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11'Ul'1'I ft'n. YI 17 ~1J1JYI 2 11'U11tl1J 2537

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9' GI

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" f f I

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I i.t I 'll

t11mfil 80% i'.lt11J1112"'lt.1,::'V1~1~rifl'~-l1uViH'1:::L'VltJu1!Jit1t11J111m1&.J~i;i~1~c;) Lc;)tJ,,::;~uLtl~'a-lrlfl~

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1

~... ., ... ., 11'Hl1'i t'l'H. U'YI 17 ~UU'YI 2 1i'U11fl'l.J 2537

Continuous Fluidized Bed Paddy Drying

Appropriate Drying Strategy

Ornanong Sripawatakul, Somkiat Prachayawarakorn and Somchart Soponronnarit

King Mongkut's Institute of Technology Thonburi Suksawat 48 Rd., Bangkok 10140,

Abstract

The objective of this research was to investigate appropriate strategies for drying

of high moisture paddy by continuous fluidized bed technique. A mathematical model was

developed and employed in order to achieve the ob.fective. High product quality, high drying

capacity and low energy consumption were taken in to consideration. Drying condition in

simulation were fixed at an air temperature of 115° c initial moisture content of 30% dry basis,

final moisture content of 22 % dry basis and ambient air temperature and relative humidity of 30° c

and 70% respectively. Resits indicated that the ratio of enerrgy consumption to drying capacity

was lowest at the weir height of 10 cm, the specific air flow rate of 0.043 kg/s-kg dry matter and

the fraction of air recycled of 80%. At these conditions, the primary energy consumption was 7.9

MJ/kg water evap, the cost of drying was 2.05 baht/kg water evap. '

2

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3

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I l l.; f

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LtJ'ilfL"l!'UfiLi.J~Vliif1'lL~i.JLi.J~VILLtJ11::\i1~1-:1 55 - 58% Thorpe (1987) Vi~'U1LL1J1J~1~'il-:!Vl'N " . '

ri NIJ!fl\1~ 1J1f~1\i1T1J,j1 L~ ti L 'ULi.J~lilYl"ll LL1J1J~~~lil1(;1 L'11i'U'ClU1-:Ii;i'tl LU'il-:1

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rl'l1i.J~'U~-:1 LVltJ 1-f L Vl ri wri~~a f;1Llil L 'lli u 'W1J~1fi 1Jl11 n11 L'vl ~"IJ'tl-:l'il1 m fl\~1 L w1:: LL~::'q nmr.in"IJ'tl-:1

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. " ' ~1L'W'l:: 0.1 kg/s-kg dry matter r.i::ilfii;i11~'J'U'1::\-l~1-:iw~-:i-:i1uYi1-D1::L'vltJU1i;i'ilfim1mw~f;li;i1~r;i • 'il'l'il'U-:!Pl 1"11w'l1Vl~~ ( 1993) ~ n1!!'1 n11'il1J LL~-:iir1'lLtl~'iln~"li'l-:iri'J1i.J~'U(l-:I LVltJL -ir3fi'ilULL1X-:i LLuu

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1n~ LfiitJ-:i nuCJfln11'VlV'lflfl-:i ·

4

:'I ..I ., ..i ., 1l'fn'l'i 'a''ilti. U'YI 17 Q1J1J'YI 2 ti'U1lfllJ 2537

SI I I I

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Soponronnarit and Prachayawarakorn (1992) L~~(ij.JU1LLUU~1~tl..:JY11..:Jfllruf;lfll1~(;1f~1,,..fu ' " '

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1. ?UJn1'i mean residence time ( 't ) 'll'il-3-li'1'lLUfi'ilnL1JLfi~'il..:J'il1.JLL1X-3

hold up = ((-0.0095 + 0.5987 F- (0.002 + 0.1736 Fl V)

+ (1.1728 - 0.0823 v + (2.2093 - 0.1505 V) F) h] PpA

't = hold up/F

( 1)

(2)

