Current Navy ships make use of shell-and-tube heat exchangers, which can utilize seawater as a heat sink. This is advantageous since ships can easily pull in water, filter it, utilize the cooling capacity, then dump the water overboard. Utilizing seawater as a heat sink reduces logistical burden and allows for ships to not have to store additional refrigerant onboard. Unfortunately, seawater is teeming with marine life. Up to now, filtration, high velocity flushing, and chlorination of the heat exchanger has been used to clean and maintain the heat exchanger in situ with deep cleaning when the ship is in port. However, filtration does not filter out bacteria, which colonize on walls of the heat exchanger to form a biofilm. High velocity flushing asymptotes in effectiveness and cannot remove build ups. Chlorination is effective in cold water, but as seawater temperatures rise, it is becoming less effective. The lack of biocide allows the biofilm to mature and larger marine growth to attach, reducing heat exchanger efficiency. During Phase I, Reaction Systems, Inc (RSI) developed an environmentally responsible way to clean the inside of the heat exchanger that does not introduce pollution into the returned ocean water. RSI was able to achieve a combination of disinfection of the water and sanitization of the surface, inhibiting biofilm growth. In the Phase II work, RSI will mature the technology by experimenting in a representative geometry and with real seawater. At the end of the Phase II, the TRL will have gone from 2 to 5. In the Phase II Option, RSI will test in a warm water port, further raising the TRL to 6.
Benefit: The anticipated benefits of this technology are vast. The primary beneficiary would be the US Navy, which has over 480 active duty ships with 93 planned ships that could benefit from this cleaning system. For the US Navy, this technology can reduce manhours spent cleaning the heat exchanger in situ, increase the life of the heat exchanger, and prevent inefficiencies due to biofouling. However, there are other beneficiaries to this cleaning system. The system can be retrofitted into any existing seawater-based architecture. That means the 800+ Cutters the Coast Guard operates, and all commercial and private ships are a potential market. Furthermore, this technology can be adapted to any component utilizing seawater, including for oil rigs, seaside powerplants, and even deep-water-source air conditioning systems for buildings.
Keywords: Antifouling, Non-toxic, Biofilm removal, Biofouling, heat exchanger
