NGHIEN Cflu - TRAO DOI I NGHIEN CU'U THI/C NGHIEM ANN HU'dNG CUA TY LE NAP VA GOC NGHIENG DOI v6\ HOAT DONG CUA ONG NHIET TRONG TRU'O'NG CO CANH BEN NGOAI DE THU HOI NHIET THAI EXPERIMENTAL STUDY THE IMPACTS OF INCLINATION AND FILLING RATIO ON CIRCULAR-FINNED THERMOSYPHON HEAT PIPE USED FOR WASTE HEAT RECOVERY Nguyen Trung Kien, Le Chi Hiep Tn(6ng Dai hpc Bach Khoa TP Ho Chi Minh T6M TAT Ong nhiet Id mot thiet bi co khd ndng truyen nhiet rdt ldn nhd vdo qud trinh bien doi pha Trong bdi bdo ndy, mgt ong nhiet trgng trUdng co cdnh d ben ngodi ditng cho viec thu hoi nhiet, thdi dugc che tao de phuc vu cho viec nghien cilu dnh hudng ciia ty le nap vd gdc nghieng doi vdi hieu qud hoat dgng ciia ong nhiet Mdi chdt dUdc sddung dng nhiet Id nUdc nguyen chdt Di nghien cdu dnh hUdng cda ty le nap, dng nhiet dddc ddt thdng ddng vd ty le nap thay doi theo hon mite 10%, 20%, 30%, 40% De nghien cdu dnh hudng cua gdc nghieng, ong nhiet dUdc nap vdi tyle 30% vd gdc nghieng thay ddi theo ndm miic: Sif, 6CP, 70^, 80°, 90° Ket qud cho thdy, ty le nap toi Uu cda dng nhiet Id 30% dng nhiet ddt thdng ditng vd gdc nghieng tdi Uu Id 7QF vdi ty le nap 30% Tii Idioa: Ong nhiet; 6ng nhiet trgng trudng; Thu hdi nhiet thdi; Ty le nap; Gdc nghieng The heat pipe is a device of very high thermal conductance due to phase changes In this report, a circular-finned thermosyphon heat pipe (used for waste heat recovery) was constructed to study the impacts of filling ratio and inclination on the heat pipe's efficiency The working fluid was water To study the impacts offillingratio, the heat pipe was placed in an erect position with thefillingratio changing atfour levels: 10%, 20%, 30%, 40% To study the impacts of inclination, the filling ratio was 30%, and the inclination changed at levels: SCf, 50", 7(f, 80", Sif The results show that the optimum fillingratio was 30% when the heat pipe was place in an erect position; the optimum inclination was 70" with the filling ratio of 30% Keywords: Heat pipe; Thermosyphon; Waste heat recovery; Filling ratio; Inclination ISSN 0866 - 7056 TAP CHl CO KHi VIET NAM S6 11 nam 2014 www.cokhivietnam.vn NGHIEN Ctfu - TRAO D O I l.GICrt THIEU Ong nhiet la mot phan tii truyen nhiet kieu mdi co kha nang truyen nhiet di I6n hon nhieu lan so vdi cac phan tii truyen nhiet thong thddng Nguyen tac lam viec cua dng nhiet la sti ket hop giQa qua trinh dan nhiet cua kim loai va qua trinh trao doi nhiet ddi lUu bay bcfi va ngiing tu cua mdi chat Hinh trinh bay so nguyen ly cua ong nhiet Ong nhiet gdm mdt dng kin bang kim loai mat cd mot ldp vat lieu mao dan va mot it lUu chat lam viec ben d ap suat bao hoa Khi gia nhiet cho phan sdi ciia ong, mdi chat se nhan nhiet, sdi va hda hoi Hdi d dp suiit cao se di chuy& dng tdi viing cd nhiet thap hcfn de ngUng tu Mdi