SĐL - Báo cáo

I. TRCH YU1. Mc ch Kho st qu trnh sy i lu bng thc nghim : Xy ng ng cong sy v ng cong tc sy. Xc nh cc thng s sy: tc sy ng tc, m ti hn, m cn bng, thi gian sy ng tc v gim tc. nh gi sai s ca qu trnh sy.2. Phng php th nghim Tien hanh say giay loc 3 che o nhiet o cua caloriphe: 480C, 600C, 700C. at giay loc vao buong say, ghi nhan gia tr nhan khoi lng cua vat lieu sau khi lam am (G1). Sau o c 5 phut, ghi nhan gia tr can va hai gia tr nhiet o bau kho bau t; tiep tuc say en khi gia tr khoi lng vat lieu khong oi trong vong 15 phut th dng che o th nghiem nay va chuyen sang che o th nghiem khac.3. Kt qu th nghim Khi lng kh ban u ca 3 sp giy lc: Kch thc giy lc: Bng 1: S liu kt qu th nghimCh sy Ch sy Ch sy

01056211801008013909582138

5906211858081140572,584141

1075621201062,582140105582138

1562,5621181547,582139154081137

2048621202032,582141203081137

254062118252582140252581137

3032,562120302582139302581137

3527,562119352582140352581137

402562119

452562120

482562120

II. L THUYT TH NGHIM1. nh ngha Sy i lu l qu trnh tch m ra khi vt liu bng cch cp nhit cho m bay hi. Trong , c hai qu trnh truyn nhit v truyn m u c thc hin bng phng php i lu.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. Tch m vo mi trng xung quanh.3. Cc yu t nh hng Bn cht ca vt liu sy: cu trc, thnh phn ho hc, c tnh lin kt m Hnh dng vt liu sy: kch thc mu sy, b mt lp vt liu... Din tch b mt ring ca vt liu cng ln th tc sy cng nhanh. m u, m cui v m ti hn ca vt liu. m, nhit v tc ca khng kh. Chnh lch gia nhit u v nhit cui ca khng kh sy, nhit cui cao th nhit trung bnh ca khng kh cng cao, do tc sy cng tng. Nhng nhit cui khng nn qu cao v khng s dng trit nhit. Cu to thit b sy, phng thc v ch sy.4. Tc nhn sy Tc nhn sy l nhng cht ng gia nhit cho vt liu sy, nhm tch nc v hi nc ra khi vt liu Cc loi tc nhn sy: Khng kh nng: l loi mi cht ph bin, r tin thng c dng lm tc nhn sy. Khi l: c th dng than, ci, tru, du, to khi l. Hi qu nhit. Trong bi ny s dng khng kh nng lm tc nhn sy, v: Cn sch. R tin p ng c yu cu t tip xc vt liu sy. Lng m t.5. ng lc qu trnh sy

L chnh lch p sut hi ca nc (m) trn b mt vt liu v p sut ring phn ca hi nc trong khng kh m

Nu : vt nh m qu trnh sy

Nu : vt ht m lm m vt liu Nu : c s cn bng ng gia ht v nh m Trong thc t, ngi ta xy dng ng cn bng di dng

Nu : vt ht m lm m vt liu

Nu : vt nh m qu trnh sy Nu : c cn bng ng gia ht v m Cch biu din ng lc qu trnh sy Dng th sy: Dng Dng Dng Dng 6. Cc dng lin kt m Lin kt ho hc

L lin kt ca m vi vt liu di dng hoc tinh th ngm nc. VD: y l lin kt bn, khng th tch bng sy. Mun tch m ny phi dng phng php ha hc hoc nung chy. VD: dng m c ht. Lin kt vt l Lin kt hp ph: sy ch tch c mt phn lin kt ny Lin kt mao dn: l lin kt yu, s tch c bng sy. Lin kt thm thu: tch m t dung dch s kh hn t dung mi nguyn cht Lin kt c l m nm t do trn b mt hoc trong cc l xp v mao qun ln. Lin kt ny l lin kt yu, c th tch c bng sy, thm ch l bng phng php c hc.7. Xc nh tc sy bng cn bng nhit Lng nhit do dng tc nhn sy cung cp trong khong thi gian

