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7/22/2019 Tinh Toan Tke Hthong Dieu Hoa Khong Khi
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Ts. V ch chnh
Tnh ton thit kH thngIU HO KHN KH
NNG, NM 2003
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1
CHNG INHNG KIN THC C BAN VKHNG KH M
iu hoa khng kh lakythut tao ra vaduy tr iu kin vi kh hu thch hp vi conngi vacng nghcua cac quatrnh san xut.
cothi su nghin cu kythut iu hoakhng kh trc ht chung ti s lc cactnh cht nhit ng c ban cua khng kh m.
1.1 KHNG KH MKhng kh xung quanh chung ta lahn hp cua nhiu cht kh, chuyu laN2vaO2 ngoai
ra con mt lng nhocac kh tr, CO2, hi nc . . .-Khng kh kh: Khng kh khng cha hi nc goi lakhng kh kh.Trong cac tnh
toan thng khng kh kh c coi lakh lytng.Thanh phn cua cac cht trong khng kh kh c phn theo tylsau :
Bang 1-1 : Tylcac cht kh trong khng kh khThanh phn Theo khi lng (%) Theo thtch (%)- Ni t : N2- xi : O2- Argon - A- Carbon-Dioxide : CO2
75,523,11,30.1
78,08420,9480,934
0,0314
-Khng kh m: Khng kh cocha hi nc goi lakhng kh m. Trong tnhin khngcokhng kh kh tuyt i matoan lakhng kh m. Khng kh m c chia ra :
+ Khng kh m cha bao hoa : Latrang thai mahi nc con cothbay hi thm vao
c trong khng kh.+ Khng kh m bao hoa : Latrang thai mahi nc trong khng kh aat ti a vakhng thbay hi thm vao oc. Nu bay hi thm vao bao nhiu th coby nhiu him ngng tulai.
+ Khng kh m quabao hoa : Lakhng kh m bao hoa vacon cha thm mt lnghi nc nht nh. Tuy nhin trang thai quabao hoalatrang thai khng n nh macoxuhng bin i n trang thai bao hoado lng hi nc d b tach dn ra khoi khng kh .V dunh sng mulakhng kh quabao hoa.
Tnh cht vt lyvaanh hng cua khng kh n cam giac con ngi phuthuc nhiuvao lng hi nc tn tai trong khng kh.
1.2 CAC THNG SCUA KHNG KH M1.2.1 Ap sut.
Ap sut khng kh thng c goi lakh ap. Kyhiu laB. Noi chung giatr B thay itheo khng gian vathi gian. Tuy nhin trong kythut iu hoa khng kh giatr chnh lchkhng ln cothboqua vangi ta coi B khng i. Trong tnh toan ngi ta ly trangthai tiu chun Bo= 760 mmHg .
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th I-d cua khng kh m thng c xy dng ap sut B = 745mmHg vaBo =760mmHg .
1.2.2 Khi lng ring vathtch ring.Khi lng ring cua khng kh lakhi lng cua mt n v thtch khng kh . Kyhiu
la, n v kg/m3.ai lng nghch ao cua khi lng ring lathtch ring. Kyhiu lav
Khi lng ring vathtch ring lahai thng sphuthuc.Khi lng ring thay i theo nhit vakh ap. Tuy nhin cung nh ap sut sthay i
cua khi lng ring cua khng kh trong thc tkythut khng ln nn ngi ta ly khngi iu kin tiu chun : to= 20oC vaB = Bo= 760mmHg : = 1,2 kg/m3
1.2.3 m1.2.3.1. m tuyt i .
Lakhi lng hi m trong 1m3khng kh m. Gias trong V (m3) khng kh m co
cha Gh(kg) hi nc th m tuyt i kyhiu lah c tnh nh sau :
V hi nc trong khng kh cothcoi lakh lytng nn:
trong o:ph- Phn ap sut cua hi nc trong khng kh cha bao hoa, N/m2Rh- Hng scua hi nc Rh= 462 J/kg.oK
T - Nhit tuyt i cua khng kh m, tc cung lanhit cua hi nc , oK
1.2.3.2. m tng i.m tng i cua khng kh m , kyhiu la(%) lat s gia m tuyt i h
cua khng kh vi m bao hoa maxcung nhit vi trang thai acho.
hay :
m tng i biu th mc cha hi nc trong khng kh m so vi khng kh mbao hoa cung nhit .
Khi = 0 olatrang thai khng kh kh.0 < < 100 olatrang thai khng kh m cha bao hoa.= 100 olatrang thai khng kh m bao hoa.
kgmv /,1 3
=
3/, mkgV
Gh
h =
3/,.
1mkg
TR
p
vh
h
h
h ==
,%max
h=
,%maxp
ph=
(1-1)
(1-2)
(1-3)
(1-4)
(1-5)
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- m laai lng rt quan trong cua khng kh m coanh hng nhiu n cam giaccua con ngi vakhanng s dung khng kh sy cac vt phm.
- m tng i cothxac nh bng cng thc, hoc o bng m k. m klathitb o gm 2 nhit k : mt nhit kkh vamt nhit kt. Nhit kt co bu boc vaithm nc ohi nc thm vai boc xung quanh bu nhit kkhi bc hi vao khng khsely nhit cua bu nhit knn nhit bu giam xung bng nhit nhit kt tng
vi trang thai khng kh bn ngoai. Khi m tng i be, cng bc hi cang manh,chnh nhit gia 2 nhit k cang cao. Do ochnh nhit gia 2 nhit kphuthuc vao m tng i vanoc sdung lam c sxac nh m tng i .Khi =100%, quatrnh bc hi ngng vanhit cua 2 nhit kbng nhau.
1.2.4 Dung m (cha hi).Dung m hay con goi lacha hi, c kyhiu lad lalng hi m cha trong 1 kg
khng kh kh.
- Gh: Khi lng hi nc cha trong khng kh, kg- Gk: Khi lng khng kh kh, kg
Ta coquan h:Sau khi thay R = 8314/ta co
1.2.5 Nhit .Nhit laai lng biu th mc nong lanh. y layu tanh hng ln nht ncam giac cua con ngi. Trong kythut iu hoa khng kh ngi ta thng sdung 2 thangnhit laC va F. i vi mt trang thai khng kh nht nh nao ongoai nhit thc cua no trong ky thut con co2 giatr nhit coanh hng nhiu n cac hthng vathit b lanhit im sng vanhit nhit kt.
- Nhit im sng: Khi lam lanh khng kh nhng ginguyn dung m d (hoc phnap sut ph) ti nhit ts nao ohi nc trong khng kh bt u ngng tuthanh nc baohoa. Nhit tsogoi lanhit im sng.
Nh vy nhit im sng cua mt trang thai bt kynao olanhit ng vi trang
thai bao hoa vacodung m bng dung m cua trang thai acho. Hay noi cach khac nhit im sng lanhit bao hoa cua hi nc ng vi phn ap sut phacho. Ty ta thygia tsvad comi quan hphuthuc.
- Nhit nhit kt : Khi cho hi nc bay hi oan nhit vao khng kh cha baohoa (I=const) . Nhit cua khng kh segiam dn trong khi m tng i tng ln. Titrang thai = 100% quatrnh bay hi chm dt. Nhit ng vi trang thai bao hoacui
kgkkkkgG
Gd
k
h /,=
h
k
k
h
k
h
k
h
R
R
p
p
G
Gd .===
kgkkkkgpp
p
p
pd
h
h
k
h /,.622,0
==
(1-6)
(1-7)
(1-8)
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cung nay goi lanhit nhit nhit kt vakyhiu lat. Ngi ta goi nhit nhit kt lav noc xac nh bng nhit kcobu thm t nc.
Nh vy nhit nhit kt cua mt trang thai lanhit ng vi trang thai bao hoa vaco entanpi I bng entanpi cua trang thai acho. Gia entanpi I vanhit nhit kt tcomi quan hphuthuc. Trn thc t ta co tho c nhit nhit kt cua trang thaikhng kh hin thi lanhit trn bmt thoang cua nc.
1.2.6 EntanpiEntanpi cua khng kh m bng entanpi cua khng kh kh vacua hi nc cha trong no.Entanpi cua khng kh m c tnh cho 1 kg khng kh kh. Ta cocng thc:
I = Cpk.t + d (ro+ Cph.t) kJ/kg kkkTrong o:
Cpk- Nhit dung ring ng ap cua khng kh kh Cpk= 1,005 kJ/kg.oCCph- Nhit dung ring ng ap cua hi nc 0oC : Cph= 1,84 kJ/kg.oCro- Nhit n hoa hi cua nc 0oC : ro= 2500 kJ/kg
Nh vy:
I = 1,005.t + d (2500 + 1,84.t) kJ/kg kkk
1.3 TH I-d VA t-d CUA KHNG KH M1.3.1 th I-d.th I-d biu th mi quan hcua cac ai lng t, , I, d vapbhcua khng kh m .
th c giao s L.K.Ramzin (Nga) xy dng nm 1918 va sau o c giao s Mollier(c) lp nm 1923. Nhth nay ta cothxac nh c tt cacac thng scon lai cuakhng kh m khi bit 2 thng sbt ky. th I-d thng c cac nc ng u vaLinx (cu) sdung.
th I-d c xy dng ap sut kh quyn 745mmHg va760mmHg.
th gm 2 truc I va d nghing vi nhau mt goc 135o. Muc ch xy dng cac trucnghing mt goc 135olanhm lam gian khoang cach gia cac ng cong tham sthunli cho vic tra cu.
Trn th nay cac ng I = const nghing vi truc hoanh mt goc 135o, ng d = constlanhng ng thng ng. i vi th I-d c xy dng theo cach trn cho thy cacng tham shu nh ch nm trn goc 1/4 thnht .V vy, hnh vec gon ngi taxoay truc d lai vung goc vi truc I mavn ginguyn cac ng cong nh abiu din, tuynhin khi tra cu entanpi I cua khng kh ta vn tra theo ng nghing vi truc hoanh mtgoc 135o.
Trn th I-d cac ng ng nhit t=const lanhng ng thng chch ln trn , cac
ng = const la nhng ng cong li, cang ln trn khoang cach gia chung cang xa.Cac ng = const khng ct nhau vakhng i qua gc toa. i ttrn xung di m cang tng. ng cong =100% hay con goi lang bao hoangn cach gia 2 vung :Vung cha bao hoavavung ngng kt hay con goi lavung sng mu. Cac im nm trongvung sng muthng khng n nh macoxung hng ngng kt bt hi nc vachuynvtrang thai bao hoa.
Khi ap sut kh quyn thay i th th I-d cung thay i theo. Ap sut kh quyn thayi trong khoang 20mmHg th sthay i olakhng ang k.
(1-9)
(1-10)
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Trn hnh 1.1 la th I-d cua khng kh m , xy dng ap sut kh quyn Bo=760mmHg. Trn th nay xung quanh con covethm cac ng =const giup cho tracu cac s tun hoan khng kh trong chng 4.
Hnh 1.1 : th I-d cua khng kh m
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1.3.2 th d-t.th d-t c cac nc Anh, My, Nht, Uc ...vv sdung rt nhiuth d-t co2 truc d vat vung goc vi nhau , con cac ng ng entanpi I=const tao
thanh gc 135oso vi truc t. Cac ng = const lanhng ng cong tng tnh trn th I-d. Cothcoi th d-t lahnh anh cua th I-d qua mt gng phan chiu.
Hnh 1.2 : th t-d cua khng kh m
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A
=100%
d
C
IAI
45
D
B
BI
th d-t chnh lath t-d khi xoay 90o, c Carrrier xy dng nm 1919 nn thngc goi lath Carrier.
Truc tung lacha hi d (g/kg), bn canh lahsnhit hin SHF (Sensible)Truc hoanh lanhit nhit kkh t (oC)
Trn th cocac ng tham s- ng I=const tao vi truc hoanh mt goc 135o. Cac giatr entanpi cua khng kh cho
tbn canh ng =100%, n v kJ/kg khng kh kh- ng =const la nhng ng cong lom, cang i ln pha trn (d tng) cang ln.Trn ng =100% lavung sng mu.
- ng thtch ring v = const lanhng ng thng nghing song song vi nhau, n vm3/kg khng kh kh.
- Ngoai ra trn th con co ng Ihc la ng hiu chnh entanpi (s sai lch giaentanpi khng kh bao hoavacha bao hoa)
1.4 MT SQUATRNH C BAN TRN TH I-d1.4.1 Quatrnh thay i trang thai cua khng kh .
Quatrnh thay i trang thai cua khng kh m ttrang thai A (tA, A) n B (tB, B) cbiu th bng oan thng AB, mui tn ch chiu quatrnh goi latia quatrnh.
