Featured Research

from universities, journals, and other organizations

When The Heat Is On, Droplets, Particles In A Fluid Ride On A Cushion Of Vapor -- And Never Touch

Date:
March 29, 2006
Source:
Ohio State University
Summary:
When a tiny droplet of cold fluid mixes with a high-temperature solid particle, a vapor layer forms between them, and they never actually touch. Ohio State University researchers have performed the first accurate computer simulation of this small-scale phenomenon. Ultimately, this knowledge could enable engineers to boost the efficiency of chemical plants, power plants, and oil refineries, or any place where hot particles and cold fluid mix.

When a tiny droplet of cold fluid mixes with a high-temperature solid particle, a vapor layer forms between them, and they never actually touch. Ohio State University researchers have performed the first accurate computer simulation of this small-scale phenomenon.

Ultimately, this knowledge could enable engineers to boost the efficiency of chemical plants, power plants, and oil refineries, or any place where hot particles and cold fluid mix.

The find contributes to the fundamental understanding of a decades-old problem, explained L.S. Fan, a Distinguished University Professor and the John C. Easton Professor of Engineering in the Department of Chemical and Biomolecular Engineering at Ohio State.

Fan described his findings at the national meeting of the American Chemical Society on March 28, as he received the E.V. Murphree Award in Industrial and Engineering Chemistry.

In the 1950s, scientists who re-created industrial chemical conditions in the lab noticed something interesting about the way two objects collide. When a flat solid surface is much hotter than a liquid droplet, the droplet never makes direct contact with the solid surface. The droplet dances around on the hot surface without touching it.

Fan likened the effect to what happens when water hits the surface of a hot cooking pan.

"The water sizzles and dances around," he said. "It's the same for droplets in contact with spherical particles in a chemical reactor. But then the question becomes, is the heat effectively transferred during the contact? And it turns out that only a very small amount of the heat is transferred due to a very short contact time."

Though scientists knew of this phenomenon for decades, they were not exactly sure how it happened. The technology needed to answer the question -- specifically, the numerical simulation required to produce highly detailed three-dimensional characteristics of the process -– were not attempted until recently.

Fan and his team derived equations to explain how heat travels between separated surfaces. Then they compared three-dimensional supercomputer simulations based on their equations to experiments on actual collisions in the laboratory.

They found that, as heat flows from the surface of a hot particle to a cold droplet, a vapor layer forms between them. The vapor layer forms a cushion that buffers the droplet's impact, so that it bounces off the particle. Heat is exchanged during that brief contact, but the particle and droplet never actually touch, because the vapor layer forms a high-pressure zone that the droplets cannot overcome.

"Once that vapor layer forms, it would take infinite force to bring the droplet and the particle together," Fan said.

In the computer simulations, the high-pressure zone sometimes pushed back against the heated droplet so that it bounced away, or it broke up when it rebounded.

When Fan's team compared the simulations to experiments in the lab, the behavior of the droplets matched almost exactly.

Scientists can apply this finding in industries such as oil refining, where hot-and-cold objects routinely interact. For example, the Ohio State researchers are now testing how different mixes of particles and droplets affect heat flow to help the droplets evaporate.


Story Source:

The above story is based on materials provided by Ohio State University. Note: Materials may be edited for content and length.


Cite This Page:

Ohio State University. "When The Heat Is On, Droplets, Particles In A Fluid Ride On A Cushion Of Vapor -- And Never Touch." ScienceDaily. ScienceDaily, 29 March 2006. <www.sciencedaily.com/releases/2006/03/060329084346.htm>.
Ohio State University. (2006, March 29). When The Heat Is On, Droplets, Particles In A Fluid Ride On A Cushion Of Vapor -- And Never Touch. ScienceDaily. Retrieved September 20, 2014 from www.sciencedaily.com/releases/2006/03/060329084346.htm
Ohio State University. "When The Heat Is On, Droplets, Particles In A Fluid Ride On A Cushion Of Vapor -- And Never Touch." ScienceDaily. www.sciencedaily.com/releases/2006/03/060329084346.htm (accessed September 20, 2014).

Share This



More Matter & Energy News

Saturday, September 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

MIT BioSuit A New Take On Traditional Spacesuits

MIT BioSuit A New Take On Traditional Spacesuits

Newsy (Sep. 19, 2014) The MIT BioSuit could be an alternative to big, bulky traditional spacesuits, but the concept needs some work. Video provided by Newsy
Powered by NewsLook.com
Virtual Reality Headsets Unveiled at Tokyo Game Show

Virtual Reality Headsets Unveiled at Tokyo Game Show

AFP (Sep. 18, 2014) Several companies unveiled virtual reality headsets at the Tokyo Game Show, Asia's largest digital entertainment exhibition. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Apple's iOS8 Includes New 'Killswitch' To Curb Theft

Apple's iOS8 Includes New 'Killswitch' To Curb Theft

Newsy (Sep. 18, 2014) Apple's new operating system, iOS 8, comes with Apple's killswitch feature already activated, unlike all the models before it. Video provided by Newsy
Powered by NewsLook.com
Stocks Hit All-Time High as Fed Holds Steady

Stocks Hit All-Time High as Fed Holds Steady

AP (Sep. 17, 2014) The Federal Reserve signaled Wednesday that it plans to keep a key interest rate at a record low because a broad range of U.S. economic measures remain subpar. Stocks hit an all-time high on the news. (Sept. 17) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins