da kts say_nam

8/8/2019 DA KTS SAY_NAM

1/28

NGUYN DANH NAM _ MY & TBNL2 K4

N MN HC K THUT SY

TI:

Thit k thit b sy hm sy khoai ty ct lt, nng sut 200 tn/nm.

iu kin thit k:

- m ban u 80%, m sn phm kh 8%.

- Khng kh bn ngoi 200C v m 85%.

- Ch sy: nhit tc nhn vo 700C, thi gian sy trong 15 gi.

- Nng lng: hi nc c p sut 5 bar.

n mn hc: K THUT SY 1


2/28


LI NI U

K thut ch bin v bo qun thc phm hin nay ang ngy cng c

hng pht trin mnh. Trong k thut bo qun bng phng php sy k phm l mt trong nhng phng php ang c p dng rt ph bin vqu hin nay. V d nh nhn sy kh, chui sy kh, ng sy, khoai ty sy

Nhm trang b cho k s ngnh Nhit trc khi ra trng nhng kin c bn nht v k thut sy, sinh vin ca Vin KH&CN Nhit Lnh, trong ctrnh o to, c hc mn k thut sy v lm n mn hc k thu c mt ci nhn trc quan v thc t hn, trong qu trnh lm n, emc giao ti c th l thit k h thng sy hm dng sy khoai ty vnng sut 200 tn/nm.Bn n gm cc phn chnh nh sau:

Chng I: Tng quan v h thng sy hm

Chng II: Tnh ton qu trnh sy l thuyt

Chng III: Xc nh kch thc c bn ca thit b sy

Chng IV: Tnh ton qu trnh sy thc

Chng V: Tnh chn calorifer v cc thit b phEm xin chn thnh cm n cc thy c gio trong b mn k thut nh

thy gioNGUYN C QUANG gip em hon thnh n ny. Tuy nhin,do hn ch v mt kin thc l thuyt v thc t nn bn n ny s khnkhi nhng sai st, em rt mong nhn c s ch dn v gp ca cc thcng nh cc bn.

Em xin chn thnh cm n !

Sinh vin thc hinNguyn Danh Nam



3/28


MC LC

LI NI U ........................................................................................................2

MC LC ...............................................................................................................

Chng I : TNG QUAN V H THNG SY HM .......................................5

I. H thng sy hm ...........................................................................................5

II. H thng sy hm sy khoai ty .............................................................

Chng II: TNH TON QU TRNH SY L THUYT .................................8

I. Tnh nng sut sy trong mt gi ...................................................................8II. Tnh lng m bc hi trong mt gi ..........................................................

III. Chn ch sy ..........................................................................................

IV. Tnh ton qu trnh sy l thuyt ..................................................................9

Chng III: XC NH KCH THC C BN .............................................

CA THIT B SY .............................................................................................13

I. Xc nh tit din hm sy ............................................................................

II. Thit b Chuyn ti ........................................................................................14

III. Kch thc tng bao v trn hm sy .......................................................

Chng IV: TNH TON QU TRNH SY THC ..........................................

I. Tn tht nhit do vt liu sy mang i qV ..................................................17

II. Tn tht do thit b chuyn ti mang ra khi hm ......................................

III. Tn tht ra mi trng .................................................................................18

IV. Tng tn tht nhit trong qu trnh sy thc ..............................................21

Chng V: TNH CHN CALORIFER V THIT B PH ...............................23



4/28


I. Tnh chn calorifer ..........................................................................................

II. Tnh ton kh ng v chn qut gi ............................................................

TI LIU THAM KHO .......................................................................................



5/28


Chng I : TNG QUAN V H THNG SY HM

I. H thng sy hmCng nh h thng sy bung, h thng sy hm l mt trong nhn

thng sy i lu ph bin nht. Nhng khc vi h thng sy bung, h thhm c th sy lin tc hoc bn lin tc vi nng sut ln v phng php ttrao i nhit ch c th i lu cng bc, ngha l bt buc phi dng qut.

Thit b truyn ti trong h thng sy hm c th l bng ti hoc gmxe gong. Bng ti trong h thng sy hm dng xch kim loi c nhim vv vn chuyn vt liu sy, ng thi cho tc nhn sy i qua bng ti x

qua vt liu sy thc hin qu trnh trao i nhit - m.Cu to ca h thng sy hm bao gm ba phn chnh: hm sy, calori

qut. Hm sy l hm di t 10 n 20 hoc 30 m, trong vt liu sy v tsy thc hin qu trnh trao i nhit - m. Cc h thng sy hm c th tcho tc nhn sy v vt liu sy i cng chiu hoc l ngc chiu, hoc zchi lu hay khng hi lu ty thuc vo mc ch thit k.