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U'ElUoif1'lLU~t:in 1.5 • 3.5 kg/min

" hold up ~t1 il1,,..un"llt1..:J-i111LU~t1n'luli1tJ!jnm!. kg

F

A

v di er l"ltl l'l'l1i.JL1'l"ll'El..:Jtl1n1fll, m/s

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5

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= t /n " '

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J.J"lflLL1-l~'!Jtl-3;J1-JLtlfltintuiuVi i hpx :: hp/n

d .... ~ --mm ix flltl fl!Jl11n11 L'VlfiL"ll.:JJ.J'l~'!J'fl.:J'fl1n1fll, kg/s

hp ;if) J.J'J~LL".:J'Tl'fMi1'lLU~'fln, kg

., ., tl'"' fli.Jn11'fl'l.JLL'\N'!J1"lL ~'fln

MR = exp (-xt Yi

Lf;lt.J~ MR = IM(tl - Meql I !M;n· Meql

X = 0.00163100Tmix - 1.16202 I mmixx I hpxl + 0.00415300 ( mmixx I hpxl

(3)

(4)

(5)

(6)

(7)

T mix + 0.147383 In( mmixx I hpxl + 0.474743 (R2 = 0.762) (8)

Y = -0.00322000 T mix • 0.835960 ( mmixx I hpxl + 0.0203190 ( mmixx I hpxl

T mix - 0. 143150 In( mmixx I hpx) + 0.548493 (R2 = 0.961 I (9)

t-n1~ueri'J.:J'!J'fl"3~N'Vl1Ji'.i 90 - 140 °c LLfi~'fi1J1rm11lt.U~'!Jtl"3'fl1n1fll~1L'Y'l1: 0.03 • 0.16 kg/s­

kg dry matter

~i.Jn1'ffll"l1i.J~U~>J~fi'!Jfl"3ir1'lLU~'fln"'1n "ll'fl'U fi1t.J'Vltl.:J (2530)

1-RH = exp[-4.723x10-6 (1.8T mix+ 491.7) (100Meq12.386 J 110)

di .t a d ..l L ,,/. " M(t) fll'fl fll"l1i.J'.llU'!Jtl.:JLJ.J~~Vi"llVIL"lfi1 fl 1· Lflll:tri"l'Ui.J111l1J1ULL'Vl"3

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T mix ;jtl ~N'VllJij'!l'fl'l?nn1fl\CJ~i.J. oc

2.2. 01'1A'1U'l Wftll'1'lZ'il1n1fll'Vlfl'3'iltlLL i-3 " I o

~"'11ru1iuVi i 'lu Fig.2 "'1n'Vlflnn11VIN'Y'lfl"3"31Ur.t~'"n1'1LU~t.JULLtlfi"3LtlUfifiU

'!J'fl'l n1~ LL~tl1 n1 f1\J';J n riu n11L tl~t.JULLUfi"3Vifl'l'l1U111t.J t \.Jrl~ f;Jtl'U LL ""3 L vhriu CJfi1"li.J'!J'fl"3fl"l1 >J l'flu~

6

~..; ., ..; ., 11'fff1'l' t1'111i. ufl 1 7 \'.l'U'Ufl 2 1i'U11fl1J 2537

. . . LL~n Ltl~t1u1:::"1~1.:i Lri'1·rNflULL'IX.:i LLfl:::~.:i LL'"l1'l~fllJ

a1

Tt(i) = 101/mmix + Ca T mix + Wmixl htg + Cv T mix l+RCpw T mix - Wt(i) htg l /

( Ca+ Wt0)Cv+RCpwl . " df 4l. "' t;q-

f"lfl 'qn.l'M.IJlJ"llfJ-l'tl1n1P'l"1fl-ln1'1flULL'M.:!Vl"JIU i, oc

di_. J' ... .,.,J!;. fllfl flf11'11lli'"lUf"l'J1lJ'llU'llfl.:lfJ1n1fll'Mfl.:ln11fJULL'M.:!Vl"llU i, kg water I kg dry air

