do an kho lanh ca r22
TRANSCRIPT
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
CHNG M U
I. NGHA CA LNH
T xa xa , loi ngi bit s dng lnh phc v cho i sng , bng cch chovt cn lm lnh tip xc vi nhng vt lnh hn nh dng bng tuyt bo qun snphm m h sn bt c l phng php lm lnh t nhin. Nhng mun lm lnh nhit ty v gi nhit trong mt thi gian ty th cn dng h thng lm lnhnhn to.Cho n nay k thut lnh ngy cng pht trin mnh m v c ng dng rngri trong 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 cc sn phm thuc- Trong cng nghip ho cht : iu khin cc phn ng ha hc
- Trong lnh vc iu ho khng kh cho sn xut v i sng.
II. MC CH CP, TR NG
c th gi cho thc phm c lu di nhm cung cp, phn phi cho nn kinh tquc dn,th phi cp ng v tr ng nhm gi cho thc phm mt nhit thp (-180C - 40 0 C). Bi v nhit cng thp th 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 phmkhng b hng trong thi gian di.
III.NHIM V CA NThit k h thng cp ng , tr ng sn phm tht Heo vi cc thng s nhsau:
1. Cp ng :- Mi cht : R22- Sn phm bo qun : Tht Heo- Cng sut : E = 2,5 tn/m
- Nhit tht u vo :vao
spt = 180C
- Nhit tht u ra : ttb = -15 0C
- Thi gian cp ng : = 11 h- Nhit phng cp ng :
cdf
t = -35 0C
2. Tr ng :- Cng sut : E = 35 tn
- Nhit phng tr ng :tdf
t = -18 0C
3. a im lp t h thng lnh :
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
Thnh ph Hu, t bng 1-1, trang 8, ti liu [1],ta c cc thng s v nhit v m nh sau :
Nhit , 0C m, %
TB c nm Ma h Ma ng Ma h Ma ng25,2 37,3 13,1 73 90
4.Quy trnh cng ngh :
Tht Heo sau khi qua phn xng ch bin c a vo phng cp ng c
nhit l :cdf
t = - 35 0C. Sau qua ng gi ri a vo phng tr ng c nhit
l :tdf
t = -18 0C.
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
CHNG 1 : XC NH KCH THC V B TR MTBNG KHO LNH
Chng ny nhm mc ch l xc nh kch thc phng kho lnh m bo cngsut lnh yu cu v b tr hp l mt bng kho lnh.
1.1 TNH KCH THC PHNG CP NGCho bit: - Cng sut : E = 2,5 tn/m
- Sn phm: Tht Heo1. Tnh th tch cht ti: Vct
Theo cng thc (2-1)trang 29, ti liu [1] :
Vct=vg
E, [m3]
Vi: - E : l cng sut cht ti phng cp ng , [tn]- gv: l nh mc cht ti th tch ,[t/m3]
Theo trang 29 , ti liu [1] th mi m2 c th sp xp c 0,6 n 0,7t (tngng 0,7t/m3) do ta c : gv = 0,17 [t/m3].
Suy ra: Vct=17,0
5,2= 14,7 m3
2. Tnh din tch cht ti : FctTheo cng thc (2-2)trang 29, ti liu [1] :
Fct=ct
ct
h
V , [m2]
Vi: hct: l chiu cao cht ti, [m] chn hct= 2m
Suy ra: Fct= 27,14 = 7,35 m2
3. Din tch trong ca phng lnh: Ftr Theo cng thc (2-4)trang 30, ti liu [1] :
Ftr=F
Fct
, [m2]
Vi : F: l h s k n ng i li,din tch chim ch ca dn bay hi,qut. dy ta chn F = 0,54 theo bng 2-4, ti liu[1]
Suy ra: Ftr= 54,035,7
= 13,6 m2
4. Chiu cao trong ca phng cp nghtr= hct+ h , [m]
Vi: h l chiu cao k n gi i i lu trong bung, chn h = 1mSuy ra: htr=2+1= 3 m
5. Xc nh s phng cp ng: ZTheo cng thc (2-5)trang 30, ti liu [1] :
Z =f
Ftr ,
Vi: f l din tch bung lnh quy chun. chn f= 4x4 m2
Suy ra: Z = 166,13 = 0,85
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
chn Z=1 phng => C bung cp ng s l: Ftr= f = 4x4 m2
1.2 TNH KCH THC PHNG TR NG.Cho bit: - Cng sut: E = 35 tn
1. Tnh th tch cht ti: VctTheo cng thc (2-1)trang 29, ti liu [1] :
Vct =vg
E, [m3]
Vi: - E: Cng sut cht ti phng cp ng , [tn]- gv= 0,45 [t/m3] : nh mc cht ti th tch, tra theo bng 2-3 ti liu [1] i
vi tht heo ng lnh
Suy ra: Vct =35
0,45= 77,77 m3
2. Tnh din tch cht ti : Fct
Theo cng thc (2-2)trang 29, ti liu [1] :Fct =
ct
ct
h
V, [m2]
Vi: hct [m]: chiu cao cht ti, chn hct= 2m
Suy ra: Fct=77,77
2= 38,88 m2
3. Din tch trong ca phng lnh: FtrTheo cng thc (2-4)trang 30, ti liu [1] :
Ftr=F
Fct
, [m2]
Vi : F: l h s k n ng i li, din tch chim ch ca dn bay hi, qut. dy ta chn theo bng 2-4 ti liu[1] vi din tch bung lnh t 20100 m2 c F=0,7
Suy ra: Ftr=38,88
0,7= 55,54 m2
4. Chiu cao trong ca phng cp nghtr= hct+ h , [m]
Vi: h l chiu cao k n gi i i lu trong bung. chn h = 1mSuy ra: htr= 2+1 = 3 m
5. Xc nh s phng cp ng: Z
Theo cng thc (2-5)trang 30, ti liu [1] :Z=
f
Ftr ,
Vi: f l din tch bung lnh quy chun. chn f = 6x6 m2
Suy ra: Z =55,54
36= 1,54
chn Z = 2 phng => C bung cp ng s l: Ftr= f = 6x6 m2
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
1.3 . B TR MT BNG KHO LNH
PX.
CHB
IN
TT
HANH LANG
C
WCP. TRCGIAN MAY
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
CHNG 2: TNH CCH NHIT CHO KHO LNH
Mc ch chng ny : nhm xc nh chiu dy lp cch nhit ca kt cu kho lnhtha mn iu kin ti u v kinh t v k thut (tha mn ti u lng lnh tit kim c
vi vn u t ) v m bo trnh hin tng ng sng .Chiu dy lp cch nhit tnh theo cng thc tnh h s truyn nhit k qua vch phng
nhiu lp ly t cng thc (3-1) trang 64, ti liu [1]
k =211
111
+++
= cn
cnn
n i
i , [W/m2K]
Suy ra chiu dy lp cch nhit:
cn=cn
++
= 211
111
n
i i
i
k, [m]
Vi: - cn: dy yu cu ca lp cch nhit, [m]- cn: H s dn nhit ca vt liu cch nhit , [W/mK]- k : H s truyn nhit, [W/m
- 1: h s to nhit ca mi trng bn ngoi ti tng cch nhit, [W/m2K]- 2: h s to nhit ca vch bung lnh ti bung lnh, [W/m2K]- i: B dy yu cu ca lp vt liu th i, [m]- i: H s dn nhit ca lp vt liu th i, [W/mK]
2.1 TNH CCH NHIT CHO TNG BAO KHO LNH
Chng ta s tnh cch nhit chung cho cc tng v tnh cho cc tng khc nghit.Chiu dy lp cch nhit c xc nh theo 2 yu cu c bn:
- Vch ngoi kt cu bao che khng c php ng sng, ngha l dy ca lpcch nhit phi ln nhit b mt vch ngoi ngoi ln hn nhit ng sngca mi trng ts.
- Chn chiu dy cch nhit sao cho gi thnh mt n v lnh l r nht.
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
1. Kt cu v cc s liu ca n
8 96 73 4 521
tftn
Lp Vt liu [m] [W/m2K]1 Va trt xi mng 0,015 0,92 Lp Gch 0,200 0,823 Va trt xi mng 0,005 0,94 Bitum 0,002 0,185 Giy du 0,005 0,156 Xp 0,047
7 Giy du 0,002 0,158 Li mt co,va mc
cao0,020 0,9
9 Mc st 4
2.Tnh tona. Phng tr ng
- H s to nhit b mt ngoi ca tng bao tra theo bng 3-7, trang 65, ti liu [1] c1 = 23,3 W/m2K
- H s to nhit b mt trong ca bung lnh lu thng khng kh cng bc va phitra theo bng 3-7 trang 65, ti liu [1] c: 2=9 W/m2K
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
- i vi phng tr ng th nhit tron g phng l -18 0C. Tra bng 3-3 trang 63 tiliu [1] vi nhit phng -18 0C tnh cho vch bao ngoi. Ta c h s truyn nhit ti uqua tng : kt = 0,22 W/m2K
Th s vo ta tnh c chiu dy lp cch nhit tng phng tr ng:
cn = 0,047[1 1 0,015 0,2 0,005 0,002 0,005 0,002 0,02 1
( )]0,22 23,3 0,9 0,82 0,9 0,18 0,15 0,15 0,9 9 + + + + + + + += 0,19 mTrn thc t th chiu dy ca cc tm cch nhit u c quy chun. Do chiu
dy thc t ca lp cch nhit cng c chn theo quy chun vi iu kin n phi lnhn hoc bng chiu dy xc nh c . y chn chiu dy thc t ca tm cchnhit l: ttcn = 0,2 m
ng vi ttcn ta s tnh c h s truyn nhit thc t:
ktd =1
1 0,015 0,2 0,005 0,002 0,005 0,2 0,002 0,02 1
23,3 0,9 0,82 0,9 0,18 0,15 0,047 0,15 0,9 9+ + + + + + + + += 0,2 W/m2K
b.Phng cp ng- H s to nhit b mt ngoi ca tng bao tra theo bng 3-7 trang 65 ti liu [1] c :
1= 23,3 W/m2K- H s to nhit b mt trong ca bung lnh lu thng khng kh cng bc mnh tra
theo bng 3-7 trang 65,ti liu[1] c: 2= 10,5 W/m2K- i vi phng cp ng th nhit trong phng l -35 0C. Tra bng 3-3 trang 63 ti
liu [1] vi nhit phng -35 0C tnh cho vch bao ngoi. Ta c h s truyn nhit ti uqua tng : kt = 0,19 W/m2K
Th s vo ta tnh c chiu dy lp cch nhit tng phng cp ng:
cn = 0,047[1 1 0,015 0,2 0,005 0,002 0,005 0,002 0,02 1
( )]0,19 23,3 0,9 0,82 0,9 0,18 0,15 0,15 0,9 10,5
+ + + + + + + +
= 0,22 mTrn thc t th chiu dy ca cc tm cch nhit u c quy chun. Do chiu
dy thc t ca lp cch nhit cng c chn theo quy chun vi iu kin n phi lnhn hoc bng chiu dy xc nh c . y chn chiu dy thc t ca tm cchnhit l: ttcn = 0,3 m
ng vi ttcn ta s tnh c h s truyn nhit thc t:
kcd =
1
1 0,015 0,2 0,005 0,002 0,005 0,3 0,002 0,02 123,3 0,9 0,82 0,9 0,18 0,15 0,047 0,15 0,9 10,5
+ + + + + + + + + = 0,145
W/m2K3. Kim tra nhit ng sng
Nu b mt ngoi ca tng bao ng sng th m s d xm nhp vo ph hu lpcch nhit. trnh hin tng ng sng xy ra th nhit b mt ngoi tng bao
phi ln hn nhit ng sng ca mi trng. iu kin khng xy ra hin tngng sng c xc nh theo cng thc (3-7) trang 66,ti liu[1].
k ks = 0,95.1 fnsn
tt tt , [W/m2K]
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
Vi: - k : h s truyn nhit thc t qua tng, [W/m2K]- ks :h s truyn nhit thc t qua tng khi b mt ngoi l nhit ng
sng, [W/m2K]- 1=23,3 W/m2K h s to nhit b mt ngoi ca tng bao che- tf : nhit trong bung lnh, 0C- tn= 37,30C : nhit mi trng ngoi- ts = 320C nhit ng sng ca mi trng, tra theo th I-d vi nhit
mi trng t1=37,30C v m =73% a. Phng tr ng
Phng tr ng c tf= -180C
Suy ra: ks= 0,95.23,3.37,3 32
37,3 ( 18)
= 2,13 W/m
2K
M c kt = 0,2 < ks = 2,13 W/m2KVy khng c hin tng ng sng trn b mt ngoi ca tng bao phng tr ng
b. Phng cp ngPhng cp ng c tf= -350C
Suy ra: ks= 0,95.23,3.37,3 32
37,3 ( 35)
= 1,6 W/m
2K
M c kc= 0,145< ks = 1,6 W/m2KVy khng c hin tng ng sng trn b mt ngoi ca tng bao phng cp ng.
