Thermal Performance - Not Always Music to the Ears

Variable Reluctance Brushless DC Motors 'VRBLDC' or Brushless DC motors without permanent magnets, are silent, very fast [20,000 rpm], efficient[over85%] and keep cool, as most losses are in the stator. So no excuses for noisey motors. Cup/Cone magnetic bearings are potentially advantageous, so a 'VRBLDC' motor need not be entirely without permanent magnets. A useful experiment is to take a party balloon, attach a short length of half inch tube, blow it up and release the air. Do this in the quiet of the night. very little noise is made. Another interesting experiment, is to take a disc and cover one or both sides with velvet. Then attach the disc to a fast motor. Smoke from a lighted incence stick reveals that the fast spinning disc behaves like a radial fan. You might be impressed? It may not be quite as efficient as a normal bladed radial fan, but it's close. Importantly it's quiet. Possibly an avenue worth further investigation. White noise is broad spectrum, pink noise has more low frequency components. What would ultraviolet noise sound like to a bat? we might not be able to hear it. A profusion of thousands of very small 'blades' acting like the velvet pile, may also be worth an investigation.

In a word.... CRYOCOOLER Cryocoolers come in a large variety of types, sizes and cooling rates. The latest are the pulse tube cryocoolers, these are being widely used in cooling tele-comunications equipment, not to mention military and space exploration uses. These compact, efficient units can provide cooling down to temperatures of a few degrees Kelvin and are becoming so prolific as to be inexpensive. Check out wwww.cryogenicsociety.org This is the web site of the Cryogenic Society of America.

For those of you who follow 'Baseball' we in the UK called the game 'Rounders' Assume the 'Baseball Bats' are strands of Flock, and the balls are molecules of Air. It is just a thought, but do there exist out there good Virtual Baseball Computer games. I was thinking the programme might be adaptable, so as to model a 'Flocked Disk Radial Fan'. Electrostatics could conceivably be used to set the flock strands, before the glue set, to the ideal subtended angles. A multiplicity of small VRBLDC (Brushless DC Motors) spinning the disks at high revolutions (over 20,000 rpm) might contribute to a low profile 'Silent' cooling system?