Tech Bite

Gas Turbine Heat Transfer 2008

2008-01-09T12:29:00.000-08:00

Click on the slideshow to access the album at Picasa

An experiment that hints we are wrong on climate change

2007-02-13T06:12:00.000-08:00

Writing in London's "The Times", Nigel Calder, former editor of New Scientist, says the orthodoxy must be challenged

More can be read at http://antigreen.blogspot.com/2007/02/experiment-that-hints-we-are-wrong-on.html

Extracting hot & cold air...

2006-06-14T00:37:00.000-07:00

Question:

As you and a friend are working on cleaning out your garage, you come across your old air compressor and see that it is still charged with high-pressure air from the last time you were using it. You tell your friend that you can extract either hot or cold air (relative to ambient) from the tank at high flow rates without using any external power at all. Your friend thinks you're crazy and bets you $50 that you can't do it. You proceed to prove him wrong, and you win the bet. How did you do it?

Answer:

You attach a vortex tube (also known as a Ranque-Hilsch Vortex Tube) to your compressor (you just happened to have one hanging around...) and proceed to show him that hot air is expelled from one end and cold air from the other. Vortex tubes have been around for many years and are commercially available. First discovered experimentally by Georges Ranque in 1933, and further refined and studied by Rudolf Hilsch in 1946, the vortex tube is a simple-to-construct and difficult-to-explain passive device — essentially a simple tube into which high-pressure air is introduced circumferentially. This air spins at upwards of a million rpm and through a process that to this day is still not well understood, the air separates into two flows: one in the center, which is relatively cool, and one towards the tube's wall, which is relatively hot.

In a counterflow vortex tube the cool air is allowed to flow from the center of the tube at one end and the hot air from an annulus at the other end. Usually a valve is used to vary the flow rate and, hence, the temperature separation. In a uniflow tube the two air streams are emitted out the same end, but again, the cold air comes from the center and the hot air from an outer annulus. The temperature difference for a given length/diameter counterflow tube is a function of the incoming air pressure, the center "throttling" opening diameter on the cold side, and the size of the annular "valve". For a tube set up for maximum temperature difference with ambient temperature inlet air, it is said the tube can generate a hot air flow of about 100 degrees F and cold flow at about -70 degrees F. When adjusted for maximum hot air temperature, it is said the hot side can generate a flow at about 350 degrees F. So it appears that Maxwell's demon is alive and well.

See a Vortex Tube here

Nanomaterials...Better Materials

2006-06-05T13:12:00.000-07:00

What do seashells, lotus leaves, the human skin, jet engines and microchips have in common?

They all represent a unique merger of structure, form and function. These natural and man made structures rely on an exquisite control of materials internal structure, often referred to as the micro- or nanostructure of the material, to achieve their function.

Find more at GE's Blog spot

Its really a nice site !!!

The Woman Who Never Forgets

2006-06-04T04:21:00.000-07:00

Does AJ have the world's best memory?
By Susan Kruglinski
DISCOVER Vol. 27 No. 06 | June 2006 | Mind & Brain

"I can remember everything that has happened to me—what day it was on, what was happening in the world, who was in my life at the time, and usually what the weather was like," says the subject known only as AJ. Researchers at the University of California at Irvine describe AJ as the first reported case of a person capable of near-perfect feats of recollection without using mnemonic tricks.

But K. Anders Ericsson, a cognitive scientist at Florida State University, contends that his research shows how ordinary people can easily acquire extraordinary recollection skills. AJ kept a 24-year diary and admits that she ruminates over dates and events. That obsessive quality may be the key to her ability, Ericsson says. "It's possible that anyone who put in half an hour a day thinking about what they were doing would be able to build up a memory comparable to hers." James McGaugh, one of the Irvine scientists who has studied AJ, remains convinced of her superlative memory and is determined to find out how it works. "She is not a mnemonist," he says. "She does it naturally and inadvertently."

To read an interview with AJ, click here

The Dark Side of the Sun

2006-06-04T04:07:00.000-07:00

Scientists spot solar storms before they spin this way
By Bjorn Carey
DISCOVER Vol. 27 No. 06 | June 2006 | Astronomy & Physics

On the sun, what you can't see can fry you. The sun rotates so slowly that it takes about a month to complete one turn, meaning that activity on its farside is hidden for up to two weeks at a time. If a giant magnetic storm is brewing on the farside, it will hit Earth with a flood of radiation as it finally rotates into view. That happened in 2003, when the unexpected blast knocked out communications satellites and interfered with airplane navigation systems. Now scientists using NASA's Solar and Heliospheric Observatory (SOHO) satellite can peer right through the sun and anticipate such storms well before they hit.

The secret is learning to "see" the sun in sound, says Phil Scherrer of Stanford University. Every second about 7,000 California-size bubbles of hot plasma rise to the surface of the sun and pop, creating a cacophony of sound waves. As the waves reverberate through the interior, they reflect off the surface of the sun's farside before returning to the front, where they create a slight ripple that SOHO's instruments can detect. Sound waves speed up when they hit a magnetically active region on the back side, so if they return to the front a bit sooner than normal, that means a magnetic storm is brewing.

