ti:Kho lnh bo qun ng 120 tn GVHD: Nguyn Tin CnhLI M UTrong nhng nm qua, ngnh k thut lnh nc ta c ng dng rt mnh m trong cc ngnh nh: sinh hc, ho cht, cng nghip dt, thuc l, bia, ru, in t, tin hc, y t, c bit trong ngnh ch bin v bo qun thy sn. Qu trnh chuyn i cng ngh ch bin p ng cc tiu chun quc t v thay i mi cht lnh mi to nn mt cuc cch mng tht s cho ngnh k thut nc ta. Vi ngun nguyn liu thy sn di do v a dng. Sn lng thy sn nh bt v nui trng hng nm l rt ln. V vy m bo thu c li nhun cao t vic xut khu thy sn th vic m bo cht lng ca sn phm l vn rt quan trng. Cng vi quy trnh cng ngh my mc v thit b ch bin th vn bo qun sau khi ch bin l mt khu khng th thiu hn ch nhng bin i lm gim cht lng sn phm. Cho nn vic xy dng kho bo qun sn phmng lnh l mt vn cp thit hin nay.Xut pht t nhng yu cu , c s phn cng ca thy Nguyn tin cnh, chng em c giao ti: Tnh ton thit k kho bo qun sn phm c ng lnh dung tch 120 tnTiu lun gm 7 chng nh sau:Chng 1: Tng quan.Chng 2: C s l thuyt tnh ton.Chng 3: Tnh ton kch thc kho lnh cn bng nhit.Chng 4: Tnh chiu dy cch nhit v kim tra ng sng.Chng 5: Tnh nhit ti, chn my nn v cc thit b ca h thng lnh.Chng 6: Cc thit b khc ca h thng.Chng 7: T ng ho v vn hnh h thng lnh. ti:Kho lnh bo qun ng 120 tn GVHD: Nguyn Tin CnhLI CM NSau mt thi gian nghin cu v tham kho hon thnh tiu lun, nhm chng em xin chn thnh cm n:Trng H Cng nghip TP. H Ch Minh to mi iu kin tt nht v c s vt cht k thut, trang thit b chng em c th hon thnh tt tiu lun trong thi gian ngn.Th vin trng cung cp nhng t liu ht sc c gi tr, l ti liu tham kho tt v qu bu.c bit gi li cm n n thy Nguyn Tin Cnh, ngi trc tip hng dn tn tnh chng em hon thnh tiu lun ng thi hn.TP. H Ch Minh, Ngy 05 thng 2 nm 2012 ti:Kho lnh bo qun ng 120 tn GVHD: Nguyn Tin CnhDANHSCHSINH VIN THC HIN STT H v tn MSSV1 Phan vn dng 101136812 Trnh hung dng 100723213 Trn th dng 100935214 o trng i 101282015 Nguyn thnh danh6 Nguyn nh duy 101330217 Nguyn hu ngc em 101004918 Phm c hin 102576919 Phm nh hip10 Nguyn trng hiu 1029903111 L nh hiu 1012321112 Trn ngc hip ti:Kho lnh bo qun ng 120 tn GVHD: Nguyn Tin CnhNHN XT CA GIO VIN HNG 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ti:Kho lnh bo qun ng 120 tn GVHD: Nguyn Tin Cnh............................................................................................................................................................................................................................................................................................................MC LCChng 1: TNG QUAN...................................................................................................11.1 ngha ca k thut lnh trong cng nghip thc phm..........................................11.2 Tng quan v cng ngh lm ng v bo qun sn phm ng lnh.......................11.2.1 Tc dng ca vic bo qun lnh.......................................................................11.2.2 Mt s bin i ca thc phm trong qu trnh bo qun ng........................21.3 Tng quan v kho lnh bo qun...............................................................................41.3.1 Kho lnh bo qun..............................................................................................41.3.2 Phn loi kho lnh..............................................................................................41.4 Tnh cp thit ca ti.............................................................................................6Chng 2: C S L THUYT TNH TON...............................................................82.1 Chn thng s thit k...............................................................................................82.1.1 Chn nhit bo qun......................................................................................82.1.2 m khng kh trong kho.................................................................................82.1.3 Thng s a l, kh tng Vng Tu...............................................................82.1.4 Phng n xy dng, v tr t kho lnh............................................................92.2 Xc nh din tch xy dng kho lnh.........................................................................122.2.1 Th tch cht ti ca bung lnh.......................................................................122.2.2 Din tch cht ti...............................................................................................122.2.3 Din tch xy dng ca bung lnh..................................................................122.3 Tnh chiu dy cch nhit v kim tra ng sng......................................................132.3.1 Tnh chiu dy cch nhit cch m.......................................................................132.3.2 Kim tra ng sng...........................................................................................132.4 Dng nhit tn tht vo kho lnh................................................................................142.4.1 Dng nhit qua kt cu bao che Q1...................................................................142.4.2 Dng nhit do sn phm v bao b ta ra Q2....................................................152.4.3 Dng nhit ta ra khi vn hnh Q4...................................................................162.5 Xc nh ph ti nhit qua thit b v my nn........................................................182.5.1 Ph ti nhit ca thit b...................................................................................18 ti:Kho lnh bo qun ng 120 tn GVHD: Nguyn Tin Cnh2.5.2 Ph ti nhit ca my nn.................................................................................18Chng 3: TNH TON KCH THC KHO LNH................................................193.1 Tnh th tch kho lnh..............................................................................................193.2 Din tch cht ti kho lnh.......................................................................................193.5 Din tch kho lnh cn xy dng.............................................................................203.6 Cu trc kho lnh.....................................................................................................203.6.1 Cu trc nn......................................................................................................203.6.2 Cu trc vch v trn kho lnh.........................................................................213.6.3 Cu trc mi kho lnh.......................................................................................223.6.4 Cu trc ca v mn chn kh..........................................................................22Chng 4: TNH CHIU DY CCH NHIT...............................................................254.1 Tnh chiu dy cch nhit...........................................................................................254.2 Kim tra ng sng trn b mt ngoi ca vch........................................................26Chng 5: TNH NHIT TI, CHN MY NN.......................................................275.1 Tnh ton nhit ti....................................................................................................275.1.1 Dng nhit qua kt cu bao che Q1...................................................................275.1.2 Dng nhit do sn phm v bao b ta ra Q2....................................................275.1.3 Dng nhit ta ra khi vn hnh Q4...................................................................275.2 Xc nh ph ti nhit qua thit b v my nn........................................................275.3 Chn h thng lnh..................................................................................................275.3.1 Chn phng php lm lnh..............................................................................95.3.2 Chn mi cht lnh...........................................................................................105.3.3 Cc thng s ca ch lm vic.....................................................................275.4 Chu trnh lnh..........................................................................................................275.4.1 Chn chu trnh lnh..........................................................................................275.4.2S v chu trnh biu din trn th lgp-i..................................................275.4.3 Tnh ton chu trnh hai cp bnh trung gian c ng xon................................275.5 Tnh chn my nn v thit b trao i nhit...........................................................275.5.1 Tnh ton my nn.............................................................................................275.5.2 Tnh ton thit b ngng t................................................................................345.5.3 Tnh chn my dn bay hi...............................................................................27Chng 6: CC THIT B KHC CA H THNG.................................................276.1 Bnh cha cao p......................................................................................................276.2 Bnh trung gian ng xon.........................................................................................276.3 Bnh tch du...........................................................................................................276.4 Bnh tch lng..........................................................................................................27 ti:Kho lnh bo qun ng 120 tn GVHD: Nguyn Tin Cnh6.5 Bnh tp trung du....................................................................................................276.6 Bnh tch kh khng ngng......................................................................................276.7 Thp gii nhit.........................................................................................................27Chng 7: T NG HA V VN HNH H THNG LNH............................277.1 Trang b t ng ho................................................................................................277.1.1 Trang b in ng lc......................................................................................277.1.2 Mch in iu khin........................................................................................277.2 Vn hnh h thng lnh...........................................................................................277.2.1 Chun b vn hnh............................................................................................277.2.2 Vn hnh...........................................................................................................277.2.3 Dng my..........................................................................................................277.2.4 S c ngp lng................................................................................................277.3 Bo dng h thng lnh.........................................................................................277.3.1 Bo dng my nn..........................................................................................277.3.2 Bo dng thit b ngng t.............................................................................277.3.3 Bo dng thit b bay hi................................................................................277.3.4 Bo dng van tit lu......................................................................................277.3.5 Bo dng thp gii nhit................................................................................277.3.6 Bo dng bm.................................................................................................277.3.7 Bo dng qut.................................................................................................27TI LIU THAM KHO...............................................................................................27Chng 1: TNG QUAN1.1 ngha ca k thut lnh trong cng nghip thc phm:1.1.1 Vai tr v nhim v:Ngun li thy sn nc ta v cng phong ph v a dng nh: c, tm, mc hin nay ngi ta xc nh trn 800 loi thy hi sn trong c hn 40 loi thy hi sn c gi tr cao. Nhu cu v thc phm thy sn ng lnh lun c xu hngtng nhanh c bit cc nc pht trin, mc sng ca h cao nn h c xu hng s dng cc loi thc phm thy sn hn ch nguy c gy mt s bnh nh :bnh tim, bnh bo ph, bnh cao huyt p, bnh bi c. Chnh v th m thc phm lnh ni chung v thc phm ng lnh ni ring lun l ngun hp dn ngi tiu dng trong v ngoi nc. N khng ngng mang li ngoi t cho t nc.1.1.2 ngha ca k thut lnh trong cng nghip thc phm:Xut pht t nhng vai tr v nhim v, mt khc Vit Nam nm vng nhit i nng m, phn ln cc loi thc phm t rau qu, tht, c cha nhiu cht v cu trc rt phc tp. cc thng s v cht lng thc phm thay i di tc dng ca cc qu trnh ln men trong thc phm cng nh cc qu trnh pht trin ca vi sinh vt v qu trnh xi ho ca khng kh lm tro thc phm c cu trc vi sinh vt b ph hu. Do lm gim gi tr ca thc phm. Mt khc thc phm nng c th xut hin nhiu cht c hi cho c th ngi.Vy