn Vnh nh hng xu n qu trnh thot hi m tip theo. Nhng nu m qu cao s lm tc sy gim. Khi ra khi l sy, khng kh mang theo hi m ca rau qu ti nn m tng ln (thng thng khong 40 - 60%). Nu khng kh i ra c mquthpthstnnnglng;ngcli,nuqucaosdbng sng, lm h hng sn phmsy. Ngi ta iu chnh m ca khng kh ra bng cch iu chnh tc lu thng ca n v lng rau qu ti cha trong l sy. c) Lu thng ca khng kh Trong qu trnh sy, khng kh c th lu thng t nhin hoc cng bc. Trong cc l sy, khng kh lu thng t nhin vi tc nh (nh hn 0,4m/s), do vy thi gian sy thng ko di, lm cht lng sn phm sy khng cao. khc phc nhc im ny, ngi ta phi dng qut thng gi cng bc vi tc trong khong 0,4- 4,0m/s trong cc thit b sy. Nu tc gi qu ln (trn 4,0 m/s) s gy tn tht nhit lng.[20] d) dy ca lp sy dy ca lp rau qu sy cng nh hng n qu trnh sy. Lp nguyn liu cng mng th qu trnh sy cng nhanh v ng u, nhng nu qu mng s lmgimnngsutcalsy.Ngcli,nuqudythslmgimslu thngcakhngkh,dnnsnphmb"mhi"dohimngli. Thng thng nn xp lp hoa qu trn cc khay sy vi khi lng 5 8 kg/m2 l ph hp.[20] 2.5 Mt s phng php sy rau qu a) Phng php sy bng khng kh Cng vic ny c tin hnh bng cch tri rau qu ln cc loi b mt ngoi tri nhn nh sang mt tri trc tip. Tuy nhin, sn phm c cht lng km do kh kim sot c vn v sinh, iu chnh m, nhit v tc sy.Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh63 SVTH: Bi Vn Vnh Ngi ta ch to my sy dung nng lng mt tri nhm khc phc nhng nhc im trn. Thit b ny s dng mt c cu rt n gin c tc dng tng cng nhit t mt tri v bo v sn phm. Cnchphnbitgiasytrctipvsygintipbngnnglng mt tri. i vi sy trc tip, sn phm c t di nh nng mt tri v kt qu l s thay i v mu sc, thnh phm vitamin. i vi sy gin tip, nguyn liunycbovkhinhsngtrctiptmttri.phngphpny, ngi ta s dng mt phng ring thu nhn nhit lng t mt tri v ti , khng kh c cp nhit ri thi qua phng cha sn phm. My sy c hc dng nhin liu t nng khng k mt cch trc tip, thc phmcsybng kh t, hocmt cchgin tip thcphmcsy bng khng kh nng do kh t. Hai hnh thc ny u c kh nng kim sot tt hnsovisybngmttrivcthtinhnhcngylnm,khngph thucvothitit.Tuynhin,chiphutvvnhnhchothitbnykh cao. i vi cc sn phm c la chn phn loi tt t nguyn liu ban u, cng on ra v x l cng quan trng nh cng on sy. b) Phng php sy lt Phngphpnytinhnhsymthochnhpnhiuloirauqu( c x l bng dioxyt sunfua nhm hn ch mt mu v vi sinh vt pht trin) dng lt mng. Loi ny thng c dng nh thc phm n nh, c th tng ngt bng cch b sung ng vo nguyn liu ban u hoc thay i thnh phn nh thm hnh nhn, da no hay bt gia v. c) Phng php sy b sung V d nh chui c sy trc nhm loi b lp ng dnh tip tc c sy b sung. Vic ng gi v bo qun sn phm sy kh i hi nhiu yu cu. Sn phm sau khi sy cn c bo qun trnh nh sng mt tri, m v nhitnhmngnngasgimhngvvhhng.Ngitathngdng Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh64 SVTH: Bi Vn Vnh dngcchabnggm,thytinh,kimloihaynhachotikhichngc nghp.GiiphprnhtlsdngtimngmngPEviiukinphi c ghp mng bng. Ni bo qun cn thong mt, trnh xa nh sng mt tri, cn trng v loi gm nhm. a s, sn phm sy u n nh cht lng trong nhiu tun. 2.6 La chn phng php sy lnh theo hng nghin cu ca ti T nhng c tnh u vit ca cng ngh sy lnh ta nhn thy rng cng ngh ny c nhiu u im v hiu qu kinh t cao trong vic ng dng vo sy ccsn phm rau qu c gi tr kinh t. Tuy nhin, t l thuyt n thc tin l mtqutrnhlmvicludiihiqutrnhutnghincutm.Cng nghsylnhcthgiiquythnchcacngnghsynngtrongccquy trnh sy rau qu. Tuynhin, vic ng dng cng ngh sy lnh i vi cc loi sn phm rau c khc nhau cn phi nghin cu c lp, t xy dng nhng quy trnh cng ngh chun cho cc loi hoc cc dng rau qu. T yu cu thc t , cn thit phi tnh ton thit k mt m hnh thc t v kim tra thc nghim iviccquytrnhcngngh.NidungthchinChngIV:Tnhton thit k m hnh my sy lnh s dng bm nhit s trnh by r ni dung ny. