Bài Thi Nghiem Qua Trinh Thiet Bi

8/12/2019 Bi Thi Nghiem Qua Trinh Thiet Bi

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GVHD: V PH

SVTT: TRN THH

MSSV: 3004120

Tp.HCM, thng 06 nm 04


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THC HNH CC QU TRNH V THIT B GVHD: V PHM PHNG TRANG

SV: TRN THHNG PHNG Trang 1

BI 1: SY

1. Mc tiu.- Vn hnh c hthng thit bsy.- Tnh ton c cc thng ssy: tc sy ng tc, m ti hn,

m cn bng, thi gian sy ng tc v gim tc.

- Xy dng ng cong sy v ng cong tc sy da trn sliuthc nghim.

2. sl thuyt.2.1. nh ngha-

Sy l qu trnhlm bc hi nc ra khi vt liu bng nhit, nhitc cung cp cho vt liu nhdn nhit, i lu nhit, bc xnhit

- Sy i lu l qu trnh tch m ra khi vt liu bng cch cp nhitcho m bay hi.Trong , chai qu trnh truyn nhit v truyn m u

c thc hin bng phng php i lu.

2.2. c trng ca qu trnh sy.Qu trnh sy din ra rt phc tp, c trng cho tnh khng thun

nghch v khng n nh. N din ra ng thi 4 qu trnh: truyn nhit cho

vt liu, dn m trong lng vt liu, chuyn pha v tch m vo mi trng

xung quanh.

2.3. Tc sy theo cn bng nhit ca qu trnh sy.Lng nhit do dng tc nhn sy cung cp cho khong thi gian d

dQ = F(t (1)

Nhit ny c tiu hao :

- un nng vt liu: ( (2)- Bay hi m v qu nhit hi: (3)

rong :

: hscp nhit ttc nhn sy vo vt liu sy (W/m2)


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F: bmt vt liu (m2)

t, nhit tc nhn sy, vt liu v hi bo ha ()

: khi lng v nhit dung ca vt liu sy (kg; j/kg)

khi lng v nhit dung ca m (kg; j/kg)r: n nhit ha hi ca m (j/kg)

nhit dung ring ca hi m (j/kg)

Lng m bc hi trong thi gian d:

(4)

U: hm m (hay m) ca vt liu, tnh theo vt liu kh (kg m/kg vt

liu kh)

T(1), (2), (3) v (4), thit lp cn bng nhit:

(5)

T(5) rt ra: c biu thc tc sy theo cn bng nhit

y l biu thc tc sy theo cn bng nhit

2.4. hng trnh c bn ca ng hc qu trnh sy.Theo phng trnh truyn m tvt liu vo tc nhn sy:

(7)

Vi: : hstruyn m trong pha kh (kg/m2.h.p)

, p: p sut ca hi m trn bmt vt liu v trong pha kh (mmHg

hay at)

Thay vo (7) v bin i ta c:

(8)Khi hi m khng bqu nhit (tc t=) th biu thc (5) c bin i

thnh:

q: cng dng in hay mt dng in


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t:

- Vi: khi lng ring ca vt liu kh (kg/m3)

thtch vt kh (m3)

nhit dung ring ca vt liu m (j/kg)bn knh quy i ca vt liu (m)

- Khi nu bqua nhit lm qu nhit hi m, ta c:= (10)

- Vi : chun sRebinde c trng cho ng hc qu trnh sy.Biu thc (10) y l phng trnh c bn ca ng hc vsy.

2.5. ng nhit cp cho vt liu trong giai on sy gim tc (q2)Trong giai on sy gim tc, ng cong tc sy c dng ng

thng, nn tc sy trong giai on ny c biu din:

K: hstl, gi l hssy. Phthuc vo tc sy v tnh cht ca vt

liu m (l/s)

K: chnh l hsgc ca ng cong tc sy giai on sy gim tc

nn:

*

1

UUth

: hssy tng i, phthuc vo tnh cht vt liu m

Uth: m ti hn

U*: m cn bng

N: tc sy ng tc (kg m/(kg vt liu kh.s)

Tch phn phng trnh (11) ta nhn c:

)exp(*

*

NUU

UU

th

(13)

Hay logarit ha (8) ta c:

NUUUU th3,2

1)lg()lg( **

(14)


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Nh vy, nu bit c hssy K, c thxc nh c thi gian cn

thit thc hin giai on sy gim tc.

Hstng i sy tng i c xc nh bng thc nghim v c th

tnh gn ng nh sau:

oU

8,1 (15)

oU : m ban u ca vt liu

T ta c:

**

8,1

1U

UUU o

th

(16)

Thay (12) v (15) vo phng trnh (11), ta c:

oU

UUN

d

dU *8,1

(17)

Thay (17) vo (10) ta c:

o

ooU

UUNRbrRq

*

1 8,1)1( (18)

2.6. ng nhit cung cp cho vt liu trong giai on sy ngtc (

1q )

Trong giai on sy ng tc, ton blng nc cung cp tdng tc

nhn bng lng nhit bc hi m v nhit vt liu khng i nn:

rNRd

dUrRq oooo

1 (19)

2.7. ng trao i nhit (q(x))sy)1(

*8,1)(

2

1 RbU

UU

q

qxq

o

(20)


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Nh vy, theo biu thc (20), khi bit chun sRb stnh c cng

trao i nhit theo m ca vt liu.

2.8. ng cong sy v ng cong tc sythng cong tc sy thng cong sy

ng cong sy: l ng cong biu din sthay i ca i

m vt liu (U) theo thi gian sy ()

)(fU (21)

Dng ca ng cong sy:

Phthuc vo nhiu yu tnh lien kt gim v vt

liu, hnh dng kch thc, cu trc vt liu, phngtrnh v ch sy.

ng cong sy l hm ca qu trnh sy.V vy,

tuy ch v phng php sy khch nhau nhng dng

ng cong sy l tng tnhau.

ng cong tc sy: l ng

cong biu din mi quan hgia tc sy v

m (hm m) ca vt liu sy:

(22))(Ug

d

dU

Tbiu thc (21) v (22), r rng ng

cong tc sy l o hm ca ng cong sy.

2.9. c giai on ca qu trnh sy.iai on un nng vt liu (AB)

Giai on ny xy ra nhanh vi khong thi gian ngn khng ng

k.ton bnhit do dng tc nhn cp dng un nng vt liu tnhit

u ( o ) ln nhit bu t ( ut )


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Trong giai on ny lng m tch ra khng ng k, m vt liu

gim khng nhiu v tc sy nhanh ln vi tc cc i (N) thng giai

on ny bqua trong tnh ton.

iai on sy ng tc (BC)Trong giai on ny, tc khuch tn m ttrong lng vt liu ra

bmt ln hn tc bc hi m tbmt vt liu, nn bmt vt liu lun

bo ha m.

Ton blng nhit cung cp bc hi m bmt (m tdo) v

bmt bc hi l bmt ngoi ca vt liu khng i nn cc thng ssy

sau y skhng i: nhit bmt vt liu v tc sy; v m vt

liu gim nhanh.

