B GIO DC V O TOTRNG I HC NNG LM THNH PH H CH MINH N MN HC K THUT LNH TNH TON THIT K H THNG MY LM NC CY 20 TN / NGYH v tn sinh vin: Dng Cng ThnhTrn nh Trng V Ngc HinNgnh: CNG NGH NHIT LNHNin kha: 2008 2012.Thng 07/2011 N K THUT LNHNhm 4TNH TON THIT K H THNG MY LM NC CY 20 TN / NGYNhm thc hin: 1. Dng Cng Thnh08137023ST:016885618622. Trn nh Trng 08137025ST:016685989223. V Ngc Hin 08137002 ST:01689949373 n c thc hin nhm tm hiuv p ng yu cu mn hc.Gio vin hng dn:Thc s L Vn BnThng 07/20112 N K THUT LNHNhm 4MC LC2.1. H thng sn xut nc cy /10/................................................................................................................5 2.2. Cng dng v phn loi nc /10/ .............................................................................................................5 2.4. Nguyn l lm vic /9/......................................................................................................................................7 3.1 Phng tin thc hin .......................................................................................................................................9 3.2 Phng php tin hnh..................................................................................................................................... 9 3.2.1 Phng php nghin cu l thuyt .............................................................................................................9 3.2.2 Phng php thc hin ...............................................................................................................................9 CHNG 4 KT QU V THO LUN................................................................... 10 4.1. kt qu tnh ton............................................................................................................................................10 CHNG 5KT LUN V NGH...................................................................... 43 3Chng 1 M U1.1. t vn T xa xa con ngi bit ly cc loi nc thin nhin t sng, sui, ao, h s dng lm lnh, d tr trong nh ma h li em ra dng. Qu trnh hnh thnh thin nhin da vo lnh ca thin nhin, nhiu ni ma ng khng kh lnh n -20 C, -30 C lm cho nc trong ao, h, sng, sui, b ng bng.Cho n khi ngnh lnh ra i, v bt u pht trin mnh trn th gii th con ngi s dng k thut lnh vo trong nhiu mc ch khc nhau ca mnh, t n gin cho n tinh vi.Mt trong nhng ng dng u tin ca con ngi chnh l sn xut ra nc ( nhn to) nhiu dng khc nhau( dng khi, dng vin, dng vy, dng bt, .), tu theo yu cu s dng v iu kin sn xut thc t.1.2. Mc ch ca n :-Tinh toan thit k may lam n c cy 20 tn / ca-C th:+ Tnh chn my nn+ Tinh toan b + Tnh chn dn ngng+ Tnh chn cc thit b phChng 2 TNG QUAN2.1. H thng sn xut nc cy /10/Phng php sn xut cy l mt trong nhng phng php c in nht. cy c sn xut trong cc bdung dchmui lnh, c nhit khong 10oC. Nc c t trong cc khun c kch thc nht nh, theo yu cu s dng. Khi lng thng gp nht ca cc cy l 12,5; 25; 50 kg. u im ca phng php sn xut cy l n gin, D thc hin, c khi lng ln nn vn chuyn bo qun c lu ngy, c bit dng cho vic bo qun c, thc phm khi vn chuyni xa. Ngoi ra cy cng c s dng lm sinh hot v gii kht ca nhn dn. Tuy nhin, cy c mt s nhc im quan trng nh: chi ph u t, vn hnh ln, cc ch tiu v v sinh khng cao do c nhiu khu khng m bo v sinh, tnh ch ng trong sn xut thp do thi gian ng lu. i km theo hthng my cy phi trang bithm nhiu hthng thit bikhc nh: hthng cu chuyn, Hthng cp nc khun, bnhng , bn lt , kho cha , my xay .V vy ngy nay trong k thut ch bin thc phm ngi ta t s dng cy. Nu c trang bi cng ch nhm bn cho tu thuyn nh c bo qun lu ngy.2.2. Cng dng v phn loi nc /10/2.2.1.Cng dng nc aNc c nhiu ng dng trong i sng hng ngy cng nh trong sn xut, sau y l mt s ng dng ca nc :- Bo qun thc phm- iu tit khng kh- Th duc th thao- Cng nghip ha cht2.2.2.Phn loi nc aC nhiu cch phn loi nc : Da vo nguyn liu sn xut: Nc t nc ngt (nc l, si, nguyn cht). Nc t nc bin, t nc mui. Nc t nc st trng v khng sinh. N K THUT LNHNhm 4 Da vo trong ca : Nc pha l Nc trong sut Nc c Da vo hnh dng: Nc khi Nc tm Nc thi Nc ng Nc vy2.3. Cu to my cy [khi] /10/6 N K THUT LNHNhm 4H thng c cc thitbchnh sau: 1- My nn: My nn 1 cp, sdngmi cht NH3 hoc R22. 