Download - trao doi nhiet
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8/6/2019 trao doi nhiet
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 2
1. Khi nim v phn loi
Khi nin:
Thit b trao i nhit l thit b trong
thc hin cc qu trnh truyn nhit giacc cht mang nhit.
Phn loi:
Trao i nhit dng vch ngn
Trao i nhit loi hi nhitTrao i nhit loi hn hp.
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 3
2. Thiet b trao oi nhiet loai vach ngana.loai vo boc ong chum:
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 4
loai vo boc ong chum nam ngang.
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By: Ly Ngoc Minh 5
.loai trao oi nhiet co canh:
b.
loai trao oi nhiet co tam gn song:
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 6
3. Thiet b trao oi nhiet loai hoi nhiet.
4. Thiet b trao oi nhiet loai ho
n hp.
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 7
II. CAC PHNG TRNH TNH TOAN THIET BTRUYEN NHIET LOAI NGAN CACH:
1. Cach bo tr dong chay cac chat tai nhiet va cac ky hieu:
t1
t1
t2
t2
t t
t1
t2
dt1
dt2
F(
x)x x+d
x
dF
L
t
t1
t1
t2
t2t
t1
t2
dt1
dt2
F(
x)x x+d
x
dF
L
t
t
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 8
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 9
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 10
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By: Ly Ngoc Minh 11
THIT B TRAO I NHIT LOI
VCH NGN
Trong kthut cng nh trong snxut, i sng thit b trao i nhitgin tip thng qua vch ngn l
loi c s dng ph cp nht.
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 12
1. Loi v bc
Cu to
CCC LOC LOI THII THIT BT B THTHNG GNG GPP
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 13
Qu trnh truyn cht ti nhit s c avo khong tr ng gia hai lp v thchin un nng hay lm ngui.
Chiu cao ca v ngoi khng c thphn mc cht lng trong thit b.
tng hiu sut truyn nhit ngi tathng t thm cnh khuy.
NGUYN L HOT NG
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 14
U NHC IM CA THIT
B u im :
ch to n gin, d vn hnh,d bo dng sa cha
Nhc im :
h s truyn nhit khng cao,thit b cng knh
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By: Ly Ngoc Minh 16
Nguyn l lm vic:khi lm vic th mt mi cht ingoi ng, cn mi cht kia i
trong ng. Cht lng i trong ngth phi i t di ln, hi ncdng trong truyn nhit th phi it trn xung.
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 17
U NHC IM
u im:to b mt trao i nhit ln
Nhc im:ch to phc tp, h s truyn nhit nh,kh lm sch pha trong ng
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 18
b) loi ng ti
Cu to:
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 19
Nguyn l lm vic:
Cht lng ti bn ngoi thng lnc, chy ln lt t ng trn xungng di ri chy vo mng.
Mt ti khong 200-1500 l/h/1mchiu di ca ng ti dy trn cng.
Cht ti nhit s i bn trong cc ng
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 20
U NHC IM
u im:lng nc lm lnh t, cu to n gin, d lm
sch b mt ngoi, d thay th, sa cha Nhc im:cng knh, lng nc khng c ti u trnb mt ng
ng dng:thng dng lm thit b lm lnh v ngng t
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By: Ly Ngoc Minh 21
Cu to: Mt ng c ng knh ln bc mt hocnhiu ng nh bn trong; hoc gm nhiung ni tip vi nhau, mi on c hai
on ng lng vo nhau.
ng trong c th trn hoc c cnh dctheo chiu di ca ng.
c)c) LoLoii ngng llngng ngng
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By: Ly Ngoc Minh 22
Nguyn l lm vic: cht ti nhit mt i gia hai
ng, cht ti nhit hai itrong ng trong.
Chuyn ng ca mi chtthng c b tr ngcchiu nhau.
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By: Ly Ngoc Minh 23
u im:c h s truyn nhit ln, d iuchnh tc chy ca mi cht, chto n gin.
Nhc im:cng knh, gi thnh cao, kh vsinh, sa cha.
ng dng:dng ngng t hoc bay hi micht lnh, lm qu lnh mi cht lnh th lng, hay dng un nng nc,lm mt du
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By: Ly Ngoc Minh 24
d)Loi ng chmCu to: C v hnh tr, bn trong lp cc ng trao
i nhit.
Trn v v np thit b c cc ca dncht ti nhit vo v ra.
Cc ng trao i nhit bn trong c th b trtheo hnh lc gic u, hnh trn ng tm,hnh vung.
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By: Ly Ngoc Minh 25
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By: Ly Ngoc Minh 26
Nguyn l lm vic:
hai mi cht trao i nhit vi nhauthng qua vch ng.