Hnh 1.3 : Yngha hnh hoc cua
t (IA- IB)/(dA-dB) = I/d =AB goi lahsgoc tia cua quatrnh ABTa hay xet yngha hnh hoc cua hsABKyhiu goc gia tia AB vi ng nm ngang la. Ta coI = IB- IA = m.ADd= dB- dA = n.BC
Trong om, n lat lxch cua cac truc toa.Ty ta co
AB= I/d = m.AD/n.BCAB= (tg+ tg45o).m/n = (tg+ 1).m/n
Nh vy trn truc toaI-d cothxac nh tia AB thng qua giatr AB. tin cho vicsdung trn th ngoai bin ngi ta vethm cac ng = const . Cac ng = constcocac tnh cht sau :
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- Hsgoc tia phan anh hng cua quatrnh AB, mi quatrnh comt giatr nhtnh.
- Cac ng cotr snh nhau th song song vi nhau.- Tt cacac ng u i qua goc toa (I=0 vad=0).
1.4.2 Quatrnh hoa trn hai dong khng kh.
Trong kythut iu hoa khng kh ngi ta thng gp cac qua trnh hoa trn 2 dongkhng kh cac trang thai khac nhau at c mt trang thai cn thit. Quatrnh nay goilaquatrnh hoatrn.
Giashoa trn mt lng khng kh trang thai A(IA, dA) cokhi lng phn kh laLAvi mt lng khng kh trang thai B(IB, dB) cokhi lng phn kh laLBvathu c mtlng khng kh trang thai C(IC, dC) cokhi lng phn kh laLC. Ta xac nh cac thngscua trang thai hoatrn C.
Hnh 1.4 : Quatrnh hoatrn trn th I-d
Ta cocac phng trnh:- Cn bng khi lng
LC= LA+ LB (1-11)- Cn bng m
dC.LC= dA.LA+ dB.LB (1-12)- Cn bng nhit
IC.LC= IA.LA+ IB.LB (1-13)
Th(a) vao (b), (c) vatrtheo v ta co:(IA - IC).LA= (IC - IB).LB(dA - dC).LA= (dC - dB).LB
hay :
Tbiu thc nay ta rut ra:BC
BC
CA
CA
dd
II
dd
II
=
A
B
BC
CA
BC
CA
L
L
dd
dd
II
II=
=
(1-14)
(1-15)
d
I
AI
A
I
B
IC
B
d d dACB
C =100%
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- Phng trnh (1-14) lacac phng trnh ng thng AC vaBC, cac ng thng nay cocung hsgoc tia vachung im C nn ba im A, B, C thng hang. im C nm trn oan
AB.- Theo phng trnh (1-15) suy ra im C nm trn AB vachia oan AB theo tylLB/LA
Trang thai C c xac nh nh sau :
* * *
C
BB
C
AAC
L
LI
L
LII .. +=
C
B
B
C
A
ACL
Ld
L
Ldd .. +=
(1-16)
(1-17)
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CHNG 2MI TRNG KHNG KH VACHON THNG S
TNH TOAN CHO CAC HTHNG IU HOA
thit khthng iu hoakhng kh cn phai tin hanh chon cac thng stnh toan
cua khng kh ngoai tri vathng stin nghi trong nha. Cac thng sobao gm:- Nhit t (oC) . - m tng i (%) .- Tc chuyn ng khng kh trong phong (m/s) .- n cho phep trong phong Lp(dB) .- Lng kh ti cung cp LN(m
3/s) .- Nng cho phep cua cac cht c hai trong phong .
2.1 ANH HNG CUA MI TRNG TI CON NGI VASAN XUT2.1.1 Anh hng cua mi trng n con ngi
2.1.1.1 Nhit .Nhit layu tgy cam giac nong lanh i vi con ngi. C thcon ngi conhitlatct= 37oC. Trong quatrnh vn ng c thcon ngi lun lun toara nhit lng qtoa.Lng nhit do c thtoara phuthuc vao cng vn ng. duy tr thn nhit c ththng xuyn trao i nhit vi mi trng. Strao i nhit osebin i tng ng vicng vn ng. Co2 hnh thc trao i nhit vi mi trng xung quanh.
- Truyn nhit : Truyn nhit t c th con ngi vao mi trng xung quanh di 3cach: dn nhit, i lu vabc xa. Noi chung nhit lng trao i theo hnh thc truyn nhitphuthuc chuyu vao chnh nhit gia c thvami trng xung quanh. Lng nhittrao i nay goi lanhit hin . Kyhiu qh
Khi nhit mi trng tmtnhohn thn nhit, c th truyn nhit cho mi trng, khinhit mi trng ln hn thn nhit th c thnhn nhit tmi trng. Khi nhit mitrng be, t = tct-tmtln, qhln, c thmt nhiu nhit nn cocam giac lanh vangc lai khinhit mi trng ln khanng thai nhit ra mi trng giam nn cocam giac nong. Nhithin qhphu thuc vao t = tct-tmtva tc chuyn ng cua khng kh . Khi nhit mitrng khng i, tc khng kh n nh th qhkhng i. Nu cng vn ng cuacon ngi thay i th lng nhit hin qhkhng thcn bng vi lng nhit do c th sinhra. thai ht nhit lng do c thsinh ra, cn cohnh thc trao i th2, olatoam.
- Toa m : Ngoai hnh thc truyn nhit c th con trao i nhit vi mi trng xungquanh thng qua toa m. Tom cothxay ra trong moi pham vi nhit vakhi nhit mi
trng cang cao th cng cang ln. Nhit nng cua c thc thai ra ngoai cung vi hinc di dang nhit n, nn lng nhit nay c goi lanhit n. Kyhiu qw.
Ngay cakhi nhit mi trng ln hn 37oC, c thcon ngi vn thai c nhit rami trng thng qua hnh thc toa m, olathoat mhi . Ngi ta atnh c rng cthoat 1 g mhi th c ththai c mt lng nhit xp x 2500J. Nhit cang cao, mmi trng cang beth mc thoat mhi cang nhiu.
Nhit n cogiatr cang cao khi hnh thc thai nhit bng truyn nhit khng thun li.
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Tng nhit lng truyn nhit vatoa m phai am bao lun lun bng lng nhit do cthsan sinh ra.
Mi quan hgia 2 hnh thc phai lun lun am bao :qtoa= qh+ qW
y lamt phng trnh cn bng ng, giatr cua mi mt ai lng trong phng trnhcoththay i tuythuc vao cng vn ng, nhit , m, tc chuyn ng cua
khng kh mi trng xung quanh...vvNu v mt lydo g omt cn bng th segy ri loan vasinh au mNhit thch hp nht i vi con ngi nm trong khoang 22-27 oC .
2.1.1.2 m tng im tng i coanh hng quyt nh ti khanng thoat mhi vao trong mi trng
khng kh xung quanh. Quatrnh nay ch cothtin hanh khi < 100%. m cang thpth khanng thoat mhi cang cao, c thcam thy dchu.
m quacao, hay quathp u khng tt i vi con ngi.- m cao : Khi m tng ln khanng thoat mhi kem, c thcam thy rt nng n
, mt moi vadgy cam cum. Ngi ta nhn thy mt nhit vatc giokhng ikhi m ln khanng bc mhi chm hoc khng thbay hi c, iu olam cho bmt da colp mhi nhp nhap.
- m thp :Khi m thp mi hi sebay hi nhanh lam da kh, gy nt nechn tay,mi ...vv. Nh vy m quathp cung khng tt cho c th.
m thch hp i vi c thcon ngi nm trong khoang tng i rng = 5070%.
2.1.1.3 Tc khng khTc khng kh xung quanh coanh hng n cng trao i nhit vatrao i
cht (thoat mhi) gia c thcon ngi vi mi trng xung quanh. Khi tc ln cng
trao i nhit m tng ln. V vy khi ng trc giota cam thy mat vathng da khhn ni yn tnh trong cung iu kin vm vanhit .
Khi nhit khng kh thp, tc qualn th c thmt nhit gy cam giac lanh. Tcgiothch hp tuy thuc vao nhiu yu t: nhit gio, cng lao ng, m, trangthai sc khoe cua mi ngi. . .vv.
Trong kythut iu hoa khng kh ngi ta ch quan tm tc giotrong vung lam vic,tc lavung di 2m ktsan nha. y lavung mamt ngi bt kykhi ng trong phongu lot thom vao trong khu vc o.
2.1.1.4 Nng cac cht c hai.
Khi trong khng kh cocac cht c hai chim mt tylln th nosecoanh hng nsc khoe con ngi. Mc tac hai cua mi mt cht tuy thuc vao ban cht cht kh, nngcua notrong khng kh, thi gian tip xuc cua con ngi, tnh trang sc khoe ...vv.
Cac cht c hai bao gm cac cht chuyu sau :- Bui: Bui anh hng n hh hp . Tac hai cua bui phuthuc vao ban cht bui, nng
vakch thc cua no. Kch thc cang nhoth cang cohai v notn tai trong khng khlu vakhanng thm nhp vao c th su hn vart khokh bui. Hat bui ln th khanngkhddang hn nn t anh hng n con ngi. Bui co2 ngun gc hu c vav c.
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- Kh CO2, SO2 . . Cac kh nay khng c, nhng khi nng cua chung ln th se lamgiam nng O2trong khng kh, gy nn cam giac mt moi. Khi nng qua ln cothdn n ngat th.
- Cac cht hai khac :Trong quatrnh san xut vasinh hoat trong khng kh cothcoln cac cht c hai nh NH3, Clo . . vv lanhng cht rt cohai n sc khoe con ngi.
Cho ti nay khng cotiu chun chung anh giamc anh hng tng hp cua cac
cht c hai trong khng kh.Tuy cac cht c hai conhiu nhng trn thc ttrong cac cng trnh dn dung cht chai phbin nht olakh CO2do con ngi thai ra trong quatrnh h hp. V thtrong kythut iu hoangi ta chuyu quan tm n nng CO2.
anh giamc nhim ngi ta da vao nng CO2cotrong khng kh.Bang 2.1 trnh bay mc anh hng cua nng CO2trong khng kh . Theo bang nay
khi nng CO2trong khng kh chim 0,5% theo thtch lagy nguy him cho con ngi.Nng cho phep trong khng kh la0,15% theo thtch.
Bang 2.1 : Anh hng cua nng CO2trong khng kh
Nng CO2% thtch
Mc anh hng
0,07 - Chp nhn c ngay cakhi conhiu ngi trong phong0,10 - Nng cho phep trong trng hp thng thng0,15 - Nng cho phep khi dung tnh toan thng gio
0,20-0,50 - Tng i nguy him> 0,50 - Nguy him4 5 - H thn kinh b kch thch gy ra th su va nhp th gia
tng. Nu ht thtrong mi trng nay keo dai th cothgy
ra nguy him.8 - Nu th trong mi trng nay keo dai 10 phut th mt o
bng vaau u18 hoc ln hn - Ht sc nguy him cothdn ti tvong.
2.1.1.5 nNgi ta phat hin ra rng khi con ngi lam vic lu dai trong khu vc con cao th
lu ngay c thsesuy sup, cothgy mt sbnh nh : Stress, bn chn vagy cac ri loan
gian tip khac. n tac ng nhiu n hthn kinh. Mt khac khi n ln cothlamanh hng n mc tp trung vao cng vic hoc n gian hn lagy skhochu cho conngi. V ducac m thanh cua quat trong phong th vin nu qualn se lam mt tp trungcua ngi oc vart khochu.
V vy n lamt tiu chun quan trong khng thboqua khi thit kmt h thngiu hoa khng kh. c bit cac hthng iu hoacho cac ai phat thanh, truyn hnh, cacphong studio, thu m thu li th yu cu vn laquan trong nht.
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2.1.2 Anh hng cua mi trng n san xut.Con ngi lamt yu tv cung quan trong trong san xut. Cac thng skh hu coanh
hng nhiu ti con ngi congha cung anh hng ti nng sut vacht lng san phmmt cach gian tip.
Ngoai ra cac yu tkh hu cung anh hng trc tip ti cht lng san phm. Trong phnnay chung ta ch nghin cu kha canh nay.
2.1.2.1. Nhit Nhit coanh hng n nhiu loai san phm. Mt squatrnh san xut oi hoi nhit
phai nm trong mt gii han nht nh. V du:- Keo Scla : 7 - 8 oC- Keo cao su : 20oC- Bao quarau qua: 10oC- o lng chnh xac : 20 - 24 oC- Dt : 20 - 32oC- Chbin tht, thc phm : Nhit cao lam san phm chong b thiu .
Bang 2.2 di y latiu chun vnhit vam cua mt squatrnh san xut thnggp
Bang 2.2 : iu kin cng nghcua mt squatrnh
Quatrnh Cng nghsan xut Nhit , oC m, %
Xng in- ong vagoi sach- Phong in n- Ni lu trgiy- Phong lam ban kem
21 2424 2720 3321 33
4545 5050 6040 50
San xut bia- Ni ln men- Xlymalt- Uchn- Cac ni khac
3 410 1518 2216 24
50 7080 8550 6045 65
Xng banh- Nhao bt- ong goi- Ln men
24 2718 24
27
45 5550 6570 80
Chbin thc phm- Chbin b- Mayonaise- Macaloni
1624
21 27
6040 50
38
Cng nghchnh xac - Lp rap chnh xac- Gia cng khac
20 2424
40 5045 55
Xng len- Chun b- Keo si- Dt
27 2927 2927 29
6050 6060 70
Xng si bng- Chai si- Xe si- Dt vaiu tit cho si
22 2522 2522 25
55 6560 7070 90
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- Theo chc nng :+ Hthng iu hoacuc b :Lahthng nhoch iu hoa khng kh trong mt khng
gian hep, thng lamt phong. Kiu iu hoacuc btrn thc tchuyu sdung cac mayiu hoadang ca s, may iu hoakiu ri (2 manh) vamay iu hoaghep.