2. Bnh cha cao p. 3. Dnngng: Cths dngdnngngtbayhi, bnhngng, dnngng t kiuti vcthsdng dn ngng khng kh. 4. Bnh tch du. 5. Bnh tch kh khng ngng. 6. Bnh thu hi du (s dng trong h thng NH3). 7. Bnh tch lng. 8. Bnh gi mc- tch lng. 9. Bncmui lm, cngbcnhkhuyvdn lnh kiu xng c.2.4. Nguyn l lm vic /9/Cc loi cy vi khi lng khc nhau c sn xut bng phng php lm lnh trong b nc mui. y l phng php ph bin nht trong nh my nc hin nayB nc mui c chia lm hai ngn, ngn ln b tr cc khun , cn ngn nh b tr dn bay hi lm lnh nc mui trong b c b tr mt bm nc mui tun hon mnh t dn bay hi ra lm lnh khun ri li quay li dn bay hi. Bm nc mui b tr thng ng trnh r r nc mui ra ngoi. Dn bay hi kiu xng c c kh nng tng kh nng trao i nhit ln ng k. Cc khun c ghp li vi nhau thnh linh sut chiu ngang ca b. Cc linh khng phi ng im trong b m chuyn ng t u ny n u kia ca b nh c cu chuyn ng xch. Khi mt linh kt ng xong v c nhc ra khi b th c cu xch chuyn 7 N K THUT LNHNhm 4ng dn tt c cc linh ln cha ra pha cui b mt khong h va t linh a y ncmi vo. Chuyn ng gia nc mui tun hon v linh l ngc chiu. Khi akt ng trong khun, ton b linh c cu trc nng ra khi b v th vo b lm tan gi. Cc khun nng ln, lp bng dnh khi vi khun tan ra, cu trc s nng trt ln bn trt vo kho cha , cn linh c cu trc a n mng rt nc, mng rt nc t ng nhiu vi c nh lng rt ng thi cho tt c cc khun lng nc anh trc. Sau khi rt nc xong linh c t vo u b v tr m c cu chuyn ng xch va y ton b cc linh dch ra. Vi phng php ny nc sau khi qua qu trnh x l c vo khun nh hnh sn, cc khun ny c t trong b nc mui, b ny c lm lnh bi thit b bc hi , sau mt thi gian nc trong khun c lmlnh vkt tinh li.Qu trnh kt thc, c ly ra t cc khun v s dng .8Chng 3 PHNG PHP V PHNG TIN3.1 Phng tin thc hin- My vi tnh c nhn.- Cc ti liu lin quan3.2 Phng php tin hnh3.2.1 Phng php nghin cu l thuyt- Tra cu ti liu sch bo nhm phc v mc ch ti.- Tm kim cc thng tin lin quan n ti qua mng internet.3.2.2 Phng php thc hinTheo phng php tng hp v k tha ta tin hnh theo trnh t sau:- Tin hnh nghin cu v tng hp li cc ti liu c - La chn cc vn lin quan n ti - Tnh ton chn cc thit b ca h thng my cyChng 4 KT QU V THO LUN4.1. kt qu tnh ton 4.1.1. Cc la chn ban ua. Chn phng php thit k nc /9/- Cc giai on sn xut nc Giai on 1: l h nhit ca nc t nhit t1 (nhit ban u ca nc) xung nhit 0oC.Giai on 2: l giai on kt tinh nc hon ton, chuyn nc t trng thi lng trng thi rn.Giai on 3: l giai on h thp nhit bng ca nc t 0oC xung nhit t2 (thng chn -5oC).Vy nhit lng ring cn thit chuyn 1Kg nc nhit ban u t1 thnh nc nhit t2 c tnh theo cng thc: /2/- Chn phng php sn xut nc Cc loi cy vi khi lng khc nhau c sn xut bng phng php lm lnh trong b nc mui. y l phng php ph bin nht trong nh my nc hin nay. Cc loi cy vi khi lng khc nhau c sn xut bng phng php lm lnh trong b nc mui. y l phng php ph bin nht trong nh my nc hin nay. Vi phng php ny nc sau khi qua quy trnh x l c vo khun nh hnh sn, cc khun ny c t trong b nc mui, b ny c lm lnh bi thit b bc hi , sau mt thi gian nc trong khun c qu lnh v kt tinh li. Quy trnh kt thc, cy c ly ra t cc khun v s dng.Kt cu cy hin nay c cc c khi lng thng dng nh sau:Loi 3,5 Kg, loi 12,5 Kg, loi 25 Kg, loi 50 Kg. y ta chn loi 50 kg. b. Chn cht ti lnh /9/- Yu cu ca cht ti lnhCht ti lnh phi m bo nhng yu cu sau: Nhit ng c phi thp. Nhit dung ring v kh nng dn nhit cao. nht v trng lng ring nh.( ) ( )2 10 0 . t C L t C qpnd pn + + N K THUT LNHNhm 4 Khng n mn kim loi v cc vt liu khc trong thit b. Khng c hi v khng nguy him.D kim, r tin, d bo qun v d vn hnh.- Phn tch tnh cht ca cht ti lnhCht ti lnh c ban trng thi: Rn, lng, kh- Chn cht ti lnhBng: nhit ng c ca mt s dung dch muiSThTMui ha tanNng %Khi lngNhit ng c1234NaClCaCl2MgCl2MgSO423,129,92019-21,2-55-35-9,9Trong sn xut, ngi ta thng chn nhit dung dch cht ti nhit thp hn nhit ng l 5oC, v cao hn nhit ng bng ca dung dch khong 10oC.Nhit ng l -5oC, nn nhit trung bnh ca cht ti nhit l -10oC, v nhit ng c ca dung dch l -20oC. Cho nn, dung dch NaCl 23,1% c nhit ng c l 21,2oC, s tha iu kin trn.Ngoi ra do NaCl r tin v c nhiu trn th trng nn vic chn dung dch NaCl lm cht ti lnh l hp l.c. Chn tc nhn lnh /9/Ta nhn thy tc nhn NH3 l thch hp nht vi h thng sn xut nc v: C nng sut lnh ring ln So vi Freon th NH3 c nng sut lnh ring ln hn, h s truyn nhit ln hn. Tn tht trong qu trnh tit