Cdng nghiep rimg
I/NGHIEN CUtJ XAC DINH MQT SO TINH CHAT NHIET CHU YEU CUA VAT LIEU COMPOSITE GO TREN MAY NL03
N g u y i n T h i Y e n
ThS. Truang Bai hpc Ldm nghipp
T O M T A T
Hfi so din nhi?t X la mpt trong nhihig dai lupng vat ly rSt kho xac djnh tinh chat, vific xac djnh dac bifit c4n thifit CO anh huong ldm den vific nghifin cuu, tinh toan thifit ke cac qua trinh thiet kfi ciing nhu thi cong san phim. Tren the gidi da c6 rat nhifiu nhihig nghifin cthi nham xay d\mg cac bang co sa dii lieu thuc nghiem ve hfi so din nhifit, tuy nhien do khic bifit vfi difiu kifin t\r nhifin nfin khi ap dung vit lifiu ciia Vifit Nam thi thuimg gjp phai sat so ldn, khong dli dp tin cay trong tinh toan ky thuat. Hifin chiing ta co mpt s6 may do hfi so din nhifit tuy nhifin d6i tupng do thu6ng la cac v | t lieu r5n, co h0 s6 din nhifit cao, khong chiia am va kliong bj bifin tinh khi thay d6i nhiet do.
Cac thiet bi niy kh6ng dap ling dupc yeu c3u xac djnh he so din nhifit ciia cac logi vgt Hfiu co he so din nhifit thip, cac vlt hfiu chua ham lugng Sm cao, Trong nghifin cuu nay chiing toi dva frfin nguyfin tic do ngudn duing xac djnh dupc hfi so dan nhifit ciia van xi mang A, = (0,203 - 0,233) W/mK va he so din nhiet din nhifit van vo trau X = (0,137 - 0,112) W/raK, hfi so din nhifit dp ciia van xi mSng a = (0,000108-0,000126) mVs, van vo trSu a = (0,000029-0,000042) mVs. Voi thdng so trfin thi hoan toan c6 the dap iing dupc la vat lieu each nhifit va may NL03 sii dyng xac djnh cho vat ii$u composite co he so din nhiet thap va chiia am.
Tir kh6a: Hf so dan nhipt, hp so dan nhift dp, vat lipu composite, vdn xi mang, vdn vo trau.
I. DAT VAN D ^
De phyc vy chuang trinh nghifin cuu ndy va phuc vu myc dich ung dung lau ddi trong tinh toan nhiet cua mfit s6 v|it lifiu. Chiing toi de xuat tim hieu vd nghien cihi thiet hi do he sfi ddn nhiet d ^ g cdm tay dua tren bai toan ngufin duang. Hi?n nay, chiing ta co rat nhieu cac phuang phap xac djnh h? s6 dan nhi^t khdc nhau. Cac phuang phap nay du^c chia lam 2 nhfim: nhom cdc phuang phap 6n dinh va nhom cac phuang phdp khong on dinh.
Phuang phap on dinh xac dinh h^ so dan nhi?t theo dya trfin trucmg nhifit dp 6n dinh nfin can thai gian cap nhi^t lau ddn dfin sy thay dfii ciia tinh chdt ciia vat lieu d^c biet la vdt lieu am.
Chinh vi vay, cac phuang phap do nhanh (phuang phap khong fin dinh) da vd dang dugrc nghien cuu dfi dp dyng trfin vdt lieu co he sfi ddn nhiet thdp. Mot sfi c6ng trinh nghifin cuu da xay dyng va nghien cuu thiet bi do he so dan nhi?t va ddn nhi?t dfi ciia cdc loai vdt Ufu c6 h? s6 dan nhi?t thap theo nguyfin ly nguon ducmg. Tuy nhifin, thiet bi do con cfing kenh, phai dat co dinh a phong thi nghiem nfin ban chfi ttong khd ndng sijr dyng. Cac sfi lieu thu du<rc chua dugfC tfing hgp thanh ca sfir d\t lifu, dp tin cay ciia thiet b} chua cao.
