POWER February 2016 - 39

HEAT EXCHANGERS
7. Improved heat transfer. The corrugated pattern of the
plates promotes turbulent flow in the welded-plate heat exchanger
(PHE), even at low velocities. Courtesy: Tranter Inc.
core, which is composed of round or oblong chevron-type plates
welded into a cassette by porthole perimeter welds. Cassettes are
then placed together and perimeter welded to each other, producing
an accordion-like core that is highly tolerant of thermal expansion
(Figure 7).
The plate pack is inserted into a cylindrical shell. Flow diverters positioned
between the shell and the plate pack help direct flow through
the shell-side channels. End plates, nozzles, and top and bottom covers
are welded to the shell to form a high-integrity pressure vessel.
Tranter says the design has experienced an extremely low failure rate
because there are no gaskets to replace and the design has an optimal
stress-distributing shape. With no tubes to vibrate under flow conditions,
there is less stress induced on welds, baffles, and supports.
One of the most surprising differences between the PHE design
and a conventional shell-and-tube heat exchanger is the size
of the components required for comparable duty. In one waterwater
heat transfer application, it would have taken a shell-andtube
heat exchanger weighing seven tons with a 100-ft2
footprint
to replace a PHE that weighed less than a ton and needed only 8
ft2
of floor space (Figure 8). The result is less cost for material
and support structures.
The standard PHE is designed for pressures up to 1,450 psig
8. Compact and efficient. Compared to a conventional shelland-tube
heat exchanger, the PHE takes up less than a tenth of the
floor space. Courtesy: Tranter Inc.
and temperatures from -50F to 1,650F (extended range units are
also available). The design can accommodate phase changes on
either the plate or shell side of the heat exchanger. Some common
power industry applications include closed loop cooling exchangers,
lube oil coolers, gland steam condensers, low-pressure feedwater
heaters, blowdown heat recovery exchangers, condensers,
and evaporators. ■
-Aaron Larson is a POWER associate editor.
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transparent shell-and-tube exchanger that can be easily reconfigured
with different bundle layouts and baffle types, cuts, and spacing.
Another design that has been refined through years of research and
development is the shell-and-plate heat exchanger. Plano, Texas-based
Tranter Inc. claims that its welded-plate heat exchangers (PHEs) allow
high heat transfer rates under elevated process conditions in less
space and at lower cost than shell-and-tube heat exchangers.
The key feature of the PHE is the heat transfer element, or plate
February 2016 | POWER
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POWER February 2016

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