lu nh D pht hin s r r ca tc nhn ra ngai do n c mi c trng Nhit ng c v bay hi ca NH3 rt thpT = - 77,7 0CTbh = - 33,35 0CVi khong nhit ny th NH3 khng th ng c trn ng ng gy tt nghn v n ng ng tc nhn khi dng sn xut .Vy ta chn tc nhn lnh l NH3.11 N K THUT LNHNhm 412d. Quy trnh sn xut nc Nc c bm trc t ging ln, qua qu trnh x l, tch b cn b c trong nc. Nc c cha trong h, mt phn c ha vi mui vi lng thch hp to ra nng mui theo mun, mt phn cho vo cc khun . t cc khun vo b nc. Do kt cu ca b , khun c gi trn cc thanh bt ngang b. Sau mt ngy m, nc c ng thnh . Khi c nhu cu s dng, ta ly ln bng phng php th cng. Nc ly t gingX l ncncCp nc vo b chaRt nc vo khunCho vo b ng bngLy th cngCn bMui Ho tan trong b C t t toql k ql38 3 41 C t t tql o qn010 5 15 + + N K THUT LNHNhm 4Ta dng nc nhit thng, xi ln trn khun , nhm tch ra khi khun.e. Chn cc thng s k thut- Chn thit b ngng t trong h thng lnh l kiu xi ti c trch lng gia dng.- Nhit ca nc vo gin xi titw1 = 33oC.- Theo nhng iu kin cng ngh phn trn, nhit ng bng ca nct = -5oC.- Nhit trung bnh ca nc mui tm = -10oC.- Nhit si ca mi cht lnhVi hiu nhit yu cu c chn l t = 5oC.- Nhit nc ra khi gin xi ti - Nhit ngng t ca mi cht lnhTrong chn tk = 5oC.- Nhit qu lnh mi cht lnhTrong qu lnh c chn tql = 3oC.- Nhit qu nhit mi cht lnhTrong qu nhit c chn tqn = 5oC.C t t tom o15 5 10 ( ) C t tow w36 3 33 3 21 2 + + C t t tok w k41 5 362 + + /1//1//1/14 N K THUT LNHNhm 44.1.2. Tnh chu trnh lnh /9/Bng cc thng s cn cho tnh ton chu trnh lnh toCpMpahKJ/Kgm3/Kg1' -15 0.2425 1739.290.51 -10 0.2425 1757.142 138 1.7143 2057.142' 41 1.7143 17753' 41 1.7143 678.5713 38 1.7143 664.2864 -15 0.2425 664.286Nng sut lnh ring Nng sut lnh ring th tch Cng nn ringNng sut nhit ring- Chn cp my nnTa c t s nn 9 125 , 724 , 071 , 10< ppkKg KJ h h qo/ 86 , 1092 286 , 664 14 , 17574 1 3/ 71 , 21855 , 086 , 1092m KJqqov Kg KJ h h l / 300 14 , 1757 14 , 20571 2 Kg KJ h h qk/ 86 , 1392 286 , 664 14 . 20573 2 Kg KJ h h qo/ 86 , 1092 286 , 664 14 , 17574 1 ph15 N K THUT LNHNhm 4Chn chu trnh lnh mt cp nn.4.1.3. Tnh chi ph lnh a. Tnh cch nhit, cch m /9/- Tnh cho tng b + Tnh b dy lp cch nhit

Hnh 1: Cu to tng b Lp Vt liub dy mh s dn nhit W/m.Kh s khch tn m g/mhMpa1 Lp ximang v va 0.02 0.88 902 Lp gch ng v st 0.38 0.82 1053 Lp ximang v va 0.02 0.88 904 Lp cch m - giy du 0.004 0.18 1.355 Lp cch nhit - styropore cn0.047 7.56 Lp cch nhit, cch m - bitum 0.1 0.18 0.867 Lp thp tm 0.006 39 0H s dn nhit ca tng /2/]Chn K1= 0,3 W/m2.B dy lp cch nhit+ + +61 2 111 11i cncniiK 1]1

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+ + 612 1 11 1 1.iiicn cnK 16 N K THUT LNHNhm 4/2/Vi: H s cp nhit pha ngoi b 1 = 19,18 W/m2.. H s cp nhit pha trong b 2 = 813,94 W/m2..Chn cn = 0,15 m.+ Kim tra ng sngVi b dy lp cch nhit trn, tnh li h s truyn nhit K1 = 0,231 W/m2..H s truyn nhit ng sng thc tViNhit khng kh bn ngoi b t1 = 35oC.Nhit trong b t2 = -10oC.Nhit ng sng (tra 35oC) ts = 34oC.Theo trn ta thy K1 < ks b mt b khng ng sng. Theo kt cu ca b, b mt trong b l tm thp, nn kt cu ca tng c cch m hon ton.- Tnh cho nn ca b Hnh 2: cu to nn b Lp Vt liub dy mh s dn nhit W/m.Kh s khch tn m g/mhMpa1 Lp thp0.006 39 02 Lp cch m cch nhit - bitum 0.1 0.18 0.86mcn1031 , 094 , 813139006 , 018 , 01 , 018 , 0004 , 082 , 038 , 088 , 002 , 0218 , 1913 , 01. 047 , 01]1

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+ + + + + + ( )K m Wt tt tkss. / 4049 , 010 3534 3518 , 19 95 , 0 . 95 . 022 111 17 N K THUT LNHNhm 43 Lp chiu lc - btong 0.2 1.1 304 Lp cch nhit, cch m bitum 0.1 0.18 0.865 Lp cch nhit styropore cn 0.047 7.56 Lp cch m - giy du0.004 0.18 1.357 Lp chiu lc -betong nn 0.2 1.1 308 t nn dm 0.1 0.46 30H s dn nhit ca nn /2/ChnK2 = 0.26 W/m2.H s cp nhit pha trong ca b2 = 813,94 W/m2..B dy lp cch nhit/2/Chn cn = 0,2 mH s truyn nhit K2 vi b dy lp cch nhit va mi tnh ton trn K2 = 0,167 W/m2.So snh vi h s truyn nhit c chn trn K2tt < K2chnVy iu kin c tha mn.V mt ngoi ca ca y b l nn t, khng tip xc vi khng kh nn y ta khng cn kim tra hin tng ng sng.Tng t nh vch ca b , mt trong ca nn cng c lt bng thp, xem nh cch m hon ton.b. Tnh ton chi ph lnh cho b /10/- Kt cu ca b Nng sut thit k b 20 tn/ngy, m.Khi lng mt cy 50 Kg.( ) B b btAm+ 0 0. . + +71 2211i cncniiK 1]1