" ~fl tllJl'11~'"l1Jfll'l1lJ=DU"llfJ-lfJ1n1fllrifJUfJ1JLL'IX.:i. kg water/kg dry air

~fl fll'"l1lJ,fJU~~tyL~tl'l'IXnu~.:iLL'"l1'l~fllJ, kW

d " • " fllfl fll'"l1lJ1fJU'°i1LW1:::'llfJ\l'il1n1fllLL'M.:I, kJ/kg oc

" ~fJ 1'11'"l1lJ1flur.i1 LW1:::'llfJ.:!1flth kJ/kg oc

.di " • ti - l<df Cpw fllfJ fil'"l1lJ'lfJU'°i1LW1:::'llfJ.:l'll1'"lL1.JflfJn, kJ/kg oc

htg ~fl fil'"l1lJ1flULLt.l.:!l 1Jn1'1'1:::L'Mt1tl1, kJ/kg

R ~fl t1i;i11fi'"lUlJ'l~-i11'"lLUftflnLLi!i'.:111itllJ'"lfl'tl1n1fl!LL"°1.:1~\ILvl1rlU hpx I mmixxt

( 11)

w~11ru1n!JV1Nll'"lfl 'l utl1i.i1 r;i1fll'"lU"Ji.i.f u~ i tl1i.i1rutl1 'l ummfll~ L~i.i~uL vi1nutl1i.i1ru

tl1~1::: L "1tlfltl n"'!1n;J1'"l Ltl~fl n fl1i.i11n'M1tr i;i11~'"lUfll'"l'lll~ U'llfl.:lfl'l m fll'Mi.:i m1fl1J LL 'IX.:i~.f u i 1v1

Wf(i) = R(Mi - Mtl + W mix (121 " . "

M; ~fJ fll'l'llJ~U'!lfl-l;J'l'"lLU~flnL~flLmH-ihiu i, Ll°l~~'lUlJ'llJl'll1ULL'IX.:i " . "

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" I I,; I t

iuVi 1 -;uii\li'uVi n ~111'l:::'llfl\lfl'ln'lfllL'il~t.J'Mi.:im1fJULL'IX.:i'tv1!0i1n

Tt1 = l:Trn/n

Wt1 = L:ww11n • v d ..,

2 .3. 10l1'l~inn1flf n'il'l.IL '!11L Fl'iiNiltlLL lM

(13)

(14)

w-;11ru1tfill'1lJl'lfll'"l'Uf'JlJ CV2 LU Fig.1 LiJUviflfl'ln1f'IL'MflL~tlUniu '°i1nn!JVIN

wi.:i.:i1u '°i :::1cX~1 mrn.J~ t1ULL1fo.:i L flUttflU'!lfl\I m·::: LL~fl'l mfll L vh nu CJfl'l'"llJ ri11 i.J1flu~ LL~ n Ltl~t1u

" tf1ll'1lJ1'11°l'l1Jl°llJ CV2 L~i;i'.:iil •

Tt2 = [02/I RCmmixl + CaTf1 + Wf1CvTt1l I (Ca+ Wt1Cvl (15)

7

Ttz

RC

Oz

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... ..... ~ ..... fil'Cl 'El1111'1n'11L'lt.JUn~U'IJ'il..J'fl'1n'1fll, (mRdmmixl

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mRc ~'tl tT11111m1L\H'H:0'1>.J'lfl"ll'tl'l'Cl'1n'1fllL~uun~'U. kg dry air/s

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Wmix = (1-RC)Wj + RCWt1 (16)

... ... ' J' 'I • Wj filt:l tl1111'1fl'l\..lf11'l1).J"JIU'll'El..:J'fl'1n'1~LVl).J, kg water/kg dry air

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mmix Ca T x + mmix Wmix lhtg+Cv T x) - miCa!Tj) - mjWjlhtg + Cv Tjl

- mRc Ca Tf2 - mRc Wt1 (hfg + CvTf2) = 0 (17)

