Chapter 5 KTTK

7/30/2019 Chapter 5 KTTK

1/26

Presented By

Harry Mills /PRESENTATIONPRO

Chng : CHUYN NG MT CHIU CACHT LNG KHNG NN

Gii thiu cc loi tn tht

Ni dung chnh

Tm hiu th nghim Reynolds

Tnh ton tn tht dc ng

Cht lng chy tng

Cht lng chy ri

Tnh ton tn tht cc b

K thut thu kh
http://www.presentationpro.com/power_designs.aspxhttp://www.presentationpro.com/power_designs.aspxhttp://www.presentationpro.com/power_designs.aspxhttp://www.presentationpro.com/power_designs.aspx


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K thut thu kh


5.1 TN THT NNG LNG DNG CHY

5.1.1 Nguyn nhngy tn tht

Chtlng c

tnh nht

C s ma sttrong khi

chuyn ng

Binthnh

nhit nng

Nhit ivo mi

trng


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5.1.1 Nguyn nhngy tn tht

Bm cp nng lng cho

cht lng chuyn ng K thut thu kh


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Hai loi tn tht chnh

K thut thu kh

KhoTn tht ccb

Tn tht dc -ng


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5.1.2 Tn tht dc ng

K hiu

dn v mCng thc tnh tng qut

Sinh ra trn ton b

chiu di dng chy.L tn tht xy radc theo ng dichuyn ca dng

chy do s ma stca cht lng vithnh rntip xcg2

v

R4

l.h

2

d

K thut thu kh


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5.1.2 Tn tht dc ng

Trong : hssccn ma st,phthuc votrng thi chyca dng chy. l (m)chiu di on tnh tntht. R (m) bn knh thulc v (m/s) vntcon dng chy ng trn: d = 4R

K thut thu kh

g2

v

R4

l.h

2

d


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5.1.3 Tn tht cc b

K hiu

cn v mCng thc tnh tng qut

Sinh ra ti nhngni dng chybinitngt. Thdtnthttich cong

cang, tn tht tini thu hp, ti cht van...g2

v.h2

Cc

K thut thu kh


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5.1.3 Tn tht cc b

c l hs tn thtccb,phthuc vo tngv trxy ra tntht. v (m/s) vn tcv tr

xy ra tntht.

Trong :

K thut thu kh

g2

v.h

2

Cc


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5.1.3 Tn tht cc b

Tn tht nng lng ca ton b

on dng ang xt

m

i

di

n

i

Ciw hhh11

21

m

1i

2

i

i

ii

n

1i

2

iCi21w

g2

v

d

l

g2

vh

K thut thu kh

n: s v tr tn tht cc b

m: s on ng tnh ton tn

tht dc ng


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5.2 HAI CH CHY TH NGHIM REYNOLDS

5.2.1 Cc ch chy ca dng chy

Chy tng

cc phn tcht lng

chuyn ng

theo nhngtng lp khng

xo ln vo

nhau

Chy ri

cc phn t chtlng chuyn

ng v trt t,hn lon

K thut thu khLink th nghim
http://localhost/var/www/apps/conversion/releases/20121107221618/tmp/phim/dns-large.mpeghttp://localhost/var/www/apps/conversion/releases/20121107221618/tmp/phim/dns-large.mpeghttp://localhost/var/www/apps/conversion/releases/20121107221618/tmp/phim/dns-large.mpeg


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5.2.2 Th nghim Reynolds

Thay i vn tc dng chy trong ng

Thay i nhit nc t 4oC n 44oC

Th nghim nhiu ng c ng knh khc nhau

K thut thu kh

Kt lun: Dng chy thay i trng thi khi thay i cc yu t trn
http://localhost/var/www/apps/conversion/releases/20121107221618/tmp/phim/dns-large.mpeghttp://localhost/var/www/apps/conversion/releases/20121107221618/tmp/phim/movie_streak_cyl.mpeghttp://localhost/var/www/apps/conversion/releases/20121107221618/tmp/phim/movie_iso_obst.mpeg


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5.2.2 Th nghim Reynolds

Trng thi

chy phthuc vo

Vn tcdng chy

Kch

thc ngLoi cht

lng

K

thut thu

kh


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5.2.3 Tiu chun phn bit hai ch chy

K

thut thu

kh

Tiu chunphn bit

ch chy

Dng t hp khng th nguyn (s Reynolds)

d.vRe

Lu : cng thc trn dng tnh cho ngtrn ng knh d.