chat ngiing tu se chay dpc theo ldp mao d i n va quay trd lai Qua trinh nhii vay tiep tuc lap lai Do b^n la mdi tnidng chan khdng va mdi chat cung da d trang thai bao hda nen nhan diicfc nhiet IiiOng, du la rat nhd, liiu chat ciing cd the hda hoi Qua trinh ngiing tu se tda mdt nhiet liiong ngoai diidi dang nhiet an Nhii vay, dng nhiet da chuyen nhiet nhan dxiac til vi tri tdi vi tri khac dpc tren dng Wick Wipour Cavity _^® Envifonmenl Tempefature Hinh 1: Sd nguyen ly cua dng nhiet Trong nguyen ly dng nhiet md ta tren day, liiu chat ngiing tu diioc di£a quay trd lai phan sdi nhd vao liic mao dan Ngoai thiet ke nay, ngiidi ta cdn cd nhieu each thiic khac de dUa chat tu quay trd lai phan sdi Ddi vdi dng nhiet trpng trudng, chat Idng ngUng dUpc diia ve phan soi nhd liic trifdng Vi ly dd, loai dng nhiet boat dpng can thiet phan sdi phai dat thap hon phan ngUng Ong nhiet can phai diipc nap moi chSt vao ben dng NgUdi ta can phai chii y den sii hda hpp gii2a tinh chat ciia mdi chat nap va v | t lieu lam ong Co the tham khao each mdt sd tieu chuan liia chpn mdi chat va vat lieu lam ong tai lieu [Ij Trong khoang nhiet dp Iam viec thdng thiidng, ngildi ta thiidng chpn mdi chat nap la niidc tinh khiet va vat lieu Iam ong la dong Khi nghien cilu ve dng nhiet, cac tac gia thudng tap trung vao cac van de sau: - Tinh chat cua mdi chat nap va vat lieu lam ong nhiet - Cac thdng so kich thUdc cua ong nhiet nhU: Chieu dai dng nhiet, dUdng kinh dng, ty Ie gifla chieu dai phan sdi va phan ngUng cua dng nhiet - Goc nghieng cua dng nhiet (gdc giiia true dng nhiet va phUdng nam ngang) - Lupng mdi chat nap vao ben dng nhiet (ty le the tich mdi chat nap va the tich phan soi cila dng) - Cac gidi ban Iam viec cUa ong nhi$t Nhieu nghien cflu da nhan manh d^n anh hfldng cua gdc nghieng va Ifldng nap ong nhiet den hieu qua boat ddng cua dng Cac tac gia cho rang ddi vdi mdi dng nhiet va moi mdi chat nap Iudn tdn tai mpi lUpng nap tdi flu va gdc nghieng tdi flu de ong nhiet cd the boat ddng hieu qua nhat Tuy nhien, gia tri toi Uu v i n chfla dUpc thdng nhat cac nha khoa hpc Bui Hai, Tran Van Vang [2] cho rang^ ISSN 0866 - 7056 TAP CHi CO KHf VIET NAM, Sd 11 nam 2014 www.cokhivietnam.vn NGHIEN cufu-TRAO D O I ty le nap dng nhiet ddi vdi nUdc tinh khiet la khoang 30 - 50% va gdc nghieng cua dng nhiet trpng trfldng nen ldn bdn 6" de dng nhiet hogit dpng binh thudng Hoang An Qudc, Le Chi Hiep, Hoang DUdng Hiing [4] nghien cflu ve dng nhiet mat trdi da dUa ty Ie nap toi Uu la 30% Yong Joo Park, Hwan Kook Kang, Chul ]u Kim [4] da cimg cd gia thiet cua nhieu nha nghien cflu trfldc ve gidi han dry-out (khi ty le ngip qua be) va gidi han flooding (khi ty Ie n^ip qud Idn) cua dng nhiet David Reay va Peter Kew [11 cho rang gdc nghieng tfl 60°-80° thi cdng suat dng nhiet dat gia tri