Thi gian sy trong giai on ny l thi gian sy ng tc ( )c xc nh t:

constNd

dU 1

(23)

Nn tch phn (23) ta c:1

1N

UU tho (24)

Vi thU l m cui giai on sy ng tc.

iai on sy gim tc (CD)Do bc hi ht m bmt chcn m lin kt, nn bmt bc hi

bco hp li dn i su vo trong lng vt liu.

Tc khuch tn m trong vt liu chm lm gim tc chung.

Nhit ca vt liu tng dn tnhit bu t ut n nhit

dng tc nhn (t)nhit bu kh.

Trong vt liu xut hin 3 vng: m, bc hi v kh.


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Trong giai on ny, nu ng cong tc sy c dng ng thng

(hoc quy i sang ng thngN2=ax=b) th ta c thphn tch tnh

thi gian sy giai on sy gim tc ny )( 2 :

'

2

'

1

'

2 lnUU

UU

N

UU thth

(25)

Vi U: m cn bng, m kt thc giai on sy gim tc.

2.10. Thi gian sy vt liu.Thi gian sy vt liu c tnh bng tng thi gian ca 3 giai on

sy: t nng vt liuo. Sy ng tc

1v sy gim tc

2. C thbqua giai

on t nng vt liu, v giai on ny xy ra rt nhanh. Biu thc tnh thi

gian sy nh sau:

'

2

''

21 lg3.2

UU

UUUU

NN

UU thth

tho (26)

Vi U2m vt liu cui qu trnh sy. Tng ng vi 2 . U2> 'U v

thng c ly: (%)3

2'2 UU

3. S thit b:

1. Ca kh vo 5. Bung sy

2.Qut ly tm 6. Khy sy

3.Caloriphe 7. Ca ra kh thi


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4. Cn

Nhn xt:Bi sy cha c hon chnh v khng thi gian nn

cha sy ti khi lng khng i sn phm vn cha kh hon ton v th

lm sai snh hng n kt qutnh ton.CU HI CHUN B:

Cu 1:nh ngha qu trnh sy i lu?

Qu trnh sy din ra rt phc tp, c trng cho tnh khng thun nghch v

khng n nh. N din ra ng thi 4 qu trnh: truyn nhit cho vt liu,

dn m trong lng vt liu, chuyn pha v tch m vo mi trng xung

quanh.

Cu 2:Thno l truyn nhit v truyn m bng phng php i lu?

Truyn nhit l qu trnh phc tp xy ra ng thi bi 3 dng (3 phng

thc truyn nhit c bn) trao i nhit c bn:

- Trao i nhit bng dn nhit- Trao i nhit bng i lu- Trao i nhit bng bc xnhit

Cu 3:Nu cc giai on sy?

Gm c 3 giai on sy:

- Giai on un nng vt liu- Giai on sy ng tc- Giai on sy gim tcCu 4: C my qu trnh sy?

- Qu trnh sy c hi lu


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- Qu trnh sy c t nng trung gianCu 5:Ktn mt vi loi thit bsy?

- Thit bsy bng ti- Thit bsy tng si- Thit bsy kh ng (hay cn gi l thit bsy kh thi)- Thit bsy phun loi thng- Thit bsy bc x- i lu- Thit bsy thng hoa- Thit bsy in cao tnCu 6:Cc thng scn o trong qu trnh th nghim?

- Khi lng- Nhit bu kh- Bu t- Thi gian.Cu 7:Ni dung th nghim?

Tin hnh sy bnh trng 2 chca Caloriphe: 400C v 500C. t

vt liu vo bung sy, ghi nhn khi lng vt liu sau khi lm m (G1).

Sau c3 pht ghi nhn gi trcn v gi trnhit bu kh, bu t.

Tip tc n khi gi trkhi lng vt liu khng i trong vng 15 pht th

dng chth nghim ny v chuyn sang chth nghim khc.

Cu 8:Cch thc tin hnh th nghim?

Bc 1: Chun bth nghim:

- Xc nh khi lng vt liu kh ban u (G0) ca vt liu: Mca bung sy ra, t cn thn


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c gi trcn (G0)- Lm m vt liu:Sau khi cn xong, ly vt liu ra v nhng nhnhng (trnh rch vt liu)

vo chu nc. Chkhong 30 giy cho nc thm u, ly vt liu ln vro nc sau xp vo gi.

- Chun bng heo tay o thi gian.- Kim tra hthng: Lp li ca bung sy. Mht cc van ca hai ca kh vo ra Chm y nc vo bu t (pha sau hthng)

Bc 2: Khi ng hthng:

- Khi ng qut: bt cng tc ca qut ht dng tc nhn vo v thiqua caloriphe gia nhit dng tc nhn.

- Khi ng caloriphe, bt cng tc Caloriphe.- Ci t nhit cho Caloriphe nhit th nghim.

Bc 3: Tin hnh th nghim

Chhthng hot ng n nh khi: nhit ca Caloriphe t gi trmong

mun ( C021 ). Tin hnh sy vt liu nhit kho st.

o sliu trong chth nghim.- Cc sliu cn o: Khi lng, nhit bu kh, bu t v thi gian.- Cch c: Khi lng (gam) khi t gi vt liu sy, c shin thtrn cn. Nhit (0C) : Nhn nt tng ng cc vtr cn o v c strn ng

hhin s.

- Chuyn chth nghim:


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Mca bung sy, ly vt liu ra lm m tip (lp li nh ban u). Ci nhit Caloriphe gi trtip theo cho chsy mi. Chhthng hot ng n nh. Lp li trnh tnh chu.

Bc 4: Kt thc th nghim

- Tt cng tt ca in trCaloriphe.- Sau khi tt Caloriphe c 5 pht, tt qut cho Caloriphe ngui.Cu 9:Trnh by mc ch th nghim?

- Vn hnh c hthng thit bsy.- Tnh ton c cc thng ssy: tc sy ng tc, m ti hn,

m cn bng, thi gian sy ng tc v gim tc.

- Xy dng ng cong sy v ng cong tc sy da trn sliu thcnghim.

Cu 10:ng cong sy l g?

- L ng cong biu din s thay i ca m vt liu (U) theo thigian sy )(

- Ph thuc vo nhiu yu tnh lin kt gi m v vt liu, hnh dngkch thc; cu trc vt liu, phng php v chsy.

- ng cong sy l hm ca qu trnh syCu 11:ng cong tc sy l g?

- L ng cong biu din mi quan hgia tc sy v m ( hmm) ca vt liu sy

- ng cong tc sy l o hm ca ng cong sy.Cu 12:Phng trnh c bn ca ng hc qu trnh sy

d

dUrRRb

d

dUrR

dU

d

r

C

d

dRC

d

dUrRq OoOoOoOo

11


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Cu 13: Sy l g? Skhc nhau gia sy v c c?

Sy l qu trnh tch m ra khi vt liu bng phng php nhit.Nhit

c cung cp cho vt liu m bngdan nhit, i lu, bc xhay nng

lng in trng c tn scao.

Skhc nhau gia sy v c c

Sy :- L lm gim khi lng vt liu,tng bn v bo qun sn phm- Theo phng php dn nhit,bc x,nng lng in trng

C c:- L lm tng nng dung dch,tch rn ha tan dkt tinh hay tch

dung mi dang nguyn cht

- Theo phng php p sut kh quyn,chn khng v p sut dCu 14:Trnh by thi gian sy ca vt liu

Ta phi phthuc vo chsy ca vt liu m ta mi bit cthi gian sy ca vt liu. V vy i vi mi vt liu c cc chsy khc nhau th thi gian sy cng khc nhau.


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V: thtch nc lc thu c.

S: din tch bmt lc.

t: thi gian ly mu (ktlc bt u chy)

Tnh lng nc lc, lng b m, lng pha rn, lng pha lng.

Vh=V0+V1=Va+V

Gh=G0+G1=Ga+G

Trong : Vh, Gh: khi lng v thtch hn hp huyn ph em i lc.

V0, G0: thtch v khi lng cht rn kh.

V1, G1: thtch v khi lng nc lc nguyn cht.

Va,Ga: thtch v khlng b m.

V, G: thtch v khi lng nc lc cha nguyn cht

m ca b:a

aa

GGGW 0 (% kg m/kg vt liu t)

2.3.p sut lc2.3.1 Khi lc vi p sut khng i

.2

..2..2

00

2

S

VSRXrVP v

Trong : nht (kg/ms)

V: thtch nc lc (m3)

S: din tch bmt lc (m2)


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: thi gian lc c n nh trc

r0: trlc ring (1/m2), trlc lp b to thnh (1kg b kh/1m2

bmt)

X0= Va/V0: tsgia lng b m (m3/ lng nc lc (m3))

Rv: trlc vch ngn (1/m)

2.3.2 Lc vi tc khng i :W=const (km hiu qu)

.

....2

00

2

S

VSRXrVP v

(N/m2)

2.4.Vt ngn lc

Phi c tnh cht ph hp vi huyn ph, gm cc loi vi c an bng

cc loi sau: si bng len polypropylene, clorinaxeton, pvc, si thy tinh

chu axit

2.5. Cht trlc

Diatomit trng to t94% SiO2, bmt ring 20 m2

/g, bn axit, c sdng rng ri, to xp 93%.

Perolit: to tsn phm ni la, cc cht trlc khng c tan trong

dung dch lc.

3. My lc khung bn

3.1.Cu to

My lc khung bn gm c mt dy cc khung v bn cng kch thc

xp lin nhau, gia khung v bn c vi lc. Huyn ph c a vo rnh

di tc dng ca p sut ri vo khong trng ca khung. Cht lng qua vi


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lc sang cc rnh ca bn ri theo van ra ngoi. Cc ht rn c gili to

thnh b cha trong khung.

3.2. Qu trnh lc- trlc ca vi lc v b lc

Lc p a ti kt qul mt lp ht rn to thnh trn vi lc gm cc

mao qun ca b lc v vt ngn l chuyn ng dng cn phi c p sut

khc phc trlc ca vt ngn v trlc ca b lc. Trlc ca ng dn

khng ng k.

3.2.1. Trlc ca b lc

Phng trnh Kozeny-carman o hiu sut qua tng ht rn c dng chy

dng tnh hiu p sut qua lc.

....

2

2

00S

VXrPb

(1)

Trong : nht ca nc lc

V

VX a0 ; Va: thtch b lc; V: thtch nc lc.

S: din tch bmt lc.

: thi gian lc.

r0: trlc b lc.

Trlc b lc thay i ty theo tnh cht ca b lc.r0=r0. Ps(2)

r0: hng s

s: chschu nn;


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s=0 cho b lc khng nn c, thng thng s c gi trt0,1-1,0.

4.2.2.Trlc ca vi lc

VRP vv

.

(3)

Rv: trlc ca vt ngn lc

3.3.Phng trnh lc tng qut

Phng trnh (1) v (3) a ti Phng trnh vi phn ca qu trnh lc.

vRS

VXr

dSdV

00 ..

(4)

Tch phn vi P= const thu c: 00

2

00

2

..

.2

.

.2

Xr

SV

Xr

SRV v

(5)

tS

Vq :lng nc lc ring (m3/m2).

Phng trnh (5) c vit gn li nh sau: q2+2.C.q=K.

Trong :0000 ..

2;

. XrK

Xr

RC v

4 Nguyn l lc 1 cp


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S th nghim

Ch thch: 1. Khung khuy huyn ph 2. Bm huyn ph

3. Thit blc khung bn 4. p k

Nhn xt :

u im:Bmt lc ln.Dch lc trong v loi bc nm men.Tm c ththay thddng.Lc c cn bn.Khng cn ngi c chuyn mn cao.

Nhc im:Cn nhiu thi gian vsinh.Phi thay thtm theo chu k.Gi thnh tm cao.


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Dch chy nhiu, phn bkhng ng u.Phi tho khung bn khi cn gim p sut.

c phng php tng nng sut lc- Tng p lc lc.- Tng tc lc.- Gia nhit trong qu trnh lc gim nhtCc yu tnh hng ti qu trnh lc

- Vn tc lu cht lc.- p sut lc.- Lp b lc, tnh cht ca vch ngn.- Lp vi lc.- Hthng lc hay thit blc.- Trng thi ca cht lc, tnh cht ca huyn ph.- Nhit lcTRLI CU HI CHUN B

Cu 1:Mc ch ca bi th nghim

- Trnh by c cu to, nguyn l lm vic v u nhc im ca thit b

lc khung bn.

- Vn hnh c thit blc khung bn.

- Tnh ton c cc hslc da trn sliu thc nghim v a raphng trnh lc tng ng.

Cu 2:Lc sdng phn ring cc hn hp nhmt vt ngn xp.


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V d: Trong qu trnh sn sut bia, sau qu trnh nu dch nha, ngi ta thc

hin qu trnh lc nhit 76780C tch bb malt. Cn sau qu trnh

ln men ph, ngi ta tin hnh lc bia 2 40C nhm mc ch tch b

cn men v cc hp cht l lng dng keo.

Cu 3:Cc phng php to chnh lch p sut khi lc.

- Thay i chiu cao ct p sut thy tnh

- Dng bm hay my nn a huyn ph vo

- Bm chn khng ht

Cu 6:Phng trnh phn lc v nghim ca n:

- Phng trnh vi phn lc:

- Nghim caphng trnh lc:

0 0

vR

Cr X

0 0

2

. .

PK

r X

Cu 8:Nu cu to nguyn l hot ng, u nhc im v phm vi s

dng ca lc khung bn.- Cu to:

+ Khung khy huyn ph

+ Bm huyn ph

+ Thit blc khung bn

+ p k

- Nguyn l hot ng:

+ Huyn ph c a vo rnh ri vo khong rng ca khung di tc

dng ca p sut, cht lng chui qua vi lc sang cc rnh ri theo van ra

ngoi cn b bgili trong khung.