(1) Nhit ny c tiu hao un nng vt liu(2) Bay hi m v ho hi nhit(3) Trong

h s cp nhit t tc nhn sy vo vt liu sy,

b mt vt liu,

nhit ca tc nhn sy, vt liu v hi m bo ho,

khi lng v nhit dung ring ca vt liu sy,

khi lng v nhit dung ring ca m,

n nhit ho hi ca m,

nhit dung ring ca hi m, Lng m bc hi trong thi gian

(4) hm m (hay m) ca vt liu, tnh theo vt liu kh, kg m/kg vt liu kh. T (1), (2), (3) v (4) ta c cn bng nhit:

(5) T (5) rt ra:

(6) y l biu thc tnh tc sy theo cn bng nhit.8. Phng trnh c bn ca ng hc qu trnh sy Theo phng trnh truyn m ca vt liu vo tc nhn sy:

(7) Trong

h s truyn m trong pha kh, (1 at hay 1 mmHg,)

p sut ca hi m trn b mt vt liu v trong pha kh, Thay vo (7) v bin i, ta c:

(8) Khi hi m khng b qu nhit (tc ) th biu thc (5) c bin i thnh

(9) cng hay mt dng nhit t Trong

khi lng ring ca vt liu kh,

: th tch vt liu kh,

nhit dung ring ca vt liu m,

bn knh qui i ca vt liu, Khi , nu b qua nhit lm qu nhit hi m, ta c

(10) Vi Chun s Rebinde c trng cho ng hc ca qu trnh sy Biu thc (10) l phng trnh c bn ca ng hc v sy, n cho bit s bin i m ca vt liu theo thi gian. Ta c th nhn c biu thc (10) khi gii h phng trnh vi phn m t truyn nhit truyn m trong vt liu. Nhng ni chung, h phng trnh ny khng gii c bng phng php gii tch.9. Lng nhit cp cho vt liu trong giai on sy gim tc Mt khc ta thy rng trong giai on sy gim tc, ng cong tc sy c dng ng thng, nn tc sy trong giai on ny c biu din:

(11)

h s t l, gi l h s sy. N ph thuc vo tc sy v tnh cht ca vt liu m, K chnh l h s gc ca ng cong tc sy giai on sy gim tc, nn ta c

(12) h s sy tng i, ph thuc vo tnh cht vt liu m m ti hn m cn bng tc sy ng tc, kg m/(kg vt liu kh.s) Tch phn phng trnh (11), ta c

(13) Hay logarit ho (8), ta c

(14) Nh vy, nu bit c h s sy K c th xc nh c thi gian cn thit thc hin giai on sy gim tc. H s sy tng i c xc nh bng thc nghim v c th tnh gn ng nh sau:

(15) m ban u ca vt liu T ta c

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

(17) Thay (17) v (10), ta c:

(18)10. Lng nhit cung cp cho vt liu trong giai on sy ng tc Trong giai on sy ng tc, ton b lng nhit cung cp t dng tc nhn bng lng nhit bc hi m v nhit vt liu khng i nn

(19)11. Cng trao i nhit

(20) Nh vy, theo biu thc (20), khi bit chun s Rb s tnh c cng trao i nhit theo m ca vt liu.12. ng cong sy v ng cong tc sya. ng cong sy: L ung cong biu din s thay i ca m vt liu (U) theo thi gian sy ():

(21) Dng ca ng cong sy: Ph thuc vo nhiu yu t nh: lin kt gia m v vt liu, hnh dng, kch thc, cu trc vt liu, phng php v ch sy. ng cong sy l hm ca qu trnh sy, v vy tuy ch v phng php sy khc nhau nhng ng cong sy vn c dng tng t nhau (xem hnh 1).b. ng cong tc sy: L ng cong biu din mi quan h gia tc sy v m (hm m) ca vt liu sy:

(22) T biu thc (22), (23) r rng ng cong tc sy l l o hm ca ng cong sy (xem hnh 2). Hnh 1: ng cong syHnh 2: ng cong tc syAB un nng vt liuAB un nng vt liuBC Sy ng tcBC Sy ng tcCD Sy gim tc CD Sy gim tc1 ng cong sy1 Vt liu dng bn mng, xp: Giy,2 ng nhit ca vt liuba,2 Vt liu keo3 Vt liu xp4 Vt liu keo xp: c im un (thay i c ch vn chuyn m)5 Vt liu c im gy khc (im ti hn th hai)13. Cc giai on ca qu trnh sy:a. AB giai on un nng vt liu : Ton b nhit cung cp un nng vt liu, m bc hi khng ng k. Nhit vt liu tng nhanh t n nhit bu t t ca tc nhn sy. m thay i khng nhiu. Tc sy tng nhanh t 0 n cc i. Thi gian ngn khng ng k.Thng giai on ny c b qua khi tnh ton.b. BC giai on sy ng tc : Nhit cung cp bc hi m t do b mt vt liu. Nhit ca vt liu bng t khng i. m ca vt liu gim nhanh. Tc sy khng i. Trong giai on ny tc khuch tn m t trong lng vt liu ra b mt ln hn tc bc hi t b mt, trn b mt lun bo ha m. Thi gian sy trong gian on ny (thi gian sy ng tc - ) c xc nh t:

(23) Nn tch phn (23) ln ta c:

(24) Vi Uth : l m ti hn, m cui giai on sy ng tc.c. CD giai on sy gim tc : Nhit ca vt liu tng dn t t ln t2 ca tc nhn. m gim chm n m cn bng u*. Tc sy gim dn t tc ng tc No xung 0, ty theo cu trc vt liu m c bin dng khc nhau. Tc khuch tn trong chm hn tc bc hi b mt, nn tc chm dn v c hin tng co b mt bc hi. Lc ny, trong vt liu xut hin 3 vng m: m, bc hi v kh.

Trong giai on ny, nu ng cong tc sy c dng ng thng ( hoc qui i sang ng thng;) th ta c th tch phn tnh thi gian sy giai on sy gim tc ny ():

(25) Vi U* : m cn bng, m kt thc giai on sy gim tc.

14. Thi gian sy vt liu:

Thi gian sy vt liu c tnh bng tng thi gian ca 3 giai on sy: t nng vt liu , sy dng tc () v sy gim tc (); c th b qua giai on t nng vt liu, v giai on ny xy ra rt nhanh. Biu thc tnh thi gian nh sau:

(26) Vi U2 : m ca vt liu cui qu trnh sy, tng ng vi; U2 > U* v thng c ly: U2 > U* = Ucb

III. DNG C THIT B V VT LIU SY1. Dng c - Thit b: H thng thit b sy gm Caloriphe: gm hai chm in tr kh, c cng sut 10KW v c n nh nhit nh b iu nhit t ngt. Qut ht: c tc 0,85 m/s, ht khng kh (tc nhn sy) v thi qua caloriphe nng nhit dng tc nhn ln nhit cn thit. H thng cn: xc nh lng m tch ra t vt liu sy. Hai ca gi: c van l, thay i lng tc nhn. H thng o nhit : gm hai u d nhit bu kh bu t c t trong bung sy bn tri gin li t vt liu sy v ng h c o nhit . Vt liu sy: 3 sp giy lc c gp i2. Tin trnh th nghima. Quan st h thng: Trc khi tin hnh th nghim (15 pht u gi), sinh vin phi quan st h thng i chiu vi s hnh v trong Gio trnh. Tm xem v tr: ca khng kh vo, qut, caloriphe, b iu chnh nhit , h thng o nhit bu t bu kh, cn, gin li t giy lc, ng h o nhit v ca khng kh ra. H thng in: tm cc cu dao qut, caloriphe (nhn ng dy dn), cc cng tc in trn hp iu khin nhit .b. Chun b th nghim: Xc nh khi lng kh ban u ca 3 xp giy lc: M ca bung sy ra t cn thn ln bn (v ca kh nng nguy him). Cch t giy lc vo bung sy: t nh nhng tng sp giy lc ln trn li sy pha trong bung sy (t c ba sp), khi kim ca cn s dao ng ch kim ht dao ng c gi tr cn (G0). Lm m giy lc: Ly khong 2/3 chu nc inox. Sau khi cn xong, ly giy lc ra v nhng nh nhng tng sp giy (trnh rch giy) vo chu nc ch khong 30 giy cho nc thm u giy, ly giy lc ln phi ngoi khng kh (trn song st ca s) cho n khi ht nhiu nc. Chun b ng h eo tay o thi gian. Kim tra h thng: Lp li ca bung sy vn cht cc con tn ca ca. M ht cc van l ca hai ca kh vo ra. Chm y nc vo bu nc (pha sau h thng, khng phi l cc cc nc i trng trn cn) o nhit bu t.

