n thit k kho lnh bo qun tri cy nng sut 120 tn

n thit k kho lnh bo qun tri cy nng sut 120 tn

TRNG I HC CNG NGHIP THC PHMTP. H CH MINHKHOA CNG NGH HA HCB MN QU TRNH V THIT B

----------

N MN HC QU TRNH V THIT B

TI:

THIT K H THNG KHO LNH BO QUN TRI CY NNG SUT 120 TN

GVHD: TH.S O THANH KHSVTH: NGUYN HONG LINHMSSV: 2004110090LP: 02DHHH1

Tp.H Ch Minh - Thng 6/2014

LI M U Tri cy l loi thc phm khng th thiu trong i sng hng ngy. y l ngun cung cp vitamin v khong cht cn thit cho c th . Nc ta l mt nc nhit i vi loi cy tri quanh nm . Tuy nhin chnh thi tit nng m li l nguyn nhn lm cho tri cy rt d b h hng khi tin hnh thu hoch theo thi v. Do vn t ra l lm sao bo qun sn phm tri cy c lu di . Phng php hiu qu nht hin nay l bo qun tri cy trong phng lnh . Theo phng php ny , tri cy sau thi gian di bo qun vn cn gi c cht lng tng i tt . ti Thit k h thng kho lnh bo qun tri cy qu nng sut 120 tn. Do thi gian v kin thc cn hn ch nn khng trnh khi nhiu sai st . Em rt mong nhn c nhng ng kin ca cc thy c ti c hon thin hn.Em xin chn thnh cm n! TP. H Ch Minh, ngy 10 thng 06 nm 2014

LI CM N Sau mt thi gian nghin cu v tham kho hon thnh n, em xin chn thnh cm n:Trng H Cng Nghip Thc Phm 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 n trong thi gian ngn.Th vin trng cung cp nhng t liu ht sc c gi tr, l ti liu thanh kho tt v qu bu.c bit gi li cm n n thy o Thanh Kh, ngi trc tip hng dn tn tnh nhm chng em hon thnh n ng thi hn.TP. H Ch Minh, ngy 10 thng 06 nm 2014

LI NHN XT CA GVHD

Ch k ca gio vin nhn xt

LI NHN XT CA HI NG PHN BIN

Ch k ca gio vin nhn xt

MC LC

CHNG 1: TNG QUAN81.1 NGHA V MC CH CA H THNG LNH81.2NI DUNG V YU CU THIT K8CHNG 2: TNH TON KHO LNH92.1TNH TH TCH KHO LNH92.2DIN TCH CHT TI TRONG KHO LNH92.3TI TRNG NN102.4DIN TCH KHO LNH CN XY DNG10CHNG 3: TNH TON CCH NHIT CCH M113.1TNH TON CHO VCH KHO LNH113.1.1 Kt cu tng bao113.1.2 Xc nh b dy lp cch nhit113.1.3 Kim tra ng sng123.2CCH NHIT CCH M CHO NN123.2.1 Kt cu cch nhit ca nn123.2.2 Xc nh b dy lp cch nhit133.3.1 Kt cu cch nhit ca trn143.3.2 Xc nh b dy lp cch nhit14CHNG 4: TNH TON CN BNG NHIT144.1TNH DNG NHIT TN THT154.1.1 Tnh nhit tht thot qua vch154.1.2 Tnh dng nhit do sn phm to ra164.1.3 Dng nhit do vn hnh kho184.1.4 Dng nhit do thng gi bung lnh194.2XC NH TI NHIT CHO THIT B V MY NN20CHNG 5: TNH TON CHU TRNH LNH, TNH CHN MY NN215.1CHN CC THNG S CA CH LM VIC215.1.1 Nhit si ca mi cht lnh215.1.2 Nhit ngng t215.1.3 Nhit hi ht (th)225.1.4 Nhit qu lnh (tql)235.2TNH TON CHU TRNH LNH245.2.1 Nng sut lnh ring khi lng245.2.2 Lu lng mi cht qua my nn245.2.3 Nng sut th tch thc t ca my nn..................245.2.4 H s cp ca my nn245.2.5 Th tch ht l thuyt255.2.6 Cng nn on nhit255.2.7 Cng nn ch th265.2.8 Cng sut ma st265.2.9 Cng sut hu ch265.2.10 Cng sut in275.2.11 Cng sut ng c lp t275.2.12 Ph ti nhit dn ngng275.3TNH CHN MY NN275.4TNH CHN THIT B NGNG T285.5TNH CHN THIT B BAY HI31CHNG 6: CC THIT B KHC CA H THNG336.1BNH CHA CAO P336.1.1 Cng dng336.1.2 Cu to336.2THP GII NHIT346.2.1 Mc ch346.2.2 Cu to346.2.3 Nguyn l356.2.4 Tnh ton356.3.1 Mc ch366.3.2 Cu to366.3.3 Nguyn l lm vic376.4BNH CHA DU376.4.1 Nhim v376.4.2 Cu to376.5BNH TRUNG GIAN386.5.1 Mc ch386.5.2 Cu to386.6.1 Mc ch396.6.2 Cu to396.7PHIN SY LC406.8MT GAS406.9VAN41