+ H thng iu hoaphn tan :Hthng iu hoa khng kh makhu xlynhit mphn tan nhiu ni. Cothv duhthng iu hoakhng kh kiu khuych tan trn thc t
nh hthng iu hoakiu VRV (Variable Refrigerant Volume ) , kiu lam lanh bng nc(Water chiller) hoc kt hp nhiu kiu may khac nhau trong 1 cng trnh.+ Hthng iu hoatrung tm : Hthng iu hoatrung tm lahthng makhu xly
khng kh thc hin tai mt trung tm sau oc dn theo hthng knh dn gion cachtiu thu. Hthng iu hoatrung tm trn thc tlamay iu hoadang tu, okhng khc xlynhit m tai tumay iu hoari c dn theo hthng knh dn n cac phong.2.3 CHON THNG STNH TOAN CAC HTHNG IU HOAKHNG KH
Vic chon cac thng stnh toan bao gm thng stnh toan trong nhavangoai tri. ivi thng stnh toan trong nhatuythuc vao muc ch cua hthng iu hoa.
- i vi h thng iu hoadn dung, tc lah thng iu hoach nhm muc ch tao
iu kin tin nghi cho con ngi. Cac thng stnh toan trong nhac la chon theo cactiu chun senu bang 2-3 di y.
- i vi hthng iu hoacng nghip , tc hthng iu hoaphuc vucng nghcuamt quatrnh san xut cuth. Trong trng hp nay , ngi thit kphai ly sliu thc ttnhasan xut lachnh xac vaphuhp nht . Cac thng stnh toan nay coththam khao bang dliu 1.2.
2.3.1 Chon nhit vam tnh toan2.3.1.1. Nhit vam trong nha
Nhit vam trong nhac chon tuythuc vao chc nng cua phong. Cothchonnhit vam trong nhatheo bang 2.3:
Bang 2.3 Nhit vam tnh toan trong phongMUA HE
Hang sang Bnh thngMUA NG
KHU VCtT,
oC , % tT,oC , % tT,
oC , %Khu cng cng : Chungc, Nha, Khach san, Vnphong, Bnh vin, trnghoc
23 24
45 50
25 26
45 50
23 25 30 35
Ca hang, ca hiu :Ngn hang, cua hang banhkeo, myphm, siu th
24 26
45 50
25 27
45 50
22 24 30 35
Phong thu m thu li, Nhath, Quan bar, nha hang,nhabp. . .
24 26
50 55
26 27
50 60
22 24 35 40
Nha may, phn xng, xnghip 25 27
45 55
27 29
50 60
20 23 30 35
2.3.1. 2 Nhit vam ngoai tri
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Thng sngoai tri c sdung tnh toan tai nhit c cn cvao tm quan trongcua cng trnh, tc latuy thuc vao cp cua hthng iu hoa khng kh valy theo bang 2-4 di y:
Bang 2.4 Nhit vam tnh toan ngoai triHthng Nhit tN,
oC m N, %Hthng cp I
+ Mua he+ Mua ng tmaxtmin
(tmax)(tmin)
Hthng cp II+ Mua he+ Mua ng
0,5(tmax+ ttb
max)0,5(tmin+ t
tbmin)
0,5[(tmax) + (ttb
max)]0,5[(tmin) + (t
tbmin)]
Hthng cp III+ Mua he+ Mua ng
ttbmaxttbmin
(ttbmax)(ttbmin)
Trong o:tmax, tmin Nhit ln nht vanhonht tuyt i trong nm o luc 1315 gi, tham khao
phuluc PL-1ttbmax, t
tbmin Nhit cua thang nong nht trong nm, tham khao phuluc PL-2, vaPL-3.
(tmax) , (tmin ) m ng vi nhit ln nht vanhonht tuyt i trong nm. Tuynhin do hin nay cac s liu nay Vit Nam cha co nn co th ly bng (ttbmax) va(ttbmin)(ttbmax) , (t
tbmin) m trung bnh ng vi thang conhit ln nht vanhonht trong
nm, tham khao phuluc PL-4
2.3.2 Chon tc khng kh tnh toan trong phongTc khng kh lu ng c la chon theo nhit khng kh trong phong nu
bang 2.5. Khi nhit phong thp cn chon tc gionho, nu tc qualn c thmtnhiu nhit, se anh hng sc khoecon ngi.
coc tc hp ly cn chon loai ming thi phuhp vabtr hp ly.
Bang 2.5 Tc tnh toan cua khng kh trong phong
Nhit khng kh, oC Tc k, m/s16 2021 2324 25
26 2728 30
> 30
< 0,250,25 0,30,4 0,6
0,7 1,01,1 1,31,3 1,5
2.3.3 n cho phep trong phong
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n coanh hng n trang thai vamc tp trung vao cng vic cua con ngi. Mcanh hng otuythuc vao cng vic ang tham gia, hay noi cach khac latuythuc vaotnh nng cua phong.
Ngi ta aqui nh n cho phep cho tng khu vc iu hoa nht nh nu bang 2.6.i vi cac may cng sut ln, khi chon cn xem xet n cua may coam bao yu cu
lp t vao v tr hay khng. Trong trng hp n qualn cn cocac bin phap khn
cn thit hoc lp t phong may ring bit.
Bang 2.6 n cho phep trong phongn cc ai cho phep,
dBKhu vcGitrong
ngayCho phep Nn chon
- Bnh vin, Khu iu dng 6 - 2222 - 6
3530
3030
- Giang ng, lp hoc 40 35- Phong may vi tnh 40 35
- Phong lam vic 50 45- Phn xng san xut 85 80- Nhahat, phong hoa nhac 30 30- Phong hi thao, hi hop 55 50- Rap chiu bong 40 35- Phong 6 - 22
22 - 64030
3030
- Khach san 6 - 2222 - 6
4540
3530
- Phong n ln, quan n ln 50 452.3.4 Nng cac cht c hai.
anh giamc nhim ngi ta da vao nng CO2cotrong khng kh, v CO2lacht c hai phbin nht do con ngi thai ra trong quatrnh sinh hoat vasan xut.
Lu lng khng kh ti cn thit cung cp cho 1 ngi trong 1 gic xac nh nhsau :
VK= VCO2/ (-a) (2-1)y :- VCO2lalng CO2do con ngi thai ra : m
3/h.ngi- Nng CO2cho phep, % thtch. Thng chon = 0,15
- a Nng CO2 trong khng kh mi trng xung quanh, % th tch. Thng chona=0,03%.- VKLu lng khng kh cn cp, m
3/h.ngiLng CO2do 01 ngi thai ra phuthuc vao cng lao ng, nn Vkcung phuthuc
vao cng lao ng.
Bang 2.7 : Lng khng kh ti cn cp
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VK, m3/h.ngiCng vn ng VCO2,
m3/h.ngi =0,1 =0,15- Ngh ngi 0,013 18,6 10,8- Rt nhe 0,022 31,4 18,3- Nhe 0,030 43,0 25,0- Trung bnh 0,046 65,7 38,3
- Nng 0,074 106,0 61,7
Bang 2.8 a ra nng cho phep cua mt scht c hai khac. Cn c vao nng chophep nay vaphng trnh (2-1) cothxac nh c lng khng kh ti cn cung cp giam nng n mc yu cu.
Bang 2.8 : Nng cho phep cua mt scht
TT Tn cht Nng chophep
mg/m3
TT Tn cht Nng chophep
mg/m3123456789
101112131415161718
AcroleinAmoniacAncolmetylicAnilinAxetonAxit aceticAxit nitricAxit sunfuricBezen
Cacbon monooxitCacbon dioxitCloClodioxitClobenzenDu hoaDu thngioxit sunfuaiclobezen
22
505
200552
50
301%o0,11
503003002020
192021222324252627
2829303132333435
icloetanivininEte etylicEtylen oxitHidrosunfuaIotKem oxitMagie oxitMetylenclorua
NaphtalenNicotinNit oxitznPhnnBui thuc la, cheBui coSiO2Bui xi mng, t
10100300
1100
15
1550
200,55
0,15316
Trong trng hp trong khng gian iu hoa co hut thuc la, lng khng kh ti cncung cp oi hoi nhiu hn, loai tranh hng cua khoi thuc.
Bang 2.9 : Lng kh ti cn cung cp khi cohut thuc
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Mc hut thuc,iu/h.ngi
Lng khng kh ticn cung cp, m3/h.ngi
0,8 1,01,2 1,62,5 33 5,1
13 1720 2642 5151 85
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CHNG 3CN BNG NHIT VACN BNG M
3.1 PHNG TRNH CN BNG NHITXet mt hnhit ng bt ky, hlun lun chu tac ng cua cac ngun nhit bn ngoai
vabn trong. Cac tac ng ongi ta goi lacac nhiu loan vnhit . Thc tcac hnhitng chu tac ng cua cac nhiu loan sau :
- Nhit toa ra tcac ngun nhit bn trong hgoi lacac ngun nhit toa: Qtoa- Nhit truyn qua kt cu bao che goi langun nhit thm thu : QttTng hai thanh phn trn goi lanhit tha
QT= Qtoa+ Qtt (3-1)
duy tr chnhit m trong khng gian iu hoa, trong kythut iu hoakhng khngui ta phai cp tun hoan cho h mt lng khng kh colu lng L (kg/s) trang thaiV(tV, V) nao ova ly ra cung lng nh vy nhng trang thai T(tT,T). Nh vy lngkhng kh nay a ly i t phong mt lng nhit bng QT. Ta cophng trnh cn bngnhit nh sau :
QT= Lq.(IT- IV) (3-2)* Phng trnh cn bng m
Tng tnh trong hlun lun cocac nhiu loan vm sau- m toa ra tcac ngun bn trong h: Wtoa- m thm thu qua kt cu bao che : WttTng hai thanh phn trn goi lam tha
WT= Wtoa+ Wtt (3-3)hcn bng m vacotrang thai khng kh trong phong khng i T(tT, T) ngui ta
phai lun lun cung cp cho h mt lng khng kh colu lng L (kg/s) trang thai V(tV
,V). Nh vy lng khng kh nay aly i tphong mt lng m bng WT. Ta cophngtrnh cn bng m nh sau :
WT= LW.(dT- dV) (3-4)* Phng trnh cn bng nng cht c hai (nu co)kh cac cht c hai phat sinh ra trong phong ngi ta thi vao phong lu lng gio
Lz(kg/s) sao cho :G= Lz.(zT- zV) , kg/s (3-5)
G: Lu lng cht c hai toa ra vathm thu qua kt cu bao che, kg/sZT va Zv : Nng theo khi lng cua cht c hai cua khng kh cho phep trong
phong vathi vaoNhit tha, m tha valng cht c toara lac sxac nh nng sut cua cac thitb xlykhng kh . Trong phn di y chung ta xac nh hai thng squan trong nht latng nhit tha QTvam tha WT.
3.2 XAC NH LNG NHIT THA QT3.2.1 Nhit do may moc thit b in toa ra Q1
3.2.1.1 Nhit toara t thit b dn ng bng ng c in
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May moc sdung in gm 2 cum chi tit lang c in vac cu dn ng. Tn thtcua cac may bao gm tn tht ng c vatn tht c cu dn ng. Theo v tr tng icua 2 cum chi tit nay ta co3 trng hp coth xay ra :
- Trng hp 1 :ng c vachi tit dn ng nm hoan toan trong khng gian iu hoa- Trng hp 2 : ng c nm bn ngoai, chi tit dn ng nm bn trong- Trng hp 3: ng c nm bn trong, chi tit dn ng nm bn ngoai.