The new method should give significantly more advance warning to satellite operators and air traffic controllers. It may help protect astronauts on the moon or traveling to Mars (see "Impossible Journey?"). "Now we don't have to wait to see the storm," Scherrer says. "You can see that it's coming around the corner."

No More Nerve Damage

2006-06-04T03:59:00.000-07:00

A new drug reverses nerve damage in diabetics.

By Eva Gladek

May 26, 2006 | Biology & Medicine

It could be the first treatment for a terrifying problem faced by people with diabetes – the nerve damage that's a leading cause of amputations. A new drug being tested in people with diabetic nerve damage uses a patient's own genes to treat them.

Diabetic neuropathy nerve damage, which causes a loss of sensation in the hands and feet, can allow small injuries to go unnoticed and become severely infected, to the point where amputation is the only option. Tight control of blood sugar can keep neuropathy at bay, but there is no cure.

"There are a variety of medications that are available now that can help with the pain but unfortunately, there's nothing available to help with numbness or prevention of nerve damage," says diabetes specialist Mark Kipnes, MD, director of the Diabetes and Glandular Disease Research Clinic in San Antonio, Texas.

TTML Week End Seminar Series - old ppt

2006-06-02T05:10:00.000-07:00

I found in my HDD, one of the old presentation entitled "y+ :: How far you have to go"

You can download the PDF file of the presentation file from here.

The content of the .ppt is purely taken from Internet resources. Even though some references were not shown in the ppt, it is not intentional and the resources are acknowledged now.

If you want to view the original ppt, please mail me to sekarannk@gmail.com

TTML Week End Seminar Series

2006-06-02T04:16:00.000-07:00

In our Thermal Turbo Machines Lab (TTML) we have planned to arrange seminars in the week ends, on Friday evening 1600 hrs.

We started with lots of Zeal and interest. it went nicely for some time (few weeks) and then came to a halt, because of the exams and semester ending. Some inertia was there to start it again. This week (today) we emerge as "Pheanix" to start the first seminar after the break. I took the session entitled, "Gas Turbine Blade Manufacturing".

The content of the .ppt is purely taken from Internet resources. Even though some references were not shown in the ppt, it is not intentional and the resources are acknowledged now.

You can download the PDF file of the presentation file from here. If you want to view the original ppt, please mail me to sekarannk@gmail.com

Typical Gas Turbine Blade

2006-05-26T07:51:00.000-07:00

God of small things...

2006-05-26T04:46:00.000-07:00

The earth is a part of our Solar System, which is one of the systems in the Milky Way Galaxy. It is said that there are lots and lots of Galaxies in the universe.

Think for a while how SMALL we are .... and how BIG we are making issues among ourselves.

Flying Machine

2006-05-25T10:19:00.000-07:00

Da Vinci's sketches find new life.

By Jack Penland
May 16, 2006

For thousands of years, man dreamt of flying, and one of the biggest dreamers was Leonardo da Vinci. Five hundred years ago he studied and dissected birds, trying to find the secret of flight. He made notes, and initial drawings, but that is as far as he went.

Two Seattle area men chose to finish the job, building a full size flying machine with flapping wings. Today such things are called ornithopters. While others before had created models based upon the drawings, retired engineer Sandy McLaughlin and retired schoolteacher John Grove wanted to add the detail that da Vinci might have done. McLaughlin explained he wanted, "to try and do what he (da Vinci) could have done if he kept working on aviation."

Read more here

The Physics of . . . Waterslides

2006-05-25T09:41:00.000-07:00

Hurtling Toward Chaos
When waterslides reach a certain speed, no scientist can predict their behavior

By Elizabeth Svoboda
DISCOVER Vol. 26 No. 07 | July 2005 | Astronomy & Physics

Standing 76 feet above Orlando, Florida, staring down the throat of the Blue Niagara slide at the Wet’nWild water park, some riders have been known to have second thoughts. Powerful pumps churn the cascading water at the top of the slide into a furious froth, muffling the sound of parkgoers seven stories below. “Just go for it!” the ride operator urges, and another human torpedo surrenders to the froth, accelerating to a velocity of about 40 feet per second while careering through the slide’s 300 feet of looping tubes.

“Yup, that’s a crazy one,” engineer Marvin Hlynka says, chuckling. Hlynka works for WhiteWater West Industries, a firm in Richmond, British Columbia, that designed the Blue Niagara and other extreme waterslides. It’s his job to use science to find new ways to scare riders out of their minds, but there’s a limit to how much his equations and computer programs can help him. In the alternate universe of waterslide design, Newtonian models don’t always work, and chaos lurks in every hairpin turn. “In terms of actually predicting where a particular drop of water or a particular body is going to be in the slide at any given time, you can’t do it,” Hlynka says. “It’s just not possible.”

Photo Courtesy of V.S.R. Somandepalli, Y.X. Hou and M.G. Mungal, Stanford University

SMOKE IN THE WATER
The swirling eddies in a turbulent stream—shown here in a laboratory simulation at Stanford University—follow the same chaotic physics as does the smoke rising from a cigarette. The water is flowing from left to right and has been dyed to better reveal its patterns.

Read full story