Trong nghien cuu ndy, chiing toi sfi de xuat
he so dan nhifit cua cac lo^i vat lieu co he sfi dan nhifit thdp tren co sfif ngufin duang, Nghifin cuu loai thifit hi do dang cam tay va quy trinh do, ddnh gid sai sfi ciia thiet bi vd nang cao dp tin c|y cho mpt sfi loai vat lieu
II. VAT LI$U, PHlTONG PHAP NGHIEN CUtJ 2.1. Nguyen/vat lieu thi nghiem
- Nguyfin lifiu: Van dam xi mang: kich thuac khac nhau chifiu rpng 300 mm, chifiu dai 100 mm, chifiu ddy thay dfii theo dung lupng mau 10 mdu vai kich thuoc chifiu day chpn (15, 16, 18, 19, 20, 22, 24, 26, 28, 30) mm. Van vo trdu: kich thuo'c khdc nhau chifiu rpng 300 mm, chifiu dai 100 mm, chifiu ddy thay dfii theo dung lupng mau 10 mau vai kich thuoc chifiu day chpn (15, 16, 18, 19,20, 22, 24, 26, 28, 30) mm
2.2. Thiet bi thi nghifm
- Mdy thiet bj: Thifit bi do he sfi dan nhiet NL03 Id thifit bj do hfi so dan nhift ciia vat lieu theo phuang phap ngufin duang. Thifit bi duoc cbe tao theo tieu chuan ASTM D5334 ciia My tai Phong Thi nghiem Bp mfin Kj^ thudt Nhift, Vifn Khoa hpc vd Cfing Nghf Nhift Lanh, Dai hoc Bach Khoa Ha Nfii.
mpt so gidi phap nham hodn thifn he thong do
TAP CHI KHOA HQC VA CONG NGHE LAM NGHIEP SO 4-2014 121
Cong nghiip rirng
23. Phmmg phap nghien cihi
De giai quyfit dupc myc tifiu va npi dung dat ra, dfi tai dupc thyc hifin bdng cac phuang phap sau:
- Phuong phap kfi thira: ke thira cdc nghien Clin ly thuyfit, cac tdi lieu, cong dinh nghifin cuu trong vd ngoai nuoc va kfit qud ciia cac dfi tdi lifin quan vfi cdc phuang phap xac dinh he sfi ddn nhift vd dan nhiet dp
- Phuang phdp nghifin cuu thyc nghifm:
thyc nghifim xdc dinh he sfi ddn nhifit va dan nhift dp voi cdc thi nghifim khdc nhau.
Dfi thyc hifn dupc toi sit dyng quy trinh cfing nghf nhu sau:
Van sau khi dpc cgnh cat theo kich thuac 300 X 100 X t (mm) vd dupc khoan 2 16 vai diwmg kinh miii khoan la 3 mm, each hai dau mpt khoang la 50 mm. Diing may kifim tra hf so dan nhiet cita van bdng each cho ddu do vao io khoan sao cho ddu do vira xuyen qua tam van. Cii" sau 10s thi ^ nhift dp lai mpt ldn, cho dfin khi nhiet dp do dupc sau 5 ldn lifin tifip tdng khfing qua 5%
thi tat may va tiep tyc ghi sfi lifu den khi nhift dp kh6ng gidm nOa. Chiing tfii tien hdnh kiem tra 6 nhift dfi phong vd sii dung tifiu chuan ASTM 5334 dfi kifim tra tinh chdt cua v?t lifu.
Qud ttinh thi nghifm dupc tien hanh theo ttinh tu sau:
Bu&c 1. Kfit nfii phich cam difin vao ngufin difn 220VAC. Bat Cong tdc 2 vi tri (Selector sang vi tti ON), nfiu thiet bi dd dugc cdp ngufin thi dong hfi do nhift dp DTA 9696 sfi sang.
Nfiu dfing hfi khfing chay, kiem tta \^\ ngufin difn vd 6 cdm.