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+ 712 21 1iiicn cnK mKcn1001 , 094 , 813146 , 01 , 01 , 12 , 018 , 0004 , 01 , 12 , 018 , 01 , 0239006 , 0 1. 047 , 021]1

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+ + + + + + 18 N K THUT LNHNhm 4Thi gian ng /1/Trong :Nhit trung bnh ca nc Chiu rng khun bo = 0,19 m (chn mt trn ca khun).i vi b , h sA = 4540 H sB = 0,026Tuy thi gian ng ch l 18,632 gi, nhng khi thit k ta nn chn thi gian cho mtmt m l 24 gi (1 ngy, m), thi gian chn d ra khng lm tiu tn nhiu chi ph lnh.S khun trong mt m S khun trn mt linhNlinh = 8khun.Khong cch gia 2 khun khun = 40mm.Khong cch khun ngoi cng vi tngkhun,tng =25mm.S hang trong bm2=50 /2 = 25 hng.Khong cch gia 2 hng hng = 25 mm.B rng ngn t gin lanh A = 900mm. B rng ca b W = 4160 + A= 5060 mm.Chiu rng lp dt b canh khuyB = 600 mmChiu rng doan h cui bC = 500 mmChiu di ca b L = B + C + m2.b= 12975 mm.Chiu cao ca b H = 1250 mmC tom10 ) ( 632 , 18 ) 026 , 0 19 , 0 ( 19 , 0104540gio + khunMN 40050. 19 N K THUT LNHNhm 4. Hnh 3: k cu b 20 N K THUT LNHNhm 4Hnh 4: kt cu trong b - Nhit tn tht qua kt cu bao cheChn H s truyn nhit qua vchk1 = 0,231 Kcal/m2.h.H s truyn nhit qua nnk2 = 0.167 Kcal/m2.h.H s truyn nhit qua npk3 = 2 Kcal/m2.h.Nhi ca mi trng quanh btf = 35oCNhit trung bnh ca nc mui tm = -10oCDin tch xung quanh bF1 = 2.(W+L+1412).H = 48,62 m2Din tch nn F2 = (W+706). (L+706)= 78,88 m2Din tch np F3 = W.L =65,64 m2- Nhit lm ng /2/Trong : Nng sut thit kG = 20 Tn/ngy,mNhit dung ring ca ncCpn = 4,18 KJ/Kg.Nhit ca nc khi a vo khun tn = 31oCNhit ng c ca ncL = 333,564 KJ/KgNhit dung ring ca nc Cpn = 2,09 KJ/Kg.Nhit cui qu trnh ng t2 = -5oC ngy KJ ngy Kcal t t F k Qm f i i/ 641420 / 2 , 153193 24 ). (1 ( ) ( ) [ ] ngy KJ t C L t C G Qpnd n pn/ 9471880 0 0 . 10 .232 + + 21 N K THUT LNHNhm 4- Nhit lm lnh khun /2/Trong S khun trong mt m nk = N =400 khunKhi lng ca mt khun gk = 7,2 KgNhit dung ring ca thp (vt liu lm khun)Ck = 0,418 KJ/Kg.Nhit ca nc khi a vo khun tf = 31oCNhit trung bnh ca nc mui tm = -10oC- Nhit tn tht do ng c cnh khuy /2/ Trong Cng sut ng c ca cnh khuyNi = 15KWHiu sut hot ng hu ch ca cnh khuyi = 0,85H s lm vic ca cnh khuy i = 0,95Ch s i ch s cnh khuy c dng i = 1 - Nhit tn tht khi tch ra khi khun/2/Trong Din tch xung quanh ca cy /2/ f = 1,25 m2B dy lp tan c th tch ra khi khun= 0,001 mKhi lng ring ca nc n = 900Kg/m3Chi ph lnh (nng sut lnh)( ) ngy KJ t t C g n Qm f k k kd/ 44 , 49357 . . .3 ngy KJ ngy Kcal N Qnii i i/ 1045020 / 8 , 250004 24 . . .1860 , 436004 ,_

ngy KJ Q Q Q Q Q Qo/ 54 , 112078275 4 3 2 1 + + + + ngy KJ L f n Qnd kd/ 1 , 150 . . . .5 224.1.4. Chn my nn /6/a. Tnh nng sut th tch thc t ca my nnNng sut lnh ca my nn cn lp t /2/Trong H s c k n tn tht trn ng ng v thit b ca h thng lnh k = 1,11/2/H s thi gian lm vicb = 0,91 /2/Nng sut lnh ringqo = 1092,857KJ/KgLng mi cht chy qua my nn Nng sut th tch thc t ca my nnb. Tnh nng sut th tch l thuyt ca my nnH s cp /3/Trong cng thc trn c/3/Vi Pk = Po = 0,008 Mpam = 1 (i vi my nn NH3 [2])t s th tch chtc = 0,04p sut bc hiPo = 0,2425 MPap sut ngng t Pk = 1,7143MPaV /3/Vy= 0,593Nng sut l thuyt ca my nn c. Chn my nnKWbQ kQo mno23 , 1583600 . 24 .. s KgqQmomnott/ 145 , 0 s m m Vtt tt/ 074 , 0 .3 '.w i r w k tl c 7216 , 0111]1

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+ oo omok koo ok lt c iPP PPP PcPP P 822 , 0273 41273 15.'++ kor w wTT 125 , 0593 , 0074 , 0 ttltVV N K THUT LNHNhm 4Theo bng 7 6 [3] chn my nn k hiu 110K hiuSxilanhng knh pitongmmVng quayVng/sVlt10-2 m3/sDimmRngmmCaommKhi lngKg 1104 115 24 8,35 950 900 800 770Nng sut l thuyt ca 1 my nn Vlt = 0,0835m3/sS my nn cn dng cho h thng lnh Chn ZMN = 2 myd. Chn ng c cho my nn- Chn ng c Cng nn on nhit ca my nn/3/ViCng nn ring ca my nn l = 300KJ/Kg Cng nn ch th /3/Trong : Hiu sut ch th (hiu sut c k n tn tht trong)/3/Vi b = 0,001 Cng tiu tn do ma st ChnPms = 0,059 Mpa Cng nn hiu dng /3/ Cng sut tip in /3/Trong chn: Hiu sut truyn ng ca khp ait = 0,95Hiu sut ca ng cel = 0,85myVVZltclttMN5 , 10835 , 0125 , 0 KW l m Ntt s563 , 84 . KW N N Nms i e15 , 113 + KWNNisi831 , 104 807 , 0 . + okoit bTTKK p V Nms tt ms32 , 8 . KWNNel teel12 , 140. 