Tgp chi Khoa hoc - Cong nghe Thuy sdn So 2/2013
THONG BAO KHOA HOC
CAN CHINH ONG MAO CHO MAY LANH NEN HOfI CONG SUAT NHO
THE CALIBRATION OF CAPILLARY TUBES FOR LOW-POWER REFRIGERATING SYSTEMS
Tr&n Bai Tiin', Nguyen Dinh Khirang', Dang Nh^t Khanh' Ngay nhan bai: 06/3/2012; Ngay phan bien thong qua 05/12/2012; Ngay duyet dang. 15/5/2013
TOM T A T
Trong ky thudt. khi can thiet ke, lap ddt may lanh nen hai cong sudt nhd, viec cdn chinh ong mao cho phu hop v&i yeu cdu cong nghe con gap nhieu kho khdn vd chd yeu vdn lap ddt theo kinh nghiem. mdt rdt nhieu thai gian Bdi vietgi&i thifu phucmg phdp cdn chinh dng mao cho da dgng moi chdt lanh, nhiet do bay hen vd cang sudt cda mdy nen Ignh Kel qud cho thdy moi quan h^ giira chieu ddi ong mao v&i nhiet do bay hai la mot hdm so mu.
Tir khoa. he thdng lanh, dng mao. mdi chdt Ignh, nhiet do ABSTRACT
In engineering, installating or designing low-power refrigerating systems.how to calibrate capillary tubes thai meet tlie technological requirements is still difficult and mostly installed with personal experiences, which lakes plenty of time. This article introduces the method to calibrate the capillary lubes in various evaporation temperatures, refrlgeraiili and refrlgeralion compressors' power The results showed the relation between Ihe length of capillary tubes and evaporation temperatures in an exponential function.
Keywords' refrigerating system, capillary tube, refrigerant, lemperalure
I. DAT V A N D ^
6ng mao ed vai Ird nhu van tiet luu de eung cap moi c h l l Ignh cho thiet bi bay hai, mdi c h l l Ignh qua ong mao se giam tir i p suit ngung lu P,^ den dp suit bay hai suit P^nhu tren hinh 1
D j c h t u p t u a t u 6 i i g m a o p , , T B N T /
vao thiet b) bay hcri
X.
phii/loc " "•
Hinh 1. Su giam ip suat moi chat lanh qua ong mao
Khi mdy nen Ignh dirng sau mgt Ihdi gian ngin cdng nghe ein gap nhieu khd khan v i chu ylu dp suit hut va dly bing nhau, nen mdy nen khdi v i n ldp dat Iheo kinh nghiim, mit rit nhilu thii ding lgi d l ding. Do do cap dich bang dng mao gian. Theo kinh nghiem [1] can chinh ing mao phii hgp cho cic logi mdy Ignh cdng suit nho. Dac nhu tren hinh 2: tii Ignh diing mii c h l l Ignh R12 bigt I i dgng co mdy nen dung dien mgt pha nhu tij vdi nhiet do -6°C Ihi dp suit ndn trin ding ho Ignh gia dinh; Ihuang nghiep, tu kem; mdy dilu hoa P„^ = 130-150PSI;-12''CdpsuatP^„= 150+160PSI, khong khi eing suit nhd... tii kem, tu bao qudn ding dp suit p^"= 160H80PSI.
Trong Ihiel k l , ldp dat mdy lanh cdng suit nhd Nhung khi ein thay doi mii chat Ignh sang R134a;
vigc can chinh dng mao cho phti hgp vdi yeu elu R22; R404a vd nhidt do mdi trudng d n Idm Ignh...
' TS. Tran Dgi Tien,' KS. Nguyen Dinh Khuong, ^KS Dgng Nhat Khanh: Khoa Co khi - Trudng Dgi hgc Nha Trang
34 • TRUONG DAI HOC NHA TRANG
Tgp chi Khoa hoc - Cong nghe Thuy s So 2/2013
thi viic can chinh i n g mao Igi gap khd khan. Do dd vigc tim phuang phip can chinh dng mao Id v i n d l ein Uiilt md Ihuc te dat ra.II. D 6 | Tl/grNG VA PHU'ONG P H A P NGHIEN CO'U 1. O i l t u g n g nghien cu-u
Doi tugng nghien etru Id i n g mao ed dudng kinh trong vd ngodi tuang irng la 1,07 mm vd 1,60 mm, dugc thtr nghigm tren may nen lanh higu SANYO ciia Nhat cdng suit 1/6HP vdi mii c h l l lanh R134a, R404a.
2. Phyang phap nghien cu-u
Dung phuang phap thye nghiem de xac dinh ehieu ddi ong mao theo nhiet do bay hai thay d i i vd thye hign trin sa do cdn chinh i n g mao d hinh 2. De edn chinh ong mao c i n tinh dugc t i n I h l l i p suit qua ong mao.