2.2 TNH CCH NHIT TRN KHO LNH
1. Kt cu v cc thng s ca n
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
2
7
9
8
4
6
5
3
1
tf
tn
Lp Vt liu [m] [W/m2K]1 Va trt xi mng 0,015 0,92 B tng ct thp 0,100 1,53 Va trt xi mng 0,005 0,94 Bitum 0,002 0,185 Giy du 0,005 0,15
6 Xp 0,0477 Giy du 0,002 0,158 Li mt co,va mc
cao0,020 0,9
9 Mc st 4
2. Tnh tona Phng tr ng
- H s to nhit b mt ngoi ca tng bao tra theo bng 3-7 trang 65,ti liu[1] c :1= 23,3 W/m2K
- H s to nhit b mt trong ca bung lnh lu thng khng kh cng bc va phi tratheo bng 3-7 trang 65,ti liu[1] c: 2= 9 W/m2K
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
- i vi phng tr ng th nhit trong phng l -18 0C. Tra bng 3-3 trang 63 tiliu[1] vi nhit phng -18 0C tnh cho mi bng. Ta c h s truyn nhit ti u quatng : kt = 0,218 W/m2K
Th s vo ta tnh c chiu dy lp cch nhit tng phng tr ng:
cn = 0,047[1 1 0,015 0,1 0,005 0,002 0,005 0,002 0,02 1
( )]0,218 23,3 0,9 1,5 0,9 0,18 0,15 0,15 0,9 9 + + + + + + + += 0,199 mTrn thc t th chiu dy ca cc tm cch nhit u c quy chun. Do chiu
dy thc t ca lp cch nhit cng c chn theo quy chun vi iu kin n phi lnhn hoc bng chiu dy xc nh c . y chn chiu dy thc t ca tm cchnhit l: ttcn = 0,2 m
ng vi ttcn ta s tnh c h s truyn nhit thc t:
ktd =1
1 0,015 0,1 0,005 0,002 0,005 0,2 0,002 0,02 1
23,3 0,9 1,5 0,9 0,18 0,15 0,047 0,15 0,9 9+ + + + + + + + += 0,218 W/m2Kb. Phng cp ng
- H s to nhit b mt ngoi ca tng bao tra theo bng 3-7 trang 65,ti liu[1] c :1= 23,3 W/m2K- H s to nhit b mt trong ca bung lnh lu thng khng kh cng bc mnh tratheo bng 3-7 trang 65,ti liu[1] c: 2= 10,5 W/m2K- i vi phng tr ng th nhit trong phng l -35 0C. Tra bng 3-3 trang 63 tiliu[1] vi nhit phng -35 0C tnh cho mi bng.Ta c h s truyn nhit ti u quatng : kt = 0,17 W/m2K
Th s vo ta tnh c chiu dy lp cch nhit tng phng cp ng:
cn = 0,047[1 1 0,015 0,1 0,005 0,002 0,005 0,002 0,02 1
( )]0,17 23,3 0,9 1,5 0,9 0,18 0,15 0,15 0,9 10,5
+ + + + + + + +
= 0,26 mTrn thc t th chiu dy ca cc tm cch nhit u c quy chun. Do chiu
dy thc t ca lp cch nhit cng c chn theo quy chun vi iu kin n phi lnhn hoc bng chiu dy xc nh c . y chn chiu dy thc t ca tm cchnhit l: ttcn = 0,3 m
ng vi ttcn ta s tnh c h s truyn nhit thc t:
kcd =1
1 0,015 0,1 0,005 0,002 0,005 0,3 0,002 0,02 123,3 0,9 1,5 0,9 0,18 0,15 0,047 0,15 0,9 10,5
+ + + + + + + + +
= 0,15W/m2K3. Kim tra nhit ng sng
Nu b mt ngoi ca tng bao ng sng th m s d xm nhp vo ph hu lp cchnhit. trnh hin tng ng sng xy ra th nhit b mt ngoi tng bao phi lnhn nhit ng sng ca mi trng. iu kin khng xy ra hin tng ng
sng c xc nh theo cng thc (3-7) trang 66 ti liu [1].
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A A
11
9
8
76
54
3
2
1
n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
k ks = 0,95.1 fnsn
tt
tt
, [W/m2K]Vi: - k : h s truyn nhit thc t qua tng, [W/m2K]
- ks :h s truyn nhit thc t qua tng khi b mt ngoi l nhit ng
sng, [W/m2K]- 1= 23,3 W/m2K h s to nhit b mt ngoi ca tng bao che- tf : nhit trong bung lnh, 0C- tn= 37,30C : nhit mi trng ngoi- ts = 320C nhit ng sng ca mi trng, tra theo th I-d vi nhit
mi trng t1=37,30C v m =73% a. Phng tr ng
Phng tr ng c tf= -180C
Suy ra: ks = 0,95.23,3.37,3 32
37,3 ( 18)
= 2,13 W/m
2K
M c kt = 0,218 < ks = 2,13 W/m2KVy khng c hin tng ng sng trn b mt ngoi ca tng bao phng tr ng
b. Phng cp ngPhng cp ng c tf= -350C
Suy ra: ks= 0,95.23,3.37,3 32
37,3 ( 35)
= 1,6 W/m
2K
M c kc= 0,15< ks = 1,6 W/m2KVy khng c hin tng ng sng trn b mt ngoi ca tng bao phng cp ng.
2.3 TNH CCH NHIT NN KHO LNH1. Kt cu v cc s liu ca n
Lp Vt liu [m] [W/m2
K]1 t nn
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
2 B tng si 0,100 1,23 Va trt xi mng 0,005 0,94 Bitum 0,002 0,185 Giy du 0,005 0,15
6 Xp 0,0477 Giy du 0,002 0,158 B tng ct thp 0,100 1,59 Va trt 0,005 0,910 G b tong11 ng PVC 100
2. Tnh toni vi nn c si th ta ch cn tnh cc lp pha trn lp c si. C th y trong
lp b tng si thng ngui ta thi cng vi chiu dy 300 mm.
Gn ng xem trao i nhit vi khng kh di nn vi mt lp b tng dy 100mma. Phng tr ng - H s to nhit b mt ngoi ca tng bao tra theo bng 3-7 trang 65,ti liu[1] c :1= 6 W/m2K - H s to nhit b mt trong ca bung lnh lu thng khng kh cng bc va phitra theo bng 3-7 trang 65 ti liu [1] c: 2=9 W/m2K
- i vi phng tr ng th nhit trong phng l -18 0C. Tra bng 3-6 trang 63 tiliu [1] vi nhit phng -18 0C tnh cho nn c si. Ta c h s truyn nhit ti u quann c si: kt = 0,226 W/m2K
Th s vo ta tnh c chiu dy lp cch nhit tng phng tr ng:
cn = 0,047[ 1 1 0,1 0,005 0,002 0,005 0,002 0,1 0,005 1( )]0,226 6 1,2 0,9 0,18 0,15 0,15 1,5 0,9 9 + + + + + + + +
= 0,19 mTrn thc t th chiu dy ca cc tm cch nhit u c quy chun. Do chiu
dy thc t ca lp cch nhit cng c chn theo quy chun vi iu kin n phi lnhn hoc bng chiu dy xc nh c . y chn chiu dy thc t ca tm cchnhit l: ttcn = 0,2 m
ng vi ttcn ta s tnh c h s truyn nhit thc t:
ktd =
1
1 0,1 0,005 0,002 0,005 0, 2 0,002 0,1 0,005 16 1,2 0,9 0,18 0,15 0,047 0,15 1,5 0,9 9+ + + + + + + + + = 0,217 W/m2
K
b. Phng cp ng - H s to nhit b mt ngoi ca tng bao tra theo bng 3-7 trang 65,ti liu[1] c :1= 6 W/m2K
- H s to nhit b mt trong ca bung lnh lu thng khng kh cng bc mnh tratheo bng 3-7 trang 65 ti liu [1] c: 2= 10,5 W/m2K
- i vi phng cp ng th nhit trong phng l -35 0C. Tra bng 3-6 trang 64 tiliu [1] vi nhit phng -35 0C tnh cho mi bng. Ta c h s truyn nhit ti u quatng : kt = 0,17 W/m2K
Th s vo ta tnh c chiu dy lp cch nhit tng phng cp ng:
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
cn = 0,047[1 1 0,1 0,005 0,002 0,005 0,002 0,1 0,005 1
( )]0,17 6 1,2 0,9 0,18 0,15 0,15 1,5 0,9 10,5
+ + + + + + + +
= 0,26 mTrn thc t th chiu dy ca cc tm cch nhit u c quy chun. Do chiu
dy thc t ca lp cch nhit cng c chn theo quy chun vi iu kin n phi lnhn hoc bng chiu dy xc nh c . y chn chiu dy thc t ca tm cchnhit l: ttcn = 0,3 m
ng vi ttcn ta s tnh c h s truyn nhit thc t:
kcd =1
1 0,1 0,005 0,002 0,005 0,002 0,1 0,005 0.3 16 1,2 0,9 0,18 0,15 0,15 1,5 0,9 0.047 10,5
+ + + + + + + + + = 0,15W/m2K
3. Kim tra nhit ng sng Nu b mt ngoi ca tng bao ng sng th m s d xm nhp vo ph hu lpcch nhit. trnh hin tng ng sng xy ra th nhit b mt ngoi tng bao
phi ln hn nhit ng sng ca mi trng. iu kin khng xy ra hin tngng sng c xc nh theo cng thc (3-7) trang 66 ti liu [1].
k ks = 0,95.1 fnsn
tt
tt
, [W/m2K]Vi: - k : h s truyn nhit thc t qua tng, [W/m2K]
- ks :h s truyn nhit thc t qua tng khi b mt ngoi l nhit ngsng, [W/m2K]
- 1= 6 W/m2K h s to nhit b mt ngoi ca tng bao che
- tf : nhit trong bung lnh, 0C- tn= 37,30C : nhit mi trng ngoi- ts = 320C nhit ng sng ca mi trng, tra theo th I-d vi nhit
mi trng t1=37,30C v m =73% a. Phng tr ng
Phng tr ng c tf= -180C
Suy ra: ks = 0,95.6.37,3 32
37,3 ( 18)
= 0,54 W/m
2K
M c kt = 0,217 < ks = 0,54 W/m2KVy khng c hin tng ng sng trn b mt ngoi ca tng bao phng tr ng
b. Phng cp ngPhng cp ng c tf= -350C
Suy ra: ks = 0,95.6.37,3 32
37,3 ( 35)
= 0,42 W/m
2K
M c kc = 0,15 < ks = 0,42 W/m2KVy khng c hin tng ng sng trn b mt ngoi ca tng bao phng cp ng.