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+ Nc lc chy ra tbn qua hthng ng ng v ly ra ngoi. B c

gi li trn bmt vch ngn lc v c cha trong khung. Khi b trong

khung y th dng qu trnh lc tin hnh ra v tho b.

- u nhc im:+ u im: Bmt lc trn mt n vdin tch sn xut ln, ng lc ca

qu trnh lc ln, ddng kim tra qu trnh lm vic.

+ Nhc im: thao tc ch yu bng tay, ra b cha hon ho, vi lc

nhanh bn mn.

- Pham vi sdng: c ng dng nhiu trong cng nghthc phm, xl

mi trng.

Cu 9: Trnh ttin hnh th nghim

Pha 500g bt CaCO3vo 20 lt nc c dung dch huyn ph lc.

- ng van V1 v van V2.

- Cho dung dch pha vo bn cha.

- Bt cng tc my khuy, khuy u hn hp dung dch CaCO3.

- Mvan V3, V4, V5, V6.

- Mbm, iu chnh p sut bng V4 khi ng hp sut chmc mong

mun.

- ong dung dch lc u C1 v ghi nhn thtch trong mi thi gian 30

giy.

- Lm th nghim vi cc chp sut khc nhau.

Cu 10:Phng php sl sliu th nghim

Tnh nng sut ca qu trnh lc(Q)


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Q = V/

Tnh lng nc lc ring(q)

Q = V/S

Trong :

V: Thtch nc thu c

S: Din tch bmt lc

: Thi gian lc

- Xc nh cc hsC, K v0r

trong phng trnh lc

- Vthcho mi th nghim lc+ Vgin / q theo q

Cu 11:Cc i lng cn o

- Thi gian lc (s)

- Thtch nc lc thu c V(lt)

Cu 12:Ktn mt vi thit blc ngoi lc khung bn:

- Thit blc tay o

- Thit blc chn khng khung bn


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BI 3: TH NGHIM HP TH ( M)

1.Mc ch th nghim

Kho st c tnh ng lc hc lu cht v kh nng hot ng ca ctchmbng cch xc nh

nh hng ca vn tc dng kh v lng ln tn tht p sut ( gim

p) khi i qua ct.

S bin i ca h s ma st ct kh fcktheo chun s Reynolds (Re) ca

dng kh v suy ra cc h thc thc nghim.

S bin i ca tha s lin h gia gim p ca dng kh qua ct

kh v qua ct t theo vn tc dng lng.

2. s l thuyt

2.1 Khi nim qu trnh hp th(hp thu)Qu trnh hp thu l qu trnh truyn vn cu tvt cht tpha kh vo

pha lng. nu qu trnh xy ra theo chiu ngc li, ngha l truyn vn cuttpha lng sang pha kh, ta c qu trnh nhhp thu.

Mc ch ca qu trnh hp thu l ha tan chn lc mt scu t.

2.2 ng dng ca qu trnh hp thuCng nghthc phmCng nghha hcCng nghsinh hcKthut mi trngNgnh cng nghip du kh

3 hng php la chn dung mi hp thu

Khi la chn dung mi cho qu trnh hp thu ngi ta da vo cc

tnh cht sau:


25/57


26/57



Hnh 3.1

1. ch vn hnh thp mhun b Kim tra xem tn cc van trn s hng dn ng van VL6, m van VL 1 nc vo bn cha n mc

chy trn

ng tt c van VL1, VL3, VL4, VL5, VL6; m van kh VK2 vm ti a van VK1

o ct kh

Kim tra p k Kim tra mc nc lng y thp Kim tra li VK2 trng thi ng. VK1 phi m hon ton M in, qut


27/57



M t t VK2 chnh con i ln 2 fit3/pht c p k M VK2 hon ton v ng VK1o ct t Kim tra li VK2 phi trng thi ng, VK1 phi m hon ton M qut kh Qk, m VK2 v tr 1fit3/pht thng kh VL2 v VL4 hon ton M bm, kim tra nc trong bn c bm hon lu cha M VL3 cho nc vo ct n khi khng c bt kh, ng thi

canh chng x VL5, duy tr mc nc O

Chnh VL3 v 4 fit3/pht(lit/p); chnh VK2, VK1 a con iln 2; 2,5; 3; 3,5; 4; 4,5 c p k . M li VK1, ng bt VK2

v v tr 1 fit3/p

Chnh VL3 v 3 (lit/p); 6(lit/p); 7(lit/p); 8(lit/p); 9 (lit/p); Ghi li s liu o c.

2. hn xt da vo thSau bi th nghim gip ta bit cch vn hnh thp hp thu, bit c

nh hng ca vn tc dng kh v lng ln tn tht p sut ( gim p) khi i

qua ct thng qua cc th ct t, ct kh

Thng qua xl sliu sgip sinh vin nhn bit c sai sl thuyt

v thc t.


28/57



BI 4: TH NGHIM TRUYN NHIT NG KP

c ch th nghim

- Lm quen vi thit btruyn nhit ng lng ng, cc dng conhit

v lu lng lu cht.

- Xc nh hstruyn nhit trong qu trnh truyn nhit gia hai dng

lnh v nng qua vch kim loi cc chdchy khc nhau.

- Thit lp cn bng nhit lng.

s l thuyt

2.1 Cc khi nim

Truyn nhit

Truyn nhit l mt qu trnh phc tp xy ra ng thi 3 dng trao i

nhit: trao i nhit bng dn nhit, trao i nhit bng i lu nhit v trao

i nhit bng bc xnhit.

Chiu qu trnh

Trong tnhin qu trnh truyn nhit chxy ra theo mt chiu tni

c nhit cao ti ni c nhit thp.

Cht ti nhit

Cht ti nhit l cht mang nhit tni ny ti mi trng khc theo quy

lut tnhin.

Truyn nhit trc tip

Truyn nhit trc tip l qu trnh truyn nhit m cht ti nhit tip xc

trc tip vi vt liu.


29/57



Truyn nhit gin tip

Truyn nhit gin tip lqu trnh truyn nhit m cht ti nhit khng

tip xc trc tip vi vt liu m thng qua vt ngn.

Truyn nhit n nh

Truyn nhit n nh l qu trnh truyn nhit m nhit chthay i

theo khng gian m khng thay i theo thi gian.

Truyn nhit khng n nh

Truyn nhit khng n nh l qu trnh truyn nhit m nhit thayi ctheo khng gian v thi gian.

rng nhit

Trng nhit c trng cho nng ca vt l nhit (toC, toK). Tp

hp tt cnhng gi trnhit ca vt hoc mi tng gi l trng nhit.

Nhit trng n nh

Nhit trng n nh l nhit trng m nhit chthay i theo khng

gian m chthay i theo thi gian. t=f(x,y,z)

Nhit trng khng n nh

Nhit trng khng n nh l nhit trng m nhit thay i theo c

khng gian v thi gian. t=f(x,y,z,t)


30/57



Mt ng nhit

Mt ng nhit l tp hp cc im c nhit bng nhau. Qu trnh dn

nhit khng xy ra trn mt mt ng nhit, m chdn nhit tmt ng

nhit ny n mt ng nhit kia.

