July 5th, 2009

Ann Vole

Radiant flooring and Raynolds number

New infrared imaging equipment is very cheap now so installers are finding that there are better ways of making radiant floor heating such as heat plates. Heat plates are just sheet or cast metal that conduct the heat away from the source of heat and then radiate that heat through the flooring material. To be more durable, I figured the besr tile shape should be a hexigon (6-sides, closest to round while still having flat sides). The problem is I wanted to put the tubes between the tiles in the cracks and a hexigon tile will mean lots of bends. When a fluid flows through a pipe slowly, it flows fastest in the middle of the pipe and slower as it gets closer to the inside wall of the pipe (this is called "laminar flow"). When the fluid flows faster, eventually eddies form causing the fluid to mix up (called "turbulent flow") and thus the resistance to the flow is much greater so the pump needs to work harder. Normally having a pump work harder is a bad thing but if it is your source of heat energy, you want more resistance. Oil is usually not used for radiant floor heating fluid because it usually flows too fast for laminar flow. The point where laminar flow becomes turbulent flow is determined by a calculation and whether the results are above or below a number called Raynolds Number. This sort of radiant heating system will use more energy for the pump but all that energy will go to heating the floor more then the heat in the fluid before it is pumped thought the pipes in the floor. I was thinking of having the oil pumped with both an electric pump and by a hydraulic pump turned by a windmill. This would be able to provide 100% of the heating by wind power on windy days with a low heating load and only need to tap into stored heat if that is not sufficient. Oil will not wear the inside of the pipes, will not freeze, can handle high temperatures, will maximize the life of the pumps and various fans and heat pumps can also be powered with the hydraulic pressure too.