LI M U
Thit k n kho lnh bo qun rau qu
LI M U
K thut lnh ra i hng trm nm nay v c s dng rt rng ri trong nhiu
ngnh k thut rt khc nhau: trong cng nghip ch bin v bo qun thc phm,
cng nghip ho cht, cng nghip ru, bia, sinh hc, o lng t ng, k thut sy
nhit thp, xy dng, cng nghip du m, ch to vt liu, dng c, thit k ch to
my, x l ht ging, y hc, th thao, trong i sng vv... Ngy nay ngnh k
thut lnh pht trin rt mnh m, c s dng vi nhiu mc ch khc nhau, phm vi
ngy cng m rng v tr thnh ngnh k thut v cng quan trng, khng th thiu c
trong i sng v k thut ca tt c cc nc.
Mt trong s l ng dng trong vic thit k cc loi kho lnh bo qun thc
phm. Trong n ny chng em tin hnh thit k kho lnh dng bo qun rau qu.Mc
lc
9Chng 1
9VAI TR CA K THUT LNH TRONG CNG NGH THC PHM
91.1. Tc dng ca nhit thp i vi thc phm
111.2. Cc ch x l lnh thc phm
14Chng 2
14TNH TON B TR MT BNG V DUNG TCH KHO LNH
142.1.Kho st s mt bng lp t kho lnh
142.1.1. Chn a im xy dng kho lnh.
142.1.2. Cc thng s kh hu
152.1.3.Cc iu kin bo qun trong kho.
172.2. Yu cu khi thit k mt bng kho lnh:
172.2.1. Yu cu chung i vi mt bng kho bo qun:
192.3. Yu cu chung i vi phng my:
192.4. Phn loi kho lnh:
192.4.1. Kho lnh ch bin (X nghip ch bin lnh)
192.4.2. Kho lnh phn phi
202.4.3. Kho lnh trung chuyn
202.4.4. Kho lnh thng nghip
202.4.5. Kho lnh vn ti
202.4.6. Kho lnh sinh hot
212.5. Phn b dung tch.
212.6. Xc nh s lng v kch tht cc bung lnh
232.6.1. Th tch kho lnh
242.6.3. Ti trng ca nn v ca trn
242.6.4.Xc nh din tch lnh cn xy dng:
242.6.5.S lng bung lnh phi xy dng:
252.6.6.Dung tch thc t ca kho lnh:
252.7.Quy hoch mt bng kho lnh
252.7.1. Yu cu chung i vi quy hoch mt bng kho lnh
262.7.2. Dung tch v chc nng ca kho lnh
272.7.3. Tnh ton kinh t
272.7.4. Chn mt bng xy dng
282.7.5. Ngun nc
282.7.6. Ngun in
282.7.7. Bc xp
30Chng 3
30TNH CCH NHIT CCH M
303.1. Cu trc xy dng v cch nhit kho lnh.
303.1.1. Mc ch ca vic cch nhit phng lnh:
313.1.2. Mc ch ca vic cch m :
323.2. Cu trc ca cch nhit cch m.
323.2.1.Cu trc cch nhit:
323.2.2.Cu trc cch m:
323.3. Phng php xy dng kho bo qun
333.3.1. Kt cu xy dng kho:
353.4. Vt liu cch nhit
373.5. Tnh ton cch nhit kho lnh:
373.5.1. Kt cu tng bao
313.5.2. Kim tra ng sng vch tng bao
323.5.3. Kim tra ng m trong c cu cch nhit
343.5.4. Xc nh chiu dy cch nhit nn
353.5.5. Xc nh kt cu trn kho lnh
383.5.6. Xc nh chiu dy cch nhit tng ngn:
38Chng 4
38TNH NHIT TI V CHN H THNG
384.1. Tnh nhit ti
394.1.1. Mc ch.
394.1.2.Tnh nhit ti
444.1.3.Xc nh ti nhit v nng sut lnh cho my nn.
444.2. Chn cc ch lm vic v tnh chn thit b
444.2.1. Chn cc thng s lm vic.
464.2.2.Tnh chu trnh my lnh.
494.2.3. Tnh chn thit b
57Chng5:
THI CNG LP T
575.1. Gia c v xy dng nn mng
585.1.1. c khung kho bng b tng ct thp.
585..1.2. Dng khung mi v lp mi.
585.2. Lp t kho lnh
585.2.1. Cng tc chun b.
585..2.2. Thi cng lp t.
635.3. Lp t h thng lnh.
635.3.1. Lp t cm dn ngng, my nn.
645.3.2. Lp t cm dn lnh.
655.3.3. Lp t ng ng ht ca my nn, v ng ng t bnh cha cao p n dn
lnh, bnh tch lng v van tit lu.
685.4. ui bi v th x, ht chn khng v np gas h thng
685.4.1. Quy trnh ui bi h thng.
685.4.2. Th x h thng.
695.4.3. Ht chn khng h thng.
705.4.4. Np gas cho h thng.
715.5. Vn hnh h thng lnh
715.5.1.Cng tc chun b.
715.5.2.Vn hnh h thng.
725.5.3.Dng my.
725.6. Bo dng h thng.
735.6.1.Bo dng my nn.
735.6.2.Bo dng thit b ngng t.
735.6.3.Bo dng thit b bay hi.
DANH SCH CC BNG TRONG BI9Bng 1.1: Kh nng phn gii ph thuc
nhit
10Bng 1.2: nh hng ca nhit n vi sinh vt
14Bng 2-1. Thng s kh hu TPHCM.
15Bng 2-2: Ch v thi gian bo qun rau qu ti
21Bng 2-3. Tiu chun cht ti v th tch ca mt s sn phm bo qun
lnh
37Bng 3-1: Chn kt cu vch tng bao
33Bng3-2: p sut bo ha theo nhit
34Bng 3-3: Kt cu cch nhit ca nn
35Bng 3-4:
37Bng3-5: Tnh cht vt l ca khng kh m 2
43Bng 4-1: Bng tng kt nhit ti
47Bng 4-2: Cc tng hp cc thng s trn cc im nt ca chu trnh.
50Bng 4-3: Thng s dn lnh
52Bng 4-4: Thng s thit b ngng t
56Bng 4-5: Kt qu tnh ton ng ng chn.
Chng 1
VAI TR CA K THUT LNH TRONG CNG NGH THC PHM
1.1. Tc dng ca nhit thp i vi thc phm
Nm 1745 nh bc hc Nga Lmnxp trong mt lun n ni ting Bn v nguyn nhn
ca nng v lnh cho rng: Nhng qu trnh sng v thi ra din ra nhanh hn do
nhit cao v km hm chm li do nhit thp.
Tht vy, bin i ca thc phm tng nhanh nhit 50oC v nhit ny rt thch
hp cho hot ho ca men phn gii( 40 (enzim) ca bn thn thc phm v vi
sinh vt.
nhit thp cc phn ng ho sinh trong thc phm b c ch. Trong phm vi
nhit bnh thng c gim 10oC th tc phn ng gim xung 1/2 n 1/3 ln.
Nhit thp tc dng n hot ng ca cc men phn gii nhng khng tiu dit c
chng. Nhit xung di 0oC, phn ln hot ng ca enzim b nh ch. Tuy nhin mt
s men nh lipaza, trypsin, catalaza nhit -191oC cng khng b ph hu.
Nhit cng thp kh nng phn gii gim, v d men lipaza phn gii m.
Khi nhit gim th hot ng sng ca t bo gim l do:
- Cu trc t bo b co rt
- nht dch t bo tng
- S khuych tn nc v cc cht tan ca t bo gim.
- Hot tnh ca enzim c trong t bo gim.
Bng 1.1: Kh nng phn gii ph thuc nhit
Nhit (0C)40100-10
Kh nng phn gii (%)11,93,892,260,70
Cc t bo thc vt c cu trc n gin, hot ng sng c th c lp vi c th sng.
V vy kh nng chu lnh cao, a s t bo thc vt khng b cht khi nc trong n
cha ng bng.
T bo ng vt c cu trc v hot ng sng phc tp, gn lin vi c th sng. V
vy kh nng chu lnh km hn. a s t bo ng vt cht khi nhit gim xung di
4oC so vi thn nhit bnh thng ca n. T bo ng vt cht l do ch yu nht tng
v s phn lp ca cc cht tan trong c th.
Mt s loi ng vt c kh nng t iu chnh hot ng sng khi nhit gim, c th
gim cc hot ng sng n mc nhu cu bnh thng ca iu kin mi trng trong mt
khong thi gian nht nh. Khi tng nhit , hot ng sng ca chng phc hi, iu
ny c ng dng trong vn chuyn ng vt c bit l thu sn dng ti sng, m bo
cht lng tt v gim chi ph vn chuyn.
nh hng ca lnh i vi vi sinh vt.
- Kh nng chu lnh ca mi loi vi sinh vt c 00C. Tuy nhin mt s khc
chu lnh nhit khc nhau. Mt s loi cht nhit 20C hay nhit thp hn.
- Khi nhit h xung thp nc trong t bo vi sinh vt ng c lm v mng t
bo sinh vt. Mt khc nhit thp, nc ng bng lm mt mi trng khuych tn cht
tan, gy bin tnh ca nc lm cho vi sinh vt cht.
- Trong t nhin c 3 loi vi sinh vt thng pht trin theo ch nhit
ring
Bng 1.2: nh hng ca nhit n vi sinh vt
Vi khunNhit thp nhtNhit thch hp nhtNhit cao nht
Vi khun a lnh (Psychrophiles)- Vi khun a m(Mesophiles)- Vi khun
a nng(Thermopphiles)90oC( 20oC40 (0oC1055oC( 40oC50 ( 20oC20
(1570oC(30oC45oC50
Nm mc chu ng lnh tt hn, nhng nhit -100C hu ht ngng hot ng ngoi
tr cc loi Mucor, Rhizopus, Penicellium. ngn nga mc phi duy tr nhit
di -150C. Cc loi nm c th sng ni khan nc nhng ti thiu phi t 15%.
nhit -180C, 86% lng nc ng bng, cn li 14% khng cho vi sinh vt pht
trin.
V vy bo qun thc phm lu di cn duy tr nhit kho lnh t nht
-180C.
bo qu thc phm ngi ta c th thc hin nhiu cch nh: Phi, sy kh, ng hp
v bo qun lnh. Tuy nhin phng php bo qu lnh t ra c u im ni bt v:
- Hu ht thc phm, nng sn u thch hp i vi phng php ny.
- Vic thc hin bo qun nhanh chng v rt hu hiu ph hp vi tnh cht ma
v ca nhiu loi thc phm nng sn.
- Bo tn ti a cc thuc tnh t nhin ca thc phm, gi gn c hng v, mu
sc, cc vi lng v dinh dng trong thc phm.
1.2. Cc ch x l lnh thc phm
Thc phm trc khi c a vo cc kho lnh bo qun, cn c tin hnh x l lnh h
nhit thc phm t nhit ban u sau khi nh bt, git m xung nhit bo
qun.
C hai ch x l lnh sn phm l x l lnh v x l lnh ng
a) X l lnh l lm lnh cc sn phm xung n nhit bo qun lnh yu cu. Nhit
bo qun ny phi nm trn im ng bng ca sn phm. c im l sau khi x l lnh,
sn phm cn mm, cha b ha cng do ng bng.
b) X l lnh ng l kt ng (lm lnh ng) cc sn phm. Sn phm hon ton ha
cng do hu ht nc v dch trong sn phm ng thnh bng. Nhit tm sn phm t
-80C, nhit b mt t t -180C n -120C.
X l lnh ng c hai phng php:
a) Kt ng hai pha
Thc phm nng u tin c lm lnh t 370C xung khong 40C sau a vo thit b
kt ng nhit tm khi thc phm t -80C.
b) Kt ng mt pha
Thc phm cn nng c a ngay vo thit b kt ng h nhit tm khi thc phm
xung t di -80C.
Kt ng mt pha c nhiu u im hn so vi kt ng hai pha v tng thi gian
ca qu trnh gim, tn hao khi lng do kh ngt gim nhiu, chi ph lnh v din
tch bung lnh cng gim.
i vi ch bin tht thng s dng phng php mt pha. i vi hng thu sn do
phi qua khu ch bin v tch tr trong kho ch ng nn thc t din ra hai
pha.
Cc loi thc phm khc nhau s c ch bo qun v ng lnh thch hp khc nhau.
ch bo qun lnh v trong giai on u ca qu trnh kt ng hai pha, ngi ta
phi gia lnh sn phm. Thng thng thc phm c gia lnh trong mi trng khng
kh vi cc thng s sau:
- m khng kh trong bung: 85 ( 90%
- Tc khng kh i lu t nhin: 0,1 - 0,2 m/s; i lu cng bc cho php 0,5
m/s (k c rau qu, tht, c, trng...).
- Giai on u, khi nhit sn phm cn cao, ngi ta gi nhit khng kh gia
lnh thp hn nhit ng bng ca sn phm chng 1 - 20C. Nhit ng bng ca mt s
sn phm nh sau:
Tht 1,2 - 4,20C. Nhit khng kh gia tng 20C - (0C
C t 0,6 - 20C.
Rau qu 0,8 - 4,20C thi gian gia nhit ko di thm 5h.
Sau khi tng nhit sn phm t 3 - 80C, nhit khng kh tng ln 10C. Tm
li, cn tng tc gia lnh nhng phi trnh ng bng trong sn phm.
Trong mt kho lnh c th c bung gia lnh ring bit. Song cng c th s
dng bung bo qun lnh gia lnh. Khi , s lng sn phm a vo phi ph hp vi
nng sut lnh ca bung. Cc sn phm nng phi b tr u cnh cc dn lnh rt ngn
thi gian gia lnh. Sn phm khi gia lnh xong phi thu dn v sp xp vo v
tr hp l trong bung tip tc gia lnh t tip theo.
