Chemical Engineering July 2022 - 39

* Compressed-air cooling
* Water or glycol cooling
* Heating and air conditioning
* Process heating and cooling
* Air-cooled process equipment
* Energy and solvent recovery
* Combustion air preheating
* Fluegas reheating
FIGURE 4. This design also utilizes a motor-andfan
assembly, but instead of tubes, corrugated
plates and fins are added to a brazed-composite
core, to create alternating air and fluid passages
heat-transfer rates translate to compact
designs. Because of the rigid
brazed alloy construction, temperature
differential between the two
fluids should be considered and is
typically limited to 200°F.
Typical applications include:
* Units that vaporize and condense
refrigerants
* Oil heating or cooling
* Applications requiring high alloys
* Heat-recovery applications
* Brine exchangers
* Applications involving liquid ammonia,
chlorine solutions, alcohols
or acids
Tube and continuous-fin air-cooled
exchangers. In the tube-and-fin aircooled
exchanger, a motor and fan
assembly forces ambient air over a
series of tubes, to cool or condense
the process fluids carried within. The
tubes are typically assembled in a
coiled configuration (Figure 3).
Air is readily available, but it is a
relatively poor heat-transfer medium.
Use of air-cooled heat exchangers
can greatly help eliminate the use of
valuable cooling-water supplies. To
increase the heat transfer rates of
the system, the tubes in air-cooled
exchangers are typically given fins,
which extend the surface area and
increase heat transfer.
The diameter and materials specified
for the tubes and fins depend on system
requirements. The fins are commonly
made from aluminum or copper
but may be fabricated of stainless or
carbon steel. Tubes are generally copper,
but can be made from almost any
material, and they typically range in
size from 3/8- to 1-in. outer diameter.
Typical applications include:
* Oil cooling
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Aluminum-bar and plate aircooled
exchangers. Similar to the
tube and continuous-fin design, this
design also utilizes a motor-and-fan
assembly, but instead of tubes, corrugated
plates and fins are added to
a brazed-composite core, to create
alternating air and fluid passages
(Figure 4). This compact, lightweight
design is considered the most costeffective
air-cooled unit available.
Turbulence created in the fluid channels
boosts efficiency and reduces
required size and surface area. Typical
applications include:
* Cooling lubrication oil for power
equipment
* Cooling fluids for hydraulic
equipment
* Cooling gearbox fluids
Concluding remarks
Clearly, for most applications and
heat exchanger types, there are a
multitude
of
choices and options
available. These guidelines should
provide a basis for comparison. No
matter what configuration is ultimately
implemented, the emphasis on clean,
efficient heat recovery ensures that
the heat exchanger will remain one of
the most critical components in the
manufacturing process.
n
Edited by Gerald Ondrey
Authors
John Boyer is the Heat Transfer
Commercial
Team manager at
Xylem Inc. (1 International Drive,
Rye Brook, N.Y. 10573; Phone:
716-303-6179;
Email:
john.
boyer@xylem.com). He has additionally
held roles in application
engineering,
management,
product/market
engineering and
general management. Boyer holds
a B.S.Ch.E. from the State University of New York at Buffalo
and Six Sigma Green Belt Certification, Lean, from
the University of Michigan College of Engineering.
Jim Klimek is the Heat Transfer
Global Product manager at Xylem
Inc. (Same address as above;
Phone: 716-862-4118; Email: jim.
klimek@xylem.com). He has additionally
held roles in application
engineering and product and application-engineering
management.
He holds a B.S.Ch.E. from the State
University of New York at Buffalo.
JULY 2022
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