II. H thng sy hm sy khoai ty

Mt cu hi t ra y l ti sao phi sy khoai ty?



6/28


Nh chng ta bit, khoai ty l mt loi thc phm giu cht dinh dKhoai ty l loi thc phm rt ph bin, c hng trm loi khc nhau. Chng phn bit da trn kch thc, hnh dng, mu sc v mi v. nhiu quc gi bit l chu u v M, y l mt loi thc phm quen thuc. Chng cng ltrong nhng thc phm giu dng cht nht. Trong 150g khoai ty cung khong 45% vitamin C cho nhu cu hng ngy ca bn. Chng c t nng lhn bi, nhiu kali hn chui v cung cp nhiu st hn cc loi rau c Khoai ty cn giu cht x, vitamin B6 v khong cht nh ng, mangan...

Tuy nhin khoai ty l c c thi gian thu hoch tng i ngn, bo qti li rt kh khn do phi s ch thnh dng nguyn liu c th gi luc. Khoai ty thng c s ch thnh dng lt. Quy trnh s ch thnh lt, tm tt, gm cc cng on sau:

C ti ngm ra thi lt phi sy x l thnh phm.

i vi c ti, ngay sau khi thi, b mt lt thng c "nha" chlm cho b mt lt rt chng b sm mu do b oxy ha. trnh hin tngsau khi thi, lt c ngm ngay trong nc sch hoc trong dung dch xKhoai lang v sn c th ngm vo dung dch nc vi trong khong 30 pht, nh vy lt sau ny s c mu trng p. Ring khoai ty ngm trong dung dnatri sunfit (Na2SO3) hoc natri bisunfit (NaHSO3) t l 1 so vi khi lng cti. Thi gian ngm 30 pht. Tt c cc lt sau khi ngm x l c vt ln rhoc nhng mt thong nhm lm cho lt thot bt nc. Cn o trn lt kh nng thot nc. Sau khi x l a lt v sy. gim bt thi gian snn c hong gi trc lm se lp b mt.

Nhng yu cu khi sy lt: Cc lt khi c hong cho se lp mt xp ln cc khay sy. Chiu dy ca lp lt trn khay khong 20mm. Cc lc xp ln xn trn khay th cng tt v nh vy tng c b mt bay hiKhay sy lm bng nhm c c l, cng c th lm mt khay bng tre nakch thc l 10 x 10mm (an hnh mt co). Nhit khng kh nng khi choxc vi sn phm sy phi m bo c cc yu cu: Nung nng sn phlm bay hi m, nhng khng c lm bin i cht lng ca chng.

Giai on u ca qu trnh sy, nhit cung cp ch yu l lm nn phm sy. Khi nhit lp b mt sn phm tng dn t ti nhit



7/28


th lng m b mt lt thot ra rt mnh. Qu trnh bay hi lp b mt ng thi vi qu trnh chuyn dch m t trong lng vt liu ra lp b mt. dn dn tc dng su vo pha trong lng lm cho nhit pha trong ca lt ln, thc y thm qu trnh chuyn dch m t trong lng vt cht ra lp bThi gian kh ca cc lt thng khng ng u, do cn phi o trn:trn ngay trn mt khay v o trn gia cc khay. Nu thc hin tt vic oc th lm gim c 1/3 thi gian sy. Tuy nhin, vic o trn mt s thsy khng thc hin c (nh kiu thit b ng hm), do bin php tl b tr v kt cu thit b thch hp tng kh nng phn b nhit tnng u cc tng khay v khu vc sy.

Vi loi thit b c kh nng truyn nhit v thot m tt, sau 8 10 gith lm kh c khi lt xung m cui cng l 12 12,5%. Cc lt sausy nht thit phi c lm ngui mi a vo bo qun.



8/28


Chng II: TNH TON QU TRNH SY L THUYT

I. Tnh nng sut sy trong mt gi

Nng sut sy trong h thng sy hm l sn lng thnh phm trong mt G = 200.103 kg/nm. Vt liu vo v ra khi thit b sy c m tng i l 1= 80%, 2 = 8%. Gi thit rng thit b lm vic 300 ngy/nm v mi ngy vic 20 gi.