~tl ~NVllJij'!ltl'li11n'1fll£.J~2.Jri'ClUL-!J1frc;if1i.J, oc

Ti ... ~ " filtl ~NVIJJi..!'ll'Cl..:Jtl1n1fll LL'l~fl'CJ).J, 0c

- ..1.-::.~- ..., 3.2 'el CU'4-tJi.l'U'il..:J'il1 n1PIVIL 'Wi.1'11\.IL \.l'il..:J"i1n 'W~fti.J

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L vi1 rl'l.N1UL Ylfl1~L tX LLriYr i;i fl).J ti;iu~).J).J ;i m7thu L YJ fil'l'1).J1'flu ~ill).J11117 fil'lU fJ ).J,jtlui..11 n ft1i..11rnvi1

~ rui.JJij'lltl'l'fl'1 mfll~ L ~i..1~u"ll ru::: 1 i.u~ t.huYr ~fl ).J H1 ~'Id ~ Ttan = P/[( PantHCa+CvWmix)) (181

nt ~tl tl,-:::~YJHl1'1Yl"ll'iNYl'Vlfl).J

Tb= Tx + ~Ttan (19)

Tb ~f.l 'QC1.4VllJi'.j"llfl'lfl1n1Pl~fltlnllil1nfl''1tU.J, oc

3.3 ni<7A11.11ru \41 Fl'l1 i.iii'1.1L tla1H'Wfi°'-3..:i11.1F1'l1i.i;'il1.1

~"'1,-ru1ill;.i1111,-ri'lUl"Ji..! cvs Lu Fig.1 LU\..l~'lu~·l~Y1~'1'11Ufil'l1iJ1flu n'17Ltl~uu

8

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LLtl ~NL fl ufi fl U'llfl\lm·::; LL~fl1 mfll LVh nu n17~ q; L~fJ fil'l1" 1au L iAriu~\I LL'l i;i ~fl" Llfl :::lli-"1 n.lfil'l1"1au

~'l~fu;nnl'i'l~t.tfl1m;ii L;iuu~"m1't;J~\ld

a5 + ah = · mmix [Ca + !Cv Wmixll ff mix · T bl .. ah ~fl fl"111n11~'WLU~!l\1Wfl\l\11Ufll'l1"1fl'W, kW

a5 ~fl fl11111n'l1~q)LftfJWi\l\111..IP'l'l1"1flt.t~ heater, kW

3.4 n1'ifi1u·uu\nn1'i~UL Uft'iHIL vHh .. flf;J11 m1~uLtl~1fWr'i fl\l\11'WLv-l~1'Dfl\I~ fl fl"~ 1"11n fii1u'lru 't~r.i1n~"m1

W5 = E/em

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E

. "

(20)

(21)

l'i1t.t'ln.lvt1 mean residence time r.i1n~"m1 (2) L0flLLU\l~'ltl!jn1ruflflnLU'W n -Du ~1"1"1 . "

ri1'W'lCU~1fi1 t, mmixx· hPx 't"r.i1n~"m1 (3). (4) LLfl::: (5) r;i1"~1~u r.i1m!uri1u'lru,..1 Wmix

r.i1n~"m1~ (161 LflfJ~i.ii.if;ifi1 Wt1 Lvhnu 0.02 LL~'lu11'11 Wmix ~L~LLfl::: T mix ~\ILU'Wrh~i I t,.c .... I

'ltlri1u'lru~1fi1 RH LLfl:::fi1 Meq r.i1n~i.im1Vi (1 Ol r.i1n-L!u~r.i11ru1iuVI i t111tm11ri1u'ln.iM1

J'.i..I ti 41 ..;, ::,..; "' ti•

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vlflLUr.ium:::n\ln\1-i'WYl n r.i1nt!uri1'W'ln.ll-11 Tt1 LLfl::: Wt1 r.i1n~i.im1YI (13) Llft::: (14) i;i1"~1~u

