Saturday, January 5, 2013
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Research update: Jumping droplets help heat transfer
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Public release date: 4-Jan-2013[ | E-mail |
Share ] Contact: Sarah McDonnell
s_mcd@mit.edu
617-253-8923
Massachusetts Institute of Technology
CAMBRIDGE, MA -- Many industrial plants depend on water vapor condensing on metal plates: In power plants, the resulting water is then returned to a boiler to be vaporized again; in desalination plants, it yields a supply of clean water. The efficiency of such plants depends crucially on how easily droplets of water can form on these metal plates, or condensers, and how easily they fall away, leaving room for more droplets to form.
The key to improving the efficiency of such plants is to increase the condensers' heat-transfer coefficient a measure of how readily heat can be transferred away from those surfaces, explains Nenad Miljkovic, a doctoral student in mechanical engineering at MIT. As part of his thesis research, he and colleagues have done just that: designing, making and testing a coated surface with nanostructured patterns that greatly increase the heat-transfer coefficient.
The results of that work have been published in the journal Nano Letters, in a paper co-authored by Miljkovic, mechanical engineering associate professor Evelyn Wang, and five other researchers from the Device Research Lab (DRL) in MIT's mechanical engineering department.
On a typical, flat-plate condenser, water vapor condenses to form a liquid film on the surface, drastically reducing the condenser's ability to collect more water until gravity drains the film. "It acts as a barrier to heat transfer," Miljkovic says. He and other researchers have focused on ways of encouraging water to bead up into droplets that then fall away from the surface, allowing more rapid water removal.
"The way to remove the thermal barrier is to remove [the droplets] as quickly as possible," he says. Many researchers have studied ways of doing this by creating hydrophobic surfaces, either through chemical treatment or through surface patterning. But Miljkovic and his colleagues have now taken this a step further by making scalable surfaces with nanoscale features that barely touch the droplets.
The result: Droplets don't just fall from the surface, but actually jump away from it, increasing the efficiency of the process. The energy released as tiny droplets merge to form larger ones is enough to propel the droplets upward from the surface, meaning the removal of droplets doesn't depend solely on gravity.
Other researchers have worked on nanopatterned surfaces to induce such jumping, but these have tended to be complex and expensive to manufacture, usually requiring a clean-room environment. Those approaches also require flat surfaces, not the tubing or other shapes often used in condensers. Finally, prior research has not tested the enhanced heat transfer predicted for these types of surfaces.
In a paper published early in 2012, the MIT researchers showed that droplet shape is important to enhanced heat transfer. "Now, we've gone a step further," Miljkovic says, "developing a surface that favors these kinds of droplets, while being highly scalable and easy to manufacture. Furthermore, we've actually been able to experimentally measure the heat-transfer enhancement."
The patterning is done, Miljkovic says, using a simple wet-oxidation process right on the surface that can be applied to the copper tubes and plates commonly used in commercial power plants.
The nanostructured pattern itself is made of copper oxide and actually forms on top of the copper tubing. The process produces a surface that resembles a bed of tiny, pointed leaves sticking up from the surface; these nanoscale points minimize contact between the droplets and the surface, making release easier.
Not only can the nanostructured patterns be made and applied under room-temperature conditions, but the growth process naturally stops itself. "It's a self-limiting reaction," Miljkovic says, "whether you put it in [the treatment solution] for two minutes or two hours."
After the leaflike pattern is created, a hydrophobic coating is applied when a vapor solution bonds itself to the patterned surface without significantly altering its shape. The team's experiments showed that the efficiency of heat transfer using these treated surfaces could be increased by 30 percent, compared to today's best hydrophobic condensing surfaces.
That means, Miljkovic says, that the process lends itself to retrofitting thousands of power plants already in operation around the world. The technology could also be useful for other processes where heat transfer is important, such as in dehumidifiers and for heating and cooling systems for buildings, the authors say.
Challenges for this approach remain, Miljkovic says: If too many droplets form, they can "flood" the surface, reducing its heat-transfer ability. "We are working on delaying this surface flooding and creating more robust solutions that can work well [under] all operating conditions," he says.
The research team also included postdocs Ryan Enright and Youngsuk Nam and undergraduates Ken Lopez, Nicholas Dou and Jean Sack, all of MIT's mechanical engineering department.
###
The work was supported by MIT's Solid-State Solar Thermal Energy Conversion Center, the U.S. Department of Energy, the National Science Foundation and the Irish Research Council for Science, Engineering and Technology.
Written by David Chandler, MIT News Office
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AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
Public release date: 4-Jan-2013[ | E-mail |
Share ] Contact: Sarah McDonnell
s_mcd@mit.edu
617-253-8923
Massachusetts Institute of Technology
CAMBRIDGE, MA -- Many industrial plants depend on water vapor condensing on metal plates: In power plants, the resulting water is then returned to a boiler to be vaporized again; in desalination plants, it yields a supply of clean water. The efficiency of such plants depends crucially on how easily droplets of water can form on these metal plates, or condensers, and how easily they fall away, leaving room for more droplets to form.