2.2 Cc qu trnh truyn nhit

Trong thc tqu trnh truyn nhit din ra theo 3 phng thc truyn

nhit c bn sau.

Dn nhit

Dn nhit l struyn nhit nng tni c nhit cao n ni c nhit thp. do struyn ng nng hoc dao ng va chm vo nhau, nhng

khng c schuyn ri vtr gia cc phn tvt cht. dn nhit chxy ra

khi truyn nhit ca cc cht rn hoc truyn nhit ca cht lng, cht kh

ng yn hay chuyn ng dng.

nh lut FourienXt trn mt mt phng c din tch F c dng nhit dn qua theo

phng vung gc vi mt phng, nh lut Fourien pht biu nh sau:

Mt dng nhit truyn qua bng phng thc dn nhit theo phng

quy nh t l thun vi din tch vung gc vi Phng truyn nhit v

gradian nhit theo phng y.

xTFQx (W)

x

T

F

Qq xx

(W/m2)

Qx: dng nhit truyn qua din tch F (j/s)


31/57



qx: mt dng nhit (W/m2)

F: din tch bmt truyn nhit vung gc vi phng x (m2)

: hsdn nhit W/m.

Thc nghim chng t l mt thng s vt l biu din khnng dn

nhit ca vt liu.

H sdn nhit ph thuc vo p sut, nhit , vt liu, cu trc vt

liu.

Hsdn nhit ca cht kh trong khong 0,006 0,6 (W/m.)

Hsdn nhit ca cht kh trong khong 0,007 0,7 (W/m.)

Hsdn nhit ca cht rn phthuc vo kt cu, xp v m ca

vt liu.

T nh lut Fourien c bn ngi ta a ra cc dng phng trnh

truyn nhit cho cc trng hp cth.

y ta chnu trng hp dn nhit n nh qua ng

Dn nhit n nh qua ng

Nghin cu qu trnh dn nhit qua vch tr (ng) nhit b mt

vch trong t1, nhit vch ngoi t2khng thay i. vt liu c hsdn

nhit khng i.

Ta c phng trnh dn nhit nh sau:

1

2

2121

1

2 ln2

1ln

..2

d

d

L

tttt

d

d

LQ

(W)


32/57



L: chiu di ca ng (m)

d1, d2: ng knh trong v ngoi ca ng (m)

Cn 212 dd

(m)

V din tch bmt trung bnh:

1

2

21

ln

)(

d

d

LddF

(m2)

Tsd2/d1 2 th F tnh bng cng thc sau:

2

)( 21 LddF

(m2)

thun tin cho vic tnh ton ta tnh

1

2

21

ln2

1

d

d

tt

L

Qq

(w/m)

Nhiu lp

Vi tng hnh ng nhiu lp vt liu khc nhau

i

in

i

n

d

d

tt

L

Qq

1

1

11

ln2

1

n: slp

t1: nhit vch trong (oC)

tn+1: nhit vch ngoi thn+1 (oC)


33/57



i lu nhit

Nhit i lu l struyn nhit m cc phn tlng hoc kh nhn nhit

ri i chcho nhau; si chdo chnh lch khi lng ring hay do cc

tc ng c hc nh: bm, khuy.

Qu trnh ta nhit i lu xy ra khi c s trao i nhit gia cht

lng, cht kh v bmt rn.

nh lut Newtontnh nhit i lu ngi ta dng cng thc Newton

Q= .F.(tr-tv) (w)

Trong : hsta nhit (W/m.) phthuc vo rt nhiu thng s

=f(tv,tf, , , cp, , ,l)

tf: nhit lu cht

tv: nhit vch

: tc truyn nhit ca cht lng

l: kch thc bmt troa i nhit

q= (tr-tv) (W/m2)

tnh ton c phng trnh trn ta cn phi xc nh c

2.3 Cc chun s

V qu trnh ta nhit i lu phthuc vo nhiu chun sdo mun xc

nh ta cn tnh cc chun ssau:


34/57



Chun sNusselt:r

Nu

. Chun sPrandtl:

a

Pr

Chun sReynolds:

.Re Chun sGrashof:

2

3...

tgGr

: vn tc chuyn ng ca lu cht (m/s)

a: hsdn nhit

.pca (m2/s)

cp: nhit dung ring ng p (j/kg.oC)

g: gia tc trng trng (m/s2

)

l: kch thc hnh hc (c thl ng knh nu l ng) (m)

t: k hiu nhit vch v nhit lu cht (oC)

:hsgin nthtch (1/oK; 1/oC) vi cht kh =1/T

4 c phng trnh thc nghim cho cc loi lu cht chuyn ng

tnh ngi ta dng chun sNu v trong tng trng hp c

thth Nu c biu thc ring

Ngoi ra ngi ta tnh trc mt s trng hp c th, ta c th tra

bng cho tng trng hp y

2.5 Cc kiu truyn nhit trong thit bvng

Kiu xui chiu: 2 dng lu cht lnh v nng chuyn ng cngchiu. Khi btr kiu ny th hiu qutruyn nhit u vo l rt cao v

u ra l thp.


35/57



Kiu ngc chiu:2 dng lu cht lnh v nng chuyn ng ngcchiu, kiu btr ny thng c dng, strao i nhit c phn bu

trn khp chiu di ca thit b.

2.6. Tchc dng chy trong thit bvng

T chc dng chy phi m bo iu kin: hiu ququ trnh trao

i nhit l cao nht. trong gm: dng nng v dng lnh.

Dng nng v dng lnh c thbtr bn trong hay bn ngoi vng

dng lu cht cng chiu hay ngc chiu.

2.7. Nhit ra ca cc dng chyTrng hp xui chiu: 2 u thit bnhit nng ra ln hn lnh ra

3 nh ton th nghim

Phng trnh cn bng nhit lng cho 2 dng lu cht nng v lnh c

dng

Q= GN

.CN

(tNV

-tNR

)=GL.C

L(t

LR-t

LV)

Trong

GN, GL: lu lng khi lng ca dng nng v dng lnh (kg/s)

CN, CL: nhit dung ring ng p ca nc nng v nc lnh

(J/kg.)

tNV, tNR: nhit vo, ra ca dng nng (o

C)

tLV, tLR: nhit vo, ra ca dng lnh (oC)

Qu trnh truyn nhit c biu din bng phng trnh sau:


36/57



Q= KL. tlog.L

Trong : Q: nhit lng trao i (W hoc j/s)

KL: hstruyn nhit di (W/m.)

t log: hiu nhit logarit chai dng lu cht (oC)

L: chiu di ng, bi th nghim ny ta ly L=1050mm

Hiu nhit ca 2 lu cht

min

ma x

minma x

lnt

t

tttlog

Hstruyn nhit di KL:

ngb

b

tr

ng

inoxtr

L

dd

r

d

d

d

K

.

1ln.

2

1

.