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5.2.3 Tiu chun phn bit hai ch c chy

K

thut thu

kh

Mt ct bt k

Trong : (m2/s): H s nht ng hc

d (m) : ng knh ngv (m/s) : Lu tc trung bnh mt ctR (m) : Bn knh thu lc mt ct

RR .vRe


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K thut thu kh


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K

thut thu

kh

Vd:Xc nh trng thi chycadu trong ngnung c ng knh d=150mm; vn tc v=0,3m/s; nhtng=0,28 st (1 st = 1 cm2/s)?

Ktqu: Re=1607 < 2320

Kt lun:Du chy tng trong ng


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5.3 TNH TON TN THT DC NG

K

thut thu

kh

Xc nh trng thi chy ca dng chy

Xc nh h s sc cn ma st

Chy tng:Re

64

Chy ri: Ref


18/26

Presented ByHarry Mills /PRESENTATIONPRO


5.3 TNH TON TN THT DC NG

K

thut thu

kh

Tn Cngthc

2

8

C

g

Chezy Maning

Blart

Canacp

Antsun

Nicurats

4 Re

3164,0

25,1Relg8,11

25,0

Re

10046,11,0

d

2

14,1lg2

1

d

Gii thiu mt s cng thc tnh khi dng chy ri


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5.4 TNH TON TN THT CC B

K

thu

t thu

kh

g

v

g

vvhc

21

2

21

2

2

12

21

V1; 1

V2; 2

1

1

2

22

2

11

mr

Mt s v tr xy ta tn tht cc b thng gp

Tn tht do t ngt m rng

Dng chy t ng i vo b cha rt rng cr=1


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K thut thu kh


Tn tht do t ngt thu hp

Dng chy t b cha rt rngi vo ng cv=0,5

1

215,0

tc

1 2


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K thut thu kh


Tn tht un

- Nu gc cong = 90o

ca ng trn bn knh ro,bn knh cong l R ta c:

5,3o

CR

r85,113,0

- Nu gc cong 90o

ta nhn Cvi o90

R

ro


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K thut thu kh


Tn tht qua van

H s Cph thuc vo gc m cho bi bng sau y:

o 5 10 20 30 40 50 60 70 80

C 0,05 0,29 1,56 5,47 17,3 52,6 206 486


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Bi tp v d:

K thut thu kh

H1

H2


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Bi tp v d:

K thut thu kh

ngc ngknh ngthnhtd1 =200mm; l1=20m;ngthhai d2=100mm; l2=35m.

H1 = 15m; H2 =5m

Hstnthttica vo: cv = 0,5; ti van v=1,56; cara cr=1; un cong tibm v qua bmu=0,9.Hscn ma stng1 1=0,026; 2=0,02;Cht lng l nc c nht ng =0,0101 (cm2/s);

r=998,23kg/m3

Mtthong 2 btip xc vi khtri.Ctp bm cung cp cho hthngl Hb=5m.Lyhshiuchnhngnng=2.


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Bi tp v d:

K thut thu kh

Tm:

1/ Lu lng Q chy trong ng? V kim tra trng thi chy

ca dng chy trong 2 ng? (chung c nhm tho lun)2/ Tm tn tht ti ca vo? (T 1)3/ Tm tng tn tht dc ng trn ng 1? (T 2)4/ Tm tn tht un v qua bm? (T 3)5/ Tm tng tn tht dc ng trn ng 2? (T 4)6/ Tm tn tht qua van? (T 5)7/ Tm tn tht ti ca ra? (T 6)


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THO LUN TUN TH 11

CH : TNH TON TN THT

C nhm thit lp bi ton

Nhm khc gii quyt

Nhm thit lp gii quyt bi ton

K thut thu kh

a ra bi ton v tr li trc 10pht

a ra bi ton v tr li trc 15 pht

a ra bi ton v tr li trc 20pht

a ra bi ton v tr li sau 25 pht

100%

80%

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20%

Chapter 5 KTTK

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