hn ch nhng bin i khng c li c hi cho thc phm bng cch h nhit ca thc phm v nhit thp th nhng bin i c hi cho thc phm s b km hm lm cho qu trnh lu hn. Do , lm cho cht lng thc phm tng cao v thi gian gi c thc phm lu hn. Mun lm c iu ny th ngy nay bng cc phng php lm lnh nhn to m ngnh k thut lnh lm c v n cng l phng php t hiu qu cao trong cc iu kin nhit nh nc ta.1.2 Tng quan v cng ngh lm ng v bo qun sn phm ng lnh:1.2.1 Tc dng ca vic bo qun lnh:Bo qun thc phm l qu trnh bo v v hn ch nhng bin i v cht lng v hnh thc ca thc phm trong khi ch i a i s dng.Thc phm sau khi thu hoch v ch bin c bo qun nhit thp cng vi ch thng gi v m thch hp trong kho lnh, khi h nhit thp th enzyme v vi sinh vt trong nhin liu b c ch hot ng v c th b nh ch hot ng. Nh vy nguyn liu c gi ti lu thm mt thi gian na.Trang 1Ni chung khi nhit nh hn 10oC th vi sinh vt gy thi ra v vi khun gy bnh b kim ch phn no hot ng ca chng. Khi nhit nh hn 0oC th t l pht trin ca chng rt thp, -5oC -10oC th hu ht chng khng hot ng. Tuy nhin c mt s loi vi khun v nmmc khi h nhit xung -15oCchng vn pht trin c nh Cloromobacter, PseudomonasDo , mun bo qun c thc phm, nht lcc mt hng thu sn trong thi gian di th nhit bo qun phi di -15oC.Nh vy, qu trnh bo qun lnh c tc dng nh sau: + nhit thp cc phn ng sinh ho trong nguyn liu gim xung. Trong phm vi hot ng bnh thng c h 10oC th cc phn ng sinh ho gim xung 1/21/3, khi h xung thp s lm c ch cc hot ng v sinh l ca vi khun cng nh nm men. + Di tc dng ca nhit thp, nc trong ng vt thu sn b ng bng lm c th ng vt b mt nc, vi khun thiu nc nn gim pht trin v c khi cn b tiu dit. Ni chung khi nhit h xung thp th ch c tc dng kim ch vi khun hn l git cht chng.1.2.2 Mt s bin i ca thc phm trong qu trnh bo qun ng:a. Bin i vt l: S kt tinh li ca nc : i vi cc sn phm ng lnh trong qu trnh bo qun nu chng ta khng duy tr c nhit bo qun n nh s dn n s kt tinh li ca nc . l hin tng gy nn nhng nh hng xu cho sn phm bo qun. Do nng cht tan trong cc tinh th nc khc nhau th khc nhau, nn nhit kt tinh v nhit nng chy cng khc nhau.Khi nhit tng th cc tinh th nc c kch thc nh, c nhit nng chy thp s b tan ra trc tinh th c kch thc ln, nhit nng chy cao. Khi nhit h xung tr li th qu trnh kt tinh li xy ra, nhng chng li kt tinh th nc ln do lm cho kch thc tinh th nc ln ngy cng to ln. S tng v kch thc cc tinh th nc s nh hng xu n thc phm c th l cc cu trc t bo b ph v, khi s dng sn phm s mm hn, hao ph cht dinh dng tng do s mt nc t do tng lm mi v sn phm gim. trnh hin tng kt tinh li nc , trong qu trnh bo qun nhit bo qun phi c gi n nh, mc dao ng nhit cho php l 20C. S thng hoa ca nc :Trang 3Trong qu trnh bo qun sn phm ng lnh do hin tng hi nc trong khng kh ngng t thnh tuyt trn dn lnh lm cho lng m trong khng kh gim. iu dn n s chnhlchpsut bay hi ca nc b mt sn phm vi mi trngxung quanh. Kt qu l nc b thng hoa, hi nc i vo b mt sn phm vi mi trng khng kh. Nc b mt b thng hoa, sau cc lp bn trong ca thc phm cng b thng hoa. S thng hoa nc ca thc phm lm cho thc phm c cu trc xp, rng. Oxy khng kh d thm nhp vo oxy ho sn phm. S oxy ho xy ra lm cho sn phm hao ht v trng lng, cht tan, mi v b xu i, c bit trong qu trnh oxy ho lipit. trnh hin tng thng hoa nc ca sn phm th sn phm ng lnh em i bo qun cn c bao gi kn v ui ht khng kh ra ngoi. Nu c khng kh bn trong s xy ra hin tng ho tuyt trn b mt bao gi v qu trnh thng hoa vn xy ra.b. Bin i v ho hc:Trong qu trnh bo qun ng lnh cc bin i sinh ho, ho hc din ra chm. Cc thnh phn d b bin i l protin ho tan, lipit, vitamin, cht mu, S bin i ca protin: Trong cc loi protin th protin ho tan trong nc d b phn gii nht, s phn gii ch yu di dng di tc dng ca enzyme c sn trong thc phm. S khuch tn nc do kt tinh li v thng hoa nc gy nn s bin tnh ca protin ho tan. Bin i protin lm gim cht lng sn phm khi s dng. S bin i ca cht bo:Di tc ng ca enzyme ni tng lm cho cht bo b phn gii cng vi qu trnh thng hoa nc lm cho oxy xm nhp vo thc phm. l qu trnh thun li cho qu trnh oxy ho cht bo xy ra. Qu trnh oxy ho cht bo sinh ra cc cht c mi v xu lm gim gi tr s dng ca sn phm. Nhiu trng hp y l nguyn nhn chnh lm ht thi hn bo qun ca sn phm. Cc cht mu b oxy ho cng lm thay i mu sc ca thc phm. S bin i v vi sinh vt:i vi sn phm ng lnh c nhit thp hn -15oC v c bo qun n nh th s lng vi sinh vt gim theo thi gian bo qun. Ngc li nu sn phm lm ng khng u, v sinh khng ng tiu chun, nhit bo qun khng n nh s lm cho cc sn phm b ly nhim vi sinh vt, chng hot ng gy thi ra sn phm v gim cht lng sn phm.Trang 11.3 Tng quan v kho lnh bo qun:1.3.1 Kho lnh bo qun: Kho lnh bo qun l kho c s dng bo qun cc loi thc phm, nng sn, rau qu, cc sn phm ca cng nghip ho cht, cng nghip thc phm, cng nghip nh,Hin nay kho lnh c s dng rt rng ri trong cng nghip ch bin thc phm v chim mt t l ln nht. Cc dng mt hng bo qun bao gm: - Kho bo qun thc phm ch bin nh: tht, hi sn, hp,- Kho bo qun nng sn thc phm hoa qu.- Bo qun cc sn phm y t, dc liu. - Kho bo qun sa.- Kho bo qun v ln men bia.- Bo qun cc sn phm khc.Vic thit k kho lnh phi m bo mt s yu cu c bn sau:- Cn phi tiu chun ho cc kho lnh.- Cn phi p ng cc yu cu kht khe ca sn phm xut khu.- Cn c kh nng c gii ho cao trong cc khu bc d sp xp hng.- C gi tr kinh t: vn u t nh, c th s dng my v thit b trong nc,Vi nhng yu cu nhiu khi mu thun nhau nh trn ta phi a ra nhng phng php thit k vi hon cnh Vit Nam.1.3.2 Phn loi kho lnh:C nhiu kiu kho bo qun da trn nhng cn c phn loi khc nhau: a. Theo cng dng: Ngi ta c th phn ra cc loi kho lnh nh sau:- Kho lnh s b: dng lm lnh s b hay bo qun tm thi thc phm ti cc nh my ch bin trc khi chuyn sang mt khu ch bin khc.Trang 3- Kho ch bin: c s dng trong cc nh my ch bin v bo qun thc phm (nh my hp, nh my sa, nh my ch bin thu sn, nh my xut khu tht,). Cc kho lnh loi ny thng c dung tch ln, cn phi trang b h thng c cng sut lnh ln. Ph ti ca kho lnh lun thay i do phi xut nhp hng thng xuyn.- Kho phn phi, trung chuyn: dng iu ho cung cp thc phm cho cc khu dn c, thnh ph v d tr lu di. Kho lnh phn phi thng c dung tch ln, tr nhiu mt hng v c ngha rt ln i vi i sng sinh hot ca c mt cng ng.- Khothngnghip: kholnhboqunccmt hngthcphmcahthng thng nghip. Kho dng bo qun tm thi cc mt hng ang c doanh nghip bn trn th trng.- Kho vn ti (trn tu thu, tu ho, t): c im ca kho l dung tch ln, hng bo qun mang tnh tm thi vn chuyn t ni ny n ni khc.- Kho sinh hot: y l loi kho rt nh dng trong cc h gia nh, khch sn, nh hng dng bo qun mt lng hng nh.b. Theo nhit : Ngi ta c th chia ra:- Kho bo qun lnh: nhit bo qun nm trong khong -2oC n 5oC. i vi mt s rau qu nhit i cn bo qun nhit cao hn (i vi chui > 10oC, i vi chanh >4oC). Ni chung cc mt hng ch yu l rau qu v cc mt hng nng sn.- Kho bo qun ng: kho c s dng bo qun cc mt hng qua cp ng. l hng thc phm c ngun gc ng vt. Nhit bo qun tu thuc vo thi gian, loi thc phm bo qun. Tuy nhin nhit bo qun ti thiu cng phi t -18oC cc vi sinh vt khng th pht trin lm h hi thc phm trong qu trnh bo qun.- Kho a nng: nhit bo qun l -12oC, bung bo qun a nng thng c thit k -12oC nhng khi cn bo qun lnh c th a ln nhit bo qun 0oC hoc khi cn bo qun ng c th a xung nhit bo qun -18oC tu theo yu cu cng ngh. Khi cn c th s dng bung a nng gia lnh sn phm. Bung a nng thng c trang b dn qut nhng cng cth c trang b dn tng hoc dn trn i lu khngkh t nhin.- Kho gia lnh:c dng lm lnh sn phm t nhit mi trng xung nhit bo qun lnh hoc gia lnh s b cho nhng sn phm lnh ng trong phng php Trang 1kt ng 2 pha. Tu theo yu cu quy trnh cng ngh gia lnh, nhit bung c th h xung-5oC v nnglnvi trn nhit ng bng ca cc sn phm c gia lnh. Bung gia lnh thng c trang b dn qut tng tc gia lnh cho sn phm.- Kho bo qun nc : nhit ti thiu -4oC.c. Theo dung tch cha:Kch thc kho lnh ph thuc ch yu vo dung tch cha hng ca n. Do c im v kh nng cht ti cho mi loi thc phm khc nhau nn thng quy dung tch ra tn tht. V d: kho 50 tn tht, kho 100 tn tht, 200 tn tht, 500 tn tht.d. Theo c im cch nhit: Ngi ta chia ra: - Kho xy: l kho m kt cu l kin trc xy dng v bn trong ngi ta bc lp cch nhit. Kho xy chim din tch ln, gi thnh tng i cao, khng p, kh tho d, v di chuyn. Mt khc v mt thm m v v sinh kho xy khng m bo tt. V vy, hin nay nc ta thng t s dng kho xy bo qun thc phm.- Kho panel: c lp ghp t cc tm panel tin ch polyuretan v c lp ghp vi nhau bng cc mc kho cam locking v mng m dng. Kho panel c hnh thc p, gn v gi thnh tng i r, rt tin li khi lp t, tho d v bo qun cc mt hng thc phm, nng sn, thuc men, dc liu Hin nay nhiu doanh nghip nc ta sn xut cc tm panel cch nhit t tiu chun cao. V th hu ht cc x nghip, cng nghip thc phm u s dng kho panel bo qun hng ho.1.4 Tnh cp thit ca ti:Hin nay ngy cng c nhiu cc loi kho lnh khc nhau, phc v cho cc mc ch khc nhau ng gp mt phn khng nh vo vic bo qun, d tr v phn phi lng thc, thc phm mt cch hiu qu trn phm vi ton th gii. nc ta, nhu cu pht trin v kho lnh cng ngy cng tng cao, cc kho lnh c cng sut ln ngy cng c xy dng nhiu hn. Trc tnh hnh ny, nhm to cho sinh vin mt ci nhn tng th v vic tnh ton thit k mt kho lnh c bn, tm hiu v cc thit b ca kho lnh, cc ch tiu thit k ca tng loi kho lnh khc nhau... T gip cho sinh vin khi ra trng s khng b ng trc cc cng vic v tnh ton thit k mt kho lnh. Xut pht t nhng yu cu thc t trn nn chng em c phn cng tiu lun: Tnh ton thit k kho lnh bo qun sn phm c dung tch 120 tnTrang 2Chng 2: C S L THUYT TNH TON2.1 Chn thng s thit k:2.1.1 Chn nhit bo qun :Nhit bo qun sn phm ng theo l thuyt nhit cng thp th cht lng sn phm cng tt, thi gian bo qun cng lu nhng ty tng mt hng c th m chng c nhit bo qun khc nhau. Nu nhit bo qun cng thp th chi ph lnh cng cao, iu lm tng chi ph vn hnh v hiu qu kinh t t c thp. Nhit bo qun cn ph thuc vo thi gian bo qun, nu mun bo qun vi thi gian di th phi gi nhit thp.Nhit bo qun cc nc Chu u hin nay l -300C. Mt s sn phm bo qun nhit cao hn -300C nu bo qun trong thi gian ngn. Theo vin nghin cu lnh ng Quc t th nhit bo qun cho c gy l -200C, cho c bo l -300C. Tuy nhin nu c gy m bo qun trn 1 nm th nhit bo qun phi t -300C. Vit Nam hin nay, nhit bo qun sn phm thy sn ng lnh quy nh chung l -18 -250C.Kho ang thit k ca chng ta bo qun mt hng mc, bch tuc ng lnh thi gian bo qun thng nh hn 1 thng. V th, chng ta chn nhit bo qun trong kho l -200C.2.1.2 m khng kh trong kho: m khng kh lnh trong kho c nh hng ln n cht lng v cm quan b mt ca sn phm ng sau khi bo qun. Bi v n lin quan n hin tng thng hoa ca nc trong sn phm. Do vy ty tng loi sn phm c th m m ca khng kh trong kho l khc nhau.i vi sn phm ng khng c bao gi cch m th m khng kh lnh l phi t95%, cnivi snphmcbaogicchmthmcakhngkhlnh khong 85 90%.Kho ang thit k ch yu bo qun cc sn phm c c bao gi nn ta chn m khng kh lnh trong kho 90%.2.1.3 Thng s a l, kh tng TP. H Ch Minh:Cc thng s ny c thng k trong nhiu nm, khi tnh ton thit k m bo an ton cao ta thng ly gi tr cao nht ng vi ch kh hu khc nghit nht. T s m bo cho kho vn hnh an ton trong mi iu kin kh hu.Trang 1Bng 2-1: Thng s kh hu TP. H Ch Minh, ti liu tham kho [1].Bng nhit 0C m tng i, %TB c nm Ma h TB c nm Ma h TB c nm27 37,3 27 74 742.1.4 Phng n xy dng, v tr t kho lnh:C 2 phng n thit k kho lnh l kho xy v kho lp ghp. y, chng em chn thit k l kho lnh lp ghp, mc d kho lnh lp ghp gi thnh cao hn kh nhiu so vi kho lnh xy. Nhng n c nhng u im vt tri so vi kho lnh xy nh sau: tt c cc chi tit ca kho lnh lp ghp l cc panel tiu chun ch to sn nn c th vn chuyn d dng n ni lp rp mt cch nhanh chng trong mt vi ngy so vi kho truyn thng phi xy dng trong nhiu thng, c khi nhiu nm; c th tho lp v di chuyn n ni mi khi cn thit; cch nhit l polyuretan c h s dn nhit thp; hon ton c th sn xut c trong ncKho lnh nm gn khu thnh phm, bao gi thun li cho vic a hng vo trong kho v gim tn tht nhit cho kho. Ngoi ra cn phi nm v tr gn ng giao thng, c th li xe bc hng m khng nh hng n cc khu khc Sn phm sau khi cp ng c chuyn sang bao gi v chuyn vo kho lnh ngay, trnh trng hp phi vn chuyn xa c th lm cho sn phm b d ng v lm tng chi ph vn hnh ca kho lnh.2.1.5 Chn phng php lm lnh:Trong thc t c nhiu phng php lm lnh cho kho. Nhng c hai phng php thng dng nht l: lm lnh trc tip v lm lnh gin tip.Mi phng php u c nhng u nhc im khc nhau ph hp vi yu cu thit b, cng ngh ca tng trng hp c th. i vi mi trng hp ny ta s chn phng php lm lnh trc tip.Lm lnh trc tip:L phng php lm lnh kho bng dn bay hi t trong kho lnh, mi cht lnh lng si thu nhit ca mi trng cn lm lnh. Lm lnh trc tip c th l dn lnh i lu t nhin hoc i lu cng bc. u im:- Thit b n gin khng cn thm mt vng tun hon ph.- Tui th cao kinh t v khng phi tip xc vi nc mui l mt cht n mn kim loi rt nhanh chng.Trang 1- ng v mt nhit ng th t tn tht nng lng v hiu nhit gia kho lnh v dn bay hi gin tip qua khng kh.- Tn hao lnh khi khi ng nh ngha l khi lm lnh trc tip thi gian t khi m my n lc kho lnh t nhit yu cu s nhanh hn.- Nhit kho lnh c th gim st theo nhit si ca mi cht, nhit si c th xc nh d dng qua nhit k ca u ht my nn. Nhc im:- i vi h thng lnh ln th lng mi cht np vo my ln, kh nng r r ca mi cht ln, kh c kh nng d tm c ch r r x l. Tn tht p sup cho vic cp cho nhng dn bay hi xa c hi du v nu dng mi cht Freon, my nn d ht m, vic bo v my nn kh khn.