Nghiên cứu thực nghiệm các yếu tố ảnh hưởng chế độ làm việc của thiết bị làm mát bay hơi

NGHIEN CU'U-TRAO D | NGHIEN CO'U THLTC NGHIEM CAC Y^U T ANH HU'dNG CHE DO LAM VlEC C O A THltT Bj LAM MAT BAY HQI EXPERIMENTAL STUDY FACTORS AFFECTING THE PERFORMANCE OF EVAPORATIVE COOLING SYSTEMS Nguyln Thfi Bao', Nguyen Bao Toan^ L6c Chac Hoang^ 'Vifin Phat trifin Nang lugng Ben viing ISED ^Trudng Dai hgc Su pham Ky thuat TP Hd Chi Minh TOM TAT Nhdm gidm phu thugc vdo mdy lgnh vd diiu hoa khong truyen thong dang sii: dung mdy nen vd tdc nhdn lgnh CFC hay HCFC, thi viec nghiin ciru vd trng dung thiet bi ldm mdt bay hai thdn thien vdi moi trudng vd tiit kiim ndng lugng Id cdn thiit Bdi bdo trinh bdy nghien cuu thycc nghiem moi quan hi giira lieu lugmg khong Q^ luu luang nuac Q^ hiiu sudt tgo dm rj, ti so luu lugmg nuac vd khong E den hiiu sudt ldm viec cda thiit bi ldm mdt bay hai Bdi bdo cUng nghien cuu dnh huang cua cdc thong so noi tren den hogt dgng cua thiit bi ldm lgnh bay hai a cdc nhi^t nuac vdo khdc nhau, cdc vdn de ndy chua dug'c de cap a cdc nghien cuu tren the gi&i Tir bdi bdo de xudt cdc thong so phit hcrp cho thiet bj ldm mdt bay hai img vol dieu kien hgu dm Vtet Nam Tir khoa: Ldm mdt bay hai; Bay hai true tiip; Bay hai gidn tiep; Dieu hoa khong ABSTRACT In order to reduce the dependence on traditional refrigeration and air conditioning systems using CFC and HCFC refrigerants, the research and development of environmental friendly and energy saving evaporative cooling systems are necessary This article presents the experimental study in the effects ofairfiow rates Q^ water flow rates Q^ humidlfication factor rj, the ratio of entering water and airflows E on the performance of evaporative coolers Thepaperalso investigates the effects ofthe above mentioned parameters on the effectiveness of evaporative cooling systems at different water temperatures that has not been reported before Then suitable parameters of evaporative cooling systems in humid climates like Vietnam are suggested Keyword: Evaporative cooling Direct evaporative cooling Indirect evaporative cooling, Air conditioning ISSN 0866 - 7056 TAP CHf CO KHf VIET NAM, Sd nam 2017 NGHIEN CLTU - TRAO D6\ TONG QUAN VE LAM MAT BAY HOI Nu'dc Theo cac thdng kfi, cdng suat dien tifiu hao cho he thdng difiu hda cac cdng trinh nhu: Cao 6c van phdng, khach san chiem tir 45-55% tdng lugng difin tifiu thu [1] Mac du hifin cd rat nhieu he thdng difiu hda khdng dugc cai tifin nham tifit kiem nang lugng nhu hfi thdng difiu hda tnmg tam cd luu lugng nudc, luu lugng gid thay ddi theo phu tai, Trfin CO sd hifiu chinh nang suat lanh sat vdi phu tai thuc te, nhifin cac he thdng deu sir dung nang lugng dien Cac he thdng dieu hda ndi trfin dfiu phai lam lanh ca nhiet hifin lln nhifit an, ma lugng nhiet an thudng chiem tir 20%-60% tdng tai nhiet ciia he thdng Thuc tfi, tdng nang suat lanh loai cdng trinh van phdng, nha hang, sieu thi, difiu kifin thdi tiet bfin ngoai nhau, bao gdm loai: Loai chu ddng va thu dgng He thdng lam mat bay hoi trgc tifip loai chu dgng it tdn kem nang lugng, tifit kiem len dfin 90%, hieu qua ban udt cd thfi d^t dugc 70% -80% [4], tromg dd thi he thdng lam mat bay hoi true tiep loai thu dgng cd thfi lam giam nhifit khdng khoang 9''C [5] Bagia dofn mODSClhi lEODEGli? Ili6ngUiac Hinh 1: Phdn logi cdc hi thong ldm mdt bay hai Cd rat nhifiu nghien ciiu trfin the gidi ve ly thuyfit va thuc nghifim cdng nghe lam mat bay hoi cho dieu hda khdng [2] Theo Duan va cgng su [3], nfiu he sd lam lanh COP ciia cac he thfing dieu hda khdng su dung may nen tii dfin va may lanh hap thu tii 0,6 dfin 1,2 thi COP ciia he thdng lam lanh bay hoi la tu 15 den 20 Lam mat bay hoi cd the dugc chia lam loai chinh: (i) Lam mat bay hoi true tifip (DEC: Direct Evaporative Cooling); (ii) Lam mat bay hoi gian tiep (IEC: Indirect Evaporative Cooling) va (iii) lam mat bay hoi kfit hgp (Combined DEC/IEC) Hinh 1, chi su phSn loai cac hfi thdng lam mat bay hoi dang dugc nghifin ciiu va img dung hien tren the gidi He thdng lam mat bay hoi gian tifip nhifit bau udt cd thfi lam giam nhifit khdng xuong thap, nhung khdng thfi thap hon nhiet bau udt ciia khdng vao He thdng bao gdm loai IEC dang tam, IEC dang hinh dng va IEC dang ong nhifit Lam mat bay hoi true tiep (DEC) la loai lam mat lau ddi va don gian nh4t, dd, khdng ngoai trdi dugc tiep xiic true tifip vdi nudc Ky thuat da dugc sit dung hang ngan nam trudc vdi nhieu hinh dang khac He thdng lam mat bay hoi gian tifip difim suong cd the lam giam nhifit khdng khdi thifit bi xudng thap hon nhifit ban udt va tiem can nhifit difim suong cua khdng vao thifit bi '^ He thdng lam mat bay hoi gian tiep (IEC) cd thfi lam giam nhiet khdng ma van giir nguyen am Dd la mdt im difim so vdi he thdng lam mat bay hoi true tiep He thdng cung dugc chia lam loai: He thdng lam mat bay hoi gian tifip nhifit bau udt va he thdng lam mat bay hoi gian tifip diem suong [3] ISSN 0866 - 7056 TAP CHf CO KHf VIET NAM, Sd nam 2017 NGHIEN C L T U - T R A O D O I He thdng lam lanh bay hoi ket hgp (Combined DEC/IEC) cd am thap hon, hieu suat cao hon va am dugc kifim soat hon so vdi ca hai he thdng kieu true tiep va gian tifip, nhifin he thdng c§n chi phi ban dau cao va he thdng phiic tap He thdng phd bifin d cac d£Lng hai giai doan, ba giai doan va nhifiu giai doan, cu thfi bao gdm: Lam lanh bay hoi kfit hgp hai giai doan bao gdm thifit bi lam lanh bay hoi gian tifip (giai doan 1), theo sau lam thifit bi lam lanh bay hoi true tiep (giai doan 2) Loai hifiu qua dat dugc khoang 90-120%, nhung miic tifiu thu nudc tang 55% [6] Liim lanh bay hoi ket hgp ba giai doan la loai hai giai doan ket hgp vdi giai doan tach am bang chat hiit am, cd thfi tifit kifim nang lugng 54% -82% so vdi cac he thdng lam lanh Sli dung may nen truyen thdng [7] Lam lanh bay hoi kfit hgp nhieu giai doan la mgt he thdng lam lanh bay hoi hai giai doan kfit hgp vdi cac chu ky lam lanh khac, vdi miic tifit kifim nang lugng tit 75-79% cao