Heat Exchanger (E-2)
Heat Balance
T1 (360°F) ® T2 (275°F)
t2 (120°F) ¬ t1 (86°F)
Mass flow rate of oil = 0.59 Btu/lb°F
Heat duty, Q = 58060 ´ 0.59 ´ 85
= 2908224 Btu/hr
Mass flow rate of water = 29376 lbs/hr
Corrected LMTD = 182°F
Av. Temp. of oil = 318°F
Av. Temp. of water = 103°F
Assumed UD = 40 Btu/hr ft2 °F
Area required A = Q/UD LMTD= 2.98 ´ 106/40 ´ 182
= 400 ft2
No. of tubes required = 400/12 ´ 0.2618 = 127
Specification of Shell and tubes
Shell Side Tube Side
ID = 19.25 inch No. of tubes = 132
Baffle spacing = 12in Length = 12 ft
Passes = 1 Tube OD & BWG = 1 in, 12
Pitch = 1.25 in2
Calculation for heat transfer area
Shell Side, oil | Tube Side, Water | ||
D | 0.0825ft | D | 0.065 ft |
as | 0.3208 ft2 | a’t | 0.479 in2 |
Gs | W/as= 19756 lbft2 | a | 0.2196 ft2 |
NRe | 5610 | Gt | 133770 lb/hr ft2 |
IH | 40 | NRe | 4618 |
NPr | 2.9 | IH | 18 |
ho | 90.2 Btu/hr ft2 °F | NPr | 1.517 |
hi | 154 Btu/hr ft2°F | ||
hio | 121 Btu/hr ft2°F |
Uc calculated = 51.67 Btu/hr ft2°F
Area available = 132 ´ 12 ´ 0.2618 = 415ft2
UD calculated = 2.98 ´ 106 / 182 ´ 415 = 38.39 Btu/hr ft2 °F
Dirt factor, Rd = (UC-UD)/UC ´ UD = 0.006 °F ft2 hr/Btu
PRESSURE DROP CALCULATION
Shell Side, oil | Tube Side, Water | ||
NRe | 5610 | NRe | 4618 |
f | 0.0025 | f | 0.00035 |
s | 0.89 | s | 1 |
Ds | 1.6ft | Pt | 0.002Psi |
N+1 | 12L/B=12 | Pr | 0.02Psi |
DPs | 0.5Psi | DP | 0.022Psi |
Heat exchanger
Heat Balance
T1 (360°F) ® T2 (341°F)
t2 (120°F) ¬ t1 (77°F)
Mass flow rate of oil = 616906 lbs/hr
Sp heat of oil = 0.54 Btu/lb °F
Heat duty,Q = 6.21 ´ 106 Btu/hr
Mass flow rate of water = 144418 lbs/hr
Corrected LMTD = 252°F
Av. Temp. of oil = 351°F
Av. Temp. of water = 98.5°F
Assumed UD = 50 Btu/hr ft2 °F
No. of tubes required = 157
Specification of Shell and tubes
Shell Side Tube Side
ID = 21.25 inch No. of tubes = 166
Baffle spacing = 18in Length = 12 ft
Passes = 1 Tube OD & BWG = 1 in,12
Pitch = 1.25 in2
Calculation for heat transfer area
Shell Side, oil | Tube Side, Water | ||
D | 0.0825ft | D | 0.065 ft |
as | 0.531 ft2 | a’t | 0.479 in2 |
Gs | W/as= 1161781 lbft2 | a | 0.276 ft2 |
NRe | 44006 | Gt | 523256lb/hr ft2 |
IH | 130 | NRe | 1.8 ´ 104 |
NPr | 2.67 | IH | 68 |
ho | 269 Btu/hr ft2 °F | NPr | 1.72 |
hi | 663 Btu/hr ft2°F | ||
hio | 518 Btu/hr ft2°F |
Uc calculated = 177 Btu/hr ft2°F
Area available = 166 ´ 12 ´ 0.2618 = 521ft2
UD calculated = 47.2 Btu/hr ft2 °F
Dirt factor, Rd = (UC-UD)/UC ´ UD = 0.003 °F ft2 hr/Btu
PRESSURE DROP CALCULATION
Shell Side, oil | Tube Side, Water | ||
NRe | 44006 | NRe | 1.8´104 |
f | 0.0016 | f | 0.00023 |
s | 0.89 | S | 1 |
Ds | 1.77ft | Pt | 0.44Psi |
N+1 | 12L/B=8 | Pr | 0.096Psi |
DPs | 8.25Psi | DP | 0.7Psi |
E-4 Design
T1 (182°F) ® T2 (127°F)
t2 (122°F) ¬ t1 (77°F)
Wwater = 149280 lbs/hr
Wair = 729806 lbs/hr
Heat duty, Q = 8.2 ´ 106 Btu/hr
Approach temperature = 50°F
Cooling range = 55°F
Overall coefficient, UD = 80 Btu/hr ft2°F
Required surface = 210 ft2/(MM Btu/hr)
Total surface for heat transfer = 1724 ft2
Bay width = 16 ft
Tube length for 16 ft bay = 24 ft
Fanned section length / Bay Width = 1.5
Fan installed = 1
Plot area = 384 ft2
Total horsepower for fan = 28.8 h.p.
Remarks 1 fan is employed; 30 h.p. driver is used
E-5 Design
T1 (127°F) ® T2 (86°F)
t2 (122°F) ¬ t1 (77°F)
Wwater = 106630 lbs/hr
Wair = 388600 lbs/hr
Heat duty, Q = 4.37 ´ 106 Btu/hr
Approach temperature = 9°F
Cooling range = 55°F
Overall coefficient, UD = 80 Btu/hr ft2°F
Required surface = 210 ft2/(MM Btu/hr)
Total surface for heat transfer = 903 ft2
Bay width = 12 ft
Tube length for 16 ft bay = 16 ft
Fanned section length / Bay Width = 1.3
Fan installed = 1
Plot area = 192 ft2
Total horsepower for fan = 14.4h.p.
Remarks 1 fan is employed; 15 h.p. driver is used
NOMENCLATURE
as = Area of shell
a//t = Flow area
at = Flow area per tube
B = Baffle Spacing
C = Clearance b/w tubes
Cp = Specific Heat Capacity
D = Inside diameter of tubes
De = Equivalent diameter of shell
Ds = Inside diameter of shell
f= Friction Factor
Gt = Tube side mass velocity
Gs = Shell side mass velocity
hi , ho = Inside and Outside film coefficient
hio = Value of hi when referred to the tube ,OD,Btu/hr.ft2.oF
ID = Internal Diameter
L = Tube Length,ft
LMTD = Log Mean Temperature Difference
m= Mass flow rate n = Number of passes
OD = Outer Diameter
PT = Tube Pitch
DP, DPt, DPr = Total, tube, return pressure drop
DPs = Pressure drop of shell
Q = Heat Flow
Rd = Combined dirt factor
Re = Reynolds number, dimensionless
s= Specific Gravity
UC,UD = Clean and Design overall coefficient
w = Mass Flow Rate of water
m = Viscosity
f = Viscosity ratio, (m/mw) 0.14
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