- Tr lnh ca dn lnh trc tip km khi my lnh ngng hot ng th dn lnh cng ht lnh nhanh chng.2.1.6 Chn mi cht lnh:Mi cht lnh (cn gi l tc nhn lnh hay gas lnh) l cht mi gii s dng trong chu trnh nhit ng ngc chiu thu nhit ca mi trng c nhit thp v thi nhit ra mi trng c nhit cao hn. Mi cht tun hon trong h thng lnh nh qu trnh nn. my lnh nn hi, s thu nhit ca mi trng c nhit thp nh qu trnh bay hi nhit thp v p sut thp, s thi nhit cho mi trng c nhit cao nh qu trnh ngng t p sut cao v nhit cao, s tng p ca qu trnh nn hi v gim p.Mi cht lnh s dng trong h thng lnh cn p ng cc yu cu sau: Tnh cht ho hc:- Mi cht cn bn vng v mt ho hc trong phm vi p sut v nhit lm vic, khng c phn hu, khng c polyme ho.- Mi cht phi tr, khng n mn cc vt liu ch to my, du bi trn, oxy trong khng kh v hi m.- An ton, khng d chy d n. Tnh cht l hc:- p sut ngng t khng c qu cao, nu p sut ngng t qu cao bn chi tit yu cu ln, vch thit b dy, d r r mi cht.Trang 1- p sut bay hi khng c qu nh, phi ln hn p sut kh quyn h thng khng b chn khng, d r lt khng kh vo h thng.- Nhit ng c phi thp hn nhit bay hi nhiu v nhit ti hn phi cao hn nhit ngng t nhiu.- Nhit n ho hi (r) v nhit dung ring (c) ca mi cht lng cng ln cng tt. Nhit n ho hi cng ln, lng mi cht tun hon trong h thng cng nh, nng sut lnh ring khi lng cng ln. - Nng sut lnh ring th tch cng ln cng tt, my nn v thit b cng gn.- nht ng hc cng nh cng tt, gim tn tht p sut trn ng ng v ca van.- H s dn nhit v h s to nhit cng ln cng tt v thit b trao i nhit gn hn.- Mi cht ho tan du hon ton c u im hn so vi loi mi cht khng ho tan hoc ho tan mt phn v qu trnh bi trn tt hn, thit b trao i nhit khng b mt lp tr nhit do du bao ph, tuy cng c nhc im lm tng nhit bay hi, lm gim nht ca du.- Kh nng ho tan nc ca h thng cng ln cng tt trnh tc m b phn tit lu.- Khng c dn in c th s dng cho my nn kn v na kn. Tnh cht sinh l:- Mi cht khng c hi i vi ngi v c th sng, khng gy phn ng vi c quan h hp, khng to lp kh c khi tip xc vi la hn v vt liu ch to my.- Mi cht cn phi c mi c bit d dng pht hin khi b r r. C th pha thm cht c mi vo mi cht lnh nu cht khng nh hng n chu trnh my lnh.- Mi cht khng c nh hng xu n cht lng sn phm bo qun. Tnh kinh t:- Gi thnh phi h tuy tinh khit phi t yu cu.- D kim, ngha l mi cht c sn xut cng nghip, vn chuyn v bo qun d dng.Trang 1Khng c mi cht lnh l tng p ng y cc nhu cu nu trn, ta ch c th tm c mt mi cht p ng t hay nhiu nhng yu cu m thi. Tu tng trng hp ng dng c th chn loi mi cht ny hoc mi cht kia sao cho u im c pht huy cao nht v nhc im c hn ch n mc thp nht.Chng em quyt nh chn mi cht lnh s dng l R22 cho h thng kho lnh ca mnh do mi cht ny r tin, d kim, vn chuyn v bo qun d dng, nc ta sn xut c, t gy nh hng n tng zn v hiu ng nh knh nh.2.2 Xc nh din tch xy dng kho lnh:2.2.1 Th tch cht ti ca bung lnh:Theo cng thc (2.1) ca [1], ta c cng thc xc nh th tch cht ti bung lnh:V=vEg (m3) (2.1)Trong :E Dung tch ca cc bung lnh, tn. gv Mc cht ti, tn/m3.2.2.2 Din tch cht ti:Theo cng thc (2.2) ca [1], ta c cng thc xc nh din tch cht ti bung lnh:F = Vh (m2) (2.2)Trong :h Chiu cao cht ti, m.2.2.3 Din tch xy dng ca bung lnh :Theo cng thc (2.3) ca [1], ta c cng thc xc nh din tch xy dng bung lnh:2( )xdFFF m(2.3)Trong : F H s s dng din tch xy dng ca kho lnh. F ph thuc vo kch thc ca bung lnh.Trang 3i vi bung din tch nh hn 100 m2, F = 0,700,75, [1].i vi bung din tch 100- 400 m2, F = 0,750,80, [1].i vi bung din tch hn 400 m2, F = 0,80,85, [1].2.3 Tnh chiu dy cch nhit v kim tra ng sng:2.3.1 Tnh chiu dy cch nhit cch m:Theo cng thc (3.2) ca [2], chiu dy cch nhit cch m c xc nh bng cng thc:[ ] )1 1(11 2 1+ + ni iiCN CNK (2.4)Trong : CN dy yu cu lp cch nhit, m.CN H s dn nhit ca vt liu cch nhit, W/mK.K H s truyn nhit qua kt cu bao che, W/m2K.1 H s ta nhit ca mi trng bn ngoi ti vch, W/m2K. 2 H s ta nhit ca vch bung lnh vo bung lnh, W/m2K.i B dy lp vt liu th i, m.i H s dn nhit ca lp vt liu th i, W/mK.Trang 32.3.2 Kim tra ng sng:iu kin vch ngoi khng b ng sng l Kth KsTrong : Kth H s truyn nhit thc, W/m2K. Ks H s truyn nhit ng sng, W/m2K.Theo cng thc (3.7) ca [2], Ks c xcnh bng cng thc:111 20, 95.sst tKt t, W/m2K. (2.5)Trong : 1 H s ta nhit ca mi trng bn ngoi b mt tng kho, W/m2K.t1 Nhit khng kh bn ngoi kho, 0C.t2 Nhit khng kh bn trong kho, 0C.ts Nhit im ng sng, 0C.2.4 Dng nhit tn tht vo kho lnh: Theo cng thc (2.4) ca [1], nhit ti Q ca kho lnh s c tnh theo cng thc sau:Q = Q1 + Q2 + Q3 + Q4 + Q5, W (2.6)Trong : Q1 Dng nhit i qua kt cu bao che ca kho lnh, W.Q2 Dng nhit do sn phm v bao b ta ra trong qu trnh x l lnh, W.Q3 Dng nhit t khng kh bn ngoi do thng gi bung lnh, y Q3 = 0 do kho bo qun sn phm thy sn khng thng gi bung lnh.Q4 Dng nhit t cc ngun khc nhau khi vn hnh kho lnh, W.Q5 Dng nhit t sn phm ta ra khi sn phm h hp, n ch c kho lnh Trang 1bo qun rau qu, Q5 = 0.2.4.1 Dng nhit qua kt cu bao che Q1:Theo cng thc (2.5) ca [1], dng nhit Q1 c xc nh theo cng thc:Q1 = Q11 + Q12, W. (2.7)Trong : Q11 Dng nhit qua tng bao, trn v nn do chnh lch nhit , W.Q12 Dng nhit qua tng bao v trn do nh hng ca bc x mt tri, W.Theo cng thc (2.6) ca [1], dng nhit qua tng bao, trn v nn do chnh lnh nhit Q11 c xc nh theo cng thc: Q11 = Kt . F(t1 t2), W. (2.8)Trong : Kt H s truyn nhit thc ca kt cu bao che xc nh theo chiu di cch nhit thc.F Din tch b mt kt cu bao che, m2.t1 Nhit mi trng bn ngoi kho, 0C.t2 Nhit khng kh trong kho, 0C.2.4.2 Dng nhit do sn phm v bao b ta ra Q2:Theo cng thc (2.11) ca [1], dng nhit do bao b v sn phm to ra xc nh theo cng thc:Q2 = Q21 + Q22, W. (2.9)Trong : Q21 Dng nhit do sn phm ta ra, W.Q22 Dng nhit do bao b ta ra, W.Theo cng thc (2.12) ca [1], dng nhit do sn phm to ra xc nh theo cng thc:Trang 23600 . 241000) (2 1 21i i M Q , W. (2.10)Trong : M Cng sut bung gia lnh hay khi lng hng nhp vo kho bo qun trong mt ngy m, tn/ngy m. M chim c 10 15% dung tch kho lnh.i1, i2 Enthalpy ca sn phm vo kho v ca sn phm nhit bo qun, J/kgK.Theo cng thc (2.14) ca [1], dng nhit do bao b to ra xc nh theo cng thc:22 1 21000. ( )24.3600b bQ M C t t , W. (2.11)Trong : Mb Khi lng bao b a vo cng sn phm trong mt ngy m, tn/ngy m.Cb Nhit dung ring ca bao b, J/kgK.t1, t2 Nhit bao b trc v sau khi lm lnh bao b, 0C.2.4.3 Dng nhit ta ra khi vn hnh Q4:Theo cng thc (2.17) ca [1], dng nhit to ra khi vn hnh xc nh theo cng thc:Q4 = Q41 + Q42 + Q43 + Q44 + Q45, W. (2.12)a. Dng nhit do chiu sng Q41: Theo cng thc (2.18) ca [1], dng nhit to ra do n chiu sng xc nh theo cng thc:Q41 = A.F, W. (2.13)Trong :A Nhit lng ta ra khi chiu sng 1 m2 bung hay nn, W/m2.F Din tch ca bung, m2.Trang 2b. Dng nhit do ngi trong bung lm vic ta ra Q42: Theo cng thc (2.19) ca [1], dng nhit do ngi trong bung lm vic to ra xc nh theo cng thc:Q42 = 350. n, W. (2.14)Trong :350 Nhit lng do mt ngi ta ra trong khi lm cng vic nng nhc 350 W/ngi.n S ngi lm vic trong bung. N ph thuc vo cng ngh gia cng, ch bin, vn chuyn, bc xp. c. Dng nhit do ng c in ta ra Q43: Theo cng thc (2.20) ca [1], dng nhit do ng c in to ra c xc nh theo cng thc:Q43 = N.1000, W. (2.15)Trong :N Cng sut in ca ng c, kW.d. Dng nhit do m ca kho lnh Q44:Theo cng thc (2.22) ca [1], dng nhit do m ca kho lnh c tnh bng cng thc: Q44 = B.F, W. (2.16)Trong : F Din tch ca kho lnh, m2.B Dng nhit dung ring khi m ca, W/m2.e. Dng nhit do x bng dn lnh Q45:Theo cng thc (2.27) ca [1], dng nhit do x bng dn lnh c tnh bng cng thc:45. . .24.3600kk pkkV C tQ n , W. (2.17)Trang 1Trong :N S ln x bng trong mt ngy m.KK Khi lng ring ca khng kh, KK=1,2kg/m3.V Th tch ca kho lnh, m3.CPkk Nhit dung ring ca khng kh, CPkk =1009 J/kgK.t tng nhit khng kh trong kho lnh sau khi x bng dn lnh. 2.5 Xc nh ph ti nhit qua thit b v my nn:2.5.1 Ph ti nhit ca thit b:Theo cng thc (2.31) ca [1], ti nhit ca thit b Q0TB c ly bng tng ca tt c cc tn tht nhit ca kho lnh:Q0TB = Q1 + Q2 + Q4, W. (2.18)2.5.2 Ph ti nhit ca my nn:Theo [1], ti nhit ca my nn QMN i vi kho lnh bo qun sn phm thy sn ng lnh c tnh theo cng thc:QMN = 85%Q1 + 100%Q2 + 75%Q4(2.19)Theo cng thc (2.34) ca [1], nng sut lnh ca my nn i vi mi nhm bung c nhit si ging nhau xc nh theo biu thc:0.MNk QQb , kW. (2.20)Trong :b - H s thi gian lm vic ca my nn.k - H s lnh tnh n tn tht trn ng ng v thit b ca h thng lnhTrang 1Chng 3: TNH TON KCH THC KHO LNH3.1 Tnh th tch kho lnh:Th tch kho lnh c xc nh theo cng thc (2.1):V=Egv=120 0.45=266,66 m3Trong : E Dung tch kho lnh, E = 120 tn.gv nh mc cht ti, tn/m3. Kho c thit k vi mt hng c ng lnh cha trong thng cactong, ta c gv = 0,45 tn/m3, [1].3.2 Din tch cht ti kho lnh:Din tch cht ti kho lanh c xc nh theo cng thc (2.2): F=Vh=266,66 284=0.93 m2Trong : F Din tch cht ti hoc din tch hng chim trc tip, m2.h Chiu cao cht ti, m.Chiu cao cht ti l chiu cao l hng cht trong kho, chiu cao ny ph thuc vo bao b ng hng, phng tin bc d. Chiu cao h c th tnh bng chiu cao bung lnh tr i phn lp t dn lnh treo trn v khong khng gian cn thit cht hng v d hng. Chiu cao cht ti ph thuc vo chiu cao thc t h1ca kho.Chiu cao h1 c xc nh bng chiu cao ph b ca kho lnh tr i hai ln chiu dy cch nhit ca trn v nn kho lnh: h1 = H 2, m;+ Chn chiu cao ph b H = 3,6 m l chiu di ln nht ca tm panel.+ Chn chiu dy cch nhit = 80 mm.Suy ra: h1 = 3,6 2.0,08 = 3,44 m.Chiu cao cht ti thc h ca kho bng chiu cao ph b tr i khong h pha trn lu thng khng kh chn l 0,5m v pha di nn lt tm palet l: 0,1m.Trang 1Suy ra: h = 3,44 (0,1 + 0,5) = 2,84 m.3.3 Din tch kho lnh cn xy dng:Din tch kho lnh thc t cn xy dng phi tnh n ng i, khong h gia cc l hng, din tch lp t dn lnh, khong cch gia cc l hng n tng bao. V vy din tch cn xy dng phi ln hn din tch tnh ton trn v c xc nh theo cng thc (2.3):xdFF 391, 236F 489, 0450,8 m2Vi din tch kho lnh nh hn 400 m2, ta chn F= 0,8.T Fxd = 489,045 m2 ta quyt nh chn kch thc kho lnh nh sau:- Chiu rng kho: 18 tm panel x 1,2 m = 21,6 m- Chiu di kho: 19 tm panel x 1,2 m = 22,8 m.Nh vy din tch thc ca kho cn xy dng l 21,6 x 22,8 = 492,48 m2.3.4 Cu trc kho lnh:3.4.1 Cu trc nn:Cu trc nn kho ph thuc vo nhiu yu t nh: nhit trong kho, ti trng ca kho hng bo qun, dung tch kho lnh.Do c th ca kho lnh l bo qun hng ha do phi c cu trc vng chc, mng phi chu ti trng ca ton b kt cu xy dng, mng kho c xy dng ty thuc vo kt cu a chn ca ni xy dng. Do kho lnh xy dng theophng n lp ghp nn ton b kho c t trn nn nh xng. Ti trng ca hng bo qun s chi phi n rn chc ca nn, kh nng chu ln ca nn. Nu ti trng ca hng bo qun cng ln th cu trc nn kho lnh phi thit k c chu nn cao.Cc tm panel nn c t trn cc con ln thng gi.Cu trc nn kho lnh c thit k nh hnh v.Trang 3Hnh 3-1: Cu trc nn mng ca kho lnh, ti liu tham kho [7].Trang 1Lp ct m cht Tm panel Lp gch th ch Lp b tng 1x2Lp b tng 4x6Lp t t nhinTrang 1Mi kho lnh c nhim v bo v cho kho trc nhng bin i ca thi tit nh: nng, ma, c bit l gim bc x nhit ca mt tri vo kho lnh.Mi kho m bo che ma che nng tt cho kho v h thng my lnh.Mi khng c ng nc, khng c thm nc. Mi dc v hai pha vi dc t nht l 2%.Kho ang thit k c mi bng tn mu xanh l cy, h thng khung bng st v cc x nng c t theo chiu ngang ca kho, cc tr chng l cc tr st cao 4m c din tch 200x100mm Trang 140m 20m1215 m1,5 mTrang 11-lp mi tn2-khung bng stHnh 3-3: Cu trc mi kho lnh, ti liu tham kho [7].3.4.4 Cu trc ca v mn chn kh:Hin nay c cc loi ca nh sau: ca bn l, ca lc v ca la. Cu trc ca l cc tm cch nhit c bn l t ng, xung quanh c m kn bng cao su hnh nhiu ngn. Kha ca m c c hai pha trong v ngoi. Xung quanh ca c b tr dy in tr si ca phng bng dnh cht ca li. Cc ca c kch thc nh sau:+ Kch thc ca ln: 1980 x 980 mm.+ Kch thc ca nh: 680 x 680 mm.Hnh 3-4: Ca ra vo kho lnh, ti liu tham kho [7].Bn trong ca c b tr mn chn kh lm bng nha do hn ch dng nhit tn tht do m ca khi xut nhp hng.Nha ch to mn chn kh phi m bo kh nng chu lnh tt v c bn cao. Mn c ghp t cc di nha c chiu rng 200 mm, dy 2 mm, chng m ln nhau l 50 mm.Trang 2Mn nha, dy 2mm, rng 200mmMn nha ca ra voHnh 3-5: Mn nha che ca ra vo v ca xut nhp hng kho lnh, ti liu tham kho [7].Trang 1Chng 4: TNH CHIU DY CCH NHIT V KIM TRA NG SNG4.1 Tnh chiu dy cch nhit:Vic tnh ton cch nhit, cch m cho kho bo qun ng nhm mc ch: - Hn ch dng nhit truyn t bn ngoi qua kt cu bao che vo kho lnh.- Trnh ngng m trn b mt ngoi ca vch vo trong kho lnh.Chiu dy cch nhit c tnh theo cng thc (2.4):[ ] )1 1(11 2 1+ + ni iiCN CNK , mm.Do trn kho c mi che v nn kho lnh c con ln thng gi nn ta ly h s truyn nhit ca nn v trn kho bng h s truyn nhit ca vch kho. V vy ta xc nh chiu dy cch nhit chung cho c tng, trn v nn. y ta chn vt liu cch nhit cho kho l cc tm panel tiu chun (panel c tc dng cch nhit, cch m).Bng 4-1: Thng s lp vt liu tm panel tiu chun, ti liu tham kho [1].Vt liu Chiu dy, m H s dn nhit, W/mKPolyurethaneCN(0,018 0,023)Tn l 0,0006 45,36Sn bo v 0,0005 0,291Nhit khng kh trong kho tb = -200C, khng kh trong kho i lu cng bc va phi. ChnCN = 0,018 W/mK. K = 0,21 W/m2K.121 W/m2K; 92 W/m2K.Thay s:Trang 1[ ]1 1 2.0, 0006 2.0, 0005 10, 018 ( ) 0, 082 820, 21 21 45, 36 0, 291 9CNm mm + + + .Ta chn chiu dy panel tiu chun: 80panelTCmm .Khi chiu dy cch nhit thc ca panel l: 0, 08 (2.0, 0006 2.0, 0005) 0, 0778CNthucm + .H s truyn nhit thc ca vch khi l:10, 2221 2.0, 0006 2.0, 0005 0, 0778 121 45, 36 0, 291 0, 018 9thK + + + + W/m2K.