Issiqlik almashtirgichni hisoblash

Issiqlik almashtirgichni hisoblash
Qurilmaning termal yuki:
Q = G1∙c1∙(t1n–t1 gacha),
qayerda bilan1= 1850 J/kg∙K – bitumning issiqlik sig'imi [19]; G1- bitumning ommaviy iste'moli. Qabul qiling G1=2000 kg/soat = 0,56 kg/s
Q - issiqlik oqimi, termal hisobdan. Q= 35210,1 kJ/soat = 9780,58 Vt Bitumning oxirgi harorati
t1k
|
|
G1 c1 t1n -Q
|
,
|
|
|
|
|
|
G1 c1
|
t
|
|
0,561850250-9780.58
|
=503K=2300BILAN
|
|
1k
|
|
|
0,561850
|
|
|
|
O'rtacha harorat farqi:
tm= t1n–t2k= 250 - 60 = 190 ºS
tb= t1 gacha–t2n= 230 - 20 = 210 ºS
Munosabatdan beri∆ b=210= 1.11<2, Bu
∆m 190
tsr tb / 2,∘BILAN
tm
tChorshanba 190210 / 2 200 C
O'rtacha havo harorati:
t2 chorshanba
|
|
t2k t2 n
|
∘BILAN
|
|
|
|
|
2
|
|
|
t
|
|
|
6020
|
40C
|
2 chorshanba
|
|
|
2
|
|
|
|
|
|
|
Bitumning o'rtacha harorati:
t t1n tChorshanba ;
1wd 2
(50)
(51)
t
|
|
250200
|
|
225S
|
|
|
|
1wd
|
|
|
|
|
2
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Havo oqimi
|
|
|
|
|
|
|
|
G2
|
|
|
|
|
|
Q
|
|
|
|
|
|
|
,
|
(52)
|
|
|
|
|
|
|
|
|
|
|
|
|
(t
|
2k
|
-t
|
2n
|
)
|
|
|
|
|
|
c
|
|
|
|
|
2
|
|
|
|
|
|
|
qaerda c2= 29 kJ/kg∙K – havoning issiqlik sig'imi [20].
|
G2
|
|
|
|
9780.58
|
|
|
|
8.43
|
kg/soat
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
29(60-20)
|
|
|
Issiqlik almashtirgichning taxminiy tanlovi.
Biz issiqlik uzatish koeffitsientining taxminiy qiymatini havo-suyuqlik issiqlik uzatish holati uchun qabul qilamiz Kor = 25 Vt/m2∙K [20], keyin taxminiy issiqlik uzatish yuzasi:
Fop
|
|
|
Q
|
|
|
|
,
|
(53)
|
Kop
|
|
|
|
tChorshanba
|
|
bu erda Q - issiqlik oqimi, termal hisobdan, W Kor - issiqlik uzatish koeffitsienti, Vt/m2∙K
Fop
|
|
9780.58
|
1,95 m2
|
25200
|
|
|
|
Fop= 9780,58/∙25∙200 = 1,95 m2.
Biz issiqlik almashinuvi yuzasiga yaqin issiqlik almashtirgichni qabul qilamiz:
F =2m 2, korpus diametri bilan bitta o'tish D=159
n = 19 trubka 20 × 2 uzunligi l = 1 m [21].
Devordan havoga issiqlik uzatish koeffitsienti:
mmi
(54)
Qayerda2= 0,027 Vt/mK - havoning issiqlik o'tkazuvchanligi 40Nu bilan2- Havo uchun Nusselt mezoni.
Reynolds mezoni:
Re2= G2/[0,785dvn2] =0,43 /[0,7850,0181.8710-3] = 16790.
2=1,8710-3-40 da havoning dinamik yopishqoqligiBILAN
Harakat rejimi bu holda Nusselt mezoniga ko'ra turbulentdir:
Nu2= 0,021Re20.8Pr20.42(Pr2/Prst2)0,25
qaerda Pr2= 7.02 - havo uchun Prandtl mezoni 40S Biz birinchi taxminiy munosabat sifatida qabul qilamiz (Pr2/Prst2)0,25
Nu2= 0,021167900,87.020,43= 94.3.
2 94.3 0,027 141.45Vt/m2∙K0,018
Bitumdan devorga issiqlik uzatish koeffitsienti:
1 Nu11
dn
(55)
Qayerda1= 0,2 Vt/mK - bitumning issiqlik o'tkazuvchanligi, Nu1– Bitum uchun Nusselt mezoni. Reynolds mezoni:
Re1
|
G1 dn
|
,
|
(56)
|
S
|
mtr
|
|
|
|
1
|
|
|
qaerda Smtr= 0,005 m2- qismlar orasidagi oqimning ko'ndalang kesimi maydoni,1= 1.5910-3Pas – bitumning dinamik viskozitesi 240 daC [20].
Re1
|
0,560,02
|
=2521
|
|
0,0051.5910-3
|
Bunday holda, Nusselt mezoni:
Nu1= 0,24Re0,6Pr10.36(Pr1/Prst1),
qaerda Pr1= 8.8 - Bitum uchun Prandtl mezoni.
Birinchi taxmin sifatida biz munosabatni qabul qilamiz (Pr1/Prst1)0,25Nu1= 0,2425210,68.80,36= 55.2.
55.2 0,2 552 Vt/m2 ∙K
1 0,02
Devorning issiqlik qarshiligi:
|
|
|
st
|
r
|
r
|
|
|
|
|
|
st
|
|
|
|
1
|
2
|
(57)
Qayerdast= 0,002 m - quvur devorining qalinligi;
st= 17,5 Vt/mK - zanglamaydigan po'latdan issiqlik o'tkazuvchanligi;
1/r1=1/r2=2900 Vt/mK – neft mahsulotlari uchun devor ifloslantiruvchi moddalarning issiqlikka chidamliligi[1, bet. 354]
|
|
|
|
0,002
|
|
|
|
1
|
|
|
|
|
|
1
|
|
|
4.6
|
10
|
-4
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
m∙K/Vt
|
|
|
|
|
|
|
17.5
|
|
|
|
|
|
|
|
|
2900
|
|
|
|
|
|
|
|
|
2900
|
|
|
|
|
|
|
|
|
Issiqlik uzatish koeffitsienti:
|
|
|
|
TO
|
|
|
|
|
|
|
|
|
1
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
(58)
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1
|
|
|
|
|
|
|
1
|
|
|
|
|
|
|
|
|
|
|
(
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
)
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1
|
|
|
|
|
|
2
|
|
|
|
|
|
|
|
|
|
|
TO
|
|
|
|
|
|
|
|
|
|
|
|
|
1
|
|
|
|
|
|
|
|
|
|
|
|
106.6Vt/m2∙K
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1
|
|
|
4.610-4
|
|
|
|
|
|
|
1
|
|
|
(
|
|
|
|
|
|
|
|
)
|
|
|
|
|
552
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
141.45
|
|
|
|
|
|
|
Issiqlik uzatish yuzasi:
|
|
|
|
F
|
|
|
|
|
|
|
Q
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
(59)
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|