71 , 461 MNelelZNN24 N K THUT LNHNhm 4Vy cng sut tip in cho mi ng c:Chn t hp ng c AO 2 91 4 theo bng 7 10 [3]K hiu ng c AO 2 91 4Cng sut , KW 75Vng quay, vng/s 24,7Di , mm 2275Rng, mm 1215Cao, mm 1370Chiu di lp t, mm 2910ng knh ng ht, mm 100ng knh ng y, mm 65Cng sut d tr cho t hp my nn75 46,71 = 28,29 KWH s d tr- Tnh hiu sut ca my nnHiu sut ch th (hiu sut c k n tn tht trong)i = 0,807Hiu sut c k n tn tht ma st ca cc chi tit myHiu sut c k n tn tht do truyn ng t = 0,95Hiu sut ng c in el = 0,85Hiu sut ca my nn/3/61 , 1432 , 4575926 , 0 eieNN604 , 0 . . . el t e i 254.1.5. Tnh chn thit b ngng t (kiu xi ti)u im - Hiu qu trao i nhit cao, h s truyn nhit t 700 900 W/m2.K. - Cu to n gin, chc chn, d ch to vckhnngsdngcngunnc bn v dn ng trn rt d v sinh. - So vi bnh ngng ng v, lng nc tiu th khng ln. Nhc im - Trong qu trnh lm vic, nc bn tung to xung quanh, nn dn ch c th lp t bn ngoi tri, xa hn khu nh xng. - Dn ngng kiu ti tiu th nc kh nhiu do phi thng xuyn x b nc. - Dn ng khng c nhng km nng s rt nhanh chng b bc, h hng. - Hiu qu gii nhit chu nh hng ca mi trng kh hu.a. Mt dng nhit pha ngoi

N K THUT LNHNhm 4 th 15: th biu din s bin i nhit ca cc dngkhi qua thit b ngng tNhit nc votw1 = 33oCNhit nc ratw2 = 36oCNhit ngng ttk = 41oCHiu nhit trung bnh Nhit trung bnh ca nctwtb = 34,5oCCc thng s ca nc nhit trung bnhKhi lng ring= 994 Kg/m3H s dn nhit= 0,626 W/m. nht ng hc = 7,35 x 10-6m2/sNhit dung ringCpn = 4,19 KJ/Kg. nht ng lc hc = 7,306 x 10-4Pa.sChun sPr = 4,865Ly tiu hao nc cho 1 m ngml = 0,2Kg/s.mChiu dy mng nc chy trn ng /6/Kch tht hnh hc /6/Tc trung bnh ca mng nc trn ng /6/Chun s Chn t s gia s bc ng v ng knh ng 1,7 2, ta c Chun s/6/ H s ta nhit pha nc Mt dng nhit v pha nc Trong mgml000479 , 0... 94 . 1 32 m d 001917 , 0 . 4 s mml/ 4198 , 0. 005 , 1095.Re d564 , 17 Pr . Re . 1 , 0048 63 . 0 NuK m WdNu. / 756 , 5735.22 +iintq221Cttt ttotb383 , 6ln121 2 27 N K THUT LNHNhm 4ng knh trong ca ngdt = 50 mm ng knh ngoi ca ngdn = 57 mmH s truyn nhit nhit ca vt liu lm ng (thp)= 45,3 W/m.KNhit tr ca lp du, vch, bn, cn Ta c phng trnh mt dng nhit pha ngoi ngb. Din tch b mt truyn nhit Ph ti nhit ca thit b ngng t Trong Nng sut nhit ring qk = 1392,857 KJ/KgLu lng khi lng thc t ca mi cht lnh mtt = 0,282 Kg/sTng din tch b mt truyn nhit pha trong ng Tng din tch b mt truyn nhit pha ngoi ngLng nhit tn tht ra mi trng khng kh /6/Trong Entanpi ca mi trng khng kh xung quanhh1 = 75,24 KJ/Kgkkk(tra gin khng kh m 35oC, m khng kh 50%)Entanpi ca khng kh bo ha htb = 133,76 KJ/Kgkkk(tra gin khng kh m nhit trung bnh ca nc)H s lu lngVi H s ta nhit i lu v pha khng kh kk = 20 W/m2.KNhit dung ring trung bnh ca khng kh Cpk = 1020 W/m2.KW K mccbbvvddii/ . 00115 . 05 . 110 6 . 058 . 010 1 . 03 , 4510 5 ., 312 . 010 06 . 023 3 3 3+++ + + + ( ) 67 , 342 2 + v v k tb tb k v vt t t t t t t t t t( ) ( ) 1 617 , 34 . 0902 , 755 v nt qKW q m Qk tt k61 , 392 . 21197 , 95 mqQFtk 2221272 , 123.mdd FFtn KW h h F Qhb kk92 , 283 ) ( . .1 2 s m KgCpkkk. / 0196 , 02 28 N K THUT LNHNhm 4H s k n s tng b bay hi do to thnh cc tia v git = 2Khi lng nc bay hi /6/Trong m ca khng kh bo ho xtb = 0,036Kg/Kg(Tra nhit trung bnh ca nc) m ca khng kh x1 = 0,014 Kg/Kg(Tra nhit khng kh xung quanh)Nhit tiu tn cho qu trnh bay hi lng nc MbTiu hoa nc ti trong thit b ngng tTrong Nhit dung ring ca ncCp = 4,18KJ/KgNhit nc rat2 = 36oCNhit nc vot1 = 33oCLng nhit m nc nhn c khi chy qua gin xi tiT s gia lng nc b sung v lng nc tiu tnLng nc b sungMbs = 7,49 Kg/sLng nc thi Cc kch tht c bn ca thit bS cm ngn = 8 cmTng chiu di ca tt c cc cmTng chiu di ca ng trong mt cmChiu di ca mi ng thngl = 2,5 mTng s ng trong mt cmChn Nng = 31 ng s Kg x x F Mtb b/ 107 , 0 ) .