The key to improving the efficiency of such plants is to increase the condensers' heat-transfer coefficient a measure of how readily heat can be transferred away from those surfaces, explains Nenad Miljkovic, a doctoral student in mechanical engineering at MIT. As part of his thesis research, he and colleagues have done just that: designing, making and testing a coated surface with nanostructured patterns that greatly increase the heat-transfer coefficient.
The results of that work have been published in the journal Nano Letters, in a paper co-authored by Miljkovic, mechanical engineering associate professor Evelyn Wang, and five other researchers from the Device Research Lab (DRL) in MIT's mechanical engineering department.
On a typical, flat-plate condenser, water vapor condenses to form a liquid film on the surface, drastically reducing the condenser's ability to collect more water until gravity drains the film. "It acts as a barrier to heat transfer," Miljkovic says. He and other researchers have focused on ways of encouraging water to bead up into droplets that then fall away from the surface, allowing more rapid water removal.
"The way to remove the thermal barrier is to remove [the droplets] as quickly as possible," he says. Many researchers have studied ways of doing this by creating hydrophobic surfaces, either through chemical treatment or through surface patterning. But Miljkovic and his colleagues have now taken this a step further by making scalable surfaces with nanoscale features that barely touch the droplets.
The result: Droplets don't just fall from the surface, but actually jump away from it, increasing the efficiency of the process. The energy released as tiny droplets merge to form larger ones is enough to propel the droplets upward from the surface, meaning the removal of droplets doesn't depend solely on gravity.
Other researchers have worked on nanopatterned surfaces to induce such jumping, but these have tended to be complex and expensive to manufacture, usually requiring a clean-room environment. Those approaches also require flat surfaces, not the tubing or other shapes often used in condensers. Finally, prior research has not tested the enhanced heat transfer predicted for these types of surfaces.
In a paper published early in 2012, the MIT researchers showed that droplet shape is important to enhanced heat transfer. "Now, we've gone a step further," Miljkovic says, "developing a surface that favors these kinds of droplets, while being highly scalable and easy to manufacture. Furthermore, we've actually been able to experimentally measure the heat-transfer enhancement."
The patterning is done, Miljkovic says, using a simple wet-oxidation process right on the surface that can be applied to the copper tubes and plates commonly used in commercial power plants.
The nanostructured pattern itself is made of copper oxide and actually forms on top of the copper tubing. The process produces a surface that resembles a bed of tiny, pointed leaves sticking up from the surface; these nanoscale points minimize contact between the droplets and the surface, making release easier.
Not only can the nanostructured patterns be made and applied under room-temperature conditions, but the growth process naturally stops itself. "It's a self-limiting reaction," Miljkovic says, "whether you put it in [the treatment solution] for two minutes or two hours."
After the leaflike pattern is created, a hydrophobic coating is applied when a vapor solution bonds itself to the patterned surface without significantly altering its shape. The team's experiments showed that the efficiency of heat transfer using these treated surfaces could be increased by 30 percent, compared to today's best hydrophobic condensing surfaces.
That means, Miljkovic says, that the process lends itself to retrofitting thousands of power plants already in operation around the world. The technology could also be useful for other processes where heat transfer is important, such as in dehumidifiers and for heating and cooling systems for buildings, the authors say.
Challenges for this approach remain, Miljkovic says: If too many droplets form, they can "flood" the surface, reducing its heat-transfer ability. "We are working on delaying this surface flooding and creating more robust solutions that can work well [under] all operating conditions," he says.
The research team also included postdocs Ryan Enright and Youngsuk Nam and undergraduates Ken Lopez, Nicholas Dou and Jean Sack, all of MIT's mechanical engineering department.
###
The work was supported by MIT's Solid-State Solar Thermal Energy Conversion Center, the U.S. Department of Energy, the National Science Foundation and the Irish Research Council for Science, Engineering and Technology.
Written by David Chandler, MIT News Office
[ | E-mail | Share ] ?
AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
Source: http://www.eurekalert.org/pub_releases/2013-01/miot-ruj010313.php
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Friday, January 4, 2013
Casual Sex: When is it Okay? | datingish
Casual Sex: When is it Okay?
A statistic like this is hard to ignore, and it must be put in context. The study also showed that the above did not hold true for teens in committed relationships. It is only true of teens engaging in non-romantic sex. So, the question surfaces: when, if ever, are we old enough to engage in casual sex?
Of course, everyone is different. Some people probably sleep around in high school and/or college, learn from it, and settle down and are fine. Others, however, might be impacted in a more long-term way by careless decisions they made at a young age.
Other studies have shown that being in a committed relationship is more satisfying and fulfilling than hooking up and sleeping around. So is there ever an appropriate time for casual sex? Is high school too young? What about college?
What do you guys think? Is there ever a time for casual sex? And if so, when?
image source
Source: http://www.datingish.com/770835550/casual-sex-when-is-it-okay-/
Thursday, January 3, 2013
No. 7 Orange beat Rutgers 78-53; Boeheim gets 903
SYRACUSE, N.Y. (AP) ? Jim Boeheim achieved another milestone in his impressive career at Syracuse, and yet passing Bob Knight for second place all-time on the victory list almost seemed like an afterthought.
