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Fouling
Nanobubble vapor infusion for heat exchanger fouling prevention
US tonnes CO 2
/ hr
Vapor infusion is an antifouling technology that reduces fouling and carbon expression through creation of a chemically and mechanically induced nanobubble formation . This article reviews vapor infusion and nanobubble science , development , and commercial application .
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By Michael Radicone , HTRI
The issue Cooling water used in the heat exchange processes may contain dissolved , sedimentary , or planktonic fouling agents . They will attach to heat transfer surfaces , forming intrusive , insulating beds through adhesion and solidification that impede water flow and heat transfer . This type of fouling impacts the mechanical or electrical system associated with the heat exchanger . Responding to reduced heat transfer or elevated pressure drop often means compensatory action to increase water flow , which in turn necessitates additional energy draw that , through fuel burn , elicits elevated carbon presentation . Greenhouse gases including carbon dioxide , sulfur dioxide , and others are released into the atmosphere through energy generation . Higher greenhouse gas concentrations in the atmosphere capture solar energy and thus raise the earth ’ s temperature . Net Zero methods are intended to reduce greenhouse gas emissions from human activity . To achieve global Net Zero goals , companies need to reduce
CO 2 emissions , especially any “ low hanging fruit ” such as reducing energy waste by improving heat exchanger efficiency within their facilities . Furthermore , the potential non-environmental benefits derived from functional improvement , such as cost or labor savings , contribute to a better value proposition .
Increasing biofilm thickness produces additional CO 2 ( assuming thermal conductivity of biofilm = static water )
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Bioflim thickness , µ m
Figure 1 . Correlation between the biofilm thickness atmospheric release of CO 2 .
Heat exchangers are a vital component in most industrial process systems , and carbon expression associated with heat exchanger fouling could account for a significant amount of atmospheric discharge . Any achievable improvement could offer broad impactful environmental and energy saving benefits . Providing a sufficient water supply , without fouling , is key to this endeavor .
Fouling-greenhouse gas relationship Studies have shown that fouling in a heat exchanger leads to additional energy demands and is directly related to greenhouse gas emissions [ 1 ] , as indicated in Figure 1 , and potentially to other environmental consequences . The loss of heat recovery and the additional energy for pumping represent a loss of thermal efficiency . The increase in energy supply , whether created on site or drawn from a local utility , is through additional fuel burn .
Nanobubbles Nanobubbles are tiny vapor-filled structures with a diameter of less than about 1 µ m and are potentially 2500 times smaller than a single grain of sand . Tens of millions fit within a micro bubble and offer an extremely large surface area . They may exist either as surface nanobubbles or dispersed in bulk liquid . Fluid-borne nanobubbles have a very long life in water due to their neutral buoyancy and low-rise velocity , possibly persisting for more than two months . Their characteristics are due to strong surface charges , internal pressures , and surface tension . Nano bubbles undergo Brownian motion within a fluid which enables them to continuously stimulate physical , biological , and chemical interactions and allow for a long perseverance within a fluid . Nanobubbles have been shown to induce the removal of fouling mineral sites held together by minerals such as calcium carbonate and provide the cleaning of stainlesssteel surfaces . Nanobubbles were determined to alleviate and resolve pitting caused by sulfate-reducing bacteria with pipe sections and service water from the secondary cooling water system at Three Mile Island Nuclear Power Station . After eight months of exposure , the pipe samples were sectioned and examined to measure corrosion pit depth . The results revealed that the mean pit depth was approximately 50 % greater in the control pipe ( which did not receive nanobubbles ) than in the sample exposed to nanobubbles .
Vapor infusion nanobubble formation To generate nonspecific high-volume bulk fluid nanobubbles for use in large commercial applications such as antifouling in heat exchangers , various methods have been utilized . These include excessive energy and water required methods such as flow generators that use membranes , static mixing , swirling liquid flow and pressurized dissolution to create nanobubble emulsions of significant density .
26 Heat Exchanger World June 2024 www . heat-exchanger-world . com