( . .1 2 KW t C M Qpn b bh06 , 16 . .2 s Kg Mt CQMbp/ 49 , 7. +KW Q Q Q Qbh kk k63 , 92 12 Wbst ttMMs Kg M M Mb bs t/ 39 , 7 mdFLn89 , 690.2 mnLL 765 , 761 71 , 301 lLNong29 N K THUT LNHNhm 4Bc ng cc n nguyn s = 1,7 x dn =0,969 m304.1.6.Tnh chn thit b bc hi (kiu xng c)a. Dng nhit pha ngoi gin lnh th 3: th biu din s bin i nhit ca cc dngKhi qua thit b bc hiNhit nc mui votm1 = -9oCNhit nc mui ratm2 = -11oCNhit bc hi to = -15oCHiu nhit trung bnh ng knh ngoi ca ngdng = 45 mmng knh trong ca ngdt = 40,5 mmGc nghing ca ng= 20oBc ng ngangS1 = 0,1 mBc ng dc S2 = 0,2 mCc thng s ca nc mui NaCl 23,1% nhit trung bnh -10oCKhi lng ring= 1175 Kg/m3 nht ng lc hc = 4,71 x 10-3Pa.s nht ng hc = 4,008 x 10-6m2/sH s dn nhit = 0,539 W/m.Nhit dung ringCm = 3,01 KJ/Kg.Chun s Vn tc ca dngnc mui chy qua thit b bc hi3 , 26.Pr mCaCttt ttotb641 , 3ln121 2 N K THUT LNHNhm 4V = 0,6 m/s/3/ (trong khong 0,4 0,7 m/s)Chun s ch chy qu Chun s Theo ti liu [4]Trong z = 1 l h s xt n nh hng ca th t ng H s cp nhit pha cht ti lnhMt dng nhit pha cht ti lnh Cng thc 8.3 [5]Trong : tng nhit tr ca vch v cc lp du, bn, cnVi: h s dn nhit ca vt liu lm ng (thp) = 45,3 W/m.KPhng trnh dng nhit pha nc muib. Din tch b mt truyn nhitNng sut lnhQo = 308,05 KWDin tch b mt truyn nhit H s truyn nhitTng chiu di ca ng Chn chiu di ca mt ngl = 2,05 mS ng trong thit bChn N = 771 ng S ng trong 1 lp n = 3667 , 6735.Re ngd91 , 192 . Pr . Re . 3 . 036 . 0 6 . 0 zNu K m WdNngung s. / 604 , 23102. +iing sfng stq..1W K mccbbvvddii/ . 00112 , 05 . 110 6 . 058 . 010 1 . 03 , 4510 25 , 212 . 010 06 . 023 3 3 3+++ + + + v v tb o v f ft t t t t t t + 359 , 11( ) ( ) 1 395 , 11 . 1406 , 634v nt q 268 , 222 mqQFnong K m Wt FQKtb ngo. / 946 , 397.2214 , 1575.mdFLngng 36 , 768 lLN32 N K THUT LNHNhm 4Tng s lp trong thit bS lp trong 1 tp nlp1 = 32lpS tp trong thit b03 , 81 loploptepnnNtpChn Ntp = 8 tpKhong cch gia 2 tp 0,1 mChiu di ca thit bL = 2.+ (nlp1 1 ).s2 = 6,6 mVikhong cch gia 2 u = 0,2 mB rng ca thit bL1 = 0,1 x 8 = 0,8 m4.1.7. Cc thit b khca. ng ngYu cu vi vic tnh ton v la chn ng ng l bn cn thit v tit din ca ng phi m bo yu cu k thut v kinh t. Chnvt liucangngtronghthnglthp. Vickimtrabnl khng cn thit. Thng ng c th chu c p lc n 3MPa.Ta cn chn ng knh ca: ng ht ca my nn hi. ng y ca my nn hi. ng dn lng ca my lnh.Ta c th tnh ton ng knh trong ca ng dn theo biu thc . .. 4 mdi Cng thc 10 1 [3] Khi lng ring ca mi cht lnh. Kg/m3di ng knh trong ca ng dn. mmm Lu lng mi cht trong h thng. Kg/s Vn tc ca dng chy trong ng. m/snNnlop257 33 N K THUT LNHNhm 4ng y ng ht ng dn lngm 0,282 8,3 1,82 580 20 15 0,5di46,5 114,7 35,2Chn ng knh ng dn bng thp theo tiu chun ca Ngang knhdanh nghaDy, mmng knhngoiDa, mmng knh trongDi,mmChiu dy vch ngmmTit din ng,mm2Khi lng 1m ngKgng y 50 57 50 3,5 1960 4,62ng ht 125 133 125 4 12300 12,73ng dn 40 45 40,5 2,25 595 1,65Mu sn quy nh cho cc ng ng ng y: mu . ng ht: mu xanh da tri. ng dn lng: mu vng. ng dn nc mui: mu xm. ng dn nc: mu xanh l cy.b. Bnh tch lngNhim v: tch lng ra khi dng hi v my nn, m bo my nn ch ht hi khng ht lng gy va p thy lc, dn n h hng my nn.Cu tov v tr: bnh tch lng l mt bnh hnh tr bng thp, c b tr trn ng ht v my nn, gia gin lnh v my nn. Bnh tch lng c t cao hn gin bay hi, c bc cch nhit nhm gim tn hoa nhit v trnh hin tng ng sng.Nguyn l hot ng: do s gim vn tc t ngt ( 15m/s xung 0,5 m/s), cc git du v lng b tch ra khi dng hi. Dng ra khi bnh tch lng hu nh hon ton l hi kh.p sut ti a cho php ca bnh tch lng l 1,5 MPa, nhit t -50 n 40oC.Chn: ta chn bnh tch lng da vo ng knh ng ht ca my nn.34 N K THUT LNHNhm 4Bnh tch lngKch tht, mm Khi lng Kg DbnhDiB H125 0 600 125 1080 2100 313c. Bnh tch duNhim v:my nn hot ng cn c du bi trn cho pitong. Do , khi my nn hot ng, nn mi cht lnh NH3, lun c mt phn du ha ln vo mi cht lnh. NH3 khng ha tan du, chng phn lp.Du theo mi cht lnh, nu khng c tch ra, i vo thit b ngng t v bm ln thnh ng trao i nhit, hn ch qu trnh trao i nhit ca thit b. Bnh tch du c nhim v, tch phn du ln trong mi cht lnh trc khi n i vo thit b ngng t.Cu to v v tr: bnh tch du l mt ng thp t ng, c tm i hng chuyn ng ca dng pha trong. Bnh tch du c t trn ng y ca my nn, trc thit b ngng t v sau my nn.Nguyn tc hot ng:dng mi cht lnh c ln du i vo bnh, vn tc ca dng b gim t ngt (20m/s xung 0,7 m/s), mt khc dng cn b thay i hng t ngt, cc git du ln trong dng mi cht lnh b tch ra khi dng ri xung y bnh, ri chy vo bnh cha du.Chn: ta chn bnh tch du da vo ng knh y ca my nn.ng knh ng ht,mmng knh bnh mmChiu cao bnh mmKhi lng Kg125 600 2100 313d. Bnh cha duNhim v:gom du t bnh tch du, gim nguy him khi x du v gim tn tht mi cht khi x du ra khi h thng lnhCu to v v tr: bnh cha du l bnh thp c dng hinh tr t ng hoc t nm, c