NGHIEN COfU - TRAO D O I
NGHlfiN CUtJ TINH T O A N THIET KE BUONG DOT TRAU H O A KHI QUY JViO NHOSU" DUNG CHO H O GIA DINH N 6 N G T H O N
RESEARCH AND DESIGNING A GASIFIER STOVE WHICH USE IN THE RURAL FAMILES
TS. Bui Trung Thanh', TS. Nguyen Van Tuyen^ KS. Le Dinh Nhat Hoai^
'Khoa Cdng nghe Nhiet lanh Dai hpe Cdng nghiep Thinh phd Hd Chi Minh
^Bp mdn Cdng nghe Nhiet lanh Dai hpc Bach khoa Thinh phd Hd Chi Minh
^Trung t i m R&D Tech Dai hpe Cdng nghiep Thinh phd Hd Chi Minh
TOM TAT
Trau thdi Id mdt loai chdt ddt thdn thudc vdi ngUdi ddn ndng thdn d Viet Nam. Ta thudng nhin thdy tUng dong trau Idn sau cdc nhd mdy xay xdt. Thdng thudng trau dUde sU dung bang cdch dot chay trUc tiep trong cdc Id ddt truyen thdngdecdp nhiet diingcho ndu an tronggia dinh, nunggqch, sdy ndngsdn.. .PhUdngphdp dot trau chay trUc tiip trongbuongdot tdn tai nhieu nhUdc diem.
Trongbdi bdo ndy, tdcgid trinh bdy phUdngphdp dot trau mdi bang cdch chuyen doi nhien lieu ran thdnh khi hod vd Ungdungnguyen ly khi hod ndy de tinh todn thiit ke mdt loai buongdit trau hod khi nguyen lydot nghich quy md nho, dUdc Ung dungdUdi dang bip dun tronggia dinh ndng thdn nhdm khae phue ede nhUde diem cua loai hep dun truyin thdng.
Bip cd cdc thdng so ccf bdn:
- Dudngkinh buongchUa trau: 250mm - Chieu cao buongchUa trduphdn Ung. 600 mm - The tich buongphdn Ung: 0,03m3 - Jongchiiu cao cua b^ dun: 900mm - Cdngsudtqmt: 65W
- Cdng sudt cda buong dot: 6,4kW.
ABSTRACT
Rice husk is a kind ofbiomass which is very much common in the rural re^on of Vietnam. We can see piles of rice husk at the back of the rice mill Normaly rice husk uses as fuel to cook in families, brick furnaces and grain dryers.
Rice hud: is directly burned in the traditional stoves. The direct burning method has disadvantage.
This paper present a new rice husk burned method. Rice husk converts into carbon monoxide and hydrogen by reacting the raw material with a controlled amount of oxygen. This new called gasification method
It is based on nutrition demand of each meal for members in the family, the author calculates and designs a newgasfier stove which uses rice husks as fuel The parameter of the stove such as:
- The diameter of combustion: 250mm - Heigft of reaction combustion: 600 mm - The volume of reaction volume: 0,03m3 - The toted of height of the stove: 900mm
- Capacity of fan: 65W ^^
- Capacity of combustion: 6,4kW.
T< n r i T f r - r i i r u f ^ri^j NAM *l* Sd 7 (Thing 7 nam 2012)
NGHIEN ClJfU - TRAO D O I
I.DAT VAN DE
Trau thii td cic nhi may xay xit li mpt loai chat ddt rai quen thudc vi gan gui vdi ngUdi ndng dan ndi chung trong ci nuue, die bivl li ndng din d vung ddng bing sdng ("Uu Long. Trau chu yeu dupe sd dyng de nau in d gia dinh, mdt sd thi dupe dung de ddt nung gach d cic xudng sin xuat gach ngdi, sd il khic ihi dUpc diing trong miia say ndng san, nhieu noi thi phii ddt bd do ed qui nhieu.
Trau li ngudn chit ddt co sin ngay tai cic diem xay \al gao tgi cic ling que d ndng thdn, re tien. Trau la loai nhien li^u de chay, khi ning sinh nhi?t tdt. 1kg triu khi ddt ed the sinh ra nhi^l lUPng khoing 3000 keal, bing 30% nhi?t lUpng dau DO va 25% -27 % gas LPG, nhUng gii thi lai thap hpn tii 20 lan den 25 lan.