CHNG 1: TNG QUAN

1.1 NGHA V MC CH CA H THNG LNHT xa xa con ngi bit s dng lnh cho i sng, bng cch cho vt cn lm lnh tip xc vi nhng vt lnh hn. Sau ny k thut lnh ra i thm nhp vo cc ngnh kinh t quan trng v h tr tch cc cho cc ngnh nh: Ngnh cng ngh ch bin v bo qun thc phm Trong cng nghip nng: lm ngui khun c Trong y t: ch bin v bo qun mu, thuc Trong cng ngh ha cht Trong lnh vc sinh hot i sng: iu ha khng khng vai tr quan trng nht l ngnh cng nghip ch bin v bo qun thc phm. Tuy nhin c th gi cho thc phm c lu di cung cp, phn phi cho nn kinh t quc dn, th phi bo qun ng nhm gi cho cc vi sinh vt lm i thiu thc phm cng b c ch, cc qu trnh phn gii din ra rt chm. V vy m c th gi cho thc phm khng b hng trong thi gian di.1.2NI DUNG V YU CU THIT K1. Bo qun mt Sn phm bo qun: tri cy Dung tch: 120 tn Nhit kho lnh bn qun: 4oC Nhit ngng t: 25oC2. Thng s mi trng a im xy dng: kho lnh t ti Tp.HCM Nhit mi trng: tn=37,3oC m mi trng: 3. Mi cht lnh Mi cht lnh s dng trong kho lnh bo qun l R22CHNG 2: TNH TON KHO LNH

2.1TNH TH TCH KHO LNHTh tch kho lnh c xc nh theo cng thc:V = (m3)

Trong : V Th tch kho lnh , m3.E Dung tch ca cc bung lnh, tn.gv Mc cht ti, tn/m3. Kho c thit k vi mt hng tri cycha trong thng g, ta c gv = 0,45 tn/m3 Dung tch tht s cc bung sn phm l tri cy Espv thng g EbbChn Ebb =10% Esp Esp = 120 (t) (u )Dung tch tht s ca bung lnh E = Esp + Ebb = 120 + 12 = 132 (t)Th tch bung lnh

V = (m3)2.2DIN TCH CHT TI TRONG KHO LNHChn h = 3 mCng thc xc nh din tch cht ti bung lnh:F= (m2)

Trong :h Chiu cao cht ti, m

2.3TI TRNG NNCng thc tnh ti trng nn:gf = gv h = 0.45 x 3 = 1.35 ( tn/m2)

Trong : h Chiu cao cht ti. gv Mc cht ti, tn/m32.4DIN TCH KHO LNH CN XY DNGCng thc xc nh din tch xy dng kho lnh:Fxd= ( m2)

Trong : F H s s dng din tch xy dng ca kho lnh, F ph thuc vo kchthc ca bung lnh.i vi bung din tch nh hn 100 m2, F = 0,700,75i vi bung din tch 100- 400 m2, F = 0,750,80i vi bung din tch hn 400 m2, F = 0,80,85Chn kch thc kho lnhDin tch bung lnh quy chun (bi ca 36 m2) nn chn Fxd = 144 m2 (1212)Chn kch thc kho nh sau: 12 x 12 x 5

CHNG 3: TNH TON CCH NHIT CCH M

3.1TNH TON CHO VCH KHO LNH3.1.1 Kt cu tng baoXy dng vch kho lnh c kt cu nh sau:Bng 1: Kt cu vch ngoi kho lnhVt liuB dy(m)H s truyn nhit (W/m.K)

Va0.0200.800

Gch0.3800.820

Va0.0200.800

Cch m bitum0.0040.300

Cch nhit polystirol0.2000.047

Lp va v tm thp0.0200.880

Cng0.624

3.1.2 Xc nh b dy lp cch nhitB dy lp cch nhit c tnh theo cng thc:

Trong :1 = 23.3 W/m2 .K : h s cp nhit ca khng kh bn ngoi (tng c chn gi). 2 = 9 W/m2.K : h s cp nhit ca khng kh trong phng (i lu cng bc).i : b dy ca vt liu lm tng (bng 1).i : h s truyn nhit ca vt liu lm tng (bng 1).K = 0.35 W/m2.K : h s truyn nhit quy chun.

=> chn 1 = 0.2 m

H s truyn nhit K

K = 0.202 W/m2.K3.1.3 Kim tra ng sngiu kin vch ngoi ca kho lnh khng b ng sng:

Trong :t1: nhit bn ngoi kho bo qun lnh ng (oC)ts: nhit ng sng ca khng kh bn ngoi (oC)t2: nhit bn trong kho lnh (oC)1: h s cp nhit ca khng kh bn ngoi (W/m2.K)0.95 : h s an ton

=> K < ks

Vy: vch ngoi khng ng sng.

3.2CCH NHIT CCH M CHO NN3.2.1 Kt cu cch nhit ca nnKt cu nn kho lnh ph thuc vo nhiu yu t nh: nhit phng lnh, ti trng ca hng bo qun, dung tch kho lnh,Yu cu ca nn l phi c vng chc cn thit, tui th cao, khng thm m.