Mi cht lng thng i trong ng, micht kh v hi i ngoi ng. Mi chtnng cng thng c b tr i trong
ng.
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By: Ly Ngoc Minh 27
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By: Ly Ngoc Minh 28
U NHC IM:
u im: kt cu gn, chc chn, cngngh ch to khng phc tp, b mttruyn nhit ln, d v sinh, sa cha.
Nhc im: kh ch to bng vt liudn, gi thnh cao.
ng dng: dng lm bnh ngng t vhi mi cht, bnh bc hi cho mylnh, lm bnh qu lnh.
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By: Ly Ngoc Minh 29
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By: Ly Ngoc Minh 30
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By: Ly Ngoc Minh 31
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By: Ly Ngoc Minh 32
e. Loi ng c cnh
Cu to: Cc cnh trn ng thng c chiu cao
tng i lnnngi l cnh di.
Cnh lm bng vt liu dn nhit tt vthng c cu to kiu cnh dc vcnh ngang.
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 33
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By: Ly Ngoc Minh 34
Nguyn l hot ng
mi cht chuyn ng trong ng l chtlng hoc hi nc c h s ta nhit lnhn nhiu so vi h s ta nhit ca chtkh bn ngoi.
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By: Ly Ngoc Minh 35
ng dng:
Dng trong cc thit b un nngnc trong ng l si hi nc t nng khng kh.
Dn bc hi trong my lnh hocmy iu ha nhit c cnh bnngoi lm lnh khng kh; dn
ngng t lm mt bng khng khtrong my lnh c cnh bn ngoing ta nhit cho khng kh
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 36
3. Thit b c dng tm:
Cu to: c thnh phn c bn l cc tm trao
i nhit c bn. B mt gm nhiu tm xp ln mt
khung , bn trong c cc khe rnh lu cht chuyn ng.
Vt liu thng l thp khng g,nhm
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By: Ly Ngoc Minh 37
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By: Ly Ngoc Minh 38
Nguyn l hot ng:
khi cht lng lu ng qua cc khernh, mi cht s chuyn ng didng mng mng nn to r a h strao i nhit rt cao to iu kin tt t nng hay lm lnh mi cht.
Cc tm thng t song song vinhau to ra cc khang khng gianhp to nn cc knh dn ring bitcho cc mi cht khc nhau
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8/6/2019 trao doi nhiet
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By: Ly Ngoc Minh 39
u Nhc im:
u im:
-m bo h s truyn nhit cao vi hiu str khng thy lc thp
-Thit b gn nh, chi ph ch to thp-Lm vic ng tin cy, khng b r r
-Kt hp hi ha gia lp t v bo dng
thit b Nhc im :
Ch to cc tm truyn nhit thng phiqua x l nhit v gia cng phc tp
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By: Ly Ngoc Minh 40
Tnh tan cho thit b trao i nhit
C 2 dng bi tan chnh
Bi tan thit k
Bi tan kim tra
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By: Ly Ngoc Minh 41
Tnh ton thit b TN
Bc 1:
B tr s chuyn ng v tc mi cht chuynng trong thit b trao i nhit. Ch chuyn
ng ca mi cht thng l ch chy ri: Bc 2:
Tnh nhit trung bnh ca 2 mi cht
m a x m i nt b
m a x
m i n
t tt
tl n
t
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By: Ly Ngoc Minh 42
Bc 3: Xc inh lng nhit trao i. Khi bqua tn tht nhit ta da vo phng trnh
cn bng nhit :Qtoa=Qthu
Khi c 2 mi cht khng bin i pha:
Q=G1cc1(t1d-t1c)=G2c2(t2c-t2d) Khi mt cht c bin i pha:Q=D1(I1-i1)=G2c2(t2c-t2d)
Khi c hai mi cht u c bin i pha:
Q=D1(I1-i1)= D2(I2-i2)Lu :n v ca cc thng s: G, D (kg/s);I,i (J/kg); c (J/kg.K); Q(W)
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By: Ly Ngoc Minh 44
Bc 5: Xc nh b mt trao i nhit
Da vo phng trnh truyn nhit:Q=k.F.ttb
Bc 6: xc nh lng nhit tn tht:
3
tt f 2Q .10 .F (t t )
4 4
1 / 4 tT T
2.5. t 58. . 100 100
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By: Ly Ngoc Minh 45
Bi tan kim tra :
Vi mt thit b c sn bit titdin F, nhit mi cht, lu lngmi cht vo. kim tra li s lm
vic ca thit b cn tnh lngnhit trao i Q, nhit ra ca ccmi cht