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh65 SVTH: Bi Vn Vnh CHNG III KHO ST THC TRNG V LA CHN PHNG PHP SY 3.1 Kho st my sy ti nh my L mt doanh nghip chuyn ch bin tm xut khu sang th trng cc nc trong khu vc, nm 2007, trc tnh hnh nguyn liu tm ngy cng c nhiu bin ng v mt gi c, Chi nhnh Cng ty c phn thy sn Bc Liu ti Khnh Ha chuyn hng sang ch bin nng sn xut khu. Bc i ny khng ch mang v li nhun hng nm ln n 9 triu USD cho cng ty, gip th trng tiu th hng ha n nh m cn gip Cng ty d dng hn trong vic ch ng ngun nguyn liu phc vsn xut v xut khu.Trong xu th cnh tranh ca nn kinh t th trng, cng vi l vn b ng v ngun nguyn liu thy sn, thng xuyn nh hng n hot ng sn xut ca doanh nghip, nm 2007, Chi nhnh Cng ty c phn thy sn Bc Liu ti Khnh Ha mnh dn th nghim xut khu nhng l hng nng sn u tin. Thi gian u, doanh nghip sn xut song song va ch bin tm va ch bin c tm v u bp, sau nhn thy li nhun t nhng mt hng nng sn, chi nhnh chuyn hn sang ch bin rau qu xut khu. Hin nay, ngoi c tm v u bp, n v tng cng thm 3 mt hng rau qu khc l b ngi, t v hnh l. Cng vi mt hng nng sn l cc mt hng kh, hin nay hnh l kh ang c xut khu vi s lng ln qua th trng nht. H thng sy ca nh my c u t ban u vi 12 bung sy mi bung c cng sut 100kg/m, mi bung c din tch 4m2 bn di c thit k cc mt sng c cc l nh, vi 27 thanh in tr mi thanh c cng sut 6kW, lng in ta ra do mi bung lm vic l rt ln. Hin nay my sy ti nh my Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh66 SVTH: Bi Vn Vnh ch phc v cho vic sy hnh v mt s mt hng nng sn c nhu cu ca khch hng v lng in ta ra l rt ln.3.2 Nhim v thit k Bn cnh vic nghin cu iu tra ngun nguyn liu ca nh my cung cp cho h thng sy , vic phn b nguyn liu trong nm , phng thc vn chuyn nguyn liu v ngun tiu th. Ngoi ra vic xc nh vic ngun nng lng cung cp cho h thng, cui cng ta xc nh sn lng cn sy trong nm. Trn c s ta xc nh cng xut thit b sy theo sn phm G2 , kg/h. Bc tip theo ta tin hnh nghin cu cc thng s ch yu ca vt liu sy, yu cu v cht lng sn phm. Da trn kt qu ta xc nh cng xut thit b sy G2, kg/h . m u ca vt liu v m sau cng khi sy. Cui cng l cht lng ca sn phm v so snh vi h thng sy ca nh my khi sy bng in tr. 3.3 Chn phng n thit kQua qu trnh kho st ta la chn phng n thit k l sy vt liu bng bm nhit vi thit k l h thng sy tng si : rt ph hp vi sy hnh, di tc dng ca TNS vi thng s thch hp VLS lun trng thi bay l lng. Qa trnh sy lien tc s cho hnh c kh v nh phn trn ca lp si d dng ly ra khi thit b sy Trong h thng ny s truyn nhit v m gia tc nhn sy v vt liu sy l rt tt nn trong cc h thng sy ln th sy tng si c cng xut ln , thi gian sy nhanh v vt liu sy c cht lng rt u. 3.4 Chon tc nhn sy v nng sut sy Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh67 SVTH: Bi Vn Vnh Tc nhn ca h thng sy phi m bo y cc yu cu v nhit , m, iu kin v sinh Khng kh m y l tc nhn sy ph bin nht hin nay dng cho hu ht cc loi sn phm v m bo v sinh cho sn phm. CHNG IV Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh68 SVTH: Bi Vn Vnh TNH TON THIT K M HNH MY SY LNHS DNG BM NHIT 4.1 Gii thiu bi ton thit k v m hnh thit kCc loi rau qu rt nhy cm vi nhit cao, c bit l cc loi vitamin v khong cht, nhit trn 600C cc cht ny bt u phn hy, dn n lm gimgitrdinhdngcngnhgithnhcasnphm[20].ivicc phng php sy nng, vic ly m t vt liu ch thc hin c bng vic t nng vt liu hoc tc nhn sy ln n nhit cao, s khng p ng c cc yu cu v cht lng. gii quyt vn ny, my sy lnh s dng bm nhit rai,lphngphpsymviclymtvtliusycthchinbng cch to ra s chnh p gia tc nhn sy v vt liu sy cho nn khng i hi phigianhittcnhnsylnnhitqucao.Cngcngnguynldch chuyn m t bn trong nhn ra ngoi b mt vt liu sy nhng c th d dng nhn thy rng, i vi phng php sy nng tc nhn sy nhit cao s lm khbmtvtliunhanhhndoscntrqutrnhdchchuynm.Hn na, cc vt liu sy khc nhau c cu trc t bo v thnh phn ha l khc nhau, vic s dng phng php sy lnh chng ta c th xy dng quy trnh cng ngh iviccloirauqukhcnhau.Bitonthitkmhnhmysylnhs dng bm nhit sy C rt c thc hin xc nh cc thng s qu