How to Model a Shell and Tube Heat Exchanger

Learn how to model a shell and tube heat exchanger in this instructional tutorial video. A working model of a cross-flow, one pass shell and tube heat exchanger is demonstrated here. Using COMSOL Multiphysics and the Heat Transfer Module, you can analyze the design's heat transfer coefficient and the pressure drops in the tube and shell.

Download the Shell and Tube Heat Exchanger model documentation here: http://www.comsol.com/model/shell-and...

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Closed Caption:

shell and tube heat exchanger is often
found in refineries as well as other
large-scale plants there are several
design variations and operating
conditions that impact the optimal
performance of such devices for the
purpose of this example we will be
analyzing a straight cross-flow one pass
to heat exchanger with water flowing
through the tube side
are flowing through the shell site
in this example in order to save time
we'll skip the parameters geometry and
explicit definition section if you would
like more information on those topics
please go to the heat exchanger tutorial
found the model gallery
to import the preprocessed heat
exchanger model click view then open the
model library in the model library go to
heat transfer module then heat
exchangers and open the shell and tube
heat exchanger geometry . mph file once
the file is open we are ready to begin
defining the physics parameters and the
analysis
first to define the material right click
on materials and open the material
browser under the built-in tab choose
air and add the material to the model
similarly open the material browser and
add liquid water to the model to find
the water material by using the
selection list and choosing water domain
once again add a third material by
opening the material browser and adding
structural steel defined the walls of
the heat exchanger and steal by choosing
boundary from the geometric entity list
and then choosing walls from the
selections list
to assign the flow boundaries of the
model we will add inlet and outlet
conditions for the water and air flows
right click on non isothermal flow and
go to the turbulent flow tab and add a
boundary inlet from the boundary
selections list choose in that water in
the velocity is zero field enter the
water velocity as you underscore water
now right-click on inlet one and rename
it as inlet water
similarly add an outlet by
right-clicking on non isothermal flow
and going to turbulent flow and adding a
boundary condition outlet from the
boundary selection list choose outlet
water and from the boundary condition
list choose normal stress this implies
that the total stress in the tangential
direction to the boundary as well as the
pressure reference are set to zero
allowing the fluid to flow without any
impedance
now rename outlet one is outlet water
right-click non isothermal flow and that
another k epsilon turbulent inlet
from the selections list choose in the
air and in the velocity section change
air velocity u 0 to u air
then rename inlet to as in the air again
right-click on non isothermal flow and a
tacky excellent turban outlet
from the selection list choose outlet
air in normal stress as boundary
condition
rename outlet to this outlet air
let's add the symmetry conditions to the
flow by right-clicking on non isothermal
flow and going to turbulent flow key
epsilon and choosing symmetry flow from
the boundary selection list choose
symmetry
right-click non isothermal flow and
under turbulent flow k Absalon choose
interior wall
from the selection list choose laws as
the interior boundaries to define the
heat transfer conditions will define
temperature at the inlets and outflow at
the outlets similar to the flow we also
have to define the symmetry conditions
for the heat transfer in addition will
use highly conductive layer feature to
account for the heat conduction through
the shell right click on non isothermal
flow go to heat transfers and added
temperature boundary
from the Boundary selections list choose
inlet water in the temperature field
type in t underscore water
then rename temperature one as
temperature water
right click on non isothermal flow and
under heat transfer add an outflow
from the Boundary selections list choose
outlet water
then rename outflow one is outflow water
add another temperature
laundry by right-clicking on non
isothermal flow
from the Boundary selection list choose
in the air and in temperature field type
T underscore air rename temperature to
as temperature air
also add another outflow boundary by
right-clicking on non isothermal flow
change the boundary to outlet air
then rename outflow to as outflow air
now add a symmetry property to the heat
transfer equations by right-clicking on
non isothermal flow and under heat
transfer choose symmetry heat from the
boundary selections list choose symmetry
right-click on non isothermal flow and
go to heat transfer and choose the
boundary condition highly conductive
layer
from the selection
less shoes walls and change the layer
thickness 25 millimeters
now we will define modeling coupling
operators in order to evaluate the
equivalent heat transfer coefficient
right click on definitions and go to
model couplings and choose average