cUc dai D6 xdc dinh dflpc cac phan nhi^t trd nay, ta can phai biet he sd tda nhiet doi luu gifla mdi chat ndng va be mat ngoai 6ng phan sdi a , he sd tda nhiet gifla mdi chat Ianh va be mat ngoai dng phan ngflng a^ h^ sd tda nhiet doi sdi a^ va he so tda nhiet ngflng a cua chat mdi chat nap ong nhiet Day la van de da dflpc trinh bay hau het cdc giao trinh ve truyin nhiet Phfldng trinh (1) cho thay, ve mat ly thuyet ta cd the dat dfldc cdng suat nhiet rSt ldn Tuy nhien, thilc ti, cdng suat nhiet qua Idn cd the xay mpt so hien tfldng Iam han che, ngan chan ddng ldng trd ve phan Trong bai bao nay, tac gia da che tao sdi cua dng nhiet Theo cac nha nghien cflu [1], mdt dng nhiet trUdng cd canh d ben [2], cac gidi ban cd the xuat hien trfldng hdp dng nhiet trpng trfldng nhU: Gidi han Ioi ngoai va thi nghiem anh hfldng cua ty Ie nap cudn, gidi han sdi va gidi ban am lan Ifldt va goc nghieng ddi vdi hi^u qua boat dpng cua dflpc xdc dinh theo cdc cdng thfle sau: dng nhiet nham tim ty le nap tdi flu va gdc nghieng tdi flu ddi vdi dng nhiet da dflpc ch^ r.[ai.s.p5(Pi-Pv)]°-^M2) tao •1:1 (3) CO SCi L^ THUYET VE ONG N H I £ T TRONG TRU'ONG ^ Cdng suat nhiet cua dng nhiet trpng trUdng dUdc tinh theo cdng thfle: , \k.R.T„ f (4) THIET KE VA CHE TAO ONG N H I £ T TRONG TRircJNG ^-^^ (1) fli + fi +fl,+fi^+flj+flg+ flj Cdc nhiet trd R,, R^, R^, R^, R^, R^, R^ la 3.1 Cac thong s6 ong nliiet tnidng nhiet trd phan dflpc trinh bay tren hinh Ong nhiet daoc che tao la ong nhiet 2: tnl6ng loai co canh v6i cac thong so nhii sau: Q= + Thong so ong nhiet: - Chieu dai ong nhiet: 1000 mm, do: PhSn soi: 400 mm; o Phan ngiing: 400 mm; o Phan doan nhiet: 200 mm; Hinh 2: Cdc thdnh phdn nhiet trd cua ong nhiet trgng trUdng - Diidng kinh ngoai cua 6ng:'?22,22 - Do day vach ong: 0,7 m; - Vat lieu lam ong: Dong ISSN 0866 - 7056 TAP CHf CO KHi VIET NAM, S6 11 nam 2014 www.cokhivietnam.vn NGHIEN cufu-TRAO DOI Oiii'i eOOnn —400fln 1 ill |l{|||||||||'1{|i|||||'J11|;|1||1||||1 lllllillll II1 ill llllllllllllllllllllllilllllllllllllllll Pill li li 11 ll il 1II j ll 11 i^^H^ Hinh Stf ong nhiet h Thdng sd cdnh: - Kich thfldc cdnh: 50 x 50 mm^ - Khoang each gifla hai cdnh; t = mm - Chi^u day cdnh: A^ = 1mm - Vat lieu lam cdnh: nhdm ngflng xuat hien dng nhiet se lam giam dang ke hieu suat ciia dng Ngoai ra, neu canh nhdm va dng ddng khdng tiep xue tdt, kha nang trao doi nhiet gifla ben ngoai va ben dng nhiet cung khdng dfldc dam bao + Mdi chat nap: nUdc nguyen chat 3.2.Ch^tao ong nhiet - Cat canh nhdm hinh vudng canh 50 mm va dng ddng^^2,_2 - Due mdt 16^22 chinh gifla cdnh nhdm hinh vudng da dupc cat san - Quet ben ngoai dng nhiet mdt ldp sdn nhu pha bdt nhdm rdi ddng tiing cdnh nhdm vao dng nhiet theo phUPng phap ddng chat Sau mpt thdi gian, cdnh nhdm se dinh chat vao ong ddng va cdc khe