trnh t thc nghim. Nguyn l hot ng ca thit b Mysylnhhotngdatrnnguynlcatsy,nhngtcnhnsy cxltchmtrckhivobungsy.Nguyntctchmtcnhnsy bng cch s dng dn lnh ca my lnh lm gim nhit ca tc nhn sy di nhit im sng hi nc trong khng kh m ngng t thnh nc Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh69 SVTH: Bi Vn Vnh v c ly ra ngoi. Phn tc nhn sy sau khi tch m c gia nhit li bi dn nng ca my lnh rii tip tc a vo bung sy thc hin qu trnh sy. Khngkhngoi tritrngthiO(t0, 0) caquadnlnh.Khimy hot ngmicht lnhcmynn nn ln dnngng t sau i quavan tit lu ri v dn lnh trao i nhit vi khng kh ngoi tri c ht vo, qu trnhlmlnhlmchokhngkhlnhtrnnbohancngngtthotra ngoi, lc ny khng kh ngoi tri c nhit l t2 trng thi 2, sau tc nhn sy tip tc i qua dn nng, nng nhit tc nhn ln n nhit t3 trng thi 3. Tc nhn sy ny sau c dn qua cc khay vt liu sy thc hin qu trnh sy tch m ng nhit. Qu trnh sy sau tip tc vi lng tc nhn hi lu cha m vt liu sy. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh70 SVTH: Bi Vn Vnh Hnh 4.1 S nguyn l h thng v th qu trnh sy 4.2 Xy dng quy trnh cng ngh sy hnh 4.2.1. Gii thiu vt liu sy Vng nguyn liuHnh l l loi gia v, khng th thiu trong cc ba n hng ngy, mc d vn u t v cng lao ng cao hn cc loi rau gia v khc, nhng vn t hiu qu kinh t cao.Hnh thn tho, cy sng lu nm, c mi c bit. C 5-6 l, l hnh tr rng, di 30-50 cm, pha gc l phnh to, trn u thun nhn. Hoa t mc trn ng hnh tr, rng. Hoa t dng hnh xim, c ngn thnh hnh tn gi trng ta hnh cu. Qu nang, trn. Hnh c trng khp ni, ch yu l lm gia v. ng thi hnh cng l mt v thuc nam c dng cha nhiu loi bnh: thuc ho, tr m, li tiu, st trng... Hnh l l loi rau mu c bit l hnh kh, gia v ny v ang c b con cc tnh nh Hi Dng vng ng Bng Sng Hng v b con BSCL c bit l tnh Vnh Long trng vi din tch kh ln. Nu nh trc y loi cy Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh71 SVTH: Bi Vn Vnh trng ny ch sn xutri rc mt vi ni, th nay c trng nhiu a phng. Thm ch cn hnh thnh nhng vng chuyn canh ln. Vi gi tr kinh t cao hin nay hnh ang c thu mua vi s lng ln dng ph v nhu cu trong nc v xut khu ra cc th trng ln nh Trung Quc, i Loan c bit l Nht vi s lng ln. c im v thnh phn ha hc ca hnh Hnh ta tn khoa hc l Allium fistilosum Linn, thuc h Liliaceae. Hnh ta l mt loi c sng nhiu nm, cao khong 50cm, c mi c bit. Tp hnh mu trng hoc hi nu nu, khng phnh ln. L gm 5- 6 l, 3 cnh phidi,hnhtr,phntrn,rng,di30-50cmngknh48mm,pha gia phnh ln, u thun nhn. Trc pht hoa cao bng l. Tn hnh cu, 1 2 l hoa, trng, mng. Phin hoa trng, 5mm, c sc xanh, qu nang, hnh trn, ng knh chng 6mm. Ht hnh 3 cnh mu en. Tinh du c mi c bit. Khng nh hnh ty v ti, thnh phn ha hc cahnhtatcnghincusurng.TronghnhtaclcAlliin (allylcystein sulfoxide) ging nh trong ti, nhng t hn. Alliin khi b thy gii bng iu t alliinnase clora Allicin, acid pyruvic v amonia (xem thnh phn ha hc ca ti). Allicin l mt cht khng an nh nn d b thy gii v phng thch allyl bisulfide, c mi c bit. 4.2.2. Xy dng quy trnh cng ngh sy Hnh Chn nhng bi hnh tng i ng u, ng tui, sinh trng tt, khng b nhim su bnh. Ra sch v ro nc trc khi sy Hnh sau khi ra c thi mng ty thuc vo yu cu ca khch hang sau triu trn khaysymbosaocho qu trnhtraoinhitilu ti u nht.Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh72 SVTH: Bi Vn Vnh Hnhchanhiuvitaminvchtdinhdngnnkhngthtinhnhsy nhitcao.ThngthngkhongnhitthchhpsyHnhtrong khong 40 -600C[3].Ta c s cng ngh sy c rt nh sau: Hnh ti u vo ( m 92%) Ra sch v ro nc Phn loi hnh Thi mng theo yu cu Xp hnh vo thnh tng khay Sy ( nhit 40-60oC) theo phng php sy lnh n m yu cu (3 - 8%) ng gi bo qun Hnh 4.2. S cng ngh sy C rt 4.3 Xc nh cc thng s u vo ca vt liu a) Thnh phn dinh dng ca vt liu sy Gitrdinhdngvthnhphnhahctrong100ghnhl:Nng lng 32,1Kcal 1%, Carbohydrates 7,34g 6%,Protein1,83g3%,Tngs cht bo 0,3g 3% , Cht x 2,6g 7% . Vitamin : Folates 64 g 16% , Niacin 