New concept to cool boiling surface may help prevent nuclear power plant accidents

October 01, 2018

A new University of Hawaii at Manoa study has produced a new technique involving heat that could help prevent nuclear power plant accidents.

Boiling is usually associated with heating, however, in many industrial applications associated with extremely hot components, such as nuclear power plants and metal casting, boiling is used as an effective cooling mechanism. This is due to "latent heat," the heat absorbed to change water into vapor, which removes a huge amount of heat from a hot surface.

There is a limit to the amount of heat that can be eliminated through boiling. Increasing this tolerable heat limit is important for many reasons, but especially for safety.

Sangwoo Shin, an assistant professor in mechanical engineering at the UH Manoa College of Engineering, has demonstrated a novel concept that overcomes the tolerable heat limit or what's known as the critical heat flux (CHF). He leads a research team that has come up with a new method that increased the CHF by 10 percent compared to approaches used in the past.

According to Shin, this is important because, if the surface is extremely hot, the water near the surface will quickly change into vapor, leaving no liquid to use for cooling the surface.

"The result of this failure of cooling leads to a meltdown of the heated surface, as witnessed from the disaster at the Fukushima nuclear power plant in 2011," explained Shin. The incident was prompted by the Tohoku earthquake that struck eastern Japan, which generated a tsunami and disabled the power and cooling systems of the plant's reactors. "In this regard, extensive efforts have been put into increasing the CHF," he said.

To date, one of the most effective ways of enhancing the CHF is by roughening the surface with nanostructures, specifically, nanowires. High surface roughness leads to an increased number of sites at which the bubbling occurs, thus resulting in enhanced CHF.

The study found that boiling heat transfer was much more favorable with a new concept that involves coating the hot surface using nanoscale bimorphs, a piece of long metal that can bend when exposed to heat due to thermal expansion.

The hot surface causes the bimorphs to deform spontaneously, which makes the surface condition to be more favorable for boiling.

Shin says future studies to further CHF enhancement can be expected by choosing the right geometry and material for the nano-bimorphs, which may contribute to developing energy-efficient technologies for extremely hot systems.
-end-
This new finding, a collaboration with researchers from Yonsei University and the University of California Riverside, was recently published in Nano Letters.

University of Hawaii at Manoa

Related Engineering Articles from Brightsurf:

Re-engineering antibodies for COVID-19
Catholic University of America researcher uses 'in silico' analysis to fast-track passive immunity

Next frontier in bacterial engineering
A new technique overcomes a serious hurdle in the field of bacterial design and engineering.

COVID-19 and the role of tissue engineering
Tissue engineering has a unique set of tools and technologies for developing preventive strategies, diagnostics, and treatments that can play an important role during the ongoing COVID-19 pandemic.

Engineering the meniscus
Damage to the meniscus is common, but there remains an unmet need for improved restorative therapies that can overcome poor healing in the avascular regions.

Artificially engineering the intestine
Short bowel syndrome is a debilitating condition with few treatment options, and these treatments have limited efficacy.

Reverse engineering the fireworks of life
An interdisciplinary team of Princeton researchers has successfully reverse engineered the components and sequence of events that lead to microtubule branching.

New method for engineering metabolic pathways
Two approaches provide a faster way to create enzymes and analyze their reactions, leading to the design of more complex molecules.

Engineering for high-speed devices
A research team from the University of Delaware has developed cutting-edge technology for photonics devices that could enable faster communications between phones and computers.

Breakthrough in blood vessel engineering
Growing functional blood vessel networks is no easy task. Previously, other groups have made networks that span millimeters in size.

Next-gen batteries possible with new engineering approach
Dramatically longer-lasting, faster-charging and safer lithium metal batteries may be possible, according to Penn State research, recently published in Nature Energy.

Read More: Engineering News and Engineering Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.