Chng 2
TNH TON B TR MT BNG V DUNG TCH KHO LNH TC "Chng 2" \f C \l
"1"
TC "Chng 2" \f C \l "1" 2.1.Kho st s mt bng lp t kho lnh
2.1.1. Chn a im xy dng kho lnh.
Chn a im kho lnh l cng tc khng th thiu v ng vai tr quan trng
trong qu trnh thit k v xy dng kho. Khi chn a im th ta phi bit c cc
thng s v kh tng thu vn, a l T ra cc phng n thit k v xy dng kho cho
thch hp lm cho cng trnh c gi thnh thp nht v cht lng cng trnh l tt
nht, cng trnh c cc ri ro do thin tai gy ra nh thin tai, l lt ti a
phng xy dng kho.
Kho lnh bo qun c t gn ch u mi qun Th c Thnh Ph H Ch Minh..
2.1.2. Cc thng s kh hu
Cc thng s kh hu ny c thng k, khi tnh ton m bo an ton th ta phi
ly gi tr cao nht, tc l gi tr khc nghit nht m bo an ton cho my lnh v
trnh cc s c ng tic xy ra. Tra bng 1-1 sch HDTKHTL ta c.
Bng 2-1. Thng s kh hu TPHCM.
Nhit , 0C m tng i, %
TB c nmMa hMa ngMa hMa ng
26,737,317,47882
2.1.3. Cc iu kin bo qun trong kho.
Ch bo qun sn phm trong kho cng chnh l iu kin mi trng trong kho m
ta phi to ra duy tr sn phm t tiu chun cht lng cao.
a) Chn nhit bo qun.
Nhit bo qun thc phm ph thuc vo tng loi sn phm v thi gian bo qun
ca chng. Thi gian bo qun cng lu i hi nhit bo qun cng thp.
Kho lnh bo qun rau qu ch yu l sup l, carot, khoai ty nn thi gian
bo qun khong 2 n 3 tun chn nhit bo qun l 20C.
b) m ca khng kh trong kho lnh.
m ca khng kh trong kho nh hng rt ln n cht lng sn phm khi s dng.
Bi v m ca khng kh trong kho lin quan n hin tng thng hoa ca nc trong
sn phm. V vy tu tng loi sn phm m ta chn m ca khng kh cho thch
hp.
c) Tc khng kh trong kho lnh.
Khng kh chuyn ng trong kho c tc dng ly i nhit lng ca sn phm bo
qun, nhit do m ca, do cu nhit, do ngi lao ng trong kho. Ngoi ra cn
phi m bo s ng u nhit , m v hn ch nm mc hot ng.
nh my Thin m sn phm c bao gi cch m nn ta thit k khng kh i lu cng
bc bng qut gi vi vn tc v = 3m/s.
Bng 2-2: Ch v thi gian bo qun rau qu ti Sn phmNhit bo qun, (oC)
m, (%)Thng giThi gian bo qun,
Bi0 585M12 thng
Cam0,5 285M- nt -
Chanh1 285- nt -- nt -
Chui chn14 1685- nt -510 ngy
Chui xanh11,5 13,585- nt -310 tun
Da chn4 785- nt -34 tun
Da xanh1085- nt -46 thng
o0 185 90- nt -46 thng
To0 390 95- nt -310 thng
C chua chn2 2,575 80- nt -1 thng
C rt0 190 95- nt -vi thng
C chua xanh680 90- nt -1014 ngy
Da chut0 485- nt -vi thng
u kh5 770 75ng912 thng
u ti290M34 tun
Hnh0 175- nt -12 nm
Khoai ty3 685 90- nt -56 thng
Nm ti0 190- nt -12 tun
Rau mung5 1080 90- nt -35 tun
Ci x lch390- nt -3 thng
Xu ho0 0,590- nt -26 thng
Ci bp, xp l0 190- nt -4 tun
Su su090- nt -4 tun
u 8 1080 85- nt -2 tun
Qu b4 1185- nt -10 ngy
Khoai lang12 1585- nt -56 tun
Bng actis1085- nt -2 tun
Mt chn (mi)890- nt -1 tun
Thanh long1290- nt -4 tun
Mng ct1285- nt -34 tun
2.2. Yu cu khi thit k mt bng kho lnh:
2.2.1. Yu cu chung i vi mt bng kho bo qun:
Quy hoch mt bng l b tr cc ni sn xut cho ph hp vi dy chuyn cng
ngh, t c mc tiu th cn phi ph cc yu cu sau:
- Phi b tr mt bng kho bo qun ph hp vi dy chuyn cng ngh, sn phm i
theo dy chuyn khng gp nhau, khng chng cho ln nhau, an xen ln
nhau.
- m bo s vn hnh tin li, r tin, chi ph u t thp
- Phi m bo k thut an ton, chng chy n.
- Mt bng khi quy hoch phi tnh n kh nng m rng phn xng hoc x
nghip.
Quy hoch mt bng kho bo qun cn phi m bo vic vn hnh x nghip d tin
v thun li. C s chnh gim chi ph vn hnh l gim dng nhit xm nhp kho bo
qun, gim th tch v gim nh cc cng vic chng cho nhau, gim dng nhit qua
vch th cn gim din tch xung quanh. V trong cc dng hnh hc thy hnh khi
ch nht c din tch ln nht. gim cn lm dng hnh lp phng khi ng v mt sp
xp hng ho th khng c li , do chng ta phi t b kin thc 1 x 1 cho nn
tng kh nng xp hng ho chng ta s dng t l 2 x 1 n 5 x 1 hoc gim dng
nhit qua vch cn hp nht cc phng lnh thnh mt khi gi l block lnh bi v
vic ny xy lp phn tn cc kho lnh ra khng nhng ln tng tn tht nhit qua
vch , cn lm tng phn tn cc kho lnh ra. Khng nhng lm tng tn tht nhit
qua vch, cn lm tng cc chi ph v nguyn vt liu khc.
- Bin php gim dng nhit xm nhp vo kho bo qun chng ta tm cch ngn
chn, khi chng ta m ca kho bo qun i vi nhng kho tip xc bn ngoi.
Pkkk < Pfkk
- Gim dng nhit xm nhp khi m ca kho bo qun thc hin nhng cch
sau:
Dng mng che chn vic i li kh khn trong khi lm vic .
Xy dng hnh lang m, nht i vi h thng kho bo qun ln.
Lm mng gi chn (t qut ca) cng tc in iu khin qut gn lin vi cnh ca,
khi ca m th qut chy, ngc li khi ng ca th qut dng.
Quy hoch phi tnh n c im ca h thng lnh. H thng lnh kho bo qun rau
qu nhit khng kh kho rt thp nhit 20C. Nn kho phi tip xc vi mt t sau
mt thi gian di lm cho nhit ca nn kho h thp dn xung khi nhit ca nn t
gim th xy ra hin tng nc trong t ng bng.
Nn kho v mt l thuyt khi t 00C nc trong nn t ng bng chuyn pha t
lng sang rn. Do kho s li ln d ph v cu trc xy dng ca kho. V vy trnh
hin tng ny ta lm nh sau :
Khng nn b tr nhng kho bo qun c nhit thp st mt t c iu kin nn b tr
trn cao .
Nn kho xy cc ng thng gi ng knh 200 ( 300 mm, c xy dng cch nhau 1
( 1,5 m to iu kin cho khng kh tun hon qua h thng ng ny lm cho nn t
nhit khng thay i
nc ta thng xy ra l lt cho nn cc kho bo qun thng c xy lp cao hn
mt t, khi khong trng di nn kho chnh l khong thng gi.
Si m sn kho, nn kho bng cch lp t cc dy in tr, ng knh dy in tr l
8 ( 12 mm t vo y in tr mt in p U nm trong 24 ( 26 V, nhit iu khin t
ng khng nh hn 1 ( 20C( lp rle nhit ) lm vic theo nguyn tc s thay i
nhit , s thay i v s gim n hoc thay i nhit , s thay i dch chuyn cc n
by.
2.3. Yu cu chung i vi phng my:
Phng my l khu vc ht sc quan trng ca xi nghip. Do n cn t cc yu cu
sau:
- Phong my nn b tr tng trt.
- B my v t hp my khng c lm lin vi cc mng tng v cc kt cu xy dng
khc ca nh xng kho bo qun.
- Khong cch gia cc t hp my phi m bo ln hn 1 m v gia t hp my vi
tng khng nh hn 0,8 m.
- Phng my phi c 2 ca ring bit cch xa nhau trong t nht phi c mt
ca thng trc tip vi bn ngoi.
- Cc ca phng my phi m v pha bn ngoi.
- Phng my v cc thit b phi c h thng thng gi, phi m bo thay i khng
kh 3 ln /ngy. H thng gi phi m bo lu lng khng kh thay i 7ln/ngy.
- Phng my v thit b phi c trang b nhng phng tin phng chng chy n v
an ton in.
2.4. Phn loi kho lnh:
2.4.1. Kho lnh ch bin (X nghip ch bin lnh) L mt b phn ca cc c s
ch bin thc phm nh tht, c, sa, rau, qu Cc sn phm l thc phm lnh, lnh
ng, hp chuyn n cc kho lnh phn phi, kho lnh trung chuyn hoc kho lnh
thng nghip. c im l nng sut lnh ca cc thit b ln. Chng l mt xch u tin
ca dy chuyn lnh.
2.4.2. Kho lnh phn phi Thng dng cho cc thnh ph v cc trung tm cng
nghip bo qun cc sn phm thc phm trong mt ma thu hoch, phn phi iu ha
cho c nm.Phn ln cc sn phm c gia lnh hoc kt ng x nghip ch bin ni khc
a n y bo qun. Mt phn nh c th c gia lnh v kt ng ti kho lnh t 3 6
thng. Dung tch kho rt ln, ti 10 15 ngn tn, c bit 30 35000 tn.Kho
lnh chuyn dng bo qun mt loi mt hang v vn nng bo qun nhiu loi mt
hang: tht, sa, c, rau quNu kho lnh c cc phn xng kem, nc , phn xng
ch bin ng gi, gia lnh v kt ng th gi l x nghip lin hip lnh.
2.4.3. Kho lnh trung chuyn
Thng t cc hi cng, nhng im nt ng st, b,dng bo qun ngn hn nhng sn
phm ti nhng ni trung chuyn. Kho lnh trung chuyn c th kt hp lm mt vi
kho lnh phn phi v kho lnh thng nghip.
2.4.4. Kho lnh thng nghip
Dng bo qun ngn hn thc phm sp a ra th trng tiu th. Ngun hng ch yu
ca kho lnh ny l t kho lnh phn phi. Kho lnh thng nghip c chia lm hai
loi theo dung tch: kho lnh thng nghip ln c dung tch t 10 n 150 tn
dng cho cc trung tm cng nghip, th x Kho lnh nh c dung tch n 10 tn
dng cho cc ca hang, quy hng thng nghip, khch snthi hn bo quntrong
vng 20 ngy. Kiu ny bao gm c cc loi t lnh, t knh lnh thng nghip.
2.4.5. Kho lnh vn ti
Thc t l cc t lnh, tu ha, tu thy hoc my bay lnh dng vn ti cc sn
phm bo qun lnh. Cc khoang lnh c th chim ton b hoc mt phn khoang hng
ca phng tin vn ti.
2.4.6. Kho lnh sinh hot
Thc cht l cc loi t lnh, t ng cc c khc nhau s dng trong gia nh.
Chng c coi l mt xch cui cng ca dy chuyn lnh, dng bo qun cc thc phm
tiu dng trong gia nh hoc tp th, lm lp phng, thi thc phm. Dung tch t
50 tn n mt vi mt khi.2.5. Phn b dung tch. Cc kho lnh bo qun rau qu
thng c cc bung sau: - Bung bo qun rau qu - Bung ch bin (la chn, phn
loi, ng gi, ng hp); - Bung tip nhn v phn phi sn phm. i vi cc kho
lnh nh di 1000 tn c th s dng mt bung vi nhiu chc nng th d: bung x
l, phn phi v tip nhn ca kho lnh ch bin rau qu c th l mt bung duy
nht. Kho lnh phn phi rau qu th khng cn bung ny. Cc bung gia lnh,
thu gom ca cc kho lnh thu mua, sau ma v c th dng lm ni bo qun, phn
loi trc khi bn.
2.6. Xc nh s lng v kch tht cc bung lnh
Dung tch kho lnh l i lng c bn cn thit xc nh s lng v kch thc cc
bung lnh. Dung tch kho lnh l lng hng c bo qun ng thi ln nht trong
kho, n v l tn hng. Ngoi ra, s lng v kch thc cc bung lnh ph thuc vo
loi hng c bo qun trong kho, c im kho lnh (kho lnh phn phi, trung
chuyn, ch bin hoc thng nghip).Bng 2-3. Tiu chun cht ti v th tch ca
mt s sn phm bo qun lnh
Sn phm bo qunTiu chun cht ti, gv tn/m3H s tnh th tch
Tht b ng lnh con con v con
Tht cu ng lnh
Tht ln ng lnh
Gia cm ng lnh trong hm g
C ng lnh trong hm g hay cactong
Tht thn, c ng trong hm, cactong
M trong hp cactong
Trng trong hp cactong
hp trong cc hm g hoc cactong
Cam, qut trong cc ngn g mng
KHI SP XP TRN GI
M trong cc hp cactong
Trng trong cc ngn cactong
Tht hp trong cc ngn g
Gi trong cc ngn g
Tht gia cm ng lnh trong cc ngn g
trong cc ngn cactong
Nho v c chua khay
To v l trong ngn g
Cam, qut trong hp mng,
trong ngn g, cactong
Hnh ty kh
C rt
Da hu, da b
Bp ci
Tht gia lnh v kt ng bng gi treo trong container0.40
0.30
0.35
0.28
0.45
0.38
0.45
0.70
0.80
0.27
0.60 0.65
0.45
0.70
0.26
0.38
0.30
0.44
0.38
0.30
0.31
0.32
0.30
0.30
0.32
0.40
0.300.88
1.17
1
1.25
0.78
0.92
0.78
0.50
0.44
1.30
0.58 0.54
0.78
0.50
1.35
0.92
1.17
0.79
0.92
1.17
1.03
1.09
1.17
1.03
1.09
1.87
1.17
5.5
2
2.6.1. Th tch kho lnh c xc nh theo biu thc:
(2.1) E dung tch kho lnh, tn;V th tch kho lnh, m3;gv nh mc cht
ti th tch, tn/m3.