(4.1)4.2 Kim tra ng sng trn b mt ngoi ca vch:iu kin vch ngoi khng b ng sng l Kth KsTrong : Kth H s truyn nhit thc, Kth = 0,222 W/m2K. Ks H s truyn nhit ng sng, c tnh theo cng thc (2.5):111 237, 3 31, 80, 95. 0, 95.21 1, 9137, 3 ( 20)sst tKt t W/m2K.Trong : 1 H s ta nhit ca mi trng bn ngoi b mt tng kho, W/m2K.t1 Nhit khng kh bn ngoi kho, 0C.t2 Nhit khng kh bn trong kho, 0C.ts Nhit im ng sng, 0C.Trang 2Cc thng s kh tng TP.H Ch Minh: t = 37,30C, 74% . Tra th i-d ca khng kh m ta c: ts = 31,80C.Nhn xt: Ks > Kt. V vy vch ngoi kho lnh khng b ng sng.Trang 2Chng 5: TNH NHIT TI, CHN MY NN V CC THIT B CA H THNG LNH5.1 Tnh ton nhit ti:Vic tnh ton nhit ti kho lnh l tnh ton cc dng nhit t mi trng xp nhp vo kho lnh. y chnh l dng nhit tn tht m my lnh phi c cng sut thi n tr li mi trng nng, m bo s chnh lch nhit n nh gia bung lnh v khng kh bn ngoi. Mc ch cui cng ca vic tnh ton nhit ti kho lnh l xc nh nng sut lnh ca my lnh cn lp t. Nhit ti Q ca kho lnh s c tnh theo cng thc (2.6):Q = Q1 + Q2 + Q3 + Q4 + Q5, WTrong : Q1 Dng nhit i qua kt cu bao che ca kho lnh, W.Q2 Dng nhit do sn phm v bao b ta ra trong qu trnh x l lnh, W.Q3 Dng nhit t khng kh bn ngoi do thng gi bung lnh, y Q3= 0 do kho bo qun sn phm thy sn khng thng gi bung lnh.Q4 Dng nhit t cc ngun khc nhau khi vn hnh kho lnh, W.Q5 Dng nhit t sn phm ta ra khi sn phm h hp, n ch c kho lnh bo qun rau qu, Q5 = 0.5.1.1 Dng nhit qua kt cu bao che Q1:Dng nhit qua kt cu bao che l tng cc dng nhit tn tht qua tng bao, trn v nn do s chnh lch nhit gia mi trng bn ngoi v bn trong kho lnh cng vi dng nhit tn tht do bc x mt tri qua tng bao v trn. Dng nhit Q1 c xc nh theo cng thc (2.7):Q1 = Q11 + Q12, W.Trong : Q11 Dng nhit qua tng bao, trn v nn do chnh lch nhit .Q12 Dng nhit qua tng bao v trn do nh hng ca bc x mt tri.Trang 1Kho lnh c thit k vch v trn kho u c tng bao v mi che nn b qua dng nhit qua tng v trn do nh hng ca bc x mt tri, Q12 = 0.Dng nhit qua tng bao, trn v nn do chnh lch nhit c xc nh theo biu thc (2.8):Q11 = Kt . F(t1 t2), W.Trong : Kt H s truyn nhit thc ca kt cu bao che xc nh theo chiu di cch nhit thc.F Din tch b mt kt cu bao che, m2.t1 Nhit mi trng bn ngoi kho, 0C.t2 Nhit khng kh trong kho, 0C.Chiu di kho: L1 = 22,8 m.Chiu rng kho: L2 = 21,6 m.Chiu cao: H = 3,6 + 0,08 = 3,68 m.Bng 5-1: Bng tng hp dng nhit xm nhp qua kt cu bao che.Bao cheKt(W/m2K)F(m2)t (0C)Qi(W)Vch pha ng 0,222 79,488 46 811,73Vch pha ty 0,222 79,488 46 811,73Vch pha nam 0,222 83,904 46 856,82Vch pha bc 0,222 83,904 46 856,82Trn 0,222 492,48 55 6013,2Nn 0,222 492,48 46 5029,2Tng Q1114379,48Do kho lnh c t trong xng ch bin c tng bao xung quanh v c mi che nn nhit khng kh xung quanh kho lnh s ly bng nhit ca khu thnh phm, t1 = 260C.Ch c trn kho lnh c nhit cao hn ta ly nhit khng kh pha trn trn l 350C.Trang 1Vy dng nhit xm nhp qua kt cu bao che l Q1 = Q11 = 14379,48 W.5.1.2 Dng nhit do sn phm v bao b ta ra Q2:Dng nhit do bao b v sn phm to ra xc nh theo cng thc (2.9):Q2 = Q21 + Q22, WTrong : Q21 Dng nhit do sn phm ta ra, W.Q22 Dng nhit do bao b ta ra, W.a. Dng nhit do sn phm ta ra Q21:c xc nh theo cng thc (2.10):3600 . 241000) (2 1 21i i M Q , W.Trong : M Cng sut bung gia lnh hay khi lng hng nhp vo kho bo qun trong mt ngy m, tn/ngy m. M chim c 10 15% dung tch kho lnh. i vi kho lnh 500 tn, ta chn lM = 50 tn/ngy m.i1, i2 Enthalpy ca sn phm vo kho v ca sn phm nhit bo qun, J/kg. Vi sn phm c ng lnh -120C, tra bng ti liu [1], ta c i1 = 24400 J/kg, i2 = 0.Vi kho bo qun ng, cc sn phm khi a vo kho bo qun c cp ng n nhit bo qun. Tuy nhin trong qu trnh x l ng gi v vn chuyn nhit sn phm tng ln t nhiu nn i vi sn phm bo qun ng ly nhit vo l: t1 = -120C, [1].Thay s: 21100050.(24400 0) 14120, 3724.3600Q W.b. Dng nhit do bao b ta ra Q22:c xc nh theo biu thc (2.11):Trang 222 1 21000 1000. ( ) 15.1460(26 20) 1166024.3600 24.3600b bQ M C t t + W.Trong : MbKhi lng baob a vo cngsnphmtrong mt ngym, tn/ngym. Ta ly Mb = 30% . M = 15 tn/ngy m, [1].Cb Nhit dung ring ca bao b, J/kgK, vi bao b l ba cc tng th Cb= 1460 J/kgK, [1].t1, t2 Nhit bao b trc v sau khi lm lnh bao b, 0C.Ta ly nhit bao b trc khi a vo kho cng sn phm bng nhit ca khu thnh phm, t1 = 260C.Vy: Q2 = Q21 + Q22 = 14120,37 + 11660 = 25780,37 W.5.1.3 Dng nhit ta ra khi vn hnh Q4:Cc dng nhit do vn hnh bao gm cc dng nhit do n chiu sng Q41, do ngi lm vic trong bung Q42, do cc ng c in Q43, do m ca kho lnh Q44 v dng nhit do x bng dn lnh Q45. Theo cng thc (2.12), ta c:Q4 = Q41 + Q42 + Q43 + Q44 + Q45, W.a. Dng nhit do chiu sng Q41: c xc nh theo biu thc (2.13):Q41 = A.F = 492,48 . 1,2 = 591 W.Trong :A Nhit lng ta ra khi chiu sng 1 m2bung hay nn, vi bung bo qun ng A = 1,2 W/m2, [1].F Din tch ca bung, m2.b. Dng nhit do ngi trong bung lm vic ta ra Q42: c xc nh theo biu thc (2.14):Q42 = 350 . n = 350 . 10 = 3500 W.Trong :Trang 3350 Nhit lng do mt ngi ta ra trong khi lm cng vic nng nhc 350 W/ngi, [1].n S ngi lm vic trong bung. N ph thuc vo cng ngh gia cng, ch bin, vn chuyn, bc xp. Kho c thit k vi phng thc bc d s dng nhn cng, ta chn s ngi lm vic trong kho l 10 ngi.c. Dng nhit do ng c in ta ra Q43: y do cha bit c cc ng c in hot ng trong kho nn ta chn theo gi tr nh hng trong ti liu [1] cho. Kho ca chng ta l kho bo qun ng nn ta chn Q43 = 12 kW.d. Dng nhit do m ca kho lnh Q44:c xc nh theo biu thc (2.16):Q44 = B.F = 4,8 . 492,48 = 2363,9 W.Trong : F Din tch ca kho lnh, m2.B Dng nhit ring khi m ca, W/m2.Dng nhit khi m ca ph thuc vo din tch bung v chiu cao bung.i vi chiu cao bung 6 m ta c bng sau:Bng 5-2: Dng nhit ring khi m ca, ti liu tham kho [1].Tn bungB, W/m2< 50 m250 150 m2> 150 m2Bo qun ng 22 12 8Vi chiu cao bung h = 3,6 m, din tch > 150 m2. S dng phng php ni suy ta c B = 4,8 W/m2.e. Dng nhit do x bng dn lnh Q45:Sau khi x bng, nhit kho lnh tng ln ng k, iu chng t c mt phn nhit lng dng x bng trao i nhit vi khng kh v cc thit b trong phng. Nhit dng x bng i b phn lm tan bng trn dn lnh v c a ra ngoi cng vi nc tan, mt phn truyn cho khng kh v cc thit b trong kho lnh gy nn tn tht. xc nh dng nhit do x bng dn lnh ta xc nh theomc tng nhit khng kh trong phng sau khi x bng. Mc tng nhit ca phng ph thuc vo dung Trang 1tch ca kho lnh.Thng thng nhit khng kh sau khi x bng tng (4 7) 0C.Dung tch cng ln th tng nhit cng nh v ngc li. Dng nhit do x bng dn lnh Q45 c xc nh theo biu thc (2.17):45. . .1, 2.492, 48.3, 6.1009.54. 49724.3600 24.3600kk pkkV C tQ n W.Trong :n S ln x bng trong mt ngy m, chn n = 4.KK Khi lng ring ca khng kh, KK=1,2kg/m3.V Th tch ca kho lnh, m3.CPkk Nhit dung ring ca khng kh, CPkk =1009 J/kgK.t tng nhit khng kh trong kho lnh sau khi x bng dn lnh (ly theo kinh nghim), lyt =50C, [1].Bng 5-3: Tnh ton dng nhit tn tht do vn hnh.Q41, W Q42, W Q43, W Q44, W Q45, W Q4, W591 3500 12000 2363,9 497 18951,9Bng 5-4: Tng hp cc kt qu tnh ton nhit ti kho lnh.Q1, W Q2, W Q4, W Q, W14379,48 25780,37 18951,9 59111,755.2 Xc nh ph ti nhit qua thit b v my nn:5.2.1 Ph ti nhit:a. Ph ti nhit ca thit b:Ph ti nhit ca thit b l ti nhit dng tnh ton b mt trao i nhit cn thit ca thit b bay hi. Cng sut gii nhit yu cu ca thit b bao gi cng ln hn cng sut Trang 1ca my nn, phi c h s d tr nhm trnh nhng bin ng c th xy ra trong qu trnh vn hnh. V th ti nhit ca thit b c ly bng tng ca tt c cc tn tht nhit ca kho lnh, theo cng thc (2.18), ta c:Q0TB = Q1 + Q2 + Q4 = 59111,75 W.b. Ph ti nhit ca my nn:Do cc tn tht trong cc kho lnh khng ng thi xy ra nn cng sut nhit yu cu thc t s nh hn tng ca cc tn tht nhit. trnh cho my nn c cng sut lnh qu ln, ti nhit my nn cng c tnh ton t cc ti nhit thnh phn nhng ty theo tng loi kho lnh c th ch ly mt phn tng ca nhit ti .Theo cng thc (2.19), ph ti nhit my nn c xc nh theo cng thc:QMN = 85%Q1 + 100%Q2 + 75%Q4 = 52,22 kW.Nng sut lnh ca my nn i vi mi nhm bung c nhit si ging nhau xc nh theo biu thc (2.2):0.1, 065.52, 2261,80, 9MNk QQb kW.Trong :b - H s thi gian lm vic ca my nn, thng ly b = 0,9(my nn lm vic 22 gi/ngy do x bng dn lnh v gim ti cho my nn), [1].k - H s lnh tnh n tn tht trn ng ng v thit b ca h thng lnh, n c xc inh theo bng sau:Bng 5-5: H s d tr k, ti liu tham kho [1].t0, 0C -40 -30 -10K 1,1 1,07 1,05S dng phng php ni suy vi t0 = -250C ta c k = 1,0655.3 Chn h thng lnh:5.3.1 Cc thng s ca ch lm vic:Vic chn cc thng s lm vic cho h thng lnh l rt quan trng v nu chn c mt ch lm vic hp l, ng n s em li hiu qu kinh t cao, nng sut lnh tng Trang 1trong khi in nng tiu tn t.Ch lm vic ca h thng lnh c c trng bng 2 thng s nhit sau:- Nhit si ca mi cht t0 (oC).- Nhit ngng t ca mi cht tk.a. Nhit si ca mi cht t0:Nhit si ca mi cht ph thuc vo nhit ca kho lnh bo qun. nhit si ca mi cht lnh dng tnh ton thit k c th ly nh sau:t0 = tb - t0 = -20 5= -25oC (5.1)Trong tb Nhit kho bo qun,0Ct0 Hiu nhit gia nhit si ca mi cht lnh v nhit khng kh trong kho. i vi dn lnh bay hi trc tip t0 = 5 13oC. Chn t0 = 5oC. b. Nhit ngng t tk:Nhit ngng t ph thuc vo nhit ca mi trng lm mt ca thit b ngng t. Do chn thit b ngng t lm mt bng nc nn:tk= 2 wt + tk = 38+ 4 = 420C (5.2)Trong : 2 wt Nhit nc ra khi bnh ngng,0Ctk Hiu nhit ngng t yu cu, thng ly t 3 5oC.Vic chn hiu nhit ngng t thc ra l bi ton ti u v kinh t gi thnh mt n v lnh l r nht. Nu hiu nhit ngng t nh, nhit ngng t s thp nng sut lnh tng, in nng tiu tn nh nhng tiu hao nc nhiu v gi thnh tiu tn nc tng. y ta chn tk = 5oC.Nhit nc ra khi bnh ngng c th xc nh theo cng thc:tw2= tw1 + tw = 33 + 5 = 380C(5.3)Trang 3Trong :tw1 Nhit nc vo bnh ngng. Ta thng ly nhit nc vo bnh ngng cao hn nhit nhit k t 340C. y nhit nhit k t ng vi thng s nhit ti TP. H Ch Minh l t = 300C. Vy dy tw1= t + 3 = 330Ctw Hiu nhit nc vo v ra bnh ngng, thng ly t 2 60C.Ta chn 05wt C 5.4 Chu trnh lnh:5.4.1 Chn chu trnh lnh:Ta c:t0 = -250C p0 = 2,01 Bar. tk =420C pk = 16,09 Bar. T s nn: 016, 0982, 01kpp < 9. y ta s dng chu trnh lnh l chu trnh kh. Chu trnh ny ph hp v c nhng u im r rt hn cc chu trnh khc:+ Chu trnh kh l chu trnh c hi ht v my nn l hi bo ha kh. +Chu trnhkhci tin v loi tr c cc nhc im cachutrnh Carnot phng va p thy lc. S dng van tit lu thay cho my dn n (Van tit lu c u im nh, gn, chi ph thp).+Chutrnhkhchaicimchnhlim1lunnmtrnngbohakh (thng b tr thit b tch lng gia my nn v thit b bay hi) v qu trnh tit lu c tn tht khng thun nghch vi nhit lng trc van tit lu bng nhit ngng t.5.4.2 S chu trnh v nguyn l hot ng:Trang 2MNNT TLHnh 5-1: Chu trnh 2 cp nn bnh trung gian c ng xon.+ Qu trnh 12 : l qu trnh p nn on nhit mi cht ( trng thi hi). Hi bo ha kh trng thi im 1 c my nn ht v v p nn on nhit ln n im 2. c im ca qu trnh c entanpi khng i S1 = S2 (hay S =0), nhit tng t t0 n tk, p Trang 1BHsut tng t P0 n Pk , v nhit t2 > tk . Qu trnh ny xy ra trong vng hi qu nhit.+ Qu trnh 23 : l qu trnh lm mt v ngng t ng p hi mi cht. Mi cht trao i nhit vi mi trng lm mt bng nc hoc khng kh .Sau , mi cht i vo bnh ngng t, c lm mt v h nhit xung ng bo ha kh (x = 1). Trong qu trnh ny, nhit th gim cn p sut khng i. Trong vng hi m mi cht chuyn t dng bo ha kh sang dng lng nh nc lm mt vi p sut khng i P2 = P3 = Pk.+ Qu trnh 34 : l qu trnh tit lu ng Enthalpy, mi cht lnh im 3 c tit lu n im 4, trong qu trnh tit lu ny mi cht c nhit v p sut t tk, Pkgim xung n nhit v p sut t0, P0. C c im : i3 = i4 v S4 > S3.+ Qu trnh 41 : l qu trnh bay hi ng p v ng nhit. Trong qu trnh ny mi cht nhn nhit ca mi trng cn lm lnh v bay hi nhit v p sut khng i.Sau , mi cht c my nn ht v qua bnh tch lng my nn khng ht phi lng, vng tun hon c khp kn v bt u vng tun hon mi.5.4.3 Tnh ton chu trnh :Xc nh cc thng s trng thi cc im nt ca chu trnh:Trang 22143lg pHnh 5-2: th lg P h chu trnh kh.im 1:Ta c p1= 2,01 Bar, t1 = -25oC, tra bng hi bo ho R22, trng thi hi Trang 1hbo ho, ta c i1 = 395,339 kJ/kg, s1 = 1,7935 kJ/kgK.im 3: Ta c p3 = 16,097 Bar, t3 = 42oC, tra bng hi bo ho R22, trng thi lng si, ta c i3 = 252,34 kJ/kg.im 2: V 1-2 l qu trnh nn on nhit nn s2 = s1 = 1,7935 kJ/kgK v p2 = p3 = 16,097 Bar. Tra bng hi qu nhit R22, ta xc nh c t2 = 77,5oC, i2 = 448,957 kJ/kg.im 4: Ta c p4 = 2,01 Bar, t4 = t1 = -25oC, i4 = i3 = 252,34 kJ/kg.Nng sut lnh ring q0:q0 = i1 i4 = 395,339 252,34 = 142,99 kJ/kg(5.4)Lng mi cht qua my nn m:0061,80, 432142,99Qmq kg/s(5.5)Cng nn ring l0:l0 = i2 i = 448,957 395,339 = 53,617 kJ/kg(5.6)Nhit thi ca thit b ngng t Qk:Qk = m.(i2 i3) = 0,432(448,957 252,34) = 84,972 kW(5.7)Cng nn on nhit:N = m.l0 = 0,432 . 53,617= 23,172 kW (5.8)H s lnh:061,82, 6623,172QN (5.9)5.5 Tnh chn my nn v thit b trao i nhit:5.5.1 Tnh chn my nn:Th tch ht thc t ca my nn:Vtt =mv1 =0,4320,111877 =0,0483m3/s (5.10) Trang 3Hiu sut ch th ca my nn:i = 00273 250, 0025. 0, 0025 ( 25)273 42kTtT+ + + = 0,72 (5.11)Cng sut ch th ca my nn:Ni = iN = 23,1720, 72 = 32,18 kW (5.12)Cng sut ma st ca my nn:Nms = Vtt ms = 0,0483 0,059.106 =2,85 kW (5.13)Cng sut hiu dng ca my nn:Ne = Ni + Nms= 32,18 + 2,85 =35,03 kW.(5.14)Hiu sut ng c my nn:el = eiNN= 32,1835, 03 =0,918.(5.15)Cng sut trn trc ng c :N 35, 031etdN = 35,03 kW (5.16)Cng sut tiu th in ca ng c :Nel

