Scientists have found a way to boil water faster, although they admit the discovery is unlikely to revolutionise tea-making.
The technology works by coating a heating element with a virus found on tobacco plants. The coating dramatically reduces the size and number of bubbles that form around the element as it gets warmer. Air pockets caused by bubbles temporarily insulate heating elements from the surrounding water, slowing down the transfer of heat.
A coating made from the tobacco virus tripled the efficiency of boiling water, scientists said, which could save vast quantities of energy in industrial power plants or large-scale electronic cooling systems.
“Even slight improvements to technologies that are used so widely can be quite impactful,” said Matthew McCarthy, an engineer at Drexel University in Pennsylvania.
Controlling the formation of bubbles would also help guard against a scenario called “critical heat flux” that is undesirable – sometimes disastrous – in industrial boilers. This happens when so many bubbles are forming that they merge into a blanket surrounding the element, meaning that it can no longer transfer heat to the water.
“What happens then is the dry surface gets hotter and hotter, like a pan on the stove without water in it,” said McCarthy. “This failure can lead to the simple destruction of electronic components, or in power plant cooling applications, the catastrophic meltdown of a nuclear reactor.”
To counteract this effect, scientists have been attempting to develop surfaces that repel bubbles and keep the boiling surface wet. McCarthy’s team has identified tobacco mosaic virus, which is roughly pencil-shaped, as the perfect structure for wicking moisture downwards towards a surface.
The team has developed a genetically modified strain of the virus, with “molecular hooks” allowing it to adhere to nearly any surface. The researchers grow tobacco plants in the lab and infect them with the modified tobacco mosaic virus. “When the plants are really sick, we put them in the blender and you get a sort of green soup,” said McCarthy.
After several rounds of centrifuging and chemical separation, which takes two days, the scientists are left with a perfectly clear solution of concentrated virus. When poured over a surface, the virus self-assembles into a layer of nano-tendrils, each pointing upward like a blade of grass.
The surface is then covered with a microscopically thin layer of nickel, rendering the virus inert. The remaining “metallic grass” wicks liquids across the surface, allowing the water and element to remain in contact.
In tests, the coating has been shown to more than triple the heat transfer rate, depending on the surface to which it is applied.
The “metallic grass” coating resulted in the boiling process occurring three times more efficiently. So if two pots of water – one with the tobacco coating, one without – were heated to the same temperature, the coated pot would produce twice as much water vapour.
In a system designed to cool down a silicon electronic part, the coating almost tripled the temperature that the silicon could reach before critical heat flux occurred.
“In the future this could be used in nuclear power stations, really kick-ass computers or for the liquid cooling of high-powered electronic devices like radar systems,” said McCarthy.
Source: psfk.comAdded: 30 March 2015