hd neu cd gifla canh nhom va dng ddng se dupc lap day bang hot nhdm - Ve sinh phia ben dng va ban kin phan ngflng va phdn bay hdi l^i - De thfl kin ong nhiet, ta ket noi dng nhiet va bd nap mdi ch& de nen vao dng nhiet den dp suat dU khoang 360mmHg Thdi gian thfl kin keo dai 12 gid - Sau dd hut chan khdng va nap mdi chat vao dng nhi^t Hai diem quan trpng nhat qud trinh gia cdng dng nhiet la viec gan cdnh vao dng nhiet va hflt chan khdng Neu viec hut chan khdng khdng dupc thfle hien tdt, khdng Hinh 4: Cac thong sd cdnh ISSN 0866 - 7056 TAP CHf CO KHI VIET NAM, Sd 11 nam 2014 www.cokhivietnam.vn NGHIEN cufu-TRAO DOI X A Y D U N G M O HiNH THi NGHIEM Trong sd nay, dng nhiet dflpc nap 4.1 Ihi nghiem anh hfldng cua ty 1^ nap den san vdi ty Ie nap 30%, ddng khdng ddi lflu cUdng bflc vdi tdc dp m/s vd gdc nghiSng hieu qua hoat dong cua ong nhiet dUdc thay doi theo mflc: 50", 60", 70", 80" 90" Ty Ie nap dng nhiet dfldc dinh nghia la ty sd gifla the tich Ifldng mdi chat nap vao 4.3 Gan sensor nhift dd dng nhiet va the tich phan sdi cua dng Theo nhieu tdc gia, ty sd cd anh hfldng khd ldn Sensor nhiet dp dflpc gan d phan soi den hieu qua boat dpng cua dng va vdi moi mdi dng nhiet each nap phan sdi 30 mm va d phan chat luon ton tai mdt ty sd nap tdi flu ma d ngflng dng nhiet each vdch phan ngflng 30 mm cdng sudt nhiet ben cua dng se dat gid tri de nhiet dp phan sdi va phan ngflng cua dng ldn nhat Sd thi nghiem dflpc trinh bay tren hinh Hinh 6: Sd thi nghiem gde nghiing ong nhiet Hmh 5: Sd thi nghiem vi ty le nap ong nhiet KET QUA THI NGHIEM Trong so dd nay, dng nhiet se dUdc dat thing dilng, dong khong duoc thoi doi liiu cuang bile vdi toe m/s va tyle nap vao ong diioc thay doi theo miic: 10%, 20%, 30%, 40% 4.2 Thi nghiem anh hiidng cua goc nghieng den hieu qua hoat dong cua ong nhiet Goc nghieng ong nhiet duqc dinh nghia la goc hop bdi true ong nhiet va phiiong nam ngang Theo nhieu tac gia, ty so ciing co anh hudng den hieu qua hoat dpng ciia ong nhiet va vol moi moi chat deu ton tai mot goc nghieng toi Uu ma d cong suat nhiet ben ctia ong se dat gia tri ldn nhat So thi nghiem diioc trinh bay tren hinh 5.1 Anh hiiong cua ty le nap den hieu quS hoat dong cua fing nhiet ' ' i-T^IenaplO%: Hinh 7: Ihi nghiem ty le nap I ISSN 0866 - 7056 TAP CHi CO KHi VIET NAM, S5 11 nam 2014 www.cokhivietnam.vn NGHIEN cufu - TRAO DOI + Ty le nap 20%: + Chenh lech nhiet trung binh giiia phan soi va phan ngiing ong nhiet cac tnidng hop duoc trinh bay tren bang 1: Hinh 8: Thi nghiem ty U nap + TylSnap30%: Tyle nap (%) Chenh lech nhi^t dd trung binh (°C) 10 25,93 20 10,83 30 9,28 40 11,94 5.2 Anh hiidng cua goc nghieng den hieu qua boat ddng cua dng nhiet + Gdc nghieng 50" Hinh 9: Thinghiem ty le nap 30% + Tyle nap 40%: Hinh 11: Thinghiemgoc nghiingSCP + Gdc nghieng 60" t