Ltl1t1t1LViuu1:::vt~1\lfi1 Wt1 ~ri1u'ln.iL~nul"i1 Wt1 ~~""~;}'W ti1i'.i1"11i.i1nn~1 0.00001 riniu

'ltlri1'W'lCUrhL~~ LflfJ~""~~1 Wt1 Lvi1nul"i1 Wt1 r.i1n~"n17~ (14) n'"1t:Jfl;i1\11:::l-1~1\I' W11

'i1n~"n11~ (14) nu Wt1 ~~""~~u~t8\1U'Elt.Jn~1 0.00001 nri1'W'ln.!~1rl'l1"i(ULU~fl\1Yii\l\11U "

vitJLU 'lum11'i1t.1'ln.l~ff1'l:::'lJfl\lfl1n1Pl~u1if~"m1'llfl\I Wilhelm (1976)

9

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f"l'l1).J~'Uli'ltlu.if1..:i~-3 l'i1 'l lX~'i.l-3 'l-D L'Jfl1\..11UL Un11'i.lULLlX-3 r.i1n Fig.8 ~r.i11ru1€11111i'l'l'l.J.1!::i.l~1'3

'r'li-3-31'1.J.U 3>J.fJi1~'l-tt i;itli!i'f;l11 n11~~f;) YlU~1~ fil'l1>J~-3,,tl-3 weir L~m nu i!if.fl11m1i. i-lfl~1 L Yl1!::"lltl-3

n~U,,'il>l'il1n1f'I 80 % iJi!if;)11~'Ju1:::~~1'3'fl~-3-:J1Utl3l.J.fJi1~'l-D'r;Jtit3'i;i11mrn~r;i~1~"1 Lri'i.lV.r.i11ru1

~Pl'J1).J~-:J'IJ'iN weir 1::'.~UfJl1'3 1 ~-3 Fig. 9 'tlU~1 Lri'i.lPl'J1).J~..:JL ~).J~\..ln111-if 'fli'1'31U'"l:::~1fl'1 LLr;i L~'Cl

L~>Jfil'l1>J~-:JLU'l.J. 13 cm 'tlU~1m1'loif 'fli-:J-31'1.J.n~rn~>J~>l~U ~>ltl1"'HCtl-3"'l1 n~111'J:::tl1n1f'IL 'W

.... tl-3tllJLLl-°l'liil'l'l1l.J~\..IL ~).J~\..lci..:J~fl 'l l-°l€ (1111 n11'ilU LLl-°l..:ion 1fl'1~..:J!Jitl..:iL'if L'lfl1 L \..ln11tlU LL .... '1l.J1 n~\..I ~'1 .. .. ..r ~ULUfl'il-3 'fl i>l'11U).J1 n"ll'U

n11tlULL,_.'1~~1l1'l:::fil'l1).J~'3"llt1'1 weir 10 cm i!it;J11n11li-lfl'El1n1f'l~1L't11!:: 0.043 kg/s-kg dry

matter .a'1111m1~).J\..1Ltlt.1WniKu BO % LU\..l~1111:::~ L~l.J1:::~l.J~11.1i'u m1~1 ~ il-um1'ClULL"'..:i L ~tl'l'"l1 n ' I lf I I.I

~tr f;)11~'l'l.J.1:::~11~'tl ~'1'11UVJ1on1:; L ~[J tl1 lJltltl (;111m1~ ~i;ilii1 ~ "1 L"1t.J'"l!::~\..ILU~'iN.,.. ~'3'11'1.J.U j).JIJi'j

7 .9 MJ/kg-water LLU~LU'U'tl~'1'31UL~Vi1'l 'l.J.lU"ll'B'l'fliK..:i..:i1ut13).Jf,]i'j 31.1 % (2.46 MJ/kg-water)

'tl~-3'31\..lfil'J1).J1tlu 68.9% (5.44 MJ/kg-waterl LLfl:::€i;i11~'l\..11:::~~1'1'tliK..:J'11\..IUj).Jl,]i'.ir;ltl'Ci'i;i11m1