Nng sut sy trong mt gi l:

2

200.1000 33,334300.20

GGT

= = = (kg/h)

Khi lng vt liu sy vo thit b:2

1 2

1

1 1 0,08. 33,334. 153,3341 1 0,8

G G

= = = (kg/h)

II. Tnh lng m bc hi trong mt gi 1 2W=G 153,334 33,334 120G = = (kgm/h)

III. Chn ch sy

Chn h thng sy hm khng hi lu, tc nhn sy l khng kh nng i chiu vi vt liu sy.

Thng s khng kh ngoi tri: t0 = 200C v 0 = 85%

Chn nhit tc nhn sy vo hm sy: t1 = 1300C, dung th ta tra c nhit nhit k t tng ng l: t = 390C

Nhit tc nhn sy ra khi hm sy phi m bo lm sao va tit kimnhit lng do tc nhn sy mang i, li va m bo khng xy ra hin tng sng.

y ta chn chnh nhit kh t ca khng kh ra khi hm sy l70C nhit khng kh ra khi hm sy l: t2 = t+ t = 39 + 7 = 460C



9/28


Ch lu ng ca kh trong hm l ch tun hon cng bc mnh v mi cht 2 m/s.

Nhit khng kh bn ngoi (trong phn xng ) l t0 = 200C, = 85%

Nhit vt liu sy ra khi hm: tv2 = t2 - t, ta chn t = 60C

tv2 = 46 6 = 400C

Thi gian sy chn theo kinh nghim: = 15 gi Ngun nng lng cung cp nhit cho tc nhn sy l hi nc bo hosut 5 bar.

IV. Tnh ton qu trnh sy l thuyt Ta c s nguyn l h thng sy nh hnh v:



10/28


Trong :1 Qut, 2: Calorifer, 3: Hm sy

th I d kho st qu trnh sy l thuyt c th hin nh hnh v:

T cp thng s ( t0 = 200C, = 85%) ta dng cng thc gii tch hoc l dng phng php th I d ta tm c cc thng s ng vi cc im tng n th.



11/28


0

4026,42 4026,4212 12 0,0233235,5 235,5 20

Pbt

= = = + + (bar)

0

.0,621.

.

Pbd

B Pb

=

(kg/kgkk)

d0 = 0,01264 (kg m/kg kk )

I0 = 1,004.t0 + d(2500 + 1,842.t0) = 52,139 (kJ/kgkk )

Nhit dung ring dn xut :

Cdx(d0) = C pk + C pa.d0 = 1,004 + 1,842.0,01264 = 1,027 (kJ/kg)

Thng s ca tc nhn sy ti im sau khi ra khi calorifer:

t1 = 1300C, vi d1 = d0 = 0,01264 (kg/kgkk )

I1 = 1,004.t1 + d1.(2500 + 1,842.t1) = 165,139 (kJ/kgkk)

Phn p sut bo ho hi nc nhit t1= 1300C l:

1

4026,42 4026,4212 12 2,6746235,5 235,5 130

Pbt

= = = + + (bar)

m tng i:( ) ( )

0

1

1 0

745 745. .0,01242750 750 0,73. 0,621 2,6746. 0,621 0,01242

d Pb d

= = =+ +(%)

Khi lng ring : ( )1 1

1

1

. 0,8417. 273k k

B Pb R t

= =+ (kg/m3)

Thng s ca tc nhn sy sau qu trnh sy l thuyt (I2 = I1 )

I2 = 1,004.t2 + d20.(2500 1,842.t2)

2 220

2

1, 004. 165,139 1, 004.460,0492500 1,004. 2500 1,004.46 I t d

t = = = (kgm/kgkk )

Phn p sut bo ha hi nc P b2 nhit t2 = 460C l :



12/28


20

20

4026,42 4026,4212 12 0,09991235,5 235,5 46

Pbt

= = = + + (bar )

m tng i 20 l:

( ) ( )

20

20

20 20

745 745. .0,0485750 750 0,7305 73,05

. 0,621 0,09991. 0,621 0,049

d

Pb d = = = + +

(%)

Khi lng ring : ( )2 2

2

2

. 1,0052. 273k k

B Pb R t

= =+ (kg/m3)

Lu lng khng kh cn thit bc hi mt kg m l:

0

20 1

1 127,3110,049 0,01264l d d = = = (kgkk/kg m)