Ddi vdi trau lam chat dot dun nau trong gia dinh thi tU trUde den nay, ngUdi ta chi cd mdt each duy nhat la ddt trau chiy trUc tiep trong cac bep dun truyen thong. Thdi gian gan day tai mpt so dia phuong eua Ddng bang sdng Ciiu Long, ngUdi ta ep trau thinh eae thanh cui triu de tien dung hpn trong van chuyen va ton trijf de dun nau, tuy nhien viec ep thanh thanh cui lai lam chat dot re tien nay trd nen dit tien hon, nhieu ngUdi din khd tiep can sd dung loai nhien lieu mdi niy. Ngoii ra, viec dau tU mdt may ep trau thinh thanh cui eung rat dit tien, dong thdi edn phai ke den dp tin cay ciia mdt sd cum eiia miy ep dim chUa cao, thudng xuyen hU hdng vit ep.
Trong bai bao niy, tic gii trinh biy phUPng phap dot trau mdi bing each chuyen ddi nhien lieu ran thanh khi hoi vi Ung dung nguyen ly khi hoa nay de tinh toin thiet ke mdt loai budng dot trau hoa khi quy md nhd dUpe Ung dung dUdi dang bep dun gia dinh, nham khic phue cic nhupe diem cua loai bep dun truyen thdng, ning cao khi nang tien dung trong sit dung ngudn trau thii d ndng thdn phue vu viec nau in hing ngiy
vi cd th^ cap nhi^t cho cic muc dich khic dU6i dang cip nhitl quy md nhd d khu vUc ndng thon.
2.n0I,lfiU VA PHL/ONG P H A P 2.1.Gidi thi^u bep dun truyen thdng
Cae ki^u bep dun triu truyen thdng co cau true lUPng ddi dPn gian. de che tao, gii thanh thap, ngUdi dan cd the tU lim dUpc, tuy nhien cac loai bep dun niy khi dun nau ludn sinh nhieu khdi kem theo, hi?u suit cip nhi^t thap. Trong qui trinh dun niu thUdng xuyen phai cd ngUcfi einh gidi vi phii cap triu vio budng ddt.
Do cich cap trau vio budng ddt li dang hd nen thUe pham trong dun niu ludn bj nhi^m bui trau vi cd miii khdi. Hinhl. Gidi thieu mot sd kieu bep ddt trau ehiy trUe tiep thUdng gap d ndng thdn vimg Ddng bang sdng CUu Long.
y ^ . ^ . . i M
ii
Hinh 2 Cut trtiu va than trau ep vien diing cho cdc bep dun truyen thong.
2.2 Tim hieu ve trau
Trau la Icfp v6 ngoai cung cua hat liia ^ duoc tach ra trong qua trinh xay xat. Mot kilo- gram Ilia khi xay xat co the cho ra 200- 230gto trau (chiem khoang 20%-23% tong khoi Um hat Ilia, c6n lai khoing 77-80% la thanh phan g?o, tamvacam)[ll
TAP CHf CO KHl VIET NAM S6 7 (Thang 7 nam 2012)
NGHIEN CtfU - TRAO D 6 I
H 1" -
Hinh S.Cdc sdn plidm thu dUdc tit xay Ida Bdng 1: Thdnh plidn cua trd'u (3}
Kich c8 2,5 - 5 m m
Nhiet tri 12,5 - 14 mj/kg
T h i n h phan hoa hoc (% KL)
c,„
35,77 H,„
5,06
s„.
8,08 0,,- 31,6
N,„
8,32
w,.
8,05
\
3,12 Trong vd trau chUa khoing 75% chat hiiu
ca d l bay hPi, chung se chiy trong q u i trinh ddt vi khoang 25% cdn lai chuyen thinh tro 12]. Chat hiiu eP ehiia ehu yeu trong trau cellulose, lignin v i hemi - cellulose (90%), ngoii ra cdn cd them thanh phan khic nhU hpp chat nito v i vdcP. Chat Lignin chiem khoing 25-30% va cellulose chiem khoing 35-40%t7]. Cic chat hflu eP eua trau la cic mach polycarbohydrat rat dii nen hau het cic loii sinh vat khdng the sd dung tnic tiep dupe, nhUng cic thinh phan nay lai rat d l chay do viy trau dUpc dimg lim chat ddt.
