This document provides tips and advice for selecting the appropriate heat exchanger for applications involving fluids with solids or high viscosity. It discusses common mistakes made in plate heat exchanger calculations and selections. Key recommendations include carefully considering nozzle sizing, fouling factors, plate pack size for maintenance, channel sizing for solids handling, pressure drop, materials selection, and gasket compatibility. Various heat exchanger types are compared for applications like slurries, and plate and frame exchangers are noted to be prone to clogging. The author provides experience in industrial heat transfer applications and consulting.

1. By Giuseppe Tommasone
Tips & Tricks
Heat Transfer Specialist
Heat Transfer

2. Contents
Heat Transfer Tips & Tricks
2
3
4
10
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Heat Transfer Specialist
10 Big Mistakes to avoid in Plate Heat
Exchanger calculation and material
selection
Which is the right Heat Exchanger for slurry,
high viscosity fluids containing solids?
Heat Transfer Experience

3. 3Heat Transfer Tips & Tricks
Heat Transfer Specialist
People like to buy, but are wary of sellers
You will surely come across Agent saying: "I deal with industrial components:
pumps, heat exchangers, valves and others ...".
Or Sales Engineer with one product to sell, not hesitating to push it even when
it is unsuitable
Hence the need for a new profile: the Heat Transfer Specialist.
Working exclusively in the Heat Exchange with a portfolio of dedicated
products without being tied to one type or another for bonds of exclusivity or
convenience.
With experience in the
installation sector borrowed
the Heat Transfer Specialist
can offer the customer a free
consultation (being paid by
manufacturers) with a view
of the whole project and
proposing the heat
exchanger more suited to
client’s needs
Strategic Consulting, including Business plan & Sales strategy development
Set up Heat Transfer products portfolio including Plate Heat Exchangers
(PFHE), Welded units (PSHE & WPHE) Spiral (SHE) Shell & Tube Heat
Exchangers (STHE) in different materials (Steel, Titanium, Tantalum,
Graphite and SiC) and Air-cooled Heat Exchangers.

4. 4Heat Transfer Tips & Tricks
in Plate Heat Exchanger calculation and material selection
In the recent years use of Plate Heat Exchangers increased
more than other type, therefore it's time to focus on mistakes to
avoid in calculation and material selection.
#1 Selection of connection size: typical nozzle velocity with
water is 5.5 m/s. Major part of PHE design software switches to
larger size if it is higher.
Standard velocity in piping is 2-2.5 m/s so that size of
connections is normally smaller and conic reductions are often
required. Don't select automatically PHE with connections same
size of piping: double check velocity in nozzles!
#2 Fouling Factor has been topic of discussion since years. PHE
FF must be 1/10 of Shell&Tube HEX FF as finally API 662
recommended. There is confusion among process engineers on FF
to be used in PHE and often EPC Contractors data sheets are
mentioning FF for S&T HE's.
4
10 Big Mistakes to avoid

5. 5
#3 Plate pack
size must be
considered from
maintenance
standpoint. Many
times to reduce
impact cost of large
frames, selection is a
PHE with plates pack
of 400 plates... easy
to sell not to open
and close!
Investigations demonstrated that
these values are not giving good
results in PHE since they often results
in oversized units with premature
fouling due to reduced velocity and
turbulence.
#4 Diameter of channel
plate required is often
underestimated. Of course
pressing depth of 2.2 mm is
more efficient than a 4.4 mm,
but if application is Oil & Gas in
a refinery in the Middle East
long life of PHE is a priority.
If solids or fibers are
present, maybe a free flow
plate is required channel 11 mm
Heat Transfer Tips & Tricks

6. 6
#5 Pressure drop is a driving force in PHE's creating turbulence to
get high U value. In calculation DP can dramatically change Heat
Transfer Area required.
Furthermore Process Engineers specified sometimes DP for S&T
HE's while typical DP in PHE is 0.7 bar.
Before deliver calculation double check if DP could be increased!
#6 Plate material selection is related to fluids involved. Stainless
steel is common material with water, but often Chloride level ppm is
underestimated
Heat Transfer Tips & Tricks
316L is not required in PHE because there are no welding's, but
316 instead of 304 can be useful in many applications. Brackish
water can require 254 SMO while sea water requires Titanium!