^ = Pk~Po^^ "higt dg ngung ty t^ v i bay hai l^. Trong dd P,^ vd P^ Id dp suit ngung tu va bay hai
Khdng khi xa ra ngodi iBoi tnidng
Khdng khi hiit v ^
Hinh 2. Scr Ah can chinh dng mao
May ndn lanh edng suit nhi do dan ngung tu giai nhigt chu yeu bang khong khi, d dieu kien khi hdu Vigt Nam nhigt do ngung ty Ihudng vao khoang ttr 36 den 38°C.
Nlu nhiit dg mdi Irudng can Iim Ignh theo y i u elu eing nghg I i I,. Khi do nhiet dd bay hai 'Q = ^^ - A ^ Vdl d i n lanh tiep xiie trye tiep: A t = 2 -^ S^C, d i n lanh khdng khi: At = 8 -^ \ifC, dan lanh Idm lanh nude hay ehll long- At = 4 -^ 6*'C.[3].
Ttr nhiit do ngung lu t,, va bay hai t^ tra bang hai bao hda eiia mii ehll Ignh xdc dinh duge P^ vd P,,, higu dp suit A P - P^-PQ ehinh Id ton that dp suit qua i n g mao.
Tren hinh 2 cho thiy dp suit cua khdng khi trudc vd sau ong mao: /J = P^^^ +7^. = P^,+ p^ vd neu bd qua ton thiy dp suit tai cira ra ciia i n g mao Ihi /^ = / ^ Tu dd suy ra higu dp suit eiia khing khi trudc v i sau ing mao A P — /J ~ Pj— P„e„- Trong hg thong Ignh vdi mgt m i l ehat Ignh eho trudc Ihi l i n lhat dp suit qua ong mao Id: / i P = P^-P^. Hay can dieu chinh chieu ddi i n g mao d l dp suit nen tren ding h i P^.^ = AP - P^-P^
Iheo so do bo tri thi nghiem Uen hinh 3.
Sa d i b i tri thi nghigm 6ng mao
.1
Cit doan Han n i l vdi ing day cua may nin lanh Dilu chinh chilu ddi ong mao sao cho dp suit ndn
Pnen = Pk - PO
}
Xdc dinh chieu ddi i n g mao Hinh 3. So- dh b6 tri thi nghifm Ong mao co dudng kinh trong 1,07mm, tien hdnh c l l thdnh cdc dogn vd hdn n i l vdi i n g dly ciia
may nen Ignh nhu tren hinh 2. Cho mdy nin lanh ehgy sau do dieu ehinh ehieu ddi eOa i n g mao sao cho dp suit nen tren ding ho x l p xi bing higu dp suit: Pl, - Pa, Do chieu d i i dng mao, xu ly s i lieu de tim qui lugt sy bien doi giua chieu dai ing mao vdi nhigt dd bay hai.
111. K^T QUA NGHIEN CU'U VA T H A O L U A N 1. Sy b i l n doi chieu ddi ong mao theo nhiet dg bay hai vdl moi c h i t lanh R134a
Chpn niet dp ngung tu t,^ - 38°C. Tra bing cde thdng s i vat ly eiia hai bdo hoi mdi chit lanh RI 34a [2]; xac i^nh duge dp suit ngung tg P^, bay hai P.
TRL/ONG OAi HOC NHA TRANG • 35
Tap chi Khoa hoc - Cong nghe Thuy san
•mem&
So 2/2013
va hieu Sp suat theo nhiet d6 bay hai difoc the hi#n a bang 1.
Bang 1. Ap suat P,; P, va h i f u ap s u i t cua moi chat l?nh R134a tlieo nhi#t dO bay hon Nhift a$ bay lien
t . f c ) 0 -5
•10 -15 -20 -25
Ap s u i t ngi/ng t^ P, (PSI) efntti?td9n9i«igtut^ = 38'C
139,80 139,80 139,80 139,80 139,80 139,80
Ap s u i t l>ay lioi P. (PSI) 42,47 35,29 29,09 23,77 19,24 15,42
Hi$U dp s u i t p ^ = ap = p^-p,(PSl)
97,33 104,51 110,71 116,03 120,56 124,38 Sy biln d i i chilu dai ong mao theo nhiet d i bay hai ciia mdi c h l l Ignh R134a dirge Uil hiin d bang 2 vd trdn hinh 4 cho thiy nhigt do bay hai cdng thip Uii ehieu dai ong mao cang Idn.
Bdng 2. Bien doi c h i l u dai cua ong mao theo nhiet dg bay ho'i cua moi chat R134a Nhl0t ao bay hoi ("C)
Chl^u ddi ong mao (m)
Ap suit nen thipc te tr§n dong ho P^ (PSI) 0 1,00 95,3
-6 1,18 105,0
-10 1,41 115,0
-15 1,52 115,7
-20 1,70 120,8
-25 1,81 124,0 Dya vdo phin mem Excell vd sau khi xir ly s i liiu thu dugc mii quan he gida chieu ddi ong mao theo nhigt do bay hai Id mgt him s i mO co dgng: y = ©.gsee""'"; he so tuang quan: R^ = 0,959
Trong do y Id chieu d i i i n g mao (m); x Id nhigt d i bay hai (°C).
