[bigben2k]

Ah yes, that was in feet per second, oops, my bad!


Anyways, I figured that the nozzle is either going to be 1/2 inch diameter, or 3/16:

3/16 nozzle: the opening of such an area is 17.8 mm^2, and that leaves an exit through the fins that can best be described as 8 channels (1 by 5) so 40mm^2, for a ratio of entrance to exit of 0.45 .

Flow speed is 14.2 m/s (46.5 fps). Pressure drop over one inch is 11.7 feet of head.


1/2 nozzle: the opening is 126.7 mm^2, with an exit of 16 channels, 80mm^2, for a ratio of 1.6 .

Flow speed is 8 m/s (26.1 fps). Pressure drop over one inch is 0.1 foot head (1.2 inch).

The above ratios are the smallest and largest, respectively.


Here's the bug: what am I trying to achieve with this inpingement? Since the flow rate is the same everywhere, the exit speed will be higher than the entrance, with a 1/2 nozzle. Using a 3/16 nozzle, the entrance speed is higher, but the exit speed is lower.

So if I go with a 3/16 nozzle, I'll have high-speed (and turbulent) flow within a very small area, which has a diameter of about 5 mm. The nozzle will have to be kept short, given the very high pressure drop.

Note that the turbulence that occurs due to the 90 deg flow bend hasn't been accounted for, yet.


Other progress:

Round saw blades:
The 20mm saw blade, if used to cut 5mm deep, will extend 13.2mm beyond the point of cut, in either direction.
25mm: 15 mm
32mm: 17.2 mm

Which makes the blades pretty useless except for the central cuts, which leaves a center square post.


Turbulator thoughts:

Turbulators at the bottom of the channel: using a 1.0mm drill bit, drill a hole every other 1.0mm, to a depth of 0.5 mm.

Turbulator at the fin: don't leave the fin tips at an angle, cut them off at 90 degrees. Necessary?

[edit]: added depth-of-cut to bottom-of-channel turbulator.