Nhit do may moc toara ch di dang nhit hin.Goi N valacng sut vahiu sut cua ng c in. Cng sut cua ng c in N thnglacng sut tnh u ra cua ng c. V vy :
- Trng hp 1: Toan bnng lng cung cp cho ng c u c bin thanh nhitnng vatrao i cho khng kh trong phong. Nhng do cng sut N c tnh lacng sutu ra nn nng lng mang c tiu thula
- Hiu sut cua ng c- Trng hp 2 : V ng c nm bn ngoai, cum chi tit chuyn ng nm bn trong nn
nhit tha phat ra tshoat ng cua ng c chnh lacng sut N.q1= N (3-7)
- Trng hp 3 : Trong trng nay phn nhit nng do ng c toa ra bng nng lngu vao trcho phn toara tc cu c chuyn ng:
tin li cho vic tra cu tnh toan, tn tht nhit cho cac ng c cothtra cu cuthcho tng trng hp trong bang 3-1 di y:
Bang 3.1 : Tn tht nhit cua cac ng c in
Tn tht nhit q1, kWCngsut mt ura, kW
Hiu sut( % )
M t vac cutruyn ng t
trong phong
M t ngoaic cu truyn
ng trong phong
M t trong, ccu truyn ng
ngoai(1) (2) (3) (4) (5)
0,040,060,090,120,18
4149556064
0,100,120,160,200,30
0,040,060,090,120,18
0,060,060,070,080,11
0,250,370,550,751,1
6770727379
0,370,530,761,031,39
0,250,370,550,751,1
0,120,160,210,280,29
1,52,24,0
808283
1,883,664,82
1,52,24,0
0,380,660,82
Nq =1
)1.(1
=N
q
3-6
3-8
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(1) (2) (3) (4) (5)5,57,5
8485
6,558,82
5,57,5
1,051,32
1115
8687
12,817,2
1115
1,82,2
18,5
2230
88
8889
21,0
25,033,7
18,5
2230
2,5
3,03,73745557590
8990909090
41,650,061,183,3100
3745557590
4,65,06,18,3
10,0110132150
185220250
919191
919292
121145165
203239272
110132150
185220250
111315
181922
Cn lu ylanng lng do ng c tiu thuang cp lachnh mc. Tuy nhintrn thc tng c cothhoat ng non tai hoc quatai. V thchnh xac hn cn tinhanh o cng dong in thc txac nh cng sut thc.
3.2.1.2. Nhit toara t thit b inNgoai cac thit b c dn ng bng cac ng c in, trong phong cothtrang b cac
dung cusdung in khac nh : Ti vi, may tnh, may in, may sy toc ...vv. ai a scacthit b in ch phat nhit hin.
i vi cac thit b in phat ra nhit hin th nhit lng toara bng chnh cng sut ghitrn thit b.
Khi tnh toan tn tht nhit do may moc vathit b in phat ra cn lu ykhng phai ttcacac may moc vathit b in cung u hoat ng ng thi. cho cng sut may lanhkhng qualn, cn phai tnh n mc hoat ng ng thi cua cac ng c. Trong trnghp tng quat:
Q1= q1.Ktt.kt (3-9)Ktt- hstnh toan bng tysgia cng sut lam vic thc vi cng sut nh mc.Kt- Hsng thi, tnh n mc hoat ng ng thi. Hsng thi cua mi ng ccothcoi bng hsthi gian lam vic , tc labng tysthi gian lam vic cua ng c thi, chia cho tng thi gian lam vic cua toan bhthng.
3.2.2 Nhit toa ra tcac ngun sang nhn tao Q2Ngun sang nhn tao y cp langun sang tcac en in. Co thchia en in ra
lam 2 loai : en dy toc vaen huynh quang.
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Nhit do cac ngun sang nhn tao toara ch dang nhit hin.- i vi loai en dy toc: Cac loai en nay cokhanng bin i ch 10% nng lng
u vao thanh quang nng, 80% c phat ra bng bc xanhit, 10% trao i vi mi trngbn ngoai qua i lu vadn nhit . Nh vy toan bnng lng u vao dubin i vaphatra di dang quang nng hay nhit nng nhng cui cung u bin thanh nhit va ckhng kh trong phong hp thuht.
Q21= NS, kW (3-10)NS- Tng cng sut cac en dy toc, kW- i vi en huynh quang: Khoang 25% nng lng u vao bin thanh quang nng,
25% c phat ra di dang bc xanhit, 50% di dang i lu vadn nhit. Tuy nhin ivi en huynh quang phai trang b thm bchnh lu , cng sut bchn lu c25% cngsut en. V vy tn tht nhit trong trng hp nay :
Q22= 1,25.Nhq, kW (3-11)Nhq: Tng cng sut en huynh quang, kW
Q2= Q21+ Q22, kW (3-12)Mt vn thng gp trn thc tlakhi thit kkhng bit btr en cuthtrong phong
senh thnao hoc ngi thit kkhng coiu kin khao sat chi tit toan bcng trnh,hoc khng cokinh nghim vcach btr en cua cac i tng. Trong trng hp nay cothchon theo iu kin uchiu sang cho bang 3-2.
Bang 3.2 : Thng skinh nghim cho phong
Khu vc Lu lng khng khL/s.m2
Phn bngim2/ngi
Cng sut chiusang, W/m2
- Nha- Motel- Hotel
+ Phong ngu+ Hanh lang
5,97,5
5,910,6
1010
203
1212
1224
- Trin lam nghthut- Bao tang- Ngn hang
10 5 12
- Th vin- Nhahat
+ Phong Audio+ Quan bar+ Khu vc trgiup
- Nhahang- Rap chiu bong- Siu th- Ca hang nho
+ Hiu un toc+ Ban day, mu
- Phong ththao nhe- Phong hi ngh
11
12,112,96,4
17,312,18,3
12,09,8
13,412,2
3
0,80,84
1,50,84
4313
12
101018121036
24241224
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Nh vy tn tht do ngun sang nhn tao , trong trng hp nay c tnh theo cng thcQ2= qs.F, W (3-13)
trong oF - din tch san nha, m2qs- Cng sut chiu sang yu cu cho 1m2din tch san, W/m2
3.2.3 Nhit do ngi toa ra Q3
Nhit do ngi toa ra gm 2 thanh phn :- Nhit hin : Do truyn nhit tngi ra mi trng thng qua i lu, bc xavadnnhit : qh
- Nhit n :Do toa m (mhi vahi nc mang theo) : qW-Nhit toan phn: Nhit toan phn bng tng nhit hin vanhit n :
q = qh+ qW (3-14)i vi mt ngi ln trng thanh vakhoemanh, nhit hin, nhit n vanhit toan phn
phuthuc vao cng vn ng vanhit mi trng khng kh xung quanh.Tn tht do ngi toa c xac nh theo cng thc :
- Nhit hin :
Q3h= n.qh..10-3, kW
- Nhit n:Q3w= n.qw..10-3, kW
- Nhit toan phn:Q3= n.q.10-3, kW (3-15)
n - Tng sngi trong phongqh, qw, q - Nhit n, nhit hin vanhit toan phn do mt ngi toa ra trong mt n v
thi gian vac xac nh theo bang 3.4.
Khi tnh nhit tha do ngi toara ngi thit kthng gp khokhn khi xac nh s
lng ngi trong mt phong. Thc t, slng ngi lun lun thay i vahu nh khngtheo mt quy lut nht nh nao ca. Trong trng hp o co th ly theo s liu phn bngi nu trong bang 3-2.
Bang 3.4 di y lanhit toan phn vanhit n do ngi toara. Theo bang nay nhit nvanhit hin do ngi toara phuthuc cng vn ng cua con ngi vanhit trongphong. Khi nhit phong tng th nhit n tng, nhit hin giam. Nhit toan phn ch phuthuc vao cng vn ng makhng phuthuc vao nhit cua phong.
Ct 4 trong bang la lng nhit tha phat ra tc thmt ngi an ng trung nin cokhi lng c thchng 68kg. Tuy nhin trn thc ttrong khng gian iu hoathng comt nhiu ngi vi gii tnh vatui tac khac nhau. Ct 4 lagiatr nhit tha trung bnh trn
c s lu y ti t lan ng vaan bathng co nhng khng gian khao sat nu trongbang. Nu mun tnh cuth theo thc tth tnh nhit do ngi abatoara chim 85% , treem chim 75% lng nhit tha cua ngi an ng.
Trong trng hp khng gian khao sat lanhahang th nn cng thm lng nhit tha dothc n toara cho mi ngi la20W , trong o10W lanhit hin va10W lanhit n
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* Hstac dung khng ng thiKhi tnh toan tn tht nhit cho cng trnh ln lun lun xay ra hin tng khng phai luc
nao trong tt cacac phong cung comt y uslng ngi theo thit kvatt cacac enu c bt sang. tranh vic chon may cocng sut quad , cn nhn cac tn tht Q2vaQ3vi hsgoi lahstac dung khng ng thi t. Vgiatr hstac dung khng ngthi anh giatylngi comt thng xuyn trong phong trn tng sngi cothcohoc
tylcng sut thc tcua cac en ang sdung trn tng cng sut en c trang b. Trnbang trnh bay giatr cua hstac ng khng ng thi cho mt strng hp.
Bang 3.3 : Hstac dung khng ng thi
HstKhu vcNgi en
- Cng s- Nhacao tng, khach san- Ca hang bach hoa
0,75 0,90,4 0,60,8 0,9
0,7 0,850,3 0,50,9 1,0
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Bang 3.4 : Nhit n vanhit hin do ngi toara,W/ngi
Nhit ph28 27 26
Mc hoat ng Loai khng gian Nhit thatan ngtrung nin
Nhit thatrung bnh
qh qW qh qW qh qWNgi yn tnhNgi, hoat ng nheHoat ng vn phongi, ng chm rai
Ngi, i chmi, ng chm rai
Cac hoat ng nheCac lao ng nheKhiu vui b1,5 m/sLao ng nng
NhahatTrng hocK.san, V.PhongCa hangSn bay, hiu thuc
Ngn hang
NhahangXng san xutVutrngXngXng san xut
115130140160160160
150230260300440
100120130130150150
160220250300430
505050505353
55556280
132
507080809797
105165188220298
555556565858
60627088
138
456574749292
100158180212292
606060606464
68707896
144
406070708686
92150172204286
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3.2.4 Nhit do san phm mang vao Q4Tn tht nhit dang nay ch cotrong cac x nghip, nhamay, o, trong khng gian iu
hoathng xuyn valin tuc coa vao vaa ra cac san phm conhit cao hn nhit trong phong.
Nhit toan phn do san phm mang vao phong c xac nh theo cng thcQ4= G4.Cp(t1- t2) + W4.r , kW (3-16)
trong o:- Nhit hin : Q4h= G4.Cp(t1- t2), kW- Nhit n : Q4w= W4.ro, kW
G4- Lu lng san phm vao ra, kg/sCp- Nhit dung ring khi lng cua san phm, kJ/kg.oCW4- Lng m toa ra (nu co) trong mt n v thi gian, kg/sro- Nhit n hoa hi cua nc ro= 2500 kJ/kg
3.2.5 Nhit toa ra tbmt thit b nhit Q5Nu trong khng gian iu hoa cothit b trao i nhit, chng han nh losi, thit b
sy, ng dn hi . . vv th cothm tn tht do toa nhit tbmt nong vao phong. Tuy nhintrn thc tt xay ra v khi iu hoa th cac thit b nay thng phai ngng hoat ng.Nhit toa ra tbmt trao i nhit thng c tnh theo cng thc truyn nhit vao
ch lanhit hin. Tuy thuc vao giatr o ac c mangi ta tnh theo cng thc truynnhit hay toanhit.
- Khi bit nhit bmt thit b nhit tw:Q5= W.FW.(tW-tT) (3-17)
Trong oWlahstoa nhit tbmt nong vao khng kh trong phong vac tnh theocng thc sau :
W= 2,5.t1/4 + 58..[(TW/100)4- (TT/100)4 ] / t (3-18)
Khi tnh gn ung cothcoi W= 10 W/m2.oCt = tW- tTtW, tT- lanhit vach vanhit khng kh trong phong.
- Khi bit nhit cht long chuyn ng bn trong ng dn tF:Q5= k.F.(tF-tT) (3-19)
trong ohstruyn nhit k = 2,5 W/m2.oC3.2.6 Nhit do bc xamt tri vao phong Q63.2.6.1 Nhit bc xamt tri
Cothcoi mt tri lamt quacu la khng lvi ng knh trung bnh 1,39.106km vacach xa quat 150.106km. Nhit bmt cua mt tri khoang 6000OK trong khi tm
at n 840.106 oKTuythuc vao thi im trong nm makhoang cach tmt tri n trai t thay i, mc
thay i x dch trong khoang +1,7% so vi khoang cach trung bnh noi trn.Do anh hng cua bu kh quyn lng bc xamt tri giam i khanhiu. Conhiu yu
tanh hng ti bc xamt tri nh mc nhim bui, my mu, thi im trong ngay vatrong nm , a im ni lp t cng trnh, cao cua cng trnh so vi mt nc bin, nhitong sng cua khng kh xung quanh vahng cua bmt nhn bc xa.
Nhit bc xa c chia ra lam 3 thanh phn
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- Thanh phn trc xa- nhn nhit trc tip tmt tri- Thanh phn tan xa- Nhit bc xachiu ln cac i tng xung quanh lam nong chung
vacac vt obc xagian tip ln kt cu- Thanh phn phan chiu tmt t.