el tdeN .35, 03. 1 0, 918etd elN = 38,15 kW (5.17)Cng sut ng c in lp t:Nc = 1,2.Nel = 1,2 . 38,15 = 45,78 kW (5.18)Trang 1 Chn my nn:Qua vic tnh ton nhit ti kho lnh chng 5, ta xc nh c nhit ti ca my nn Q0 = 61,8 kW. y chnh l nng sut lnh m my nn cn phi t c bo m duy tr c nhit kho lnh iu kin thit k.Vi ch lm vic nh sau:+ My nn 1 cp+ Mi cht lnh R22+ Nhit ngng t tk = 420C+ Nhit si mi cht t0 = -250C+ Nng sut lnh 061, 8MNycQ kW.Tra ca ta l my nn ca hng MYCOM, ta chn my nn MYCOM 1 cp c k hiu F6WA2 vi cc thng s sau:Bng 5-7: Thng s k thutmy nn MYCOM F8WA2, ti liu tham kho [4].K hiuS xi lanhTc (v/ph)Th tch qut, (m3/h)Q0(kW)F6WA2 6 1450 280,7 76,1Trang 1Hnh 5-2: My nn MYCOM N42B, ngun ti liu tham kho s [7].5.5.2 Tnh chn thit b ngng t:Thit b ngng t trong h thng lnh l cc thit b trao i nhit b mt, trong mi cht lnh c p sut cao, nhit cao sau my nn c lm mt bng khng kh, nc hay cht lng nhit thp khc ngng t thnh lng. Qu trnh ngng t lun km theo hin tng ta nhit, ni cch khc nu khng c lm mt lin tc th qu trnh ngng t s dng li, mc ch bin hi mi cht lnh thnh lng cng khng thc hin c. Mt khc trong thit b ngng t nu p sut ca mi cht lnh khng thay i th nhit ngng t s gi khng i.Ch lm vic ca thit b ngng t trong h thng lnh cng c nh hng rt ln ti s lm vic v c tnh nng lng ca ton th h thng. Do b mt trao i nhit ca thit b khng th qu ln nn nhit ngng t tk trong my phi cao hn nhit mi trng xung quanh. Chnh tr s chnh lch nhit ny gy nn khng thun nghch bn ngoi v dn ti tn tht nng lng.Nh vy xut hin bi ton ti u v kinh t - k thut trong vic la chn thit b ngng t. Khi tng tr s chnh lch nhit th tn tht nng lng v chi ph vn hnh tng nhng b mt ca thit b ngng t li gim i, kt qu vn u t s gim. Ngc li nu chn thit b ngng t vi chnh lch nhit nh th tn tht nng lng nh, chi ph vn hnh gim nhng thit b li ln dn n vn u t ban u tng.Qu trnh ngng t mi cht amoniac l qu trnh ngng mng, do vy vic xc nh cng trao i nhit phi tnh ti nhit tr ca mng cht ngng. tng cng trao i nhit khi ngng t ta phi tm cch to ra dng chy ri, ph v v tch mng cht ngng khi b mt i Trang 1nhit. V vy vic p dng cc bin php gim bt tn tht thit b ngng t s em li hiu qu kinh t cao cho ton h thng.- Chn kiu thit b thit k v ch lm vic: y, chng ta chn thit b ngng t kiu ng chm v bc nm ngang s dng cho mi cht R22 gii nhit bng nc qua thp gii nhit vi cc ch lm vic l: Nhit nc vo bnh ngng tw1 = 330C Nhit nc ra bnh ngng tw2 = 380C Nhit ngng t ca mi cht tk = 420C- chnh lch nhit trung bnh gia mi cht lnh v mi trng lm mt: max minmaxmin9 46,19ln ln4tbt tt Ktt Vi :maxt - hiu nhit ln nht, maxt = tk tw1 = 42- 33 = 9Kmint - hiu nhit nh nht, mint = tk tw2 = 42 38 = 4K- Lu lng nc qua bnh ngng:84, 9724, 056. 4,19.5kp nQmC t kg/s = 4,088 . 10-3 m3/s. - Chn b mt truyn nhit ca bnh ngng l chm ng c cnh b tr so le trn mt sng c cc thng s nh sau:ng knh trong: dtr = 0,0132 m.ng knh chn cnh: dng = 0,0165 m.ng knh cnh: D = 0,021 m.Bc cnh: Sc = 0,002 m.Din tch mt ngoi ca 1 m ng : F = 0,149 m2/m.Din tch mt trong ca 1 m ng : Ftr = 0,0415 m2/m.Trang 2- H s lm cnh:6 , 30415 , 0149 , 0 trngFF - Chn vn tc nc gii nhit: w = 1,2 m/s.- S ng nc trong mt li:31 2 24. 4.4, 088.1024, 89.0, 0132 .1, 2trmnd Chn s ng trong 1 li l 25 ng, tc nc s l = 1,195 m/s.- Thng s vt l ca nc nhit trung bnh 35,50C:= 993 kg/m3= 0,6195 W/mKv = 0,7247.10-6 m2/s pr = 4,8505- Xc nh h s to nhit 2 t vch trong ca ng ti nc lm mt:Tr s Reynolds:6. 1,195.0, 0132Re 217660, 7247.10id y l ch chuyn ng chy ri, v th tr s Nu c dng:Nu = 0,021.Re0,8.Pr0,43 = 0,021.217660,8.4,85050,43 = 122,28- H s to nhit v pha nc:1. 122, 28.0, 61955738, 490, 0132iNud W/m2K.- Xc nh mt dng nhit pha trong ng (trng hp ny l pha nc) theo din tch pha trong ng (t b mt vch c nhit tv vo nc):Trang 1( )1 12302, 751 1v wtb tb vl tb vi ii it t t tq t t + + Trong : ii= 0,00026 l tng nhit tr dn nhit ca vch.Chn 0, 3v tbt t , t ta c:( )22302, 75 2302, 75.0, 7.6,1 9832, 77 /l tb vq t t W m - Cc ng c b tr trn mt sng theonh ca tam gic u, chm ng c dng hnh lc gic vi s ng t theo ng cho lc gic ln m xc nh theo cng thc:m = 0,75.( )31. . . /kiQq s d l DTrong :S - Bc ng ngang, s = 1,3.dc = 1,3.0,021 = 0,0273l/D - T s gia chiu di ng v ng knh trong ca thn, ly l/D = 8Vym = 3384, 972.100, 75 10, 819832, 77.0, 0273.0, 0132.8 chn m = 11 ngy chnh l s ng theo chiu ngang n2 = m = 11 ng- H s to nhit t pha mi cht ngng t tnh theo b mt trong ca ng 2 i vi hi R22 ta c:Trang 10,1672 3242. . .0, 72 . .. . 2a vn h gd t _ ,Trong :h - L hiu entanpi vo v ra ca R22 bnh ngng h = 196,617 kJ/kgThng s vt l ca mi cht lnh R22 khi ngng t nhit 42 0C:Cp = 1,317 kJ/kg.K = 0,0672 W/m.K =196.10-6 N.s/m2= 1122,4 kg/m3- H s tnh n iu kin ngng t khc nha trn cc phn ng v ngang ca b mt ngng tngnngngdcFFhdEFF+1]1