T dung tch kho lnh cho cng c th tnh th tch kho lnh mt cch d dng
t biu thc 2-1.
nh mc cht ti gv tra theo bng 2-3.
Chn gv= 0,35 tn/m3;
E = 300 tn;
V = 300/0,35 = 857,14(m3).2.6.2. Din tch cht ti Ca bung lnh F,
m2, c xc nh qua th tch bung lnh v chiu cao cht ti:
F din tch cht ti hoc din tch hng chim trc tip, m2; h chiu cao
cht ti, m;
V th tch.
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 xp. 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. Kho lnh mt tng c chiu cao 6 m th chiu cao cht
ti ln ti 5 m.
= 857,14/5 = 171,42 m2.
2.6.3. Ti trng ca nn v ca trn c tnh ton theo nh mc cht ti v chiu
cao cht ti ca nn v gi treo hoc mc treo vo trn:
gF gv x h
gF nh mc cht ti theo din tch, tn/m2.
gF 0,35 x 5 1,75 tn/m2.
2.6.4. Xc nh din tch lnh cn xy dng:
F1 din tch lnh cn xy dng, m2; F h s s dng din tch cc bung cha,
tnh c ng i v cc din tch gia cc l hng, gia l hng v ct, tng v cc din
tch lp t thit b nh dn bay hi, qut. F ph thuc din tch bung v ly theo
bng 2-4.Bng 2-4. H s s dng din tch theo bung
Din tch bung lnh, m2F
n 20
T 20 n 100
T 100 n 400
Hn 4000.50 0.60
0.70 0.75
0.75 0.80
0.80 0.85
Qua bng 2-4 ta c th thy bung cng rng, h s s dng din tch s dng
cng ln v c th b tr hp l hn cc li i, cc l hng v cc thit b.
Tra bng chn F = 0,75
=> F1= 171,42/0,75 = 228,56 m2.
2.6.5. S lng bung lnh phi xy dng:
f din tch bung lnh quy chun chn xc nh qua cc hng ct kho, m2. Din
tch bung lnh quy chun c chn l f = 60 m2.
Vy:
Chn Z = 4, kch c mi bung s l 6 x 10 m. Thm mt bung ph tr, mt
gian my, mt hnh lang t.
Lu : Khi thit k mt bng kho lnh Cn phi tnh ton thm cc din tch lnh
ph tr cha nm trong cc tnh ton trn. Th d hnh lang, bung tho v cht
ti, kim nghim sn phm, bung cha ph phm v k c bung kt ng ca kho lnh
phn phi.
Din tch kho lnh quy chun c tnh theo hng ct quy chun cch nhau 6 m
nn f c s l 36 m 2. Cc din tch quy chun khc l bi s ca 36 m2. Trong
khi tnh ton, din tch lnh c th ln hn din tch ban u 10 15%, khi chn Z
l s nguyn.
2.6.6. Dung tch thc t ca kho lnh:
Z1 s lng bung lnh thc t xy dng; Z = 4.
(tn)
2.7. Quy hoch mt bng kho lnh
2.7.1. Yu cu chung i vi quy hoch mt bng kho lnh
Quy hoch mt bng kho lnh l b tr nhng ni sn xut, x l lnh, bo qun v
nhng ni ph tr ph hp vi dy chuyn cng ngh. t c mc ch cn tun th cc yu
cu sau:
Phi b tr cc bung lnh ph hp dy chuyn cng ngh. Sn phm i theo dy
chuyn khng gp nhau, khng an cho nhau. Cc ca ra vo ca bung cha phi
quay ra hnh lang. Cng c th khng cn hnh lang nhng sn phm theo dy
chuyn khng i ngc.
Quy hoch cn phi t chi ph u t l b nht. Cn s dng rng ri cc cu kin
tiu chun, gim n mc thp nht cc din tch ph tr nhng phi m bo tin nghi.
Gim cng sut thit b n mc thp nht.
Quy hoch mt bng cn phi m bo s vn hnh thun li v r tin.
Quy hoch phi m bo li i v ng vn chuyn thun li cho vic bc xp th
cng hoc c gii thit k.
Chiu rng kho lnh nhiu tng khng qu 40 m.
Chiu rng kho lnh mt tng phi ph hp vi khong vt ln nht 12 m, thng
ly 12, 24, 36, 48, 60, 72 m.
Chiu di kho lnh c ng st nn chn cha c 5 toa tu lnh bc xp cng
lc.
Chiu rng sn bc d ng st 6 7,5 m; sn bc d t cng vy.
Trong mt vi trng hp, kho lnh c sn bc d ni lin rng 3,5 m, nhng
thng thng cc kho lnh c hnh lang ni ra c hai pha, chiu rng 6 m.
Kho lnh th tch < 600 tn khng c ng st, ch c mt sn bc d t dc
theo chiu di kho m bo mi phng thc bc d.
gim tn tht nhit qua kt cu bao che, cc bung lnh c nhm li tng khi
vi mt ch nhit .
Mt bng kho lnh phi ph hp vi h thng lnh chn. iu ny c bit quan
trng vi kho lnh mt tng v khng phi lun lun m bo a c mi cht lnh t cc
thit b lnh v, do phi chuyn sang s ln hn vi vic cp lng t di ln.
Mt bng kho lnh phi m bo k thut, an ton phng chy cha chy.
Khi huy hoch cng cn phi tnh ton n kh nng m rng kho lnh. Phi li
mt mt mt tng c th m rng kho lnh.
2.7.2. Dung tch v chc nng ca kho lnh
Ni chung cc kho lnh c dung tch v cng dng ht sc khc nhau, nn mt
bng cng c b tr khc nhau. Kho lnh a nng phn ln l cc kho lnh cho thu.
Ngi ta cho thng nhn v cc doanh nghip thu nn hng ho ht sc a dng v ch
bo qun cng khc nhau, nn kho lnh cng cn a dng p ng nhu cu . Tuy nhin
xu hng pht trin li l cc kho lnh chuyn dng s dng cho mt mt hng n nh
no , v d cc kho lnh bo qun tht cho l m, kho bo qun c bn cng. Cc kho
lnh c bn cng tip nhn c c ch bin v kt ng trn cc tu c a v Cc kho lnh
tm xut khu, cc kho lnh rau qu trc khi vn chuyn i xa hoc cc kho lnh
bo qun khi i thu hi trong thi v v ng thi l cc trung tm thu mua.
t c hiu qu kinh t, din tch kho lnh ti thiu cho thu phi t c 2000
m2, gii hn ln nht l khng hn ch. Trung bnh cc kho lnh cho thu c din
tch t 5000 n 10000 m2. Cc kho lnh chuyn dng c nhng quan im ring v
hiu qu kinh t nn cng khng c gii hn v din tch.
2.7.3. Tnh ton kinh t
Cn c s tnh ton k lng v kinh t khi tin hnh xy dng kho lnh. i vi
kho lnh cho thu cn phi c vn u t xy dng (gi thit b, vn xy dng c bn)
vi gi vn hnh ( nguyn liu tiu hao khi vn hnh, gi sa cha, gi in, nc,
thu, lng, phc li, bo him x hi, cc chi ph khc) vi kh nng cht ti, kh
nng quay vng hng, kh nng cho thu, din tch cc loi phng c th cho
thu.
2.7.4. Chn mt bng xy dng
Khi chn mt bng xy dng, ngoi cc yu cu chung nh nu trn cn phi ch n
mng ca kho lnh phi vng chc bi vy cn phi tin hnh kho st nn mng v mc
ncVic gia c nn mng nhiu khi dn n vic tng ng k vn u t xy dng. c bit
cc kho lnh bn cng cn ng cc v x l nn mng. cc vng khai thc m, vic
khai thc c th dn ti cc h hng v nn mng, st l t ai. Cc x l n nh nn
mng i khi rt tn km. Nu mc nc qu ln cn c bin php chng thm m.
2.7.5. Ngun nc
Do nhit thi thit b ngng t l rt ln nn ngay t khi thit k cn phi
tnh ton n ngun nc. C th x dng nc thnh ph, tuy nhin nu c kh nng t
khai thc l tt nht, nh vy s ch ng hn rt nhiu. Cn phi khoan v bm t cc
ging khoan, xc nh cht lng v tr lng nc v kh nng khai thc ti ch. min
Bc Vit Nam, nc khai thc cc ging khoan c nhit n nh 24oC trong c ma
ng ma h nn rt thun li cho cho gii nhit bnh ngng so vi nc tun hon ti
32oC, nng sut lnh khi dng nc ging khoan c th tng ti 20% v in nng
tiu th c th gim ti 15%. Ngoi vic cp nc, vic thot nc cng cn c d tnh.
C th thot ra knh, mng, sng ngi
2.7.6. Ngun in
Quan trng tng t l vic cp in n cng trnh, gi in v gi xy lp cng
trnh in. Ngoi nc th in l hng mc c nh hng ln n vn u t xy dng v c bit
l vn hnh sau ny nn cn c quan tm thch ng khi chn mt bng xy dng.
2.7.7. Bc xp
Cc kho lnh u cn c mt sn rng cho xe ti i li bc d hng, m bo c vic
bc d hng v khi lng cao nht, ng thi m bo cc mt hng ng lnh khng b nh
hng n thi gian bc xp. Dc theo chiu di kho cn b tr hin tu ho v hin t
cho cng mt lc c th bc xp nhiu toa hng v nhiu t. i vi kho lnh bn cng
cn phi c cu cng ca kho c th bc xp trc tip t tu vo kho trnh phi dng
phng tin vn chuyn trung gian.
Chng 3TNH CCH NHIT CCH M
3.1. Cu trc xy dng v cch nhit kho lnh.
3.1.1. Mc ch ca vic cch nhit phng lnh:
Nhit tk, trong khi nhit mi trng (tf > tk). lnh trong x nghip
ng lnh. Cu trc cch nhit chim 25 ->40 % chi ph xy dng x nghip. Do
phi c bit ch n vic chn cu trc cch nhit. Thit k v khi thi cng nu cu
to ca vch cch nhit l im cu trc xy dng cch nhit xu th n khng m bo ch
nhit v m theo yu cu lm tng s kh ngt sn phm, h hng sn phm v tng chi
ph sn xut lnh (tng chi ph vn hnh).
Do vy vic cch nhit cho kho lnh c xem xt v coi trng vn ny. c bit
i vi h thng kho lnh xy dng trong phng lnh lun lun phi duy tr nhit
thp.
Do s chnh lch nhit nh trn lun lun xut hin dng nhit xm nhp t ngoi
mi trng vo.
i vi kho lnh ca chng ta, mc ch xy dng gim dng nhit xm nhp t ngoi
mi trng vo trong kho, ch cn bng cch tng Rw ln.
RW : nhit tr ca vch (tc l cn tr dng nhit ) mun tng dng nhit tr
ca vch c nhiu cch nhng tt nht l xy tng dy ln mt cch ph hp nht lp vt
liu cch nhit.
*) ngha :
Vic cch nhit cho vch kho lnh n s lm gim bt hiu s nhit ca b mt
pha trong kho v nhit khng kh trong kho.
(t = tW2 tk Khi hiu nhit ln s lm tng s tun hon ca khng kh gn
vch, s tun hon khng kh tng ln lm tng s kh ngt ca sn phm vo ma h,
ngc li lm sn phm qu lnh vo ma ng .
trnh hin tng ny khi xp xp sn phm vo trong kho lnh khng c xp sn
phm vo st vch kho. T nhng l do trn vic cch nhit cho kho lnh rt l tt
yu.
3.1.2. Mc ch ca vic cch m : Nhit mi trng xung quanh bao gi ln hn
nhit ca khng kh trong phng lnh cho ln m (d=g/kg k3) ca khng kh xung
quanh ln hn phong lnh, kt qu pht sinh chnh lch cha m.
(d = dng - dn hay l p sut ring phn ca hi nc n sinh ra :
(p = pfh - pkh y l nguyn nhn to ra mi trng m trong vch kho lnh.
S chnh lch v p sut hi nc trong v ngoi to nn dng hi nc to nn dng hi
nc khych tn qua vch kho vo trong phng lnh n c nh gi qua thng s gi l
mt dng m ( .
( =
Trong :
Ph1 : p sut hi nc bn ngoi
Ph2 : p sut hi nc bn trong
H : Tr lc dn m m2sp/kg.
Vic chm dt hon ton dng nhit m i qua vch khi m lun lun tn ti (t v
(p l iu khng th thc hin c. V khi vch kho c tr lc nhit v m v cng ln
nhng nu tng mt cch hp l nhit tr v m tr v m tr th c th gim c dng
nhit v m.
gii quyt vn ny ta phi thc hin vic cch nhit v cch m ca kho lnh
.
Nu cho m xm nhp vo qua vch qua vch kho lnh gy ra mt s tc
hai:
- N lm m vt liu cch nhit lm gim kh nng cch nhit ca vt liu.
-N lm cho cc vt liu tham gia vo cu trc vo kho lnh lm t nhanh ,
mc nt.
-m i vo mang theo nhit vo lm tng nhit ti ca thit b lnh ln (tng
nhit ti ca bung) ng thi n lm tng kh nng mt khi lng ca sn phm (do
chuyn pha t lng sang hi ) . khc phc nhng tc hi nu trn ngi ta phi
cch m cho kho.
3.2. Cu trc ca cch nhit cch m. 3.2.1. Cu trc cch nhit:
Cu trc cch nhit m bo s lin tc khng to ra cc cu nhit hin tng t
nhit. i vi kho xy khi lp cch nhit cho cng trnh khng nn h cc mch ghp
gia cc tm cch nhit .
V tr lp t :
+ i vi tng cch nhit t pha trong hay pha ngoi u c c nhng bo v lp
cch nhit, cu trc tt th lp bn trong tng c li hn.
+ i vi nn lp di mt nn.
+ i vi trn th lp lp cch nhit pha trn hay pha di u c tu thuc vo
din tch.