Sau khi dot, trong tro trau cd chUa tren 80%
la silic oxyt, khoang 15 den 20% tro. silie oxyt li thanh phan cd the dUpe tai sU dung trong rat nhieu linh vUc khic nhau trong nginh Vat lieu xiy dUng [5]
Hinh 4. Vd trau
Trau cd khdi lUpng the tieh (pb) 100 -r 120kg/m3. Nhiet tri thap khoang 3000 kcal/kg khi chay 11] [3]
De dot chay hoan toan 1 kg trau trong dieu kien binh thudng, ngudi ta phai cung cap cho trau tU 4,3 -^ 4,7kg khdng khi [l]t6]
2.3 Cac phan ling hda hoc xay ra trong q u i trinh nhiet phan hda khi
Trong mdt budng ddt hda khi, cic nhien lieu ehda carbon trai qua nhieu qui trinh khae nhau:
Q u i trinh nhiet phin xiy ra khi nhien lieu dupe nung ndng len, chat d l bay hoi thoit ra vi than dupc giii phdng ra. Q u i trinh niy phu thude vao tinh chat, thinh phan va cau true cua nhien lieu, sau dd se trii qua eic phan Ung khi hda.
Q u i trinh dot sinh ra cac sin pham d l bay hoi v i than d^ sinh ra khi CO^ v i CO.
Qua trinh khi hda xiy ra khi than phan Ung vdi COj va nUdc de sinh ra CO va H^ theo phan Ung:
C + H O - > H + C O ' ^ erf KHf VTET NAM •t* Sd 7 (Thang 7 nam 2012)
NGHIEN COTU - TRAO DC!)I
Ngoii ra, khi CO dat ean bing rat nhanh khi nd phan Ung vdi nUde d nhi^t dp trong budng dot hda khi. Dieu nay lim can bing ndng dp ciia khi CO, hdi nUdc, C 0 2 va H2.
Ve b i n chit, mpt sd lUpng ban ehe oxy hoac khdng khi dUpe dUa vio budng ddt hda khi de cho phep mpt sd cie nhi^n li^u hflu cP dupc ddt chiy de sin xuat CO va ning lUpng dc cic p h i n Ung lien tyc sinh ra hydro v i bd sung C 0 2 I5|
Cdc phdn ting toa nhiit:
Phin Ung chiy:
C + O^ -> COj - 401,9 kj/mol (1) Phin Ung oxy hda khdng hoan toin;
C + 1 / 2 0 . - ^ CO (2) Phan Ung Metan hda:
C + 2H,->CH^ (3) Phan Ung luin phien khi - nUde:
COj + Hj ^ CO + Rp - 42,3 kJ/mol (4) P h i n flng Metan hda tU CO:
CO+3H, ^ C H ^ + H p - 205,9 kJ/mol (5) Cdc phdn Ung thu nhiet
Phin flng C va hoi:
C + Hp -> CO + H^ + 122,6 kJ/mol (6) Phan Ung Boudouard
C-h 0 0 ^ ^ 2 0 0 + 1 6 4 , 9 kJ/mol (7) Cac phuong trinh (6), (7) li cac phan Ung
chinh cua q u i trinh khfl, cho thay r i n g nhi^t Iflpng se giim xudng do phai cung cap nhi^t cho p h i n flng nen nhiet dp cua ddng khi hda se giim dan trong sudt qua trinh khfl. PhUPng trinh(4) dupe gpi l i phan flng can bang khi - nfldc (phan Ung luan phien khi - nfldc).
Ve mat ly thuyet, doi vdi mdi nhi^t dp, ti sd gifla s i n pham cua CO v i H ^ v i san pham cua CO^ v i Hj l i co dinh va b i n g gia tri can bang khi - nude khdng ddi. Trong thUe te, t h i n h phan cin bang cua khi se chi dat dUpc trong trUdng hpp tdc dp p h i n flng va thdi gian cho p h i n flng l a d u [ 5 ] .
2.4. Nguyen 1^ ddt trau h o i khi 2.3.1. Buong d6t nguyen ly thuan
Nguyen ly ki^u ddt thuan (Downdraft gasifier), khdng khi cap tU tren xuong vi di ciing chi^u vdi chi^u djch chuyen cua trau nhi^n li^u.
Trong nguyen ly niy hie in tao ra se di theo d6ng khi tfl trdn xudng, ludng khi chinh se di qua viing oxy hda eiia budng ddt hda khi, h i e in bi chay va keft qud li vi?e chiy sach. (ias dflpc tao ra til qui trinh h o i khi se dUpc ISy tfl day budng dot. Nhit vay ddi vdi budng ddt nguyin ly thu^n, nhignli^
se dupe nap lien tyc tai dinh cua budng dot.TrSn dudng di xudng, cic t h i n h p h i n cua trau nhien li^u li^u phii di qua vimg nhi?t phin (tang than) v i dupc chuyen t h i n h cic khi H2,CO.C02 va CH4, cic t h i n h p h i n khi lao ra nay se tuy thupc vao nhi^t dp cua vung ndng v i thdi gian ma hd h i e in di qua.