3.2.6.2 Xac nh nhit bc xamt tri .Nhit bc xaxm nhp vao phong phuthuc kt cu bao che vac chia ra lam 2 dang :
- Nhit bc xaqua ca knh Q61- Nhit bc xaqua kt cu bao che tng vamai : Q62Q6= Q61+ Q62 (3-20)
a. Nhit bc xaqua knh* Trng hp sdung knh c ban :Knh c ban laloai knh trong sut, day 3mm, cohshp thum=6%, hsphan xam
= 8% (ng vi goc ti cua tia bc xala30o)Nhit bc xamt tri qua knh c tnh theo cng thc :
Q61= Fk.R.c.ds.mmkh.K.m, W (3-21)trong o:
+ Fk - Din tch b mt knh, m2
. Nu khung g Fk = 0,85 F (F Din tch phn knh vakhung), khung st Fk= F+ R- Nhit bc xamt tri qua ca knh c ban vao phong . Giatr R cho bang 3-7+ c- Hstnh n cao H (m) ni t ca knh so vi mc nc bin:
+ ds- Hsxet ti anh hng cua chnh lch nhit ong sng so vi 20oC+ mm - H s xet ti anh hng cua my mu . Tri khng my ly mm = 1, tri comy
mm=0,85+ kh- H sxet ti anh hng cua khung knh. Kt cu khung khac nhau th mc chekhut mt phn knh di cac tia bc xakhac nhau. Vi khung gkh= 1, khung kim loai kh= 1,17+ K- Hs knh, phuthuc mau sc valoai knh khac knh c ban valy theo bang 3-5
Bang 3-5 : c tnh bc xacua cac loai knhLoai knh Hs
hp thuk
Hsphan xa
k
Hsxuynqua k
Hsknh K
Knh c ban
Knh trong day 6mm, phngKnh spectrafloat, mau ng nu, day 6mmKnh chng nng, mau xam, 6mmKnh chng nng, mau ng nu, 12mmKnh Calorex, mau xanh , 6mmKnh Stopray, mau vang, 6mmKnh trong trang mang phan xaRS20, 6mmKnh trong trang mang phan xaA18, 4mm
0,06
0,150,340,510,740,750,360,440,30
0,08
0,080,100,050,050,050,390,440,53
0,86
0,770,560,440,210,200,250,120,17
1,00
0,940,800,730,580,570,440,340,33
1000023,01 H
c +=
10
20.13,01
= sds
t
3 -22
3-23
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+ m - Hsmt tri . H snay xet ti anh hng cua man che ti bc xamt tri. Khikhng coman che m= 1. Khi coman mc chon theo bang 3-6
Bang 3-6 : c tnh bc xacua man che
Loai man che, rem che Hshpthum
Hsphanxam
Hsxuyn qua
m
Hsmttri m
- Ca chp mau nhatmau trung bnhmau m
- Man che loai metalon- Man che Brella kiu HaLan
0,370,580,720,290,09
0,510,390,270,480,77
0,120,030,010,230,14
0,560,650,750,580,33
Bang 3-7: Dong nhit bc xamt tri xm nhp vao phong R, W/m2
V 10OBc Gimt tri
Thang Hng 6 7 8 9 10 11 12 13 14 15 16 17Bcng Bc
ng
60173170
139413423
158483489
142442438
139334309
136205129
1298844
1364444
1394444
1424141
1583535
1392525
ng NamNam
Ty Nam
5766
1552525
1733525
1464141
794444
444444
444444
444444
444479
4141136
3535173
2525155
6
TyTy Bc
Mt nm ngang
6613
2525
139
2525
337
4141524
4444647
4457
735
4488766
129205735
309334647
438442524
489483337
423413139
Bcng Bc
ng
16132158
107401426
123467498
110419448
104344309
98177136
956944
984444
1044444
1104141
1233535
1072222
ng NamNam
Ty Nam
8233
1802222
2083535
1774141
1014444
444444
444444
444444
4444101
4141177
3535208
2222180
5 va7
TyTy Bc
Mt nm ngang
339
2222
132
3535
337
4141524
4444662
4444
744
4469779
136177744
309344662
448419524
498467337
426401132
Bcng Bc
ng
354
79
47356
435
50410
514
47350
470
47252
328
44107
145
4444
44
4444
44
4744
44
4741
41
5035
35
4722
22ng NamNam
Ty Nam
5733
2492222
2963535
2684141
1894444
854444
444444
444485
4444189
4141268
3535296
2222249
4 va8
TyTy Bc
Mt nm ngang
336
2222
120
3535
331
4141527
4444672
4444
763
4444789
145107763
252237672
470350527
514410331
435356120
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31
Bcng Bc
ng
333
19281410
35325517
41252476
44142334
4454
148
444444
444444
444444
414141
353535
191919
ng NamNam
Ty Nam
333
3061919
4014135
3856041
2967644
1778544
668866
4485177
4476196
4160385
3541401
1919306
3 va9
Ty
Ty BcMt nm ngang
3
33
19
1998
35
35306
41
41505
44
44653
44
44741
44
44779
148
54741
334
142653
476
252505
517
325306
410
28198
Bcng Bc
ng
000
16183372
32208489
41139457
4488315
4444
126
444444
444444
444444
414141
323232
161616
ng NamNam
Ty Nam
000
3255716
46412632
47017341
38820544
25522457
145230145
57224255
44205388
41173470
32126464
1657325
2 va10
TyTy Bc
Mt nm ngang
00
0
1616
69
3232
268
4141
438
4444
609
4444
694
4444
735
12644
694
31588
609
457139
438
489208
268
372183
69Bcng Bc
ng
000
1385
312
28117451
3854416
4141293
4444
123
444444
444444
414141
383838
282828
131313
ng NamNam
Ty Nam
000
31211013
48320528
50828738
46030354
34432898
221334221
98328344
54303460
38287508
28205483
13110312
1 va11
TyTy Bc
Mt nm ngang
000
131354
2828
196
3838413
4141552
4444
637
4444662
12344637
29341552
41654413
451117196
3128554
Bc
ng Bcng
0
00
13
47271
28
88432
38
54410
41
41287
44
44132
44
4444
44
4444
41
4141
38
3838
28
2828
13
1313
ng NamNam
Ty Nam
000
31215813
48623328
51429638
47034473
382366144
249378249
114366382
73344470
38296514
28233486
13158312
12
TyTy Bc
Mt nm ngang
000
131344
2828
208
3838378
4141527
4444
609
4444637
13244609
28741527
41054378
43288208
2714744
V 20OBc Gimt triThang Hng 6 7 8 9 10 11 12 13 14 15 16 17
Bcng Bc
ng
88255255
129454467
104385505
79262451
60120303
5447
129
474444
544444
604444
793844
1042838
129928
6ng Nam
NamTy Nam
8899
1962828
2303838
2084444
1394444
664444
444444
444466
4444139
4444208
3838230
2828196
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6
TyTy Bc
Mt nm ngang
9935
2828
189
3838
382
4444555
4444681
4444
732
4447789
129120732
302262681
451385555
505454382
467486189
Bcng Bc
ng
63224237
88416467
73435514
54350457
47230312
4498
145
444444
444444
474444
544141
733838
882525
ng Nam
NamTy Nam
98
99
221
2525
268
3838
249
4444
180
4444
91
4444
44
4444
44
4491
44
44180
41
41249
38
38268
25
25221
5 va7
TyTy Bc
Mt nm ngang
9925
2525
173
3838
372
4141552
4444681
4444
757
4444792
14598757
312230681
457350552
514435372
467416173
Bcng Bc
ng
19142167
32350448
35372520
41281470
44158334
4457
161
444444
444444
444444
414141
353535
322222
ng NamNam
Ty Nam
916
6
28122
22
35635
35
34144
41
30963
44
17376
44
6382
63
4476
173
4463
309
4144
341
3535
356
2222
281
4 va8
TyTy Bc
Mt nm ngang
6616
2222
151
3535
337
4141527
44445662
4444
741
4444779
16157741
334158662
470281527
520372337
148350151
Bcng Bc
ng
000
19262410
35274514
41186470
4469328
4444
142
444444
444444
444444
414141
353535
191919
ng NamNam
Ty Nam
000
3122519
4296935
44212041
37816444
26519947
129205129
47199265
44164378
44120442
3569429
1925312
3 va9
Ty
Ty BcMt nm ngang
0
00
19
1995
35
35293
41
41483
44
44624
44
44710
44
44735
142
44710
328
69624
470
186483
514
247293
410
26295
Bcng Bc
ng
000
13139
28164464
3891445
4141315
4444
155
444444
444444
414141
383838
282828
131313
ng NamNam
Ty Nam
000
2876613
46015828
50524038
47029341
37533585
233350233
85334375
41293470
38240505
28158460
1366287
2 va10
TyTy Bc
Mt nm ngang
000
131357
2828
214
3838401
4141539
4444
618
4444656
15544618
31541539
44591401
464164214
31213957
Bcng Bc
ng
000
976
224
2582
404
3544401
4141287
4141
136
414141
414141
414141
353535
252525
9991 va11
ng NamNam
Ty Nam
000
230889
45021825
51731535
49838850
426429145
287445287
145429426
50388498
35315517
25218454
988230
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1 va11
TyTy Bc
Mt nm ngang
000
9916
2525
151
3535319
3838460
4141
542
4141568
13641542
28741460
40141319
40482151
2247616
Bcng Bc
ng
000
644
177
2257
372
3538382
3838268
4141107
414141
414141
383838
353535
222222
666
ng Nam
NamTy Nam
0
00
186
796
438
23322
527
35035
501
41663
423
460198
306
470306
189
460423
63
416501
35
350527
22
233438
6
79186
12
TyTy Bc
Mt nm ngang
000
6613
2222
114
3535290
3838246
4141
508
4141536
10741508
26838426
38238290
37257114
1774413
V 30OBc Gimt triThang Hng 6 7 8 9 10 11 12 13 14 15 16 17
Bc
ng Bcng
104
331341
91
410492
57
306508
44
173451
44
60309
44
44139
44
4444
44
4444
44
4444
44
3844
57
3238
91
1632ng Nam
NamTy Nam
1321616
2373232
2843828
2844444
2304744
1396044
546654
4460139
4447230
4444284
3838284
3232237
6
TyTy Bc
Mt nm ngang
161660
3232
192
3838
413
4444568
4444684
4444
757
4444789
13960757
309173684
451306568
508410413
492438192
Bcng Bc
ng
69293315
63413489
44388517
44281457
44145312
4450
139
444444
444444
444444
444141
443838
632828
ng NamNam
Ty Nam
1321313
2592828
3153838
3154441
2626344
1678544
699544
4485167
4463262
4144315
3838315
2828258
5 va7
TyTy Bc
Mt nm ngang
131347
2828
208
3838
388
4141555
4444675
4444
744
4444776
13950744
312145675
457281555
517388388
489413208
Bcng Bc
ng
19173208
25341464
35315520
41208467
4185322
4444
145
444444
444444
414141
4141413
353535
252525
ng Nam
NamTy Nam
117
66
309
2525
401
4135
407
8541
353
14841
259
18347
123
198123
47
183259
41
148353
41
85407
35
41401
25
25309
4 va8Ty
Ty BcMt nm ngang
6619
2525
148
3535
337
4141508
4141631
4444
710
4444741
14544710
32285631
467208508
520315337
464341148
3 va9
Bcng Bc
ng
000
16233391
32284498
38126454
4147325
4444
151
444444
444444
414141
383838
323232
161616
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34
ng NamNam
Ty Nam
000
3092816
4135732
47918938
44525941
35630979
211331211
79309356
41259445
38189479
3257413
1628309
3 va9Ty
Ty BcMt nm ngang
000
161679
3232
255
3838426
4141565
4444
637
4444669
15144637
32547565
454126426
498284255
39123379
Bc
ng Bcng
0
00
9
140249
25
123426
35
57416
38
38296
41
41136
44
4444
41
4141
38
3838
35
3535
25
2525
9
99
ng NamNam
Ty Nam
000
230579
44818025
51429035
50138247
429438148
290457290
148438429
47382501
35290514
25180448
957230
2 va10
TyTy Bc
Mt nm ngang
000
9919
2525
155
3535315
3838451
4141
539
4444565
13641538
29638451
41657315
426123155
29410419
Bcng Bc
ng
00
0
325
85
1950
344
2828
366
3535
262
3838
110
3838
38
3838
38
3535
35
2828
28
1919
19
33
3ng NamNam
Ty Nam
000
88323
40121419
50834428
51143273
451486202
328501328
202486451
73432511
28344508
19214401
33288
1 va11
TyTy Bc
Mt nm ngang
000
336
191985
2828224
3535344
3838
429
3838457
11038429
26235344
36628224
3445085
85256
Bcng Bc
ng
000
000
1332
290
2828331
3535252
3838101
383838
383838
353535
282828
131313
000
ng Nam
NamTy Nam
0
00
0
00
360
20213
495
35628
511
44888
451
501227
341
514341
227
501451
88
448511
28
356495
13
202360
0
00
12
TyTy Bc
Mt nm ngang
000
000
131360
2828189
3535306
3838
385
3838413
10138385
25235306
33128189
2903260
000
Cng thc (3-21) trn y ch tnh cho cac trng hp sau :- Knh laknh c ban (K= 1) cohoc khng corem che- Khng phai knh c ban (k1) va khng corem che (m= 1).