Buac 2. Mdu vat lifu cdn xac dinh he s6 ddn nhifit dupc khoan 16 duong kinh 3 mm, do sau la 150 mm. Cac kich thuac ciia mau nen ddm bdo loTi hon 10 lan duong kinh lo khoan (tdng dp chinh xac cita phep do)
Buac 3. Cdm que tham vao lo dd dupc khoan sin, ddm bdo cho 16 khoan vira vfii que tham, tao difiu kifn cho vifc ddn nhift tir que thdm sang vat. Nfiu 16 khoan bi lon, cfi thg dung them bp MgO (magie oxit) dfi tang cucmg qua trinh dan nhift ndy
Buac 4. Quan sdt nhiet dp tten d6ng ho, day la nhift dp ban ddu cita qua ttinh do, nhi?t dfi ndy dupc ghi vao gia tri a thai difim r = 0.
Chudn bj sin d6ng ho bdm thdi gian, dua dong hfi vfi gid tri 0 gidy sau do bat dfing hfi chay cimg vai thcd difim bat khoa cap dien ngufin cho que tham. Su thay dfii nhift dp cua que tham dupc ghi lai sau mfii 10 giay.
UI. K E T QUA VA T H A O LUAN 3.L Ket qud do hf $6 d i b nhift cua vdn xi mdng Bang \. Ket qud dp hp so dan nhipt cda vdn xi mdng
Hf so dan nhift MW/mK)
Hf so dan nhift cua xi mdng Ket qud doi chihig (so sanh)
T^i lifu 1
2 3 4 5 6 7 8 9 10
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10
0,209 0,233 0,203 0,210 0,228 0,208 0,213 0,209 0,231 0,223
- Tam va ban xi mang amiang h^
s6 din nhiet X -(0,56-1) W/mK
[1],[5,61
- Xi mang he so (Mn nhi^t X =1
W/mK [3]
Xi mang c6t heu (KMIOSDA) cd Kiem dinh kich thuoc 220x100x30 mm, c6 he s6 cue phong dan nhiet X - 0,45 W/mK chay chSa
ch^y
TAP CHi KHOA HQC VA CONG NGHE LAM N G H I f P S 6 4-2014
Cong nghiip rirng Nhin vao bdng 1 cho thay van dam xi nang
la mpt lo^i vElt Heu cdch nhift, giu'a vdn ddm xi mdng so voi xi mang thi hf sfi ddn nhifit ciia van dam rat nho nguyen nhan Id do hf sfi ddn nhift phy thupc vdo rat nhieu cdc yfiu tfi nhu:
dp rong, khoi lupng, ciing nhu cau tnic cita vat lifu [5]. Hf so dan nhift cita vdn dam xi mdng ttong thirc nghifm cao nhdt la 0,233 W/mK so vdi tifiu chudn ASTM thi difiu nay co nghia Id may NL03 hoan toan co the xac dinh dupc hf Bang 2. Ket qud do he
so ddn nhift cita vdt lifu each nhift voi dp tin cay cao. He sfl dan nhift ciia v§t Hfu anh huong bfiri ba yfiu tfi: thdnh phan, cau tnic va difiu kifn ciia qud trinh. Thdnh phan nufirc cung dong vai tto rdt quan ttpng vi nuac chifim mfit ty le rat lan ttong thyc pham. Ngodi cdc yfiu tfi ttfin no con dnh hufimg cua dp dm, dp dm cdng cao thi he sfi dan nhift cang lan va nguoc lai 3.2. Ket qua do hf so dan nhift cua van vo trau
so ddn nhift vdn vd trau TT
1 2 3 4 5 6 7 8 9 10
Mau
2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10
H | so dSn nhiet X.(W/mK)
0,118 0,123 0,119 0,112 0,124 0,137 0,115 0,125 0,126 0,114
Uf so dan nhi|t ciia vo trau Ket qua doi chimg (so s^nh) Vo trau CO h? so dan nhi?t
>.=0,109W/mK
Tai li(U [4,5]