Loai budng ddt n i y cd Uu diem:
- Kha nang tao ra ddng khi hda khong chUa h i e in (tar-free) se thugin Ipi cho vi^c cung cap nhien lieu khi h o i cho cac ddng cO no (ner flng dung cap nhien lieu cho ddng cP no sau kh d i lim ngupi, Ipe va tieh tap chat theo tieu chuan)
1 M.
m
l-CiiaciipnhiinlifK 2-Vung sdy.
3- Viing diilngcit! ~|
4- Ddy Id;
_ _ 5'Khdng khi vim 1 6-Viing kh^
1 7-Ghi Id;
a 1 8-Gasra;
1 9- Phin chUa tro:
1 10- Trau.
I | 11-Vimg nhietphtK 12-Viing diHamnH
Hinh 5. Buong dot hda khi nguyen ly thudn ddng[5i - Kha nang lim sach hac in cao cd the dat 70- 80% [5] Do lupng hac in da bi chay het khi di qua viing chay.
I
- Q u i trinh hinh t h i n h khi dpn gian * Tuy nhien loai budng ddt nay cd n h # di^m:
TAP CHf CO KHf VIET NAM • Sd 7 (Thing 7 nam 2012)-
NGHIEN COfU - TRAO D6\
- Kha nang hda khi cho mdt sd nhien lieu sU truyen nhi?t ddi Iflu cUdng bfle va bfle xa m i khdng qua xU li trfldc se kem. Dac biet li cie tU nhflng vimg thap hon d ben dfldi. Hac in nhidn lieu cd mat dp thap se lim phit sinh eic van (tar) v i eic chat de chay se cung dich ehuyen de ve ddng ehiy va tdn i p q u i nhieu. theo ddng gas. Tro dupe lay ra ngoii tfl d i y eua budng dot hda khi. Budng ddt nay cd Uu diem - Loai budng ddt n i y cd h i m lUpng tro cao
hPn budng dot theo kieu nghich. . Dpn giin, gia che tao thap.
- Budng dot loai n i y cd hieu suat thap hon budng dot kieu nghich do thieu trao ddi nhiet ben trong ciing nhU gii tri nhiet cua ddng khi hda.
- Khi nang chiy eiia tro cao.
- Hi^u suat sinh nhiet eua thiet bi cao.
- Vdi loai budng dot niy yeu cau can thiet Cd k h i nang hoat ddng vdi nhieu phai duy tri nhiet dp ddng deu cao tren tilt dien i^^^ nguyen lieu k h i c nhau (mun cUa, vd ngu chiy- cdc...).
- Yeu cau ham lupng i m trong nhien lieu . ^ 6 the sfl dung nguyen li?u smh khdi dUa vao khi h o i phai thap ^^i ^^^ ^^^^^ ^^ ^^ ^^^^^^ ph^n vd cP cao [5]
- Khi thoat ra d efla budng dot hda khi cd Loai buong dot n i y tdn t^i mdt sd nhupe nhiet dp cao, can ed he thdng thu hdi nhiet. diem nhU-
- Loai budng dot niy cdn tU 4 -^ 7% ham lupng carbon khdng chuyen ddi het.
2.3.2. Buong dot nguyen Iy nghich
Budng dot nguyen ly nghich edn gpi (budng dot Updraught gasifier). Ddi vdi loai budng dot nay thi cic hat nguyen lieu chay chu yeu d phan d i y buong dot.
1-Ola c^p nhiSn b^u;
* , 2-Gas ra;
Hinh 6. Buong dot hoa khi nguyen ly nghich - 15U2]
' Khdng khi vao budng ddt d phia dfldi va gas t h o i t ra d phia tren. Can d ghi budng dot c i c phan flng c h i y x i y ra v i cic p h i n Ung
*niy giam dan theo chieu cao ciia budng dot. 6 eac phan tren eua budng ddt hda khi x i y ra sfl tddt ndng va nhiet p h i n nguyen lieu v i o nhd
- C i e Id phan phdi khi d l bi oxy hda, v i cd the bi bit kin do eac keo nhfla, tar di qua. Do vay vdi loai budng dot n i y can phai lap dat thiet bi phan phdi khi dang rdi de d l d i n g thay the va lam ve sinh dupe
' Theo [5] gas dflpc tao ra tfl loai budng ddt nay cd chfla tfl 10 -^ 25% h i e in ( t i n h theo khdi lupng)
- Loai budng dot nay khuyen cio Iflu y den vile loai bd hac in neu gas tao ra dflpe dung trong viec cap nhien lieu cho ddng ed nd.