~~f;)LVhnu 3.0 (MJ/kg-waterl /(kg dry matter/min) L'l.J.~1l1'l~n11'Cl1JLLi:i-3dr.i~iili'l1'l;r.h£J 2.05 lJ1'Vl/

11

i1 .; OJ .; .,

1Tn'l'11 nn. n 17 ,:iuun 2 li'U11Ylll 2537

nfanfi.1tl1~'1:::L~tJ ;j~LlJuf'i1'l<!~1tJL'Un11~11..iLri1'1l..i 0.99 U1Vl/nfanf)Jtl1~1:::L,,.tJ ri1'l.n'~1tJL'U m1vi1L\lum1'l un1ru1.ifJ1>JuLLJ11LU'UL~il L w~..i 1 .06 U1Vl I nLflnf)JJ1~1::;mu n1'l.ifJ1>Ju~ L'llfl

' " ' f'i1'l.if~1u'lun11vi1LU'Un11,,:::L~"LU'U 1.61 U1Vl I nLflnf"i.hVi1:::L,,.tJ

m1~,,~~L,,.~-n::;~"'lum1vi1LU'Un11'1lULL,,;'1~~ n.l,,.1Ji11l'a'1'Cl1n1Pl 115 °c Y'lUtl1~'ii'(l]'11n1'1 ',,.a~1 L Y'l1:::'iJ'a'1mn1P1~1 ,,::;~'ULU~'a'1Y'li'1'11'U~1 LLfl ::;~ti' (1]'11 n11,,."'ULtltJ'Un iU'iJ'a'1'a1n1Pl LLfl::;

' fll'l1i.1~'1'!l'a'1 weir L ~ i.i~u.,::;v'h 'l ~iuLtJ ~'il'1Y'li'1'11'Ufl~fl'1 n11'aU LL~'1L 'U~1111:::~fll'l1i.1~'1'il'il'1.ft'u weir 10 cm tll'l11n11h~fl~1LY'l1:::'il'il'1'il1n1f'I 0.043 kg/s-kg dry matter l'l'l1iJL1'l'il'il'1'il1n1PlL'ULU~

2.3 m/s LL~:::ti'l'J11n1'1,,.~'UL~uummfl!niu 80 % li116l'!11ri1u1::;,,.-l1'1Y'li'1..i1u~'l.if1:::L,,.utl1"1'il ' "

t1i;i,1n11t:.1~l'li;'hq~ t~u.,::;~uLtJfie'1Y'li'1'11utJ :i.i.r;ii'.l 7 .9 MJ/kg-water LLti'1LUUY'la·N1uh'lrh1 u

itJ'ile..iY'la'1'11t.1tJ3i.1.r;in 31.1 % 12.46 MJ/kg-waterl Y'li'1'11Ufil'l1iJ1'au 68.9 % 15.44 MJ/kg­

waterl LLfl:::'ii'm1ri'lU'1:::,,.-l1'1Y'la'1'11'UU3"1Ji'.l1'i'ilti'l1111n11f..1~111LVi1riu 3.0 !MJ/kg-waterl I (kg dry

" " ' matter/min) 'lu~n11::;m,euu~_,il.,::;~l'i1'lf~1t1 2.os U1Vl/ nLfmfi.iu1Vi1:::L,,.tJ LLt1mtluf'i1~11'1

Lfi1°4'il'1 0.99 U1Vl/nLflnfi.1tl1~1::;L,,.tJ ri1'l<D~1u'lun11vi1LO'Un1'l' (L'Un,ru'l<Dtl1>JuLmLi'.l'UL~'ilLY'l~'1) " '

1.06 u1wiit~nfi.1il1Vi1:::L,,.u

A1 "II 'il \.J Fl N •

~ L~tJt.ILflli'il'a LL~ ~'1 rl'l1 iJ'iJ'ilU ~ rulii'il~111tl4' tJ LL 'IA-l"ll 1~ LL fl:::~ 1i.!n'11.JU'1:::i.11 ru~'l ~fil'l1"~i.ru ~11'ULfllNn11~4'ud LL~::; Australian Centre for International Agricultural Research ~i'liJ~UUf111t.I

12

!1.1 ... .I ... 1TH'l'l'i t'f'\111. uVI 1 7 ~UUVI 2 1iU11fllJ 2537

"' ... L 'il n ft1 'i'il'N'iN

... fl\.1~1.