Qua bang 2 ta thdy khi xdc dinh hf sfi dan nhifit cua van tten may NL03 kfit qua cho thay van vo trdu co hf so dan nhifit lon nhat X = 0,137 W/mK va nho nhdt la 0,112 W/mK difiu ndy chung to hifu qud each nhiet tflt, co thfi sit dyng ldm vat lieu each nhifit tfit. Hf sfl dan nhiet ciia vdn vo ttdu so vdfi trau nguyen thi hf sfi cua van vfi trau cao hon trdu nguyfin nguyfin nhdn la do: Hf sfl ddn nhift cua thuc phdm dnh hufimg bfii ba yfiu tfl: thanh phdn, cdu tnic va dieu kifn cOa qua trinh. Thanh phdn nufirc ciing dong vai ttfl rdt quan ttpng vi nu6c chifim mpt ty If rdt lan ttong thyc pham. Ngodi cdc yeu tfl ttfin no con anh hucmg cua dp am, dp am cdng cao thi hf sfl ddn nhift cang lon va ngupe lai
Nhan xet: Nhin vao hai bdng 2 vd 3 ta thdy:
Khi xdc dinh hf sfi ddn nhift cua hai loai vat lifu composite van dam xi mang va vdn vo trdu thi hf sfl ciia vdn xi mang nam frong khoang (A,
= 0,203 W/mK - 0,233 W/mK) vd van vfl ttdu
ndm ttong khoang (k = 0,137 W/mK - 0,112 W/mK) nhu vay co thfi noi he sfi ddn nhift cua van xi mdng lom hom van vfi ttdu nguyfin nhdn Id do cau tnic ciia vdt lieu. Cdc yfiu tfi cau tnic bao gfim dp rfing, kich thuac, hinh ddng va su sdp xfip hay phdn bfi pha ttong vat lifu (khi, nuac, bdng va chat khfl). Cac yfiu tfi qud ttinh bao gflm nhift dp, dp sudt va dieu kien truyen nhift. Gid tti he s6 dan nhifit co the thay dfli theo phuomg vufing gfic hay song song ttong vat Ufiu.[2].
Ngoai ra con kfi dfin khfii lupng rifing ciia van vo trdu nho hom khfii lupng rieng ciia van dam xi mang md khfli lupng rifing nho thi dp rflng xfip ldm ddn dfin hf sfi ddn nhift nho va ngupi lai. Ben canh do cdu ttiic ciia vat lieu con kfi dfin cdu tnic ciia bpt xop nghia Id lo ngam khi cang nho min thi he sfi ddn nhift nho vi dong nhift dfli luu ttong vat lifu gidm.
TAP CHI KHOA HQC VA CONG NGH|: LAM NGHI|:P S 6 4-2014 123
Cong,
TT
1 2 3 4 5 6 7 8 9 10
nghiep rirng
MSU
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10
Bang 3. ^c/ qua dohfsS d&n nhi$t dp vdn xi mang vd vdn i He sS dan nhi|t dp a (mVs)
Viu 3d mang 0,000113 0,000118 0,00124 0,000114 0,000120 0,000116 0,000125 0,000126 0,000108 0,000108
Ket qua so sanh Xi mang co he s6 dan nhiet dp a = 0,00028 (mVs)
TH lifu [3]
MSu
2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10
f6 trau He so dan nhiet dQ a (mVs) Van vo trkn Ket qua so
siinh 0,000031
0,000032 0,000038 0,000042 0,000031 0,000032 0,000039 0,000039 0,000030 0,000029
Vo trau CO he so dan nhiet do
a = 0,0000101
(mVs) Tii ii?u [2]
Nhin va bang 3 ta thay: He sfi ddn nhiet dp ciia van dam xi mdng Idm hon hf sfi ddn nhiet dp cua van vfi ttau dieu nay hodn todn dung voi quy ludt ciia van cdch nhift vd tinh chdt ciia vdn each nhift phyc thupc vdo cdu tnic ciing nhu thanh phan cau tao nen vdt lifu.