2.3.3 Budng ddt cd ddng khi cheo nhau Ddi vdi loai niy, thi ddng khi cap cho qua trinh chay trau trong budng dot di ngang vdi chieu dich ehuyen cua cdt trau n h i l n lieu.
Tai vung oxy hda trong loai budng dot n i y cd nhiet dp khi hda rat cao (cd the >1500''C[5]. Do vay vat lieu che tao loai budng ddt y l u cau chiu dUPe nhiet dd cao hon hai loai tren.
TAP CHf C O KHf VIET NAM •t* Sd 7 (Thing 7 nam 2012)
NGHIEN CUU - TRAO D O I
H);j/i 7. Budng dot hda khi c6 ddng khi cheo nhau [Sj
I- Citii flip nhfn li(u, 2- Viing sdy, 3- Vung chiing nil.
4- Viing khA 5- Gas ra.
6- Tro thay.
7- GftJ W, i- Viing chila tro.
9-Ddy Id:
10- Khdng khi vdo.
Budng ddt niy cd flu diem:
- Budng dot nay ed the van hinh d qui md nhd.
- Viec lim sach gas rat don giin (chi can ed mdt bd cyclone).
Tuy nhien budng ddt nay cd nhUpe diem li:
- Khi ning ehuyen ddi hac in thap - Yeu eau nhiln lieu cap vio vio ed chat Iflpng cao [5].
3. KET QUA TfNH T O A N THIET KE Tren cP sd phan tich thinh phan cua Triu thai, cung nhU dl' cap ve eae phan Ung xiy ra trong qua trinh dot trau hoi khi vi eac nguyen ly hoi khi, tic gii Ifla chpn nguyin ly hoa khi kieu nghich de tinh toin thiet ke budng ddt cip nhiet sfl dung trong dun nau cho hp gia dinh ndng thdn theo hfldng nghien cflu.
3.1 Xic dinh nhiet lU^ng cua buong dot cia cung cip 6i nau in trong ngiy
3.1.1. Tinh todn ndng lUdng cdn cung cap cho ngtfdi hdng ngdy
Ca sd tinh toan thiet k^ dflpe dUavaonhu eau cin cung cip ning Iflpng thdng qua vile dun niu thdc pham, dun nUdc uong trong mdi bu6i niu trong hp gia dinh.
*
Thdng th Udng theo khao sit gia dinh nong thdn trung binh ed 6 ngfldi vdi cip dp tudi phan bd nhu sau:
+ Hai ngUdi dp tudi tfl 30 - 60 + Hai ngfldi dp tudi tfl 18 - 30 + Hai ngfldi cd dp tudi 10-18
Thdng thfldng trung binh cfl mdi cap tuoi liet ke d tren li mpt nam va mpt nfl.
Tat ca mpi ngUdi deu thudc dang lao dpng trung binh. Theo[4l nhu cau dinh dUdng kien nghi cho ngfldi Vi^t Nam" thi nhu cau nang lUdng phai cung cap nhfl sau:
- Nam tfl 30-60 tudi can 2700 kcalo/ngay.
Viy nhiet lUpng: 5400kcalo - Nfl tfl 30-60 tudi can: 2500 kcalo/ngiy.
Viy nhiet lUpng can 5000kealo/ngay - Nam tfl 10-20 tudi can 2200 kcalo/ngay.
Viy nhi^t lUdng can: 4400 kcalo/ngay Tdng edng nhiet Ifldng can cap tU cac buoi an li 14800 kcalo/ngiy
Ta di tinh nhiet Ifldng cho tflng lan siJ dung budng dot trau hoa khi de dun nau an trong gia dinh trong moi buoi an.
TAP CHI CO KHf VIET NAM So 7 (Thing 7 nam 2012)_
NGHIEN ClJfU - TRAO D 6 |
3.1.2.Tinh liidngnUdc uong trong 1 buoi Theo [4]cfl 10kg thi' trpng can 0,4 kg nUde/ ngay. G i i sfl trpng Ifldng trung binh mdi ngUdi Idn la 55kg. Gia dinh gdm 4 ngUdi Idn vdi tong trpng lUpng la 220kg v i tdng trpng lUpng 2 ngUdi nhd 80kg (lay trung binh mdi ngfldi 40kg).