Hinh 10: Thi nghiim ty li nap Hinh 12: Thi nghiem goc nghieng 60° ISSN 0866 - 7056 TAP CHI CO KHI VIET NAM, Sd 11 nam 2014 www.cokhivietnam.vn NGHIEN cufu -TRAOOOl BAN LUAN KET QUA f Gdc nghieng 70° 6.1 Nh4n xet chung Cac thi nghiem trinh bay nhiet phan sdi va phan ngUng khoang phiit Ta cd the thay ban dau nhiet phan sdi v i phfa ngiing d^u tang nhanh sau dd tiiong ddi on dinh d mdc nhiet dp trSn 80°C Hmh 13: Thi nghiem gdc nghiing 70° + Thi nghiem gdc nghieng 80" Hinh 14: Thi nghiem gdc nghiing SCfi + Thi nghiem vdi gdc nghieng 90" da dflpc trinh bay tren hinh + Chenh lech nhiet dp trung binh gifla phan sdi va phan ngflng dng nhiet cdc trfldng hpp dflpc trinh bay tren bang 2: Goc nghieng (") Chenh lech nhiet trung binh (»C) 50 10,63 60 10,205 70 9,105 80 9,125 90 9,28 Chenh lech nhiet dp gifla phan sdi va phan ngiing khoang ti! + S'C dng nhiet da hoat dpng on dinh Chenh lech nhiet dp cd diioc la nhiet trd vach dng phan sdi, nhiet trd vach ong phan ngUng va chenh lech nhiet dp that sU giiia phan sdi va phfa ngiing Vl the, chenh lech nhiet dp gifla phfa sdi va phan ngflng ben dng se nhd hon gia tri •>• 8°C Day la gia tri hoan toan cd the chap nhan dfloc 6.2 Anh hudng ciia ty le nap den hieu qua hoat ddng cua ong nhi^t Trong cac thi nghidm vdi ty le nap 20%, 30%, 40%, dng nhiet hoat ddng hieu qua gfa nhfl da on dinh Sfl khac dflpc the hien giai doan khdi dong ciia dng nhiet Trong giai doan khdi dpng, nhiet dp vach ngoai phan sdi T tang nhanh hdn so vdi nhiet dp vach ngoai phan ngflng T Sd di cd dieu la nhiet dp vach ngoai phan sdi phai tang den mot gia tri nhat dinh thi ben dng nhiet mdi xay qua trinh bay hoi va ngflng tu Vl the, ban dau nhiet trd dng nhiet cdn rat ldn, chSnh lech nhiet dp gifla phan sdi va phfa ngflng cua dng nhiet 15 + 20°C va chenh lech se giam dan xudng cdn khoang + 8°C va tri on dinh d mflc ISSN 0866-7056 TAP CHi CO KHi VIET NAM, Sd II nam 2014 www.cokhivietnam.vn NGHIEN cufu-TRAOD6I Cac dng nhiet hau nhfl deu trai qua giai doan khdi dpng va dn dinh tfldng ddi gidng nhu da trinh bay d tren Van de can phai so sdnh d day la thdi gian khdi ddng cua dng nhiet va chenh lech nhiet dp gifla phan sdi va phan ngflng cdc trfldng hdp thi nghiem tren Ket qua thi nghiem cho thay, ddi vdi dng nhiet cd ty le nap ldn (40%) thdi gian khdi ddng lau hdn cdc dng nhiet cd ty le nap nhd (20%, 30%) va chenh lech nhi^t dp gifla phan sdi va phan ngflng Idn, cd the len den 20"C Ta nhdn thay dng nhiet dflpc nap vdi ty le 30% la tdi Uu nhat: Thdi gian khdi ddng nhanh, chenh lech nhiet dp nhd hdn so vdi cdc trfldng hpp cdn l^i Neu imdi chdt nap vdo dng nhiet qud it, b^n ong nhiet xay hien tfldng dry-out, hieu qua lam vi6c cua dng nhi^t trd n&n cUc ky kem (hinh 7) Dieu la Ifldng nap qua it, long chi bay hdi tai phdn dng gan vdi phan ngflng, phan dng xa