Novel Methods to Mitigate Heat Exchanger Fouling

TECHNOLOGY AREA(S): Ground SeaOBJECTIVE: Develop fouling mitigation techniques to prolong performance of seawater heat exchangers.DESCRIPTION: Seawater heat exchangers are plagued by fouling, such as particulate and biological film formation, during operation. Fouling of heat exchangers is a serious and long-standing problem that can result in decreased heat transfer efficiency, higher resistance to fluid flow, increased energy consumption, decreased heat exchanger lifetime, and increased downtime necessary to replace or clean fouled parts. Biological fouling is the accumulation of microorganism, plants, algae or animals on the interior of the tube and is the type of fouling most experienced. Turf-like algae growths are increasingly found when operating in warm seawater environments. The Navy currently uses a combination of periodic chlorination and periodic seawater flush to mitigate fouling in titanium seawater heat exchangers. Seawater flushing at velocities of 3 m/s is sufficient to remove most particulates. However, electrolytic chlorinator systems used to remove biological fouling are expensive, difficult to maintain, and ineffective in warm water.This topic seeks new passive or active environmental-friendly fouling mitigation techniques that would prolong heat exchanger performance and availability. Potential solutions include, but are not limited to, active controls that could periodically scrub small groups of tubes using high flow rates; head re-design to eliminate flow dead zones; and the application of novel coatings on fouling-prone areas within heat exchanger to prevent adhesion of particles or microbes with minimum degradation in heat transfer.PHASE I: Develop concepts to mitigate biological fouling in seawater heat exchangers. Validate feasibility by modeling and subscale demonstration at seawater temperatures up to 38 C. Prepare a Phase II plan.PHASE II: Develop a prototype system capable of eliminating biological fouling in a representative titanium shell and tube heat exchanger sized for a 200 refrigeration ton chiller. Evaluate performance in a relevant seawater environment (warm water port). Validate and expand analytic models (developed in Phase I) that must comply with Navy's Hazardous Material Control and Management program.PHASE III: Develop final design and manufacturing plans using the knowledge gained during Phases I and II in order to support transition of system to Navy platforms. Ensure that the final system meets Navy-unique requirements, e.g., shock, vibration and EMI. Explore dual-use applications in seawater cooled power plants, as well as commercial marine vessels.KEYWORDS: Thermal Management, Heat Exchangers, Biofouling, CoatingsReferences:1. Satpathy K.K. et al. Biofouling and its control in seawater cooled power plant cooling water system - a review. Nuclear Power, IntechOpen, DOI: 10.5772/9912 (2010). https://www.researchgate.net/publication/221909115_Biofouling_and_its_Control_in_Seawater_Cooled_Power_Plant_Cooling_Water_System_-_A_Review 2. Fan, S. et al. A state-of-the-art review on passivation and biofouling of Ti and its alloys in marine environments. Journal of Materials Science & Technology 34, 2018, pp. 421 435,. https://www.sciencedirect.com/science/article/pii/S1005030217302840 3. Mamroth, A., Frank, M., Hollish, C., Brown, R. and Simpson, M.W. A Hybrid Marine Air Conditioning Plant Model for Condition-Based Maintenance Diagnostics. Proceedings of ASNE Advanced Machinery Technology Symposium (2020).4. Navy Safety and Occupational Health (SOH) Program Manual for Forces. OPNAVINST 5100.19F. https://www.secnav.navy.mil/doni/Directives/05000%20General%20Management%20Security%20and%20Safety%20Services/05-100%20Safety%20and%20Occupational%20Health%20Services/5100.19F.pdf