Theo ti thit k ca em, em chn cu trc cch nhit l polystyrol
(styrofor) cch nhit cho kho (trn ,tng, nn).
3.2.2. Cu trc cch m:
V nguyn tc cu trc cch m lp v pha c m cao (v pha nng) .
Khi lp cu trc cch m cho kho em chn l nha ng v giy du dng cch m
cho tng, nn cn trn dng tn lp ng thi cng cch m.
3.3. Phng php xy dng kho bo qun
Trong thc t sn xut hin nay c 2 phng php xy dng kho thng s dng l
kho xy v kho lp ghp.
- Kho lp ghp : c u im l kch thc lp ghp tiu chun, thao tc lp ghp
d dng, cch m hon ton , thi gian thi cng ngn, hiu qu cao.tuy nhin n
c nhc im l gi thnh cao, chi ph u t ln , khng tn dng c ngun nhin liu
sn c ti a phng.
- Kho xy : c u im l c kh nng tn dng ngun nguyn liu sn c ti a
phng, cc nguyn vt liu sn c ca x nghip, gi thnh r, chi ph u t thp.
Tuy nhin n c nhc im l thi gian thi cng ko di cu trc xy dng phc
tp.
Qua cn i gia kho lp ghp v kho xy, i chiu vi tnh hnh ca x nghip
em chn phng n xy dng kho bo qun ng ca x nghip l kho xy.
3.3.1. Kt cu xy dng kho: gim tn tht lnh, cng nh m bo tnh an ton
v kinh t cho kho lnh hot ng trong thi gian di th kho lnh cn c xy
dng theo kt cu nh sau:
3.3.1.1. Mng v ct.
Mng phi chu c ti trng ca ton b kt cu xy dng v hng ho bo qun, bi
vy mng phi kin c, vng chc v lu bn. Mng c th lm theo kiu rm mng hoc
c th theo kiu tng khng lin tc. Khi mng ngi ta phi cha trc nhng l lp
ct chu lc. Trong kho lnh mt tng s dng ct c tit din vung
(400(400).
3.3.1.2. Tng bao v tng ngn.
C rt nhiu phng n xy dng tng bao tng ngn nhng phong php c in nht
cho n nay vn ph hp vi Vit Nam.
Tng gch chu lc c hai lp va trt hai pha. Cch nhit pha trong phng
lnh. Trc khi cch nhit ph ln tng mt lp bitum dy 2,5(3 mm cch m sau
dn lp cch nhit ln.
Cch nhit c th dn hai lp trnh cu nhit. Cch nhit c th c nh vo tng
nh inh mc bng thp. Np g.
i vi tng ngn c th cch nhit bng gch hoc bng btng bt cch nhit. Nu
hai phng c nhit qu chnh lch c th b tr cch nhit phng lnh hn.
3.3.1.3. Mi Cc kho lnh c cc tm mi tiu chun i km theo vi ct, rm ,
x tiu chun. Mi kho lnh khng c ng nc, khng c thm nc.
Nu kho lnh c chiu rng ln c th lm mi dc v mt pha, thng lm dc v
hai pha v c nghing 2%. Chng thm nc bng bitum v giy du. Chng bc x mt
tri bng cch ph ln trn cng mt lp si trng kch thc 5(15 mm.
i vi kho lnh em thit k ngoi vic b tr nh trn cn b tr thm lp mi lp
bng b l xi mng hoc bng thp.
3.3.1.4. Nn Kt cu nn ph thuc vo nhiu yu t ;
- Nhit phng lnh;
- Ti trng ca kho hng bo qun;
- Dung tch kho lnh;
Yu cu ca nn kho lnh phi vng chc , tui th cao ,v sinh sch s, khng
thm nc.
Theo tiu chun th nn c nhit dng khng cn cch nhit.Nu nn c nhit m
khi c nhiu phng n thit k khc nhau;
Vi kh hu vit nam th nhit tng i cao ngay c khi ma ng vy vi nhng
kho lnh m c nhit m nh th cng khng nht thit phi dng in tr si nn
.Nhng nhng kho lanh c nhit m cao thi trnh xy ra ng m nn ta c th b
tr thm in tr si nn. 3.3.1.5. Ca kho lnh
Cc kho lnh c rt nhiu loi khc nhau, kho ca cng c nhiu loi hc
nhau. Ca kho lnh lp ghp ging ca ca t lnh. Ca l mt tm cch nhit, c bn
l t ng, chung quanh c m kn bng cao su, c b tr nam chm mnh ht mnh ca
m bo kn v gim tn tht nhit.Ca mt cnh c chiu rng 1m v ca hai cnh c
chiu rng 1.8 m.
Vi kho ca em chon ca cho xe nng h chn ca rng 3m v cao 2.3m ca b
bnh xe chuyn ng trn thanh ray st tng nn ng m nh nhng, tit kin din
tch.
3.4. Vt liu cch nhit
Cch nhit lnh c nhim v hn ch dng nhit tn tht t ngoi mi trng c
nhit cao vo bung lnh c nhit thp qua kt cu bao che. Cht lng ca vch
cch nhit ph thuc ch yu vo vt liu cch nhit theo cc yu cu di y:
H s dn nhit ( nh (( -> 0);
Khi lng ring nh;
thm hi nc nh (( -> 0);
bn c hc v do cao;
Bn nhit thp v khng n mn cc vt liu xy dng tip xc vi n;
Khng chy hoc khng d chy;
Khng bt mi v khng c mi l;
Khng gy nm mc v pht sinh vi khun, khng b chut, su b c ph;
Khng c hi i vi c th ngi;
Khng c hi i vi sn phm bo qun, lm bin cht v gim cht lng sn
phm;
Vn chuyn, lp rp, sa cha, gia cng d dng;
R tin v d kim;
Khng i hi s bo dng c bit.
Trn thc t khng c cc vt liu cch nhit l tng p ng y a cc yu cu trn.
Mi vt liu c u v nhc im c th. Khi chn mt vt liu cch nhit cho mt trng
hp ng dng no cn phi li dng c trit cc u im v hn ch n mc thp nht cc
nhc im ca n.
Yu cu quan trng nht i vi vt liu cch nhit l h s dn nhit phi nh.
Vt liu cch nhit phn ln l cc vt liu phi kim loi v c v hu c dng xp
ngm cc bt khng kh hoc ngm cc bt kh no .
H s dn nhit ( ca vt liu cch nhit c tnh cht gn ging nhau v ph
thuc vo:
Khi lng ring;
Cu trc ca bt xp (kiu, ln, cch sp xp ca cc l cha kh, thnh phn v
cu to ca phn rn v mi quan h qua li ca chng);
Nhit ;
p sut v cht kh ngm trong bt xp;
m, khuch tn hi nc v khng kh trong thi gian s dng.
Khi lng ring ca vt liu l khi lng ca 1m3 vt liu tnh c phn rng cha
kh. H s dn nhit ca vt liu v c c to nn phn rn ca bt xp, khi lng ring
cng b, th tch rng cha kh cng ln v h s dn nhit ( cng nh. Tuy nhin
khi lng ring cng nh bn c hc cng thp. m bo bn c hc, khng th gim khi
lng ring xung tu . V d polystiron cch nhit cn khi lng ring bng hoc
ln hn 25 kg/m3.
H s dn nhit ca vt liu cch nhit cng nh kh cc l ngm kh cng mn, v
khi dng nhit do i lu khng kh trong cc l gim.
H s dn nhit gim khi nhit gim.
p sut ca cc cht kh cha trong cc l xp cng nh, h s dn nhit cng nh.
Chn khng c kh nng cch nhit tt nht nhng kh thc hin v s khuch tn m v
khng kh vo vt liu. Ch c th thc hin c cch nhit chn khng trong cc bnh
hay chai v thu tinh hoc bng thp (phch , phch nc, phch lng tnh, chai
cry) chu c p lc khng kh v chng c khuch tn hi nc v khng kh.
3.5. Tnh ton cch nhit kho lnh:
3.5.1. Kt cu tng bao Bng 3-1: Chn kt cu vch tng baoSTTVt liuB dy
( (m)H s dn nhit ( (w/m2k)H s khuch tn ( g/mhMpa
1Lp va xi mng0,020,8890
2Lp tng gch0,20,81105
3Lp va xi mng0,020,8890
4Lp bitum cch m0,0040,330,86
5Lp vt liu cch nhit polistyrol(cn=?0,0477,5
6Lp va cng tm thp0,020,8890
Trong :
1-3: Lp va xi mng
2: Lp tng gch
4: Lp bitum cch m
5: Lp polistyrol cch nhit
6: Lp va xi mng cng thp
Xc nh chiu dy lp cch nhit tng bao:
Chiu dy cch nhit ca lp vt liu c xc nh t phng trnh h s truyn nhit
k:
Ta c:
(cn: dy lp cch nhit polystirol
(cn: h s dn nhit ca polystirol
k: h s truyn nhit qua tng bao, ng vi kho nhit ta c k= 0,29
w/m2k.
(1: h s ta nhit b mt ngoi tng ngn, (1= 23,3 w/m2k
(2: h s ta nhit ca vch pha trong kho lnh, i vi kho lnh khng kh i
lu cng bc (2= 9 W/m2K.
(i: b dy ca lp vt liu th i.
(i: h s dn nhit ca vt liu th i.
Theo kt cu vch nh trn v da vo bng 1 ta c chiu dy lp cch nhit
l:
Chiu dy cch nhit thc phi ln hn hoc bng chiu dy xc nh c. y ta chn
chiu dy tng l 160 mm.H s truyn nhit thc c tnh:
3.5.2. Kim tra ng sng vch tng bao Mt dng nhit tnh theo nhiu cch
trong c hai cch sau y:
q = k(t1 t2)
q = (1(t1 tw1)
=>
iu kin kho khng b ng sng l:
tw1 > ts
=>
Nhit ng sng ts tra theo t1 v trn th Molier h x ca khng kh m p
sut kh quyn (760 mmHg) c tnh ti an ton, thc t ngi ta ly h s truyn
nhit ng sng lm chun:
Theo bng nhit trung bnh thng nng nht Thnh ph H Ch Minh l t1=
37,3oC; m ( = 74%. Tra th h-x ta c ts = 32,5oC. Nhit bung lnh -2oC,
(1 theo bng 3-7 l 23,3 W/m2K.
Nh vy vch ngoi khng b ng sng.
3.5.3. Kim tra ng m trong c cu cch nhit iu kin m khng ng li
trong lp cch nhit (lm t kt cu cch nhit, lm tng kh nng trao i nhit)
l p sut ring phn hi nc thc t lun phi nh hn p sut bo ha hi nc mi im
trong c cu cch nhit:
px < phmax
Ta i xc nh px:
Do mt dng nhit qua mi im trong vch l nh nhau v bng mt dng nhit
qua tng bao:
Mt dng nhit qua kt cu cch nhit:
q= k(t = 0,257 x (37,3 (-2)) =10,1 W/m2
Nhit b mt cc lp vch: q = q1= (1 x (tf1 t1)
t1 = tf1 q/(1 = 37,3 10,1/23,3 = 36,86oC
t2 = t1 - q = 36,86 10,1 x 0,02/0,88 = 36,60C
t3 = t2 - q = 36,6 - 10,1 x 0,2 /0,81 = 34,10C
t4 = t3 - q = 34,1 -10,1 x 0,02/0,88 = 33,80C
t5 = t4 - q = 33,8 - 10,1 x 0,004/0,33 = 33,60C
t6 = t5 - q = 33,6 - 10,1 x 0,16 /0,047 = -0,78oC
t7 = t6 - q = -0,78 - 10,1 x 0,02 / 0,88 = -1,01 0C
q = (2 x (t7 - tf2 )
tf2 = t7 q/(2= -1,01 10,1/9 = -2,13oC T nhit tnh ton c ta tra
bng tnh cht ca khng kh m (bng 7-10 ti liu tham kho [ 17] mi cht
lnh) ta c bng p sut hi bo ha theo bng sau:Bng3-2: p sut bo ha theo
nhit
Vch 1234567
Nhit toC36,836,634,133,833,6-0,78-1,01
p sut phmax, bar6270615553945292522415231500
Tnh phn p sut thc ca hi nc Dng hi thm thu qua kt cu bao che:
Ph1 v ph2 phn p sut hi ca khng kh bn ngoi v bn trong phng;
Ph1 = Px x (t=37,30C) x ( = 6371 x 0,74 = 4714,54 pa
Ph2 = Px x (t=-20C) x ( = 517 x 0,6 = 310,2 pa
H: tr khng thm hi ca kt cu bao che:
H = (TL1)
H= 3 + + + =0,0285 m2hMpa/g
Phn p sut thc ca nc trn b mt Px2 = Ph1 - ( = 4714,54 - x 106 =
4680,2 pa
Px3 = px2 - ( = 4680,2 - x 106 = 4385,9 pa
Px4 = px3 - ( = 4385,9 - x 106 = 4351,5 pa
Px5 = px4 - ( = 4351,5 - x 10-6 = 3632,8 pa
Px6 = px5 - ( = 3632,8 - x 106 = 336,8 pa
Px7 = px6 - ( = 336,8 - x 106 = 302,5 pa
Phng n ny t yu cu v tt c cc phn p sut thc nh hn p sut bo ha.