0.525 mg 3% , Pantothenic acid 0.075 mg 1.5% , Pyridoxine 0.61 mg 5% , Riboflavin 0.080 mg6%,Thiamin0.055mg5%,VitaminA997IU33%,VitaminC18.8mg 31% Vitamin E 0.55 mg 4% , Vitamin K 207 g 172% . Electrolytes:Sodium16mg 1% , Potassium 276 mg 6% . Minerals : Calcium 72 mg 7 % , Copper 0.083 mg 9%,Iron1.48mg18.5%,Magnesium20mg5%,Manganese0.160mg7%, Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh73 SVTH: Bi Vn Vnh Phosphorus 37 mg 5% , Selenium 0.6 g 1% , Zinc 0.39mg3.5%.Phyto-nutrients: Carotene- 598 g , Crypto-xanthin- 0 g,Lutein-zeaxanthin 1137 g. b) Xc nh kch thc vt liuSdngthckpcchnhxcl0,05mmcthangot 0,054100mm.Kchthcbanulkchthclnnhtcacclthnhthi mng c kch thc 3 5 mm c) Xcnh m ca vt liu sy m l mt thng s k thut quan trng v lm c s cho qu trnh sy. Cncvomuvcuimchngticthtnhcthigiansyl thuytcngnhthigianboqun. mucahnhcxcnhbng phng php t sy d) Phng php xc nh mu, mi Bng cch nh gi cm quan ca nhiu ngi v mu sc ca nguyn liu u vo v sn phm. e) La chn ch sy i vi rau qu ni chung cng nhHnh ni ring nhit syyu cu khng qu cao. Thng thng i vi cc loi rau qu nhit sy khng qu60OC,vnucaohncthlmtnthngccthnhphnvitamin,chtdinh dng v mu sc trong sn phm dn n lm gim gi thnh sn phm. y ta tnh ton theo hai ch sy khc nhau,mt l ch syhi lu hon ton tc nhn sy v ch thi b tc nhn sy. 4.4 Tnh ton l thuyt ch sy hi lu hon ton Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh74 SVTH: Bi Vn Vnh Mc ch tnh ton nhit ca qu trnh l xc nh tiu hao khng kh dng cho qu trnh sy L, kg/h v tiu hao nhit Q, kJ/h. Trn c s tnh ton nhit xc nhcckchthccbncathitb.ngthiquavicthitlpcnbng nhit, cn bng nng lng ca h thng s xc nh c hiu sut s dng nhit v hiu sut s dng nng lng ca h thng cng nh tiu hao nhit ring ca bung sy v h thng. My sy lnh da trn nguyn l ca t sy, nhng tc nhn sy c x l tch m trc khi i vo bung sy. Nguyn tctch m tc nhn sy dng dn lnhcamylnhlmgimnhitcatcnhnsydinhitim sng bc hi nc trong khng kh m ngng t thnh nc v ly ra ngoi. Phn tc nhn sy sau khi tch m c gia nhit li bi dn nng ca my lnh ri tip tc a vo bung sy thc hin qu trnh sy.C s ca phng php ny c thc hin bng cch gim m tng i trong khng kh to ra s chnh lch p sut gia hi nc trong khng kh vhinctrongnngsn,thcphm.Bngcchnymstchrakhi nng sn, thc phm, v i vo khng kh. Khi lm lnh khng kh trong thit b trao i nhit xung thp hn nhit ng sng, hi bo ho m s ngng t v tch ra khi khng kh. Khng kh sau i qua dn nng s sy kh vt liu. Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh75 SVTH: Bi Vn Vnh Hnh 4-3. S nguyn l bm nhit s dng trong h thng sy lnh Trng hp tc nhn sy hi lu hon tonKiu sy hi lu hon ton s dng Heat pump dryer, tc nhn sy sau kh i qua bung sy (trng thi 3 c qut ht tr v theo ng ng hi lu, sau qua dn lnh gim nhit n nhit t4 (trng thi 4) v n nhit t1 (trng thi 1), ti y lng nc ngng t s c dn ra ngoi. Tc nhn sy sau khi tch m tip tc i qua dn nng, nng nhit ln t2 (trng thi 2), ri i qua bung sy, thc hin qu trnh sy. Qu trnh sy l thuyt c trnh by trn gin I-d nh sau: Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh76 SVTH: Bi Vn Vnh Hnh 4-4. th I-d ch sy hi lu hon ton 1-2:Qutrnhgianhittcnhnsynnhitsy.im(2)ltrng thi khng kh nng trc khi vo bung sy. 2-3: Qu trnh sy ng nhit, tc nhn sy c m thp c thi qua vt liu sy s nhn m thot ra t vt liu v mang ra khi bung sy. 3-4: Qu trnh lm lnh tc nhn sy n nhit ng sng. im (3) l trngthikhngkhsaukhiiquabungsychiluhonton,im (4) trng thi khng kh trong thit b bay hi, lc bt u gim m. 4-1: Qu trnh tch m. im (1) l trng thi khng kh cui giai on tch m.4.4.1 Xc inh cc im nt trn th sy a)im(Mi trng bn ngoi) *Nhit t0= 260C c chn theo nhit trung bnh ca khu vc Thnh Ph Nha Trang. [Theo kt qu thc nghim chng 4] * m tng i 0 = 81% [Theo kt qu thc nghim chng 4] *Phn p sut hi bo ha ca nc Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh77 SVTH: Bi Vn Vnh

