2. ΨΥΧΡΟΜΕΤΡΙΚΗ...

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Transcript of 2. ΨΥΧΡΟΜΕΤΡΙΚΗ...

5

, , .

5.1 , , . 1 2 ma . , :m a3 3 = m a1 1 + m a 2 2

3 = :

ma1 1 + ma2 2 m a3

(38)

m a3 = m a1 + m a2

. , :

h3 =

ma1 h1 + ma2 h2 m a3

(39)

(24) , :

(c t

p 3

+ h fg 0 3 =

)

ma1 ma3

(c tp

1 + h fg 0 1 +

)

m a2 m a3

(c t

p 2

+ h fg 0 2

)

, :

t3 =

ma1 t1 + ma2 t 2 m a3

+

h fg 0 ma1 ma 2 1 + 2 3 cp m a3 m a3

, :

t3

ma1 t1 + ma2 t 2 ma3

(40)

T cp . , h, . t ( 5.1) . 1 2 ma1 ma2 .

5.1(). . 5.1(). .

5.1 30 m3/min 15 C 13 C 12 m3/min 25 C 18 C . . . , : t1 = 15 oC, t1 = 13 oC, u1 = 0.827 m3/kg d.a., 1 = 0.0084 kg w.v./kg d.a. , h = 36.85 kJ/kg d.a. t2 = 25 oC, t2 = 18 oC, u2 = 0.959 m3/kg d.a. 2 = 0.01 kg w.v./kg d.a., h2 = 51.1 kJ/kg d.a. , : ma1 = 30/0.827 = 36.2 kg d.a./min ma2 = 12/0.859 = 13.9 kg d.a./min ma3 = 36.2 + 13.9 = 50.1 kg d.a./min 3 = [36.2(0.0084) + 13.9(0.01)]/50.1 = 0.00886 kg w.v./kg d.a. h3 = [36.2(36.85) + 13.9(51.1)]/50.1 = 40.8 kJ kg/d.a. 3 h3 DBT , t3 = 16 oC WBT , t3 = 14.5 oC 5.2 2 C 80 % , 30 C 10 C , . .

1 = 0,0035 kg w.v./kg d.a. h1 = 10.78 kJ/kg d.a. H , : ma1 = 1/(1 + 1) kg = 1/1.0035 = 0.9955 kg 2 = 0,00765 kg w.v./kg d.a. h2 = 49.67 kJ/kg d.a. : ma2 = 2/(1 + 2) kg = 2/1.00765 = 1.9848 kg h = [0.9965(10.78) + 1.9848(49.67)]/(0.9965 + 1.9848) = 36.68 kJ/kg d.a. = [0,9965(0,0035) + 1,9848(0,00765)]/(0,9965 + 1,9848) = 0,00627 kg w.v./kg d.a.

5.1.1 , , , 5.2 . 0 C, . 4, 3, (38), 5.2(). t4 t3, . c , : c = 3 4

4 =

ma1 1 + ma2 2 ma1 + ma2

(41)

m a4 h4 + m a4 c h f 4 = m a4 h3

h4 =

ma1 h1 + ma2 h2 ma1 + ma2

c h f4

(42)

5.2(). . 5.2(). .

hf4 t4 . (41) (42) t4 c. t4 4, h4 hf4, , . . , , , , .

5.2 , , 5.3. : (i)

(ii) (i) (ii) (iii) (iv) (v) (vi)

OC OD OE F OG

5.3. . , , . , . C D . , . , , . .

5.2.1 , 5.4, , : Qs = macp(tB tA) = macp(tB tA) + macpv(tB tA)

= ma(1.005 + 1.88)(tB tA) = ma(hB hA)

(43)

cp . s, . , , . , . , . . (43) ma . (cmm). : ma = Qv (44)

Qv . (cmm), : ma =

(cmm)60

kg ../s

(44)

, 20 C 50 % RH. 1,2 kg/m3 ... 1,0216 kJ/(kg ..)(K). (43), : Qs =

60 = 0.0204 (cmm)t, kW

(cmm )(1,2 )(1,0216 ) t(45)

, , td 5.4. .