Trng hp knh khng phai knh c ban (K1) vacorem che (m1) ngi ta tnh theo
cng thc di y.* Trng hp khng phai knh c ban vacorem che :Q61= Fk.Rxn.c.ds.mmkh.K , W (3-24)
trong oFk- Din tch ca knh , m2Rxn- Lng nhit bc xaxm nhp vao khng gian iu hoa
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Tr sR ly theo bang 3-7, cac giatr K, K, Kly theo bang (3-5), m, m, mly theobang (3-6). Cac hskhac vn tnh ging nh cac hscng thc (3-21)
* Bc xamt tri qua knh thc t
Nhit bc xamt tri khi bc xaqua knh ch comt phn tac ng tc thi ti khng khtrong phong, phn con lai tac ng ln kt cu bao che vab hp thumt phn, ch sau mtkhoang thi gian nht nh mi tac ng ti khng kh
V vy thanh phn nhit tha do cac tia bc xaxm nhp qua ca knh gy tac ng tcthi n phutai hthng iu hoakhng kh
Rxn= Rmax.k.nt (3-26)trong o
Rxn- Lng bc xamt tri xm nhp qua ca knh gy tac ng tc thi n phutai cuahthng iu hoakhng kh, W/m2
Rmax- Lng bc xamt tri ln nht xm nhp qua ca knh, W/m2(Tham khao bang 3-8a)
nt- Hstac dung tc thi (Tham khao bang 3-8b, va3-8c)k - Tch scac hsxet ti anh hng cua cac yu tnh sng mu, cao, nhit ng
ng sng, loai khung ca vaman che.Hstac ng tc thi cho trong cac bang 3-8b va3-8c. Cn lu yrng xac nh hs
tac dung tc thi phai cn cvao khi lng tnh cho 1m2din tch. Tht vy khi khi lngring cua vt cang ln, khanng hp thucac tia bc xacang ln, do omc chm trgiaim cc ai cua nhit bc xavaphutai lanh cang ln.
Bang 3-8a : Lng nhit ln nht xm nhp qua ca knh loai c ban Rmax, W/m
2
HngV (Bc)
ThangBc ng
Bcng ng
NamNam Ty
NamTy Ty
BcMt
Ngang
0
67 va58 va49 va3
10 va2
11 va112
141793232
3232
492483445372249
164132
464479514527514
479464
132164294372445
483492
44444444
107
211259
132164294372445
483492
464479514527514
479464
492483445372249
164132
713735773789773
735713
10
67 va58 va49 va3
10 va211 va1
1269541323228
483467410325208117
489498514517489451
173208296401470508
44444488
230334
173208296401470508
489498514517489451
483467410325208117
766779789779725662
RR mkmkmmkkxn .88,0
)]..4,0..(.4,0[ ++++= (3-25)
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12 28 88 432 514 378 514 432 88 637
20
67 va58 va49 va3
10 va2
11 va112
8260353228
2525
486435372274164
8257
505514520514464
404382
230268356442505
517527
444482
205350
445470
230268356442505
517527
505514520514464
404382
486435372274164
8257
789792779735656
568536
30
67 va58 va49 va3
10 va211 va1
12
63503528252219
4384133412841235038
508517520498426366331
284315407479514511511
6695
199331457501514
284315407479514511511
508517520498426366331
4384133412841235038
789776741669565457413
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V du1: Xac nh lng nhit bc xaln nht vao qua ca sbng knh c ban, rng 5m2.Cho bit a phng ni lp t cng trnh v 20o Bc, knh quay v hng ng,khung ca bng st, nhit ong sng trung bnh la25oC, tri khng sng mu, cao sovi mt nc bin la100m.
-ng vi 20oBc , hng ng , theo bang 3-8 , tra c Rmax= 520 W/m2vao 8 githang 4 vathang 8
- Hsc= 1 + 0,023x100/1000 = 1,0023- Hsds= 1 - 0,13 (25-20)/10 = 1,065- Tri khng my nn mm= 1- Khung ca knh lakhung st nn kh= 1,17- Knh laknh c ban vakhng corem che nn k= m=1Theo cng thc (3-21) ta co:
Q = 5 x 520 x 1,0023 x 1,065 x 1,17 = 3247 W
V du2 : Xac nh lng nhit bc xa xm nhp khng gian iu hoaqua 10m2knhchng nng mau xam day 6mm, t hng Ty Nam, TP. HCh Minh, bn trong coman
che kiu HaLan. V tr lp t cocao so vi mt nc bin khng ang k, nhit ngsng trung bnh 24oC, tri khng my, khung ca bng g.- Lng nhit bc xaqua knh c xac nh theo cng thc :
Q = F.Rxn.c.ds.mmkh- Cac hsc= mm= kh= 1- Hs ds = 1+ 0,13.(24 - 20)/10 = 1,052- Lng nhit xm nhp :
Rxn= [0,4k+ k.(m+m+k.m+0,4k.m)].R / 0,88= [ 0,4 x 0,51 + 0,44.(0,09 + 0,14 + 0,05x0,77+0,4x0,51x0.09] R/0,88 = 0,375.R
- Gia tr R tra theo bang 3-7 vi 10ov Bc, hng Ty Nam : Rmax= 508 W/m2vao luc
15 githang 1 va11.Q = 10 x 0,375 x 508 x 1,052 = 2004 W
b. Nhit lng bc xamt tri qua kt cu bao che Q62.Khac vi ca knh c chbc xamt tri qua kt cu bao che c thc hin nh sau- Di tac dung cua cac tia bc xamt tri, bmt bn ngoai cung cua kt cu bao che se
dn dn nong ln do hp thunhit. Lng nhit nay setoara mi trng mt phn, phn conlai sedn nhit vao bn trong va truyn cho khng kh trong phong bng i lu vabc xa.Quatrnh truyn nay secochm trnht nh. Mc chm trphuthuc ban cht ktcu tng, mc day mong.
Thng thng ngi ta boqua lng nhit bc xaqua tng. Lng nhit truyn qua maido bc xavachnh nhit trong phong vangoai tri c xac nh theo cng thc:
Q62= F.k.m.t, W (3-26)F - Din tch mai (hoc tng), m2k - Hstruyn nhit qua mai (hoc tng), W/m2.oCt = tTD- tT chnh nhit tng ng
tTD= s.Rxn/ N (3-27)s- Hshp thucua mai vatng
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N= 20 W/m2.K - Hstoanhit i lu cua khng kh bn ngoaiRnx= R/0,88 - Nhit bc xap vao mai hoc tng, W/m2R - Nhit bc xaqua knh vao phong (tra theo bang 3-7), W/m2m- Hsmau cua mai hay tng
+ Mau thm : m= 1+ Mau trung bnh : m= 0,87
+ Mau sang : m= 0,78
s- Hshp thucua tng vamai phuthuc mau sc, tnh cht vt liu, trang thai bmt tra theo bang di y
Bang 3.9 : en bmt kt cu bao che
STT Vt liu vamu sc HsA Mt mai
1 Fibr xi mng, mi, mau trng 0,422 Fibr xi mng , sau 6 thang sdung 0,61
3 Fibr xi mng , sau 12 nm sdung 0,714 Fibr xi mng mau trng, quet nc xi mng 0,595 Fibr xi mng mau trng sau 6 nm sdung 0,836 Tm ep gn song bng bng khoang 0,617 Giy du lp nhath 0,918 Giy du lp nhath, rc hat khoang phumt 0,849 Giy du lp nhath, rc cat mau xam 0,88
10 Giy du lp nhath, rc cat mau xm 0,9011 Tn mau sang 0,812 Tn mau en 0,8613 Ngoi mau ohay nu 0,6514 Ngoi mau oti 0,615 Ngoi xi mng mau xam 0,6516 Thep anh bong hay mau trng 0,4517 Thep anh bong hay mamau xanh 0,7618 Tn trang kem mi 0,6419 Tn trang kem b bui bn 0,9020 Nhm khng anh bong 0,5221 Nhm anh bong 0,26
B Mt quet sn22 Sn mau osang 0,5223 Sn mau xanh da tri 0,6424 Sn mau tm 0,8325 Sn mau vang 0,4426 Sn mau o 0,63
C Mt tng27 agranit mai nhn, mau o, xam nhat 0,55
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28 agranit mai nhn anh bong, mau xam 0,6029 acm tach mai nhn mau trng 0,3030 Gach trang men mau trng 0,2631 Gach trang men mau nu sang 0,5532 Gach nung mu omi 0,70 0,7433 Gach nung, cobui bn 0,77
34 Gach gm p mt mu sang 0,4535 B tng nhn phng 0,54 - 0,6536 Trat va mau vang, trng 0,4237 Trat va mau xi mng nhat 0,47
3.2.7 Nhit do lot khng kh vao phong Q7Khi cochnh ap sut trong nhavabn ngoai th secohin tng ror khng kh . Vic
nay lun lun kem theo tn tht nhit.Noi chung vic tnh tn tht nhit do ror thng rt phc tap do khoxac nh chnh xac
lu lng khng kh ror. Mt khac cac phong coiu hoa thng oi hoi phai kn. Phn
khng kh ror coth coi la mt phn kh ti cung cp cho hthng.Q7= L7.(IN- IT) = L7.Cp(tN-tT) + L7.ro(dN-dT) (3-28)
L7- Lu lng khng kh ror, kg/sIN, IT- Entanpi cua khng kh bn ngoai vabn trong phong, kJ/kgtT, tN- Nhit cua khng kh tnh toan trong nhavangoai tri, oCdT, dN- Dung m cua khng kh tnh toan trong nhavangoai tri, g/kg.kk
Tuy nhin, lu lng khng kh ror L rr thng khng theo quy lut vart khoxac nh.Nophuthuc vao chnh lch ap sut, vn tc gio, kt cu khe hcuth, sln ong mca ...vv. V vy trong cac trng hp nay cothxac nh theo kinh nghim
Q7h= 0,335.(tN- tT).V., W (3-29)Q7w= 0,84.(dN- dT).V., W (3-30)
V - Thtch phong, m3- Hskinh nghim cho theo bang 3.10 di y
Bang 3.10 : Hskinh nghim
ThtchV, m3
< 500 500 1000 1500 2000 2500 > 3000
0,7 0,6 0,55 0,5 0,42 0,4 0,35
Tng lng nhit do ror khng kh: Q7= Q7h+ Q7w (3-31)Trong trng hp cac ca ra vao s lt ngi qua lai tng i nhiu , cn b sung
thm lng khng kh .Gc= Lc.n. (3-32)
Gc- Lng khng kh lot qua ca, kg/giLc- Lng khng kh lot qua ca khi 01 ngi i qua, m3/ngin - Slt ngi qua lai ca trong 1 gi.- Khi lng ring cua khng kh, kg/m3
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Nh vy trong trng hp nay cn bsung thmQ7h= 0,335.(tN- tT).Lc.n , W (3-33)Q7w= 0,84.(dN- dT). Lc.n , W (3-34)
Bang 3-11 di y dn ra lng kh kh lot qua ca khi 01 ngi i qua.
Bang 3-11 : Lng khng kh lot qua cua Lc, m3/ngi
Lu lng Lc, m3/ngin, Ngi/giCa thng Ca xoay
< 100100 700
700 14001400 2100
333
2,75
0,80,70,50,3
3.2.8 Nhit truyn qua kt cu bao che Q8Ngi ta chia ra lam 2 tn tht
- Tn tht do truyn nhit qua trn mai, tng vasan (tng trn) : Q81- Tn tht do truyn nhit qua nn : Q82Tng tn tht truyn nhit
Q8= Q81+ Q82 (3-35)3.2.8.1 Nhit truyn qua tng, trn vasan tng trn Q81
Nhit lng truyn qua kt cu bao che c tnh theo cng thc sau y :Q81= k.F.t (3-36)
k -Hstruyn nhit cua kt cu bao che, W/m2.oCF - Din tch b mt kt cu bao chet - chnh nhit tnh toan, oC1. Xac nh chnh nhit tnh toan.