hon so vdi he thdng lam lanh sit dung may nen truyen thdng [8] Mehere va cac cdng su [9] da phan tich va tdi uu hda qua trinh truyen nhifit va truyfin chat he thdng lam lanh bay hoi true tifip Phan tich da chi rang, luu lugng khdng va sd t3m cooling pad la hai yfiu td anh hudng chinh dfin hifiu suat lam mat cua mgt he thdng lam mat bay hoi true tifip Vdi sd lugng tam cooling pad tdi uu, nhiet khdng dau dat dugc 25,5°C, am tuong ddi dat 75% va hifiu suat dat dugc 82,6% vdi difiu kien mdi trudng xung quanh 35''C Tdc Iudng khdng tdi uu la 0.0135 kg/s Tuy nhifin, anh hudng cua hai thdng sd quan trgng la nhiet va luu lugng nudc vao he thdng lam mat khdng dugc dfi cap nghien ciiu O Viet Nam hifin nay, cd kha it cdng trinh nghien ciiu ve cdng nghfi lam mdt bay hoi, mac du cdng nghfi da dugc iing dung kha phd bifin mgt sd nganh cdng nghifip va dan dung, ciing nhu cac thifit bi gia dung [10, 11] Bai bao dugc tac gia vifit nham gop phan vao viec nghifin ciiu cac yfiu td anh hudng den qua trinh lam lanh bay hoi true tifip de dfi cac che lam vific hgp ly cua thifit bi lam mat bay hoi dieu kien hau Viet Nam M H I N H THf NGHIEM 2.1 Thiet bi thi nghiem Tdng quat md hinh dugc lap dat tai Trudng Dai hgc Su pham Ky thuat TP.Hd Chi Minh [12] dimg dfi dac thuc nghiem dugc cho Hinh Md hinh la kieu lam mat bay hoi true tifip dugc thifit kfi bao gom mgt so bd phan: Quat hiit, bom nudc, bifin tan diing difiu chinh tdc qugt va bom, thiing chua nudc, tam trao ddi nhifit cooling pad Thfing sd kich thudc cac thifit bi gdm: Bom, cdng suat 400W, sir dung difin pha 220V; Quat, cong suat 400W, cung su dung difin pha 220V, toe quay 1425v/ph; TSm trao ddi nhifit coolmg pad: Cao 80cm, dai 62cm va rdng 15,6cm; Thiing chiia nudc tuan hoan vdi thfi tich chiia 150 lit; Bifin tSn hifiu DELTA VFD-L cdng suat HP, loai pha dugc sii dung de thay ddi lim lugng cua bom va quat Hinh 2: Sa nguyen ly cua hi thong ihi nghiim ldm lgnh bay hai nuac: 1) Vi tri nhiet dp vd dg dm khong ddu ra; 2) Vi tri nhiel dp vd dg dm khong dau vdo; 3) Vi tri nhiel cua mrdc ISSN 0866 - 7056 TAP CHf CO KHf VIET NAM, Sd nam 2017 www.cokhivietnam.vn NGHIEN CLTU - TRAO OCl Nhifit va am cua khdng vao va khdi thiet bi dugc xac dinh bang dung cu cd thdng sd Bang dudi day: J-1 Thong so thiet bi do: STT Ten thiet bi Apech TH-05/ Jumbo Digit Dai lioat dSng Indoor: 0-50»C Outdoor:-50"-70»C Dpim: 15 + 95% Difiu kifin mdi trudng qua trinh dat thuc nghifim: Nhifit tnmg binh: t = 30°C; Do am tmng binh: cp ^ 75 % Luu lugng nudc va luu lugng khdng dugc thay doi bang bien tan dfi difiu khifin tSn sd ciia ddng co bom va quat Da cay dugc sir dgng dfi lam lanh nudc va nhiet nudc thimg chiia dugc difiu chinh dfin nhiet yeu cau ciia thi nghifim bang each difiu chinh lugng nudc va lugng da thimg Nhiing thi nghifim chu yeu da dugc thuc hien tren mo binh nham xac dinh cac ndi dung Do cliinti xac Nhiet do: ± 1°C Dp im: ± 5% va chat giiia nudc va khdng khi, thudc vao nhifit Clia nudc so vdi nhifit ciia khdng Trfin