3.5.4. Xc nh chiu dy cch nhit nnBng 3-3: Kt cu cch nhit ca
nn
STTTn vt liuB dy ( (m)H s dn nhit ( (w/mk)
1Lp nn nhn bng cc tm b tng lt cng thp0,041,4
2Lp nn b tng0,11,4
3Lp cch nhit bng x l
(cn=?0,29
4Lp b tng t in tr0,10,88
5Lp bitum cch m0,0030,3
6Lp b tng dmO,151,28
Xc nh chiu dy cch nhit cho nn kho lnh i vi nn c si ta ch cn tnh
cc lp trn xp c si:
(cn = (cn x
Theo sch hng dn thit k h thng lnh (Nguyn c Lng) ta c cc s liu
sau:
Kn= 0,41 W/m2K
(1 = 23,3 W/m2K
(2 = 9 W/m2K
(cn = 0,29 W/mK
Vy b dy vt liu cch nhit l:
(cn = 0,29 x =0,179 m
3.5.5. Xc nh kt cu trn kho lnh Theo thc t kho lnh thng c kt cu
theo bng sau:
Bng 3-4:
STTVt liuChiu dy (cn (m)H s dn nhit ( (W/mK)H s khuch tn m(
(g/mhMpa)
1Lp ph ng thi l lp cch m0,0120,30,86
2Lp b tng0,041,430
3Lp cch nhit gm si t st(cn =?0,16226
4Tm cch nhit polystirol0,10,0477,5
5Lp b tng ct thp chu lc0,221,530
Xc nh chiu dy cch nhit cho trn kho lnhChiu dy cch nhit c xc nh
qua phng trnh truyn nhit:
(cn =(cn x
Vi : (1 =23,3 W/m2K (2 =9 W/m2K
Kt =0,257 W/m2K
(cn =0,16 W/mK
(cn =0,16 x
(cn = 0,22 m
Vy chiu dy cch nhit l: 0,22 +0,1 = 0,32 m.
1- lp ph ng thi l lp cch m
2- lp b tng
3- lp cch nhit si & ct
4- tm cch nhit
5- cc tm be tng ct thp
Kim tra ng sng cho trn:
iu kin m khng ng li trn mt ngoi trn:
t1 > ts
Vi:
ts tra c ts= 32,5 oC
t1 nhit b mt vch v c xc nh nh sau:
Do mt dng nhit khng i khi i qua mi im trn b mt vch nn ta c:
q = q1 =k x (t =0,257 x (37,3 -(-2) =10,1 W/m2 Ta li c:
q1 = (1 x (t
10,1= 23,3 x (37,3 t1)
=> t1= 37,3 10,1/23,3 = 36,8 oC
Ta thy t1 > ts. Vy vch khng xy ra ng sng.
Kim tra ng m trong kt cu cch nhit trn kho lnh iu kin m khng ng
li trong vch l Px < Phmax.
c xc nh nh sau:
Mt dng nhit do kt cu cch nhit gy ra:
q = k x (t = 0,257 x (37,3 ( -2)) = 10,1W/m2 Xc nh nhit tng lp
trong vch:
Ta c:
q= (1 x (tf1 t1)
Vy:
t1 = tf1 - q/(1 =37,3 - 10,1/ 23,3 =36,8 0C
t2 = t1 q x (1 /(1 = 36,8 - 10,1x 0,012/0,3 =36,390C
t3 = t2 qx (2/(2 = 36,39 - 10,1 x 0,04/1,4 = 36,1 0C
t4 = t3 - q x (3 /(3 = 36,1 - 10,1 x 0,4/0,16 = 10,85 0C
t5 = t4 - q x (4 /(4 = 10,85 - 10,1 x 0,1/0,044 = -12,1 0C
t6 = t5 - q x (5 /(5 = -12,1 - 10,1 x 0,22/1,5 = -13,58 0C
tf2 = t6- q/(2 = -13,58 - 10,1/9 = -14,7 0C
T nhit tnh ton ta tra bng tnh cht vt l ca khng kh m. Ta c p sut
bo ha trong bng sau:Bng3-5: Tnh cht vt l ca khng kh m 2
Vch 123456
Nhit oC36,836,3936,110,85-12,1-13,8
p sut Ph max pa61805885,65846,41518,9958,9611,1
Xc nh p sut thc ca hi nc:
Dng hi m thm qua kt cu bao che:
Ph1 v Ph2 phn p sut hi ca khng kh bn ngoi v bn trong phng;
Ph1 = Px x (t=37,30C) x ( = 6371 x 0,74 = 4714,54 pa
Ph2 = Px x (t=-20C) x ( = 517 x 0,6 = 310,2 pa
H: tr khng thm hi ca kt cu bao che:
H = (TL1)
H = =0,037 m2hMpa/g
Px2 = ph1 -( =4714,54 - x 106 = 3054,1 pa
Px3 = px2 - ( =3054,1 x 106 = 2895,4 pa
Px4 = px3 - ( = 2895,4 - x106 =2726,9 pa Ta thy Px4 > Px4, nn
ti lp ny s xy ra hin tng ng m. khc ph hin tng ny ta thay lp cch m
bitum bng polyetylen c dy 1mm v ( = 0,0018 g/mhMpa.
H = = 0,56 g/m2h
= =(4714,54 310,2) x 10-6/0,56 =0,0078
Xc nh phn p sut thc trn b mt vch:
Px2 = ph1 -( =4714,54 - x 106 = 381,2 pa
Px3 = px2 - ( =381,2 x 106 = 370,8 pa
Px4 = px3 - ( = 370,8 - x106 =359,7 pa
Px5 = px4 - ( = 359,7 - x106 =302,5 pa
Vy tt c cc px2 , px3 ,px4, px5 u nh hn px2, px3 ,px4,px5 =>
vch s khng xy ra ng m.
3.5.6. Xc nh chiu dy cch nhit tng ngn:
V c bn bung c cng nhit nn ta c:
K = 0,58 W/m2K
(1 =(2 =9 W/m2K
V tt c px2 , px3 ,px4, px5 u nh hn Px2 , vy ta chn b tng bt lm
cch nhit, khi h s dn nhit l ( = 0,15 W/ mK.
Vy chiu dy cch nhit ca tng ngn:
(cn =0,15 x =0,19 m
Chng 4TNH NHIT TI V CHN H THNG4.1. Tnh nhit ti 4.1.1. Mc ch.
Tnh nhit ti l tnh ton cc dng nhit t mi trng bn ngoi i vo kho
lnh. y chnh l dng nhit 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 kho lnh l xc nh nng sut lnh ca
my lnh.
4.1.2. Tnh nhit ti
Nhit ti ca kho xc nh theo cng thc.
Trong :
Dng nhit qua kt cu bao che ca bung lnh.
Dng nhit do sn phm to ra trong qu trnh x l lnh.
Dng nhit t cc ngun khc khi vn hnh my lnh.
4.1.2.1. Dng nhit qua kt cu bao che Q1.
L dng nhit tn tht qua tng bao, trn v nn kho lnh 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.
Trong Dng nhit qua tng, trn v nn do chnh lch nhit .
Dng nhit qua tng, trn do nh hng ca bc x mt tri.
Dng nhit truyn qua vch, trn v nn do chnh lch nhit Q11. Chiu dy
ca tm panel tiu chun l:
Kch thc tnh ton ca kho lnh l:
Chiu di kho lnh L=24m Chiu rng kho lnh l R=10 m Chiu cao ca kho
lnh l H=5 m Ta c dng nhit truyn qua vch, trn v nn kho lnh l:
Chnh lch nhit bn trong v bn ngoi kho lnh, xt vch v trn
Chnh lnh nhit bn trong v di nn kho lnh, chon nhit di l 20oC
Do trn kho chu bc x mt tri chiu vo mi kho lnh lm bng tn nn phn
khng kh pha di mi tn b bc x mt tri nung nng hn nhit bn ngoi tri
khong 100C
Vy dng nhit truyn qua vch, nn, trn l:
Trong :
H s truyn nhit thc ca kt cu bao che, xc nh theo chiu dy cch nhit
thc (xc nh chng trc W/m2K). Din tch kt cu bao che ca vch v trn l
580m2, din tch nn l 240m2 Hiu nhit bn trong v bn ngoi kho lnh
0C
Vy: = 0,257 x 580 x 39,3 =5858W
= 0,257 x 240 x 22 = 1356 W
Dng nhit qua vch kho lnh do nh hng ca bc x mt tri.
Do kho lnh nm trong phn xng nn c h thng tng bao che chn nn khng
chu nh hng ca bc x mt tri. Do W
= 5858 + 1356 +0 = 7214 W4.1.2.2. Dng nhit do sn phm v bao b to
ra.
W
Trong :
: Dng nhit do sn phm to ra W : Dng nhit do bao b to ra W Dng
nhit do sn phm to ra. Ta c:
Trong :
: Entalpi ca sn phm nhit vo kho v nhit bo qun trong kho
Kj/kg.
M: Khi lng hng ho nhp vo kho bo qun trong 1 ngy m. i vi kho bo
qun th t/ngy m.
Ch : hng ho bo qun trong kho bo qun c cp ng n nhit bo qun . Tuy
nhin trong thi gian x l nh ng gi, vn chuyn, nhit sn phm tng ln t
nhiu nn i vi sn phm bo qun ng ly nhit vo kho ti tm sn phm l
-170C
Nh vy c tra thuc dng c bo nn (tra bng 4-2 sch Hng dn thit k h
thng lnh) ta c.
j/kg , chn nhit khi a rau vo l 20oC
j/kg v t2 = - 20C
Do
Dng nhit do bao b to ra. Dng nhit do bao b to ra tnh theo cng
thc:
Trong :
: Khi lng bao b a vo kho cng sn phm
(t/ngy m) : Nhit dung ring ca bao b. (do y l bao b cacton)
t1, t2: Nhit trc v sau khi lm lnh ca bao b
Ta chn:
t1 = 200C, bng nhit rau khi a vo kho
t2 = -20C
Vy ta c
Vy dng nhit do sn phm v bao b to ra l:
4.1.2.3. Dng nhit do vn hnh Q3 c xc nh theo cng thc:
Trong :
: Dng nhit do n chiu sng (W) : Dng nhit do ngi lm vic to ra
trong kho (W) : Dng nhit do ng c in to ra (W) : Dng nhit do m ca
(W)
: Dng nhit do x tuyt (W)
Dng nhit do n chiu sng to ra Q31 Dng nhit do n chiu sng to ra xc
nh theo cng thc:
F: Din tch bung F = 240m2 A: Nhit lng to ra khi chiu sng trn 1m2
din tch bung W/m2 Chn A = 1,2 W/m2 ( do y l kho bo qun ng )
Vy
Dng nhit do ngi to ra Q32.
Dng nhit do ngi to ra xc nh theo cng thc:
Nhit lng do 1 ngi to ra khi lm vic nng nhc l 350W/ngi
n: s ngi lm vic trong bung. Ta chn 2 ngi lm vic trong bung
Vy .
Dng nhit do ng c in to ra.
(W)
N Cng sut ng c in.
1000 H s chuyn i t KW ra W. Tng cng sut ca ng c in qut dn lnh lp
t trong kho lnh phi ly theo thc t thit k. Tuy nhin n y ta cha chn c
dn lnh nn cha bit c th tng cng sut ng c in ca qut dn lnh, v vy c th
ly theo nh hng nh sau: i vi kho bo qun lnh ly N = 2 KW. Vy dng nhit
tn tht do ng c qut dn lnh ta ra:
Q33 = 2KW = 2000 W.
Vy dng nhit do ng c in to ra l:
W
Dng nhit do m ca Q34.
Dng nhit do m ca xc nh theo cng thc.
(W)
Trong : B: Dng nhit khi m ca, ta chn dng nhit khi m ca l
F: Din tch ca bung lnh.
Vy
Dng nhit do x tuyt Q35.
Trong kho lnh khi x tuyt ta thc hin trn mi dn lnh nn ta ch vic
tnh ton cho 1 dn lnh .
Dng nhit do x tuyt c xc nh theo cng thc:
(W)
Trong :
: Khi lng ring ca khng kh.
V: Dung tch kho lnh.
. Nhit dung ring ca khng kh.
. Nhit chnh lch trc v sau khi x tuyt.
Vy (W)
Vy dng nhit do vn hnh Q3 l:
(W)
Bng 4-1: Bng tng kt nhit ti
Dng nhitKt cu
bao che
Q1 WSn phm to ra
Q2 WMy v
thit b
Q3 WW
Tr s721419419,25059,3531692,55
4.1.3. Xc nh ti nhit v nng sut lnh cho my nn.
Ti nhit ca my nn cng c tnh ton t cc dng nhit thnh phn nhng tu
theo tng loi kho lnh c th ly mt phn tng ca ti nhit .
i vi kho lnh bo qun ta c.
W Nng sut lnh cho my nn c tnh theo cng thc.
Trong :
Nng sut lnh ca my nn (W)
k: H s tnh n tn tht ng ng v thit b ca h thng lnh.
Chn k = 1,07 b: H s thi gian lm vic (chn b = 0,9)
Vy (W) 35 KW4.2. Chn cc ch lm vic v tnh chn thit b4.2.1. Chn cc
thng s lm vic.
Ch lm vic ca h thng lnh c c trng bi 4 yu t sau:
- Nhit si ca mi cht lnh to.
- Nhit ngng t ca mi cht tk.
- Nhit qu lnh tql .
- Nhit hi ht v my nn hay nhit qu nhit tqn , th. Chn nhit si ca
mi cht lnh t0. Nhit si ca mi cht lnh ph thuc vo nhit bung lnh.
Nhit si ca mi cht lnh ly nh sau:
Trong :
tb: Nhit ca bung lnh tb = -20C
: Hiu nhit yu cu. . Chn
Chn nhit si ca mi cht l 100C Nhit ngng t tk. Do y l dn ngng gii
nhit bng khng kh nn hiu nhit trung bnh gia mi cht lnh ngng t v khng
kh l . Chn l 30C.
Trong y l nhit khng kh ly trung bnh trong nm Thnh Ph H Ch
Minh.
Nhit qu nhit tqn.
L nhit ca mi cht trc khi vo my nn. Nhit hi ht bao gi cng ln hn
nhit si.
chn l chnh lch nhau 100C
Vy
Ta chn nhit qu nhit nh vy do y khng c thit b qu nhit m ch qu
nhit do tn tht nhit trn ng ng ht t thit b bay hi v my nn.