- Mua he:tH= .(tN- tT) (3-37)
- Mua ng :t= .(tT- tN) (3-38)
tT- Nhit tnh toan trong phong, oCtN- Nhit tnh toan bn ngoai, oC- Hstnh n v tr cua kt cu bao che i vi khng kh bn ngoai
a) i vi tng bao
i vi tng bao trc tip xuc vi mi trng khng kh bn ngoai th = 1. Trng hptng ngn nm bn trong cng trnh khng trc tip tip xuc vi khng kh bn ngoai trith hssec chon tuytrng hp cuthdi y.
b) i vi trn comai- Mai bng tn, ngoi, fibr xi mng vi kt cu khng kn = 0,9- Mai bng tn, ngoi, fibr xi mng vi kt cu kn = 0,8- Mai nhalp bng giy du = 0,75
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c) Tng ngn vi phong khng coiu hoa(phong m)- Nu phong m tip xuc vi khng kh bn ngoai = 0,7- Nu phong m khng tip xuc vi khng kh bn ngoai = 0,4
d) i vi san trn tng hm- Tng hm coca s = 0,6
- Tng hm khng coca s = 0,4
e) i vi tng ngn vi phong coiu hoaTrong trng hp nay ta khng tnh = 0
2. Xac nh hstruyn nhit qua tng vatrn.
T- Hstoanhit bmt bn trong cua kt cu bao che, W/m2, oCT- Hstoanhit bmt bn ngoai cua kt cu bao che, W/m2, oCi, - Chiu day cua lp thi , mi - Hsdn nhit lp thi, W/m.oC
a) Hstrao i nhit bn ngoai vabn trong phong
Bang 3.12 : Hstrao i nhit bn ngoai vabn trong
Dang vav tr bmt kt cu bao che T
W/m2.oC
N
W/m2.oC- Bmt tng, trn, san nhn 11,6- Bmt tng, trn, san cog, tyschiu caocua gvakhoang cach 2 mep g< 0,24
8,7
- Trn cogh/a = 0,23 0,3 8,1- Trn cogh/a > 0,3 7,6- Tng ngoai, san, mai tip xuc trc tipkhng kh bn ngoai.
23,3
- Bmt hng ra hm mai, hoc hng ra cacphong lanh , san trn tng hm
11,6
b) Nhit trcua lp khng khNu trong kt cu bao che co lp m khng kh th tng nhit trdn nhit phai cng
thm nhit tr cua lp khng kh nay. Thng lp m nay c lam trn trn chngnong.
NT
o
i
iRk
11
11
++
== (3-39)
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Bang 3.13 : Tr snhit trcua khng kh Rkk
Nhit trlp khng khRkk, m2.oC/W
Lp khng kh nm ngang, dongnhit i tdi ln
Lp khng kh nm ngang, dongnhit i t trn xung
Bdaylp khng kh
mm
Mua He Mua ng Mua He Mua ng10203050
100150
200 300
0,1290,1380,1380,1380,1460,1550,155
0,1460,1550,1630,1720,1810,1810,189
0,1290,1550,1630,1720,1810,1890,189
0,1550,1890,2060,2240,2320,2490,249
Ghi chu:
Tr sRkkcho bang trn y ng vi chnh nhit trn 2 bmt cua lp khng kh t= 10oC. Nu t 10oC ta cn nhn tr scho bang 3-14 di y
Bang 3.14: Hshiu chnh nhit trkhng kh
chnh nhit t, oC 10 8 6 4 2Hshiu chnh 1 1,05 1,1 1,15 1,2
c) Hsdn nhit cua vt liu xy dngHsdn nhit cua vt liu thay i phuthuc vao rng, m vanhit cua vt
liu.- rng cang ln th cang be, v cac lkh trong vt liu cohsdn nhit thp- m tng th hsdn nhit tng do nc chim chcac lkh trong vt liu, do hs
dn nhit cua nc cao hn nhiu so vi hsdn nhit cua khng kh.- Nhit tng, hsdn cua vt liu tng. Sthay i cua hsdn nhit khi nhit
thay i theo quy lut bc nht := o+ b.t kCal/m.h.oC (3-40)
trong o:
o- Hsdn nhit cua vt liu 0oC, kCal/m.h.oC
t - Nhit vt liu, oCb - H s ty l phu thuc vao tnh cht vt liu, co gia tr nm trong khoang 0,0001
0,001.Tuy nhin, do sphuthuc vao nhit cua vt liu khng ang knn trong cac tnh
toan thng coi hsdn nhit cua cac vt liu lakhng i valy theo bang di y.
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Bang 3.15 : Hsdn nhit cua cac vt liu
STT Vt liu Khi lngring, kg/m3
Hsdnnhit W/m.oC
123
456789
1011
12
131415
16
1718192021
22232425
26272829
3031
I- VT LIU AMING
Tm vaban ximng amingTm cach nhit ximng amingTm cach nhit ximng amingII- B TNGB tng ct thepB tng admB tng gach vB tng xB tng bt hp hi nongB tng bot hp hi nong
Tm thach cao p mt tngTm vaming thach cao nguyn chtIII- VT LIU TGach mcIV- MANG GACH XY CGach thng thng vi va nngGach rng (=1300), xy va nhe(=1400)Gach nhiu lxy va nngV- VT LIU TRAT VAVAVa xi mng vava trat xi mng
Va tam hp vava trat tam hpVa vi trat mt ngoaiVa vi trat mt trongTm p mt ngoai bng thach caoTm si gcng p mtVI- VT LIU CUNGiy cactng thngGiy tm du thng nha ng bitum hay hc nTham bng dung tronh nhaTham bng khoang chtVII- VT LIU THUYTINHKnh ca sSi thuytinhThuytinh hi vathuytinh botThuytinh hi vathuytinh botVIII- VT LIU GGthng, tung ngang thMun ca
1900500300
24002200180015001000400
10001000
1600
180013501300
1800
1700160016001000700
700600150200
2500200500300
550250
0,3490,1280,093
1,5471,2790,8720,6980,3950,151
0,2330,407
0,698
0,8140,5810,523
0,930
0,8720,8720,6980,2330,233
0,1740,1740,0580,069
0,7560,0580,1630,116
0,1740,093
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3233343536
373839
GdanTm bng si gepTm bng si gepTm bng si gepTm gmm (lie)IX- VT LIU KHAC
Tm silicat bmt in hoa vatm ximng silicat in hoaTm silicat bmt in hoa vatm ximng silicat in hoaTm silicat bmt in hoa vatm ximng silicat in hoa
600600250150250
600400250
0,1740,1630,0760,0580,069
0,2330,1630,116
3.2.8.2 Nhit truyn qua nn t Q82 tnh nhit truyn qua nn ngi ta chia nn thanh 4 dai, mi dai cob rng 2m nh
hnh ve3-1.Theo cach phn chia nay
- Dai I : k1= 0,5 W/m2.oC , F1= 4.(a+b)- Dai II : k2= 0,2 W/m2.oC , F2= 4.(a+b) - 48
- Dai III : k3= 0,1 W/m2.oC , F3= 4.(a+b) - 80- Dai IV : k4= 0,07 W/m2.oC , F4= (a-12)(b-12)Khi tnh din tch cac dai, dai I cac goc c tnh 2 ln v cac goc nhit cothtruyn
ra bn ngoai theo 2 hng- Khi din tch phong nhohn 48m2th cothcoi toan bladai I- Khi chia phn dai nu khng ucho 4 dai th u tin t1 n 4. V duch chia c 3
dai th coi dai ngoai cung ladai I, tip theo ladai II vaIII.Tn tht nhit qua nn do truyn nhit
Q82= (k1.F1+ k2.F2+ k3.F3+ k4.F4).(tN- tT) (3-41)
Hnh 3.1 : Cach phn chia dai nn
3.2.9 Tng lng nhit tha QTTng nhit tha cua phong :
== 8
1 ,,
iT kWQQ 3-42
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Nhit tha QT c s dung xac nh nng sut lanh cua b x ly khng kh trongchng 4. Khng nn nhm ln khi cho rng nhit tha QTchnh lanng sut lanh cua bxlykhng kh .
Tng nhit tha cua phong QTgm nhit hin Qhf vanhit n Qwfcua phong.- Tng nhit hin cua phong :
Qhf= Q1+ Q2+ Q3h+ Q4h+ Q5+ Q6+ Q7h+ Q8
- Tng nhit n cua phong :Qwf= Q3w+ Q4w+ Q7wNh atrnh bay trn , trng hp khng gian khao sat lanhahang th bnh qun mi
ngi cng thm 20W do thc n toara , trong o10W lanhit hin va10w lanhit n.
3.3 XAC NH LNG M THA WT3.3.1 Lng m do ngi toa ra W1Lng m do ngi toa ra c xac nh theo cng thc sau :
W1= n.gn, kg/s (3-43)n - Sngi trong phong.
gn- Lng m do 01 ngi toa ra trong phong trong mt n v thi gian, kg/sLng m do 01 ngi toara gnphuthuc vao cng lao ng vanhit phong. Trsgncothtra cu theo bang 3.16 di y :
Bang 3.16 : Lng m do ngi toa ra, g/gi,ngi
Nhit khng kh trong phong, oCTrang thai lao ng10 15 20 25 30 35
Treem di 12 tui 15 18 22 25 35 60Tnh tai 30 40 40 50 75 115
Lao ng tr hoc (cquan, trng hoc)
30 40 75 105 140 180
Lao ng nhe 40 55 75 115 150 200Lao ng trung bnh 70 110 140 185 230 280Lao ng nng 135 185 240 295 355 415Phong n, khach san 90 90 171 165 250Vutrng 160 160 200 305 465
3.3.2 Lng m bay hi t cac san phm W2
Khi a cac san phm t vao phong th comt lng hi nc bc vao phong. Ngc lainu a san phm kh th nosehut mt lng m.W2= G2.(y1% - y2%)/100 kg/s (3-44)
y1, y2- Ln lt lathuy phn cua san phm khi a vao vara.g2- Lu lng cua san phm , kg/sThanh phn m tha nay ch cotrong cng nghp
3.3.3 Lng m do bay hi oan nhit tsan m W3
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Khi san b t th mt lng hi m tocothbc hi vao khng kh lam tng mcua no. Lng hi m c tnh nh sau :
W3= 0,006.Fs.(tT- t) kg/s (3-45)Fs- Din tch san b t, m2t- Nhit nhit kt ng vi trang thai trong phong.
Lng m do bay hi oan nhit c tnh cho ni thng xuyn nn nhab t nh khu
nhagit, nhabp, nhavsinh . Ring nn t do lau nhathng nht thi vakhng lin tuc,nn khi tnh lu yn im nay.3.3.4 Lng m do hi nc nong mang vao W4
Khi trong phong coror hi nong , v dunh hi tcac ni nu, th cn phai tnh thmlng hi m thoat ra tcac thit b nay.
W4= Gh (3-46)3.3.5 Lng m tha WT
Tng tt cac ngun m toara trong phong goi lalng m tha
Nhit tha WTc sdung xac nh nng sut lam kh cua thit b xlykhng kh chng 4.3.4 KIM TRA ONG SNG TRN VACH
Nh abit khi nhit vach tW thp hn nhit ong sng cua khng kh tip xuc vinoth sexay ra hin tng ong sng trn vach o. Tuy nhin do xac nh nhit vachkhonn ngi ta quy iu kin ong sng vdang khac.
* Vmua he: Mua heta thc hin chiu hoa (lam lanh), nhit bn ngoai ln hnnhit bn trong:
Khi o tTW > tT > tTs, nh vyvach trong khng thxay ra hin tng ong sng.
Goi tN
slanhit ong sng vach ngoai ta co iu kin ong sng:tNs > tNWTheo phng trnh truyn nhit ta co
k.(tN- tT) = N.(tN- tNW)hay:
k = N.(tN- tNW)/ (tN- tT)Khi giam tNW th k tng, khi giam ti tNsth trn tng ong sng, khi ota c giatr
kmaxkmax= N.(tN- tNs )/ (tN- tT)
iu kin ong sng c vit lai:
kmax= N.(tN- tN
s )/ (tN- tT) > k (3-48)
* Vmua ng: Vmua ng lylun tng ttrn ta thy nu xay ra ng sng th chcothxay ra trn vach tng trong. Khi oiu kin khng ong sng trn vach trongla:
kmax= T.(tT- tTs )/ (tT- tN) > k (3-49)*
*****
=
=4
1
/,i
iT skgWW 3-47
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CHNG 4THANH LP VATNH TOAN
CAC S IU HOAKHNG KH
Thanh lp s iu hoa khng kh la xac nh cac qua trnh thay i trang thai cua
khng kh trn th I-d nhm muc ch xac nh cac khu cn xlyvanng sut cua noat c trang thai khng kh cn thit trc khi cho thi vao phong.S iu hoa khng kh c thanh lp trn c s:a) iu kin kh hu a phng ni lp t cng trnh :tNvaN.b) Yu cu vtin nghi hoc cng ngh : tTvaT.c) Cac kt quatnh cn bng nhit : QT, WT,d) Thoa man iu kin vsinh:
1. Nhit khng kh trc khi thi vao phong khng c quathp so vi nhit trong phong nhm tranh gy cam lanh cho ngi sdung, cuthnh sau :
tVtT- a (4-1)
- i vi h thng iu hoakhng kh thi tdi ln (ming thi t trong vung lamvic) : a = 7 oC
- i vi hthng iu hoakhng kh thi t trn xung : a = 10oCNu iu kin vsinh khng thoa man th phai tin hanh sy nong khng kh ti nhit
tV= tT- a thoaman iu kin v sinh ri cho thi vao phong.2. Lng kh ti cp vao phong phai am bao ucho ngi trong phong.
