Tinh Toan Tke Hthong Dieu Hoa Khong Khi

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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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 khng =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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4

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


16/229


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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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7

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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8

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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9

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


21/229

10

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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21

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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22

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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23

(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

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32/229

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34

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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


36/229

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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

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NamNam Ty

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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


38/229


39/229


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39

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

=

Tinh Toan Tke Hthong Dieu Hoa Khong Khi

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