Bng 2: Kt cu cch nhit ca nnVt liuB dy (m)H s truyn nhit (W/m.K)

Btng t0.021.6

Btng tm0.101.0

Cch nhit (Stiropor)0.200.047

Cch m bitum0.0050.23

Va0.010.88

Btng ct thp0.151.5

Cng0.485

3.2.2 Xc nh b dy lp cch nhitB dy lp cch nhit c tnh theo cng thc:

Trong : 1 = 23.3 W/m2 .K : h s cp nhit ca khng kh2 = 9 W/m2 .K : h s cp nhit ca khng kh trong phng (i lu cng bc).i : b dy ca vt liu lm tng (bng 2).i : h s truyn nhit ca vt liu lm tng (bng 2).K = 0.35 W/m2 .K : h s truyn nhit quy chun.

=> chn 2 = 0.2 m => H s truyn nhit ca nn K = 0.215 W/m2 .K Kim tra tng t trn ==> khng c ng sng v ng m.

3.3CCH NHIT CCH M CHO TRN3.3.1 Kt cu cch nhit ca trnMi kho lnh khng c php ng nc v thm nc.Mi c kt cu nh sau:Bng 3: Kt cu cch nhit ca trn kho lnhVt liuB dy (m)H s truyn nhit (W/mK)

Btng ct thp0.071.5

Va0.010.88

Bitum0.0050.23

Cch nhit (Stiropor)0.150.047

Va trn li thp0.040.88

Cng0.1957

3.3.2 Xc nh b dy lp cch nhitB dy lp cch nhit c tnh theo cng thc:

Trong :1 = 23.3 W/m2 .K : h s cp nhit ca khng kh bn ngoi (tng c chn gi). 2 = 9 W/m2 .K : h s cp nhit ca khng kh trong phng (i lu cng bc). i : b dy ca vt liu lm tng (bng trn). i : h s truyn nhit ca vt liu lm tng (bng trn). K = 0.35 W/m2K : h s truyn nhit quy chun.

=> chn 3 = 0.2 m => H s truyn nhit ca trn K = 0.288 W/m2.KKim tra tng t trn ==> Khng c ng sng ng m trn b mt kt cu.

CHNG 4: TNH TON CN BNG NHITVic tnh ton nhit ti kho lnh l tnh ton cc dng nhit t mi trng xm nhp vo kho lnh. y chnh l dng nhit tn tht m my lnh phi c cng sut thi 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. Dng nhit tn tht vo kho lnh c xc nh bng biu thc: Q = Q1 + Q2 + Q3 + Q4 (W)

Trong :Q1: dng nhit tht thot qua vch.Q2: dng nhit do sn phm ta ra.Q3: dng nhit do vn hnh kho.Q4: dng nhit do thong gi bung lnh.4.1TNH DNG NHIT TN THT4.1.1 Tnh nhit tht thot qua vchBao cheK (w/m2k)F(m2)T (k)Q1 =KFT (w)

Tng ngoi0.2026062.3755.076

Tng ngoi0.2026062.3755.076

Tng ngoi0.2026062.3755.076

Tng ngoi0.2026062.3755.076

Nn0.21514462.31928.808

Trn0.28814462.32583.7056

Tng Q17532.8176 (w)

4.1.2 Tnh dng nhit do sn phm to ra Dng nhit do tri cy ta ra:

M: nng sut bung bo qun lnh ng (t/24h)Q21 :Dng nhit do tm ta rah1 ,h2 : enthapi ca sn phm trc v sau khi x l lnh :Theo bng 4-2 p.81 Chn nhit hng nhp thng vo kho bo qun lnh ng l:t1 = 8 oC h1 = 302 kJ/kgt2 = 4 oC h2 = 286.7 kJ/kgM = 8%E = 0.08120 = 9.6 ( t/24h)Vi: M: khi lng hng nhp vo bo qun lnh ngE: dung tch phng bo qun lnh ngVy : Dng nhit do tri cy h hp:Q22 = E (0.1qn + 0.9qhp) ,W =120 (0.140.7 + 0.914) = 1667 (W)Vi:E : dung tch kho lnhqn v qhp :dng nhit ta ra khi c sn phm nhp vo kho lnh, sau l nhit bo qun kho lanh . W/t (bng 4-5) Dng nhit do bao b ta ra:

Vi: Mb : khi lng bao b a vo cng sn phm (t/24h)Cb : Nhit dung ring ca bao b (kJ/kgK)t1, t2 : nhit bao b trc v sau khi bo qun lnh ng1000/(243600) : h s chuyn i t/24h ra kg/sTa c :Khi lng bao b g : Mb = 10%M = 10% 9.6 =0.96 (t/24h)Nhit dung ring ca bao b g : Cb = 2.5 (kJ/kgK)Nhit bao b trc khi bo qun: t1= 8 oCNhit bao b sau khi bo qun : t2 =4 oC

Tng nhit do sn phm ta ra l :Q2 = Q21 + Q22 + Q23 = 1700 + 1667 + 111.11 = 3478.11 (W)4.1.3 Dng nhit do vn hnh kho Dng nhit do n chiu sang:Q31 = AF ,W A: nh mc chiu sng trn mt m2 phng, A = 1.2 W/m2 F: Din tch phng lnh, F= 144 m2Q31= 1.2144 = 172.8 W