Nhfl vay ta tinh dflpe lUdng nUde can eung ci'p cho gia dinh trong 1 ngay se l i 12 lit. Ta phin bd mdi buoi nau 6 lit nfldc v i dUpc tinh toin nhiet Iflpng dun nau nhU sau:
3.1.2.1. Nhiet lUdngcan denau nUdc Ta gii sfl nhiet dp ban dau eua nude va cae thUc pham bang nhiet dp mdi trUdng t" = 28"C.
a. Nhiet Ifldng can thiet de lam ndng noi SU dung cdng thUc:
„ m,. cAt 10.13":
=Ii:Jkcalh
Trong dd:
Q ^ - nhiet Ifldng can thiet, kcal/h;
m^^ =1- khdi lUdng ndi, kg;
c = 0,13 (kcal/kg*'e) - Nhiet dung rieng eua vat lieu che tao ndi
At = 100 - 28 =72 - dp chinh lech nhiet dp trfldc v i sau khi nau, °C
' X = 5/60 - thdi gian lim ndng ndi. h;
•: (dfl kien l i m ndng ndi nau trong 5 phut)
T = 10/60 - Thdi gian nau nfldc, h (dU kien nau trong 10 phut)
3.1.3. Nhiet lUdng cdn thiit denau cdm
Sfl dung cdng thUe
Q,^:!LiJi.'-°;'-''-,|4S.6kc.ll.
T ]2_
60 Trong dd:
Q. - Nhiet Iflpng can thiet, kcal/h;
m = 1,2- Khdi lUPng gao can nau, kg; (can ni'u 1,2 kg gao cho 6 ngfldi an)
C=;0,43keal/kg"C - Nhiet dung rieng eua gao [7]
At =100 - 28 =72- dd chinh lech nhiet do trUde v i sau khi nau, "C;
T = 15/60- thdi gian nau edm,h;
(du kien nau trong 15 phut) 3.1.4. Nhiet lUdngcdn denau mon thit
Sfl dung cdng thflc
Q , = - ^ ^ ^ = —j^=;SS.8kcalh
r 10 3 b. Nhiet Ifldng can thiet de nau nfldc
Q r
60 Trong do:
:; Q^ - nhiet Iflpng can thiet, kcal/h s. m^ =6 - khdi Ifldng nfldc can nau, kg
c = 1 - nhi^t dung rieng cua nfldc, kcal/kg°C At =100 - 28 = 72- Dp chinh leeh nhiet dp :rUdc va sau khi nau,''C;
Trong dd:
Qii^ - nhiet lUpng can thiet, kcal/h m^^ = 1kg - khoi lUpng thit can nau, kg c = 0,9 keal/l^C - nhiet dung rilng eua thit [7]
At =100 - 28 = 72 - dp chenh lech nhiet dp trUdc v i sau khi nau, °C;
T = 10/60- thdi gian nau, h;
(dfl kien nau trong 10 phflt)
__ ^TXS^ui-cri i^of v r e x NAM V Sd 7 (Thing 7 nam 2012)
NGHIEN CtfU-TRAOeOi j
3.1.5 Nhiet liiging can de niiu m6n ran 3.2.2. Difdng kinh bu6ng dot
Ap dyng cong thilc: Dudng Icinh buong dot In • khi la doi kinh mat c4t ngang cua flng try noi irau bj chiyi Q_ = !!ll£rl = L_L^=60:.6kcal h hoa khi. Duemg kfnh buong dot co the dU()ct|[
theo |6|:
10 60
T.ongd6: Q . S . PMl.0.254,m) V B V 120
Q^-nhiet IU0ng can thiel, kcal/h; Trong do: * m =l,5-kh6i luong rau can n3u, kg
c = 0,93kcal/kg"C - Nhiet dung riSng ciia D-du6ng kinh ciia buong dot, m rau, 17| G„ = 6,1 - luong nhien li^u can thift, kg/h'
At =100 - 28 = 72- Dp chenh lech nhiet dp B '= 110-210- toe dp hoa khi riSng, k trudc va sau khi nau,"Ci m'h. Theo [2) ta chpn B= 120kg/m'h
T = 10/60 - thdi gian nau, h; (dU kien nau Xa chpn dUong kinh buong hoa khi D:
trong 10 phut). 0,250m Tong nhiet lUong can thiet sil dung cho nau an 32.3 Chieu cao cua buong dot
Q„.= (Q„o + Q, + Q, + Q, +Q.) = 3844.3 kcal/gid
Chieu cao cua buong dot hoa khi la toi^
Theo [6] nhiet luong can nau khi tinh Uj^jng ^^^-i, ,(j ^^„Yt den day buong dothoaUii toan can nhan them he so k do t6n that trong qua (j^'n mat ghi). Chieu cao dUpc xac dinh tion[
trinh nau va do each bo tri luc nau khong lien tuc. kh^j^g ,hdi gian buong dot hoal dpng khi n Chpn k= 1,45. Vay nhiet lupng ciia be'p cung cap ^ ^ , |j„ „|,i^„ ,j^^
cho mpt lan nau la: 5500 kcal/gid hay cpng suat
ciia bep la: 6,4kW. j ^ ^ G . T ^ 120.0,5 K 100 ' "