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)*Dung m ca khng kh

(Ly gi tr Pa = 0,993 bar) *Entanpy ca khng kh mI0 = 1,0048.t0 + d0(2500 +1,842.t0) = 1,0048.26 + 0,028(2500 + 1,842.26)= 97,465 kJ/kg.kk *T cc thng s nhit v m khng kh ngoi tri, s dng th I-d ta xcnhcts=240C(TimO(260C,81%)dngngd=constct ng =100%, ta xc nh c ts) b) im: Trng thi khng kh sau dn nh *Nhit : t1 = 8 0C, theo [5] * m tng i v tc nhn sy n dn lnh ngng t m nn tc nhn sy trng thi bo ha nn chn 1= 100%. *Phn p sut bo ho

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)*Dung m ca khng kh

*Entanpi Thay cc thng s ca im 1 vo cng thc ta c: I1 = 1,0048.t1 + d1(2500 +1,842.t1)Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh78 SVTH: Bi Vn Vnh = 1,0048.8 + 0,00678.(2500 + 1,842.8) = 25,1 kJ/kgkk c)im 2 : Tc nhn sy c gia nhit (trng thi khng kh sau dn nng) *Nhit : t2 = 400C (Nhit ci t trong qu trnh sy) *Phn p sut bo ho

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)*Dung mDoqutrnh1-2lqutrnhgianhittcnhnsythngquadnnngca bmnhit nn : d1 = d2 = 0,00678 kg/kgkk *Entanpy : I2 = 1,0048.t2 + d2(2500 +1,842.t2) = 1,0048.40 + 0,00678.(2500 + 1,842.40) = 57,64kJ/kgkk * m tng i

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d) im 3 Vmtlthuytqutrnhsytrongphngphpsylnhlqutrnhng nhit,t2=t3=400C.Vi muraca tcnhn sysau khirakhi bung sy chn =15 %. *Phn p sut hi bo ha

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)*Dung m:

* EntanpyI3 = 1,0048.t3 + d3(2500 +1,842.t3)Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh79 SVTH: Bi Vn Vnh = 1,0048.40 + 0,011.(2500 + 1,842.40) = 68,5kJ/kgkk e)im 4 * m: 4= 100%. *Dung m: d4 = d3 = 0,011 kg/kgkk *Phn p sut bo ho Pb4 = ( )44 4aP .d0,621+d .= 0,993.0,011(0,621+0,011).1= 0,0173 bar *Nhit t4 = b44026,42-235,512-lnP = 4026, 42235,512 ln0, 0173 = 15,3 0C *Entanpi I4 = 1,0048.t4 + d4(2500 +1,842.t4)= 1,004.15,3 + 0,011(2500 + 1,842.15,3) = 43,2 kJ/kgkk 4.4.2 Tnh ton tc sy v thi gian sy Theo yu cu ca ti ta la chn vt liu sy lHnh, Cc thng s vt l ca Hnh. - m u vo 1 =92% [Xc nh bng thc nghim chng 4] - m cui2 = 3% - 5%. y ta chn m trung bnh ca sn phm 2