phan ngflng khdng dfldc cap Idng nen nhiet dp tang nhanh Du trfldng hpp nhiet dp ngUng tu van tang nhflng mflc dp tang hau nhfl khdng ddng ke so vdi nhiet dp phan sdi nen chenh lech nhiet dp ldn Tfl nhflng ket Iuan tren, cd the thay ring, ddi vdi dng nhiet da dflpc che tao, ty^ le nap 30% la ty le nap tdi Uu Ket luan tUPng ddi phil hpp vdi cdc ket luan cua nhieu tdc gia nghien cflu ve dng nhiet trpng trUdng cd be mat nhan ben da dflpc cdng bd [1], [2] 6.3 Anh hi/dng cua goc nghieng d^n hieu qua hoat ddng cua ong nhiet Khi thay doi gdc nghieng cua dng nhiet, cdng suat nhiet cua dng nhiet ciing hi thay doi •vi cac ly sau: Cdng suat nhiet ben ngoai thay ddi sii tiep XUC gifla dng nhiet va ddng khdng cat ngang qua Theo ly thuyet, neu dng nhiet dat thang dflng thi cdng suat nhiet ben ngoai cua dng nhiet la ldn nhat Cdng suat nhiet ben bi thay ddi sU thay ddi cua lflc trgng trfldng va chieu day mang nUdc ngflng tren be mat dng phan ngflng Khi gdc nghieng tang, lUc trpng trfldng tdc dung len ddng chat long ngflng tang nhien cfldng dp tda nhiet giam chieu day mang nfldc ngflng tren b^ mat dng phan ngflng tang Quan sat ve chieu day mang nfldc ngflng tang Ien gdc nghieng dng nhiet tang da dfldc trinh bay [1] Trong cac thi nghiem tren, cd the thay rang hieu qua Iam viec cua dng nhiet khdng thay doi rd ret ddi vdi trfldng hdp gdc nghieng dng nhiet la 70", 80", 90" Ong nhiet dat nghieng 50", 60" cd thdi gian khdi dpng Iau hdn va chenh lech nhiet dp cao hdn so vdi cdc trfldng hdp cdn lai Dieu cd the la gdc nghieng cua dng nhiet so vdi phfldng thang dflng du ldn, anh hudng cua gdc anh hUdng cua gdc nghieng ddi vdi cdng suat nhiet ben ngoai trd nen rd ret hdn va tfl day cung cd the thay rang, cdng suat nhiet ben ngoai cd tdc ddng ldn hdn va rd net hdn den cdng suat nhiet toan bd so vdi cdng suat nhiet ben Tfl ket luan tren day, cd the dfl doan rang, neu gdc nghieng dng nhiet cang nhd thi hieu qua dng nhiet cang kem Vi the, tfl cdc ket qua thi nghiem tren day, cd the thay gdc nghieng tdi Uu la 70" Gdc nghieng tdi Uu tfldng ddi ldn hdn so vdi ket qua cua mpt sd tac gia khac [2], [4] Tuy nhien, cung cd the thay rang, anh hfldng cua gdc nghieng ddi vdi hieu qua hoat dpng cua dng nhiet khdng nhieu va khdng rd net nhfl anh hfldng cua ty le nap den hieu qua boat ddng cua dng nhiet ISSN 0866 - 7056 TAP CHI C O KHI VIET NAM, Sd 11 nam 2014 www.cokhivietnam.vn NGHIEN cufu-TRAOD6I R^: Nhiet trd vdch dng phan sdi, K/W; R^: Nhiet trd vdch dng phan ngflng, K/W; Tfl nhflng ket qua da nghien cflu, cd the R^: Nhiet trd phan sdi ong nhiet, K/W; thay rang, ty Ie nap va gdc nghieng dng nhiet R^: Nhiet trd phan ngflng dng nhiet, K/W; CO anh hfldng nhat dinh den hieu qua lam viec R_,: Nhiet trd phan doan nhiet cua dng nhi^t, cua dng nhiet Ddi vdi dng nhiet trpng trfldng K/W; CO