DA KTS SAY_NAM

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    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

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 2

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 3

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    NGUYN DANH NAM _ MY & TBNL2 K4

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

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

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

    n mn hc: K THUT SY 4

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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?

    n mn hc: K THUT SY 5

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 6

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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.

    n mn hc: K THUT SY 7

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 8

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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:

    n mn hc: K THUT SY 9

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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.

    n mn hc: K THUT SY 10

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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 :

    n mn hc: K THUT SY 11

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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)

    n mn hc: K THUT SY 12

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 13

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 14

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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)

    n mn hc: K THUT SY 15

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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.

    n mn hc: K THUT SY 16

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 17

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 18

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 19

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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:

    n mn hc: K THUT SY 20

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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)

    n mn hc: K THUT SY 21

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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)

    n mn hc: K THUT SY 22

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 23

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 24

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    NGUYN DANH NAM _ MY & TBNL2 K4

    II. Tnh ton kh ng v chn qut gi

    S tnh ton kh ng

    n mn hc: K THUT SY 25

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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.

    n mn hc: K THUT SY 26

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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

    n mn hc: K THUT SY 27

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    NGUYN DANH NAM _ MY & TBNL2 K4

    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