= 4%. [Xc nh bng thc nghim chng 4] -Khi lng ring

[Ph lc 6 /3/] Tcsyngtc:Sdngdngcotcgikhitinhnhthc nghim ta xc nh c vn tc tc nhn sy trong bung sy v = 3,1 m/s. Vn tc tc nhn sy v =3,1m/s < 5 m/s. Theo ti liu[1] ta c h s trao i nhit i lu:

Mt dng nhit [1] Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh80 SVTH: Bi Vn Vnh m 1 1b bJ = (t-t )Vi tm - nhit tc nhn sy, tm = 400C tb - nhit b mt vt liu tb=t = 270C [Xc nh da vo th I-d]

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Hay 893880 kj/m2h Cng bay hi m trn b mt vt iu 1b2bJJ =r r - nhit n ha hi (theo gi tr p sut) vi tb=270C. Ta c: P=0,04517bar.Ta c:r=2429 (kj/kg)

Tc sy ng tc [1] 20100bJUR= Vi: o - khi lng ring ca Hnh, o =n =944 (kg/m3) [Ph lc 6 /3/] R- phn na kch thc vt liu syTheo thc nghim kho st ly R=2 mm

Thi gian t nng vt iu [1] 200F R =a F0chun s Fure .-Xc nh chun s Bio nh s tng quan gia s trao i nhit trn b mt v tnh dn nhit ca n:

Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh81 SVTH: Bi Vn Vnh Vi:R - bn knh vt liu, m; - h s dn nhit ca vt liu, =0,35 W/mK; [Ph lc 6 /3/] qo- h s trao i nhit i lu; Theo ti liu [3]

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Vi: Uk - tc dng kh, m/s; k - khi lng ring khng kh ti nhit sy, kg/m3; R - bn knh vt liu xc nh t thc nghim, mm; - Chun s nhit Tuxc nh i lng t nng vt liu ti 1 im bt k: Tu=1okk-37,5-28= =0,9- 37,5-27tt Vi:tk -nhittrungbnhcatcnhnsytrongkhnggiansy,tk = tm=37,50C; ou- nhit vt liu a vo thit b sy, ou = to; u1 - nhit b mt bay hi ca vt liu, u1= t ; Tra theo th hnh 5.11 [Ti liu 3] ta tm c h s 00, 6 F ~ a - h s dn nhit ca vt liu: vaC= Trong:=0,35(w/m2K),=944(kg/m3),Cv=3,47(kJ/kgK)[Phlc6 /3/]

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Thi gian sy ng tc [1] Theo cng thc thc nghim Egorov [1] 1/21 2 cb100 =k +0,435.k .ln100-| | |\ . Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh82 SVTH: Bi Vn Vnh Vik1, k2 - hng s thc nghim v c on nh trong nhng khong m cn bng ht cb v m tng i khng kh . Vi m khng kh 0= 81% nm trong khong (80%< < 100%) ta c gi tr cc h s k1=4,5 v k2=30,5. Ta c:

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Vy thi gian sy ng tc dk kx1 - =U *d m ban u cu vt liu d = 92%

*kx m ti hn ca vt liu m

Thi gian sy gim tc [1] Vidk = 1150 % kx cb22k cb2 cb kx cb-2,3 = lnU -1 1 = + -= Trong :

Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh83 SVTH: Bi Vn Vnh

0,011h Tng thi gian sy: = 0 + 1 + 2 = 0,022 + 22,9 +0,11 = 22,9 (h) 4.4.3 Tnh ton nhit qu trnh a) Xc nh lng m bc hi Lp vt liu sy liu c b tr nm trn cc khay sy bng kim loi sao cho dng tc nhn sy c th d dng di qua b mt ca vt liu nhng ng thi phi m bo cho qu trnh truyn nhit v truyn m ca tc nhn sy din ra thun li nht. Qua thc t kho nghim khi tin hnh cc th nghim b tr vt liu trn 1 khay sy ta c khi lng vt liu sy G1 =100 kg/m *Lng m bc hi trong mt m sy

*Khi lng sn phm sau khi sy G2 = G1-W = 10091,66 =8,34 (kg/m) *Thi gian sy = 22,9 (h) theo kt qu tnh ton trn *Lng m bay hi trong 1 gi

b) Lng khng kh kh cn thit lm bay hi 1 kg m 03 21 1l = = =237 kgkk/kgad -d 0,011-0,00678 * Lu lng khng kh kh tun hon trong qu trnh sy Llt = W.l0 = 91,66.237 = 21723,42 kgkk/m c)Nhit lng dn nng cung cp cho qu trnh sy lm bay hi 1 kg m Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh84 SVTH: Bi Vn Vnh qlt = 2 13 2I -Id -d = 57,64-25,10,011-0,00678 = 7711 kJ/kga *Nhit lng dn nng cung cp sy 1 m Qlt = W.qlt = 91,66.7711 = 706790,26 kJ *Nng lng tiu hao cho qu trnh sy