LN = n.mk= n.k.Vk (4-2)trong o:
n - Sngi trong phongmk- Khi lng gio ti cn thit cung cp cho 01 ngi trong mt n v thi gian,
kg/ngi, gi.Vk- Lng khng kh ti cn cung cp cho mt ngi trong mt n v thi gian, tra
theo bang 2-7, m3/ngi, gi.- Khi lng ring cua khng kh, = 1,2 kg/m3.Tuy nhin lu lng giobsung khng c nhohn 10% tng lng giocung cp cho
phong.4.1 TNH TOAN CAC S IU HOAKHNG KH THEO TH I-d4.1.1 Phng trnh tnh nng sut gio
Tcac phng trnh cn bng nhit, m vacht c hai ta xac nh c phng trnh xacnh nng sut gio.
- Nng sut giothai nhit :Lq= QT/(IT-) (4-3)
- Nng sut giothai m:LW= WT/(dT- dV) (4-4)
- Nng sut giothai cht c hai:Lz= GT/(zT- zV) GT/zT (4-5)
Trong cac cng thc trn T latrang thai khng kh trong phong, V latrang thai khng khtrc khi thi vao phong.
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O
1
4
6
T7V
WTQT
3N
5
T
2
O=V
Tt
=100%
=95%N
N
tN
T
T
I
d
Khi thit kh thng iu hoa thng phai am bao 2 thng snhit vam khng itheo yu cu , tc laphai thoa man ng thi 2 phng trnh cn bng nhit vam. Hay noicach khac ta co: LQ= Lw
Suy ra
Hay
ai lng Tgoi lahsgoc tia cua quatrnh tthay i trang thai cua khng kh trongphong do nhn nhit tha vam tha.
Nh vy trang thai cua khng kh trong phong khng i th trang thai khng kh thivao phong V(tV, V) phai lun lun nm trn ng T = QT/WTi qua im T(tT, T)
4.1.2 Cac s iu hoakhng kh mua he4.1.2.1. S thng
S thng las khng co tai tun hoan khng kh tphong vthit b xlykhngkh. Trong s nay toan bkhng kh a vao thit b xlykhng kh lakhng kh ti.
S thng c trnh bay trn hnh 4.1
Hnh 4.1 : S nguyn lyvabiu din sthay i trang thai khng kh trn th I-d
*Nguyn lylam vic: Khng kh bn ngoai tri cotrang thai N(tN,N) qua ca ly giocovaniu chnh (1), c a vao bung x lynhit m (2), tai y khng kh c xly theochng trnh nh sn n mt trang thai O nht nh nao ovac quat (3) vn chuyntheo ng ng gio(4) vao phong (6) qua cac ming thi (5). Khng kh tai ming thi (5)cotrang thai V sau khi vao phong nhn nhit tha vam tha vatthay i n trang thaiT(tT, T) theo tia quatrnh T= QT/WT. Sau okhng kh c thai ra bn ngoai qua cac cathai (7).
S thng c sdung trong cac trng hp sau:- Khi knh giohi qualn vic thc hin hi gioquatn kem hoc khng thc hin c
do khng gian nhohep .
VT
T
VT
T
dd
W
II
Q
=
VT
VT
T
T
dd
II
W
Q
=
T
T
T
d
I
W
Q=
=
(4-6)
(4-7)
(4-8)
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V Tt=t-a
V
=100%
N
tNN
I
TtT
=95%
dO
T
T
- Khi trong khng gian iu hoa cosinh ra nhiu cht c hai, vic hi giokhng coli.Mua henc ta nhit va m bn ngoai phong thng cao hn nhit vam
trong phong. V thim N thng nm bn trn phai cua im T.
* Xac nh cac cac im nut :Theo th biu th quatrnh ta co:
- Quatrnh NO laquatrnh xlykhng kh din ra thit b xlykhng kh. Trang thaiO cui quatrnh xlykhng kh com o95%.- Quatrnh OV laquatrnh khng kh nhn nhit khi dn qua hthng ng ng. Qua
trnh nay khng trao i m, olaquatrnh gia nhit ng dung m. V tt cacac ng ngdn khng kh lanh u boc cach nhit nn tn tht nay khng ang k. Thc tcothcoiVO
- Qua trnh VT laqua trnh khng kh t thay i trang thai khi nhn nhit tha vamtha nn cohsgoc tia VT= T= QT/WT
Tphn tch trn ta cothxac nh cac im nut nh sau:- Xac nh cac im N(tN, N), T(tT, T) theo cac thng stnh toan ban u.
- Qua im T keng = T= QT/WTct ng o= 0,95 tai OV- Ni NO ta coquatrnh xlykhng kh
Cn lu ytrang thai thi vao VO phai am bao iu kin vsinh lanhit khng cquathp so vi nhit trong phong tranh gy cam lanh cho ngi sdung.
tVtT- aNu khng thoa man iu kin vsinh , th phai gia nhit khng kh t trang thai O ln
trang thai V thoaman iu kin vsinh mi thi vao phong , tc latV= tT- a (hnh 4.2).
Hnh 4.2: S thng khi nhit tVthp
Trong trng hp nay cac im O vaV xac nh lai nh sau :- im V lagiao cua ng = T= QT/WT qua im T va ng t = tT- a .- im O lagiao cua ng thng ng (ng dung m) qua im V vang o= 0,95.
* Cac thit b chnh cua quatrnhthc hin c s thng mua he cn cocac thit b chnh sau : Thit b xlykhng
kh, quat cp gio, bsy cp II, hthng knh cp gio, ming thi.
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* Xac nh nng sut cac thit b- Nng sut giothi vao phong :
- Nng sut lanh cua thit b xly:
- Nng sut lam kh cua thit b xly:
- Cng sut nhit cua thit b sy cp II (nu co) :
* Kt lun:
- S thng cou im lan gian, gon nhedlp t.- Khng tn dung nhit t khng kh thai nn hiu quathp.- Thng c sdung trong cac hthng ni cophat sinh cac cht c, hi hoc ng
ng quaxa, cng knh khng kinh thoc khng th thc hin c.
4.1.2.2. S tun hoan khng kh mt cptn dung nhit cua khng kh thai ngi ta sdung s tun hoan1 cp.
Trn hnh 4.3 las nguyn lyhthng tun hoan 1 cp* Nguyn lylam vic: Khng kh bn ngoai tri cotrang thai N(tN,N) vi lu lng LN
qua ca ly gio co van iu chnh (1), c a vao bung hoa trn (3) hoa trn vi
khng kh hi cotrang thai T(tT,T) vi lu lng LTtcac ming hi gio(2). Hn hp hoatrn cotrang thai C sec a n thit b xly(4), tai y noc xlytheo mt chngtrnh nh sn n mt trang thai O vac quat (5) vn chuyn theo knh gio(6) vao phong(8) . Khng kh sau khi ra khoi ming thi (7) cotrang thai V vao phong nhn nhit tha QTvam tha WTvatthay i trang thai tV n T(tT, T). Sau omt phn khng kh cthai ra ngoai vamt phn ln c quat hi gio(11) hut v qua cac ming hut (9) theo knh(10) .
Hnh 4.3 S tun hoan 1 cp
skgdd
W
II
QL
VT
T
VT
T /,
=
=
kWII
IIQIILQ
VT
oN
ToNo ,).(
==
skgdd
ddWddLW
VT
oN
ToN /,).(
==
kWII
IIQIILQ
VT
oV
ToVSII,).(
==
(4-9)
(4-10)
(4-11)
(4-12)
LT
3
2
C
N NL1
1110
L + LN T
4
L5
6V
7
T
TTQ W
8
9
12O
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C
=95%
N
NtN
d
T
tTT
O=V
T
=100%
I
* Xac nh cac im nut trn I-d- Trang thai C latrang thai hoatrn cua dong khng kh ti colu lng LN vatrang thai
N(tN, N) vi dong khng kh tai tun hoan vi lu lng LTvatrang thai T(tT, T)- Qua trnh VT laqua trnh khng kh t thay i trang thai khi nhn nhit tha vam
tha nn cohsgoc tia = T= QT/WT. im OV coo0,95 .Tphn tch trn ta cocach xac nh cac im nut nh sau :
- Xac nh cac imN, T theo cac thng stnh toan ban u.- Xac nh im hoa trn C theo t lhoa trnTa co
trong o:LN- Lu lng gioti cn cung cp c xac nh theo iu kin vsinh, kg/s.L - Lu lng gio tng tun hoan qua thit b x lykhng kh c xac nh theo
cng thc (4-13), kg/s- im VO lagiao nhau cua ng = T= QT/WTi qua im T vi ng o= 0,95.
Ni CO ta coquatrnh xlykhng kh.
Hnh 4.4 : Biu din s tun hoan 1 cp trn th I-d
Nu nhit im O khng phuhp iu kin vsinh th phai tin hanh sy khng khn im V thoaman iu kin vsinh tc lat = tT- a (xem hnh 4-5). Khi ocac im V vaO xac nh nh sau:
- TT keng = T= QT/WTct t = tT- a tai V- TV kng thng ng ct o= 0,95 tai O.- Cac im con lai vn ginguyn v tr.
* Cac thit b chnh : thc hin s iu hoa khng kh mt cp ta phai cocac thit bchnh sau y : Quat cp gio, quat hi gio, thit b x lykhng kh, thit b sy cp 2, hthng knh cp gio, hi gio, ming thi vaming hut
N
N
T
N
LL
L
L
L
CN
TC
==
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11T
WQ
C2
LT
3
2L + L
N T1
13
6
12
TT
NL
N
C11 L
78 V
9 1014
L
4
T2
5LT1
4.1.2.3 S tun hoan khng kh hai cpkhc phuc nhc im cua s 1 cp do phai cothit b sy cp 2 khi trang thai V
khng thoa man iu kin vsinh, ngi ta sdung s 2 cp cothiu chnh nhit khng kh thi vao phong makhng cn cothit b sy.
1. S iu chnh nhit thi vao
* S nguyn ly:
Hnh 4.6 : S tun hoan 2 cp coiu chnh nhit
* Nguyn lylam vic: Khng kh bn ngoai tri vi lu lng LN va trang thai N(tN,N)c ly qua ca ly giocovan iu chnh (1) vao bung (3) hoa trn vi khng kh hi colu lng LT1vatrang thai T(tT,T) at mt trang thai C1nao o. Hn hp hoa trn C1sec a n thit b xly(4) vac xly n trang thai O. Sau on bung hoatrn (6)hoa trn vi khng kh hi colu lng LT2vatrang thai T(tT,T) at trang thai C2vac quat (7) vn chuyn theo ng ng gio(8) vao phong (10). Khng kh sau khi ra khoiming thi (9) co trang thai C2vao phong nhn nhit tha vam tha va tthay i trangthai n T(tT, T) . Cui cung mt lng c thai ra ngoai qua ca thai 14, phn ln con lai
c hi vtip tuc xly.
* Xac nh cac im nut- Cac im nut N(tN, N), T(tT, T) c xac theo cac thng stnh toan.- im hoa trn C2: Muc ch cua vic hoatrn lanhm am bao nhit khng kh khi
thi vao phong thoaman yu cu vsinh. Hay tC2= tT- a. Nh vy im C2lagiao im cuang T= QT/WT i qua T vi tC2= tT- a.
- im O nm trn ng o= 0,95 vang keo dai TC2.- im C1c xac nh theo t shoa trn : LN/LT1= TC1/C1N
* Cac thit b chnhthc hin s iu hoa khng kh hai cp ta phai cocac thit b chnh sau y : Quat
cp gio, quat hi gio, thit b xlykhng kh , hthng knh cp gio, hi giovacac mingthi, ming hut.
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Hnh 4.7 : Biu din s tun hoan 2 cp coiu chnh nhit trn I-d
* Xac nh nng sut cac thit b- Lu lng gio:
- Lng khng kh bsung LNc xac nh theo iu kin vsinh nh sau :LN= n..Vk kg/s (4-20)
- Lu lng gioLT2xac nh theo phng phap hnh hoc da vao quatrnh hoa trn thitb hoa trn (6):
Cac im T, C2vaO ac xac nh nn cothtnh c LT2
- Lu lng gioLT1LT1= L - LN- LT2 (4-22)
- Nng sut lanh cua thit b xly:Qo= (L-LT2).(IC1- IO) , kW (4-23)
- Nng sut lam kh cua thit b xly:W = (L-LT2).(dC1- dO) , kg/s (4-24)
* Kt lun:S tun hoan 2 cp coiu chnh nhit thi vao cou im:
- Nhit thi vao phong cothddang iu chnh c nhiu chnh lng giotrchLT2 nhm nng nhit thi vao phong thoaman iu kin vsinh. Do os 2 cp co
iu chnh nhit khng cn trang b thit b sy cp II.- Nng sut lanh vanng sut lam kh yu cu cua thit b xlygiam
+ Cng sut lanh giam QO = LT2.(IC1- IO)+ Lu lng gio giam L = LT2.(dC1- dO)
Nh vy ta khng cn phai u t hthng xlykhng kh qua ln, cng knh.- Phai cothm bung hoa trn th2 vahthng trch gion bung hoa trn nay nn chi
ph u t vavn hanh tng.
skgdd
W
II
QL
CT
T
CT
T /,22
=