2.4 B TR CCH NHIT KHO LNH
i vi tng ngn gia 2 phng lnh c nhit m nh nhau vn phi cch nhit vi
chiu dy nh tng bao ngoi v phng trng hp ch c mt phng lm vic.
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
thun tin cho vic thi cng th chiu dy lp cch nhit tng bao ngoi c dngchung cho cc tng cn li .
CHNG 3 : TNH NHIT H THNG LNH
- Chng ny nhm tnh tng tn tht nhit ca kho lnh . t tnh ra cng sutyu cu ca my lnh.
SVTH : Trn Thanh Sang _ Lp 07N2 Trang : 15
A
T
(-18C)
T
(-18C)
C
(-35C)
300
100
200
100
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
- Tn tht lnh t kho lnh ra mi trng c xc nh theo biu thc 4-1, trang 75 ,ti liu [1] :
Q = Q1 + Q2 + Q3 + Q4 + Q5 , [W]Trong : Q1: Tn tht lnh qua kt cu bao che, [W]
Q2: Tn tht lnh lm lnh sn phm v bao b, [W]Q3: Tn tht lnh do thng gi. Tn tht ny ch c i vi cc
phng lnh c pht sinh ngun hi thi hoc cc cht c hi. y sn phm bo qun ltht heo qua ch bin nn khng cn phi thng gi bung lnh => Q3=0
Q4: Tn tht lnh do vn hnh , [W]Q5: Tn tht lnh do sn phm th (Rau, hoa qu), y sn
phm l tht heo => Q5 = 0=> Tn tht lnh ca kho lnh thit k dc tnh theo cng thc:
Q = Q1 + Q2 + Q4 , [W]
- Cc s liu v cch b tr bung :
SVTH : Trn Thanh Sang _ Lp 07N2 Trang : 16
C
(-35C)T
(-18C)
T
(-18C)
A
D
C
E
F
G
H
K
B4500
4500
6000 6500
6500
6000
4000
2250
4000
6000 6000
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
=> chiu di nn v trn = 4m.Kt qu tnh ton c a vo bng tng hp sau:
Kt cu Kch thc,
[m x m]
Din tch F,
[m2]
ki
[W/m2K]
ti
[0C]
Qi
[W]Tng AB 4,5 x 3,6 16,2 0,145 72,3 169,83Tng AD 4,5 x 3,6 16,2 0,145 72,3 169,83Tng BC 4,0 x 3,6 14,4 0,47 43,38 293,59Tng CD 4,0 x 3,6 14,4 0,265 50,61 193,12
Nn 4,0 x 4,0 16 0,15 72,3 173,52Trn 4,0 x 4,0 16 0,15 72,3 173,52Tng Q1 = Qi 1173,41
2. Tnh tn tht lnh do lm lnh sn phm v bao b: Q2Ta c : Q2 = Q
sp
2 + Qbb
2 , [W]
Trong :
- Q sp2 : Tn tht lnh do lm lnh sn phm- Q bb2 : Tn tht lnh do lm lnh bao b
a.Tnh Qsp2 :Ta c cng thc tnh Q sp2 : theo trang 80, ti liu [1]
Qsp
2 =1 2
.
i i
E
, [kW]Vi : - E: Khi lng sn phm a vo cp ng 1 m, [t]
- i1: Entanpi ca tht Heo khi a vo nhit 180C, tra bng (4-2) trang81 ti liu [1] ,bng ni suy ta c : i1 = 266,2 kJ/kg
- i2: Entanpi ca tht Heo khi a ra nhit 150C, tra bng (4-2) trang81 ti liu [1] ta c : i2 = 12,2 kJ/kg
- =11h thi gian cp ng cho 1 m tht
=> Q sp2 = 3600.111000).2,122,266.(5,2
= 16,035 kW
b. Tnh Q bb2 :
Ta c cng thc tnh tn tht lnh do bao b:
Q bb2 =1 2
. .( )bb bb
G C t t
, [kW]
Vi: - Gb: Khi lng bao b a vo cng sn phm,[t]. Do khi lng bao bchim ti (10 30)% khi lng hng (trang 84 ti liu [1]) v bao b bng kim loi nnly bng 30% khi lng sn phm Gb=30%G.
- Cbb: Nhit dung ring ca bao b, i vi bao b bng kim loi th : Cbb =
0,45kJ/kg.K (trang 84 ti liu [1])
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
- t1: Nhit u vo ca bao b ly bng nhit u vo ca sn phm- t2: Nhit u ra ca bao b ly bng nhit ca phng cp ng- = 11h thi gian cp ng cho 1 m sn phm
=> Q bb2 =0,3.2,5.0,45.[18 ( 15)].1000
11.3600
= 0,281 kW
Vy tng tn tht lnh do lm lnh sn phm v bao b l:Q2= 16,035 + 0,281 = 16,316 kW
3.Tnh tn tht lnh do vn hnh: Q4Tn tht lnh do vn hnh Q4 bao gm cc tn tht lnh do n chiu sng , do
ngi lm vic trong phng,do cc ng c in v do m ca:
Q4= Q1
4 + Q2
4 + Q3
4 + Q4
4 , [W]
Vi: - Q14 : Tn tht lnh do n chiu sng bung lnh
- Q 24 : Tn tht lnh do ngi lm vic trong phng
- Q 34 : Tn tht lnh do cc ng c in- Q 44 : Tn tht lnh do m ca
a. Tn tht lnh do n chiu sng: Q14Q14 c tnh theo cng thc (4-17) trang 86 ti liu [1] ta c:
Q14 = A . F, [W]
Vi: - F: din tch phng lnh , [m2] F = 4x4=16 m2
- A: Nhit lng to ra khi chiu sng 1m2 din tch bung. i vi phng boqun lnh c A= 1,2 W/m2
=> Q14 = 1,2 .16 = 19,2 W
b. Dng nhit do ngi to ra Q 24 :
Q 24 dc tnh theo cng thc (4-18) trang 86 ti liu [1] ta c:
Q 24 = 350.n , [W]
Vi: - 350: nhit lng do 1 ngi to ra khi lm vic nng nhc- n l s ngi lm vic trong phng . V phng c din tch < 200 m2 =>
chn n = 2
Q 24 = 350.2 = 700 W
c. Tn tht lnh do cc ng c in Q 34 :Ta bit rng nng lng in cung cp cho ng c c chia lm 2 phn:
+ 1phn bin thnh nhit nng to ra mi trng xung quanh. Do nu ng c ttrong phng lnh th nhit to ra ny s gy ra 1 phn tn tht lnh.
+ Phn ln cn li bin thnh c nng c ch (nh lm quay qut thng gi, quay ng cqut dn bay hi). Nhng c nng ny ti mi trng s c xt vi khng kh trong mitrng bin thnh nhit nng gy ra tn tht lnh cho kho lnh.
Tn tht lnh do cc ng c in c tnh theo cng thc (4-19), trang 87, ti liu [1]:
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
Q 34 = .i N i , [kW]Vi: - :i Hiu sut ca ng c
+ i = 1: Nu ng c t trong phng
+ i = dc : Nu ng c t ngoi phng lnhi vi phng cp ng ngi ta nh mc cng sut ca ng c in cho phng ccng sut E=2 tn/m l : N = 4x2,2 kW
Ta c th tnh cng sut ng c in ca phng cp ng vi cng sut l 2,5tn/m l:
N dccd= 25,2.2,2.4
= 11kW
=> Tn tht lnh do ng c in
Q 34 = Ndc
cd= 11kW
d. Tnh dng nhit khi m ca:Q 44 Dng nhit khi m ca c tnh theo cng thc (4-20) trang 87 ti liu [1]
Q 44 = B.F , [W]
Vi: B- dng nhit ring khi m ca, [W/m2]. Tra bng (4-4) trang 87 i viphng cp ng c din tch F= 16 m2 < 50 m2 ta c: B = 32 m2
F= 4x4m2: din tch bung
=> Q 44 = 16.32 = 512 W
Vy tng tn tht lnh do vn hnh l:Q4 = 19,2 + 700 + 11000 + 512 = 12231,2W
4. Tnh nhit kho lnhi vi h thng lnh cp ng th tng tn tht nhit cp cho phng ny l:
Q0 = Q1 + Q2 + Q4 = 1173,4 +16316 + 12231,2 = 29720,6 W = 29,7206 kW5. Cng sut lnh yu cu ca my nn
Cng sut nhit yu cu ca my nn phi m bo b li tn tht nhit cp cho phngQ. Nhng v khi mi cht i t my nn n dn lnh th s c cc tn tht trn ng ngv tn tht ti cc thit b trong h thng. Bn cnh th my nn khng th vn hnh lintc 24h trong 1 ngy c v nu nh th s gy ra ng sut mi lm hng my nn. Vvy cng sut lnh yu cu ca my nn c xc nh nh sau:
Q 0MN =
bkQ.
Trong :k : h s k n tn tht lnh trn ng ng v cc thit b trong h thng lnh.
i vi phng cp ng th nhit phng l 350C nn dng ni suy ta tnh c nhit dn bay hi k = 1,085 (trang 92, ti liu [1])
b : h s k n thi gian lm vic ca my nn. D tnh my nn lm vickhong 22h/1ngy m => chn b = 0,9 (trang 92, ti liu [1])
Vy cng sut lnh yu cu ca my nn l:
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
Q 0MN
=29720,6.1,085
0,9= 35829,83 W
3.2 TNH NHIT CHO PHNG TR NG
S liu cho trc : E = 35 tn , tf = -180
CV 2 phng tr ng c cng sut nh nhau nn ta ch tnh cho phng GHKF l phng lmvic khc nghit nht
1. Tnh tn tht lnh qua kt cu bao che : Q1Ta c : Q1 = Q
dl1 + Q
bx
1 = Qdl1 = ki .Fi.ti , [W]
Vi : - ki: h s truyn nhit ca vch th i. i vi cc vch bao bn ngoi, trn,nn th ki c tnh trong chng 2. Ring i vi tng ngn gia cc phng lnh thta chn k ti u theo bng (3-5) trang 64 ti liu [1]. i vi tng ngn gia 2 bung trng c: kGF = 0,58 W/m2K
- Fi: Din tch b mt kt cu, [m2]- ti: chnh nhit bn ngoi vi mi trng bn trong
+ chnh nhit ca tng ngn gia phng tr ng vi mi trng ngoi :tGH = ( tntf) = 37,3 ( 18) = 55,30C
+ chnh nhit ca tng ngn gia phng tr ng vi phng m:tFK= 0,7( tntf) = 0,7[37,3 ( 18)] = 38,710C
+ chnh nhit ca tng ngn gia 2 phng tr ng :tGF = 0,6( tntf) = 0,6[37,3 ( 18)] = 33,180C
- Chiu cao tnh ton phng lnh l: htt = 3,6 m- Kch thc chiu di tng ngoi : theo mc a), trang 77, ti liu [1]+ i vi bung gc kho : ly chiu di t mp tng ngoi n trc tm tng
ngn=> chiu di tng GH = HK = FK = 6,5m
- Kch thc chiu di tng ngn : tnh t b mt trong ca tng ngoi n tm catng ngn
=> chiu di tng GF = 6m, EC = 2,25m,- Kch thc chiu di nn v trn tnh t b mt trong ca tng ngoi n tm ca
tng ngn=> chiu di nn v trn = 6m.