7. 7
#7 Gasket material is a weak point of PHE especially in case of
multipurpose use (like Pharmaceutical). Try to find a gasket material
suitable for different fluids is not so easy...
Wide range of materials is available Viton® Extreme, Aflas® TFE/P,
Viton® FKM, EPDM P.C., Buna-n, Silicone, NBR etc. but if you are in
trouble don't hesitate to select a semiwelded SPHE or fully welded
WPHE!
#8 Heat Recovery is one of the main reason to select a PHE rather
than other type of Heat Exchangers: countercurrent flow, LMTD=1
possible etc.
The LMTD is defined by the logarithmic mean as follows:
Heat Transfer Tips & Tricks
where ΔT is the temperature difference between the two streams at
end A, and ΔT is the temperature difference between the two
streams at end B. With this definition, the LMTD can be used to find
the exchanged heat in heat exchanger:

8. 8
Where Q is the exchanged heat duty (in watts), U is the heat transfer
coefficient (in watts per kelvin per square meter) and Ar is the
exchange area.
If duty is not District Cooling, industrial applications cost/benefit
better ratio in PHE is usually when LMTD is equal to 5.
Therefore if Process Engineer is asking for LMTD 3 show always
LMTD 5 option: Capex will result more convenient!
#9 Plate Pack mixing: with different chevron angle required
thermal length can be achieved (NTU) with consequent minor Heat
Transfer Area
Heat Transfer Tips & Tricks

9. 9
This is good for calculation...what about maintenance ? How plate
assembly will be correct in field if mixing is 72/28? Double check
increase of HTA in case of 100% plate H theta or L theta and 50/50 (M
channel). Maintenance Manager will be happy and will spread idea that
your PHE's are easy to assembly....
#10 Pressure Vessel Code in Oil & Gas application typical
requirement is ASME VIII Div.1 with U stamp and nozzle load calculation
according to API 662 table 2 severe conditions. In PHE design this
include extra costs for material (SA-516 Gr.70 for frame, SA-193 Gr.B7
for bolts, SA-194 Gr. 2H for nuts etc.) even if you mentioned according
to ASME VIII Div. without U stamp.
Heat Transfer Tips & Tricks
Verify on data sheets required code, otherwise you will in trouble!
Taking into consideration these 10 Big Mistakes to avoid you will be
ready to design every kind of Plate Heat Exchangers....good
calculations!

10. 10Heat Transfer Tips & Tricks
Which is the right Heat
Exchanger for slurry, high
viscosity fluids containing solids?
Several Heat Transfer applications are involving fluids with fibers (textile),
solids (PVC granules, antibiotic broths), high viscosity (visbreaking, tomato
juice,) or all of them (waste water treatment, anaerobic digestor, slurry)
Selection of proper Heat
Exchanger is always a trade
off: higher performance but
shorter operational life
because of fouling or wide
gap channel for longer
operating cycle but poor
thermal performance.
Corrugated Tube & Tube HE was first choice in Food & Dairy

11. 11Heat Transfer Tips & Tricks
Then Shell&Tube HE with large tube diameter
Later on wide gap Plate & Frame HE: compromise with channel up to 12 mm
reasonable K value and fully cleanable feature
In Petrochemicals a valid alternative to Shell & Tube is Spiral
Even though in multi pass heat
exchangers clogging redirects the flow
through the open channels, the channel
design in the SPHE reduces bypassing
through the velocity in the channel spiral
that increases until deposits are eliminated

12. 12Heat Transfer Tips & Tricks
Welded Plate Heat Exchangers WPHE Bloc type with wide gap channel
started to be used for solid waste water treatment
Choice is depending by applications: in Food & Dairy Tube in Tube is widely
used for sanitary hygienic conditions. In Oil & Gas Spiral & Welded Bloc Type
are best selection due to heavy conditions (high pressure) while in Biogas &
Waste Water Treatment Spiral & Tube in Tube are the big player.
Plate & Frame HE even with wide gap channel didn't find wide range of
applications because of tendency to clogging in relatively short time.

13. 13Heat Transfer Tips & Tricks
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Heat Transfer Experience of Author

14. 14Heat Transfer Tips & Tricks
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Heat Transfer Experience of Author

15. 15Heat Transfer Tips & Tricks
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Heat Transfer Experience of Author