Nhit qu lnh tql y l nhit mi cht lng trc khi vo van tit lu. Do qu
trnh qu lnh v qu nhit xy ra rt t nhin nn ta c phng trnh sau:
Trong :
l entalpi ti cc im nt trn s sau
Do:
tqn = 00C
V to = -100C
Nn tra trn th lgP-i ta c:
T tk= 40,30C ta tra th lgP i ta c:
Thay vo phng trnh trn ta c:
Tra th c:
tql = 370C
Vy nhit qu lnh l 370C
4.2.2. Tnh chu trnh my lnh.
4.2.2.1. Chu trnh my lnh.
Thuyt minh h thng
Hi mi cht sau khi sinh ra thit b bay hi, c nhit to v p sut Po,
lng hi ny s b tn tht nhit do ng ng dn gas nn nhit s tng ln nhit t1
v p sut P1. Sau n s c my nn ht v v nn nn n nhit v p sut t2 v P2.
Sau n s qua dn ngng ti thit b ngng t ny mi cht s c gii nhit bng h
thng qut dn ngng y mi cht s thc hin nhim v chuyn pha t pha hi sang
pha lng v h nhit xung tk v gi nguyn p sut Pk. Sau n s c qu lnh bng
do tip xc vi ng ng ht ca my nn nn nhit ca gas s gim xung cn t3.
Sau gas s qua thit b van tit lu v ti y van tit lu s lm nhim v h
nhit ng thi h p sut ca gas lng ny xung v tr 4 (t4, P4). Sau n qua
dn bay hi trao i nhit vi sn phm chuyn pha t pha lng sang pha hi.
Sau c my nn ht v v tip tc mt hnh trnh khp kn.
S thay i mi cht trong h thng.
11: Qu trnh qu nhit hi ht.
1-2 : Qu trnh nn on nhit t p sut Po n Pk
2-3: Qu trnh ngng t.
33: Qu trnh qu lnh mi cht trc khi vo van tit lu.
34: Qu trnh tit lu ng entalpi.
4 1: Qu trnh bay hi ng p.
Bng 4-2: Cc tng hp cc thng s trn cc im nt ca chu trnh.
Thng s
im ntNhit
0Cp sut
MPaEntalpy
Kj/kgTh tch ring
m3/kg
1
1
2
3
3
4-10
0
40,3
40,3
17
-100,37
0,37
0,84
0,84
0,84
0,37701
710
731
520
490
4900,065
0,07
0,035
.
.........-----------
4.2.2.2. Tnh chu trnh my lnh.
Qua vic tnh ton nhit kho lnh ta xc nh c nhit ti Q0MN. y cng l
nng sut lnh m my nn phi t c duy tr nhit lnh yu cu trong bung
lnh.
T nng sut lnh Q0MN = 35(KW) ta phi tnh nhit v chn my nn theo cc
bc sau.
Nng sut lnh ring q0 (kj/kg).
(kj/kg).
Trong :
qo: Nng sut lnh ring (kj/kg) : Entalpi ti im 1 v im 4 ca chu
trnh.
(kj/kg).
Lu lng mi cht mtt (kg/s).
(kg/s)
Th tch ht thc ca my nn Vtt (m3/s).
(m3/s).
H s cp
Ta c
Trong :
H s cp my nn
p sut ht v ngng ca h thng MPa.
Ta chn MPa
m = 0,91,05 Ta chn m = 1
c: t l th tch cht c = 0,030,05 Ta chn c = 0,04.
Th tch ht l thuyt .
(m3/s). Cng nn on nhit .
KW.
Hiu sut ch th.
Trong
(w: L h s tn tht khng thy c (w = .
b = 0,001.
Cng sut ch th .
(KW).
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
nn.
Ta c Nms = Vtt x Pms, KW
Pms: vi my nn freon ngc dng th.
Pms = (0,019 ( 0,034)MPa.
Ta chn Pms =0,02 MPa.
Vy Nms= 0,018 x 0,02 x 106 = 360 (W) = 0,36 KW.
Cng sut hu ch. Ta c: Ne = Ni + Nms = 4,179 + 0,36 = 4,539 KW
Cng sut in.
Cng 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.
Ta c. , KW
Trong : (td - l hiu sut truyn ng ai (td = 0,95.
(el - l hiu sut ng c. (el =0,8(0,95
Vy: KW
Cng sut chn ng c.
Ta c: Ndc = (1,1 ( 2,1 ) x Nel KW;
Chn h s an ton l 1,2.
Nn ta c:
Ndc = 1,2 x 5,3 = 6,37KW.
Nhit thi ra thit b ngng t.
(W).
4.2.3. Tnh chn thit b4.2.3.1. Chn cm my nn dn ngng.
Do qu trnh tnh ton tnh Qo = 35 KW v cng sut ng c Ndc = 6,37 KW
nn ta chn h thng my nn v dn ngng nguyn cm do hng Bitzer ca c sn xut
vi cc thng s sau:
Model:LH135/4N.2-S
Th tch qut:56,1 m3/h
Cng sut ng c:11 KW
Nng sut lnh:11,2 KW
Ghi ch:
LH135 - Kiu dn ngng.
4N.2 - Kiu dn lnh.
y l my nn mt cp. Vi cc thng s trn phc v cho kho lnh 300 tn ta
phi cn 1 h thng cm my nn v dn ngng s m bo bo nng sut lnh.
4.2.3.2. Chn dn lnh.
Dn lnh l mt thit b trao i nhit trong gas lng thu hi nhit bc
hi.
Dn lnh ti chn l dn lnh khng khi i lu cng bc, t tn din tch trong
kho, nhit trong bung u, h s trao i nhit ln, nhng nhc im l n v tn
nng lng cho qut ca dn lnh.
Do Qo = 35KW nn nng sut kho lnh phi t t nht l 35KW. Nn ta chn dn
lnh do hng Gao Xiang Trung quc sn xut. V nng sut dn lnh ch c 9,2 kW
nn phi cn 4 dn lnh Dn lnh c chn vi cc thng s sau: Bng 4-3: Thng s
dn lnhK hiuNng sut lnh
KWDin tch trao i nhit m2Lu
lng
m3/hKhong thi
mThng s ca qutin tr si
Cng sut, dng in, ngun in
V/HzWAV/HzKW
GX-LE403-15009,257,31270515230-400/504501,65200/509,96
Ghi ch:
GX-LE 40 3-1500
4.2.3.3. Tnh chn thit b ngng t a) Chn kiu dn ngng :
Vic tnh ton thit b ngng t thc cht l xc nh din tch b mt trao i
nhit . Vi ti ca em chn kiu bnh ngng gii nhit bng nc , vi thit b gn
nh c th lp ngay trong phng my .
b) Xc nh nhit ti ca dn ngng:
Nhit ti ca dn ngng c xc nh qua biu thc :
Qk =K x F x (ttb (TL1)
Vi :
Qk : Ph ti nhit ca thit b ngng t. KW
F : Din tch b mt trao i nhit. (ttb: Hiu nhit trung bnh logarit
.K
Ta c :
Qk =39,179 KW
iu chnh lng nc vo lm mt sao cho tw1 = 200C v lng nc ra tw2 =
280C. khi hiu nhit logarit s l:
(ttb = (TL1)
Vi:
(tmax =tk tw1 =40,3 20 =20,30C
(tmim =tk tw2 = 40,3 28 =12,30C
Vy:
(ttb = =20,3-12,3/ln1,65 = 16 K
Vy din tch b mt chuyn nhit ca bnh ngng ng chm nm ngang l: (theo
bng 8.6 TL1) ta c :K = 700 ( W/m20K)
F =Qk/(K x (ttb) =39,179 x 1000/(16 x 700 )= 3,5 ( m2)
Chn kiu bnh nhng ng chm nm ngang , freon c cc thng s nh sau:
Bng 4-4: Thng s thit b ngng tBnh ngngDin tch b mt ngoi, m2ng knh
ng v ,mmChiu di ng, mS ngTi nhit max, KWS li
KTP-123,53771,28643,34;2
4.2.3.4. Tnh chn cc thit b ph.
4.2.3.4.1. Tnh chn van tit lu.
Dn bay hi c nhiu ng nhnh phn phi mi cht v mc tn tht p sut trong
dn bay hi ln nn m bo cung cp mi cht cho dn lnh nn y ti chn v vic
chn van tit lu t ng cn bng ngoi cho kho bo qun cn c vo cc thng s
sau:
Nhit ngng t: tk = 40,30C.
Nhit qu lnh: tql = 37 0C.
Nhit bay hi: ts = -10 0C.
Nng sut lnh: Qo = 35 KW .
- Xc nh p sut u vo van tit lu:
p sut ngng t 40,3 0C l: 1,5 MPa = 217,5 PSI.
Tr tn tht p sut trn ng cp lng: 2 PSI.
Tr tn tht do ct p thy tnh 10 feet: 5 PSI.
p sut u vo van tit lu: 224,5 PSI.
- Xc nh p sut u ra van tit lu:
p sut ca R22 10 0C l 0,37 MPa = 53,7 PSI.
Cng tn tht p sut trn ng ht: 2 PSI.
Cng tn tht p sut trn ng ht: 20 PSI.
(p sut u ra van tit lu: 75,7 PSI.
- Xc nh hiu p sut: (P = 224,5 75,7 = 148,8 PSI. Theo bng 8.2 (1
( ta chn van TCL 700H tit lu l van tit lu cn bng ngoi.
Cu to ca van tit lu nh sau: Van tit lu mng ch m khi trng thi mi
cht lnh ra khi thit b bay hi trng thi hi qu nhit. Gi f l din tch b
mt mng xp. Nu nhit ra khi mi cht l hi qu nhit th tqn > t0 do
nhit mi cht trong bu cm bin cng c coi l nhit qu nhit, khi trng thi
mi cht trong bu cm bin l hi bo ho tqn c p sut bo ho Pt. Phng trnh
cn bng lc: Pt. f = P0+R; (Pt P0). f = R khi trng thi mi cht sau khi
ra khi thit b bay hi ti bu cm bin l hi bo ho kh th van tit lu
ng.
Khi my mi chy th nhit qu nhit tqn tng i ln hn nhit t0 nn van tit
lu m ln.
Khi my dng th van tit lu ng li. Trong thc t cho my nn vn hnh c
an ton th trc van tit lu phi lp thm mt van in t lc my nn chy van in
t c in m ra cp dch cho dn bay hi, v my dng van in t ng li.
V tr lp t.
Van tit lu mng cn bng ngoi bao gi cng c lp t sau van in t v trc
dn lnh. N ch m khi trng thi mi cht sau khi ra khi thit b bay hi ti
bu cm bin phi l hi qu nhit.
4.2.3.4.2. Tnh chn bnh cha cao p.
Nhim v ca bnh cha cao p l cha gas lng sau khi ngng t phn phi n
cc dn lnh.
Bnh cha cao p c b tr v pha cao p v nm sau dn ngng. N gii phng b
mt truyn nhit ca dn ngng bi lp cht lng ng thi cung cp ng u lng cht
lng cho van tit lu.
Th tch bnh cha cao p chn nh sau:
Trong :
V: th tch bnh cha cao p m3 G: Lng tc nhn lnh i qua bnh cha cao
p.
G = mtt = 0,165 Kg/s
v3: Th tch ring cht lng nhit tk (m3/kg). m3/kg Vy m3 T th tch ca
bnh cha ta tnh ton th ta chn bnh cha vi cc thng s sau:
Th tch bnh: 0,3 m3 Chiu di bnh: 865 mm ng knh trong: 220mm ng
knh ngoi: 290mm4.2.3.4.3. Tnh chn bnh tch lng.
ng knh bnh tch lng c tnh nh sau:
Phng trnh cn bng lu lng.
Chn bnh tch lng c ng knh trong 172mm
4.2.3.4.4. Phin lc.
Phin lc c nhim v loi tr cn bn trnh hin tng tc van tit lu. Ngoi
ra cn c nhim v loi b cc Axid v cc cht khc ra khi vng tun hon mi cht
lnh. Phin lc c lp trn ng cp lng cho dn bay hi v c lp t trc van in
t.
4.2.3.4.5. Van in t.
Van in t l van chn c iu khin bng lc in t. Khi c in cun dy s sinh
ra lc in t ht li thp v y van ln, van in t m ra cho dng mi cht i
qua, khi khng c in van in t ng li ngng cp dch. Van ch c hai ch l ng
hoc m.
4.2.3.4.5. Tnh chn ng ng dn mi cht trong h thng.
Trong h thng lnh gm nhiu thit b ring bit, chng lin kt vi nhau nh
cc ng dn, v vy phi tnh ton la chn ng ng dn sao cho va bn v va tit
kim ng ng m bo yu cu k thut v kinh t.
Cng t cc yu t nh: tc lu ng cho php ca mi cht, lu lng ca dng mi
cht, khi lng ring ca mi cht T ta tnh ng knh ng dn.
ng knh trong ng c xc nh theo biu thc:
(m)
Trong :
m: Lu lng (kg/s). Khi lng ring ca mi cht (kg/m3).
Tc dng chy trong mi cht (m/s).
Trong h thng lnh ta cn xc nh 3 ng ng l ng ng ht t thit b bay hi
v my nn, ng ng y, v ng ng dn lng.
a) ng ng ht t dn bay hi v my nn.
Ta c:
m = 0,165kg/s
Theo bng 10 1 (TL1) ta c: m/s nn chn m/s
v1 = 0,07 m3/kg nn
Vy
Vy chn loi ng st c ng knh lm ng ng ht my nn. Chn dh = 40 mm. b)
ng ng y ca my nn t my nn n thit b ngng t.
Ta c:
m m = 0,165kg/s Theo bng 10 1 (TL1) ta c: m/s nn chn m/s
v2 = 0,035 m3/kg nn
Vy
Vy chn loi ng st c ng knh lm ng ng ht my nn. Chn dn =35 mm.
c) Tnh chn ng ng dn lng.
Ta c:
m m = 0,165 kg/s Theo bng 10 1 (TL1) ta c: m/s nn chn m/s
3 = 0,88*103 m3/kg nn
Vy
Vy chn loi ng st c ng knh lm ng ng ht my nn. Chn dl = 18mm.