Dng nhit do ngi ta ra:Q32= 350n ,W350: nhit lng do ngi ta ra khi lm vic nngn: s ngi lm vic trong phng, chn n=3Q32= 3503 = 1050 W Dng nhit do ng c in:Q33= 1000N ,WN: cng sut ng c in , N = 2 Q33= 10002= 2000 W Dng nhit khi m ca:Q34 = BF ,WB: dng nhit do tn tht kho lnh m ca cho 1 m2 phng lnh, B= 15 (tra bng 4-4)F: din tch phng lnh, F = 144 m2Q34= 15144 = 2160 WVy dng nhit vn hnh:Q3 = 172.8 + 1050 + 2000 + 2160 =5382.8 (W)4.1.4 Dng nhit do thng gi bung lnhTra th h-x ta c : h1 =105 kj/kg h2 =13 kj/kgKhi lng ring ca khng kh trong bung pk=1.28m3/kgBi s tun hon khng kh a=3

Dng nhit tn tht do khng kh nng a vo:Q4 = Mk (h1-h2)1000 = 6.410-3 (105-13)1000 = 588.8 (W)Dng nhit tn tht cho ton b kho Q= Q1 + Q2 + Q3 + Q4 = 7532.82 + 3478.11 + 5382.80 + 588.80 = 16982.53 W 4.2XC NH TI NHIT CHO THIT B V MY NNTi nhit cho thit b l tng cc ti nhit thnh phn c gi tr cao nht :QMN = Q1 + Q2 + Q3 + Q4 + Q5 W (4-15) (NL) QMN =7532.82 + 3478.11 + 5382.80 + 588.80 = 16982.53 (W)Nng sut lnh ca my nn c xc nh theo biu thc:

Q0= (4-17) (NL)Q - Tng nhit ti ca my nnb - L h s thi gian lm vic, chn b= 0.9 k - L h s tnh n tn tht trn ng ng v thit b ca h thng lnh, ly k=1.12 (dng phng php ni suy trong ti liu hdtk NL) CHNG 5: TNH TON CHU TRNH LNH, TNH CHN MY NN5.1CHN CC THNG S CA CH LM VICCh lm vic ca mt h thng lnh c c trng bng 4 nhit sau.+ Nhit si ca mi cht lnh t0.+ Nhit ngng t ca mi cht lnh tk.+ Nhit qu lnh ca lng trc van tit lu tql.+ Nhit hi ht v my nn ( nhit qu nhit ) tqn.5.1.1 Nhit si ca mi cht lnhNhit si ca mi cht lnh ph thuc vo nhit ca kho lnh. C th ly nh sau: t0 = tb - t0, 0C [ 1, 204 ]Trong : tb - l nhit kho lnh. tb = 4 0C; t0 - l hiu nhit yu cu. Kho lnh la chn phng php lm lnh trc tip, m ca khng kh trong kho cao, hiu nhit yu cu l 8 130C nn chn t0 = 13 0C [ 1, 204 ] Vy t0 = 4 - 13 = -9 0C.5.1.2 Nhit ngng tNhit ngng t ca hi mi cht lnh ph thuc vo mi trng lm mt v nhit ca cht ti nhit chy qua thit b ngng t.Thit b ngng t ca h thng lnh c tc nhn lm mt l nc ly t ngun nc ngm qua h thng x l c tun hon khp kn qua thp gii nhit.Nhit ngng t c xc nh theo biu thc: tk = tw2 + tk, 0C [ 1, 205 ]Trong : tw2 - l nhit nc ra khi bnh ngng, 0C; tk - l hiu nhit ngng t yu cu, 0C. Chn nhit ngng t thc ra l mt bi ton ti u v kinh t v k thut, t gi thnh mt n v lnh l nh nht, nu hiu nhit ngng t nh, nhit ngng t thp, nng sut lnh tng nhng phi tng chi ph cho in nng chy bm nc gii nhit.... tk = ( 3 5 ) 0C c ngha l nhit ngng t cao hn nhit nc ra t 3 5 0C. [ 1, 205 ]Chn tk =5 0C.- Nhit nc u vo, u ra chnh lch nhau( 2 6) 0C ph thuc vo kiu thit b ngng t.tw2 = tw1 + (2 6) 0C.Vi tw1 l nhit nc vo bnh ngng.Thit b ngng t trong cm my l thit b ngng t ng chm v bc nm ngang nn chn tw = 5 0C. [ 1, 205 ]- Nhit nc vo bnh ngng ph thuc vo iu kin mi trng. tw1 = t +( 3 5) 0C.[ 1, 205 ] Vi t : l nhit bu t, vi t= 37,30C => t=330C Vy ta c tw1 = 37oC. tw2 =37+ 5 = 42oC. tk = 42 +5= 47 oC. 5.1.3 Nhit hi ht (th)- Nhit qu nhit l nhit ca hi mi cht trc khi vo my nn. Nhit hi ht bao gi cng ln hn nhit si ca mi cht.- Mc ch ca vic qu nhit hi ht l bo v my nn trnh khng ht phi lng. Tu tng loi mi cht v my nn m c nhit qu nhit khc nhau.- i vi my lnh fron, do nhit cui tm nn thp nn qu nhit hi ht c th chn cao. Trong my nn fron, qu nhit hi ht t c trong thit b hi nhit. Vi mi cht fron qu nhit khong (10 15) 0C. [ 1, 208] Chn th = 15 0C. =>Nn tqn = to + tqn = -9 + 15 = 6oC.5.1.4 Nhit qu lnh (tql)- L nhit ca mi cht lng trc khi vo van tit lu. Nhit qu lnh cng thp th nng sut lnh cng cao. tql= tw1+(3-5oC)= 37+(3-5oC)= 40-42oCChn tql=400C- Do s qu lnh lng c thc hin trong thit b hi nhit, nn nhit thi ra ca mi cht lng cng l nhit lng m hi mi cht sau khi bay hi nhn vo.Ta c phng trnh sau: h1 - h1 = h3 h3Trong h1, h1, h3, h3 l entalpi ti cc im nt trn th lgp I.Tra th lgp-i ca mi cht R22 ta c: to = -9 oC h1 = 401,57 kJ/kg tqn = 6 oC h1 = 406,454 kJ/kgVi nhit ngng t l 35oC , tra th lgp i ca mi cht R22 ta c : h3 = 258,15 kJ/kg.T phng trnh : h1 - h1 = h3 h3=> h3 = h3 h1 + h1 = 258,15 406,454 + 401,57 = 253,266 KJ/KgThng sim ntNhit oCp sutbarEntapikJ/kgTh tch ringm3/kg

