Abstract
Makai Ocean Engineering has been developing Thin Foil Heat Exchangers (TFHX) for use in seawater-refrigerant, air-water, and water-water applications. This report summarizes work performed between November 2024 – July 2025.
In this period, Makai’s efforts included improving TFHX fabrication and assembly methods, characterization of TFHX thermal performance, and investigation of biofouling mitigation methods.
TFHX Design and Fabrication Development
Makai investigated options to improve the assembly process and gained experience with installation and operation of the cassette design. Makai continued to explore options to increase the internal fluid flow rates to make the TFHX more competitive in applications that already use plate-and-frame heat exchangers.
TFHX Characterization and Model Development
Makai performance tested two 2-MWth, cassette-style seawater-ammonia TFHXs on the HX Test Facility. The condenser was tested in a horizontal counterflow configuration and the evaporator was tested in a vertical, cross-flow, falling film configuration. Evaporator performance met model predictions but the condenser underperformed, likely due to issues with assembly.
TFHX Prototype Construction and Demonstration
Makai developed several concept designs for an accessible seawater/seawater heat exchanger and selected one to proceed with construction. Makai also designed the test station (as part of the HX Test Facility) to prepare for demonstration and testing.
Long-Duration Biofouling and Intake Screen Testing
Makai continued the intake screen testing and concluded 3-mm plate spacing in-situ cleaning and baseline tests after 1 year. The cleaned unit had a 13% increase in pressure drop whereas the baseline unit had 400% increase in pressure drop. Makai developed a system to clean TFHX units with 2.12-mm plate spacings and began a new submerged test.