c. Khi ng h thng Khi ng qut: ng cu dao ca qut ht cc dng tc nhn vo v thi qua coloriphe gia nhit dng tc nhn (tm cu dao qut bng cch nhn ng dy dn in vo qut). Khi ng caloriphe: ng cu dao ca caloriphe dn in vo hp iu khin (nhn ng dy in s tm c cu dao caloriphe). Bt cng tc ca chm in tr th hai (HEATER II) v tr chnh gia sang ON. ch 70oC th bt thm cng tc ca chm in tr th nht (HEATER I) pha bn tri ca cng tc in tr th hai. Ci t nhit cho caloriphe: M np mica ca hp ci t nhit (pha trn cng tc ca chm in tr II) v ci t nhit cn thit. ng h in t trn hp ci t cho bit nhit ca caloriphe.d. Tin hnh cc ch th nghim: Ch h thng hot ng n nh khi: Nhit ca caloriphe t gi tr ci t (12oC). Giy lc phi khng cn nhiu nc. Tin hnh sy vt liu ch cn kho st: M ca bung sy ra t ca ln bn. t nh nhng tng sp giy lc ln cc li sy. Lp kn ca bung sy li. o s liu trong mt ch th nghim: Cc s liu cn o: khi lng, nhit bu kh bu t v thi gian.e. Cch c gi tr o: Khi lng (gam): khi t giy lc vo bung sy, kim ca cn s dao ng (cn gm hai kim, ch c dy kim mnh nh, khng c kim ln), ch kim ht dao ng, c s m dy kim trng (c s nh khng c s ln). Nu dy kim nm gia hai s th cng li chia i. Nhit (oF): ng h c hin th nhit o theo nguyn tc c hc: c tt c 4 kim (2 kim nh bn trong v 2 kim ln bn ngoi), quan tm hai kim ln (kim ln bn phi ch nhit bu kh; kim ln bn tri ch nhit bu t). u nhn ca cc kim ny s ch vo cc vng trn c ghi gi tr nhit (vng m c gi tr c th, vng mnh khng ghi gi tr mi vng l hai n v ). Gi tr nhit tng t trong ra ngoi, nu u kim nm gia hai vng mnh th ly gi tr l 1 . Thi gian: o bng ng h eo tay. Trong mt ch nhit , o s liu c chnh xc th cn lu : Khi phi giy lc bn ngoi, phi ch ht nhiu nc ri mi bt u ch th nghim xc nh c G1 chnh xc. Lu cch t giy lc ln li sy: phi theo chiu np gp giy lc t tri sang phi, tc theo chiu tc nhn v t mt cch phng phiu khng xp gc. Khng c t ngc li, v khi dng tc nhn thi qua s bung giy lc (do giy lc c gp i) thay i b mt bc hi dn n cc thng s sy s thay i v cui cng gy sai s th nghim. Chuyn i ch th nghim: M ca bung sy, ly giy lc ra lm m tip (lp li nh ban u). Ci t nhit caloriphe gi tr tip theo cho ch sy mi. Ch cho h thng hot ng n nh. Lp li trnh t nh ch u.f. Mt s lu trong qu trnh vn hnh h thng sy: Lun theo di s hot ng ca b iu nhit xem c chnh xc gi tr nhit ci t hay khng. Trng hp ch sy nhit cao m nhit caloriphe khng t gi tr ci t th phi khp bt ca dng kh ra (ch khp bt khng c ng kn). Cc ca kh vo ra phi lun m khng c ng. Chm nc lin tc vo bu nc o nhit bu t. Khng c m qut trn ngay bi th nghim v s lm kim cn dao ng (qut s 7 trn tp l in ca ra vo phng th nghim).g. Kt thc th nghim: Tt caloriphe: Tt cc cng tc ca cc chm in tr trn hp iu khin. Tr v khng cho hp ci t nhit . Ko cu dao in ca caloriphe. Tt qut: Sau khi tt caloriphe c 5 pht, mi ko cu dao qut cho caloriphe ngui. M ca bung sy ly giy lc ra v lp ca li. Kim tra h thng mt ln na v v sinh khu vc bi th nghim phng th nghim.

IV. KT QU TH NGHIM1. Kt qu x l s liu thBng 2: X l s liu thCh 48Ch 59Ch 70

t(ph)GtutktGtutktGtutk

0,000,1116,6747,780,000,1026,6759,440,000,1027,7858,89

0,080,0916,6747,780,080,0827,2260,000,080,0728,8960,56

0,170,0816,6748,890,170,0627,7860,000,170,0627,7858,89

0,250,0616,6747,780,250,0527,7859,440,250,0427,2258,33

0,330,0516,6748,890,330,0327,7860,560,330,0327,2258,33

0,420,0416,6747,780,420,0327,7860,000,420,0327,2258,33

0,480,0316,6748,890,480,0327,7859,440,480,0327,2258,33

0,580,0316,6748,330,580,0327,7860,000,580,0327,2258,33

0,670,0316,6748,33

0,750,0316,6748,89

0,830,0316,6748,89

2. Kt qu tnh ton

Bng 3: Cc thng s ch sy Ch sy 48oC

(oC)(oC)(mmHg)(mmHg)