Bng 4-5: Kt qu tnh ton ng ng chn.
ng ngng knh tnh c
mmKch thc chn
ng knh trong
mmng knh ngoi
mm
ng y
ng ht
ng dn lng
32381635
4018386321
Chng5:THI CNG LP T
5.1. Gia c v xy dng nn mng y l mt cng on quan trng trong qu trnh
xy dng kho, n quyt nh tnh vng chc v an ton ca kho. Mng c o su 70cm.
c ca cc ct b tng ct thp. Sau ta c cc ct b tng n chiu cao bng mt nn
kho thit k, tin hnh xy mng t vo nn to vng chc ca nn. Sau c lp b tng
chu lc v xy cc con ln bng gch.
5.1.1. c khung kho bng b tng ct thp.
Sau khi xy dng xong mng kho, nn kho tin hnh c cc ct b tng theo
chiu cao v kch thc thit k. Trn cng ca cc ct c lin kt vi nhau bng cc
dm b tng ct thp.
Cng vi vic xy dng khung ta tin hnh xy tng bao cho nhng tng cn
thit.
5..1.2. Dng khung mi v lp mi.
Sau khi c c khung b tng ca kho ta tin hnh dng khung st mi, lp cc
x dc theo chiu di ca kho v tin hnh lp tn. Sau khi c c b khung vng
chc cho vic lp ghp cc cu trc cch nhit.
5.2. Lp t kho lnh5.2.1. Cng tc chun b.
Trc khi lp t kho lnh th phi chun b dng c lp t cho y nh l: panel,
thanh nhm V v thanh thp ch U, tn rive, khoan, my ct
Chun b bo h lao ng cho ngi thi cng.
o c k trc khi lp t.
5..2.2. Thi cng lp t.
u tin ta lp phn panel vch trc nhng cha mt vch pha Ty Bc ra v vch
ny khi lp xong panel nn ta mi lp. Lp lun ca ra vo kho lnh v ca s.
Lp n panel nn. Lp panel vch cn li. Lp cc x gi panel trn. Lp panel
trn.5.2.2.1. Lp panel vch.
a). lp vch kho lnh.
t hai tm panel li gn nhau v dng c cu kho cam lp ghp n li. Cch lp
bng kho cam ta trnh by nh hnh v 4-1.
Sau khi lp xong phi bn keo silicon vo cc khe h gia hai tm panel
trnh m lt vo cc tm panel.
Sau cng phi cho nt che l a lc gic vo bng nt nha trnh m vo tm
panel.
Ch : khi cho nt vo ta phi bn keo vo nt cch li tm panel vi m bn
ngoi, v gi nt cho chc chn.
b). Lp panel vch gc kho lnh (hai vch vung gc vi nhau).
t hai tm panel nh hnh v 4-3.
Sau dng cc thanh thp ch V c nh hai tm li vi nhau. Cc thanh nhm
ny va c nh va chng m cho tm panel.
Dng cc con tn rive c nh thanh nhm ch V vi panel.
Cn mt vch ta lp panel nn trc ri mi lp vch c ( l vch pha Ty
Bc).
5.2.2.2. Lp ca ra vo v ca s.
y k c ca ra vo v ca s u dng loi ca kiu bn l.
o c xem v tr t ca nm u .
Dng my ct ct mt l ng bng kch thc ca .
t ca vo v tr .
Dng khoan khoan l v bn rive vo tm s 2 c nh ca vi panel.
5.2.2.3.Lp panel nn.
Lp panel nn nh hnh v.
Trc tin lp tm panel nn v vch trc. t hai tm panel vung gc vi nhau
sau dng thanh nhm mng ch V t gc v bn tn rive vo gi thanh thp c nh
hai tm panel li vi nhau. y thanh nhm ch V ny ch co tc dng chng m
cho tm panel thi.
Sau lp cc tm panel nn vi nhau. Cc tm panel nn c lp vi nhau bng c
cu kho cam nu mc trc.
5.2.2.4.Lp panel vch cn li.
Cch lp panel vch cn li ta lp nh hnh v 4-6.
5.2.2.5.Lp x gi panel trn.
Do panel trn khng c ct nn dng cc x gi cho trn kho khng b ri xung
di.
X treo ny thng dng thanh thp hnh ch U.
5.2.2.6.Lp cc panel trn.
Sau khi lp xong cc x ta tin hnh lp cc panel trn.
u tin lp cc trn pha Ty Bc trc cch lp trn ny nh hnh v 4-8.
Lp panel trn sau ta dng cc bu long d bt xuyn qua panel trn c nh
panel trn vi x treo hnh ch U, x treo gi panel trn khi b ri xung di
(Lp bulong d phi cho mt t keo silicon vo phn d p vo panel trn n gi
cho bulong d khng b xoay chuyn khi ta sit ai c pha trn).
Sau tin hnh bt thanh nhm s 9 v tn s 8 nh hnh v 4-8. Khi lp xong
panel trn u tin th lp panel tip theo cng hng tng t nh vy, nhng trc
khi bt bulong d phi hai tm panel gn nhau v khoa chng bng c cu cam
trc sau mi tin hnh lp bulong d vo v tng t nh trn.
Sau khi xong hng th nht phi cng dy cp bng c cu tng cho dy cp cng
ra gi panel tt hn.
Sau khi lp xong hng th nht tin hnh lp hng th hai. Lp hng th hai
thc hin theo hnh v 4-9.
`
t hai tm panel gn nhau v cng thc hin nh hnh v. Nhng do hai tm
panel ny khng c c cu no n khp vi nhau nn ch t chng gn nhau v dng
thanh nhm s 3 lp khe h ca hai lp panel .
Sau khi lp xong hng th hai ta tin hnh lp hng th ba. Lp hng th ba
tin hnh nh hnh v 4-10.
Do y l tng pha ng Nam nn n gip vi kho lnh th hai nn tin hnh lp
nh hnh v 4-10.
Sau khi lp xong panel trn hng th ba ny xong l hon thnh lp xong
kho lnh. V gi tin hnh lp t h thng lnh.
5.3. Lp t h thng lnh.
Do y l h thng lnh c trung bnh nn theo xu hng hin nay lp t chng
theo hai cm. Mt cm gm h thng my nn, dn ngng v cc thit b ph khc. Cn
cm my cn li l cm dn lnh v van tit lu.
5.3.1. Lp t cm dn ngng, my nn.
Lp t cm ny nh hnh v 4-11.
``
Trong lp t h thng th lp t cm ny l kh nht do n gm nhiu b phn quan
trng ca h thng nh my, nn, dn ngng, mch in, cc thit b bo v h thng Nn
phn ny thng lp trc xng xong xui, chy th xong xui th mi em n cng
trnh ch vic t n ln vi tr lp t l xong.
Do yu cu v nng v cng knh nn khi lp cm ny ta phi tch ri dn ngng v
cm my nn thnh hai. Khi a cm my nn vo v tr lp t ri mi a dn ngng ln.
Khi da dn ngng ln xong phi dng bulong-ai c sit cht chn dn ngng vo
khung ca cm my nn v cm my nn phi c c nh tht chc vo sn b tng. V khi
my hot ng n s to ra rung ng mnh nu khng c nh chc chn n s b dch
chuyn v gy nh hng n h thng.
Sau khi c nh xong cm my ny tin hnh lp ng ng ni t bnh tch du n dn
ngng v t dn ngng n bnh cha cao p.
Ch : Khi lp cm my ny vo sn b tng th phi o c sao cho cm my ny phi
cch tng khong 1m khi lp t ng ng ht khng b vng lm cho gi tr thm m
khng cao.
5.3.2. Lp t cm dn lnh.
Lp cm dn lnh ta thc hin theo hnh v 4-12.
Trc khi a dn lnh ln ta phi o c v tr lp t dn lnh cho ph hp. Sau
ta khoan l cho thanh thp ch U s 7 sao cho khong cch cc l ca n phi
bng khong cch cc l trn thanh thp ch U trn dn lnh.
Sau khi khoan l xong xui tin hnh treo thanh thp s 7 ln trn x g s
11 v a thanh ty 4 vo ng v tr nh hnh v, khi cho dn lnh ln ta ch vic
x thanh ty vo cc l trn thanh thp ch U s 3 v sit ai c vo l xong phn
lp t dn lnh.
Ch : Khi lp dn lnh ta phi ch y khong cch cha dn lnh v vch kho
lnh n phi cch vch khong 0,5m khng kh i lu c d dng m khng b vch cn s
i lu .
Sau khi lp xong dn lnh ln th ln nc kho lnh tng dy cp bng c cu
tng ln cho hp l.
5.3.3. Lp t ng ng ht ca my nn, v ng ng t bnh cha cao p n dn lnh,
bnh tch lng v van tit lu.
5.3.3.1.Lp t ng ng ht ca my nn v bnh tch lng.
ng ht ny dng bng ng thp nn ta lp t theo cc bc sau:
Trc khi lp t ng ng phi lm v sinh bn trong ng cho sch s (thng dng
gi lau v dng cy gy di lau).
o c v ct ng theo ng kch thc m o trc. Sau khi ct ng xong phi lau
li ng mt ln na mt st trong ng ra ngoi.
Lm cc gi treo ng (do y l ng st nn rt nng, phi lm gi treo ng phi
chu c trng lng ca ng ng).
a cc ng ln gi treo sao cho hp l.
Dng my hn in hn cc ch mi ni, cc co (ch : ch nhng th hn p lc c
tay ngh cao mi c hn).
Do bnh tch lng nm trn ng ht t dn lnh v mt nn nn trng qu trnh lp
ng ht my nn tin hnh lp lun bnh tch lng. Bnh tch lng ny l dng bnh
treo nn ta khng cn lm gi cho n m ch vic hn hai mi hn l ng ng t dn
lnh v bnh tch lng v t bnh tch lng v my nn nh hnh 4-13.
5.3.3.2.Lp ng ng t bnh cha cao p n dn lnh, v van tit lu.
ng ng ny nh nn dng loi ng ng. Lp t ng ng ng cng tng t nh lp t ng
ng st nhng n d dng hn. V khng phi lm gi treo ng.
Trc khi lp van tit lu phi tin hnh ui bi ng ng va lp. ui bi bng
cch dng kh N2 ui nh hnh v.
Sau khi ui bui xong th tin hnh lp van tit lu v van tit lu nm trn
ng dn t bnh cha cao p n dn lnh.
Cch lp van tit lu nh hnh v 4-14:
Trc ht lp c van tit lu ta phi bit c v tr lp t van tit lu l ngay
st thit b bay hi trn ng dn lng vo.
Lp t van theo ch dn ca mi tn trn thn van (ch : khng ng mao tip
xc vi cc ng khc).
Lp ng cn bng ngoi: Ta dng ng cn bng ngoi l ng ng 6. Lp ng 6 vo
van bng cch loe ng v dng c u cn sit cht n li. Cn lp u kia vo ng st
th phi ly b hn gi h nng mt phn ng st cho n nng n khi gn chy th cho
ng ng vo n khoan thng mt l va bng ng ng. Sau ta dng que hn ng thau
hn ng ng vo ng st.
Lp bu cm bin: V tr lp bu cm bin l t li hi ra khi dn bay hi (ng
st) v m bo tip xc tt vi ng ny dng bn kp bng nhm gi n c nh vo ng
st.
5.3.3.3. Lp t ng ng nc ngng.
ng nc ngng thng lp t bng ng nha PVC. Sau khi lp t ng nc ngng
xong ta phi bc cch nhit cho ng nc ngng ny. L do bc cch nhit l cho
khng xy ra ng bng trn ng ng nc lm h hi n ng nc, v khng cho nhit t
nc x ny nh hng ti dn lnh.
5.3.3.4. Qu trnh bc cch nhit ng ng.Sau khi th x h thng xong nu
khng b x ch no ta tin hnh bc cch nhit ng ng.
Bc ht phn ng t dn lnh v my nn. Trong qu trnh bc ng ng ta tin hnh
bc lun c bnh tch lng trnh tht thot nhit. 5.4. ui bi v th x, ht chn
khng v np gas h thng 5.4.1. Quy trnh ui bi h thng.
Do qu trnh ui bi ta thc hin i vi ng ng ri v cc thit b cm my nn,
v dn ngng nn by gi ta ch vic ui bi cc ng st na thi.
Qu trnh ui bi tin hnh nh sau:
M phn van ni vi van tit lu ra sau tin hnh t chai Nit v cho kh
Nit vo hng (hnh v 4-15).
M mt bch ca van ht my nn ra.
Ta tin hnh kt ni nh hnh v. Sau khi kt ni xong th mt ngi ng ch mt
bch v dng tay bt cht mt bch li, cn ngi th hai m van chai Nit ra.
Ngi m c khong 15 giy th ng van Nit li sau li m li khong 3 n 4 ln.
Cn ngi my nn th bt cht tay vo mt bch khi no thy kh Nit ra vi p lc
cao m tay khng gi c na th bung tay ra cho bi bay qua li , v tip tc
lm nh vy khong 3 n 4 ln na l xong.
5.4.2. Th x h thng.
Sau khi ui bi h thng xong tin hnh th x h thng.
Th x h thng ta cho kh Nit vo th. Cho kh Nit vo h thng pha cao p
l 16bar cn pha h p l 10bar.
Thi gian gi p sut l 12 gi. Trong 6 gi u p sut cho php h khng qu
10%, sau phi gi khng i.
Sau khi bm p sut bn pha cao p v h p th ta ng chai Nit li v dng
bt x phng th cc ch hn v cc mt bch ca my nn xem c b x ch no khng. Nu
m b x th phi x ht Nit ra ngoi v khc phc, hoc hn li, khi gii quyt
xong s c li bm Nit vo v lm li t u.
Cn nu qua thi gian th x m khng thy x ch no v p sut lun m bo th
phi x ht Nit ra v tin hnh ht chn khng h thng.
5.4.3. Ht chn khng h thng.
Qu trnh ht chn khng c trnh by hnh v 4-16.
`
Qu trnh ht chn khng kt ni nh hnh v 4-16. Sau khi dy gas kt ni vi
cc gic co A, B, D, E th tin hnh bt my ht chn khng cho n chy. Ht n
khi p sut ng h LP chi v vch 30mmHg th cho my chy thm 1 gi na, sau
cho my nghi mt lc sau ht li ln na. C lm nh vy khong 3 n 4 ln l .