Kt qu tnh ton c a vo bng tng hp sau:Phng tr ng II: GHKF
Kt cuKch thc,
[m x m]Din tch F,
[m2]ki
[W/m2K]ti
[0C]Qi
[W]
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
Tng GH 6,5 x 3,6 23,4 0,2 55,3 258,8Tng GF 6 x 3,6 21,6 0,58 33,18 415,68Tng HK 6,5 x 3,6 23,4 0,2 55,3 258,8Tng FK 6,5 x 3,6 23,4 0,2 38,71 181,16
Nn 6 x 6 36 0,218 55,3 434Trn 6 x 6 36 0,218 55,3 434Tng 1982,44
2. Tn tht lnh do lm lnh sn phm v bao b Q2:i vi phng tr ng th Q2 = 0 l do nhit tht a vo phng tr ng l 150Cnhit tht khi ra khi phng l -120C, nh vy cn 30C ta dng lm lnh cho bao b
3.Tnh tn tht lnh do vn hnh: Q4Tn tht lnh do vn hnh Q4 bao gm cc tn tht lnh do n chiu sng , do ngi lmvic trong phng,do cc ng c in v do m ca:
Q4= Q1
4 + Q2
4 + Q3
4 + Q4
4 , [W]
Vi: - Q14 : Tn tht lnh do n chiu sng bung lnh
- Q 24 : Tn tht lnh do ngi lm vic trong phng- Q 34 : Tn tht lnh do cc ng c in
- Q 44 : Tn tht lnh do m ca
a. Tn tht lnh do n chiu sng: Q14Q14 dc tnh theo cng thc (4-17) trang 86 ti liu [1] ta c:
Q1
4 = A . F, [W]Vi: - F: din tch phng lnh , [m2]
F = 6 x 6 = 36 m2
- A: Nhit lng to ra khi chiu sng 1m2 din tch bung. i vi phng boqun lnh c A= 1,2 W/m2
=> Q14 = 1,2 .36 = 43,2 W
b. Dng nhit do ngi to ra Q 24 :
Q 24 dc tnh theo cng thc (4-18) trang 86 ti liu [1] ta c:
Q2
4 = 350.n , [W]Vi: - 350: nhit lng do 1 ngi to ra khi lm vic nng nhc
- n l s ngi lm vic trong phng ,v phng c din tch < 200 m2 => chnn = 2
=> Q 24 = 350.2 = 700 W
c.Tn tht lnh do cc ng c in Q 34 :Tn tht lnh do cc ng c in c tnh theo cng thc (4-19), trang 87, ti liu [1]:
Q 34 = .i N i , [kW]
Vi: - :i Hiu sut ca ng c
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
+ i = 1 : Nu ng c t trong phng
+ i = dc : Nu ng c t ngoi phng lnh
i vi phng tr ng ngi ta nh mc cng sut ca ng c in cho phng ccng sut E=20 tn/m l : N = 4 x 0,75 kW
Ta c th tnh cng sut ng c in ca phng tr ngvi cng sut l 35 tn/m l:
N dccd=4.0,75.20
35= 1,71 kW
=> Tn tht lnh do ng c in
Q 34 = .N= 1.1,71= 1,71 kW
( =1 chn ng c t trong phng )
d.Tnh dng nhit khi m ca:Q 44 Dng nhit khi m ca c tnh theo cng thc (4-20) trang 87 ti liu [1]
Q4
4 = B.F , [W]Vi: B: dng nhit ring khi m ca, [W/m2]. Tra bng (4-4) trang 87 i vi
phng tr ng c din tch F= 36 m2 < 50 m2 ta c: B = 22 m2
F= 6x6m2: din tch bung
=> Q 44 = 36.22 = 792 W
Vy tng tn tht lnh do vn hnh l:Q4 = 43,2+ 700 + 1710 + 792 = 3245,2W
4. Tnh nhit kho lnh.
0
Q
= 1Q
+ 2Q
+ 0,7.4
Q
=1
Q
+ 0,7.4
Q
( v 2Q
= 0)Ta ly 0,7. 4Q l do c s khng dng thi v vn hnh. M y ch c 2 phng
tr ng nn chn 0,7. 4Q .
=> 0Q = 1Q + 0,7. 4Q= 2. Q1
+ 0,7.2.Q4= 2.1982,44 + 0,7.2.3245,2= 8508,16W
5. Cng sut lnh yu cu ca my nn
Cng sut lnh yu cu ca h thng lnh l:
Q 0MN =
.o
k Q
b
Trong :k- h s k n tn tht lnh trn ng ng v cc thit b trong h thng lnh.
i vi phng cp ng th nhit phng l -180C nn bng phng php ni suy ta tnh
c k = 1,034 (trang 92 ti liu [1])
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
b- h s k n thi gian lm vic ca my nn. D tnh my nn lm vickhong 22h/1ngy m => chn b = 0,9 (trang 92 ti liu [1])
Vy cng sut lnh yu cu ca my nn l:
Q 0MN
=1,034.8508,16
0,9= 9774,93 W
SVTH : Trn Thanh Sang _ Lp 07N2 Trang : 24
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
CHNG 4 : LP CHU TRNH V TNH CHN MY NN
Mc ch chng ny nhm tnh chn chu trnh ca h thng lnh tnh cng sut yucu ca thit b trong h thng lnh t lm c s tnh chn cc thit b ny .
4.1 TNG QUT1.Chn mi cht lnh
Mi cht s dng trong h thng lnh l R22 v n c nhng u nhc im sau:u im :
+ Khng c hi+ Khng d chy, d n+ Khng n mn kim loi en v kim loi mu+ Khi r r , khng lm hng thc phm cn bo qun+ Ha tan hn ch du , khong nhit -200C -400C khng ha tan du
+ Nng sut lnh ring th tch ln+ p sut ngng t iu kin bnh thng < NH3 + Nhit ha rn thp hn so vi NH3
+ D vn chuyn v bo qunNhc im :
+ t tin hn NH3 .+ Khng ha tan nc+ C tnh ra cn bn nn d gy tc nghn h thng+ Gy nhim mi trng (ph hy tng zn v gy hiu ng nh knh)
Ni chung R22 c hon thin nhit ng cao nn c s dng rng ri .V vy
chn mi cht R22 l ph hp . 2. Chn mi trng gii nhitChn mi trng gii nhit l nc tun hon qua thp trao i nhit v so vi
khng kh th nc lm mt c nhng u im sau :+ H s ta nhit cao hn nn lm mt tt hn+ t chu nh hng ca thi tit
4.2. H THNG LNH TR NGI. Thng s ban u
- Nng sut lnh yu cu Q 0MN
= 9774,93W = 9,77493 kW
- Nhit v trng thi ca i tng lm lnh : t f= - 180C- Chn mi trng gii nhit l nc tun hon qua thp gii nhit :
+ Nhit nc khi vo bnh theo trang 159, ti liu [1] :t 1w = t + (34)0C
Vi: t : l nhit nhit k t ca khng kh c tra theo th i-d vi tn= 37,30Cv m = 73% ,ta c: t = 330C
=> t 1w = 33 + (34)0C = 360C+ Nhit nc ra khi bnh ngng:
t 2w = t 1w + (26)0C
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
y chn bnh ngng ng chm nm ngang nnt 2w = t 1w + 40C = 36 + 4 = 400C
II. Tnh ton chu trnh
1. Chn nhit bay hi :t0 = tf (4 10)0C = -18 (4 10) = - (2228)0CChn to = -250C tra bng hi bo ho ca R22 trang 320 ti liu [1], bng ni suy ta
tnh c p sut bay hi l : p0 = 2,02 bar2. Chn nhit ngng t :
tk = (t 1w +t 2w )/2 + (4 6)0C = (36+40)/2 + 4= 420CChn tk = 40C v mi trng lm mt l nc. Tra bng hi bo ho ca R22 trang
320 ti liu [1] ta c p sut ngng t l: pk = 16,06bar
3. Nhit hi qu nhit
tqn = t0 + tqn = -25 + 25 = 00C- Chn qu nhit tqn = 250C do nhit cui tm nn thp nn qu nhit hi ht rtcao theo trang 161 , ti liu [1]
4. Nhit qu lnhtql = tw1 +tql = 36 + 4 = 40 0C
- Chn qu lnh tql = 40C
5. Tnh cp nn ca chu trnhTa c t s nn ca chu trnh:
= 0p
pk
= 02,2
06,16
= 7,9 < 12Vy chn chu trnh my nn 1 cp
6. Chn chu trnh lnhChn chu trnh lnh cho phng tr l chu trnh my lnh 1 cp dng thit b hi nhit.
Mc d l chu trnh ny b lch ra khi chu trnh Cacno lm cho h s lnh gim xung.Nhng ngc li n trnh c hin tng m v my nn gy ra hin tng thu kch lmhng my nn. i vi freon c th dng bnh tch lng hoc thit b hi nhit nhng dngthit b hi nhit nhiu hn.Do nhit cui tm nn ca chu trnh hi nhit ln hn bnhtch lng
7. Xy dng th v lp bng thng s cc im nt
a. S nguyn l ca chu trnh lnh 1 cp dng thit b hi nhit:
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
q
q
HN
TL
NT
MN
BH
qO
K
HN
Ch thch:MN: My nnNT: Bnh ngng tTL: Van tit luBH: Dn bay hiHN: Thit b hi nhit
b. th T-s v lnP- i:
lnP
1'1
3
i
2
3'
44
1'
3
1
2
s
T
3'
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
Cc qu trnh :1 - 2 :qu trnh nn on nhit trong my nn
2 - 3 :qu trnh ngng t ng p bnh ngng3- 3 :qu trnh qu lnh trong bnh hi nhit3- 4 :qu trnh tit lu trong van tit lu nhit4- 1 :qu trnh bay hi ng p dn bay hi1- 1 :qu nhit hi ht v my nn
c. Nguyn l lm vic:Hi sau khi ra khi thit b bay hi i vo thit b hi nhit nhn nhit ng p ca
lng cao p tr thnh hi qu nhit (1) ri c ht v my nn nn on nhit ln p sutcao (2), sau qua thit b ngng t nh nhit ng p cho mi trng lm mt ngng tthnh lng cao p (3) ri i qua thit b hi nhit nh nhit ng p cho hi h p tr thnhlng cha si (3) qua van tit lu gim p xung p sut bay hi (4) ri i vo thit b bayhi nhn nhit ng p ng nhit ca i tng cn lm lnh, ho hi v chu trnh c thtip tc.