0,00000,104832016,6747,7812,480,0031,11

0,08330,09002606072016,6747,7812,480,0031,11

0,16670,07482006072016,6748,8912,480,0032,22

0,24800,06251484860016,6747,7812,480,0031,11

0,33330,04801004860016,6748,8912,480,0032,22

0,41670,0400604048016,6747,7812,480,0031,11

0,48000,0325303036016,6748,8912,480,0032,22

0,58330,0275102024016,6748,3312,480,0031,67

0,66670,024801012016,6748,3312,480,0031,67

0,74800,024800016,6748,8912,480,0032,22

0,83330,024800016,6748,8912,480,0032,22



0,00000,100030026,6759,4423,05,032,78

0,08330,08002208096027,2260,0023,56,532,78

0,16670,06251487084027,7860,0025,07,332,22

0,24800,0475906072027,7859,4425,07,531,67

0,33330,0325306072027,7860,5625,07,032,78

0,41670,024803036027,7860,0025,07,332,22

0,48000,024800027,7859,4425,07,531,67

0,58330,024800027,7860,0025,07,332,22



0,00000,094828027,7858,8925,08,4831,11

0,08330,072519090108028,8960,5627,010,0031,67

0,16670,05481207084027,7858,8925,08,4831,11

0,24800,0400606072027,2258,3323,57,4831,11

0,33330,0300204048027,2258,3323,57,4831,11

0,41670,024802024027,2258,3323,57,4831,11

0,48000,024800027,2258,3323,57,4831,11

0,58330,024800027,2258,3323,57,4831,11

3. tha. ng cong sy

Hnh 3: ng cong sy ch

Hnh 4: ng cong sy ch sy

Hnh 5: ng cong sy ch

b. ng cong tc sy

Hnh 6: ng cong tc sy ch



Bng 6: Kt qu tnh ton t thCh sy

73,950106270,01358,480,39240,2360

105,160308400,00957,990,23200,1570

63,510208760,015713,790,24710,0838

Bng 7: Kt qu tnh ton L thuytCh sy 480C

UUthP(mmHg)Pm(mmHg)NNtbKJmf12

320177,80,012,48678,42678,420,00563,81610,03770,4714,40,210,75

260177,80,012,48678,420,00563,81610,03770,4714,4

200177,80,012,48678,420,00563,81610,03770,4714,4

148177,80,012,48678,420,00563,81610,03770,4714,4

100177,80,012,48678,420,00563,81610,03770,4714,4

60177,80,012,48678,420,00563,81610,03770,4714,4

30177,80,012,48678,420,00563,81610,03770,4714,4

10177,80,012,48678,420,00563,81610,03770,4714,4

0177,80,012,48678,420,00563,81610,03770,4714,4

0177,80,012,48678,420,00563,81610,03770,4714,4

0177,80,012,48678,420,00563,81610,03770,4714,4

Ch sy 590C


300166,75,023,00976,92957,250,00605,86150,03770,6814,40,200,30

220166,76,523,48922,650,00605,53590,03770,6414,4

148166,77,325,00960,640,00605,76390,03770,6714,4

90166,77,525,00949,790,00605,69870,03770,6614,4

30166,77,025,00976,920,00605,86150,03770,6814,4

0166,77,325,00960,640,00605,76390,03770,6714,4

0166,77,525,00949,790,00605,69870,03770,6614,4

0166,77,325,00960,640,00605,76390,03770,6714,4

Ch sy 590C


280155,68,525,00895,51881,950,00645,75690,03770,6214,40,180,29

190155,610,027,00922,650,00645,93130,03770,6414,4

120155,68,525,00895,510,00645,75690,03770,6214,4

60155,67,523,48868,380,00645,58240,03770,6014,4

20155,67,523,48868,380,00645,58240,03770,6014,4

0155,67,523,48868,380,00645,58240,03770,6014,4

0155,67,523,48868,380,00645,58240,03770,6014,4

0155,67,523,48868,380,00645,58240,03770,6014,4

Bng 8: Sai sChe o sayo am ti han Uth (%)Toc o say ang toc N (%/h)

Thc nghiemLy thuyetSai so (%)Thc nghiemLy thuyetSai so (%)