*Lng m ngng t Adlt = d3 d2 = 0,011 0,00678 = 0,00422 kga d) Lng nhit thu c t ngng t 1kg m qll lt = l0.(I4 I1) = 237.(43,2 25,1) = 4289,7 J/kga *Lng nhit dn lnh thu c Qll lt = W.qll lt = 91,66.4289,7 = 393193,9kJ*Cng sut dn lnh ca qu trnh sy

4.5 Tnh ton l thuyt ch sy thi b tc nhn Vikiusykhnghilu,khngkhmitrng(trngthi0;(t0,0))c qut ht qua dn lnh gim nhit n nhit t1 (trng thi 1), v t2; ti y, lng nc ngng t s c dn ra ngoi. Tc nhn sy sau khi tch m tip tc iquabungsy,thchinqutrnhsyvthotrangoi(trngthi4).Qu trnh sy l thuyt c trnh by trn gin I-d nh sau: Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh85 SVTH: Bi Vn Vnh Hnh 4-5. th I-d ch sy thi b tc nhn 0-1 : Qu trnh lm lnh tc nhn sy n nhit ng sng. im (0) l trng thi khng kh iu kin mi trng, im (1) l trng thi khng kh trong thit b bay hi, lc bt u gim m. Khng kh ngoi mi trng c ht vo dn lnh kh m. 1-2: Qu trnh tch m. im (2) l trng thi khng kh cui giai on gim m trc khi i vo dn nng gia nhit. 2- 3: Qu trnh gia nhit tc nhn sy n nhit sy. im (3) l trng thi khng kh nng trc khi vo bung sy. 3-4: Qu trnh sy tc nhnsy c m thp c thi qua vt liu sy s nhnmthotratvtliuvmangrakhibungsy(qutrnhsyng nhit). im (4) l trng thi khng kh sau bung sy thi b ra mi trng.4.5.1. Xc nh cc thng s im nt a) im 0 (Trng thi khng kh mi trng): tng t ch hi lu hon ton. b) im 1: Trng thi khng kh trc u dn lnh Ta c d1 = d0 =0,028 kg/kgkk, 1=100%. * Phn p sut hi bo ha

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( ) Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh86 SVTH: Bi Vn Vnh * Nhit

* Entanpi I1 = 1,0048.t1 + d1(2500 +1,842.t1)= 1,004.30,3 + 0,028(2500 + 1,842.30,3) = 102 kJ/kgkk c) im 2 : Trng thi khng kh sau dn lnh (sau khi kh m) Ta c: 2=100%, t2= 80C * Phn p sut bo ho 2b24026,42 4026,42exp 12- =exp 12- =0,01072 bar235,5+t 235,5+8P =| || | | |\ .\ . * Dung m ca khng kh 2 b222 b2 a .P1.0, 01072d =0,621 0, 621 0, 00678 kg/kgkkP - .P 0, 993-1.0, 01072= =* Entanpi : Thay cc thng s ca im 2 vo cng thc ta c I2 = 1,0048.t2 + d2(2500 +1,842.t)= 1,0048.8 + 0,00678.(2500 + 1,842.8) = 25,1 kJ/kgkk d) im 3 : Tc nhn sy c gia nhit (trng thi khng kh sau dn nng) * Nhit : t3 = 400C * Phn p sut bo ho b334026,42 4026,42P =exp 12- =exp 12- =0,0731 bar235,5+t 235,5+40| || | | | |\ .\ . * Dung m: Do qu trnh 2-3 l qu trnh gia nhit tc nhn sy thng qua dn nng ca bm nhit nn : d2 = d3 = 0,00678 kg/kgkk * EntanpyI3 = 1,0048.t3 + d3(2500 +1,842.t3)Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh87 SVTH: Bi Vn Vnh = 1,0048.40 + 0,00678.(2500 + 1,842.40) = 57,64kJ/kgkk * m tng i ( )a 333b3P .d=0,621+d .P =( )0,993.0,006780,621+0,00678 .0,0731 = 0,147 = 14,7 % e) im 4 : Trng thi tc nhn sy thi ra ngoi Vmtlthuytqutrnhsytrong phng phpsylnhl qutrnhng nhit, t3=t4=40oC. m ca kh tc nhn sy sau khi qua bung sy 4=15% * Phn p sut hi bo ha 4b44026,42 4026,42P =exp 12- =exp 12- =0,0731 bar235,5+t 235,5+40| | | | ||\ . \ . * Dung m : 2 b222 b2 .P0,15.0,0731d =0,621 =0,621 =0,011 kg/kgkkP - .P 0,993-0,15.0,0731a * EntanpyI4 = 1,0048.t4 + d4(2500 +1,842.t4) = 1,0048.40 + 0,011.(2500 + 1,842.40) = 68,5kJ/kgkk 4.5.2 Xc nh nhit qu trnh a) Lng m bc hi trn mt m sy *Lng m bc hi trong mt m sy

