{"id":3918,"date":"2015-04-09T10:55:25","date_gmt":"2015-04-09T10:55:25","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=3918"},"modified":"2015-04-09T10:57:15","modified_gmt":"2015-04-09T10:57:15","slug":"phase-change-heat-transfer-viruses-help-water-blow-off-steam-3x-faster","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/phase-change-heat-transfer-viruses-help-water-blow-off-steam-3x-faster\/","title":{"rendered":"Phase-change Heat Transfer: Viruses Help Water Blow off Steam 3X Faster"},"content":{"rendered":"
\"Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml\"<\/a>
Scanning electron microscope image of the one-micrometer thick nanocoatings on a silicon substrate<\/figcaption><\/figure>\n

Legions of viruses that infect the leaves of tobacco plants could be the key to making power plants safer, heating and cooling buildings more efficient and \u201creally kick-ass computers,\u201d or to the liquid cooling of high-powered electronic devices, like radar systems. These tiny protein bundles, which were once a threat to a staple cash crop of the nascent United States in the 1800s, are now helping researchers like Drexel University\u2019s Matthew McCarthy, Ph.D., better understand and enhance the processes of boiling and condensation.<\/p>\n

McCarthy\u2019s research focuses on phase-change heat transfer \u2014 the boiling, evaporation and condensation of fluids. These processes, which are ubiquitous in nature, have also become integral to the technologies that keep our society running. Steam turbines generate electricity in massive plants that power cities. Boiling water is a time-tested purification method that is still used to treat water supplies. And both heating and cooling processes are part of the systems that control our indoor climates on a daily basis. If McCarthy\u2019s work can make phase-change heat transfer even a little more efficient, its impact could be huge.<\/p>\n

\u201cEven slight improvements to technologies that are used so widely can be quite impactful,\u201d McCarthy said. \u201cPhase-change heat transfer plays an important role in everything from power generation to water purification, HVAC and electronics cooling. Increasing performance of these systems would translate to significant improvements in the way we produce, consume and conserve our energy and water resources.<\/p>\n

Better Boiling?<\/strong><\/h2>\n

To improve on something that nature has been doing since the beginning of time, and people have been refining for thousands of years, McCarthy\u2019s looking not at the liquid or the heat source, but at the surface that links them.<\/p>\n

In his\u00a0Multiscale Thermofluidics Lab<\/span><\/a>,<\/span> McCarthy and his team design, build and test surfaces that are becoming increasingly better at controlling the formation and removal of vapor bubbles during the boiling process, while also delaying the onset of and undesirable condition that engineers call \u201ccritical heat flux.\u201d<\/p>\n

\u201cCritical heat flux is essentially the failure of a surface during boiling, where the production of vapor cannot be balanced by replenishing liquid,\u201d McCarthy said. \u201cThe result is an uncontrollable and often dangerous increase in surface temperature. This failure can lead to the simple destruction of electronic components or, in power plant cooling applications, the catastrophic meltdown of a nuclear reactor.\u201d<\/p>\n

When a liquid reaches critical heat flux, a thin layer of vapor blankets the heat-transfer surface. This vapor insulates the liquid from the heat source, and it drastically reduces the surface\u2019s ability to dissipate heat to the liquid. This results in \u201cburnout,\u201d which means dangerous increases in surface temperature occur very rapidly. After critical heat flux and burnout occur, it is extremely difficult to re-wet the surface and reduce its temperature.<\/p>\n

McCarthy\u2019s goal is to create nanostructured coatings for the heat-transfer surfaces that can delay or prevent the vapor barrier from forming in the first place. The ideal structure for higher heat transfer during boiling, according to McCarthy, is one that draws in the liquid and quickly rewets when the water does transform into a vapor.<\/p>\n

A \u201cDri-Fit\u201d Boiling Surface<\/strong><\/h2>\n

\u201cThe only way to delay CHF is to keep the surface wet at higher and higher heat fluxes.\u201d McCarthy said.<\/p>\n

To keep the boiling surface wet, McCarthy\u2019s team is employing a technique that\u2019s more frequently used to keep athletes dry. Wicking, or capillary effect, is the secret behind the high performance and thermal apparel that draws moisture away from the body. This material, which keeps people cool during a workout or warm in the winter, can also keep a boiling surface wet \u2014 thus staving off critical heat flux.<\/p>\n

The trick to making a wicking, or hydrophilic, material is strategically increasing its surface area to draw the liquid down a path toward region of lower density. Sponges do this with their pores and air pockets. McCarthy\u2019s team is creating its own super-hydrophilic surfaces by coating them with thousands of nanostructure tendrils. This is where the viruses come in.<\/p>\n

Viral Building Blocks<\/strong><\/h2>\n

The tobacco mosaic virus is a simple virus consisting of a single strand of RNA surrounded by thousands of coat protein strands. It was the first virus ever to be identified, in 1930, and one of the most extensively studied \u2014 likely because they were destroying an important cash crop at the turn of the last century. Today, the pests have carved out a new niche: self-assembling scaffolding for building nanostructures.<\/p>\n