d . Lp bng thng s cc im nt
im Nhit t0C
Ap sutP(bar)
Entanpii(kJ/kg)
Entropis(kJ/kgK)
Th tchv(m3/kg)
Ch thch
1 -25 2,02 695 1,7939 0,1113 Hi bo ho kh1 0 2,02 699 1,8295 0,1259 Hi qu nhit2 80 16,06 755 1,8295 0,0189 Hi qu nhit
3 42 16,06 550 1,1744 0,0010 Lng si3 40 16,06 546 1,1616 0,0005 Lng cha si4 -25 2,02 546 1,1890 0,0389 Hi bo ha m
Xc nh lu lng tun hon qua h thng
G = 00
MNQ
q= 0
1 4
MNQ
i i=
9,77493
695 546= 0,06 kg/s
8. Ph ti nhit ca thit b ngng tQk= G.qk = G.(i2 i3) = 0,06.(755550) = 12,3 kW
9. Nhit lng qua thit b hi nhit QHN= G.qHN = G.( i3i3)= G.( i1 i1)= 0,06.(550546) = 0,24 kW
10. Xc nh cng ca my nnL = G.l = G.(i2 i1) = 0,06.( 755 699) = 3,36kW
11. Tnh chn cng sut lnh- Cng sut lnh phng tr ng:
Q 1 = Q1 = 8508,16kW
- Cng sut lnh ca my nn lnh trong phng tr ngQ 0
MN = 9,77493 kW12. H s lm lnh
=l
q0 = 695 546755 699
= 2,66
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
III. Chn my nn1.Chn my nn
a. Th tch ht thc tVtt = G. v1 = 0,06. 0,1113 = 0,0066m3/s
b. H s cp
C t s nn : =0p
pk=
02,2
06,16= 7,9. Tra th hnh 7- 4 trang 168 ti liu [1] vi my
nn kiu hin i ta c: = 0, 56c. Th tch ht l thuyt
Vlt = ttV
=
0,0066
0,56= 0,0117 m3/s
- Xc nh chu trnh lanh tiu chun :Theo bng (7-1) trang 172 - Ti liu [1] chn ch lnh tr ng 1 cp R22 th c
cc thng s sau:
t0 = -150C => p0 = 2,97 bartk = 300C => pk = 11,9 bartqn = 150Ctql = 250C
Bng thng s ca chu trnh lnh tiu chun:
Tsim
Trng Thit
[0C]p
[bar]v
[m3/kg]i
[kJ/kg]1 Bo ho kh -15 2,97 0,087 698,5
4 Hi bo ha m 30 11,9 537
- Nng sut lnh ring khi lng tiu chunq0tc = i
tc
1 - itc
4 = 698,5 537= 161,5 kJ/kg- Nng sut lnh ring th tch
qV =0
1
q
v=
695 546
0,1113
= 1339kJ/kg
- Nng sut lnh ring th tch tiu chun
qVtc =tcv1
0tcq=
161,5
0,087= 1857kJ/kg
- H s cp iu kin tiu chun
C t s nn : =0
p
pk=
97,2
9,11= 4. Tra th hnh 7- 4 trang 168 - Ti liu [1] vi my nn
kiu hin i ta c: = 0,81- Nng sut lnh tiu chn Q0tc
Q0tc = Q0 .
.
.
v
tcvtc
q
q= 9,77493.
1857.0,81
1339.0,56= 19,6kW
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
Tra bng 7-2 trang 175 ti liu [1] chn :+ My nn piston MYCOM 1 cp c k hiu F2WA2( hngMayekawa Nht),+ QMNtc0 = 32,6 kW > Q0tc lp t
+ Th tch ht l thuyt: Vlt = 71 m3 /h = 0,0197 m3/s
d. S lng my nnZMN = MN
tc
tc
Q
Q
0
0=
19,6
32,6= 0,6 = > Chn Z= 1
=> Vy dng 1 my nn2. Chn ng c ko my
Cng sut ng c in ko my nn c tnh theo cng thc (7-25) trang 171 tiliu [1]
Ndc = (1,12,1).Neli vi cc my lnh nh ch lm vic dao ng ln, in li ln xung php ph nn
chn h s an ton = 2,1Suy ra: Ndc = 2,1.Nel = 2,1.
L
Trong : L- cng nn ca my nn- Tn tht nng lng trong my nn
= i.e.t.elVi: i h s hiu sut ch th do qu trnh nn on nhit thc t
khng phi l qu trnh nn on nhit thun nghch, i c tnh theo cng thc (7-21)trang 217 ti liu [1] :
i =kT
T0 + 0,0025.t0 = 25 27342 273
++
+ 0.0025.(-25) = 0,72
e H s hiu sut c hc do tn tht ma st ti cc b mt chuyn ng (donh ch to quy nh), chn e = 0,92
t H s hiu sut truyn ng gia my nn v ng c, v my nn htruyn ng ai nn chn t = 0,98
el H s hiu sut ca ng c in, chn el =0,9 theo trang 217 ti liu[1]
Suy ra : = 0,72.0,92.0,98.0,9 = 0,58Vy cng sut ng c ko my nn:
Ndc = 2,1.3,36
0,58= 12,16 kW
4.3 H THNG LNH CP NGI. Thng s ban u
- Nng sut lnh yu cu ca my nn Q 0MN
= 35,829 kW- Nhit v trng thi ca i tng lm lnh : t f= - 350C- Chn mi trng gii nhit l nc tun hon qua thp gii nhit :
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
+ Nhit nc khi vo bnh l:t 1w = t + (34)0C
Vi: t- l nhit nhit k t ca khng kh c tra theo th i-d vi t n= 37,30C v m = 73%, ta c: t = 330C
=> t 1w = 33+ (34)0
C = 360
C+ Nhit nc ra khi bnh ngng:t 2w = t 1w + (26)0C
y chn bnh ngng ng chm nm ngang nnt 2w = ts + 40C = 36 + 4 = 400C
II. Tnh ton chu trnh1. Chn nhit bay hi :
t0 = tf (4 10)0C = -35 (4 10) = - (3945)0CChn to = -45 0C tra bng hi bo ho ca R22 trang 320 ti liu [1] ta c p sut bay
hi l : p0 = 0,82662 bar2. Chn nhit ngng t :
tk = (t 1w +t 2w )/2 + (4 10)0C = (36+40)/2 +4= 420CChn tk = 40C v mi trng lm mt l nc. Tra bng hi bo ho ca R22 trang
320 ti liu [1] ta c p sut ngng t l: pk = 16,06 bar 3.Nhit qu lnh tql :
L nhit mi cht lng trc khi i vo van tit lu ,tql cng thp th nng sut lnhcng ln v th ngi ta c gng hn ch nhit qu lnh cng thp cng tt
tql = tw1 + 40C = 36 + 4 0C = 400C , tql = 40C. 4.Nhit qu nhit:
tqn = t0 + tqnVi : tqn : qu nhit hi ht , i vi mi cht lnh R22 th : tqn=250C tqn = -45 + 25 = -200C
L nhit ca hi nc trc khi i vo my nn .Nhit hi ht bao gi cngln hn nhit si ca mi cht . m bo my nn khng ht lng gy hin tngthy kch th ngi ta b tr thit b hi nhit trc khi mi cht lng vo my nn . qunhit ca tng loi my nn i vi tng loi my nn ty thuc vo tng loi mi chtkhc nhau
5. Tnh cp nn ca chu trnhTa c t s nn ca chu trnh:
=0p
pk =83,006,16 = 19,3> 12
Vy chn chu trnh my nn 2 cp, vi p sut trung gian c chn ti u sao cho ts nn bng nhau gia cc cp. Vy p sut trung gian ca chu trnh:
Ptg = kpp .0 = 0,82662.16,06 = 3,6435 bar,=>Tra bng ph lc trang 320 , ti liu [1] ca hi bo ha R22 bng phng php nisuy ta tnh c nhit hi nn trung gian l : ttg= -9,190C.
Chn nhit qu lnh lng trong ng xon trao i nht ca bnh trung gian ln hnnhit lng trong bnh trung gian khong 30C. Khi nhit lng trong ng xon trao
i nhit t6 = ttg + (35) 0C = -9,19 +3 = - 6,19 0C
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
6. Chn chu trnh lnhChn chu trnh cho phng cp ng l chu trnh lnh 2 cp dng bnh trung gian c ng
xon trao i nhit. Bi v do tr lc ca h thng dn bay hi trong phng cp ng khln (> 0,3kg/cm2). Nu dng bnh trung gian lm mt hon ton th c th h s lm lanh
cao hn nhng p sut trung gian khng mnh cp lng cho dn bay hi7. Xy dng th v lp bng thng s cc im nt
1. S nguyn l ca chu trnh lnh
6'6
5'
7
1'
1
HN
BTG
BH
TL2
NHANCA
4 3
NT
2
5TL1
Ch thch :NCA: My nn cao p BTG: Bnh trung gianNHA: My nn h p HN: Hi nhitNT: Bnh ngng tTL: Van tit luBH: Dn bay hi
2. th
SVTH : Trn Thanh Sang _ Lp 07N2 Trang : 32
1 1
45
11
4
5
T
s i
lnp
6'
5'7
2
3
6
6
7
6'
5' 23
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
Cc qu trnh ca chu trnh : 1-1 : qu nhit hi ht v my nn
1-2 : nn on nhit cp h p t P0 ln Ptg2-3 : lm mt hi qu nhit h p xung ng hi bo ha x = 1
3-4 : nn on nhit cp cao p t Ptg ln Pk4-5 : ngng t ng p, ng nhit5-5 : tit lu t Pk xung Ptg5-6 : qu lnh lng ng p trong bnh trung gian6-6 : tit lu t p sut Pk xung P06-1 : bay hi nhn nhit ca mi trng cn lm lnh
3. Nguyn l lm vic :Hi (1) sau khi qua b hi nhit tr thnh hi qu nhit (1) c ht v my nn h
p nn on nhit ln p sut trung gian (2) ri c sc vo bnh trung gian v c lmmt hon ton thnh hi bo ha kh. Hn hp hi bo ha kh (3) c ht v my nn
cao p v c nn on nhit ln p sut ngng t Pk im (4) sau i vo thit bngng t , nh nhit cho mi trng lm mt ngng t thnh lng cao p (5). Ti y lngcao p c chia lm 2 dng :
+ Dng nh i qua van tit lu 1 (TL1) , gim p xung p sut trung gian thnh him (5) i vo bnh trung gian v c tch thnh hi bo ha kh (3) v lng (7) . Lnghi (3) ny cng vi lng hi to thnh do lm mt hon ton hi nn trung gian v doqu lnh lng i trong ng trao i nhit , c ht v my nn cao p
+ Phn ln lng cn li i vo trong ng trao i nhit c qu lnh n (6) , lng 6i qua van tit lu 2(TL2) gim p xung p sut bay hi (6) ri i vo thit b bay hinhn nhit ca i tng cn lm lnh ha hi ng p ng nhit thnh hi bo ha kh
(1) v chu trnh c th tip tc .