11223346-990474740-96,0223,676744,37418,03418,03418,0346,022406,454401,57433,17415,93258,15253,266253,2660,42

5.2TNH TON CHU TRNH LNH5.2.1 Nng sut lnh ring khi lng L nng sut lnh ca 1 kg mi cht lnh lng p sut cao v nhit cao to ra, sau khi qua van tit lu v bay hi ht trong thit b bay hi, thnh hi bo ho kh nhit bay hi v p sut bay hi. Ta c: q0 = h'1 h4 kJ/kg.Trong : h'1- l Entapi ca hi (bo ho ) sau khi ra khi dn lnh. h4 - l Entapi ca mi cht sau khi qua van tit lu. Nn q0 = 401.57- 253.266 = 148.304 kJ/kg.5.2.2 Lu lng mi cht qua my nn

Ta c: kg/s. [ 1, 211 ]5.2.3 Nng sut th tch thc t ca my nn [ 1, 214 ] Ta c : Vtt = G v1 = 0.14 0.42 =0.0588 m3/s5.2.4 H s cp ca my nn Ch lm lnh ca h thng lnh: to = -9 0C po = 3.6767Pa. tk = 47 0C pk = 18.034Pa.

Ta c = => = 0.72

Xy dng chu trnh trn th Logp-h

Hnh 5.2: chu trnh 1 cp 1 tit lu lm mt trung gian mt phn c hi nhitNHA- My nn h p, MTG- Thit b lm mt trung gian, NCA- My nn cao pHN- Hi nhit, NT- Thit b ngng t, TL- Thit b tit lu, BH- Thit b bay hi

Cc qu trnh trn th:1-2 : Nn on nhit my nn h p s2=s1 2-3 : Lm mt ng p p=ptg=const thit b trung gian3-4 : Nn on nhit my nn cao p s4=s34-5 : Ngng t ng p p=pk=const trong thit b ngng t, mi cht nh nhit lng qk cho m trng gii nhit5-5: Qu trnh qu lnh ng p p=pk=const trong thit b hi nhit5-6: Tit lu t p sut pk ,h5=h66-1:Bay hi ng p, ng nhit trong thit b bay hi1-1: Qu trnh qu nhit ng p p=p0=const thit b hi nhit5.2.5 Th tch ht l thuyt

Ta c : m3/s. 5.2.6 Cng nn on nhit Ta c: Ns = G l = G (h2 h1) , kW. [ 1, 216 ] Vy Ns = 0.14 ( 433.17 406.454 ) = 3.740 ,kW5.2.7 Cng nn ch th L cng nn thc do qu trnh nn lch khi qu trnh nn on nhit l thuyt. Ta c: , kW [ 1, 217 ] i : L hiu sut ch th i = w + b t0. Trong : b - l h s thc nghim b = 0.001; w - l h s tn tht khng thy c w = .

Vy .

Suy ra: kW.5.2.8 Cng sut ma st Cng sut ma st sinh ra do s ma st trong cc chi tit chuyn ng ca my nn, cng sut ny ph thuc vo kch thc v ch hot ng ca my. Ta c: Nms =Vtt Pms , kW [ 1, 218 ] Pms vi my nn fren ngc dng th Pms = (0.019 0.034) Mpa Ta chn Pms = 0.025 Mpa [ 1, 218 ] Vy Nms = 0.0588 0.025 106 = 1470 W = 1.470 kW5.2.9 Cng sut hu ch L cng nn c tnh n tn tht ma st ca cc chi tit my nn nh pittng-xi lanh, tay bin-trc khuu-c pittng,y chnh l cng o c trn trc khuu ca my nn. Ta c: Ne = Ni + Nms, kW [ 1, 218 ] = 4.583 + 1.470 = 6.053 kW5.2.10 Cng sut inCng sut in Nel l cng sut o c trn bng u in c k n tn tht truyn ng, khp, ai ...v hiu sut chnh ca ng c in. Ta c: , kW [ 1, 218 ] Trong : td - l hiu sut truyn ng ai , y ta dng my nn bn kn nn td = 0.95 el - l hiu sut ng c el = 0.8 0.95. Chn el = 0.85.