2. 'fl1'flt.i~P1 f'l1~'l1VI~~. 2536, m1~m:t1m1'fJULLiX~il1'lLU~'fln LV!tJ'lti~~~vi LVliLUVltlth.:J

!il•m titN, 'lviu1u~t.1fit.l'foJru 1'lf'l'l nni.i Pl 1 fl (;ln,1~111rusn111 l"l ru::~ Pl'l mm ia11ei i;if ... 'i' 'i' "" ,, ...

t'ltl1U\.ILVll"l •t.li.~U~1~'*4'fli.JLn~1!!\.1~1.

3. Giner, S.A. and De Michelis, A. 1988, Evaluation of thermal efficiency of wheat drying in

fluidized beds, The British Society for Research in Agricutural Engineering Journal 41, 11-23.

4. Page, G.E.1949, Factors Influencing the Maximum Rate of Drying Shell Corn in Layers,

Unpublis~ed Thesis For the Degree of Master of Science, Purdue Univ., West Lafayette,

Indiana, USA.

5. Satayaprasert, C. and Vanishsriwatana, V. 1992, Drying corn in fluidized bed, Thailand

Engineering Journal 44(2). 76 - 79.

6. Soponronnarit, S. and Prachayawarakorn, S. 1992, Maintaining quality, maximizing throughput

and minimizing energy comsumption in fluidized bed paddy drying, Proceedings of the 15th

ASEAN Seminar on Grain Post-Harvest Technology, Singapore, Also accepted to be published

in Drying Technology, 1994.

7. Sutherland, J.W. and Ghaly, T.F. 1990, Rapid fluid-bed drying of paddy rice in the humid

tropics, Proceedings of the 13th ASEAN Seminar on Grain Post-Harvest Technology, Brunei.

8. Thorpe, G.R. 1987, Thermodynamic performance of continuous flow fluidized bed grain

disinfestor & drier, J. Ag. Eng. Research, 37(1 ), 27 • 40.

9. Tumambing, J.A. and Driscoll, R.H. 1991, Modelling the performance of continuous fluidized

bed dryer for pre-drying of paddy, Proceedings of the 14th ASEAN Seminar on Grain Post·

Harvest Tech~~ogy, Philippines.

10. Wilhelm, L.R. 1976, Numerical calculation on psychrometric properties in SI units, Trans.

ASAE. 19(2). 318 - 321,325.

13

:'I .,j ., ... ., 111n11 nn. uVI 17 ~mm 2 11u11f1JJ 21>37

CV2 02

______ j _____ t ____ _

r------------,

I_ -I - - - t ...___-_-___,-1 lf 1 Wt1 I

I I M, .__ ..........,_.__.___,_ __ ...._. ___ ---i: _i~

l-1---r---t, CV1

I I

l -i- J

CV3

Fig.1 Control volumes of continuous cross-flow fluidized bed drying system.

I )- -

/

t T mix ,w mix

M. in

Fig.2 Control volume of the thin layer i.

14

IF i < n

!"I ..I ., ..I ., 1ll\Y1l l'l'H. UY! 1 7 '1111JYI 2 TiU11tUJ 2537

( START)

INPUT DATA: V, F, AC, h, m mix • T . ,T ,T ,W ,M. ,P mix 1 wb 1 1n

CALCULATE: mean residence time

CALCULATE: t, m mixx ,hp><

w,1,assume =0 ·02

CALCULATE: T 11

,W 11

CALCULATE: energy consumption

c STOP)

W =W f1,assume f1

IF abs[W • W ] >0.00001 f1 ,assume f1

Fig.3 Computer simulation flow chart.