25 , 075 , 0. 3 , 1 Vi : 2Cos S 2) d D .(Fc2ng2d). ( 139 , 0235002 , 0 2) 0165 , 0 021 , 0 (22 2mCos (= 350 : gc u cnh)Fd, Fn : din tch b mt ng v ngang ca 1 m ng c cnh (m2/m).Fn = Fng Fd = 0,149 0,139 = 0,01 m2.Chiu cao qui c :) ( 0063 , 0021 , 00165 , 0 021 , 04 42 22 2mDd Dhcng c1]1

11]1

Chn E = 1. Vy :Trang 1609 , 1149 , 001 , 00063 , 00165 , 01149 , 00139 , 03 , 1 . 3 , 125 , 075 , 025 , 075 , 0 +1]1

+1]1

ngnngngdcFFhdEFF( )2 30,1670,2542 6196617.1122, 4 .0, 0672 .9,810, 72 . 5, 5 3, 6.1, 6 12171, 88196.10 .0, 0132.vvtt - Nh vy ta c h phng trnh:0,752 2. 12171, 87v vq t t ( )12302, 75 6,1vq t Gii h ta c 0, 9vt K, q = 11075,3 W/m2- Ta chn s ng theohng ngang ca ng cho ln l 11 trong lc gic u, vy tng s ng s l:n = 0,75.112 + 0,25 = 91 ng- S li ng i trong bnh: z= 91/25 = 4 li.- Din tch b mt truyn nhit tnh theo b mt trong ca ng:849727, 6711075, 3kQFq m2.- Chiu di ng trong bnh ngng:17, 672, 033,14.0, 0132.91Fld n m. Cu to v hot ng ca bnh ngng:Hi qu nhit t my nn c a vo bnh ngng theo ng ng 1 vo in y vo khng gian gia cc ng, ta nhit cho nc lm mt i trong ng thnh phn v ngng t li. Lng c ly ra pha di bnh ngng theo ng 2 v vo bnh cha cao p. Nhit Trang 1 nc vo v ra khi bnh ngng chnh lch khong 5 60C do trao i nhit vi hi mi cht.Hnh 5-3: Bnh ngng ng chm v bc nm ngang , ti liu tham kho [7]1- Hi t thit b ngng t2- Lng sau ngng t3- Ni van an ton4- p k5- Nc vo lm mt bnh ngng6- Nc ra khi bnh ngng7- ng cn bng p sut vi bnh ngngTrang 3125643878- Tch kh khng ngng5.5.3 Tnh chn thit b bay hi:Thit b bay hi c nhim v ha hi gas bo ha m sau tit lu ng thi lm lnh mitrng cn lm lnh. Nh vy cng vi thit b ngng t, my nn, thit b tit lu th thit b bay hi l mt trong nhng b phn quan trng khng th thiu trong h thng lnh. Qu trnh lm vic ca thit b bay hi nh hng ti thi gian v hiu qu lm lnh. V vy d h thng trang b tt n u nhng thit b bay hi lm vic km hiu qu th tt c tr nn v ch. Do cn chn thit b bay hi ph hp cho h thng, c din tch ph hp vi din tch yu cu lm vic.+ Nng sut lnh 061, 8DLQ kW+ Nhit bay hi t0 = -250C khng kh lnh t dn bay hi c th phn b ng u trn din tch ca kho, ta chn 4 dn lnh c kt cu v kch thc ging nhau cho kho tr. Vy nng sut lnh ca mi dn l: 15,45 kW. Tnh ton qu trnh lm lnh ca khng kh trong dn lnh:Hnh 5-4: th I d biu din qu trnh lm lnh ca khng kh trong dn lnhTi b mt ca dn lnh khng kh c nhit bng nhit ca b mt v tr thnh khng kh bo ha. Trng thi ca khng kh ra khi dn lnh l hn hp gia khng kh v khng kh bo ha nhit ca b mt.im V: trng thi khng kh vo dn lnh.im R: trng thi khng kh ra khi dn lnh.Trang 1im W: trng thi khng kh ti b mt dn lnh.Ba im ny iu nm trn mt ng thng c trng cho qu trnh lm lnh khng kh trong dn lnh.Gc nghing ca ng thng ny c biu th:tV Nhit khng kh khi vo dn lnh, oC.tR Nhit khng kh khi ra khi dn lnh, oC.tw Nhit khng kh ti b mt dn lnh, oC.Hiu nhit tR tV = 240C, chntR tV = 20C. duy tr nhit kho tr ng -200C, ta chn :tv = -190C; v = 90%tR = t1 2 = -210C; R = 95%tw= -220C ; w = 100%.+ Entanpi v cha hi ti im V:tv = -190C; v = 90%. Tra bng khng kh m, ta c :ik = -4,58 Kcal/kg = -4,58.4,187 = -19,17 kJ/kg.i = 0,5 Kcal/kg = 0,5.4,187 =2,09 kJ/kg.d= 0,00085 Kg/Kg.Vy:i = -19,17 + (0,92,09) = -17,28 kJ/kg.d = 0,90,00085 = 0,000765 Kg/Kg.+ Entanpi v cha hi ti im R:tR = t1 2 = -210C; R = 95%. Tra bng khng kh m, ta c ik = -5,06 Kcal/kg = -5,06.4,187 = -21,18 kJ/kg.i = 0,423 Kcal/kg = 0,423.4,187 =1,77 kJ/kg.d= 0,00072 Kg/Kg.Vy:i = -21,18 + (0,951,77) = -19,5 kJ/kg.d = 0,950,00072 = 0,000684 Kg/Kg.+ Entanpi v cha hi ti im W:tw= -220C ; w = 100%. Tra bng khng kh m, ta c ik = -5,3 Kcal/kg = -5,3.4,187 = -22,19 kJ/kg.i = 0,387 Kcal/kg = 0,387.4,187 =1,62 kJ/kg.d= 0,00066 Kg/Kg.Trang 1Vy:i = -22,19 + (11,62) = -20,57 kJ/kg.d = 10,00066 = 0,00066 Kg/Kg.Vy:000684 , 0 000765 , 05 , 19 28 , 172 12 1+ d di i= 27407. Tnh ton kt cu dn lnh:B mt truyn nhit ca dn bay hi c cu to l cc ng ng b tr song song v c cnh phng bng nhm lng vo ng ng.Chn :ng knh ngoi : dng = 0,014 mng knh trong : dtr = 0,012 mng knh cnh : dc = 0,068 mBc cnh : sc= 0,004 mB dy cnh : c = 0,0004 mBc ng ngang : s1= 0,045 mBc ng dc : s2= 0,045 mDin tch cnh ca 1m ng :Fc = 2 xcngsds s1422 111]1

= 2 x94 , 0004 , 014014 , 0045 , 0 045 , 02 1]1

(m2/m).Din tch khong cch gia cc cnh ca 1m ng :0396 , 0004 , 00004 , 01 014 , 0 101]1

1]1

ccngsd F (m2/m).Tng din tch mt ngoi c cnh ca 1m ng :98 , 0 0396 , 0 94 , 00 + + F F Fc ng (m2/m).Din tch b mt trong 1m ng :0377 , 0 012 , 0 tr trd F (m2/m).H s lm cnh :Trang 126 995 , 250377 , 098 , 0 trngFFH s ta nhit v pha khng kh i vi chm ng c cnh phng hnh ch nht:tkdNu .W/m2K.Vi tr s Nu: mtdndLC Nu1]1

. Re .- ng knh tng ng :) ( 0065 , 0) 0004 , 0 004 , 0 ( ) 014 , 0 004 , 0 () 0004 , 0 004 , 0 )( 014 , 0 045 , 0 (2) ( ) () )( (21ms d ss d sdc c ng cc c ngt d - Chn t s : 35 tddL.- Chiu di cnh theo chiu chuyn ng khng kh vung gc cc ng ng :2275 , 0 0065 , 0 35 35 tdd L (m).- Tr s Re :tdd .Re: nht ng hc.Chn vn tc khng kh = 4,5 m/s, lc = 11,79x10-6 m2/s.Vy : 228710 79 , 120065 , 0 5 , 4 .Re6 tdd- H s C c tnh theo cng thc C = A.BChn A = 0,1.B = 1,36 0,248111 , 01000Re Trang 2Vy C = 0,1 x 0,8111 = 0,0811- S m n = 0,45 + 0,00656775 , 0 tddL- S m m = -0,28 + 0,08 x 09704 , 01000Re - H s dn nhit (W/m.K) tra bng tnh cht vt l ca khng kh kh, ta c = 1,96 .10-2 kcal/m.h. = 1,96 .10-2 1,163 = 2,28 x 10-2 (W/m.K)Khi :mtdndLC Nu1]1

. Re . = 0, 6775 0,097040, 0811.2287 .35 10, 8274Vy h s ta nhit v pha khng kh:tkdNu . = 98 , 370065 , 010 28 , 2 8274 , 102 (W/m2K).H s ta nhit qui c :c tKqR R+ + .11 (W/m2K).H s tch m vi b mt truyn nhit tw < 0 th c xc nh nh sau:0923 , 121 190,000684 0,0007652280 1 2280 12 12 1+ + + t td d- tttRVi :t : b dy lp tuyt bm dn bay hi. Chn t = 0,001m.t : h s dn nhit ca lp tuyt. Chn t = 0,25 (W/m2.K).- Rc : Tr nhit ca s tip xc gia ng v cnh i vi dng cnh lng ng : Chn Rc = 4,5x10-3 (W/m2.K).Trang 3Vy :6 7 , 3 01 0 5 , 42 5 , 00 0 1 , 00 9 2 3 , 1 . 9 8 , 3 711.113 + ++ +c tKqR R (W/m2.K)Thng s m:c: h s dn nhit ca nhm. c = 1751,163=203,5 (W/m.K). 57 , 290004 , 0 5 , 203 )25 , 0001 , 00923 , 1 . 98 , 371(2. )..1(2 ++c c tKRm Chiu cao qui c ca cnh: h ) ln 35 , 0 1 ).( 1 .( . 5 , 0' + ngd h (m)- i vi cnh hnh vung := 1,5ngdB; - B = s1 = s2 = 0,045 (m) 696 , 3014 , 0045 , 015 , 1 0275 , 0 ) 696 , 3 ln 35 , 0 1 )( 1 696 , 3 ( 014 , 0 5 , 0 ) ln 35 , 0 1 ).( 1 .( . 5 , 0' + + ngd hm.i lng mh:mh=29,57.0.0275=0,813Hiu sut ca cnh :') 'mhmh ( thE Vi :th: tang hyperpol.Vy : Trang 181 , 0813 , 0) 813 , 0 ( (') ' thmhmh thE.H s ta nhit v pha khng kh qui chun dn theo b mt trong ng:1]1

+ tr0trcq qtrFFEFFVi : : h s khng u ca s truyn nhit theo chiu cao ng, = 0,85.Vy :72 , 5580377 , 00396 , 085 , 0 81 , 00377 , 094 , 067 , 3001]1

+ 1]1

+ tr trcq qtrFFEFF (W/m2.K).Mt dng nhit v pha khng kh qui i theo b mt trong ca ng :44 , 1117 ) 22 20 ( 72 , 558 ) ( + w kho qtr trt t q (W/m2.K)Din tch b mt truyn nhit :32'15, 45 1013, 821117, 44BHtrtrQF mq

Lu lng khng kh qua dn lnh :1 215, 456, 96( / )17, 28 19, 5BHkhQG kg si i +Th tch khng kh qua dn bay hi :6, 964, 991, 395khkhkhGV (m3/s)kh : khi lng ring ca khng kh -200C; kh = 1,395 (kg/m3).Din tch cho khng kh i qua :24, 991,114, 5khkhVf m Din tch b mt truyn nhit ca 1 ng ( khib tr cc cm ng dc theo chiu chuyn ng ca khng kh) :Trang 31]1

