If you have waste heat of 140 degrees Celsius, and the area is 30 degrees, then you can up to 27 pe

Convert heat into a deafening sound, and that sound transform back to an even greater heat. It sounds door dipping strange, but it can, and it's door dipping useful too. To use the process for recovering energy from waste heat. Researchers ECN in Petten They have come a long way. [With video report]
From the outside you can hear a faint hum at best. But in their inner devices of Simon Spoelstra and his colleagues produce a sound of 170 decibels, loud enough to focus. Irreversible hearing damage Fortunately, they are shut.
The noise generated in thermo-acoustic heat engines, or rather, from a temperature difference. "How that works, I will try to explain in a minute," said Spoelstra. The sound wave travels through a pipe and is converted back to a temperature difference. On the other side by a 'heat pump' door dipping And all that without moving parts.
When ECN Energy Research Centre in Petten Spoelstra's group is investigating the use of these systems in the industry. "In factories is a huge amount of energy door dipping is lost as waste heat. That you will never be able to use all useful, but part is to regain. We think thermoacoustic systems are ideal for that. "
The latest version of the device gets in converting heat into sound, almost door dipping half of the theoretical maximum, says Spoelstra. "That limit is called the Carnot efficiency, the French mathematician Sadi Carnot. door dipping It is a simple calculation: the difference in temperature divided by the highest temperature, in degrees Kelvin ".
If you have waste heat of 140 degrees Celsius, and the area is 30 degrees, then you can up to 27 percent of the heat energy that convert door dipping to movement or sound, charges for Spoelstra. "When you start out at 550 degrees, the theoretical maximum is much higher, with 64 percent. And our latest device gets there almost half, about 31 percent. That's the world. "
The fact that noise can arise from a difference in temperature, has been discovered in the seventeenth century, he says. "By glassblowers. Sometimes they heard a whistling sound when they held a tube in the fire. No one could explain how this sound occurred, which is only much later did it. "
The crux is that sound consists of a wave of themselves and compacting again expanding gas. The sound wave is amplified, if thermal door dipping energy is added, just at the time that the gas is at the compacting made the researcher. "It will be extra off by the heat a little bit later, so that the sound wave is powerful."
At the other end of the tube, do the reverse, door dipping and carries the sound energy is about to increase. Temperature difference Spoelstra: "You can use it to create, for example, from 140 degrees to 190 degrees, residual heat hotter but you can also use it to make cold. Then you have a cooling system that runs on waste heat. "
Not everyone believes door dipping at first glance that you can recover. Energy with this principle "We also had to be convinced, when inventor Kees Buck knocked us with a demonstration model. That was in 1999. A year later we started this research, which he cooperates. "
The fact that people are difficult to empathize, in the operation of the mechanism remains difficult, you Spoelstra. "I am almost certain that we grant are missed because the reviewers did not understand how that works a few times. You have to see it in action to believe it. "
That's what we do with the camera there. door dipping In the workshop, he first shows an open tube and hear a demonstration model of plexiglass and finally door dipping the thermoacoustic engine efficiency with which the record is located. The tube of which is filled with helium under high pressure, in order to enlarge it. The energy content of the sound wave
Ready for use in the industry are the devices yet, but next year the researchers will be testing a larger version, which is 10 kilowatts can exploit. Residual heat Truly commercial use of this technique would then follow, soon hope Spoelstra and his colleagues. door dipping
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