4. Lp bng thng s cc im nt
Tsim
Trng Thit
[0C]P
[bar]v
[m3/kg]i
[kJ/kg]s
[kJ/kg.K]
1 Hi bo ho kh -45 0,82662 0,2571 686,361 Hi qu nhit -20 0,82662 0,3152 702,66 1,92 Hi qu nhit 45 3,6435 746,54 1,93 Hi bo ho kh -9,19 3,6435 0,0636 702,51 1,76654 Hi qu nhit 65 16,06 740,82 1,76655 Lng si 40 16,06 549,345 Hi bo ho m -9,19 3,6435 549,347 Lng si -9,19 3,6435 489,366 Lng cha si -6,19 16,06 495,83
6 Hi bo ho m -45 0,82662 495,83
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
5. Tnh ton chu trnha. Xt 1kg mi cht qua thit b bay hi
- Tnh lng hi to thnh do qu lnh lng cao p i trong ng trao i nhit
=73
65
ii
ii
=
549,34 495,83
702,51 489,36
= 0,25kg
- Tnh lng hi to thnh do lm mt hon ton 1kg hi trung p
=73
32
ii
ii
=746,54 702,51
702,51 489,36
= 0,20kg
- Lng hi to thnh khi i qua van tit lu
= ( + ).(53
75
'
'
ii
ii
) = (0,25 + 0,20) .549,34 489,36
702,51 549,34
= 0,17kg
b. Nhit lng nhn c thc t ti thit b bay hiq0 = i1 i6 = 686,36- 495,83 = 190,3 kJ/kg
c. Lu lng thc t qua my nn h p
GHA =0
0
q
Q=
35,829
190,3= 0,18 kg/s
d. Lu lng thc t qua my nn cao pGCA = ( 1+ + + ). GHA = (1+ 0,17+ 0,25 + 0,20). 0,18
= 0,29 kg/se. Nhit thi ra ca bnh ngng :
Qk = GCA (i4 - i5) = 0,29.(740,82- 549,34) = 55,52 [kW] f. Nhit lng thi ra cho mi trng lm mt thit b ngng t:
qk = ( 1+ + + ). ( i4- i5)
= (1+ 0,17 + 0,25 + 0,20).( 740,82 549,34)= 310,19 kJ/kgg. Nhit lng ta ra trong qu trnh qu lnh ng trao i nhit
qql = i5 i6 = 549,34 495,83 = 53,51 kJ/kgh. Cng nn my h p
LNHA = GHA.( i2 i1 ) = 0,18.( 746,54 702,66) = 7,89 kWi. Cng nn my cao p
LNCA = GCA.( i4 i3 ) = 0,29.( 740,82702,51) = 11,1 kWi. Cng nn cho c chu trnh
L = LNHA +LNCA = 7,89 + 11,1 = 18,99 kW
k. H s lm lnh =
L
Q0 =
35,829
18,99= 1,88
III. Tnh chn my nn v ng c ko n1. Tnh chn my nn
a. Th tch ht thc t qua my nn h p v cao pVHAtt = GHA .v1 = 0,18. 0,3152 = 0,056 m3/s
V CAtt = GCA .v3 = 0,29.0,0636 = 0,018 m3/sb. H s cp
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
C t s nn : =0p
ptg=
3,6435
0,82662= 4,4 . Tra th hnh 7- 4 trang 168 ti liu [1] vi
my nn kiu hin i ta c: 1 = 2 = 0,75 c. Th tch ht l thuyt
VHAlt =1
HAttV = 0,056
0,75= 0,074 m3/s
V CAlt =2
CAttV =
0,018
0,75= 0,024 m3/s
Chn 1 my nn 2 cp nh vy ta khng th bit c th tch ht l thuyt ca loimy nn ny l bao nhiu, m ch bit th tch ht l thuyt trong tng cp ca my nn.Do ta chn chu trnh lnh quy chun v xc nh my nn cho chu trnh lnh quy chun lm my nn chy trong h thng lnh thc t.
- Xc nh chu trnh lnh tiu chun :
Theo bng (7-1) trang 172 ti liu [1] chn ch lnh ng 2 cp R22 th c ccthng s sau:t0 = -350C => p0 = 1,325 bartk = 300C => pk = 11,9 bartqn = - 200Ctql = 250C
Suy ra p sut trung gian ca chu trnh:Ptg = kpp .0 = 9,11.325,1 = 3,97 bar
=> ttg = - 6,730C => t6= -6,73 + 3 = - 3,730CBng thng s ca chu trnh lnh tiu chun :
Tsim
Trng Thit
[0C]p
[bar]v
[m3/kg]i
[kJ/kg]1 Bo ho kh -35 1,325 0,1665 690,995 Lng si 30 11,9 536,576 Lng cha si -3,73 11,9 490,456 Hi bo ho m -35 1,325 490,45
- Nng sut lnh ring khi lng tiu chun
q0tc = i
tc
'1 - i
tc
6 = 690,99 490,45 = 200,54 kJ/kg- Nng sut lnh ring th tch tiu chun
qVtc =tcv '1
0tcq=
200,54
0,1665= 1204 kJ/kg
- H s cp iu kin tiu chun
C t s nn : =0p
ptg=
325,1
97,3= 3. Tra th hnh 7- 4 trang 168 ti liu [1] vi my nn
kiu hin i ta c: = 0,84- Nng sut lnh ring th tch
qV = 01'
q
v =190,3
0,2571 = 740 kJ/kg
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
- Nng sut lnh tiu chn Q0tc
Q0tc = 0MNQ .
.
.
v
tcvtc
q
q= 35,829.
1204.0,84
740.0,75= 65,29kW
Chn my nn pitton MYCOM R22 F42B2 bng 7-4 trang 177, ti liu [1] c nng sut
lnh tiu chun :QMN
tc0 = 68,4 kW > Q0tc lp t- S my nn lp t:
Z = MNtc
tc
Q
Q
0
0=
65,29
68,4= 0,95 => Chn Z = 1 my
2.Chn ng c cho my nnCng sut ng c in ko my nn tnh theo cng thc (7-25) trang 171ti liu [1]
Ndc = (1,12,1).Neli vi cc my lnh nh ch lm vic dao ng ln, in li ln xung php ph nnchn h s an ton = 2,1
Suy ra: Ndc = 2,1.Nel = 2,1. L
Trong : L- cng nn ca my nn- Tn tht nng lng trong my nn
= i.e.t.elVi: i h s hiu sut ch th do qu trnh nn on nhit thc t khng phi l qu trnhnn on nhit thun nghch, i c tnh theo cng thc (7-21)trang 170 ti liu[1] :
i =kT
T0+ 0,025.t0 =
45 273
42 273
++
+ 0.0025.(-45) = 0,61
e H s hiu sut c hc do tn tht ma st ti cc b mt chuyn ng (donh ch to quy nh), chn e = 0,92
t H s hiu sut truyn ng gia my nn v ng c, v my nn htruyn ng ai nn chn t = 0,98
el H s hiu sut ca ng c in, chn el =0,9 theo trang 171 ti liu[1]Suy ra : = 0,61.0,92.0,98.0,9 = 0,49
Vy cng sut ng c ko my nn: Ndc = 2,1.18,99
0,49= 81,38 kW
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
CHNG 5: TNH CHN CC THIT B TRAO I NHITV THIT B PH
5.1 TNH CHN THIT B NGNG T
1. Chn thit b ngng tChn thit b ng chm nm ngang c nc lm mt tun hon. Bi v loi thit b ny
c ph ti nhit ln(qF = 45005500 W/m2) nn n t tiu hao kim loi, thit b gn nh,chc chn, lm mt bng nc nn t chu nh hng ca thi tit v d v sinh v phanc lm mt .
2. Mc ch ca thit b ngng tThit b ngng t dng ngng hi nn t my nn thnh lng cao p trc khi qua
van tit lu vo dn bay hi3. Cu to
Ch thch :1. p k,di p k c ng xi phng gim rung cho kim p k2. Van an ton, di van an ton c van chn c lp khi sa cha hoc khi vanan ton mt tc dng3. ng vo hi cao p4. ng cn bng vi bnh cha lng cao p lng trong bnh ngng chy.
v bnh cha d dng5.ng d tr hoc ng x kh khng ngng6,8. ng x kh v x bn v pha nc lm mt7. Np bnh , v khng c p lc nn lm y phng v trong np c cc tm phn
chia to li i cho dng nc9. ng ra ca lng cao p10. ng thp trao i nhit l cc ng ng c cnh v pha Fron v Fron trao i
nhit km hn nc11, 12 .ng vo v ra ca nc lm mt , vo di ra trn m bo bao ph
ton b b mt trao i nhit .
SVTH : Trn Thanh Sang _ Lp 07N2 Trang : 37
7
9
8
54321
12
11
810
6 6
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
4. Nguyn l lm vicy l thit b ngng t lm mt bng nc chuyn ng cng bc bn trong ng. Hi
cao p i vo bnh t pha trn theo ng (3), chim y khng gian th tch bnh. Ti yn nh nhit cho nc lm mt chuyn ng cng bc bn trong ng, ngng t thnh
lng cao p, chy xung di v qua ng (9) i ra ngoi.5. Tnh chn thit b ngng t
- Ph ti nhit ca thit b ngng t :
Qk= Qc
k1 + Q ck
2 = 12,3 + 55,52 = 67,82 kW
- Ly ph ti nhit:qF= 5000 W/m2
- Din tch b mt truyn nhit F: theo cng thc (8-1) trang 214 , ti liu [1]
Fk=k
F
Q
q=
367,82.10
5000= 13,56 m2
Theo bng 8-3 ,trang 204 ,ti liu [1] chn bnh ngngvi cc thng s:
K hiu Din tchb mt
ngoi, m2
ngknh ngv, mm
Chiu ding , m
S ng Ti nhitmax, kW
S li
KTP-18 18 377 1,8 86 62,8 4;2
5.2 TNH CHN THIT B BAY HI
1. Chn thit b bay hiDo Fron ha tan du nn nu dng dn thng thng th khi mi cht bay hi scn li mt lp du(v nhit -20-400C, Fron li khng ha tan du) trn b mtthong ca lng mi cht trong ng trao i nhit lm ngn cn qu trnh bay hi cami cht dn n ngn cn qu trnh trao i nhit. Do dn bay hi Fron phi chpnhn i t trn xung trnh hin tng trn v du v li cacte ca my nn.Chn thit b bay hi kiu dn lm lnh khng kh i lu cng bc. V n c s
dng lm lnh trc tip khng kh m khng cn phi lm lnh gin tip qua cc cht tilnh. Hn na loi ny d v sinh v trnh c hin tng nt ng do cht lng ng
bng
2. Mc ch ca thit b bay hiDng ha hi hi bo ha m sau khi tit lu v ng thi lm lnh mi trng cn
lm lnh.
