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Tube Pitch Shell
HEAT EXCHANGER SECOND PART:
The tube pitch is the sum of the diameters of the two tubes and clearance c'.
The shell side and bundle cross flow area
Where ID = inner diameter of shell
C' = bundle clearance
B = baffle spacing
PT = tube pitch
Mass velocity Gs = w/as lb/hr ft2 or kg/hr.m2
Get help with your essay from our expert essay writers...Where w = fluid flow rate
Shell side equivalent diameter
The shell equivalent diameter can be calculated using the flow area between axial direction to the tubes and the wetted perimeter of the tubes.
Shell side equivalent diameter for square pitch
De =
INSERT THE EQUATIONS
Where PT = tube pitch
do = tube outside diameter
de = equivalent diameter in
Mean temperature difference
For calculating the heat transfer area required for a given duty, mean temperature difference ∆Tm must be needed. This can be calculated from the temperature difference in the fluid inlet and outlet of the exchanger.
INSERT THE EQUATION
∆Tlm =
Where ∆Tlm = lag mean temperature difference
T1 = hot fluid temperature inlet
T2 = hot fluid temperature outlet
t1 = cold fluid temperature inlet
t2 = cold fluid temperature outlet
true temperature difference ∆Tm can be calculated from the logarithmic mean temperature by applying a temperature correction factor.
∆Tm = Ft ∆Tlm
Where ∆Tm = true temperature difference
Ft = the temperature correction factor
The correction factor is a function of the shell and tube fluid temperatures and the number of tube and shell passes. It is normally as a function of two dimensionless temperatures.
INSERT EQUATIONS
R= shell side fluid flow rate times the fluid mean specific heat, divided by the tube side fluid flow rate times the tube side fluid specific heat
S= measure of the temperature efficiency of the exchanger
Correction factor Ft
CONDENSORS
We can use the design of shell and tube exchangers for condensers. The construction and design of the shell and tube exchanger for condenser is similar but the baffle spacing is lengthier i.e; typically baffle spacing lB = inside diameter of the shell.
Using the design of shell and tube exchanger four kinds of condenser configurations can design.
1. Horizontal cooling medium in tubes and condensation in shell side
2. Horizontal cooling medium in shell side and condensation in tubes
3. Vertical with condensation in the shell
4. Vertical with condensation in tubes
Mostly in process industries for condensation prefers horizontal shell side and vertical tube side
We can find mean condensation film coefficient for a single tube is from
INSERT THE EQUATION
Where
(hc)1 = mean condensation film coefficient for single tube w/m2 ...c
KL = condensate thermal conductivity w/m ...c
ρL = condensate density kg/m3
ρV = vapour density kg/m3
μL = condensate viscosity Ns/m2
g = gravitational acceleration 9.81 m/s2
- = the tube loading the condensate flow per unit length of tube kg/m.s
The above equation is used for finding mean condensation film coefficient for dingle tube when condensation outside horizontal tubes.
Using the kerns methods we can find mean coefficient for a tube bundle
INSERT THE EQUATION
L = length of tube
Wc = total condense flow
Nt = total number of tubes in the bundle
Nr = average number of tubes in a vertical tube row.
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