Nhu vdy thifit bj NL03 la mpt ttong loai thifit bj dfing thai do dupc he sfl ddn nhiet va hf so dan nhift dfi cua vat lifu each nhiet. l/u diem ctia thifit bj gpn nhp, co thfi do ngay ttie thai t^i hifn truang phyc vy tryc tiep cho cfing nghf ehe bien cdc lo^i vat lifu cdch nhift IIL K£T LUAN
Qua qud trinh nghien ciiu di dfin kfit luiin:
Trfin ca sa phan tich danh gid hf sfi ddn nhift hifn CO va dfii chieu vai yeu cdu dat ra, dfi tai da lya chpn phuang phap do nhanh hay phuang phap do khfing fin dinh dya trfin bdi toan ngufin nhift d?ng duang. Dya tten co sa ly thuyfit vfi ngufin duomg da su dung thiet bi do gfim que thdm, bp xir ly va bp cdp ngufln. Cdc thifit bi dupc ehe X^o gpn nhe, dp chinh xdc cao, cho phep su dyng trong phong thi nghifm va ca
ngoai thyc dja. Kfit qua do ttfin mpt sfl lo^ vat lieu cho thay dp fln djnh va khd nang dp d\ing cua thifit bi do dfii vdi vat lifu composite, bdng sfi lieu thu dupc co dp tin cdy cao
TAI \A%\5 THAM KHAO
1. D^ng Quoc Phii, Nguyen Diic Lgi, Dinh Van Thu|n (2009). Che lao ditng cu do hf so ddn nhift ciia mpt so vgt lifu cdch nhift cua Viet Nam. Tgip chi khoa hgc va c6ng ngh§ nhi^t lanh 5/2009,
2. TrSn VSn Phii, V5 Thj Dieu (2001). Xdy dt/mg thiit bj xdc dinh hf so ddn nhift vd ddn nhift do ciia vgi 'if"- T9P chi khoa hgc va cong ngh? nhiet lanh 5/2001.
3. Nguyen Diic Lg\ (2010). Vgt lifu ky thugt nhiit Ignh. NXB B4ch khoa Ha Nfi nam 2010.
4. Songming Zhua, Michele Marcottea, Hosahalli Ramaswamyb, Yanwen Shaob, Alain Le-Bailc (2008).
Evaluation and comparison of thermal conductivity of food materials at high pressure. Food and Bioproducts Processing, Volume 86, Issue 3, September 2008, Pages 147-153.
5. Vanessa Jury, Jean-Yves Monteau, Jacques Comiti, Alain Le-Bail (2007). Determination and prediction of thermal conductivity of frozen part baked bread during thawing and baking. Food Research Intemational, Volume 40, Issue 7, August 2007, Pages 874-882,
TAP CHi KHOA HQC VA CONG NGHE LAM NGHIEP SO 4-2014
Cong nghiep rung
STUDY DETERMINING THERMAL PROPERTIES OF MAJOR APPLIANCES IN WOOD COMPOSITE MATERIALS NL03
Nguyen Thi Yen
SUMMARY
Coefficient of thermal conductivity is one of the physical quantities is difficult to determine the nature and specifically identifying influential necessary to research , design calculations and design process as well as construction products . The world has been a lot of research in order to build the database tables of experimental thermal conductivity , however, because of differences in natural conditions to the application of matenals often encountered Vietnam significant errors , not reliable enough for engineering calculations . Currently we have a number of thermal conductivity gauges however measured object is usually solid materials with high thermal conductivity , moisture and contains no denatured when the temperature changes . These devices do not meet the specific requirements of the thermal conductivity of materials having low thermal conductivity , the material containing high moisture content . In this study we rely on measuring principle to identify the source line thermal conductivity of cement board X = ( 0.203- 0.233 ) W/mK thermal conductivity and thermal conductivity husk board X. = ( 0.137 - 0 112 ) W/mK , the thermal conductivity of a cement board, a = (0.000108- 0.000126) m^ /s a = (0.000029 - 0.000042) mVs . With the experimental parameters can fully meet the insulation and NL03 machine used to determine the composite material has a low coefficient of thermal conductivity and moisture content
Keywords: Boards busk, coefficient of thermal conductivity, composite materials, cement boards, high thermal conductivity.
N g u o i phan bien Ngdy nhdn b a i N g d y nhSn phan bien N g a y quyet dinh dang
T S . Trinh Hien M a i 29/4/2014 03/7/2014 20/10/2014
TAP CHI KHOA HQC VA CONG NGH? LAM NGHI|P SO 4-2014 125