48oC73.948177.778-140,4027627.000678420-8,20

59oC105.160166.667-58,4887840.000957251-13,96

70oC63.510155.556-144,9308876.000881946-0,68

Che o sayHe so say tng oi He so say K, 1/h


48oC0,013520,005658,408,483,816154,99

59oC0,009510,006036,907,995,861526,62

70oC0,015750,006459,1713,795,756958,26

Che o sayThi gian say ang toc 1, hThi gian say ang toc 2, h


48oC0,39240,2146,490,23600,75-217,82

59oC0,23200,2013,780,15700,3-91,05

70oC0,24710,1827,170,08380,29-246,18

V. BN LUNCu 1 : Nhn xt v gii thch dng ng cong sy v ng cong tc sy so vi dng l thuyt.* ng cong sy:Vi nhng s liu th ta thu c v p dng phng php bnh phng cc tiu, ta thu c ng cong sy kh ging vi l thuyt. Trong bi th nghim ny, vy liu sy l giy lc, nn qua trnh un nng din ra kh nhanh, nn ta c th b qua giai on ny, v ghp chung vi giai on ng tc. Nhn xt chung: hnh dng ng cong sy sai lch so vi l thuyt khng ng k.* ng cong tc sy:ng cong tc sy cng c dng ph hp so vi l thuyt. l bi v ta khng dng cch v trung bnh U/, m ly vi phn trc tip trn ng cong sy. ng cong tc sy c chnh xc hn, ng l ta phi ly vi phn ti nhiu im. Nhng v cch ny qu phc tp nn ta ch ly ti 2 im. Cho nn nhn chung, ng cong tc sy tuy ng v hnh dng nhng v gi tr th khng c chnh xc lm.Theo KQ Th nghim thu c th U* = 0. Nhng trn thc t, U* khng th bng 0 do vt liu khng c sy kh tuyt i m lun cha 1 lng m cn bng nht nh. Tuy nhin trong mt bi th nghim no u c mt sai s nht nh, nn trong bi th nghim ny, ta ly U* = 0Cu 2 : Nhn xt v gii thch kt qu tnh ton, nu ln mi quan h ca cc thng s sy.* m cn bng U* : Theo ti liu (p53, [1]): m cn bng ph thuc vo m khng kh v nhit . Vi cng mt m, khi nhit cng tng th m cn bng ca vt liu cng gim. Nhng trong bi th nghim ny th U* = 0 l do : 3 xp giy lc m ta cn ban u khng phi l vt liu kh tuyt i, m l vt liu cha mt lng m cn bng nht nh ( iu kin nhit mi trng ngoi). Cho nn thc cht ta c th sy vt liu xung di Go = 45g, nhng khng th tnh mt cch chnh xc v khng c s liu ca khi lng vt liu kh tuyt i v do vt liu sy t n 1 m cn bng U*=Ucb=const.VI. Ta nhn thy rng: khi nhit sy cng tng th tc sy ng tc cng tng. iu ny hon ton ph hp vi l thuyt. l do khi nhit cng tng th ng lc ca qu trnh sy (th sy ) cng tng.* H s sy tng i trong giai on gim tc : Theo ti liu (p93, [1]): h s sy tng i ch ph thuc vo tnh cht ca vt liu m (loi vt liu, thc vt liu, m ban u ca vt liu,), khng ph thuc vo nhit ca tc nhn sy. Nhng trong bi th nghim ny, mc d 3 ch 480C, 60oC v 70oC c m ban u ca vt liu chnh lch khng ang k ( m ca ch 700C thp hn v trong qu trnh th nghim, mt phn giy lc b t v r trong nc) nhng li khc nhau. l do c xc nh theo cng thc: . M nh ni trn, U* v Uth tnh ton c l khng chnh xc nn dn n sai s ca . Tuy nhin theo kt qu ta thy, chnh lch gia cc ch khng ln lm 16%* H s sy trong giai on gim tc K : Theo ti liu (p93, [1]): h s sy K ph thuc vo ch sy (tc sy ng tc N) v tnh cht ca vt liu m () theo cng thc K = N. iu c ngha l vi tnh cht ca vt liu m khng i, khi nhit tc nhn sy cng tng th K cng tng (do khng i, cn N th tng ln) Kt qu th nghim ph hp vi l thuyt, K tng theo nhit tc nhn sy. * Thi gian un nng vt liu : Da vo ng cong sy khi nhit tc nhn sy cng tng th thi gian un nng vt liu cng ngn. iu ny l hon ton ph hp so vi l thuyt, do nhit sy cng tng th vt liu s t n trng thi bc hi nhanh hn. Tuy nhin, giai on ny rt ngn, khng ng k, cho nn trong tnh ton ta thng b qua giai on ny.* Thi gian sy ng tc 1 : Theo l thuyt, khi nhit sy cng tng th thi gian th thi gian 1 cng gim. l do 1 c tnh theo cng thc . M khi nhit tc nhn sy tng th Uth tnh c cng tng, trong khi N tng nhanh hn Uth 1 gim kt qu th nghim l hon ton ph hp vi l thuyt.* Thi gian sy gim tc 2 : Theo l thuyt, khi nhit sy cng tng th thi gian th thi gian 2 cng gim. Nh KQ tnh ton ging vi l thuyt. Tuy nhin trong qu trnh tnh ton vn cn sai s, v khi ta dng ng cong sy v ng cong tc sy u gn ng. Ta cng nhn thy rng thi gian sy gim tc 2 ln hn thi gian sy ng tc 1. Tnh cht ny cn ty thuc vo loi vt liu (ty thuc vo cc lin kt ca m vi vt liu) Mi quan h ca cc thng s sy theo l thuyt: Khi nhit tc nhn sy cng tng th:

U*UthNKo12

= const

Cu 3 : Nhn xt v gii thch kt qu nh gi sai s. * m ti hn Uth : Sai s ca php o Uth l kh ln ( 48%). Cc gi tr Uth tnh theo thc nghim nh hn l thuyt (do sai s c gi tr m). l do sai s khi ta xy dng ng cong sy v ng cong tc sy xc nh Uth. Ngoi ra cn c nhng sai s trong qu trnh lm th nghim (s ni phn sau). * Tc sy ng tc N : Sai s ch sy 48oC, 590C l nh, khng ng k. Cn sai s ch sy 70oC li kh ln. Sai s tng dn khi nhit sy tng dn. Kt qu tnh ton c sai s l do trong qu trnh tnh ton N l thuyt, n gin ta s dng cng thc thc nghim p = 0,0229 + 0,0174vk , kg/m2.h.mmHg. Cng thc ny khng phn nh ht s ph thuc ca h s trao i m p vo cc yu t nh hng ln n nh cng thc chun m ch phn nh s ph thuc vo tc tc nhn sy. V khi ta coi p l mt hng s trong sut qu trnh sy, chnh iu ny dn n sai bit ni trn khi p khng th phn nh c chnh xc din tin qu trnh sy. Ngoi ra cn do sai s do dng gin khng kh m tra Pm v P, tuy s dng phn mm tra t ng tuy nhin vn c sai s, ng thi cn do gin ny c xy dng p sut 745mmHg, trong khi p sut th nghim khng trng vi p sut ny. Nhng sai s ny l khng ng k. Bn cnh cn do sai s khi dng ng cong sy v ng cong tc sy tm N v sai s trong qu trnh lm th nghim.* H s sy tng i trong giai on gim tc :Sai s ca l kh ln ( 60%). l do sai s khi ta xc nh Uth v U*. * H s sy trong giai on gim tc K :Sai s ca K l kh ln ( 60%). l do sai s khi xc nh v N (nh ni trn).* Thi gian sy ng tc 1 : Sai s ca 1 2 ch 48oC v 60oC l kh ln, ch c ch 70oC l nh. Gi tr 1 o c trong thc nghim ln hn so vi l thuyt. Tuy nhin ch 70oC li ln hn. l do sai s khi xc nh cc thng s trn. * Thi gian sy ng tc 2 : Sai s ca 2 l kh ln ( 60%). Gi tr 2 o c trong thc nghim nh hn so vi l thuyt. l do sai s khi xc nh cc thng s trn. Cu 4 : Nu cc nguyn nhn v bin php khc phc sai s.* Cc nguyn nhn sai s : Trong qu trnh lm th nghim: Do vt liu ban u khng phi l vt liu kh tuyt i, cho nn dn n sai s trong tnh ton ( ni trong Cu 2, phn U*). Do c s trn cn khng chnh xc. V rt kh c s khi kim dao ng gia 2 vch. Do c s trn vng o nhit bu kh v bu t khng chnh xc. V nhit dao ng trong mt khong rt nh. Do bm thi gian khng hon ton l chnh xc. Ngoi ra, cn do thit b c k nn khng cn c chnh xc na. Trong qu trnh tnh ton: Do dng gin tra Pm v P . ng thi cn do gin ny c xy dng p sut 745mmHg, trong khi p sut th nghim khng trng vi p sut ny. Nhng sai s ny l khng ng k. Do dng ng cong tc sy da trn phng trnh ng cong sy Do la chn cng thc khi tnh N l thuyt p = 0,0229 + 0,0174vk , kg/m2.h.mmHg (nh ni Cu 3, phn N)* Cc bin php khc phc sai s : Trong qu trnh lm th nghim: Vt liu ban u phi l vt liu kh tuyt i, hoc bng cch no xc nh trc c khi lng kh tuyt i ca vt liu. Phi ch tht k c c s liu chnh xc. Nhng tt nht l phng th nghim nn c cc thit b o in t vic c s liu c chnh xc hn. Trong qu trnh tnh ton: Phi cn thn hn trong vic tra th. Tt nht l p dng cc cng thc tnh ton thay v tra trn gin . Dng phng php Bnh phng cc tiu v ng cong sy v ng cong tc sy. Nn p dng cng thc tnh p.