15

~..I ., ..I .... 11'H'fl') ff'ilti. U'YI 17 iltltl'YI 2 'li'U11fllJ 2537

120

1: experiment result 2: simulate result

-0.36 100

:LJ

2 -a

* 6 80 +-- 0.31 -c: Q)

Q) c ..__ 2 C>

"' 1 (_)

Q5 Q) ..__ a.. 2 E 2 0.26 en ~ 60 ·5

E ~ c: u::

40 • 0.21

20 -+---~--~--~----------1-0.1 6

80 1 00 1 20 1 40 1 60 1 80 200

Mean residence time (s)

Fig.4 Comparison between simulated and experimental results of air temperature and paddy moisture content.

{ initial moisture content = 28-30%db, inlet air temperature = 115 C )

' 16

!'II .. ., .. ., 111n11 ttn. urt 17 QUUYI 2 11'U11fl1l 263 7

120

110-

100--';/!. 90-.

0 . . - .... • "C 80-

(jj ·:;. 70-"'CJ . • • • cu 60- ••• CD .c 50-CD

.i?: - 40-cu

30-(ii a:

20-

10- i I I

0 I I I I I I

12 14 16 18 20 22 24 26 28

Final moisture content ( %db)

Fig.5 Relationship between relative head yield and final moisture content of paddy (temperature = 115 C).

120-

110-

100 - + t~tJt, =I= - + *- 90- + $ ~fJt - + + + (/) 80-(/) + CD 70 -~ c CD

60--.c ~ 50-CD > 40-:;;; «I 30-(jj a: 20-

10-

0 I I

12 14 16 18 20 22 24 26 28

Final moisture content ( %db)

.Fig.6 Relationship between relative whiteness and final moisture content of paddy (temperature = 115 C).

17

!!'I... u ... u 111't'l'U t'l'H. UY! 17 Q1J1JYI 2 1lU11flll 2537

10

14-

SP=Specfic air flow rate (kg/s-kg dry matter) V =Velocity (m/s)

~12 1: SP•0.030, V• 1.7 a i 2: v .. 0.043, v-2.3 . O>

~10-::::?: -c: .Q a.. E :::J U> c: 0 0 >-O> ..... Q) c: Q)

>-..... cu E

·;;:: 0..

2 -6

8 ~1

6 4

2 ~ 4

2

2-

0

~ " ~ ~ ro ~ ~ e ~ ~ 100

Fraction of air recycled (%)

Fig.7 Effect of fraction of air recycled and specific air flow rate on primary energy consumption and drying capacity, weir height= 1 O cm.

18

c :€ ..... Q)

:::::: cu E >-.....

"C O>

..:io::

~ -·u cu a. cu 0 O> c:: ·::;.. ..... 0

~~ ., ~ ., 11'Hfll ll'n. u'rl 1 7 UUU'rl 2 1iU11fl1J 2537

SP""specific air flow rate (kg/s-kg dry matter) V =velocity (m/s)

1: SP,,..0.030, V=1.7 2: SP=0.043, V=2.3

2

50 55 60 65 10 75 eo B5 eo e:s 100

Fraction of air recycled (%)

Fig.8 Effect of fraction of air recycled and specific air flow rate or1 primary energy consumption to drying capacity ratio, weir height= 10 cm.

19

:o1..I ... ..i ... 11'H'l'l'.i t'f911. u'rl 17 QlJUYI 2 1i'U11fl1.J 2537

15- SP= specific air flow rate (kg/s·kg dry matter) H = weir height 1 : H 4cm,sp=0.115 2 : H = 7cm,sp=0.060 3 : H =10cm.sp=0.043 4 : H •13cm,sp=0.033

.._ 4

2 3

8

0 0 oo ~ oo ~ ro n oo ~ ~ ~ 100

Fraction of air recycled (%)

Fig. 9 Effect of fraction of air recycled and specific air flow rate on primary consumption and drying capacity ( bed velocity=2.3 m/s }.

20