trao doi nhiet

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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By: Ly Ngoc Minh 3

2. Thiet b trao oi nhiet loai vach ngana.loai vo boc ong chum:


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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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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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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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By: Ly Ngoc Minh 8


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By: Ly Ngoc Minh 9


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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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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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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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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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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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By: Ly Ngoc Minh 18

b) loi ng ti

Cu to:


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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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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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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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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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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

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trao doi nhiet