canh da dfldc che tao, ty Ie nap tdi flu la 30% Q^: Gidi ban Idi cudn cua dng nhiet, W; mdi chat nap la nfldc va dng nhiet dat thang Q^: Gidi han sdi cua dng nhiet, W; dflng Gdc nghieng dng nhiet cung cd anh Q^: Gidi ban am tbanh cua dng nhiet, W; hudng den hieu qua boat ddng cua dng nhi^t A^: Tiet di^n cua hdi dng, m^; nhflng khdng rd rang nhfl anh hfldng cua ty A^: Tiet dien mat dng phan sdi, m^; Ie nap Gia tri gdc nghieng tdi flu trfldng p^: Khdi lupng rieng cua chat long ngUng, kg/ hop la 70" m^; p^: Khdi Ifldng rieng cua hdi, kg/m^; Mot sd k^ hi^u bai: a^: Sflc cang b^ mat cua mdi chat nap, N/ra; g: Gia tdc trpng trfldng, m/s^ t^: Nhiet dp ben ngoai ong phan sdi, "C; r: Nhiet an hda hdi cua mdi chat nap, J/kg; t^; Nhiet dp ben ngoai dng phan ngflng, "C; k: sd mfl doan nhiet cua hdi; K^: Nhiet trd ben ngoai dng phan sdi, K/W; R: Hang sd chdt cua hdi, J/kgK; R,: Nhiet trd ben ngoai dng phan ngflng, K/W; T^: Nhiet dp tuyet doi ciia hdi, K.*J* KET LUAN Ngay nhan bai: 01/10/2014 Ngay phan bien: 08/11/2014 Tai lieu tham khao: [I] D.A Reay P.A Kew Heat pipes, Pergamon Press Oxford (2006) [2] Bui Hai Tran Van Vang, 6ng nhiet vd dng dung ciia o'ng nhiit, NXB Bach Khoa, Ha Ndi (2008) [31 Hoang An Qu6c, Le Chi Hiep, Hoang DUdng Hung Nghien cdu thd nghiem dng nhiit mdt trdi loai chan khong dliu kien Viet Nam,Ta.p chi Khoa hpc va Cong nghe Nhilt vol 74 pp 8-11 2007 [4] Yong Joo Park, Hwan Kook Kang, Chul Ju Kim Heat transfer characteristics of a two-phase closed thermosyphon to the fill charge ratio International Journal of Heat and Mass Transfer, vol 45 pp 4655 4661,2002 ^*^ [5] Ming Zhang Zhongliang Liu Gucyuan Ma, Shuiyuan Cheng, Numerical simulation and experunental IlOO 2009" ' " ° " ' ' ' ' ' ' ' * ' ^ " " ^ ' ' ^ ^ ° " ^ ' Energy Conversion and Management, vol 50 pp 1095 - [61 Mostafa A^ Abd ELBaky, Mcusa M Mohamed, Heat pipe heat exchanger for heat recovery in air conditioning Applied Thermal Engineering, vol 27, pp 795 - 801 2007 [7] S H Noie Heat transfer characteristics of a two-phase closed thermosyphon Applied Thermal Engineering, vol 25 pp 495 - 506.2005 Fl- = " " " ' " • " ISSN 0866 - 7056 TAP CHi CO KHi VIET NAM, Sd 11 nam 2014 www.cokhivietnam.vn ... Khi nghien cilu ve dng nhiet, cac tac gia thudng tap trung vao cac van de sau: - Tinh chat cua mdi chat nap va vat lieu lam ong nhiet - Cac thdng so kich thUdc cua ong nhiet nhU: Chieu dai dng nhiet,... 30 - 50% va gdc nghieng cua dng nhiet trpng trfldng nen ldn bdn 6" de dng nhiet hogit dpng binh thudng Hoang An Qudc, Le Chi Hiep, Hoang DUdng Hiing [4] nghien cflu ve dng nhiet mat trdi da dUa... da dflpc trinh bay hau het cdc giao trinh ve truyin nhiet Phfldng trinh (1) cho thay, ve mat ly thuyet ta cd the dat dfldc cdng suat nhiet rSt ldn Tuy nhien, thilc ti, cdng suat nhiet qua Idn