VI. PH LC1. Tnh ton cc thng s

2. Tnh ton cc thng s

3. Dng ng cong sy T cc gi tr tnh ton c trong bng 3, ta xc nh cc im tng ng trn th Nh bit, ng cong sy biu th 3 giai on chnh: un nng vt liu: c dng on thng nm ngang (rt ngn) Sy ng tc: c dng ng cong nhng c th xem l ng thng. Sy gim tc: c dng ng cong tim cn n mt gi tr no T , ta v 3 on ti u nht theo phng php bnh phng cc tiu xc nh giao im 2 ng (ng thng v ng bc 2), ta chn 1 im nghi ng, ri dng ng 2 ng nh trn. Sau o hm 2 phng trnh trn, cho bng nhau ra c thi gian sy ti giao im, th vo 1 trong 2 phng trnh ban u s tm c U ti giao im, so vi U xc nh bng th, nu 2 gi tr ny gn bng nhau th ta chn im l giao im 2 ng. Nu 2 gi tr rt khc xa nhau th tin hnh chn im khc v tin hnh nh trn4. ng cong tc sy ng cong tc sy l o hm ca ng cong sy. Trn c s , ta c cc bc thc hin nh sau: giai on th hai: sau khi c hm ca ng thng, ta o hm tm gi tr ca tc sy trong giai on sy ng tc. chnh l gi tr tuyt i ca h s gc ca on thng va tm c (v ). giai on th ba: nh ta bit, giy lc l vt liu dng bn mng, xp nn ng cong tc sy trong giai on sy gim tc l ng thng. V ng thng ny i qua im (U*, N = 0) nn ta ch cn tm thm mt im na, bng cch: K mt tip tuyn vi ng cong sy trong giai on 3 ti mt thi im no . Chn thi im thch hp trong giai on sy gim tc Dng ng thng i qua 2 im (U*, 0) v (U, N) ta c ng cong tc sy trong giai on gim tc. Giao im ca ng gim tc v ng ng tc l Uth. chnh xc, ta phi v nhiu tip tuyn ti nhiu im biu din cc im ny ln th ng cong tc sy dng phng php bnh phng cc tiu tm ng thng tt nht i qua cc im . Nhng, phng php ny rt phc tp.5. Tnh ton cc gi tr Tm gi tr trn th: chnh l honh giao im ca ng ng tc v ng gim tc.

6. Tnh ton cc gi tr trong

l m ban u ca vt liu ti thi im l m cn bng ca vt liu Sy ng tc: Sy gim tc:

l b mt ring khi lng ca vt liu l b mt bay hi ca vt liu

N l tc sy ng tc c ly t trung bnh cc gi tr N trong bng7. Tnh sai s

Sai s (%) =

VII. TI LIU THAM KHO[1]. Nguyen Van Lua, Qua trnh va Thiet b trong Cong Nghe Hoa Hoc & Thc pham Tap 7: Ky thuat say vat lieu, Nha xuat ban ai hoc Quoc gia TpHCM, 2001, 252tr.[2]. Vo Van Bang Vu Ba Minh, Qua trnh va Thiet b trong Cong Nghe Hoa Hoc & Thc pham Tap 3: Truyen Khoi, Nha xuat ban ai hoc Quoc gia TpHCM, 2004, 388tr.[3]. Giao trnh Th nghiem QTTB Bo mon May & Thiet b H Bach Khoa TP.HCM

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