3.2 Tinh toan thiet ke bep dot .r. ...
3.2.1 Tinh liidng trau cdn tiap vdo buone dot hod n L--. . U - 3^
.., * H-chieu cao cua buong dot, m;
B= 120- Hf so khi hoa rieng, kg/m%!
T. .. . I. ^ . - , . . . , , . ^ T =0,5-thdi gian yeu cau chayhettrau.lt Ta tinh lupng trau can thiet la lupng trau
can cung cap cho bep dot cho moi lan dot: Si Pj, =100-khoi lUpngthetich traudSl^
dung cong thilc tinh [6] thai tU nhien, kg/m'.
G = - 2 s _ = J ! ^ = 6 , U h 3.2.4 T6c do chiy H\-,4, 3000.0J ^
Tdc dp chay la thdi gian can thift dlviuj Trong dd: chay di chuyen xudng phia dudi, dUdc tinh tbw
cong thiic:
G„-lupng trau can cung cap, kg/h H 0,6 f m l Q„=5500-nhiet lupng can denau, kcal/h ^ " T " o ^ " ' ' ^ T q„, = 3000 - nhiet tri ciia trau, kcal/kg ^ ' '^
\ = 30-hieu suat ciia bep khi nau %. Trong dd:
TAP CHl CO KHl V I £ T NAM • S6 7 (Thang 7 nSm 2012)_
NGHIEN COU-TRAO Ddi
H = 0,6 - chilu cao eiia budng ddt, m Theo [6], ton that dflpc tinh toin
^i T = 0,5 - thdi gian dot chay het trau, h;
ri-i N h u viy tde dd di chuyen khi chay hoa khi , y ''i /, n ^ I T / - . J z = 0,03cm/s h, = ( , - ^ . ( l + p . t ) , m m H p
.2.5 LUdng khong khi cdn thiit cho qud trinh khi °
od khi . V , , , , , , . V ,
i. v^ - van toe dong khi qua Ipp trau , m/s;
, , . , , , V , . .- s^ C - h i so trd Iflc eua Idp nhien lieu, C pbu LUdng khone khi cung cap cho buong dot ,, . . . - ..• r,' i J
1 1 1 . , . - « , V , . , , , , , thuoe vao chuan so Reynolds
nay lUdng khong khi can thiet cho qua trmh khi " . L - - . » - L - . . L - ^ . L - i L ' U • o,- /. , „ ° ° ^ t - nhiet dp ben trong thiet bl khi hoa, "C.
oa),m^/h: ° a.ij^^.A _ 0,35.6,1-4,5 _ g ^ 3 ^ _ Q QQ22it^\^s Vdi nhiln lieu la trau cd nhiet dp ehiy
u n^ 1,2 chiy trong pham vi tfl 700" C -^ 1400"C, eung vdi . , he sd trao ddi nhiet ddi lUu tU nhien eua khdng :: rong do: \diia = 0.2 -H 0,5) [6]. Ta ehpn tl = 1050°C.
a = 0 , 3 5 - H l s d q u y d d i k h i h o i k h i G =6,1- 1 1
upng trau can thiet, kg/h ' P - he so nhiet eua khi, p = ^ ^ ^ - ; A= 4,5- Iflpng khdng khi khi dot trau d
tieu kiln binh thfldng Tieu chuin Reynolds dupe xic dinh:
p = 1,2 - khdi luong rieng cua khdng khi, ,
:':g/m\ R e = ^ ^ , u
Nhu viy gii tri Q dflpc hieu l i Iflu Iflpng Trong dd:
•^:ua quat cap khi v i o buong dot.
d - dudng kinh budng tao khi, m;
i.2.6 Van toe khidi qua Idp trau u - dp nhdt ddng hpc cua ddng khi, mVs;
V - van tdc ddng khi, m/s;
Van tdc cua ddng khi di qua Idp trau trong
^ua trinh h o i khi. Tra bang dp nhdt ddng hpc trong cie sach Q g chuyen nginh, d nhiet dp 1050''C, ta tim dflpc dp - ^^^ITi^ "TTTTT^^^ =4,4cm/s ^^^^ d5ng hp^ ^fla khi u = 185,7.10* m=/s.