+ ccngtrkh trshd sdf F' '1'2Vi : h=027 , 02014 , 0 068 , 02ng cd d (m).' 2''10, 0121,11 1, 6332 0, 0004 0, 02720, 045 0, 0140, 004trtr khcngcdF f mhs ds 11 + + 11 ] ]S cm ng lm vic song song :'13, 828, 461, 633tntrFzF cm.Chn z = 8 cm.Tng chiu di 1 cm :'''11,1143, 352 0, 0004 0, 0272. .0, 045 (0, 014 )( )0, 004khcngcfLhs ds + + mS hng ng trong 1 cm ng :k sLm.1'Vi hwk w : chiu rng cm ng.h: chiu cao cm ng.Chn k = 1,93 '143, 3522, 34. 0, 045 1, 93Lms k hng ngChn s ng trong mt cm ng l 22.Trang 3Chiu di 1 ng trong 1 cm ng :'43, 351, 9722Ll mm ,chn l = 2 (m)Chiu di 8 cm ng :L = 8L = 8 x 43,35 = 346,8 (m).Th tch dn lnh:V = 1,05.L.4.2trd = 1,05.346,8.4012 , 0 .2= 0,041 m3.Chn dn bay hi: khng kh lnh t dn bay hi c th phn b ng u trn din tch ca kho, ta chn 4 dn lnh c kt cu v kch thc ging nhau cho kho tr. Vy nng sut lnh ca mi dn l: QoBH = 20Q= 61, 84 = 15,45 kW chn dn bay hi ta da vo nng sut lnh Q0BH. Din tch truyn nhit:160,8 m2. Nng sut lnh: 15,48kW. Kch thc :+ Chiu di :1,25 m.+ Chiu rng :1,82 m.+ Chiu cao :0,972 m Lu lng khng kh: 14400 m3/h. S qut gi: 2 qut. Cng sut qut gi: 4,4 kW.Chng 6: CC THIT B KHC CA H THNG6.1 Bnh cha cao p:6.1.1 Cng dng:Trang 3Bnh cha cao p c b tr ngay sau bnh ngng t, dng cha lng mi cht p sut cao, nhit cao gii phng b mt trao i nhit ca thit b ngng t, duy tr s cp lng lin tc cho van tit lu. N c t ngay di bnh ngng v c cn bng p sut vi bnh ngng bng cc ng cn bng hi v lng. N c tc dng cha ton b lng gas trong h thng khi cn sa cha bo dng.6.1.2 Cu to bnh cha cao p:Bnh cha cao pnmngang cho mi cht ammoniac l mt hnh tr nm ngang. Bnh cha cao p c thit k m bo p sut lm vic l 1,8 MPa. Trang 376895342110Cng dng chnh ca thit b lm mt trung gian l lm mt trung gian cc cp nn trong h thng lnh my nn nhiu cp. y ta s dng thit b lm mt trung gian l bnh trung gian t ng c ng xon rut g. Bnh trung gian c ng xon rut g ngoi vic s dng lm mt trung gian, bnh cn c th s dng :+ Tch du cho dng gas u y my nn cp 1.+ Tch lng cho gas ht v my nn cp 2.+ Qu lnh cho lng trc khi tit lu vo dn lnh nhm gim tn tht tit lu.Trang 36.2.2 Cu to bnh trung gian:Trang 13246115121314119710V1V2V1V25Hnh 6-2: Bnh trung gian ng xon, ti liu tham kho [7].Bnh trung gian c cu to hnh tr, c chn cao, bn trong bnh b tr ng xon lm lnh dch lng trc tit lu.Bnh c trang b hai cng tc phao khng ch mc dch, cc cng tc phao c ni vo ng gp 14 ly tn hiu.Cng tc phao trn V1 bo v mc dch cc i ca bnh, nhm ngn nga lng ht v my nn cao p. Khi mc lng trong bnh dng cao t mc cho php, cng tc phao tc ng ng van in t 3 cp dch vo bnh. Cng tc phao pha di V2 khng ch mc dch cc tiu nhm m bo cc ng xon lun ngp trong dch lng. Khi mc dch di h xung thp qu mc cho php, cng tc phao V2 tc ng m van in t cp dch cho bnh. Ngoi cng tc phao, bnh cn c trang b van an ton v ng h p sut lp pha trn thn bnh.6.2.3 Hot ng:Gas t my nn cp 1 n bnh c dn sc vo khi lng c nhit thp v trao i nhit mt cch nhanh chng.Phn cui ng y 2, ngi ta khoan nhiu l nh hi sc ra xung quanh u hn. Pha trn thn bnh c cc nn chn c tc dng chn khng cho lng ht ln pha trn trnh hin tng ht lng v ca my nn tm cao. Dng lng tit lu ha trn Trang 19 Hi lng10 X y, hi du11 Chn bnh 12 Tm b13 Thanh 14nggplpvan phao15 ng lp van an ton, p k1Hihtvmynn p cao2 Hi nn tm thp vo3 Tit lu vo4 Cch nhit bnh trung gian5 Nn chn6 Lng ra7 ng xon rut g8 Lng vovi hi qu nhit cuiqu trnh nn tm thp, trc khi da vo bnh. ng hi ht v my nn cp 2 c b tr nm pha trn cc nn chn.Bnh trung gian c bc cch nhit, bn ngoi cng bc lp tn bo v.Hnh 6-3: Bnh trung gian do cng ty SEAREE sn xut, ti liu tham kho [7].6.3 Bnh tch du:6.3.1 Cng dng:Cc my lnh khi lm vic lm vic cn phi tin hnh bi trn cc chi tit chuyn ng nhm gim ma st, tng tui th thit b. Trong qu trnh my nn lm vic du thng b cun theo mi cht lnh.Vic du b cun theo mi cht lnh c th gy ra cc hin tng:+ My nn thiu du, ch bi trn khng tt nn d chy, h hng.+ Du sau khi theo mi cht lnh s ng bm cc thit b trao i nhit nh thit b ngng t, thit b bay hi, lm gim hiu qu trao i nhit, nh hng chung n ch lm vic ca ton h thng. V vy tch lng du cun theo mi cht khi my nn lm vic, ngay trn u ra ca my nn ngi ta b tr bnh tch du. Lng u c tch ra s c a v bnh thu hi du. 6.3.2 Nguyn l lm vic:Nhm m bo tch trit du b cun theo mi cht lnh, bnh tch du c thit k theo nhiu nguyn l khc nhau nh sau: + Gim t ngt tc dng gas t tc cao (khong 18 25 m/s) xung tc thp 0,5 1m/s. Khi gim tc t ngt cc git du mt ng nng v ri xung.Trang 2+ Thay i hng chuyn ng ca dng mi cht mt cch t ngt. Dng mi cht a vao bnh khng theo phng thng m a ngot theo nhng gc nht nh.+ Dng cc tm chn hoc khi m ngn cc git du. Khi dng mi cht chuyn ng va vo cc vch chn, khi m cc git du b mt ng nng v ri xung.+ Lm mt dng mi cht xung 50 600C bng ng xon trao i nhit t trong bnh tch du.+ Sc hi nn c ln du vo mi cht lnh trng thi lng. y ta chn bnh tch du kiu nn chn. 6.3.3 Cu to v nguyn l hot ng ca bnh tch du:Trang 23451671 Hi vo2 Vnh gia cng3 Hi ra4 Nn chn trn5 - Ca hi x vo bnh6 Nn chn di7 - Du v bnh cha du2Hnh 6-4: Bnh tch du kiu nn chn, ti liu tham kho [7].Nguyn l tch du kt hp r ngot dng t ngt, gim tc dng v s dng cc nn chn. Dng hi t my nn n khi vo bnh r ngot 900, trong bnh tc dng gim t ngt xung khong 0,5 m/s, cc git du phn ln ri xung pha di bnh. Hi sau thot ln pha trn i qua cc l khoan nh trn cc tm chn. Cc git du cn ln s dc cc nn chn cn li. dng hi khi vo bnh khng sc tungte lng du c tch ra nm y bnh, pha di ngi ta b tr thm mt nn chn. Nn chn ny khng c khoan l nhng ch gn vo bnh c cc khong h du c th chy v pha di.Ngoi ra ngoi cui ng dn hi bt kn khng x hi thng xung pha di y bnh m hi c x ra xung quanh theo cc rnh x hai bn.6.4 Bnh tch lng: 6.4.1 Cng dng, nguyn l lm vic: ngn nga hin tng ngp lng gy h hng my nn, trn ng hi ht v my nn ngi ta b tr bnh tch lng. Bnh tch lng s tch cc git hi m cn li trong dng hi trc khi v my nn.Bnh tch lng lm vic theonguyn l tng t bnh tch du. im khc bit nht gia cc bnh l bnh tch lng phm vi nhit lm vic khc. Bnh tch du lm vic nhit cao cn bnh tch lng lm vic phm vi nhit thp nn cn bc cch nhit, bnh tch du t trn ng ng y, cn bnh tch lng t trn ng ng ht. 6.4.2 Cu to bnh tch lng:Trang 32Trang 1Trang 2Trang 3345161 ng gas vo2 Vnh gia cng3 ng gas ra4 Nn chn trn5 - Ca hi x vo bnh6 - Lng raHnh 6-5: Bnh tch lng kiu nn chn, ti liu tham kho [7].6.5 Bnh tp trung du:Trong h thng lnh NH3, du c thu gom v bnh thu hi du. Bnh thu hi du c cu to ging bnh cha cao p gm cc b phn sau: thn bnh dng tr, cc y elip, trn c lp b ng thy xem mc du, van an ton, ng h p sut, ng du thu hi v, ng ni v ng ht v x y bnh. thuhi du t cc thit b v bnh thu hi du, trc ht cn phi to p sut thp trong bnh nh ng ni thng ng ht ca my nn. Sau m van x du ca cc thit b du t ng chy v bnh. Du sau c x ra ngoi em x l hoc loi b, trc khi x du nn h h p sut trong bnh xung xp x p sut kh quyn. Khng c p sut chn khng trong bnh khi x du, v nh vy khng nhng khng x c du m cn lt kh khng ngng vo bn trong h thng.Trang 5Hnh 6-6 : Bnh thu hi du, ti liu tham kho [7].1 Knh xem mc 4 ng ni v ng ht2 p k 5 ng x du3 Van an ton 6 ng hi du v6.6 Bnh tch kh khng ngng:6.6.1 Cng dng: Trang 1541326BTG, BCCA BTD BTLKhi lt kh khng ngng vo bn trong h thng lnh, hiu qu lm vic v an ton ca h thng lnh gim r rt, cc thng s vn hnh c xu hng km hn:+ p sut v nhit ngng t tng.+ Nhit cui qu trnh nn tng.+ Nng sut lnh gim. V vy nhim v ca bnh l tch cc kh khng ngng trong h thng lnh, x b ra bn ngoi nng cao hiu qu lm vic, an ton h thng, ng thi trnh khng c x ln mi cht ra bn ngoi.Nguynnhnlt kh khngngng: kh khngngnglt vohthngdonhiu nguyn nhn khc nhau: + Do ht chn khng khng trit trc khi np mi cht lng, khi lp t h thng.+ Khi sa cha, bo dng my nn v thit b.+ Khi np du cho my nn. + Khi phn hy du nhit cao.+ Do mi cht lnh b phn hy.+ Do r r pha h p, pha h p trong nhiu trng hp c p sut chn khng, nn khi c vt r khng kh bn ngoi s lt vo bn trong h thng.6.6.2 Cu to v nguyn l hot ng:Bnh tch kh khng ngng hot ng trn nguyn tc lm lnh hn hp kh khng ngng c ln hi mi cht ngng t ht mi cht, trc khi x kh ra bn ngoi.Kh khng ngng thng tp trung nhiu nht thit b ngng t, bnh cha cao p. Khi dng mi cht n thit b ngng t, hi mi cht c ngng t v chy v bnh cha cao p. Phn ln kh khng ngng c tch t ti thit b ngng t, tuy nhin vn cn ln rt nhit mi cht lnh cha c ngng ht. V vy ta chuyn hn hp kh n bnh tch kh khng ngng, tip tc c lm lnh nhit thp hn ngng t ht mi cht lnh. Kh khng ngng sau c x ra ngoi.Cu to bnh tch kh khng ngng gm thn bnh hnh tr, cc y dng elip, bn trn c b tr cc thit b nh van an ton, ng h p sut. Bn trong c bnh c ng trao i nhit dng xon lm lnh v ngng t hi mi cht. Mi cht sau khi ngng t c hi v Trang 2pha trc tit lu tit lu lm lnh bnh.6.7 Thp gii nhit:6.7.1 Cng dng:Nhim v ca thp gii nhit l thi ton b lng nhit do mi cht lnh ngng t ta ra. Lng nhit ny c thi ra mi trng nh cht ti nhit trung gian l nc. Nc vo bnh ngng c nhit 1 wt, nhn nhit ngng t tng ln khong 50C, ra khi bnh ngng c nhit 2 wt. Nc sau khi ra khi bnh ngng c a sang thp gii nhit v phun thnh cc git nh. Nc nng chy theo khi m xung, trao i nhit v cht vi khng kh i ngc dng t di ln trn nh qut gi cng bc. Qu trnh trao i nhit v cht ch yu l qu trnh bay hi mt phn nc v khng kh. Nhit nc gim 50C vxung nhit ban u 1 wt.6.7.2 Cu to:Thp c lm bng vt liu nha composit kh bn, nh v thun li lp t. Bn trong c cc khi nha c tc dng lm ti nc, tng din tch v thi gian tip xc. Nc nng c bm ti t trn xung, trong qu trnh phun, ng phun quay quanh trc v ti u ln trn cc khi nha. Khng kh c qut ht t di ln v trao i nhit cng bc vi nc. Qut c t pha trn ca thp gii nhit. Pha di thn thp c cc tm li c tc dng ngn khng cho rc bn ngoi ri vo bn trong b nc ca thp v c th tho ra v sinh y thp. Thn thp c lp ghp t cc tm ri, v tr lp ghp to thnh gn lm cho thn thp vng chc hn. ng nc vo ra thp bao gm: ng nc nng vo, ng bm nc i, ng x trn, ng x y v ng cp nc b sung.Trang 2123498714 11 12 13 66510Trang 2Bnh ngngHnh 6-7: Cu to thp gii nhit, ti liu tham kho [7].1 ng c qut gi; 2 V thp; 3 Chn bi nc; 4 Dn phun nc;5 Khi m; 6 Ca khng kh vo; 7 B nc; 8 ng nc lnh cp lm mt bnh ngng; 9 ng nc nng t bnh ngng ra a vo dn phun lm mt xung nh khng kh i ngc chiu t di ln; 10 Phin lc nc; 11 Phu chy trn; 12 Van x y; 13 ng cp nc vi van phao; 14 Bm nc.Chng 7: T NG HA V VN HNH H THNG LNH7.1 Trang b t ng ho:My nn l thit b quan trng nht trong h thng lnh, v vy n c bo v rt nghim ngt.Khi cc iu kin lm vic khng t yu cu, h thng bo v t ng ngt in dng my. My nn c bo v bi cc thit b sau:- Bo v p sut: p sut cao HP, p sut du OP, p sut thp LP.- Bo v qu dng v qu nhit (OCR).- Bo v cc iu kin gii nhit khng tt: + Bo v p sut nc, lu lng nc.+ Bo v khi bm gii nhit dn ngng ngng hot ng.+ Bo v khi qut thp gii nhit khng lm vic.+ Bo v bm gii nhit my nn.