Page 119 - Process Equipment and Plant Design Principles and Practices by Subhabrata Ray Gargi Das

116 Chapter 4 Shell and tube heat exchanger

From Table 4.11, minimum number of six tie rods with minimum diameter of 10 mm is required.
The thickness of the flat channel cover t channel in mm is obtained from Eq. (4.33) as
p ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi p ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
D s C p design 489 0:25 7:8
þ 10 ¼ 17:2
t channel ¼ þ Corrosion allowance ¼
10 f all;stress 10 9:5
2
2
f all;stress ¼ allowable stress value in kgf/mm at design temperature (¼ 9.5 kg/mm , for plate
material as per IS 2002 Gr. I < 250 C), and C ¼ 0:25 as the cover is bolted with full faced gaskets.

Adopted standard plate thickness is 20 mm. Depth of pass partition grooves in channel cover is
5 mm and there should be a minimum thickness of 3 mm of base material.
Further mechanical detailing of the exchanger may be done referring to the code.

Nomenclature
2
A e Bundle cross flow area (m )
2
A o Heat transfer area, i.e., effective tube outside area (m )
B Baffle spacing (m)
C Gap between outer diameter of tubes perpendicular to flow direction (mm)

C p Specific heat capacity (W/kg C)
CL Fraction of shell cross-sectional area required to accommodate one tube ( )
CTP Factor to account for clearance required between shell and outermost tubes ( )
De Shell-side equivalent diameter defined in Eq. (4.12) (mm)
D h Hydraulic diameter (mm)
D i Inside diameter (mm)
D n Nozzle inside diameter (mm)
D o Tube outside diameter for unfinned tubes or root diameter in case of finned tubes (mm)
D s Shell inside diameter (mm)
f Fanning’s friction factor for flow condition as decided by Reynolds’ number ( )
2
f all;stress Allowable stress value in kgf/mm at design temperature
F T LMTD correction factor ( )
2
G Mass flux (kg/s m )
h f Fin height (mm)
h i Heat transfer coefficient inside tubes (W/m 2 C)
h o Shell-side heat transfer coefficient (W/m 2 C)
K c Loss coefficient associated with the flow area contraction ratio at inlet, b in ( )
K e Expansion loss coefficient based on flow area expansion ratio at exit, b e ( )
2
k w Tube material thermal conductivity (W/m K)
L Total tube length/length of core passage (m)
L e Net effective tube length available for contact by the shell-side fluid (m)
L IB Length of impingement baffle (mm)
L p Tube length per pass (m)
m Mass flow rate (subscript s for shell-side fluid and t for tube-side fluid, c for cold fluid
and h for hot fluid (kg/s)
n Number of shell passes ( )
N b Number of baffles ( )
N f Number of fins per mm ( )
N p Number of tube passes ( )