thuc tfi, qua trinh A-1 vaA-2 khdng cd y nghTa he thdng lam mat (hic nhifit khdng tang lfin hay khdng ddi sau tham gia qua trinh) Vi vay, thi nghiem dugc thuc hien vdi trudng hgp cdn lai, bao gdm: (i) Nhiet nudc t^ nam giiia nhifit nhiet kfi khd tjj^ va nhiet nhifit kfi udt twb cua khdng khi; (ii) Nhifit nudc bang nhifit bau udt t = t^j^; (iii) Nhiet nudc nam giira nhifit bau udt va nhifit difim suong t^ "^ t^ *^ t^^; (iv) nhifit nudc bang nhiet diem suong t^ ^ tj va (v) Nhiet nudc thap hon nhifit difim suong t^ < t^ Kfit qua cua thi nghiem dugc cho Bang - Xac dinh anh hudng cua nhifit nudc dfin hieu qua lam vific cua he thdng lam mat bay hoi nudc - Xac dinh anh hudng cua luu lugng nudc dfin hifiu qua lam viec ciia he thdng - Xac dinh anh hudng cua luu lugng khdng dfin hifiu qua lim viec cua he thdng Ket qua ciia cac thi nghifim dugc trinh bay ben dudi Hinh Trgng thdi thay doi ciia qud trinh truyin nhiet vd chdt giira nuac vd khong 2.2 Anh huong cua nhiet (to nirofc den hieu qua Um vific cua he thdng Nhu bieu dien trfin Hmh 3, cd trudng hgp cd thfi xay qua trinh truyfin nhifit ISSN 0866 - 7056 TAP CHf CO KHf VIET NAM, Sd nam 2017 NGHIEN CLfU-TRAO DOI Bdng Ket qud thi nghi&m vai nhiet donwac khdc nhau: STT Thi nghi&m V, U, i ii lii iv twb t^, nfin tri lugng nudc lam mat nhd di vao thifit bi dfi tang hifiu qua lam mat Khi nhiet nudc lam mat nhd hon hay bang nhifit difim suong cua khdng t^^tj, nfin tri lugng nudc lam mat ldn dfi phat huy hieu qua lam mat ciia thifit bi bay hoi lam mat ISSN 0866 - 7056 TAP CHf CO KHf VIET NAM Sd nam 2017 NGHIEN CU'U-TRAO D(!)l 2.4 Anh huong cua luu lirgng khdng den hieu qua lam viec ciia he thong Tuong tu, ling vdi nhifit nudc khdng ddi (trudng hgp t^^ < t^j < t^^^), ta cd mdi quan he giua luu lugng khdng Q^ va hifiu suat tao am r| tren Hinh va mdi quan he giira luu lugng luu lugng khdng Q^ va nhifit khdng khdi thifit bi lam mdt t^^^^^^ trfin Hmh Qua Hinh va ta thiy, iing vdi cac chfi luu lugng nudc khac nhau, viec tang luu lugng khdng dfiu din den nhiet khdng khdi thifit bi t^^^^ giam va hifiu suat tao am T] tang Viec cd the dugc giai thich tang luu lugng khdng khi, qua trinh bay hoi nudc tang din den giam nhifit an cua khdng khi, tir dd giiip nhifit khdng khdi thifit bi se giam va hieu qua lam mat tang 2.5 Anh h u ^ g cua ti sh giira liru luong nud'c va luu lugng khdng E den hi^u qua lam vific cua hfi thong Nfiu dinh nghia E la ti sd giua luu lugng nudc va luu lugng khdng vao thifit bi lam mat thi anh hudng cua nd den hifiu qua lam vific cua thifit bi dugc thfi hien tren Hinh 10, ling vdi trudng hgp nhiet nudc nSm giiia nhifit nhifit ke khd va nhifit nhifit ke udt cua khdng t^^^ < t^ < t^^ va Hinh 11, iing vdi trudng hgp nhifit dg nudc thap hon nhiet diem suong cua khdng t^ < t , 27 y'' y^ 26.8 S26.6 1 Z 26.A 26i 261 26 259 /" " ' t^r^ ^J ff Z' e,ii/s) -ằ-llZ5 -ã-973 -t-T70 -ã-6SS -^ô7 ã.1 0.2 03 04 05 0.G i:^ 0.8 0.9 11 U U 1 Hinh 10: Moi quan hi giiia t^^^, vd E dng vdi trudng hgp t^^