- Bo v khi mt s thit b khc khng lm vic: My nn s t ng dng khi mt thit b no khng lm vic chng hn nh qut dn lnh, bm nc lnh,- Ngoi ra ta cn trang b in iu khin mc dch bnh trung gian v iu khin nhit phng lnh.iu khin mc dch bnh trung gian: iu khin mc dch bnh trung gian ta s dng cc van phao in t. Mc dch bnh trung gian c khng ch gia hai mc: cc i v cc tiu.Khng ch mc cc i nhm bo v my nn trnh ht m, gy ngp lng pha cao p.Mc cc tiu c khng ch nhm m bo lng dch ti thiu trong bnh trung gian tng cng trao i nhit cho ng xon. Khi mc dch trong bnh t mc cc i van phao pha trn tc ng ngt in cun dy van in t cp dch cho bnh trung gian, Trang 1khi mc dch trong bnh s khng tng. Khi mc dch h xung mc cc tiu, van phao tc ng m van in t v dch c tit lu vo bnh.iu khin nhit phng lnh: i vi kho lnh bo qun, h thng lnh hot ng hon ton t ng v c iu khin ng ngt theo nhit phng. Khi nhit phng lnh t yu cu (bng nhit ci t ca thermostat), thermostat tc ng ng van in t ngng cp dch cho dn lnh, my tip tc hot ng nn p sut ht h xung, sau mt thi gian khi p sut ht xung thp, rle p sut thp tc ng dng my. Khi nhit phng nng ln cao, thermostat tc ng m van in t cp dch cho dn lnh, p sut ht tng ln v rle p sut thp ng mch khi ng my nn.V nguyn tc, thermostat c th trc tip tc ng mch iu khin ng my nn. Tuy nhin m bo an ton khi dng my phi ht kit gas khi dn lnh nn ngi ta mi cho hot ng nh trn.7.1.1 Trang b in ng lc:Mch in ng lc:cn gi l mch in ngun l mch in cp in ngun chy cc thit b my nn, bm, qut, i vi ng c v thit b in ca h thng lnh do cng sut ln nn vic ng m cc ng c c thc hin bng cc khi ng t. Cc thit b u c ng m v bo v bng cc aptomat, tt c cc thit b u c rle nhit bo v qu dng.Cc thit b c cng sut nh th dng ampe k ni trc tip vo mch in, cn thit b c cng sut ln th ampe k c qua bin dng CT. i vi ng c my nn qu trnh khi ng din ra nh sau: Khi nhn nt START trn mch iu khin, nu khng c bt c s c no th cun dy khi ng t MC c in v ng tip im thng m MC trn mch ng lc. Trong khong 5 giy u tin (t rle thi gian), cun dy khi ng t (MS) c in v tip im thng m MS ca n trn mch ng lc ng.Lc my chy theos sao, dng khi ng gim ng k.Sau thi gian t rle tc ng ngt in cun MS v ng in cho cun MD, tng ng cc tip im trn mch ng lc MD ng, MS m. My chuyn t s sao sang s tam gic. i vi cc thit b c cng sut nh hn nh bm, qut dng khi ng nh nn khng cn khi ng theo s sao tam gic nh my nn. 7.1.2 Mch in iu khin:a. Mch khi ng sao tam gic:Cc k hiu trn mch in:MC, MS v MD cun dy khi ng t s dng ng mch chnh, mch sao v mch tam gic ca ng c my nn.Trang 3AX rle trung gian.T rle thi gian.Khi h thng ang dng, cun dy ca rle trung gian (AX) khng c in, cc tip im thng m ca n trng thi h nn cc cun dy (MC), (MS) v (MD) khng c in.Khi nhn nt START khi ng my nn, nu h thng khng c s c p sut cao, p sut du, p sut nc, qu nhit th cc tip im thng ng HPX, OPX, WPX, OCR trng thi ng. Dng in i qua cun dy ca rle trung gian (AX). Khi cun dy (AX) c in nh tip im thng ng AX mc ni tip vi tip im MCX nn t duy tr in cho cun (AX). Tip im thng m MCX ng khi khng c s c p sut nc bm gii nhit my nn.Khi cun dy (AX) c in, tip im thng m AX th hai ca n s ng mch in cho cc cun dy khi ng t (MC) v (MS) hoc (MD).Trong thi gian 5 giy u (thi gian ny c th thay i ty ) rle thi gian T c in v bt u n thi gian, mch cun dy khi ng t (MS) c in, my chy theo s ni sao, cun (MD) khng c in.Sau thi gian 5 giy, tip im ca rle thi gian nhy v ng mch cun (MD) v mch cun (MS) mt in. Kt qu my chuyn t s ni sao sang s tam gic.Do cun dy (MC) ni vi cp tip im thng m MS, MD ni song song nn d my c chy theo s no th cun (MC) cng c in. Khi xy ra qu nhit (do my qu nng hay dng in qu ln) th c cu lng kim ca rle qu nhit OCR nhy v ng mch n bo hiu s c bo hiu s c ng thi cun (AX) mt in v ng thi cc khi ng t ca ng c my nn mt in v my dng.Nu xy ra mt trong cc s c p sut du, p sut cao hoc p sut nc hoc nhn nt STOP th cun (AX) mt in v my nn cng s dng.b. Mch bo v p sut du:Khi h thng ang hot ng bnh thng, c cu lng kimca rle p sut du ng, cun dy rle trung gian (OP) mc ni tip vi n c in. Mch in cun (OPX) v n (L) khng c in do tip im thng ng OP v thng m OPX ang trng thi h.Khi p sut du nh hn gi tr nh sn, dng in qua in tr sy du ca rle v bt u t nng c cu lng kim, khi c cu lng kim nh ra cun dy rle trung gian (OP) Trang 2mc ni tip vi n mt in, ko theo cc tip im thng ng OP ng li, cun dy rle trung gian (OPX) v n (L) c in. Cun dy (OPX) c in ko theo tt c cc tip im thng ng ca n nh ra, cun dy (AX) trn mch in khi ng my nn mt in v tc ng dng my.Thng thng khi s c xy ra, cc mch in s c duy tr, ch khi x l xong s c v nhn nt RESET mi c th khi ng li my nn. Mch in cun s c (OPX) cng t duy tr thng qua tip im thng ng ca n. Nu khng c mch ny th s rt nguy him v ngi vn hnh c th khi ng li my nn ngay m khng n ang c s c p sut du.Trn mch p sut du, ngi ta s dng tip im thng m ca cun dy rle trung gian AX nh l iu kin mch p sut du c hiu lc. Mch s c ca cun (OPX) ch c hiu lc khi cun dy (AX) c in, tc my nn ang hot ng m mt p sut du. Trong trng hp khi khi ng my, do bm du cha hot ng nn hiu p sut dus bng 0, nhng nh cun (AX) cha c in nn mch s c p sut du cha c hiu lc v my vn c th khi ng c.c. Mch gim ti:Mch gim ti trong s s dng gim ti trong cc trng hp sau:- Khi mi khi ng ang chy theos sao, do dng khi ng rt ln nn bt buc phi gim ti.- Khi vn hnh do ph ti ln, ngi vn hnh mun gim ti bng tay.- Lc chy bnh thng (ch tam gic) nhng p sut ht qu thp, h thng hot ng khng hiu qu nn my chuyn sang ch gim ti.Khi gim ti cun dy van in t (SV) c in v m ng thng du tc ng ln c cu gim ti ca my nn gim ti.Cng tc xoay COS trn s iu khin cho php la chn ch gim ti bng tay MANUAL ngay lp tc, ch gim ti t ng AUTO hoc ngt mch gim ti OFF. Trong qu trnh khi ng khi ang chy theo s sao th my nn lun gim ti v lc nay cun dy khi ng t (MS) ang c in, tip im thng m ca n trn mch gim ti ng v cun (SV) c in.Khi ch t ng AUTO, ch khi p sut ht nh hn gi tr dt trc th s gim ti.Ngoi ra thi im bt k no cng c th gim ti my nn khi xoay cng tc COS Trang 2sang v tr MANUAL.Khi my nn ang ch gim ti, n s sng bo hiu h thng ang chy ch gim ti.d. Mch bo v p sut cao:Khi h thng ang hot ng bnh thng, tip im ca rle p sut cao HP m, n v cun (HPX) khng c in.Khi p sut pha y ca my nn vt khi gi tr m ta ci t trc khong 18,5 kG/cm2, tip im rle p sut HP ng (UP-ON), cun dy rle trung gian (HPX) c in v n sng bo hiu s c.Lc ny cc tip im thng ng HPX m ra.Trn mch khi ng cun (AX) mt in v tc ng dng my nn.Rle s c (HPX) cng t duy tr in cho n thng qua cc tip im thng ng RES v tip im thng m HPX. Ch sau khi khc khc xong s c v nhn nt RESET th cun (HPX) mi mt in.e. Mch bo v qu dng:OCR biu th c cu lng kim ca rle nhit, nhit bnh thng c cu lng kim ng tip im mch in cho cng tc t my nn v cun (AX). Lc ny h thng c th khi ng lm vic. Khi dng in chy qua ng c qu ln, my nn nng, c cu lng kim ca rle nhit nh ra v mch in khi ng ca my nn mt in, c cu lng kim nhy sang pha mch n v n sang bo hiu s c qu dng. Khi xy ra s c qu dng phi i cho c cu lng kim ngui v nhy v v tr bnh thng th mi c th khi ng li c. Mch bo v qu dng phc hi qua nt RESET nh cc mch s c khc.f. Mch iu khin v bo v bm, qut gii nhit:Mch in c tc dng chy cc bm qut gii nhit dn ngng v bo v my nn khi p sut nc thp. chy cc qut v bm gii nhit c th thc hin theo 2 ch : Ch bng tay: Bt cng tc COS sang v tr MAN, nu khng c s c p sut nc v s c qu dng ca cc bm qut (tip im WPX v OCR ng) cc cun dy khi ng t ca cc bm qut c in v ng in cho ng c cc bm qut.Trang 3 Ch t ng: Bt cng tc COS sang v tr AUTO, ch t ng bm qut s khi ng cng vi my nn. Sau khi nhn nt START trn mch khi ng nu khng c bt c s c no th cun (AX) c in ng thi ng tip im AX cp in cho cc cun dy ca cc khi ng t (MCP1), (MCP2), (MCCF1) v (MCCF2) ca bm, qut gii nhit v bm, qut hot ng.Khi mt trong cc thit b bm gii nhit my nn, bm v qut gii nhit dn ngng khng lm vic th cun (MCX) mt in, my khi ng my nn mt in v ngng my nn. Bo v qu dng bm, qut gii nhit: Khi mt trong cc thit b gm bm gii nhit my nn, bm gii nhit v cc qut gii nhit dn ngng b qu dng, rle nhit nhy khi v tr thng ng v ng mch in cun dy rle trung gian (AUX) v n sang bo s c. Cun dy s c (AUX) ng mch chung bo hiu s c ng thi cun dy rle trung gian (MCX) mt in.Tip im thng m ca n trn mch khi ng nh ra, cun (AX) mt in v my dng ngay lp tc.g. Mch bo v p sut nc:Trong h thng ny c hai bm: bm gii nhit dn ngng v bm gii nhit my nn, v th tng ng s c 2 rle p sut nc WP1 v WP2 bo v.Khi ang hot ng bnh thng, tip im ca cc rle p sut nc m, cun dy rle thi gian T2 khng c in.Khi xy ra s c mt p sut nc ca mt trong hai bm th cun dy rle thi gian T2 c in v bt u m thi gian. Nu s c ko di qu thi gian t (10 giy) tip im T2ng, cun (WPX) c in v n sng bo hiu s c.Cun WPX t duy tr nh tip im thng ng ca n v tip im RES.ng thi vi bo hiu s c tip im thng ng ca WPX trn mch khi ng nh ra, cun (AX) mt in v my dng. Rle thi gian T2 rt quan trng, n c tc dng iu khin dng my khi p sut nc thc s gim trong mt thi gian nht nh, m khng tc ng tc thi. Trnh trng hp dng my do gim p sut tc thi khi c cc bt kh trong dng nc hoc dao ng bt thng khc.Sau s c p sut nc, mun khi ng li h thng phi nhn nt RESET mi c th khi ng li my nn.Trang 2h. Mch iu khin nhit kho lnh:Nhit kho lnh c iu chnh hon ton t ng v iu khin ng ngt cp dch thng qua dixell XR-60C.M t chung v dixell XR60C:XR60C c kch thc 32 x 74 mm l b iu khin cho cc h thng lnh c nhit trung bnh hoc thp. Thit b c 3 r le ng ra kiu khin my nn, b x (loi in tr hoc gas nng) v cc qut ca dn lnh. Thit b c 2 cm bin PTC ng vo, mt cho vic iu khin nhit , mt c t pha trn dn lnh kim sot nhit kt thc vic x .S u in ca dixell XR60C nh sau:Hnh 7-1: S in ca Dixell XR60C, ti liu tham kho [7].i. Mch chung bo ng s c:Khi xy ra cc s c p sut hoc qu dng, mch in ca chung BZ c in v chung reo bo s c. Khi ngi vn hnh phi nhn nt BELL STOP ngng chung. Lc cun dy ca rle trung gian (BZX) c in v tip im thng ng ca n nh ra, ngt in ca chung BZ.Sau khi khc phc cc s c xong bm nt RESET, in i qua cun dy ca rle trung gian (RES), tt c cc tip im thng ng RES ca n trn cc mch s c s nh ra, Trang 3lm mt in mch bo s c v h thng c th bt u khi ng.7.2 Vn hnh h thng lnh:7.2.1 Chun b vn hnh:Kim tra in p ngun khng c sai lch so vi nh mc 5%:360V < U < 400V.Kim tra bn ngoi my nn v cc thit b chuyn ng xem c vt g gy tr ngi s lm vic bnh thng ca thit b khng.Kim tra cht lng v s lng du trong my nn. Mc du thng phi chim 2/3 mt knh quan st. Mc du qu ln v qu b u khng tt.Kim tra mc nc trong cc b cha nc, trong thp gii nhit, trong b dn ngng ng thi kim tra cht lng nc xem c m bo yu cu k thut khng. Nu khng m bo th phi b b sung nc mi, sch hn.Kim tra cc thit b o lng, iu khin v bo v h thng.Kim tra h thng in trong t in, m bo trong tnh trng hot ng tt.Kim tra tnh trng ng m ca cc van:+ Cc van thng ng: Van x y cc bnh, van np mi cht, van by-pass, van x kh khng ngng, van thuhi du hoc x v du, van iu ho cc h thng, van x kh. Ring van chn ng ht khi dng my thng phi ng v khi khi ng th m t t.+ Tt c cc van cn li u trng thi m. c bit ch van u y my nn, van chn ca cc thit b o lng v bo v phi lun m.+ Cc van iu chnh: Van tit lu t ng, rle nhit, rle p sut, ch c ngi c trch nhim mi c m v iu chnh.7.2.2 Vn hnh:Hthnglnhcthit kchai chvnhnh: Chvnhnhtng (AUTO) v ch vn hnh bng tay (MANUAL).a. Cc bc vn hnh t ng AUTO:- Bt aptomat ca t in ng lc, aptomat ca cc thit b ca h thng cn chy.Trang 2- Bt cc cng tc chy cc thit b sang v tr AUTO.- Nhn nt START cho h thng hot ng. Khi cc thit b s hot ng theo trnh t nht nh.- T t m van chn ht ca my nn.Nu m nhanh c th gy ra ngp lng, mt khc khi m qu ln dng in ng c cao s qu dng, khng tt.- Lng nghe ting n ca my, nu c ting g bt thng km sng bm nhiu u ht th dng my ngay.- Theo di dng in my nn.Dng in khng c qu ln so vi quy nh.Nu dng in qu ln th ng van chn ht li hoc thc hin gim ti bng tay. - Quan st tnh trng bm tuyt trn thn my nn.Tuyt khng c bm nn phn thn my qu nhiu. Nu ln qu th ng van chn ht li v tip tc theo di.-Tiptcmvanchnht cho n khi m hon ton nhng dng in my nn khng ln qu quy nh, tuyt bm trn thn my khng nhiu th qu trnh khi ng xong.- Bt cng tc cp dch cho dn lnh, bnh trung gian.- Kim tra p sut h thng:+ p sut ngng t: Vi NH3: Pk < 16,5 kg/cm2 (tk < 400C).+ p sut du:Pd = Ph + (23) kG/cm2.- Ghi li ton b cc thng s hot ng ca h thng. C 30 pht ghi mt ln. Cc s hiu bao gm: in p ngun, dng in cc thit b, nhit u y, u ht v nhit tt c cc thit b, bung lnh, p sut u y, u ht, p sut trung gian, p sut du, p sut nc.- So snh v nh gi cc s liu vi cc thng s vn hnh.b. Cc bc vn hnh bng tay (MANUAL):- Bt aptomat tng ca t in ng lc, aptomat ca tt c cc thit b ca h thng cn chy.Trang 1- Bt cc cng tc chy cc thit b nh bm, qut gii nhit, qut dn lnh, thp gii nhit, sang v tr MANUAL. Tt c cc thit b ny s c chy trc.- Bt cng tc gim ti my nn sang MANUAL gim trc khi chy my.- Bm nt START cho my nn hot ng.- M t t van chn ht v quan st dng in my nn nm trong gii hn cho php.- Bt cng tc cp dch dn lnh, bnh trung gian, ng thi quan st v theo di cc thng s nh ch AUTO.- Sau khi m hon ton van chn ht, nhng cc thng s nh dng in, p sut ht, bm tuyt bnh thng th tin hnh ghi li cc thng s vn hnh, c 30 pht ghi mt ln.7.2.3 Dng my:a. Dng my bnh thng:H thng ang hot ng ch t ng:- Tt tt c cc cng tc cp dch cho dn lnh, bnh trung gian. - Khi p sut Ph < 5