Lu lng khng kh cn thit bc hi W = 120 kg m/h l:

L0 = W.l0 = 120.27,311 = 3277,487 (kgkk/h )

Nhit lng tiu hao trong qu trnh sy l thuyt:

q0 = l0.(I1 I0 ) = 27,311.(165,139 52,139 ) = 3086,25 (kJ/kg m)

Q0 = q0.W = 3086,25.120 = 370358 (kJ/h)



13/28


Chng III: XC NH KCH THC C BN

CA THIT B SY

Chn kiu thit b sy nh hnh v

Trong thit b ny, qu trnh sy xy ra trong hm. Kch thc c bn gchiu rng Bh, chiu cao Hh v chiu di Lh.

I. Xc nh tit din hm syTit din hm BxH c xc nh theo iu kin thng gi, cn chiu d

hm sy xc nh theo thi gian sy v nng sut sy.Tit din thng gi trong phn sy ca hn phi tha mn k thng gi, tc l

0

k k

V F v

=

y, vk l tc mi cht trong hm. Theo trn ta chn ch tun honcng bc mnh. Tc l vk 2m/s.

Vic chn vk nh hng n kch thc thit b v tnh kinh t ca h th Nu chn vk ln th tit din hm s nh v nh vy tha mn iu kin vgian sy v nng sut sy, chiu di hm sy s ln. Ngc li nu chn vk nh thtit din hm s tng i ln v chiu di s nh hn. Mt khc, tc khdn n tng nng lng vn chuyn kh. Xt ring v kch thc thit b t



14/28


cng chn tc vk hp l cho kch thc thit b hp l ( kch thc thit bcng nh hng n tn tht nhit vo mi trng ).

Vy ta chn tc lu ng ca kh trong hm l vk = 2 (m/s)

Tit din thng gi ca hm l:

0 3549,066 0,49293600. 3600.2k k

V F v

= = = (m2)

Chn h s in y tit din phn sy ca hm, F = 0,65

Tit din tng ca phn sy:0,4929 1,408

1 1 0,65k

s F

F F

= = = (m2)

II. Thit b Chuyn ti

y ta chn thit b chuyn ti l xe gong v kch thc xe gong tnh nh sau:

Chn chiu rng ca xe goong: Bx = 1000mm

Cc kch thc khc: H = B = 50 mm

chiu rng hm sy: Bh = Bx + 2. B = 1000 + 2.50 = 1100 (mm)

Chiu cao hm sy:1,048 1,281,2

sh

h

F H B

= = = (m) = 1280 (mm)

Chiu cao xe goong: Hx = 1280 50 = 1230 (mm)

Chiu cao sn xe: Hx = 200 (mm)

Tit din cn tr trong hm sy: Fc= Fs Fk =1,408 0,4929 = 0,9154 (m2

)Chn chiu dy ca lp vt liu sy trn khay l: Hvls = 60 mm

S khay sy cha trn xe gong l: 15,263.c

vls x

F n H B

= = khay



15/28


Chn li n = 15 khay

Khong cch gia cc khay sy: . 22 x vlsk H n H H

n = = (mm)

Chn li:

Chiu cao xe goong: Hx = 1,25 m

Chiu rng xe: Bx = 1 (m)

S khay cha VLS: 15 khay

Chiu dy lp vt liu sy trn khay: 0,06 (m)

Khong cch gia cc khay: 0,025 (m)

Chiu rng hm sy: Bh = 1,1 (m)

Chiu cao hm sy: Hh = 1,275 (m)

Tit din cn tr: Fc = 0,9 (m2)

Tit din ton b: Fs = 1,4025 (m2)

Tnh li h s in y: F = Fc/Fs = 0,6417

Nh vy ph hp vi gi thit chn

Tnh chiu di xe goong:

Chn mi khay cha c 8 kg vt liu m, khi lng ring ca khoai ty l kt= 1034 kg/m3

th tch khoai ty trn mt khay sy l: 38 7,7369.101034k kt kt

GV

= = = (m3)

Chiu di mt khay sy (cng chnh l chiu di xe goong )

( ) ( )

37,7369.10 0,651 . . 1 0,8 .0,06.1

kt x

k vls x

V L H B

= = = (m) = 650 (mm)



16/28


Tnh s xe goong cn thit trong hm sy:1. 153,334.15 19,167

15.8 xGnG

= = = xe

Chn li s xe: n = 20 xe

Khong cch phn b ti v tr ca hm sy: L = 1 m

Chiu di hm sy l: Lh = n.Lx + 2. L = 20.0,65 + 2.1 = 15 (m)

III. Kch thc tng bao v trn hm sy

Tng bao quanh hm sy gm 3 lp. Bn trong l lp gch dy = 110

mm vi h s dn nhit = 0,7 W/mK. gia l lp cch nhit dy = 50 mmvi h s dn nhit = 0,053 W/mK. Ngoi cng l lp tn bo v.

