Improving Heat Exchanger Functionality with Nanobubble Technology to Achieve Net Zero Goals

Climate change is a critical environmental issue for this and future generations. Natural and human-induced activities have already warmed the global average surface temperature by 1.1°C. There is an international agreement that climate change requires an immediate response before the planet reaches a point after which it cannot recover. As the primary driver being a change in the earth’s atmosphere, it is vital that companies, countries, and individuals do whatever is possible to reduce this condition.

Part One of this two-part article examines the greenhouse gases affecting the planet, heat exchanger fundamentals, and the connection between heat exchanger fouling and its impact on the environment.

By Michael Radicone, CEO and Chief Science Officer of I2 Fluid Innovation, Inc.

Greenhouse gas (GHG) emissions include carbon monoxide, methane, sulfur dioxide, fluorinated gases, nitrous oxide, and others that are released into the atmosphere through both natural and industrial processes.¹

They are linked to environmental pollution and atmospheric temperature rise. Along with nitrogen, oxygen, helium, and other gases, they envelop the Earth as a blanket. GHG provides protection and predictable weather patterns by allowing ultraviolet and infrared wavelengths to warm the earth’s surface and then mediating its escape back into space. Human activities, primarily through the combustion of fossil fuels, have upset the balance of the natural system, allowing for an increase in atmospheric GHGs. Due to an abundance of these gases, the atmosphere can hold more heat, thus increasing the global temperature.

Carbon dioxide (CO₂) is a gas of great concern due to its abundance and robust emission profile when created through commercial activities during energy production. Increased CO₂ emissions have led to higher concentrations of it in the atmosphere. In 2021, CO₂ accounted for near 80% of all U.S. greenhouse gas emissions. Prior to expansive industrialization, and its compensatory rise in fossil fuel demand, CO₂, when released into the environment, was absorbed by the forests and the oceans. As GHG output has increased, the equilibrium between reabsorption and atmospheric presentation has fallen out of balance.

With the environment having reached and surpassed its limit for natural CO₂ absorption, Net Zero goals and methods are being adopted to help diminish industrial GHG expression.²

These methods encompass artificial reabsorption coupled with technological improvements intended to reduce industrial CO₂ expression. Achieving the desired Net Zero goals on an industrial and global scale will require both primary and supplemental technologies. Although large-scale commercial reductions are vital, applying innovative science may be the most difficult to implement due to technological adoption resistance and financial costs. It is apparent that all industries need to look at the means to reduce their energy waste through existing system improvement with methods that can be implemented quickly and without excessive costs. Typically, the energy savings and improvement in functionality should compensate for the integration costs, thus allowing for a net sum gain rather than expense.

Heat Exchangers Are Industry’s Low-Hanging Fruit

A heat exchanger is a device that is used to transfer heat between a process and a cooling fluid during an industrial application. The term “thermal manipulation” best describes what   heat exchanger does. Although simplistic in design, their operational condition can significantly impact the day-to-day energy consumption of an industrial process and its carbon footprint. It is not their function but rather their malfunction, due to processes such as fouling, that heat exchangers can affect GHG emissions and energy expenditure.

Heat exchangers are foundational devices found in large numbers in all industries, including nuclear power, chemical production, petroleum refining, and propulsion generation. Typically robust, they are designed to compensate for potential inefficiencies to minimize excessive downtime or diminished functionality. Exchanger parameters to be considered for optimum function are exchanger size, plate surface area, and, importantly, cooling water flow characteristics. Unfortunately, even though sufficient design margins are anticipated, certain conditions, such as cooling water fouling (as seen in Figure 1), can elicit increased energy draw and thus excessive GHGs. The results of this degrading functionality are expressed through reduced heat transference and increased back pressure within the cooling water system.

For a heat exchanger to function efficiently, it requires clean heat transfer surfaces and unimpeded cooling water flow. Fouling occurs when contaminants within the cooling water adhere and solidify on heat transfer surfaces and in flow spaces. This condition begins immediately after a clean heat exchanger is brought online. Although not immediately apparent, as foul formations increase in density or dimension, there is an ever-decreasing function expressed by the exchanger. Each exchanger requires a specified cooling water volume, speed, and pressure to ensure heat extraction. This is not achieved if there is impeded flow space or misdirection away from heat transfer surfaces.

Obstructions reduce flow volume which causes increased back pressure across the exchanger. Furthermore, on heat transfer surfaces, the foulants function as thermal insulators, reducing the transfer of heat from one fluid to another. Sensors will demand greater water flow from the cooling water pump as a response to a temperature and pressure rise. To compensate, the pump increases water output necessitating increased energy draw. This energy is typically from a source that uses fossil fuel combustion for electrical energy production. Even a small, incremental rise in pump demand due to foul formation can often translate to measurable increases in GHG generation (see Figure 2). There is an ever-increasing decline in function (and corresponding increase in energy draw) that continues until an acute condition, such as total malfunction, requires an emergency disassembly. Unfortunately, due to the importance of a heat exchanger within a process system, they are not readily taken offline to clean and are typically tolerated until and when an issue arises. if there is impeded flow space or misdirection away from heat transfer surfaces. Obstructions reduce flow volume which causes increased back pressure across the exchanger. Furthermore, on heat transfer surfaces, the foulants function as thermal insulators, reducing the transfer of heat from one fluid to another.

Sensors will demand greater water flow from the cooling water pump as a response to a temperature and pressure rise. To compensate, the pump increases water output necessitating increased energy draw. This energy is typically from a source that uses fossil fuel combustion for electrical energy production. Even a small, incremental rise in pump demand due to foul formation can often translate to measurable increases in GHG generation (see Figure 2). There is an ever-increasing decline in function (and corresponding increase in energy draw) that continues until an acute condition, such as total malfunction, requires an emergency disassembly. Unfortunately, due to the importance of a heat exchanger within a process system, they are not readily taken offline to clean and are typically tolerated until and when an issue arises.

The above graph is from one of the many papers^{3, 4} that have indicated the relationship between heat exchanger fouling and its environmental impact. The paper concluded the following:

• “…the presence of unwanted deposits on heat transfer surfaces in power station steam condensers can increase the discharge of greenhouse gases. The extent of the increase is of course dependent upon the thickness of the deposit.”
• “The loss of heat recovery and the additional energy for pumping represent a loss of thermal efficiency. When fuel combustion supplies energy, additional greenhouse gas emission will result.”

For decades, industry has borne the financial expense and challenges presented by heat exchanger fouling because of the difficulty of remediation or prevention. It was understood that there was a fiscal impact of maintenance, repair, excessive energy, and loss of process which could reach .25% of an industrialized country’s GNP due to fouling.⁵ These challenges were tolerated since the results of these inefficiencies were only felt by the facility. It was the advent of climate change and an understanding that each malfunctioning heat exchanger offers a compounding impact on environmental global events. It is now universally accepted that there is a need to reduce GHG expression from industrial process systems by utilizing a sustained method to prevent fouling in heat exchangers.

Part Two of this two-part article will explore nanobubbles and their capabilities, as well as the role heat exchangers play on Net Zero goals.

Author’s note:

As mentioned within the paper, global warming and carbon dioxide expressions have an insidious, generational impact. While researching and writing this paper it was vital that the younger generation have both input and review. I relied upon their passion and concerns to understand the urgency presented by global warming. For information regarding vapor infusion please reach out to the author.