1

21

Trong :

dtr, dng: ng knh trong v ng knh ngoi ca ng truyn nhit

(m).

inox: hsdn nhit ca kim loi chto ng (w/m.)

1, 2: h s cp nhit ca dng nc nng, dng nc lnh

(w/m2.)

rb: hsnhit ca cn bn (m2./w)

db: ng knh lp bn (m)

KL: hstruyn nhit di (w/m.)

H s cp nhit 1, 2gia vch ngn v cc dng lu cht c

tnh tchun sNusselt (Nu)


37/57



Phng trnh tng qut ca chun sNusselt l:

PL

nm

t

ANu ..

Pr

Pr.Pr.Re.

25,0

Trong :

Cc hs: A, n, m, L, P l cc hsthc nghim phthuc cc yu

tsau:

Chchy ca cc dng lu cht .

Stng quan gia cc dng chy vbmt truyn nhit.c im ca bmt truyn nhit (nhm, hnh dng ,)

Ta c cc phng trnh Nusselt cho dng chy ngang ng nh sau:

Khi 5 Re 103:25,0

38,05,0

Pr

Pr.Pr.Re.5,0

t

Nu

Khi 103 Re 2.105:25,0

38,06,0

Pr

Pr.Pr.Re.25,0

t

Nu

Khi 2.105 Re 2.106:25,0

37,08,0

Pr

Pr.Pr.Re.023,0

t

Nu

Ta c phng trnh tnh Nusselt cho chchy dc theo thn ng:

Chchy mng Re 2320

L

t

GrNu ..Pr

Pr..Pr.Re.15,0

25,0

1,043,033,0

Chchy chuyn tip 2320 Re 10000:


38/57



Lt

CNu .Pr

Pr.Pr.

25,0

43,0

Chchy ri Re 10000:

P

t

Nu .Pr

Pr.Pr.Re.021,0

25,0

43,08,0

Trong gi trC phthuc Re theo bng sau:

Gi trL phthuc vo tlL/d khi Re 10000

L/d 1,0 2,0 5,0 10,0 15,0 29,0 30,0 40,0 50,

0

L 1,9 1,7 1,44 1,28 1,18 1,13 1,05 1,02 1,00

Khi Re 10000 th hsPphthuc vo Re v L/d nh sau:

L/d

Re

10,0 20,0 30,0 40,0 50

1.104 1,23 1,13 1,07 1,03 1,00

2.104 1,18 1,10 1,05 1,02 1,00

5.104 1,13 1,08 1,04 1,02 1,001.105 1,10 1,06 1,03 1,02 1,00

1.106 1,05 1,03 1,02 1,01 1,00

Re 2100 2200 2300 2400 2500

C 1,9 2,2 3,3 3,8 4,4

Re 3000 4000 5000 6000 8000 10000

C 6,0 10,3 15,5 19,5 27,0 33,0


39/57



Chun sGrashof (Gr)Chun sGrashof c trng cho quan hgia lc ma st phn tv

lc ko do ttrng khc nhau, nhng im c nhit khng ging nhau

trong cng mt dng lu cht (nc).

2

23

2

3.......

tdgtdgGr tdtd

Trong Gr: chun sGrashof

: nht ng hc ca lu cht (m2/s)

dtd: ng knh tng ng ca tit din dng chy (m)

: khi lng ring ca lu cht (nc), (kg/m3)

: nht ng lc hc ca nc (N.S/m2).

t: hiu nhit gia lu cht v thnh ng, trong bi th nghim nyta ly t=6oC

: hsgin nthtch (phthuc vo nhit ), (1/oC)

T(oC) 0 20 40 60 80 100 120

(1/oC) -0,6.10-

4

2,1.10-4 3,9.10-4 5,3.10-4 6,3.10-4 7,5.10-4 8,6.10-4

2

232 ..).(6)./(81,9

tdo dCsm

Gr


40/57



Thit bth nghim: Hthng thit bth nghim c cc thit bthnhphn sau:

Ni un nc nng c gia cng bng thp khng gc dng lng tr

ng vi ng knh D=395mm, chiu cao ni l H=500mm

Thnh ni c lp bo n dy 30mm, trong ni c hai in trgia nhit

un si nc.

Mt bm nc nng c cng sut 0,5 HP dng bm nc nng tni

un hthng trao i nhit.

Hp iu khin hthng thit b.

ng kp chy ngang l loi ng lng ng m lu cht lnh chy ngang

mt ngoi ca ng trong .

ng kp chy dc l loi ng lng ng n gin, lu cht nng chy dc

mt trong ca ng trong v lu cht lnh chy dc trong khong khng gian

gia hai ng.

Mt lu lng kdng phao dng o lu lng ca nc nng v

nc lnh.

Loi ng Kch thc

ng trong (mm)

Kch thc

ng ngoi (mm)

Chiu di

(mm)

Chy dc 18/22 30/34 1050

Chy ngang 18/22 30/34 1050


41/57



Bi 5: TH NGHIM M T

1. Mc ch th nghim

Kho st slu chuyn ca nc nhit phng ths nghim trong h

thng thit bmng ng vi nhiu ng ng c ng knh khc nhau, trn

ng ng c lp ventury, mng chn, co ni, van kim, bm, ng o ct p.

2. sl thuyt2.1.nh hc lu cht

Phng trnh thy tnh :

Khi khi lng ring thay i khng ng kta xem =const, phng trnh

thy tnh c dng:

p+ .g.z= const (1.1)

p: p sut ti im ang xt

g: gia tc trng trng

z: chu cao ca im ang xt so vi gc ta ta chn


42/57



Pht biu: vi mt im bt k trong lng lu cht u tun theophng

trnh (1.1)

Xt mt im B bt k trong lng lu cht th ti B p sut, KLR quan h

theo pt:

pB+ .g.zB= const

V ti im A no th p sut, KLR cng c pt:

pA+ .g.zA= const

Lc : pB+ .g.zB=pA+ .g.zA

pBpA= .g.(zA-zB)

pAB= .g.hAB (1.2)

pAB: l chnh p gia vtr A v B trong lng cht lng

T(1.2) ta thy khi zA=zBth pAB= 0 hay pB=pA

p sut thy tnh ti mt im trong lng cht lng

pA-p0= .h (kg/m.s2= N/m2)

Trong :

= .g : tr ng lng ring ca cht lng (kg/m2.s2)

: l khi lng ring ca cht lng (kg/m3)

h: chiu cao tA n mt thong (m)

p0: p sut trn mt thong


43/57



i tm cht lng (du, ru...) so vi mH2O

pdu ==

pcht lng==

2.2. o p sut

o p sut kh quynp sut kh quyn c tnh theo p sut tuyt i

Pkq= .g.h (N/m2)

Trong :