Nhi^td9bayboi(''C)
Hinh 4. Bien doi chilu dai ong mao theo nhiet do bay htfi vol moi chat lanh R134a, cdng suat may nen lanh 1/6HP va dirdrng kinh trong ciia dug mao l,07mmm
2. Sy b i l n dol chieu ddi ong mao theo nhi#t d i bay hai vdl mdi chat lanh R404a
Tra bang cac thdng so vat Iy cua hai mdi chll Ignh R404a [2]; dugc dp suit ngung lu P^,, bay hai Pg va higu dp suit theo nhiet dg bay hai duge I h l hign d bang 3.
Bang 3. Ap s u i t P^; P, vd higu dp s u i t cua moi chat Ignh R404a theo nhiet dg bay hoi Nhl$t d$ bay hoi
1.PC]
0 -5 -10 -15 -20 -25
Ap s u i t ngimg t^ P^ (PSI) i, nhi#t d9 ngimg t^ t^ = 38°C
253,41 253,41 253,41 253,41 253,41 253,41
Ap s u i t bay hoi P. (PSI) 89 76 64 54 45 38
Hi#u dp s u i t P^ = AP = P.-P,(PSI)
164,17 177,39 189,09 199,42 208,39 215,83 Sy bien d i i ehieu d i i ong mao theo nhidt dg bay hai cua mdi chat Ignh R404a dugc t h i hiin d bdng 4 vd trdn hinh 5 eho thay nhigt dp bay hai cing thap thi chiiu dai i n g mao cdng ldn. Nhung ciing nhigt do bay hai diieu d i i ing mao dimg mdi chit lanh R404a Idn ban dang ke so vdi R134a. Nhu d -10°C vdi R404a cd chilu
36 • TRUONG OAI HOC NHA TRANG
Tgp chi Khoa hoc - Cong nghe Thuy sdn So 2/2013
d i l la 3,41m, trong khi dd R134a chi dai 1,41m. C o s y khac bigt tren Id do sy gdm dp suit qua ong mao dting m i i c h l l Ignh R404a Id 187PSI Idn ban so vdi R134a cd sy giim dp suit Id 115PSI.Bang 4. Bien doi chleu dai cua ong mao theo nhigt do bay hai cua m i l chat R404a Nhl?t do bay hcyi (°C)
Chieu ddi ong mao (m)
Ap suit nen thu'c t l tren d6ng ho P„^„ (PS!) 0 2,96 170,2
-5 3.16
180 -10 3,41 187
-15 3,57 200,3
-20 3,79 207,8
-25 4,08 215,5
?5
is
BD « 1
• < © •*
y = 2.78996"™"
R^ = 0.9963
-5 -10 -15 -20 Nhijt dg bay hiri (°C)
Hinh 5. Bien doi chieu dii ong mao fheo nhiet dg voi moi chit lanh R404a, cong suit mdy nen lanh l/6HPv^ dtr^mg kinh trong cua ong mao l,07mmm
Dua v i o phan mem Excell vd sau khi xCr I^ so lieu thu dugc m i l quan he gitra chieu ddi ing mao theo nhiet dg bay hai Id m i l hdm s i mu cd dgng. y = 2,789e''''"'^; he so tuong quan R' = 0,996.
Nhu vgy de xac dinh chieu dai ong mao can tien hdnh nhu sau'
Xde djnh nhiit dg ngung ty 1,^, bay hai t^,. Nhi^t d i bay hoi dugc xdc djnh tir nhiit d i mii trudng can Idm Ignh I,.
Chon mdi chat Ignh, tinh nang suit lanh yeu c l u Q^ d l tir dd chgn edng suit m i y ndn lanh ein thill.
Ttr nhigt d i 1^ vd I,,; Tra bang eac thing so vat Iy eua mdi ehat Ignh de x i e dinh ap suit ngung ty P^ v i bay hai P^; Tinh higu ap suit AP = P^ - P^.
- Chgn dudng kinh ong mao sau dd can ehinh x i e dinh chieu dai i n g mao.
IV. K£T LUAN
Phuang phap can chinh i n g mao trin da giiip cho ngudi ky thuat xie djnh dugc chilu dai ong mao eho edc logi mdy Ignh cing suit nhd vdi c i c moi chit Ignh thudng dung R134a; R404a... khi nhiet do mdi trudng c i n lam Ignh thay d i i mgt cdch thugn Igi vd nhanh chdng.
TAI LIEU THAM KHAO
1. Nguyen Ditc Lgi, Phgm Van Tiiy, Tii lanli, may kem, may da, may dieu hoa nhiet do, t-JXB Khoa hgc vi 2. Nguyin Diic Lgri, Ga diu va chdt tai lanh, NXB Giao dye 2006
3 Komondy Halasz, Hfltogepek, Tankonyvkiad6, Budapest, 1981
TRLTONG DAl HOC NHATRANG • 37