ABSTRACT

This Small Business Technology Transfer Research (STTR) Phase I project aims to significantly enhance water condensation heat transfer through the application of patterned surface coatings. These patterned coatings are expected to reduce unnecessary energy consumption caused by film-wise condensation mechanisms, typical in modern condenser systems. Instead, the proposed surfaces promote sustained drop-wise condensation, a mechanism that is, according to theory, 10 times more energy efficient than film-wise condensation, thus leading to significant reductions in material and operating costs. State-of-the art commercial coatings that promote drop-wise condensation have limited operating lifetimes of only 100 h. Therefore, a durable coating that facilitates sustained operation for longer durations is highly desirable for commercial applications. The technology proposed in this grant application involves the manufacture of surfaces with patterned hydrophobic and hydrophilic regions through the deposition of a hydrophobic coating that can be thermally decomposed locally via a carbon dioxide laser affording spatial resolutions below 100 micrometers. The methods selected to manufacture, apply, and pattern the coatings are standard industrial large-scale processes and are amenable to scaling up. The patterned wettability coatings are anticipated to improve the energy efficiency of condensation surfaces by a factor of 2 - 4 times from the current state-of-the-art.

The broader impact/commercial potential of this project affects a number of large market segments that depend on condensation processes, from small household dehumidifiers and HVAC systems, to large scale desalination plants. Condensation is an extremely energy intensive process. Thus, any costeffective performance enhancement facilitates numerous applications, such as enhanced dehumidification, HVAC and atmospheric water generation. The dehumidifier market alone represents a global market of $7 billion. By incorporating NBD coatings into existing commercial units, energy costs may be reduced without compromising condensation output, thereby disrupting the market with new energy efficient devices. The proposed technology also has civilian, humanitarian and military applications because it recovers water from the natural humidity in the atmosphere in virtually any region of the world. It will enable the US to increase its national security by enabling efficient water harvesting, lend goodwill through support of humanitarian needs, improve our nation's economic competiveness, and ultimately bring more STEM jobs to America. Enhanced condensation can have a significant logistical impact for any remote operation worldwide where water is not readily accessible. Other uses can enable increased global sustainability for capturing potable water for human, animal and plant consumption.

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