Trn hm sy cng bao gm 3 lp. Trong l b tong dy 100 mm vi h dn nhit 0,7 W/mK. Lp cch nhit dy 50 mm vi h s dn nhit 0,053 W/ Ngoi cng l lp tn bo v.

Kt cu tng th ca hm sy c trnh by nh bn v.



17/28


Chng IV: TNH TON QU TRNH SY THC

I. Tn tht nhit do vt liu sy mang i qV

tnh tn tht nhit do vt liu sy mang i, trc ht ta phi bit nhvt liu sy ra khi hm sy tv2 v nhit dung ring ca n Cv2 . Theo kinh nghim,trong sy nng sn, nhit vt liu sy ra khi thit b sy ly thp hn nhnhn sy tng ng t 5 100C. Trong h thng sy ny, vt liu sy v tc nhsy i cng chiu nhau nn:

tV2 = t2 (5 100C)ta chn tV2 = 46 6 = 400C

Nhit dung ring ca khoai ty l : Ck = 1,4214 (kJ/kgK), do khoai ty cnhit dung ring khi ra khi hm sy l:

Cv2 = Ck .(1- 2) + Ca. 2 = 1,4214.(1 0,08) + 4,18.0,08 = 1,642 (kJ/kgK)

Tn tht do vt liu sy mang i bng:

Qv = G2.Cv2.(tv2 tv1) = 33,334.1,642.(40 20) = 1094,74 (kJ/h)

1094,74 9,122W 120

V V

Qq = = = (kJ/kgm)

II. Tn tht do thit b chuyn ti mang ra khi hm- Tn tht do xe gong mang i.

Xe gong lm bng thp CT3 c khi lng mt xe Gx = 40 kg. Theo ph lc 4,nhit dung ring ca thp l: Cx = 0,5 kJ/kgK. V l thp nn nhit xe gong lcra khi hm sy ly bng nhit tc nhn sy: tx2 = t1 = 460C do

( ) ( )2 1. . . 20.40.0,5. 46 20 693,33315

x x x x x

n G C t t Q

= = = (kJ/h)

693,333 5,77W 120

x x

Qq = = = (kJ/kgm)

- Tn tht do khay sy mang i



18/28


Khay ng vt liu sy c lm bng nhm, mi khay c trng lng l 1 Nhit ca khay ra khi hm sy cng l nhit ca tc nhn sy, tk2 = t1 =460C. Theo ph lc 4, nhit dung ring ca nhm l, Ck = 0,86 kJ/kgK. Do tntht do khay sy mang i s l:

( ) ( )2 111. . . 15.20.1,5.0,86. 46 20 670,815

k k k k

n G t t Q

= = = (kJ/h)

670,8 5,589W 120

k k

Qq = = = (kJ/kgm)

Nh vy tn tht do thit b chuyn ti l:

QCT = Qx + Qk = 693,333 + 670,8 = 1364,133 (kJ/h)

1364,133 11,367W 120

CT CT

Qq = = = (kJ/kgm)

III. Tn tht ra mi trng

Phn b nhit qua tng hm sy

- Tn tht qua tng bao



19/28


Qt = k.Fxq. ttb

k: h s truyn nhit, 1 21 1 2 2

11 1k

=+ + +

i, i : chiu dy v h s dn nhit ca cc lp vt liu

1: H s ta nhit i lu cng bc ca tc nhn sy vi b mt tng, W

Theo bng 3 ti liu [2] ta c h s trao i nhit i lu cng bc khi kh cng dc theo b mt vch, i vi b mt nhm, v < 5 m/s

1 = 6,15 + 4,18.v = 6,15 + 4,18.2 = 14,51 (W/m2K)