Trong qu trnh ht chn khng ta kt hp sn dng ng st (sn ng ng bng sn mu
).
5.4.4. Np gas cho h thng.
Np gas vo h thng ta thc hin theo s :
Sau khi chn khng h thng, ni bnh vi nhnh van ht ng van s 7 v m
van s 8 ra sau ta m van chai gas ra gas vo h thng thng qua chnh lch
p sut. Sau cho my chy v iu chnh p sut ht khng vt qu 1.5 n 2 bar.
Cho my chy my nn ht ht phn gas trong chai gas. Np gas cho n khi p
sut ht khong 1 bar l . Khi xong ng van s 8 ri ng van chai gas. Sau
tho b np gas ra v cho my tip tc chy kim tra xem co cn s c no na
khng. Nu khng c s c no th ta kt thc qu trnh lp t h thng ti y.
5.5. Vn hnh h thng lnh5.5.1. Cng tc chun b.
Cng tc chun b gm cc bc sau:
Kim tra in p ngun khng c sai lch so vi nh mc 5%.
Kim tra bn ngoi my nn v cc thit b chuyn nh xem c vt g gy tr ngi
s lm vic ca my khng.
Kim tra s lng v cht lng du trong my nn. Mc du thng phi chim 2/3
mt knh xem mc.
Kim tra cc thit b o lng, iu khin v bo v h thng.
Kim tra h thng in trong t, m bo trong tnh trng hot ng tt.
Kim tra tnh trng ng m ca cc van.
5.5.2. Vn hnh h thng.
Sau khi kim tra xong ta tin hnh vn hnh cho h thng hot ng. y h
thng ny hot ng theo ch t ng. Ch ny hot ng hon ton t ng, cc bc vn
hnh nh sau:
Bt aptomat tng ca t in ng lc, aptomat cho tt c cc thit b ca h
thng cn chy.
Bt cng tc SW1 sang v tr ON. Khi qut dn ngng v qut dn lnh s chy
mt thi gian sau th my nn chy.
Theo di dng in my nn. Dng in khng c qu ln so vi quy nh. Nu dng
in ln qu th ta ng van chn ht li.
T t m van chn ht ra cho n khi dng in khng tng qu mc th thi.
Bt cng tc SWs sang v tr ON cp dch cho dn lnh.
Kim tra cc thng s p sut trng h thng.
- p sut ngng t < 16 kg/cm2. - p sut du kg/cm2. - p sut ht
< 1,5 kg/cm2.
Ghi li ton b cc thng s hot ng ca h thng bao gm: in p ngun, dng
in cc thit b, nhit v p sut du, nhit v p sut ht, nhit v p sut nn,
nhit bung lnh, bay hi.
5.5.3. Dng my.
Dng my c 3 trng hp l dng my s c v dng my bnh thng.
a) Dng my bnh thng:
Nhn cng tc SW2 v v tr OFF cho gas chy v ht bnh cha cao p.
Khi p sut ht xung thp qu mc lm cho rle p sut ht mt in v my nn
ngng hot ng.
ng van chn ht li.
Nhn cng tc SW1 sang v tr OFF ngng qut dn ngng v qut dn lnh.
ng cc ptomt ca cc thit b li.
b) Dng my s c.
Khi c s c khn cp cn tin hnh ngay lp tc:
Nhn cc cng tc SW1 v SW2 v v tr OFF dng my.
Tt cc aptomat tng ca t in li.
ng van chn ht li.
Tm nguyn nhn x l.
c) Dng my lu di.
Dng my lu di cn tin hnh ht nhiu ln ht kit mi cht trong dn lnh v
a v bnh cha cao p.
Sau khi tin hnh dng my, tt aptomat ngun v kho t in.
5.6. Bo dng h thng.5.6.1.Bo dng my nn.
Vic bo dng my nn l cc k quan trng cho h thng hot ng c tt, bn v
hiu qu lm vic cao nht.
My lnh d xy ra s c trong ba thi k: Thi k ban khi mi chy th v thi
k xy ra cc hao mn cc chi tit my.
C sau 6000 gi th phi i tu my mt ln. D my t chy th cng phi 1 nm i
tu my mt ln.
Cc my dng lu ngy trc khi chy phi tin hnh kim tra
Cng tc i tu gm:
Kim tra kn v tnh trng cc van x, van ht ca my nn.
Kim tra bn trong my nn, tnh trng du, chi tit my c b hoen g, lau
chi cc chi tit. Trong thi k i tu phi tho cc chi tit, lau chi v thay
du m.
Kim tra du bn trong ccte qua ca quan st du. Nu thy bt kim loi mu
vng, cn bn th phi kim tra nguyn nhn.
Kim tra mc mi mn ca cc thit b nh trc khuu, cc m kn, vng bc,
pittong, vng gng so vi cc kch thc tiu chun. Khi mn qu mc cho php th
phi thay th ci mi.
Th tc ng ca cc thit b iu khin HP, OP,WP, LP v b phn cp du.
Lau chi v sinh b lc ht my nn.
V sinh trong ng c.
Cng tc bo dng nh k: theo quy nh c 72 n 100 gi lm vic u tin phi
tin hnh thay du my nn. Trong 5 ln u tin phi thay du hon ton.
5.6.2.Bo dng thit b ngng t.
Bo dng thit b ngng t gm cc bc sau:
V sinh b mt trao i nhit.
X du tch t bn trong thit b.
Bo dng cn chnh qut gii nhit.
Sn sa bn ngoi.
Sa cha thay th thit b in, cc thit b an ton v iu khin lin
quan.
5.6.3. Bo dng thit b bay hi.
X bng dn lnh: Khi bng bm trn dn lnh nhiu s lm tng nhit tr ca dn
lnh, dng khng kh qua dn b tc, gim lu lng gi, trong mt s trng hp tc
qut v mt qut khng th quay lm chy ng c. V vy phi thng xuyn x
bng.
Bo dng dn lnh:
V sinh dn trao i nhit, mun vy cn ngng h thng hon ton, kh dn lnh
v dng chi qut sch. Nu khng c cn phi ra bng nc.
V sinh mng thot nc dn lnh.
TI LIU THAM KHO
[1]. inh Vn Thun - V Ch Chnh. H thng my v thit b lnh Nh xut bn
khoa hc k thut 2005.
[2].Hong nh Tn, Bi Hi. Bi tp K thut nhit. Nh xut bn i hc Bch
khoa Thnh ph H Ch Minh, nm 1993
[3]. Nguyn c Li, Phm Vn Ty. K thut lnh c s. Nh xut bn Gio Dc, nm
2002.[4]Nguyn c Li. Mi cht lnh. Nh xut bn Gio Dc, nm 1998. [5].
Nguyn c Li, Phm Vn Ty. Bi tp K thut lnh. Nh xut bn Gio Dc, nm
1998
[6] Nguyn c Li. Hng dn thit k h thng lnh. Nh xut bn Khoa hc v K
thut, nm 2002.
[7].Nguyn c Li. T ng ha h thng lnh. Nh xut bn Gio Dc, nm
2001.
[8] My v thit b lnh [9] Vt liu k thut nhit
[10] Mi cht lnh [11] Ti liu tham kho thm
1: Kho cam
2: L dng lc gic iu khin khoa cam.
3: Cht panel th hai gi kho cam
4: Cht panel th nht gi khoa cam khng b bt ngc lai sau.
4
3
2
1
Hnh 5-1: Cch kho tm panel
1: Panel tng th nht.
2: Panel tng th hai.
3: C cu kho cam.
4: Nt che l kho cam.
4
2
3
1
Hnh 5-2: Cch lp panel vch.
1: Tm panel vch 1.
2: Tm panel vch 2.
3: Thanh nhm hnh ch V.
4: Tn rive.
1
4
3
2
Hnh 5-3: Lp panel vch gc kho lnh.
5
4
3
2
1
Hnh 5-4: Ca kho lnh
1: Ca kho lnh.
2: Tm inox gi ca vi panel
3: Kho ca.
4: Cht kho.
5: Bn l.
1: Panel nn.
2: Panel vch.
3: Tn rive.
4: Thanh nhm ch V.
4
3
2
1
Hnh 5-5: Lp panel nn v vch
1: Panel vch .
2: Panel nn.
3: Tn rive.
4: Thanh nhm ch V.
4
3
2
1
Hnh 5-6: Lp panel vch v nn
Hnh 5-7: Cch `lp x treo
1: X treo.
2: Tng .
3: Dy cp.
4: X g trn mi kho.
1
2
3
4
1: Panel vch pha Ty Bc.
2: Panel trn kho lnh.
3: Bulong d.
4: ai c gi bulong d.
5: Dy cp theo panel trn.
6: C cu tng.
7: Thanh thp ch U.
8: Tn rive.
9: Thanh nhm ch V.
10: X g.
10
9
8
7
6
5
4
3
2
1
Hnh 5-8: Lp panel trn pha Ty Bc
8
7
6
5
3
4
2
1
Hnh 5-9: Lp panel trn hng th hai
1: Panel trn hng th nht.
2: Panel trn hng th hai.
3: Thanh nhm lp khe h gia hai panel.
4: Bulong d.
5: Thanh thp ch U.
6: C cu tng.
7: Dy cp.
8: X g.
1: Tm panel hng th hai.
2: Tm panel hng th ba.
3: Tm panel kho lnh th hai.
4: Panel vch .
5: Bulong d.
6: Thanh nhm ch V.
7: Tn rive.
8: Thanh thp ch U.
9: C cu tng.
10: Dy cp treo.
11: X g.
4
3
7
6
5
8
9
10
11
2
1
Hnh 5-10: Lp panel trn hng th ba.
Hnh chiu cnh
Hnh chiu ng
Hnh 5- 11: Cch lp cm dn ngng, my nn
4
2
1
sn b tng
7
5
3
6
1: Qut dn ngng.
2: Dn ngng.
3: My nn.
4: Bnh cha cao p.
5: ng gas v dn lnh.
6: Khung .
7: ng gas t dn lnh v.
Hnh 5- 12: Cch treo dn lnh.
11
10
8
7
6
5
4
3
2
1
1: Dn lnh.8: Dy cp mc tng.
2: Qut dn lnh.9: Tng.
3: Thanh thp ch U trn dn lnh.10: X g trn mi.
4: Thanh ty.11: Dy cp.
5: ai c.
6: Panel trn.
7: Thanh thp ch U phn b lc u trn panel.
5
4
3
2
1
Hnh 5-13: Lp t bnh tch lng
1: Bnh tch lng
2: B gim ng.
3: Mi hn in.
4: ng st.
5: Co ng st.
Hnh 5-14: V tr lp t van tit lu
1: Dn lnh.
2: ng cn bng ngoi.
3: ng t bnh cha cao p n.
4: ung v my nn.
5: Bu cm bin.
6: Van tit lu
6
5
4
3
2
1
Hnh 5-15: Cu to ng ng sau khi bc cch nhit
1: Vt liu cch nhit PU.
2: V tn bc bn ngoi.
3: ng ng.
4: ng st.
4
3
1
2
7
6
5
4
3
2
1
Hnh 5-16: Cng tc ui bi ng ng st
1: Dn lnh.
2: ng ng sau van tit lu.
3: ng st.
4: Dy np gas.
5: Chai Nit.
6: Bnh tch lng.
7: Mt bch ca van ht.
8
7
5
6
E
D
C
B
HP
LP
4
3
A
1
2
Hnh 5-17: S qu trnh ht chn khng
1: ng nn ca my nn.
2: ng ht v ca my nn.
3: Van ht.
4: My nn.
5: My ht chn khng.
6: ng khng kh c ht ra.
7: Van cao p ca ng h np gas.
8: Van thp p ca ng h np gas.
Hnh 5-18: Cc thit b trong qu trnh ht chn khng: Dy gas, ng h np
gas, my ht chn khng.
E
8
7
4
3
D
C
B
A
1
2
HP
LP
5
Hnh 5-19: Cch np gas h thng.
1:ng nn ca my nn.
2: ng ht v ca my nn.
3: Van ht.
4: My nn.
5: chai gas.
7: Van cao p ca ng h np gas.
8: Van thp p ca ng h np gas.
A,B,C,D,E: Cc gicco kt ni.
EMBED AutoCAD.Drawing.16
EMBED AutoCAD.Drawing.16
tql
tqn
i(kJ/kg)
Hnh 4-1: Biu din cc thng s trn th lgPi
4
P0, T0
3'
3
Pk, Tk
1
1'
2
Dn ngng
tql
tqn
Bieu dien tren o th P-i
4
Po,To
3'
3
Pk,Tk
1
1'
2
P(bar)
Van tit
lu
Hnh 4-3: Cm my nn dn ngng
Cng sut ng c my nn i km 15HP
S qut gi
ng knh qut EMBED Equation.3
Hnh 4-4: Dn bay hi
12
11
10
9
8
7
6
3
4
5
2
1
P
1
= f(t
qn
)
P
h
R
Hnh 4-5: Cu to van tit lu
1: Np chp
2: Vt iu chnh.
3: Mi cht lnh vo thit b bay hi.
4: L xo.
5: Ty van.
6: Ni vi ng cn bng
p sut ngoi.
7: Mng xp.
8: Bu cm bin.
9: ng mao.
10: Ty van.
11: Dch vo.
12: Phin lc.
Hnh 4-6: S lp t van tit lu
Hnh 4-7: phin lc cho thit b my lnh freon.
Hnh 4-8: Cu to van in t.
1: Thn van.7: V.
2: van.8: Cun dy din t
3: Clppe.9: Vt c nh
4: ng dn hng ng thi l ng ngn cch10: Vng on mch chng n.
khoang mi cht vi bn ngoi.11: Dy tip in.
5: Li st.12: M c ni vt.
6: Li c nh.13: L xo.
.
Hnh 4-2: Chu trnh my lnh
Hnh 3-3:Kt cu cch nhit trn kho lnh
Hnh 3-2: Cc thng s
Hnh 3-1:S biu din kt cu tng bao
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