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Fouling
Before After six months
Figure 2 . Well screens before and after vapor infusion .
The task of treating cooling water in an environment such as a heat exchanger necessitates a simple , easily integrated approach . Vapor infusion is just such an approach and can form high nanobubble concentrations . Vapor infusion uses various methods to form nanobubbles , including mechanical , physical , and chemical means . These simple infusion techniques include bubble shearing , microbubble creation and collapse and use of varied gases create bubble surfaces prone to shrinking , prevent dissolved oxygen mass transfer , and provide a chemical treatment . In 2005 , a test of the technology was planned at the request of an electronics manufacturing plant that had a geothermal system suffering from severe biofouling in exchanger and recipient well screens , resulting in significant back pressure . The supply well water contained high levels of mineral iron and iron-reducing bacteria which caused fouling within the exchanger and downstream well screens over 2000 feet away . After installation of an infusion system , the heat exchanger showed improved function and the back pressure was resolved in two months . The well screen fouling was resolved after six months of vapor infusion . Photos taken of the well screens prior to infusion indicated significant , gelatinous biofilms but , after infusion , only sand silt remained ( Figure 2 ). The well screens received only preinfused water from the exchanger and not direct infusion . This client went 16 years without needing to clean their exchanger . A further indication of downstream bubble interaction was provided during a US Navy trial . Naval Facilities Engineering Systems Command ( NAVFAC ) wanted to determine if vapor infusion could provide sustainable bubbles for downstream shipboard seawater piping systems . NAVFAC designed a proof-of-concept study which pumped seawater from the sea water surface off Kona , Hawaii . The test pipes were clear PVC and over twenty feet long . Normally , ambient air bubbles should have coalesced over this distance , providing little wall surface interaction . The researchers compared a timed iodine vapor infusion with a non-infused control . After 45 days , the biofouling within the two pipes containing titanium coupons ( as seen in Figures 3 and 4 ) are noticeably different indicating nanobubble formation . University evidence of nanobubble formation using vapor infusion treatment chemicals was provided by the Earthman Labs at the University of California ( UC ) Irvine , CA . [ 2 ] The purpose of the study was to determine if infusing iodine vapor into a fluid volume could create nanobubbles without the varied methods commonly used . Two infusion devices consisting of a simple ¼-in . OD tube and a custom injection quill were used to determine if microbubble size influenced nanobubble formation and their characteristics . After three-minutes of infusion , the fluids were left untouched for a period to indicate if any nanobubbles persevered . The infused fluids were analyzed using a NanoSight device by Malvern Panalytical . to determine the concentration density of nanoparticles within the solution .
Persistence
0.25-in . diffuser
48 hours Concentration 1.28 × ( 10 8 ) mL -1 Size
158 – 196 nm
Table 1 . NanoSight results after using an open-end ¼-in . OD tube to produce iodine vapor infused nanobubbles .
Figure 3 . Forty-five-days control . Figure 4 . Forty-five-days with vapor infusion . www . heat-exchanger-world . com Heat Exchanger World June 2024
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