*Khi lng sn phm sau khi sy G2 = G1-W = 10091,66 =8,34 (kg/m) *Thi gian sy = 22,9 (h) theo kt qu tnh ton trn *Lng m bay hi trong 1 gi Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh88 SVTH: Bi Vn Vnh

b) Lng khng kh kh cn thit lm bay hi 1 kg 4 301 1l = = =237 kgkk/kgad -d 0,011-0,00678 *Lu lng khng kh kh tun hon trong qu trnh sy Llt = W.l0 = 91,66.237 = 221723,42kgkk/m c) Nhit lng dn nng cung cp cho qu trnh sy lm bay hi 1 kg m qlt = 3 24 3I -Id -d=57,64-25,10,011-0,00678= 7711 kJ/kga *Nhit lng dn nng cung cp sy 1 m Qlt = W.qlt = 91,66.7711 = 706790,26 kJ *Cng sut dn nng qu trnh sy

*Lng m ngng t Adlt = d1 d2 = 0,028 0,00678 = 0,02122 kga d) Lng nhit thu c t ngng t 1kg m qll lt = l0.(I1 I2) = 237.(102 25,1) = 18225,3 J/kga *Lng nhit dn lnh thu c: Qll lt = W.qll lt = 91,66.18225,3 = 1670531kJ *Cng sut dn lnh qu trnh sy

4.6. Xc nh kch thc bung sy Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh89 SVTH: Bi Vn Vnh Cc kch thc c bn gm Chiu di L, chiu rng B, chiu cao H. Trong , chiu di L xc nh theo thi gian sy v nng sut sy. i vi thit b sy tng si chiu cao xc nh theo yu cu duy tr ch sy ng u v tn dng c ti a nhit ca mi cht. Qua qu trnh kho st nh my ta c cc thng s ca bung sy nh sau :LBH =222(m3) y cng l thng s ph hp vi yu cu ca qu trnh tnh toan : L thuyt :*Nng sut bung sy:G1 = 100 kg/m *Th tch hu dng : Vh = 1.m VGK , m3 Trong : m - Khi lng ring ca vt liu sy, m= 944 kg/m3 [Ph lc 6 /3/] KV - H s in y. KV = (0,40,5) [3]. Ta chn KV = 0,5 Thay vo ta tnh c

*Th tch ton b bung sy:V = Vh +AV, m3 Trong :AV -Th tch ca cc khong trng ca knh gi v cc khng gian t qut v cc thit b sy, m3. Theo kinh nghim ta chnAV= (30 40%)V [3].- Ta chnAV = 0,3.V = 0,3.0,21 = 0,064 m3 - Vy th tch bung sy l: V = 0,274 m3 Vi V tnh ton c, ta chn cc kch thc ca bung sy ph hp vi qu trnh o c thc t : Di Rng Cao l : LBH =222 (m3) 4.7. Cn bng nhit cho qu trnh Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh90 SVTH: Bi Vn Vnh Phng trnh cn bng nhit cho thit b sy: Q+Qbs+WCntm1+G2Cmtm1+LI1+Gvc.Cvctm1 =G2Cmtm2 +Q5+LI3+ Gvc.Cvc.tm2 Q + Qbs = L(I3 I1) + G2Cm(tm2 tm1) + Q5 WCn.tm1 + Gvc.Cvc.(tm2 tm1) Q + Qbs = Q2 + Qm + Q5 + Q1 + Qvc (*) Trong :*Q - Nhit lng cung cp gia nhit tc nhn sy *Qbs - Nhit lng b sung. Do khng dng thit b gia nhit cho khng kh sau dn nng nn Qbs = 0 *Q1 = - WCmtm1 - Nhit hu ch do m mang vo *G2Cm.(tm2 tm1) = Qm -Nhit lng tn tht do vt liu sy mang ra *Q5- Nhit tn tht ra mi trng theo kt cu bao che *Gvc.Cvc.(tm2 tm1) = Qvc- Nhit lng tn tht theo thit b vn chuyn *Q2 = L(I3 I1) - Nhit tn tht do tc nhn sy Chia 2 v (*) cho W v b qua Qbs

L, I 1 , d 1 G cv. C vc .t m2 Q 5 G 2 .C m .t m2 (G 2 C n +WC m ). t m1 THIT B SYQQ bs L, I 3' , d 3' G vc. C vc .t m1 53' 15 3' 1( )w w w w w( )vc vlvvc v vlQ Q Q Q Lq I I tCq l I I q q q tc= = + + + = + + + Khoa Cng Ngh Nhit Lnh n tt nghip GVHD: ThS. L Nh Chnh91 SVTH: Bi Vn Vnh