112

13. COOLER-01 (C-01)

Fungsi : Untuk mendinginkan produk R-03
Tipe : Shell and Tube Heat Exchanger
Gambar :
Aliran inlet
Shell
Tube

Rear End
Head
Aliran outlet
Water in

Fluida Panas : Aliran Keluar R-03

W = 135.286,29 kg/hr = 298.254,87 lb/hr
T1 = 320oC = 608 oF
T2 = 220oC = 428 oF
Fluida Dingin : Air
w = 309.949,92 kg/hr = 683.321,80 lb/hr
t1 = 28oC = 82,4 oF
t2 = 50oC = 122,4 oF
Perhitungan design sesuai dengan literatur pada buku Donald Q. Kern
(1965).
1. Beban Panas C-02
Q = 53.983.202,14 kJ/hr
= 51.166.952,47 Btu/hr
2. LMTD
Fluida Panas (oF) Fluida Dingin (oF) Selisih
608 Suhu tinggi 122,4 486
428 Suhu rendah 82,4 345,6
Selisih 140,40

t 2  t1
LMTD =
ln (t 2 / t1 )
 113

= 411,82 oF
Ft =1 (Fig.18, Kern)
t = 411,82 oF
3. Temperatur Rata-rata
T1  T 2
Tavg =
2
= 518 oF
t1  t 2
tavg =
2
= 102,20 oF
4. Menentukan luas daerah perpindahan panas
Asumsi UD = 150 Btu/hr.ft2.oF (Tabel 8, Kern)
Q
A =
U D . t

= 51.166.952,47 ft2
150  411,82

= 828,31 ft2
Karena A > 200 ft2, maka digunakan Shell & Tube Heat Exchanger
5. Spesifikasi tube dan shell
 Tube Side
Panjang tube (L) = 18 ft
Outside Diameter (OD) = 0,75 in
BWG = 18
Pass =1
a” = 0,1963 ft2/lin ft
Jumlah tube, Nt = A
828,31 ft2
Lx0,1963
= 18 a"
= 234,42
Dari tabel.9 Kern, didapat nilai yang mendekati Nt perhitungan adalah
Nt = 239
 Corrected Coefficient, UD
 114

A = Nt x L x a''
= 239 x 18 ft x 0,1963 ft2
= 844,48
Q
UD =
U D . t

= 147,13
karena nilai Ud perhitungan mendekati nilai Ud asumsi, maka data untuk
shell :
Shell = Air
ID = 17,25 inch (Tabel 9, Kern)
Baffle Space (B = ID/2) = 8,625 inch
Pass =1
Pt = 0,938 in triangular pitch
6. Perhitungan desain bagian tube
 Flow Area/tube, a’t
a’t = 0,334 in2 (Tabel 10, Kern)
Nt  a ' t
at =
144  n
239  0,334
=
144  1
= 0,55 ft2
 Laju Alir, Gt
Gt = W/at
298.254,87
= 0,55

= 538.028,98 lb/hr.ft2
 Bilangan Reynold, Ret
μ = 0,018 cp = 0,044 lb/ft hr
ID = 0,632 inch = 0,053 ft (Tabel 10, Kern)
Ret = ID.Gt/ μ
0,053  538.028,98
= 0,044
 115

= 639.845,39
Dengan L/D = 341,77 diperoleh
Jh = 1.000 (Fig.24, Kern)
 Nilai hi
CP = 8,140 Btu/lb.oF
k = 0,006 Btu/hr ft.oF
Prandl Number (Pr)

 c.  = 57,22
 
 k 

1/ 3 0,14
 k   Cp     
hi  J H      
 D  k   w 
0 ,14
  
Koreksi viskositas diabaikan, karena 
 
 =1
 w 

 0,006 
   57,22
1/ 3
hi = 1.000 
 0,053 

= 460,33 Btu/hr ft2 oF

hio = hi x ID/OD
= 387,90 Btu/hr.ft2.oF
7. Perhitungan desain bagian shell
ID = Diameter dalam shell = 17,25 in
B = Baffle spacing = 8,625 in
Pt = tube pitch = 0,9375 in
C’ = Clearance = Pt – OD
= 0,9375 – 0,75
= 0,188 in
 Flow Area, as
as = ID x C’B/144 Pt
17,25  0,188  8,625
= 144  0,188

= 0,207 ft2
 Laju Alir, Gs
 116

Gs = w/as
683.321,80
= 0,207

= 3.306.812,50 lb/hr.ft2
 Bilangan Reynold, Res
de = 0,55 in (Fiq.28 Kern)

De (Equivalent diameter) = 0,046 ft

μ = 0,677 cp = 1,637 lb/ft hr
GS De
Res =

3.306.812,50 x 0,046
= 1,637

= 92.567,65
Maka:
jH = 200 (Fig.28, Kern)
 Nilai ho
Cp = 17,98 Btu/lb.oF
k = 0,36 Btu/hr ft.oF
Prandl Number (Pr)
1
 Cp.  3
= 816,25
 
 k 

Koreksi viskositas diabaikan karena tidak significant, maka diperoleh :

ho = jH . (k/De). (Cpμ/k)1/3\
0,36
= 200 x 0,046 x816,25

= 1.470,87 Btu / hr ft2 oF

8. Clean Overall Coefficient, UC

hio  ho
UC =
hio  ho

= 306,95 Btu/hr.ft2.oF
 117

9. Dirt Factor, Rd
U C U D
Rd =
U C U D
= 0,004 hr.ft2.oF/Btu
10. Pressure drop
 Bagian tube
Untuk NRe = 639.845,39
Faktor friksi = 9 x 10-5 (Fig 26, Kern)
s = 0,841
f Gt 2 L n
ΔPt =
5, 22 x 10 10 x De s  t

= 0,22323 psi
V2 / 2g = 0,04 (Fig 27, Kern)
ΔPr = ( 4n/s ) ( V2/2g )
= 0,190 Psi
ΔPT = ΔPt + ΔPr
= 0,414 psi
 Shell Side
Res = 92.567,65
f = 0,000005 (Fig.29, Kern)
N+1 = 12 L / B = 300,52
Ds = 1,438 ft
s =1
fGs 2 Ds( N  1)
ΔPs =
5,22  1010 Des s

= 9,87 psi
 118

IDENTIFIKASI
Nama Alat Cooler-01
Kode Alat C-01
Jumlah 1 buah
Operasi Kontinyu
Fungsi Menurunkan temperatur keluaran R-03

DATA DESAIN
Tipe Shell and Tube Heat Exchanger
Bahan Konstruksi Carbon Steel
Tube Side Shell Side
Jumlah 239 ID 17,25 in
Panjang 18 ft Baffle Space 8,625 in
OD 0,75 in
BWG 18
Pitch 15/16 in triangular pitch
Pass 1 Pass 1
Pt 0,414 psi Ps 9,87 psi

Dirt Factor 0,004