change the geometric entity to boundary
and from the boundaries list choose in
that water
one and rename it as average one in that
water
similarly add another average operator
by right-clicking on definitions
choose boundary as the geometric entity
in from the selections list choose inlet
air
rename average to as average to in the
air
now right
nations go to model couplings and select
integration choose boundary is the
geometric entity and select water air
walls as the boundary
rename integration one as integration
one water air walls
given the complexity of this model the
computation time can greatly varied
depending on the mesh size defined by
the user
it is important to balance between
accuracy and computational cost in order
to ensure the most accurate solution in
a timely manner for the purpose of this
example we will define a modified
physics induced extremely coarse mesh in
order to obtain a relatively quick
solution while still remaining accurate
in the mesh settings window change the
element size two extremely course then
right-click mesh one and select edit
physics induce sequence
click on free tetrahedral one then under
the scale geometry section set the
x-direction scale factor to 0.5 then
under the boundary layer OneNote select
boundary layer properties one and
defined number of boundaries as three
then click build off
once the mesh is built you're ready to
compute study one please note that it
takes about three hours to compute the
model with an average computer
containing 12 gigabytes of free memory
depending on the computational power of
your machine this time may vary
once the results are calculated expand
the wall resolution node and click on
surface one in the expression section
like replace expression then choose non
isothermal flow upside and select while
liftoff
quick plot to see the upside wall lift
off for the tubes from this graph you
can see where the most critical errors
in term of mesh resolutions are located
typically an acceptable wall lift off
should remain under ten percent of the
tube radius in this plot you can see
that most of the wall lift off remains
under ten percent which makes this mess
resolution sufficiently we find for the
purpose of this example now that we have
validated the model let us analyze the
temperature distribution along all of
the wall boundaries
under the datasets node with surface one
from the selection list choose walls as
the boundary
on the results expand temperature and
click on surface one then change the
default temperature unit two degrees c
click plot to view the temperature
distribution along the new surface in
order to create a 3d streamline view
illustrating the velocity and
temperature we will near the solution
obtained by the original half heat
exchanger geometry right click on data
sets go to more data sets and that a
mirror 3d from the plane list choosy
explains as the plane of symmetry
right-click on results and a 3d plot
group from the data set list choose
mirror 3d one
right click on 3d plot group for in a
stream line
in the points edit field under the
streamline positioning section type in a
hundred to find a number of streamlines
and apply then define the line type as
tube in order to make the coloring of
the velocity field illustrating the
temperature more visible right click on
streamline one and choose color
expression from the color table list
choose thermal right-click on 3d plot
group for and rename it as velocity
streamline this figure illustrates the
air flow as well as the water flow
through the heat exchanger the largely
different heat capacities between the
air and the water are clearly portrayed
in this plot as the temperature of the
air changes much more drastically than
that of the water when it flows through
the heat exchanger
now right-click on the right values and
not a globally evaluation using the
integration and average coupling
operators defined earlier type in the
following expression to define the heat
transfer coefficient here you can see
the global expressions embedded in the
terms for the power the area
in that hot temperature and in the cold
temperature
click evaluate to soften the heat
exchangers overall heat transfer
coefficient
right click on global evaluation one and
rename it as heat transfer coefficient
that is now analyze the average water
inlet pressure as well as the average
air in the pressure right click on Drive
values and go to average then select
surface average from the selection list
choose inlet water and in the expression
field enter p then click on the evaluate
button to see the average inlet water
pressure this result is equivalent to
the water pressure drop across the heat
exchanger as the outlet water pressure
is almost zero
right click on surface average one and
rename it as inlet pressure water
right click on the right values and add
another surface average
from the Boundary selection list choose
in the air and in the expression field
type in p
now click the evaluate button to see the
average in the air pressure
similarly this value is equivalent to
the air pressure drop across the heat
exchanger
right click on surface average two and
we named it as inlet pressure air
find this and similar models in the
model gallery at council calm / miles