Pat Grandelli, P.E. Steven Rizea, P.E. Michael Eldred Robert Loudon

OTEC Heat Exchangers: Performance and Power Output

for Historical and Modern Designs

Makai Ocean Engineering, Inc.

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Asia Pacific Clean Energy

Summit, OTEC Symposium

Honolulu, Hawaii September 2013

Heat Exchanger Attributes

•High heat transfer performance (U)

•Clean: Clog-free, no biofouling

•Corrosion: Lifetime

OTEC Heat Exchanger Development Focus

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•Cost: Materials & manufacturing

•Parasitic losses: Minimize flow & head

•Compactness: Manifolds, Area

Makai Ocean Engineering, Inc.

Initial Tests: 1978 - 79

Carnegie-Mellon Shell & Fluted Tube (Al)

Linde / Union Carbide Shell & Hi-Flux Tube (Ti) Plate Heat Exchanger (Ti) 3

Makai Ocean Engineering, Inc.

2nd Gen Tests: 1981

Johns Hopkins Folded Tube (Al)

Trane Brazed Aluminum Heat Exchanger #1

•By 1981, we learned cleanliness & biofouling are solvable. •Cost is the problem. Is aluminum the answer?

4 Makai Ocean Engineering, Inc.

3rd Gen Tests: 1981 - 84

Trane Brazed Aluminum Heat

Exchanger #2

•Corrosion & Fabrication •SW Flow & pressure ~30% less than CMU •Performance improved 6% vs. CMU •Gov’t funding ends

•BAHX2 is an improved OTEC Evaporator 5

Makai Ocean Engineering, Inc.

Recent Tests: 2012

BAHX3 is the result of OTEC plant system analysis.

L ifetime U (performance & parasitics) V alue (price & arrangement)

•BAHX3 has 2/3 of CMU flow, at same seawater head. •27% better U than CMU. • Extruded aluminum channels. • Vertical 5m tall. Compact.

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Makai Brazed Aluminum Heat

Exchanger #3

Makai Ocean Engineering, Inc.

Thank You References: • Avery, W.H. & Wu, C. Renewable Energy from the Ocean, A

Guide to OTEC. Oxford University Press, NY, 1994. • Constructability of extended surface heat exchangers for OTEC.

Proc. 8th Ocean Energy Conference. June 1981. • Makai Ocean Engineering, Chart Energy & Chemical Brazed

Aluminum Evaporator Testing Report, Aug 23, 2012. Unpublished.

• Panchal, CB. Heat transfer with Phase Change in Plate-Fin Heat Exchangers, Proc 22nd ASME-AICHE National Heat Transfer Conference, Niagara falls, NY, Aug 1984.

• Panchal, Hillis, et al. OTEC Performance tests of the Trane plate-fin heat exchanger. Argonne National laboratory report ANL/OTEC-PS-07. April 1981.

• Yung, Lorenz, et al. OTEC Performance tests of the Johns Hopkins University Applied Physics Laboratory Folded-Tube Heat Exchanger. Argonne National laboratory report ANL/OTEC-PS-09. August 1981.

Image citations: • Mini-OTEC: OTECnews.org • All other photos & graphs: Makai Ocean Engineering, Inc. • Trane Brazed Aluminum Heat Exchanger #1: Panchal, Hillis,

1981. • All other line art: Avery & Wu, 1994.

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Makai Ocean Engineering, Inc.

Pat.Grandelli@makai.com (1) 808-259-8871 www.makai.com Makai Ocean Engineering, Inc.