McCarthy has been directing minions of tobacco mosaic viruses since he was a post-doctoral researcher at the University of Maryland, when his lab used them for research on nanostructured battery electrodes. He now grows his own genetically modified strain of the virus on the tobacco plants in his lab.<\/p>\n

\u201cThe genetic mutation introduces chemical binding sites \u2014 like molecular hooks \u2014 on the outer surface of the viruses that allow them to attach to nearly any substrate we want to use,\u201d McCarthy said. \u201cThis includes stainless steel, aluminum, copper, gold, silicon, and a variety of different polymers. Because of this, we are able to do a rather broad array of testing on materials that are already in use in power plants and water treatment facilities today.\u201d<\/p>\n

To make a test surface, McCarthy pours a solution containing billions of viruses onto his selected substrate. The rod-shaped viruses attach to the surface, forming a bristly layer of nanostructures. The tiny forest is then coated with a thin shell of metal that rigidly attaches the nanostructures.<\/p>\n

Once coated, the viruses are rendered inert. What they\u2019ve left behind is a coating of evenly spaced tendrils \u2014 \u201cmetallic grass,\u201d as McCarthy calls it. This \u201cgrass\u201d creates a capillary effect, which allows the coating to wick liquids across it and keep them in contact with the heat-transfer surface.<\/p>\n

\u201cThis is quite an efficient technique for bio-templating nanostructures,\u201d McCarthy said. \u201cIt requires no electricity, power, heat or special equipment \u2014 just a series of solutions at room temperature. After the coating process is complete, the now-inert viruses are fully encased, resulting in a conformal coating of high-surface-area metallic nanostructures.\u201d<\/p>\n

Testing the Waters<\/strong><\/h2>\n

With help from the viral framework, McCarthy\u2019s lab can produce nanostructure-coated test surfaces of all shapes and sizes in a matter of hours. One \u201cbatch\u201d of McCarthy\u2019s tobacco mosaic viruses can quickly coat a surface and turn it into a forest of tendrils that are perfect for wicking water.<\/p>\n

\u201cThe nanostructures we build using the TMV act to stabilize the boiling process at large heat transfer rates,\u201d McCarthy said. \u201cThese coating essentially act like a sponge, when a vapor bubble forms on the surface, they wick liquid underneath it using capillary forces to delay the dry-out phenomena associated with critical heat flux. The result is a greater than three-times increase in the critical heat flux, which allows safe operation at higher and higher heat transfer rates.\u201d<\/p>\n

As part of his National Science Foundation CAREER award research, McCarthy\u2019s team will look at the performance of dozens of different surface configurations with variations that range from the spacing of the nanostructures, to the overall shape and the metallic coating.<\/p>\n

\u201cOur lab has the unique ability to quickly design and build structured surfaces, thanks to our TMV technique,\u201d McCarthy said. \u201cWe can also create surfaces that are extremely difficult, if not impossible, to do using other methods such as conformally coating complex microstructured surfaces and depositing nanostructures on low temperature materials. Because we can do this cheaply and relatively quickly, we can test numerous surfaces and make scientific conclusions based on large data sets.\u201d<\/p>\n

Preliminary results are already quite promising. The super-wicking surfaces have shown a 240-percent increase in critical heat flux, which means the maximum heat transfer rate achievable before critical heat flux occurs is more than three times as high as it was using the uncoated boiling surface.<\/p>\n

The \u201cmetallic grass\u201d coating also results in a tripling of the efficiency of the boiling process. So, if two pots of water \u2014 one with a nanostructure coating and one without \u2014 were heated to the same temperature, the pot coated with nanostructures would produce twice as much water vapor as the uncoated pot.<\/p>\n

\u201cIn addition to studying the fundamentals of boiling heat transfer and its enhancement, this technology could be applied to new heat exchanger designs and high-performance thermal management systems of the future,\u201d McCarthy said. \u201cIt could also be used to retrofit existing systems with self-assembled viral nanostructures \u2014 which could prove to be a cost-effective way to improve their efficiency.\u201d<\/p>\n

And, as McCarthy notes, a little improvement to the efficiency of something that\u2019s widely used goes a long way.<\/p>\n

Source: scientificcomputing<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Legions of viruses that infect the leaves of tobacco plants could be the key to making power plants safer, heating and cooling buildings more efficient and \u201creally kick-ass computers,\u201d or to the liquid cooling of high-powered electronic devices, like radar systems. These tiny protein bundles, which were once a threat to a staple cash crop […]<\/p>\n","protected":false},"author":6,"featured_media":3919,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-3918","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml-300x217.jpg",300,217,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",90,65,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",320,232,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",96,70,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/04\/Viruses_Help_Water_Blow_off_Steam_Three_Times_Faster_ml.jpg",150,109,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/3918","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=3918"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/3918\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/3919"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=3918"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=3918"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=3918"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}