"I'm proud to be able to do that. I'm happy to get it done," Boeheim said after his seventh-ranked Orange had defeated Rutgers 78-53 on Wednesday night for his 903rd victory, one more than Knight among men's Division I coaches. "To me, this game is not about numbers, it really isn't. It's not about how many points you score or the assists you get. It's about all the people, all the people you meet on the way. It's been an unbelievable experience."
Boeheim, in his 37th season at his alma mater, trails only Duke's Mike Krzyzewski, who has 940 victories, and he was more touched by the phone calls and letters than anything else.
"I got a call from (former St. John's star) Chris Mullin, I think after 900," Boeheim said. "That call meant as much to me as anything because he's the best player, you could argue, who's played in this league. And I got a note from (Butler) coach Brad Stevens, which is interesting because I'm probably his biggest fan. He just thanked me for my contributions to the game.
"If a young coach thinks that way about me, then I'm really happy. That's what I'm really proud about."
Boeheim was also proud of the way Syracuse (13-1, 1-0 Big East) performed en route to its 33rd straight home victory, the longest active streak in the nation. The Orange have beaten Rutgers (9-3, 0-1) 13 straight times.
Brandon Triche had a season-high 25 points, hitting 5 of 7 3-point attempts, and added six assists and four steals to lead Syracuse. Michael Carter-Williams finished with 12 points and 10 assists, his eighth double-double, and C.J. Fair had 15 points and three blocks.
Eli Carter led Rutgers with 19 points while Myles Mack, who entered the game averaging 14.5 points, did not score and was 0 of 3 from behind the arc. He entered the game leading the Big East at 51.2 percent from 3-point range.
The Scarlet Knights had won five straight but were no match for Syracuse in coach Mike Rice's first game back after a three-game, 16-day suspension for inappropriate behavior and language. Rutgers went 3-0 under associate head coach David Cox, capped by a 68-56 win over Rider on Friday.
Rice was suspended without pay and fined $50,000 on Dec. 13 for a violation of athletic department policy. Rice, 43, who returned to the team on Saturday, is in his third season at Rutgers. A former guard at Fordham, Rice came to Rutgers from Robert Morris, where he took the Colonials to the NCAA tournament twice.
Rutgers has defeated three top 10 teams at home under Rice, but the program has never accomplished the feat on the road. Syracuse won the game with a 21-0 run over the final 6:42 of the first half to break open what had been a tight affair.
Rutgers committed 10 turnovers in each half and was outscored 20-7 on the fast break.
"We're really good when we're scoring and things are going our way," Rice said. "The team response ? we lacked the energy, we lacked the toughness. In this league, bad things are going to happen, whether it's missed shots or turnovers, which we really couldn't have against Syracuse, but we had them.
"How are you going to respond defensively? That's what limits their runs, and our defense was a no-show after we stopped scoring."
Carter's runner in the lane at 8:07 gave Rutgers its only lead at 20-18. It was the final basket of the period for the Scarlet Knights. They missed seven shots, committed three fouls and had two shots blocked as the Orange ran away.
Fair followed his own miss to start the Orange surge and consecutive baskets by Carter-Williams, the second a pretty underhanded scoop with reverse spin, gave Syracuse an eight-point lead.
Triche's fast-break layup after a block by Fair and a bank shot off the glass by Rakeem Christmas kept the Orange rolling, and James Southerland's transition 3 made it 35-20 with 2:22 to play.
"It did snowball," said Austin Johnson, who had six points and four rebounds for the Scarlet Knights. "It's a tough place to play. We just have to remain confident and do what we know we're capable of out there. If we do that, we can compete with anybody. Tonight was definitely a clunker."
Triche's lob to Southerland completed the run as Syracuse finished the half 14 of 29 (48.3 percent) from the field while holding Rutgers to 8 of 29 (27.6 percent). About the only mistake the Orange made was Christmas's turnover out of bounds in the final seconds as Syracuse tried to hold for the final shot.
At the outset, the game had the makings of a barnburner. Triche hit three 3-pointers in the first 6 minutes of play, all off assists by Carter-Williams as the Orange gained an early lead. But Carter kept pace with three 3s and another 3 from the wing by Jerome Seagears tied it at 16.
The score was tied four times before Syracuse took control.
"We were playing really well and we were down two," Boeheim said. "I was getting ready for it to be a battle right down to the end, so I'm shocked at what happened during that period of time. We were playing well. Then we started playing even better."
Both teams are leaving the conference, Syracuse after the season for the Atlantic Coast Conference and Rutgers for the Big Ten at a date that's still to be determined.
Source: http://news.yahoo.com/no-7-orange-beat-rutgers-78-53-boeheim-020815644--spt.html
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Wednesday, January 2, 2013
Tuesday, January 1, 2013
WTS: Apple iPhone 4S 16GB Black | Refurbished | 250.00 USD
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