Vy kW.5.2.11 Cng sut ng c lp t m bo an ton cho h thng lnh, ng c lp t phi c cng sut ln hn cng sut ng c in. Ta c: N/c = (1.1 2.1 ) Nel , kW; [ 1, 219 ] Chn h s an ton l 1.5 Nn N/c = 1.5 7.496 =11.244 kW.5.2.12 Ph ti nhit dn ngng

Ta c: KW.5.3TNH CHN MY NNMy nn l mt b phn rt quan trng ca h thng lnh, n quyt nh nng sut lnh ca h thng; phn quan trng ca my nn l nng sut lnh v cng sut ca ng c my nn i hi phi p ng c nng sut lnh ca kho bo qun. Nhim v ca my nn l lin tc ht hi mi cht lnh sinh ra thit b bay hi nn ln p sut cao y vo thit b ngng t.Qua vic tnh nhit ti kho lnh phn trc ta xc nh c nhit ti QoMN = 21.133 kW cho my nn, y chnh l nng sut lnh m my nn phi t c m bo duy tr c nhit lnh trong kho lnh v cng sut ng c lp t N/c = 11.244 kW. Chn my nn pittng ca Nga theo OCT 26.03-943-77K hiu: II20S xilanh: 4ng knh pittng: 6.25Vng quay: 24vg/sDi: 680 mmRng: 550 mmKhi lng: 223 kgVlt= 1.5410-2 Chn s my nn zmn=15.4TNH CHN THIT B NGNG TThit b ngng t trong h thng lnh l cc thit b trao i nhit b mt, trong hi mi cht lnh c p sut v nhit cao sau my nn c lm mt bng khng kh, nc hay cc cht lng nhit thp khc ngng t thnh th lng.Qu trnh ngng t lun km theo hin tng ta nhit, ni cch khc l nu khng c lm mt lin tc th qu trnh ngng t s dng li, mc ch l bin hi mi cht lnh thnh th lng cng khng thc hin c.Do tc nhn lnh l Freon nn ph hp vi tnh cht ca mi cht cc ng trao i nhit thng l ng ng c cnh nhm lng vo hoc cun trn b mt ngoi ca ng tng cng kh nng truyn nhit t pha freon. Theo cc d kin tnh ton c phn trn ta c:- Ph ti nhit thit b ngng t Qk =21.133 kW.- Nhit ngng t tk=470C. - Nhit nc vo lm mt tw1 = 37oC .- Nhit nc ra khi thit b ngng t tw2 = 42oC.

T cng thc Qk = k F ttb, W [ 1, 260]ttb - L hiu nhit trung bnh logaritVi t max = tk tw1 = 47 - 37 = 10oC; t min = tk - tw2 = 47 - 42 = 5 oC.

Nn Mt dng nhit (ph ti nhit): qf= k ttb = 700 7.21=5049.43 (W/m2) C th tnh c din tch trao i nhit cn thit. F=Qk/qf= 21.133 1000/ 5049.43=4.2 m2 Vi thit b ngng t ng chm v bc nm ngang ta c k - L h s truyn nhit, k = 700 W/m2k Chn bnh ngng t ng chm nm ngang (bng 5.2,I):Bnh ngng: KTP-12Din tch b mt ngoi: 12.8 m2ng knh ng v: 377 mmChiu di ng: 1.2 mS ng: 86Ti nhit: 43.3 kWS li: 4:2CU TO: Ta chn thit b ngng t kiu ng chm nm ngang v n c u im sau:+ Ph ti nhit ln nn t tiu hao kim loi, thit b trao i nhit gn nh, kt cu chc chn.+ Lm mt bng nc t ph thuc vo thi tit nn my hot ng n nh hn.+ D v sinh v pha nc lm mt.

7111098654321141381266

Hnh 5.4: Thit b ngng t ng chm nm ngangCh thchp k1. Van an ton (trc p k v van an ton phi c van chn tin khi sa cha, thay th hoc kha van khi van an ton nhy. ng xiphng dng cho kim rung hn)2. ng hi mi cht vo.3. ng cn bng vi bnh cha lng cao p lng t bnh ngng chy xung bnh cha d dng.4. ng d tr c khi lm ng x kh khng ngng.5. ng x kh v x bn v pha nc lm mt.6. Np phng v nc lm mt khng c p lc v trong np c cc tm phn chia to li i cho dng nc.7. ng x kh v x bn v pha nclm mt.8. ng x du.9. Rn du.10. ng x ca lng cao p.11. Cc ng trao i.13,14. ng vo v ra ca nc lm mt. Nc i t di ln trn c th ph y b mt trao i nhit.