: l khi lng ring ca thy ngn (kg/m3)

g: gia tc trng trng (m/s2)

h: chiu cao ct thy ngn (m)

o p sut cht khTrong bnh ang c p sut tuyt i l p, p sut d trong bnh so vi

kh quyn l:

pd= pp0= .g.hL(N/m2

): Khi lng ring ca cht lng vo manometter (kg/m3)

hL: chiu cao ct cht lng chnh trong manometer (m)

o p sut chn khng ca kh trong bnh ta dng Vacumeter

o p sut chn khngTrong bnh ang c p sut tuyt i l p, p sut chn khng trog bnh

l:pck= p0p= .g.hL

o p sut lu cht ang chuyn ngp ko chnh

Trng hp 1:h=h1= (zA+ (zB+ ) (m)


44/57



Trng hp 2: h=h1. (m)

h: l chnh p sut gia hai im A,B

2.3. Chchy trong ng

- Chun Renolds :Re= =

d: ng knh ng trong, hoc ng knh tng ng ca knh

(m)

: vn tc dng chy (m/s)

: nht ng lc hc ca lu cht (N.s/m2; kg/m.s)

: nht ng hc (m2

/s)Nu Re 2300 th chchy l chy tng

Nu Re > 2300 th chchy l chy ri

2.4. Trlc v ma st

Khi chuyn ng trong ng lu cht tip xc vi ng ng dn slm cn

trtc chy ca lu cht. Mt khc khi i qua nhng chquanh co, khp

ni ng, nhng chthu hp, phnh to...cht lng bcn trlm vn tc chychm li v p sut cng gim.

-Cc k hiu:: hstn tht dc ng hoc hsma st

: hstn tht cc b

- Tn tht dc ng c tnh theo cng thc Darcy:Tn tht dc ng gy ra bi chiu di ng ng :

hL= . (m c.lng)

Nu ng ng trn


45/57



hL= . (m c.lng)

Trong :

L: chiu di ng

v: vn tc lu cht trong ng (m/s)D: ng knh ng trn

R: bn knh ng trn hoc bn knh thy lc

R= S/ (m)

S: Tit din mt ct t (m2)

: chu vi t

Chy tng Re 2300: =

Chy ri : = f(

Nu 3000 < Re < 100000 : =

Re > 100000 : =

-Tn tht cc bTn tht cc bgy ra bi cc im co, ngoc, t thu, t m, cc

van...

hcb=

v: vn tc lu cht trong ng (m/s)

2.5. hng trnh becnuli cho cht lng ng yn v chuyn ng

Phng trnh becnuli cho mt ct A-A v B-B l:

zA +

Phng trnh becnuli c dng :z1 + = z2 + + H (m c.lng)

: hshiu chnh ng nng

H: mt nng ( tn tht nng lng hoc ct p) = hL+ hCB


46/57



z: vnng (m)

: p nng (m)

: ng nng (m)

v1, v2: vn tc lu cht ti cc mt ct2.6. Tn tht nng lng dng chy

- Tn tht nng lng dc ng ng:- Khi dng lu cht chy dc trong ng ng thng th c smt mt nng

lng do lu cht ma st vi thnh ng. Tn tht nng lng ny c tnh

ton nh sau:

hd= . ta li c : hd=Trong :

: hsma st phthuc vo Re v nhm ca ng

L: Chiu di ng thng (m)

d: kch thc ng (m)

: tc chy ca lu cht (m/s)

P: Tn tht p sut (N/m2)Tn nng lng cc b:

Khi dng lu cht chy qua van, bt thu, t m, bi hng t ngt

khi qua co th dng lu cht bmt mt nng lng. Tn tht nng lng

ny gi l tn tht nng lng cc bv c tnh ton nh sau:

hCB= . trong : hstrlc cc b

- ng ventury l ng c tit din trn tht dn v sau tng dntrli kch thc ban u

- Mng chn l a kim loi mng co ng knh bng vi ngknh trong ca ng t vung gc vi trc ng, trn a c gia cng mt l

hnh trn, tm lnm trn trc ng


47/57



- ng ventury v mng chn mc ni tip vi ng dn lu chtlm cho dng lu cht khi qua n btn tht p sut, thay i tc chy.

- Phng trnh becnuli gia hai mt ct t:z1+ + = z2+ + + h

= dv/d=dm/d

Trong :

- d: l ng knh trong ca tit din ng. (m)- dv,dm: l ng knh lventury hay mng chn. (m)

Gi hsco tht dng ca ventury v mng chn ln lt l CV v Cm.

- K : l hng si vi mt loi ng knh ng xc nh.Ta c cng thc tnh lu lng chy qua ng.

Q = C.K.

K =

2.7. Chiu di tng ng ca van

L chiu di ca ng ng c tn tht nng lng dc ng bng vi tntht nng lng cc bca van.

hCB= .LE.2/(2.g.d)

- Trong :LEl chiu di tng ng ca van (m

Nhn xt biu

Qua kt quth nghim ta thy, tn tht p sut cng ln khi m titdin ng cng nh, lc ny cht lng chim y ng ti a v trlc ma s t

gy ra cng ln nhiu.


48/57



ng ch l, i vi trng hp cht lng chy qua cht thu th

tn tht p sut tng ln ng k, do lc ny, tit din ng bt ngbthu hp.

Qua bi th nghim trn gip ta thit lp dng lu cht chy qua thit

bbng cch ng mcc van, chnh lu lng bng cc van iu khin, o

gim p sut thy tnh bng p kct nc.

Xc nh tn tht p sut ca dng chy qua cc ventury v mng

chn.

Thit lp mi quan hgia:

Tn tht p sut ct p ca ventury v mng chn vi lu lng chy Hsco tht ca ventury v mng chn vi chdng chy Hsma st ca ng ng vi chdng chy Chiu di tng dng ca van vi chchy

Cth:

Th nghim 1Thit lp mi quan hgia tn tht ct p ca dng chy qua venturyv mng chn vi lu lng thtch. Biu din quan hny trn gin

Th nghim 2o gi trtn tht p sut ca dng chy qua cc on ng thng c

kch thc 32/34 v mng chn. Xc nh hsma st trn ng

ng, nhm ca ng. Biu din quan hgia hsma st v ch

dng chy ln gin .

Th nghim 3o gi trtn thp p sut ca dng chy qua cc on ng thng c

kch tht 25/27 v mng chn. Xc nh h sma st trn ng


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dng chy ln gin .

Th nghim 4o gi trtn thp p sut ca dng chy qua cc on ng thng c

kch tht 14/16 v mng chn. Xc nh h sma st trn ng


dng chy ln gin .

Th nghim 5Xc nh chiu di tng dng ca van 9.

6 C

1. Mc tiu th nghim

Trnh by c cu to, nguyn l lm vic v u nhc im thit bc

c gin on 1 ni, hot ng trong iu kin chn khng.

Vn hnh c hthng c c.

Tnh ton c cn bng vt cht, cn bng nng lng v cc i lng

c trng cho qu trnh c c.

2. sl thuyt

2.1. Cc khi nim trong c c

Khi nim c c


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C c l qu trnh lm tng nng ca dung dch bng cch tch mt

phn dung mi nhit si, dung mi tch ra khi dung dch bay ln gi l

hi th.