. ^ . 3 6 0 0 ^ ^ - ^ 3600 • ' 0,058.0,250 , 4 4 R e = - : ^ - - = 7 8 , 1 > 7
1 8 5 , 7 . 1 0 ' Irong dd:
Vi Re > 7 ( che dp roi) nen ta cd:
V - Van tdc cua khong khi xuyen qua Idp
nhien lieu,cm/s; i; = + - | " - 5 5 5 Q^ - LUU luong khong khi cSn thiet cho ' Re R e " ' 78,1 78,1""' qua trinh khi hoa, mVh; Vay trd lUc khi di qua Idp nhien lieu trong
< D - Dudng kinh budng ddt, m. thiet bi khi hda la:
3.2.7Xac dinh tSn thdt buong dot 0 048' 1
h = 55,5 ^ ^ i ^ (1 + .1050) =13,5 N/m^
De cd ca sd thiet ke quat cap khi cho buong ddt, trong pham vi tinh toan ta di xac dinh tdn that trong budng dot.
2 273 + 1050
. . TAPjC;v;^f<i<rm v i F T N A M V Sd 7 (Thang 7 nam 2012)
NGHIEN COfU - TRAO D O I
i
I
m
3
pu.iu ,'hi>au,.
,u,i,il)'khi:
Hinh 8. Bip dot Inui hod kin nguyen ly iighfch
con phii linh dcii tdn that cue bp khi sin, I h i l i o i d i q u a c a e k h e h ^ p d d i y l d , kenhdl .l.uii; dm thu vi dd md, co 90", vj tri re nhinl dudng di cua s.in pham khi den chd dunni d.ic bi?t qua ghi phan pbdi khi (vai trd lin phun khi) lai chd dit ndi nau tdn that ma si sin p h i m khi chay trin dfldng dng den vjtr sinh n b i | l dung cho nau an. •
Ngiy nh^n bii: 28/6/2012 Ngiy p h i n bi(-n: 04/7/2012
Ngudi phan bien: (iS, TSKH. Tran V3n Phu
Dfla trin cac nguyin ly hoa khi, nhu cau eung cap nang lUpng thdng qua vile dun nau eic khau phan thfle an trong gia dinh trong cic buoi an trong ngiy, tic gii da tinh toin thiet ke dupe mdt loai bep dot trau hoa khi theo nguyen ly dot nghich eung vdi eac thdng sd ky thuat
- Dudngkinh buong chfla trau: 250mm;
- Chieu cao budng chfla trau phan Ung: 600 mm;
- The tich budng phan Ung: 0,03m';
- Tdng chieu cao cua bep dun: 900mm;
- Cdng suit quat: 65W;
- Cdng suit eua budng ddt: 6,4k\\'
5. THAO LUAN
Cdng suit quat cung cap khi cho budng ddt cdn phu thudc nhieu den dfldng dng vi khoang each cung cap khi tU budng h o i khi den vi tri ddt khi de sinh nhi?t. Ngoai cac tdn thit do ddng khi qua Idp nhien lieu nhU d i tinh d trin thi
Tai lieu tham khao:
jlj. Bill Trung Ihanh.Thiet ke Id dot gas trau.n- loai miy say ndng sin. Co di|n khi hoa nong nil v('(i van de cdng nghi?p hoa hi?n dai hda nong ngi
& ndng thdn, Nha xuat ban Nong nghi?p thing 1 -1 l2l. Ph?m Hoang LUdng, Cng dung cdng ngh?khi sinh khdi cdng suit nhd de sin xuat nang lit(fa^
chi Khoa hpe & cdng ngh^ nhi?t - sd 74/2007 13]. Nguyen Thanh Quang. Ding The Hiing, ngh.- cflu thiet ko ch^ tgo h? thdng hoa khi than tang- djnh. lap *.hi cong ngh^ nhicl.so 9, 2007 [4]. Dao thi Yen Phi, nhu can nang lUpng khaupk^^
in hpp ly, Bg mdn dinh. trfldng Dai hpc Y Pham Ng«
Ihijch.
151. .Ami K. Rajvanshi, Alternative E n e i ^ in # cultural, vol 11, nimbka agricuhural research Insttut ,Maharashtra.lndia,1986, pages 83-102 (6l. Alexis T Belonio, rice husk gas stove handbool Central Philippine University - 2005
(71. Energy Efficiency Guide for Industry in Asia www.energyeificiencyasla.org.
TAP CHf C O KHf VIET NAM •t* Sd 7 (Thing 7 nam 2012)