5.5TNH CHN THIT B BAY HIThit b bay hi l ni trao i nhit gia mi cht lnh v i tng cn lm lnh, mi cht lnh nhn nhit ca i tng cn lm lnh ha hi thnh hi bo ha kh trc khi v my nn.Cng nh thit b ngng t, tnh ton thit b bay hi ch yu thit k v kim tra din tch trao i nhit cn thit theo cc thong s cho trc nh ti nhit Q0, nhit v lu lng cht ti lnh vo v ra nhit bay hi v n cu to nh hnh v:

Hnh 5.5 Thit b bay hi dng qutDin tch b mt trao i nhit:F= Q0/ k ttbVi: Q0: ti nhit lnh ca thit b bay hi, Q0=21.133 kWk: h s truyn nhit vi mi cht R22, chn k= 17.5ttb: hiu nhit trung bnh logarit gia mi cht v cht ti lnh.t max= tb1-t0 = 7-(-9) = 16t min = tb2-t0 = 1-(-9) = 10(V nhit bo qun sn phm l 40C nn chn tb1=70C, tb2=10C)

=>=>F= 21133/ 17.512.8=94.34 m2

Chn kho lnh c 2 dn lnh vy nng sut ca mi dn phi t t nht l 10.57 kW.

Chn dn lnh Friga-Bohn:Model: KB 2100Nng sut: 15,44kWBc cnh: 7mmChiu di: 1753mmChiu cao: 680mmChiu su: 720mmNng sut qut: 520 WKhi lng: 98 kg

CHNG 6: CC THIT B KHC CA H THNG6.1BNH CHA CAO P6.1.1 Cng dngBnh cha cao p c b tr ngay sau thit b 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 nm ngang mi cht NH3 l mt hnh tr nm ngang, c thit k m bo p sut lm vic l 1.8 MPa.6785123

54

Hnh 6.1: Bnh cha cao pCh thch1. p k.2. Van an ton.3. ng vo cu lng cao p t thit b ngng t.4. ng cn bng vi thit b ngng t.5. ng ra ca lng cao p pha trn hoc di bnh.6. ng thy sng ch mc lng trong bnh cha.7. ng x du.8. Rn du.

6.2THP GII NHIT6.2.1 Mc chGii nhit ton b loi nhit do mi cht lnh ngng t nh ra. Lng nhit ny thi ra mi trng nh cht ti nhit trung gian l nc.6.2.2 Cu to

Hnh 6.2: Thp gii nhitCh thch1- ng c qut gi.2- Chn bi nc.3- Dn phun nc.4- Khi m.5- Ca khng kh vo.6- B nc.7- ng nc lnh cp lm mt bnh ngng.8- Phin lc nc.9- Phu chy trn.10- Van x y.11- ng cp nc v van phao.12,13 ng nc nng t bnh ngng ra a vo dn phun lm mt xung nh khng kh i ngc t di ln.6.2.3 Nguyn lNc nng t bnh ngng v nc lm mt my nn theo ng (12) vo dn phun nc (3) gii nhit nh khng kh i t di ln (chuyn ng cng bc nh ng c qut gi) v ri xung b, theo ng 7 vo thit b ngng t v i lm mt my nn. Van phao c nhim v khi ng ng c bm nc cp nc cho thp khi mc nc thp hn gi tr cho php.6.2.4 Tnh tonDin tch tit din thp gii nhit:

Chn thp gii nhit c qut gi qF = 40 kW/m2

Ch thp gii nhit => Cc thng s:- Lu lng nc: 1.11 (l/s)- t ca nc: 5oC- Lu lng ca khng kh: 1.11 (m3)- Vng quay: 23.3 (vng/s)- Nhit ti: 23.2 (kW)- Din tch tit din thp: 0.44 (m2)- Kch thc(mm): + Mt bng: 848 x 848 + Thn thp: 660 x 736 + Chiu cao: 1600- Khi lng: 232 (kg)

6.3BNH TCH DUChn bnh tch du kiu nn chn6.3.1 Mc chHi mi cht sau khi c nn ra khi my nn thng b cun bn theo ht du bi trn ca my nn. Lng du ny nu n cc b mt trao i nhit ca cc thit b nh l thit b ngng t, bay hi s lm cn tr qu trnh trao i nhit v lm gim hiu qu ca thit b. Do cn phi tch du bi trn ra khi lung hi cao p v lung hi nn.V tr: sau my nn v trc thit b ngng t6.3.2 Cu toCh thch1- ng vo ca hi cao p.2- Van an ton.3- ng ra ca hi cao p.4- Cc tm chn, thc t thng dng tm chn c bc l 10mm bc l 20mm.5- Ming phun ngang.6- Tm ngn c nhng l 40mm.7312654

7- ng x du. Hnh 6.3: Bnh tch du6.3.3 Nguyn l lm vicDu c tch ra nh 3 nguyn nhn:+ Nh s gim vn tc t ngt khi i t ng nh ra bnh nn lc qun tnh gim t ngt.+ Nh lc ly tm khi ngoc dng nn ht du nng b vng ra v ri xung y nn.+ Nh cc tm chn (4): dng hi b va p vo cc tm chn s b mt vn tc t ngt v ht du c gi li v ri xung y bnh.6.4BNH CHA DU6.4.1 Nhim vDng gom du t cc thit b nh bnh tch du, bu du ca bnh ngng, bnh cha, bnh bay hi, bnh tch lng, gim tn tht v gim nguy him khi x du t p sut cao.6.4.2 Cu toBnh cha du l bnh hnh tr t ng hay nm ngang c ng ni vi ng ht my nn v ng ni vi p k, ni vi y x du v ng x du ra ngoi.