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
3. Cu to
4
8
6 7
51
2
3
Ch thch : 1. ng lng tit lu vo dn
2. Bp chia : t thng ng,dn c bao nhiu v ng th bp chia c by nhiu l.3. Cc ng chia :phi c chiu di bng nhau phn phi lng cho u.4. Cc v ng trao i nhit : l ng ng c cnh v lm lnh cht kh5. ng gp di6. By du to ch ng du chy tr v my nn7. ng ra ca hi h p8. Dn phun nc x tuyt
4. Nguyn l lm vic.y l thit b bay hi kiu khng ngp lm lnh cht kh chuyn ng cng bc bn
ngoi ng.Lng Freon c tit lu vo dn t pha trn nh bp chia v cc ng chia nn lng
Freon c chia u cho cc v ng nhn nhit ca cht kh chuyn ng i lu cngbc bn ngoi ng ha hi. Chiu di v ng phi c tnh ton sao cho freon i n oncui ca ng phi c hon ton thnh hi v i vo ng gp di 5 ra ngoi.Ph ti nhit : qF = 170340 W/m2
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5. Tnh chn thit b bay hia.H thng dn bay hi cho phng cp ng- Nng sut lnh ca phng cp ng: Q0 = 35,83 kW- Chn ph ti nhit ca thit b bay hi qF = 250 W/m2
=> Din tch b mt trao i nhit : xc nh theo cng thc (8-9), trang 233, ti liu [1] :F 0
F
Q
q= =
335,83.10
250= 143,32 m2
Tra bng 8-14 trang 251 ti liu [1] chn 8 dn qut kiu 2B020 c :- Din tch b mt ngoi : Fd = 20 m2
- Ti nhit khit = 10K : 2320W- S lng qut: 2- Cng sut qut: 100 W- Kch thc ph b: Di x Rng x Cao = 630mm x 765mm x 465mm
b.H thng dn bay hi cho phng tr ng- Nng sut lnh ca thit b bay hi : Qo= 9774,93 W- Chn ph ti nhit ca thit b bay hi : qF = 250 W/m2
=> Din tch b mt trao i nhit :xc nh theo cng thc (8-9), trang 233, ti liu [1] :
F =0
F
Q
q=
9774,93
250= 39,09 m2
Tra bng 8-14, trang 251 ,ti liu [1] chn 2 dn qut kiu 2B020 c :- Din tch b mt ngoi : Fd = 20 m2
- Ti nhit khit = 10K : 2320W- S lng qut: 2- Cng sut qut: 100 W- Kch thc ph b: Di x Rng x Cao = 630mm x 765mm x 465mm5.3 . TNH CHN THIT B PH
1. Bnh cha cao pa. Mc ch
- Bnh cha cao p mc ch cp lng n nh cho van tit lu. Ch c trong hthng lnh trung bnh v ln
- Ngoi ra n cn c nhim v cha lng t cc thit b khc v khi sa cha hthng
V tr : nm sau thit b ngng t v trc van tit lu.b. Cu to
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BNH CHA CAO AP
Ch thch : 1. p k , di p k c ng xiphng gim rung cho kim p k
2. Van an ton, di van an ton c van chn c lp khi sa cha hoc khi vanan ton mt tc dng3. ng vo ca lng cao p4. ng cn bng vi thit b ngng t lng t bnh ngng chy xung bnhcha d dng5. ng d tr hoc lm ng x kh khng ngng6. ng thu sng quan st mc lng trong bnh7. ng ra ca lng cao p ti van tit lu
c. Tnh ton bnh cha cao pTa chn h thng lnh mi cht Fron chy t trn xung nn th tch cha c
tnh theo cng thc 8 -13, trang 260, ti liu [1] ta c :
VCA =0,3.
.1,20,5
dV
= 0,72Vd
Vi : 1,2 H s an ton
VCA Th tch bnh cha cao pVd Th tch h thng dn bay hi2. Bnh tch du
a. Mc ch- trnh du bm bn b mt trao i nhit ca cc thit b trao i nhit ( thit b
ngng t ,bay hi.) , lm gim hiu qu trao i nhit.b. Cu to
Chn bnh tch du kiu t v dng chung cho cc my nn lnh
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7
2
6
3
4
5
1
Ch thch :1.ng vo ca hi cao p2. Van an ton
3. ng ra hi cao p4.Cc nn chn , thc t dng 3 nn khoan l 10mm, bc 20mm5. Ming phun ngang6. Tm chn du khoan l40 mm
y 5 v 6 c mc ch l dng hi khng sc thng vo lp du pha di lmvng du v cun du theo lm gim hiu sut tch du .7. ng x du.
c.Nguyn l lm vic:Du c tch nh 3 nguyn nhn:
- Gim vn tc ca dng khi i t ng nh ra ng to lm lc qun tnh gim v di
tc dng ca trng lc cc ht du nng ri xung- Do lc ly tm khi ngot dng cc ht du nng b vng ra va p vo thnh bnh ri
xung di-Do s mt vn tc t ngt khi va p vo cc tm chn. Cc ht du nng c gi
li v ri xung y bnhd. Tnh chn bnh tch du. Ch tnh chn bnh tch du kiu t
- ng knh ng : theo ti liu [2] trang 222 ta c:
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n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
d4 hV
=
Trong :
+ :tc mi cht ng ni vo bnh tch du
Chn = 18 [m/s] (theo ti liu [2] trang 222)+Vh :th tch ring thc t ca mi cht ra khi my nnVh = Vcd + Vtd = (0,056+ 0,018)+0,0066= 0,0806[m/3s]
d4 4..0,0806
0,07163,14.20
hV
= = = m = 71,6[mm]
=> Chn loi bnh 100-MO.+ 100: ch ng knh ng ni vo u y my nn+ MO: ch loi bnh
3. Thit b tch kh khng ngng:a. Mc ch:Nhm loi kh khng ngng ra khi thit b ngng t tng din tch trao i nhit.
b. Cu to
2
1
5
4 3
Ch thch :1 - ng ra ca hi h p nhng trc khi v my nn phi qua bnh hi nhit trnh hin tng thu kch.2- ng vo ca hn hp kh khng ngng v hi cao p c ly t bnh cha caop v thit b ngng t3 -ng lng cao p tit lu vo ng trong.4- ng tit lu ca lng cao p ngng t.5 -ng x kh khng ngng.
c. Nguyn l lm vic:
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Hn hp hi cao p v kh khng ngng t thit b ngng t qua bnh cha cao pc i vo khng gian gia hai ng nh nhit cho mi cht lnh l lng cao p tit luvo trong ng trong (3) .Hi cao p c ngng li thnh lng chy xung di v qua vantit lu (4) vo li trong ng trong. Kh khng ngng t li pha trn qua ng (5) x rangoi.
4.Bnh hi nhit:a. Mc ch:
- Dng p qu nhit dng hi ht v my nn nhm trnh hin tng thy kch.- Qa lnh lng cao p trc khi vo tit lu nhm gim tn tht lnh do tit lu.
Thit b c t sau thit b bay hi,trc my nn.b. Cu to:
1v 3: ng ra v vo ca hi h p2 : Li st bt hai u nhm hng ng i ca dng hi tip xc vi ngxon(6) v va lm tng tc ca dng hi nhm tng cng qu trnh trao i nhit.4 v5: ng ra v vo ca lng cao p.6 : ng xon.
c. Nguyn l lm vic:Hi h p i vo pha trn ca bnh trao i nhit vi lng cao p i trong ng xon tr
thnh hi qu nhit c ht v my nn.Hi ra phi c ly t pha di ht du vmy nn.Lng cao p i trong ng xon ngc vi chiu dng hi tng cng qa trnh
trao i nhit.Bnh ny c bc cch nhit.
5. Bnh gom du a. Mc ch
- trnh nguy him khi x du t cc thit b c p sut qu cao ra ngoi.- d thao tc thu hi du t cc thit b c p sut chn khng
b. Cu to
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BNH CHA DU
3
n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
1. ng vo ca du;2. ng cn bng;3. p k4. ng x du
c. Nguyn l lm vic- x du t 1 thit b no v bnh gom th chng ta thao tc sao cho p sut
trong bnh gom du thp hn p sut ca thit b cn x bng cch m van 2- x du t bnh gom ra ngoi c 2 trng hp:
+ p sut trong bnh gom qu cao: M van 2 p sut trong bnh ch cao hn khquyn 1cht
+ p sut trong bnh chn khng: Th ta m van x du bnh tch du nng cao psut trong bnh ln cao hn p sut kh quyn 1 cht
- Bnh ny ch lm nhim v trung gian x du ra ngoi cho thun tin v an ton nnkhng cn ng thu xem mc du
d. Tnh ton bnh cha duChn bnh cha du c k hiu 150CM ( l loi bnh tiu chun b nht trong phm
vi ti liu [1] bng 8-20 trang 267 ) vi cc thng s sau :DxS = 159 x 4,5 mmB = 600 mm ,H = 770 mm ,Th tch 0,008 m3
,Khi lng 18,5 kg
6. Bnh trung giana. Mc ch
- Lm mt trung gian hon ton hi trung p gia cc cp nn trong h thng lnh lmgim cng nn v nhit cui tm nn cho my nn cao p
- Tch lng, tch du ra khi hi trung p ht v my nncao p- Lm qu lnh lng cao p trc khi tit lu gim tn tht lnh do tit lu.
b. Cu to
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12
1 2
5
11
6
3
4
11
98
7
13
n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
1. ng vo ca hi nn trung p2. ng lng cao p tit lu vo bnh3. ng ra ca hi trung p
4. Cc nn chn5. ng thu ti v van phao6. Phin lc7. ng xon TN8. ng x du9. ng tho lng ra khi bnh10. ng ra lng cao p11. Van an ton12. p k
13. L cn bng
c. Tnh chn bnh trung gian
Ta c th tnh chn bnh trung gian theo ccbc c trch mc 8.2.1.4 trang 296298ti liu [3]:
-Din tch truyn nhit ca thit b trunggian
Ftg =f
tg
qQ
Vi : Qtg Cng sut nhit trao i bnh trung gianQtg = Qql + Qlm
Qql : Cng sut nhit qu lnh ca mi cht trc tit luQql = GHA.( i5 - i6 ) = 0,18.(549,34 495,83) =9,63 kW
Qlm :Cng sut nhit lm mt trung gianQlm = GCA.( i2 - i3 ) = 0,29.(746,54 702,51) = 12,76 kW
Suy ra: Qtg = 9,63 + 12,76 = 22,39 kWqF Mt dng nhit ca thit b ngng tqF = 5000 W/ m2
Suy ra Ftg =f
tg
q
Q=
322,39.10
191,48= 4,48 m2
- ng knh trong bnh trung gian :
Di =4.
.
V
Trong :
+ V: Lu lng th tch trong bnh, bng lu lng ht ca cp nn cao pV = GCA. v3 = 0,29.0,0636= 0,018 m3/s
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1
7
n mn hc : K Thut Lnh GVHD : Nguyn Thnh Vn
+ : Tc gas trong bnh, chn = 0,6 m/s
Suy ra: Di =4.
.
