Boiling Research Could Improve Power Plant Efficiency

Bryan Kilgore for Zondits, September 17, 2015. Image credit: kadufernandiz

Kripa Varanasa, an associate professor of mechanical engineering, is leading a team of researchers at Massachusetts Institute of Technology (MIT) working to improve industrial boiling to avoid or postpone the onset of critical heat flux conditions. Critical heat flux occurs when the bubbles and vapor generated through boiling linger close to the boiling surface for too long. The vapor limits heat transfer and can cause the boiling surface to heat up uncontrollably, potentially melting the metal surface. This can damage the boiler and it limits the safe operating temperature. Higher industrial boiler temperatures would allow for increased overall power plant efficiency. This is critical because 90% of electricity generation in the United States uses a steam boiling process.

The research revealed that at some point the textured surfaces will start to impede a boiling heat transfer process. A certain level of surface texturing does provide heat transfer benefits, but too much will prevent efficient removal of vapor from the surface. Researchers are working to determine the point of maximum benefit and to better understand the physics behind liquid flow and surface texture interactions.

Breakthrough in plant efficiency

Laboratory Talk, September 10, 2015

In its research, the MIT team looked at the causes of extreme heating on a surface when water boils – a phenomenon that can severely damage industrial boilers and disable entire facilities.

Cases of such extreme heating occur when critical heat flux’s thermal limit is exceeded, the researchers said.

According to the MIT team, understanding critical heat flux, and developing ways to prevent it, could be the catalyst for operating chemical facilities and power stations at higher temperatures while simultaneously making them more energy efficient.

“Roughly 85% of the worldwide installed base of electricity relies on steam power generators, and in the US it’s 90%,” said Kripa Varanasi, an associate professor mechanical engineering.

Read More