5.4. . 5.5.

5.2.2 t (t = ), BC 19, , . : G = ma (C - B) (46)

, , (hC hB), 19. , , : QL = ma (hC hB) = ma (cptC + h fg 0 C) (cptB + h fg 0 B) = ma h fg 0 (C B) =G h fg 0 (47)

cp B C. , QL hfg0. , QL.

, . , . , , . 2500 h fg 0 (47) (44) ma, : QL = (cmm)(1.2)(2500)/60 = 50 (cmm) , kW (48)

5.2.3 AC, 5.6. , . : QS = ma(hB hA) = macp(tC tA) (49) , : G = ma(C A) : QL = ma(hC hB) =ma h fg 0 (C A) (50)

(49) (50) : Q = QS + QL = ma(hC hA) =ma[cp(tC tA) + h fg 0 (C )] (51) (51)

5.6. . cmm, :Q=

60 = 0.02(cmm) h

(cmm )(1,2) h

(52)

: Q = (cmm)(0.0204t + 50) (52)

5.2.4 (SHF) O , . SHF (Sensible Heat Factor) : SHF =

QS Q = S QS + Q L Q

Q, Qs QL (45) (52), :

SHF =

hB h A h hA = B (hB hA ) + (hC hB ) hC hA 0,0204t 0,0204t = = 0,0204t + 50 0,02h

(53)

20 (hC hA) SHF (1 SHF). , , , BC, (1 SHF). , . . . 0,75 0,8 . . (53) : SHF =

1 1 + 2451 t(54)

= : tan =

1 1 + tan

t 1 1 = 1 2451 SHF

(55)

, . , : (i) (ii)

, . : 1. , tan. t=()(tan) . 2. , hL. . SHF hS = (hL ) 1 SHF . 3. SHF. SHF . , SHF.

5.3 5.2 . , . , . . , , .

5.3.1 5.7 . 1 2 , S. , , . . . .

, , 2 5.7.

5.7. . BPF (By-Pass Factor) , 1,2,S , := t 2 t S 2 S h2 hS = = t1 t S 1 S h1 hS

(1-) . . , . 5.7 2 1 S (1-).

5.3.2 , . ( 5.8)

5.8. . tS , 5.9. DPT. . 5.9 2 BPF . BPF , . , , td .

5.9. .

5.9 1-S , 2. tS . . . . tS td 5.10. , . (t-is). (pv-pvs) (-s), pvs , ts. To 1-S . 1-S. H 2 BPF .

5.10. . . 1-S 5.10 , . 1-S 1. 1-S ,

ts , . SHF . 5.3 39,6 cmm , , 31 C DB 18,5 C WB. 4,4 C. 12,5 kW . . 5.10, : s = 5,25 g/kg d.a. hs = 17.7 kJ/kg d.a. : 1 = 8,2 g/kg d.a. u1 = 0.872 m3/kg d.a. h1 = 52.5 kJ/kg d.a. : ma = Qv/u = 39.6/0.872 = 44.41 kg d.a./min kg : h1 h2 = Q/ma = (12.5)(60)/44.41 = 16.89 kJ/kg d.a. : h2 = 52.5 16.89 = 35.61 kJ/kg d.a. H : (h1 h2)/(h1 hs) = (1 2)/(1 - s) (52,5 35,61)/(52,5 17,7) = (8,2 2)/(8,2 5,25) : 2 = 6,77 g w.v./kg d.a. , h2, 2 : t2 = 18.6 oC t2 = 12.5 oC O : X = (h2 hs)/(h1 hs)

= (35.61 17.7)/(52.5 17.7) = 0.515 5.3.3 , 5.8 ts ( 5.11). . , , .

5.11. .

5.3.4 5.12 . . , , , , . , , , . . .

5.13 1-2 , ts , tw. . . :

5.12. .

1-2 : (ts>t1) H . . 1-2 : (ts=t1) H . . 1-2C : (t1