Mc ch ca qu trnh c c- Lm tng nng ca cht ha tan trong dung dch.- Tch cht rn ha tan dng rn (kt tinh).- Tch dung mi dng nguyn cht (ct nc)

2.2. c phng php c c

C c p sut kh quyn:l phng php n gin nhng khng tinht.

C c p sut chn khng: dng cho cc dung dch c nhit sicao, dphn hy v nhit,

C c p sut d:dng cho cc dung dch hng phn hy nhit cao, sdng hi thcho cc qu trnh khc.

2.3. Cn bng vt liu trong hthng c c 1 ni

Xt hthng mt ni

Trong

G- khi lng nguyn liu, [kg]; kg/s

Gc- khi lng sn phm. [kg]; kg/s

W- lng hi th, [kg]; m/s

x- nng cht kh trong nguyn liu, [phn khi lng]

xc- nng cht kh trong sn phm, [phn khi lng]

Theo nh lut bo ton vt cht.


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Bo ton khi lng G=Gc+W

Bo ton cht kh G.x=Gc.xc

Gii ra ta c

Lng hi th:

c

x

xGW 1

Nng sn phm

cuiWG

xG

G

xGx

c

c

..

2.4. Cn bng nhit lng

K hiu t: nhit nguyn liu. [].

tc: nhit sn phm, [].

tn: nhit nc ngng, []. c: nhit dung ring nguyn liu, [J/kg.]. cc: nhit dung ring sn phm, [J/kg.]. cn: nhit dung ring nc ngng, [J/kg.]. i: hm nhit trong hi t, [J/kg]. i: hm nhit trong hi th, [J/kg]. Qc: tn tht nhit c c, [J]; Qc=0,01. q.Gc. q: tn tht nhit c c ring, [L/kg]. Qmt: tn tht nhit ra mi trng, [J].

Theo nh lut bo ton nhit

Qv= Qr


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G.c.t+D.i=Gc.cc.tc+W.i+D.cn.tn+Qc+Qmt

Rt ra Lng hi t tiu tnnn

mtcccc

tci

QQtcGtcGiWD

.

....'.

Trong qu trnh tnh ton nhit c thxem cc c

Tnh bmt truyn nhitQ=K.F. . thi=D.(i-cn.tn)

Trong

Q: lng nhit truyn, [J].

K: hstruyn nhit, [W/m2

.].

F: Din tch bmt truyn nhit

: thi gian c c, [s].

thi: hiu snhit hu ch, [].

Rt ra bmt truyn nhithi

nn

tK

tciDF

.

)..( , [m].

Thit bth nghim

Dung dch c c c theo tng m, nhp liu mt ln tthng cha dung

dch u. dung dch si trong bung bc hi do nhit truyn tnc nng bn

vngoi. Hi thbc ln tdung dch si c dn qua thit bngng tng

xon ngng tthu hi v nh lng. Mt bm chn khng loi vng nc

c sdng to chn khng cho hthng.

Hthng c c gm cc thit bchnh sau:

- Ni c c 2 vcnh khuy.


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- My khuy trn.- Thit bngng tng xon.- Bnh cha nc ngng.- Bm chn khng loi vng nc.- p ko chn khng.- Nhit kin t.- Hthng in.- X nha cha dung dch u.

Ni c c 2 v

Ni cha dung dch ng c ng knh D=250mm, cao H=500mm, b

dy = 5mm.

Ni c chto bng thp khng gAISI304.

Thit bngng tng xon

ng xon c ng knh 16 c qun thnh cc vng xon c ng

knh D= 150mm. ng xon cj gia cng bng thp khng gAISI304.

m chn khng

Hthng sdng bm chn khng loi vng nc 1HP.

TRLI CU HI CHUN B:Cu 1:Mc tiu bi th nghim:

- Trnh by c cu to, nguyn l lm vic v u nhc im thit bcc gin on mt ni, hot ng trong iu kin chn khng.

- Vn hnh c hthng c c.


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- Tnh ton c cn bng vt cht, cn bng nng lng v cc i lngc trng cho qu trnh c c.

Cu 2:C c l g?

C c: l qu trnh lm tng nng ca dung dch bng cch tch mt

phn dung mi nhit si, dung mi tch ra khi dung dch bay ln gi

l hi th.

Cu 3:Trnh by mc ch ca qu trnh c c:

- Lm tng nng ca cc cht ha tan trong dung dch.- Tch cht rn ha tan dng rn /kt tinh).- Tch dung mi dng nguyn cht / ct nc).Cu 4:Cc bc chun btin hnh th nghim:

- Tm hiu hthng thit b, cc van v tc dng ca n.- Tm hiu vi thit bo nhit , cc vtr o v cch iu chnh cng

tc o nhit .

- Tm hiu vi thit bo nng cht kh/ Brix k).- Xc nh cc i lng cn o.- Chun bdung dch ng em c dc.- Chun bbng sliu th nghim.Cu 5:Bx l g? Cc phng php o nng ca dung dch ng?

Brix: biu thtl% khi lng cc cht ha tan so vi nc ma hay

dung dch ung.

Cc phng php o nng ca dung dch ng:

Phng php ttrng Phng php pha long


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Phng php chit quangCu 6:Cc bc tin hnh th nghim.

Chy nc nng. C dc dung dch. Vsinh thit b.Cu 7:Tnh p sut tuyt i da vo chsp k?

=

M ththng thit bc c dng trong th nghim:

Ni c c hai ve c cnh khuy. Thit bngng tc ng xon. Bnh cha nc ngng. Bm chn khng. p ko chn khng. Hthng in.Cu 8:M ththng thit bc c dng trong th nghim:

Ni c c hai ve c cnh khuy. Thit bngng tc ng xon. Bnh cha nc ngng. Bm chn khng. p ko chn khng. Hthng in.Cu 9:Cc dng cu to thit bc c khc nhau:

Thit bc c c ng tun hon trung tm. Thit bc c tun hon cng bc.


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Thit bc c c bung t ngoi. Thit bc c loi mng.Cu 10:Cc thng scn o:

Nhit nc vo, ra. Nhit hi th. Nhit dung dch. Nhit nc ngoi v. Khi lng nguyn liu. Thi gian.Cu 11:Cn bng nng lng cho qu trnh c c:

GCt+ D.ic= GcCctc+ DCntD+ W.iW+ Qtt

Cu 12: Cn bng vt cht ca qu trnh c c:

G= Gc+ W

G.x= Gc.xc

Cu 13:u nhc im ca phng php c c gin on:

- u im: Gic cht lng, tnh cht sn phm, hay cc cu tdbay hi. Nhp liu v tho sn phm n gin, khng cn n nh lu lng. Thao tc ddng. C thc c n cc nng khc nhau. Khng cn phi gia nhit ban u cho dung dch. Cu to n gin, gi thnh thp.

- Nhc im:


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Qu trnh khng n nh, tnh cht ha l ca dung dch thay i lin tctheo nng , thi gian.

Nhit hi ththp, khng dng c cho mc ch khc.Kh gic chn khng trong thit b.

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