V
=
4.0,018
3,14.0,6= 0,19 m
Chn bnh trung gian c ch to sn, (Tra bng 8-19 trang 266-Ti liu [1] )
Chn loi 40C3 c k hiu 40C3 vi cc thng s k thut+ ng knh ngoi : Da = 426mm+ ng knh trong : Di = 406 mm+ ng knh ng xon: d = 70 mm+ Chiu cao: H = 2390mm+ Din tch b mt ng xon: F = 1,75 m2
+ Th tch bnh: V = 0,22 m3
+ Khi lng: m = 330 kg7. Tnh chn thp gii nhit
a. Mc ch:
gii nhit cho nc lm mt thit b ngng t v my nnb. Cu to
Ch thch :1.Qut ht2.Tm chn nc khi vng ra ngoi
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3. Dn phun nc gm 2 ng khoan l nghing mt gc 450 i nhau c gnvomt xoay khi phun nc c quay trn ti u trn ton b thit b4. B phn lm ti nc nhm lm tng b mt tip xc vi khng kh tng hiuqa lm mt5.Van phao cp nc b sung ( b kng hi nc b gi cun ra ngoi)6.ng vo ca nc c lm mt7.Mng nc8. ng vo ca nc c lm mt
c. Nguyn l lm vic:Nc nng t thit b ngng t i vo thp v c ti u trn ton b din tch thpnh ng ti nc 3. Sau nc lm ti nh b phn lm ti nc 4 nh nhit cho gichuyn ng cng bc t di ln, ngui v tr li nhit ban u chy xung mng vc bm 8 tr li thit b ngng tLng nc hao ht do cun theo gi v 1 phn nc bc hi c b sung qua ngvan phao 5
d.Tnh chn thp gii nhit:Ta c ph ti nhit ca thit b ngng t Qk= 55,52 kW. Ta quy nng sut lnh
ra ton . Theo tiu chun CTI 1 ton nhit tng ng 3900 kcal/hQk =55,52 kW
V = kw 2 w1
Q
. .( )C t t = 4.1000.187,4.548,57
= 0,0034 [m3 /s] = 3,4[l/s]
Tra bng 8- 22 trang 272 ti liu [1] chn thp gii nhit FRK20 vi cc thng s :
+ Lu lng nc nh mc 4,4 l/s+ Chiu cao thp 1845 mm+ ng knh thp 1170 mm+ ng knh ng ni dn vo 50 mm
+ ng knh ng ni dn ra 50 mm+ ng chy trn 25 mm+ ng knh ng van phao 15 mm+ Lu lng qut gi 170 m3/ph
+ ng knh qut gi 760 mm+ M t qut 0,37 kW+ Khi lng tnh 58kg
8. Cc thit b khcChn cc thit b khc bao gm: Van 1 chiu, van chn, van tit lu,
van din t ta c th chn theo ng knh ca h thng ng ng ni chng
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Ti liu tham kho :
[1]- Hng dn thit k h thng lnh - Nguyn c li
[2]- Bi tp k thut Lnh -Nguyn c li, Phm Vn Tu
[3]- H thng my v thit b lnh- V Ch Chnh
[4] - K thut lnh ng dng-Nguyn c li, Phm Vn Tu, inh VnThun
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MC LC
TrangChng M U 1
. ngha ca lnh 2. Mc ch cp tr ng 2III .Nhim v ca n
1. Cp ng:2. Tr ng:3. a im lp t4. Qui trnh cng ngh
Chng 1: XC NH KCH THC V B TR MT BNG KHO LNH 31.1 Tnh kch thc phng cp ng 3
1. Tnh th tch cht ti: Vct2. Tnh din tch cht ti : Fct3. Chiu cao trong ca phng cp ng4. Chiu cao trong ca phng cp ng5. Xc nh s phng cp ng: Z
1.2 Tnh kch thc phng tr ng 51. Tnh th tch cht ti: Vct2. Tnh din tch cht ti : Fct
3. Chiu cao trong ca phng tr ng4. Chiu cao trong ca phng tr ng5. Xc nh s phng tr ng: Z
1.3 B tr mt bng kho lnh 5Chng 2: TNH CCH NHIT CHO KHO LNH2.1 Tnh cch nhit cho tng bao kho lnh 6
1. Kt cu v cc s liu ca n2.Tnh ton3. Kim tra nhit ng sng
2.2 Tnh cch nhit trn kho lnh 9
1. Kt cu v cc thng s ca n2.Tnh ton3. Kim tra nhit ng sng
2.3 Tnh cch nhit nn kho lnh 121. Kt cu v cc thng s ca n2.Tnh ton3. Kim tra nhit ng sng
2.4 B tr cch nhit cho kho lnh 15Chng 3: TNH NHIT H THNG LNH3.1 Tnh nhit cho phng cp ng 17
1. Tnh tn tht lnh qua kt cu bao che : Q12. Tnh tn tht lnh do lm lnh sn phm v bao b: Q2
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3.Tnh tn tht lnh do vn hnh: Q44. Tnh nhit kho lnh5. Cng sut lnh yu cu ca my nn
3.2 Tnh nhit cho phng tr ng 211. Tnh tn tht lnh qua kt cu bao che : Q12. Tn tht lnh do lm lnh sn phm v bao b Q2:3.Tnh tn tht lnh do vn hnh: Q44. Tnh nhit kho lnh.5. Cng sut lnh yu cu ca my nn
Chng 4: LP CHU TRNH V TNH CHN MY NN4.1 Tng qut 254.2 H thng lnh cho phng tr ng 25
. Thng s ban u. Tnh ton chu trnh
1. Chn nhit bay hi :2. Chn nhit ngng t :3. Tnh cp nn ca chu trnh4. Chn chu trnh lnh5. Chn qu lnh, qu nhit6. Xy dng th v lp bng thng s cc im nt7. Xc nh lu lng tun hon qua h thng8. Ph ti nhit ca thit b ngng t9. Xc nh cng ca my nn10. Tnh chn cng sut lnh11. H s lm lnh
. Chn my nn1.Chn my nn2. Chn ng c ko my
4.3 H thng lnh cho phng cp ng 30. Thng s ban u. Tnh ton chu trnh
1. Chn nhit bay hi :2. Chn nhit ngng t :3. Tnh cp nn ca chu trnh4. Chn chu trnh lnh5. Chn qu lnh, qu nhit6. Xy dng th v lp bng thng s cc im nt7. Tnh ton chu trnh
. Tnh chn my nn v ng c ko n1. Tnh chn my nn2.Chn ng c cho my nn
Chng 5: TNH CHN CC THIT B TRAO I NHIT VTHIT B PH
5.1 Tnh chn thit b ngng t 361. Chn thit b ngng t
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2. Mc ch ca thit b ngng t3. Cu to5. Tnh chn thit b ngng t4. Nguyn l lm vic
5.1 Tnh chn thit b bay hi 371. Chn thit b bay hi2. Mc ch ca thit b bay hi3. Cu to4. Nguyn l lm vic.5. Tnh chn thit b bay hi
5.3 Tnh chn thit b ph 391. Bnh cha cao p2. Bnh tch du3. Thit b tch kh khng ngng4. Bnh hi nhit5. Bnh gom du6. Bnh trung gian7.Tnh chn thp gii nhit
Ti liu tham kho 48
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Contents
CH NG M U .......................................................................................................1I. NGH A C A L NH ..........................................................................................1II. M C CH C P, TR NG .....................................................................................1III. NHI M V C A N ...........................................................................................1
1. C p ng : .....................................................................................................12. Tr ng : .....................................................................................................13. a i m l p t h th ng l nh : ...................................................................14. Quy trnh cng ngh : .....................................................................................2
CH NG 1 : XC NH KCH TH C V B TR M T B NG KHO L NH ....................31.1 TNH KCH TH C PHNG C P NG ...................................................................33. Di n tch trong c a phng l nh: Ftr .........................................................................31.2 TNH KCH TH C PHNG TR NG. .................................................................45. Xc nh s phng c p ng: Z ...............................................................................41.3 . B TR M T B NG KHO L NH .............................................................................5
CH NG 2: TNH CCH NHI T CHO KHO L NH .........................................................61. K t c u v cc s li u c a n ..............................................................................7
2.Tnh ton..................................................................................................................73. Ki m tra nhi t ng s ng ................................................................................8
2.2 TNH CCH NHI T TR N KHO L NH .....................................................................91. K t c u v cc thng s c a n .........................................................................9
2. Tnh ton.............................................................................................................103. Ki m tra nhi t ng s ng ..............................................................................11
2.3 TNH CCH NHI T N N KHO L NH ......................................................................121. K t c u v cc s li u c a n ............................................................................12
2. Tnh ton .....................................................................................................133. Ki m tra nhi t ng s ng ...............................................................................142.4 B TR CCH NHI T KHO L NH ..........................................................................14
CH NG 3 : TNH NHI T H TH NG L NH ..............................................................153.1 TNH NHI T PHNG C P NG ..........................................................................171. Tnh t n th t l nh qua k t c u bao che : Q1 ...................................................17
2. Tnh t n th t l nh do lm l nh s n ph m v bao b: Q2 ........................................183.Tnh t n th t l nh do v n hnh: Q4 ........................................................................194. Tnh nhi t kho l nh ................................................................................................205. Cng su t l nh yu c u c a my nn ....................................................................203.2 TNH NHI T CHO PHNG TR NG ...................................................................21
1. Tnh t n th t l nh qua k t c u bao che : Q1 .....................................................212. T n th t l nh do lm l nh s n ph m v bao b Q2: ...............................................22
3.Tnh t n th t l nh do v n hnh: Q4 ....................................................................224. Tnh nhi t kho l nh. ...........................................................................................23
5. Cng su t l nh yu c u c a my nn ..................................................................23CH NG 4 : L P CHU TRNH V TNH CH N MY NN .............................................254.1 T NG QUT ........................................................................................................251.Ch n mi ch t l nh ..............................................................................................25
2. Ch n mi tr ng gi i nhi t ..............................................................................254.2. H TH NG L NH TR NG ...........................................................................25
I. Thng s ban u ..............................................................................................25II. Tnh ton chu trnh...............................................................................................261. Ch n nhi t bay h i : .......................................................................................262. Ch n nhi t ng ng t : .....................................................................................263. Nhi t h i qu nhi t .......................................................................................26
4. Nhi t qu l nh .............................................................................................265. Tnh c p nn c a chu trnh .................................................................................266. Ch n chu trnh l nh ..............................................................................................26
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7. Xy d ng th v l p b ng thng s cc i m nt .............................................268. Ph t i nhi t c a thi t b ng ng t ......................................................................28
9. Nhi t l ng qua thi t b h i nhi t .................................................................2810. Xc nh cng c a my nn ........................................................................28
11. Tnh ch n cng su t l nh ...................................................................................2812. H s lm l nh ..................................................................................................28
III. Ch n my nn ......................................................................................................291.Ch n my nn ......................................................................................................29
2. Ch n ng c ko my ...............................................................................304.3 H TH NG L NH C P NG ..............................................................................30
I. Thng s ban u ...............................................................................................30II. Tnh ton chu trnh...............................................................................................311. Ch n nhi t bay h i : .......................................................................................312. Ch n nhi t ng ng t : .....................................................................................31
3. Nhi t qu l nh tql : ....................................................................................314. Nhi t qu nhi t: ......................................................................................31
5. Tnh c p nn c a chu trnh .............................................................................316. Ch n chu trnh l nh ..........................................................................................327. Xy d ng th v l p b ng thng s cc i m nt ..........................................32
III. Tnh ch n my nn v ng c ko n .................................................................341. Tnh ch n my nn .............................................................................................34
2.Ch n ng c cho my nn ........................................................................36CH NG 5: TNH CH N CC THI T B TRAO I NHI T V THI T B PH 375.1 TNH CH N THI T B NG NG T .......................................................................37
1. Ch n thi t b ng ng t .....................................................................................372. M c ch c a thi t b ng ng t ..........................................................................373. C u t o ..............................................................................................................37
4. Nguyn l lm vi c ..........................................................................................385. Tnh ch n thi t b ng ng t .............................................................................38
5.2 TNH CH N THI T B BAY H I ............................................................................381. Ch n thi t b bay h i .......................................................................................38
2. M c ch c a thi t b bay h i .........................................................................38
3. C u t o Ch thch : ...........................................................................................394. Nguyn l lm vi c. .............................................................................................39
5. Tnh ch n thi t b bay h i ...............................................................................405.3 . TNH CH N THI T B PH ..................................................................................40
1. Bnh ch a cao p ................................................................................................402. Bnh tch d u .......................................................................................................41
3. Thi t b tch kh khng ng ng: ..............................................................................434.Bnh h i nhi t: ........................................................................................................445. Bnh gom d u ........................................................................................................44
6. Bnh trung gian a. M c ch ...................................................457. Tnh ch n thp gi i nhi t ...................................................................................478. Cc thi t b khc ...........................................................................................48Ch n cc thi t b khc bao g m: Van 1 chi u, van ch n, van ti t l u, van di n t ta
c th ch n theo ng knh c a h th ng ng ng n i chng ..............................48Ti li u tham kh o : ...................................................................................................49