Ch thch:1- V thit b2- ng vo t bnh tch du3- Van x du4- Chn thit b

Hnh 6.4: Bnh cha du

6.4.3 Nguyn lKhi m van ni ng ht, p sut trong bnh gim xung, mi cht lnh c thu hi. Khi p sut d gim gn 0, c th m van x x du ra khi bnh. Hi du t cc bnh v bnh cha du nh chnh lch p sut.6.5BNH TRUNG GIAN6.5.1 Mc chDn lnh 1 cp c bnh trung gian lm mt hon ton c nhim v lm mt trung gian mt phn hay ton phn hi mi cht ra cp nn p thp v qu lnh lng trc khi vo van tit lu bng cch bay hi mt phn lng p sut v nhit trung gian.6.5.2 Cu to

Ch thch:1- V thit b2- Lp cch nhit3- Chn thit b4- Van x du5- ng ra ca cht lng 6- Hi vo t bnh cha cao p7- Hi ra t my nn8- Hi ra t my nn Hnh 6.5: Bnh trung gian

6.6BNH TCH LNG6.6.1 Mc ch 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.Cc bnh tch lng lm vic theo nguyn tc tng t nh bnh tch du, bao gm:1. Gim t ngt tc dng hi t tc cao xung tc thp. Khi gim tc t ngt cc git lng ng nng v ri xung y bnh.1. Thay i hng chuyn ng ca dng mi cht mt cch t ngt. Dng mi cht a vo bnh khng theo phng thng m thng a ngot theo gc nht nh.1. Dng cc tm chn ngn cc git lng. Khi dng mi cht chuyn ng va vo cc vch chn cc git lng b mt ng nng v ri xung.1. Kt hp tch lng hi nhit, hi mi cht khi trao i nhit s bc hi hon ton. 6.6.2 Cu toCh thch1- Lng vo t bnh trung gian2- p k3- Hi v my nn4- Tm chn5- ng ng6- Hi vo dn lnh7- Chn thit b8- V thit b9- Lp cch nhit

Hnh 6.6: Bnh tch lng

6.7PHIN SY LCPhin sy l mt thit b ph trong h thng lnh nhng n l mt thit b ph rt quan trng m bo cho h thng lnh hot ng bnh thng vi tin cy v tui th cao.Phin sy l mt ng hnh tr bn trong c cha cc ht cht rn c tnh cht hp th, hp ph v gi li m cng nh cc cht c hi cho h thng lnh nh mt s axit v kh l. Phin c hai u ni cho mi cht lnh i qua. Phin sy khi kt hp vi phin lc gi l phin sy lc, khi phin c b tr thm cc loi li thp, li ng, d, len, n gi li cc vt l nh cc bi, g st, vy hn trong vng tun hon mi cht lnh, trnh hng hc cho my nn v trnh tc cho ca thot ca van v ng ng.6.8MT GASL cc van chn, lp t cc van chn trn c ng nn ln ng ht ca h thng v tr gn my nn. Khi c cc van chn ny th cng vic bo tr, sa cha tr nn n gin v tit kim gas lnh rt nhiu.

Mt gas

6.9VAN Van mt chiu c b tr trn ng y ca my nn v thit b ngng t, khng cho dng mi cht t thit b ngng t chy tr li my nn khi dng my nn. Van an ton lp nhng thit b cao p v cha nhiu mi cht lng, dng phng trng hp p sut vt qu mc qui nh th x v thit b p sut thp hoc trc tip vo khng kh. Van tit lu nhit cn bng trong b tr trc dn bay hi iu chnh lng lng cung cp cho dn. Van kho c lp thit b (u vo v ra).

KT LUN

Trong sn xut v ch bin thc phm, bo qun lnh ng vai tr quan trng, n lm tng thi gian bo qun thc phm, phc v cho iu ha, d tr nguyn liu, ko di thi v sn xut cho x nghip. Do vy vn xy dng kho lnh l iu tt yu v cn thit. c hiu qu kinh t cao khi xy dng kho lnh, th trong qu trnh thit k kho lnh, vic xc nh nhit ti ca kho lnh cn phi chnh xc, cn thn v n l c s tnh chn cc thit b. Nu kt qu tnh ton nhit ti ca kho lnh nh hn kt qu thc t th dn n khng kinh t.V kin thc thc t cn nhiu hn ch nn khi tnh ton thit k khng trnh khi thiu st. Em mong c qu thy c ch bo thm, cho n ca em c hon thin hn.

TI LIU THAM KHO

[1]. Nguyn c Li, Mi cht lnh, Nh xut bn Gio dc, 1998.[2]. Nguyn c Li, Hng dn thit k h thng lnh, Nh xut bn Gio dc, 1999.[3]. Nguyn c Li - Phm Vn Ty, K thut lnh c s, Nh xut bn Gio dc,2003.[4]. Nguyn c Li - Phm Vn Ty, Bi tp k thut lnh, Nh xut bn Gio dc,1998.[5]. Nguyn c Li - Phm Vn Ty, My v thit b, Nh xut bn Gio dc, 2005.

GVHD: Th.s o Thanh KhTrang 8