Construction Essays - Tube Pitch Shell

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Tube Pitch Shell


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

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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 =


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.


∆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.


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


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



(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


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.