ng ni vi bnh tch du, ng ni vi ng ht ca my nn. p sut trong bnh c bo bng p k gn trn bnh.Khi m van vi ng ht, p sut trong bnh c th gim xung gn bng p sut kh quyn. Khi x du p sut trong bnh ch c php ln hn p sut kh 35 N K THUT LNHNhm 4quyncht t, tt cccvanphi ng. psut caonht chophpcabnhl 1,8MPa, nhit t -40oC n 150oC.Bnh cha duKch tht, mmTh tch, m3Khi lng, KgDbnhB H300CM 325 765 1270 0,07 92e. Bnh cha cao p Nhim v: Cha lng cao p sau ngng t, trc tit lu, nhm gii phng b mt truyn nhit cho thit b ngng t v duy tr s cp lng thng xuyn cho van tit lu.Cu to v v tr:H thng lnh ca ta thuc loi ln, nn bnh cha cao p c chn l mt bnh hnh tr c t nm ngang. Bnh c tnh ton lm vic vi p sut 1,8 MPa.Bnh c t pha sau v thp hn thit b ngng t.Chn: Theo quy nh v an ton th bnh cha cao p phi cha c 30% th tch ca ton b h thng dn lnh bay hi trong h thng lnh c bm cp mi cht lng t trn v 60% th tch dn trong h thng lnh cp lng t di ln. Khi vn hnh mc lng trong bnh cao p ch c php chon 50% th tch bnh.Sc cha ca bnh cha cao p i vi h thng lnh cp lng t di: ( )363 , 3 5 , 2 45 , 1 . 45 , 1 . 45 , 1 . 45 , 1 m V V V V Vtd KK td d CA + Vi dung tch ca t dn:Vtd = L.V = 1575,146 x 1,59 x 10-3 = 2,5 m3Trong : Chiu di ng trong t dn L = 1575,146 mDung tch ca 1 m ngm mdVn/ 10 59 , 14.3 32 Loi bnhKch tht, mm Dung tchm3Khi lngKg D L H3,5PB 1000 4890 950 3,5 1455f. Thit b tch kh khng ngng36 N K THUT LNHNhm 4Cng tun hon vi mi cht lnh trong h thng lnh c khng kh v cc loi kh khng ngng. Thnh phn ch yu ca kh khng ngng trong h thng vn l khng kh. Khng kh lt vo h thng do nhiu nguyn nhn: Khi tin hnh sa cha. Khi ht chn khng h thng, chn khng cha m bo yu cu. Khi h thng lm vic ch chn khng v nhit si thp. Khi np mi cht v np du. Do phn hy mi chtNhim v: trong thit b ngng t, khng kh to lp bao quanh b mt trao i nhitlmtngtrnhit, dnnlmgimhiuqutraoi nhit. Mtkhc, kh khng ngng cn lm tng p sut ngng t v nhit cui tm nn. Chnh v vy, ta cn c thit b tch kh khng ngng ra khi h thng theo nh k.Cu to v v tr: gm 2 ng lng vo nhau, t trn bnh cha cao p.Hot ng: mi cht NH3 i qua van tit lu vo ng trong ca thit b, mi cht NH3 bay hi nhit thp. Hn hp kh khng ngng v mi cht i vo ng ngoi ca thit b, tip xc vi ng trong, mi cht ngng t, tr v bnh cha cao p, kh khng ngng c cho thot ra ngoi.g. Phin lc v phin syNhim v: tch cc cn bn v cc tp cht khc nh nc, axitra khi dng mi cht nhm trnh: Tc ng dn nht l tc van tit lu. Cc chi tit chuyn ng ca my b bo mn. Tc van tit lu do nc ng bng.Cu to : thn ca phin lc c dng hnh tr bng thp. B phn lc v sy ca phin ch l mt khi zeolite c t c nh trong phin.V tr lp t: Phin lc ng hi, c b tr trn ng ng ht trc my nn. Phim lc ng lng, c b tr trn ng lng pha trc van tit lu.37 N K THUT LNHNhm 4h. Mt gasNhim v: mt gas c mt s nhim v sau: Quan st dng mi cht chuyn ng pha trong h thng. Quan st bit lng gas pha trong h thng: Nu gas, khng si bt kh pha trong mt gas. Nu thiu gas, si bt kh mnh pha trong mt gas. Nu ht gas ta s thy cc git du bm trn knh. Quan st bit m ca dng mi cht, bng cch so snh mu ca chm mu tm mt gas vi cc mu chu vi mt gas: Xanh: kh. Vng: thn trng. Nu: m.Nu dng mi cht b m, ta phi thay phin sy mi. Quan st bit tnh trng cc ht zeolite trong phin sy, nu mt gas b vy c iu c ngha l cc ht zeolite b phn r bn trong phin sy, khi ta phi thay phin sy trnh hin tng b ngt van tit lu.Cu to: mt gas l mt ng hnh tr, pha di c bt kn, pha trn gn mt gas quan st dng mi cht pha trong.V tr lp t: mt gas c lp trn ng lng, pha sau phin sy, pha trc van tit lu.i. Cc loi van:- Van kha, van chn:c lp trn ng ht, ng y ca my nn, pha trc p k v cc thit b khc, vi mc ch kha cho h thng c kn trong iu kin sa cha hay thay th cc thit b.38Hnh : Van mt chiu hnh ccHnh : Van mt chiu hnh nm N K THUT LNHNhm 4- Van mt chiuVan mt chiu ch cho dng chy theo mt hng. Van c lp trn ng y ca my nn, nm gia my nn v thit b ngng t, c nhim v ngn khng cho mi cht chy ngc tr li my nn, trong trng hp phi dng my nn sa cha.Ngoi ra van mt chiu cn c lp trn ng dn kh khng ngng ra ngoi khng kh, ngn khng cho chng quay ngc tr li thit b tch kh khng ngng.Van hot ng da trn nguyn tc chnh lch p sut. Khi p sut u vo ln hn p sut u ra, van s t ng m cho dng hi i qua. - Van an tonVan an ton c lp nhng thit b c p sut cao v cha nhiu mi chy lng nh thit b ngng t, bnh cha cao p. Van cng hot ng da trn chnh lch p sut ging van mt chiu, nhng khc l chnh lch p sut phi t nhng tr s nht nh. Van c dng phng khi p sut trong cc thit b vt qu mc quy nh, lc van s t ng m ra x mi cht ra ngoi khng kh.