2: H s trao i nhit i lu t nhin t tng ti khng kh bn ngoi, 2 = 0. t

tnh h s 2 ny ta gi thit chnh nhietj t b mt vch

t = tw4 t0 = 12,5K

Theo bng 1 ti liu [2] ta c 0 = 3,8525 W/m2K

Theo bng 2 ti liu [2] ta c t = 0,98 2 = 3,8525.0,98 = 3,77545(W/m2K)

Thay s k = 0,69719 W/m2K

ttb: chnh nhit trung bnh, ttb = tk t0

tk = 0,5.(t1 + t2) = 0,5.(130 + 46) = 880C

ttb = 88 20 = 68 K Mt dng nhit qua tng l: qt = k. ttb = 47,409 (W/m2)

Kim tra li chnh nhit gia b mt ngoi tng v khng kh l:

t = q/ 2 = 47,409/3,77545 = 12,43 K



20/28


Nh vy gi thit trn l hp l

Din tch xung quanh ca hm sy (k c phn ca ) l:

Fxq = 2.(Lh + 2.Bh).Hh = 43,86 (m2)

Tn tht nhit qua tng bao: Qt = k.Fxq. ttb = 2079,35 (W)

- Tn tht nhit qua trn hm sy

Qtr = k tr .Ftr . ttb

Theo trn ttb = 68K

H s truyn nhit k c tnh theo cng thc: 1 21 1 2 2

11 1tr k

=+ + +

1 = 14,51 W/m2K

1 = 0,1 m; 1 = 0,7 W/mK; 2 = 0,05 m; 2 = 0,053 W/mK

H s ta nhit i lu t nhin ca khng kh bn ngoi (trn hm syngang) l:

1,3. 1,3.3,77545 4,908tr tuong = = = (W/m2

K)k tr = 0,7358 (W/m2K)

Din tch trn hm sy: F = Lh.Bh = 15.1,1 = 16,5 (m2)

Tn tht nhit qua trn:

Qtr = Ftr .k tr . ttb = 825,657 (W)

- Tn tht nhit qua nn

Nhit trung bnh ca tc nhn sy l: tk = ( 46 + 130)/2 = 880C

V khong cch t hm n phn xng l 2m

Tra bng 7.1 ti liu [1] ta c tn tht nhit ring qua 1 m2 nn l:



21/28


qn = 53,38 W/m2

Din tch nn hm sy: Fn = Ftr = 16,5 m2

Nhit tn tht qua nn l: Qn = Fn.qn = 16,5.53,38 = 880,77 (W)

Vy tng tn tht nhit ra mi trng l:

Qmt = Qxq + Qtr + Qn = 3785,787 (W) = 13628,834 (kJ/h)

Tnh cho 1kg m: qmt = Qmt/W = 113,57 (kJ/kg m)

IV. Tng tn tht nhit trong qu trnh sy thc = Cn.tv1 ( qv + qct + qmt )

= 4,185.20 ( 9,122 + 11,367 + 113,57) = - 50,361 (kJ/kg m)V. Tnh ton qu trnh sy thc

th I d biu din qu trnh sy thc

Thng s trng thi thc ca khng kh ra khi hm sy c xc

Entanpi sau qu trnh sy thc:2 20 163,295t i i l = = (kJ/kg kk)



22/28


cha hi: 2 222

1,004. 0,04842500 1,842.

t t

i t d t

= = (kg/kgkk)

m tng i thc t: 222 2

. 0,72 72%.(0,621 )

t t

t

B d Pb d

= = =+

Tiu hao khng kh thc t

2 1

1 27,893t

l d d

= = (kgkk/kg m)

Lng khng kh cn bc hi W = 120 kg m l

L = l.W = 27,893.120 = 3347,28 (kgkk/h)

Tiu hao nhit thc tq = l.(I1 I0) = 27,893.(165,139 52,139) = 3151,978 (kJ/kg m)

Tnh cho W = 120 kg m/h : Q = q.W = 3151,987.120 = 378245,02 (kJ/h)

= 105,06 (kW)



23/28


Chng V: TNH CHN CALORIFER V THIT B PH

I. Tnh chn calorifer

Cng sut nhit ca calorifer:105,06 110,5890,95cal s

QQ

= = = (kW)