- Van tit lu tay1 thn; 2 ; 3 tm van, kim van; 4 m kn; 5 chn m; 6 trc; 7 tay quayhnh: van thng hnh: van gc39 N K THUT LNHNhm 4Van tit lu tay l mt b phn ca thit b tch kh khng ngng. Mi cht lnh qua van, p sut gim t Pk xung Po, nhit bc hi ca mi cht lnh lc ny l to. Nh vy khi hn hp hi (mi cht lnh v kh khng ngng) tip xc vi ng tr cha n, trao i nhit, mi cht lnh ngng t tr v bnh cha cao p.- Van tit lu nhit cn bng ngoi Van tit lu nhit hay cn gi l van tit lu iu chnh t ng nh qu nhit ca hi ht v my nn. C 2 loi: Van tit lu nhit cn bng trong: dng cho h thng lnh nh. Van tit lu nhit cn bng ngoi: dng cho h thng lnh ln.Van tit lu nhit cn bng ngoi, c mt ng c b tr st vi u ht ca my nn. Khi p sut di mng n hi l Ph. Nu ti nhit ca dn bay hi ln hay mi cht lnh vo dn bay hi t, qu nhit ca hi ra khi dn tng, p sut pha trn mng n hi tng, y kim van xung pha di, m ca van, mi cht lnh vo nhiu hn.V ngc li. /7/.- Van in tL loi van iu chnh ON OFF. Ly tin hiu p sut, nhit hay mc lng ng m van.j. p kc dng do p sut ca mi cht bn trong ng ng v thit b. p k c lp trn ng ht, ng y ca my nn, trn thit b ngng t, bnh cha cao pCc p k chuyn dng cho h thng lnh c cc thang chia nhit si bo ha tng ng ca mi cht lnh.k. Cnh khuyQut khut nc mui dng khuy trn v tun hon nc mui trong b. Mc ch, tng cng trao i nhit gia nc mui v dn bay hi, gia b mt khun v nc mui, lm ng u nhit trong b nc 40 N K THUT LNHNhm 4mui, lm ng u s ng trong khun. Tnh chn cnh khuy theo ti liu /8/Chn cnh khuy c ng knhdk = 760mm.Tc vng quay ca cnh khuy n = 3vng/s.Chn ng knh ng dn hng dng D = 1200mmH s ng dng hnh hc ca thit b khuy 58 , 17601200 kDdDGChun s 2 2. . .Rek kkd n d n = 5,7 x 10-3 T trn ta c th tra th v nhn c h s cng sut khuy KN = 0,45.Cngsut khuyN = KN. . n3. dk5 = 0, 45. 1175. 33. 0, 765 = 3619,78 W = 3,62 KW.Cng sut ca ng c:N = K. N/= 4,68 KWTrong : H s tr cng sut chn K = 1,1.Hiu sut s dng = 0,85.Chn ng c 3 pha c cng sut theo tiu chun 5 KW.h. B tr lp t /9/41 N K THUT LNHNhm 44.2. Tho lunT trc n nay, ni n nc ai cng bit,ni n lm nc th ngi ta ch ngh n gin l h nhit xung thp nc ng bng, nhng lm c iu th i hi ngi k s phi tnh ton v thit k ra c nhng thit b lm lnh, v phi m bo nhng tiu chun ca nc .Trn thc t nu mun xy dng thnh cng mt nh my nc , n i vo hot ng c hiu qu th ngi k s khng phi ch c kin thc v k thut m i hi phi tnh n tnh kinh t khi xy dng mt phn xng nc .Vi kt qu tnh ton trn ta c th thy tnh kh thi v mt k thut cn v vn kinh t th ti vn cha thc hin c.42Chng 5KT LUN V NGH5.1. Kt lun ti c nhm 4 thc hin hon tt theo yu cu t ra, theo phng php tng hp, tnh ton v k tha nn ti vn cn nghin v mt l thuytthiu phn sng to ci tin h thng my cy.5.2. nghTrong qu trnh thc hin ti, v nhiu l do v thi gian v cc iu kin cho php nn nhm thc hin ti vn cha hon thnh hon chnh, vn cn nhiu thiu xt. ngh : nhm 4 cn ciu kin v thi gian c th kho nghimcc h thng my cy nhm hiu su hn v c th so snh gia l thuyt v thc nghm ti u ha h thng trong thit k v lp t. TI LIU THAM KHO/1/. Nguyn c li Phm Vn Ty inh Vn Thun, k thut lnh ng dng, NXB Gio Dc, 363 trang, thng 6/2007./2/. Trn c Ba Nguyn Tn Dng (ch bin), cng ngh lnh, tp 1, NXB i Hc Quc Gia, 537 trang, 2007./3/. Nguyn c Li, hng dn thit k h thng lnh, NXB Khoa Hc v KThut, 402 trang, 2006./4/. Nguyn Cng Minh, Lun Vn Tt Nghip: thit k xng sn xut nc khi, Trng i Hc Bch Khoa Thnh Ph H Ch Minh, 112 trang, 2001./5/.Nguyn c Li Phm Vn Ty, k thut lnh c s, NXB Gio Dc, 379 trang, 2007./6/.Nguyn c Li, Phm Vn Ty, Bi tp k thut lnh, NXB Gio Dc, 227 trang, 1996./7/. Nguyn c Li, T ng ha h thng lnh, NXB Gio Dc, 319 trang, 2003./8/. Trng Hong Minh, Thit k nh my sn xut nc cy 120 tn/ 24h v kho bo qun dung tch 120 tn, n chuyn ngnh, i hc Nha Trang, 2008./9/. NGUYN VN PHC, Bi tp ln thitk b khi (50kg)nng sut 40 tn/ngy m, H Quc Gia TP HCM, Trng H Bch Khoa, 2009. /10/. GS.TSKH. Trn c Ba, Ts. Trn Thu H, Ts. Nguyn Vn Ti, Th.s Hu Hon, Th.s L Quang Lim, Gio trnh k thut lnh i cng, Trng H Cng nghip TP HCM khoa cng ngh nhit lnh, nh xut bn H Quc gia TP HCM, 2009