Vi s = 0,95 l hiu sut nhit ca calorifer

Tiu hao hi ca calorifer

'

cal

h

Q Di i

=

, kJ/kg

Trong : ih, entanpi ca hi nc vo calorifer, ih = i kJ/kg

i , entanpi ca nc ngng, kJ/kg

Vi p sut ca hi nc P = 5bar i = 2749 kJ/kg

i = 640 kJ/kg

110,589

0,0522749 640 D= = (kg/s) = 188,772 (kg/h)

y ta chn dng 2 calorifer nn tiu hao hi trn 1calorifer l: D = 94,386 kg

Xc nh b mt trao i nhit ca calorifer

..cal s

tb

Q F k t

=

chnh nhit trung bnh

1 2

1

.ln

tb t

t t t t t

=

t1 = th t0 = 152 20 = 132 K



24/28


t2 = th t1 = 152 130 = 22 K

H s hiu nh: = 1

132 22.1 61, 39

132ln22

tbt = =

(K)

H s truyn nhit k c xc nh theo bng 4 phn ph lc

y ta gi thit lu tc ca khng kh qua calorifer l : = 4 kg/m2s

k = 20,8 W/m2K

B mt truyn nhit3105,06.10 82,276

20,8.61,39 F = = (m2)

Ta s dng 2 calorifer, 1 chic c b mt truyn nhit l: F = 82,276/2 = 41,182

Tra bng phn ph lc ta chn c calorifer K9 kiu I c din tch btrao i nhit l 41,6 m2 v din tch tit din kh i qua l f = 0,486 m2.

Kim tra li lu tc khng kh qua calorifer:

= L/f = 3347,28/(3600.2.0,486) = 0,956 (kg/m2s)

Lu tc khng kh nh th s gy ra tr lc khng kh nh

Vy ta chn 2 calorifer K9 kiu I

Tr lc pha khng kh ca calorifer l pcal = 3,0 mmH2O

Cc kch thc ca calorifer l: A = 1250 mm

B = 902 mmC = 200 mm



25/28


II. Tnh ton kh ng v chn qut gi

S tnh ton kh ng



26/28


Tr lc ca h thng bao gm: tr lc ca calorifer, tr lc ma st ca dn kh v tr lc cc b ti cc tit din nh ch ngot, ng t thu ...

Tr lc ma st trong cc xe goong c xc nh theo cng thc:2

. . .2td

L v pd

= , N/m2

Trong :

l h s tr lc ma st, = 0,05 W/mK

L l chiu di phn sy, L = 15 m

dtd l ng knh tng ng ca khe thng gi gia cc khay cha vt liu

theo trn ta tnh c din tch thng gi ca hm sy l : Fk = 0,5m2

chu vi phn thng gi : u = 8,75 m

4. 4.0,5 0,2288,75td

f d u

= = = (m)

v: l tc kh trong hm sy, theo trn ta chn v = 2 m/s

: l khi lng ring ca ca kh trong hm (tnh theo nhit trung bnh ca

Cc tr lc cc b c tnh theo cng thc:2

. .2cv p = , N/m2

y cc h s tr lc cc b c ly theo ti liu [2]. Cc kt qu tnc a ra trong bng di y.



27/28


STT V tr gy tr lc

(kg/m3)v

(m/s)Cdi(m)

ktd(m)

P(N/m2)

1 Cn 0.8417 3.2 1.25 5.38692 Calorifer 303 Ngot 90 0.8417 3 1.1 4.16644 Ngot 90 0.8417 3 1.1 4.1664

Vo xe 20 ln 0.85 2 0.18 6.12Trong xe 0.85 2 15 0.228 0.05 5.5921Ra xe 20 ln 0.85 2 0.25 8.5

68 Ngot 90 1.005 2.8 1.1 4.333669 Ngot 90 1.005 2.8 1.1 4.3336

Tng cng 72.599

Ta c tng tr lc ca h thng l 72.599 N/m2 iu kin nhit kh t = 880C v = 0,9233 kg/m3. Ta chuyn tr lc ny v iu kin tiu chun k thut ta

1,2. 72,599. 94,350,9233

tctc p p

= = = N/m2

Nh vy ta chn qut theo kiu kin:

Lu lng3347

1812,520,9233.2V = = m3/h

p sut Ptc = 94,35 N/m2

Ta chn 2 qut ly tm 4 70 N04 vi tc qut l = 70 rad/s

Hiu sut qut l = 0,73



28/28


TI LIU THAM KHO

[1] GS.TSKH TRN VN PH TNH TON V THIT K H THN

SY Nh xut bn Gio dc[2] PGS.TS HONG VN CHC THIT K H THNG THIT B SY Nh xut bn Khoa hc v k thut

[3] Internet

da kts say_nam

Documents