[Gooserider]

I'm doing sort of a combo approach, you might be able to do a variant on it.

My rad is a Fedco 2-342 equivalent, single pass unit, approx. 6" X 9.5" on the cooling surface, big enough for two 120mm fans. Heated water enters from the bottom, and exits after cooling from the top. I realized that since it's a single pass unit, if I blew constant air through it, I would get a temperature gradient with most of the cooling occurring on the bottom half of the rad. I also have setup the rad to be the only planned air intake into the case, so blowing all the air out would leave the case interior starved for airflow.

So I split the difference, with a two part shroud. The bottom half is like your triangle, and runs from the center of the rad down to the 120mm x 38mm fan in the bottom of the case (which is mounted on casters) blowing the warmest air out the bottom. I'll be putting a skirt around the front bottom of the case to help with noise suppression and to prevent the warmed air from getting recirculated into the rad on the front of the case.

The top half is a parrallelogram shaped box angled to drop the fan a little bit down (in order to make more room for the plumbing coming off the top of the rad) with a second 120mm x 38mm blowing straight through into the case to cool anything that needs it and feed the PSU and the 2 120mm x 25mm exhaust fans. I will have a filter on the front side of the rad, and set the fans up to have positive pressure in the case so as to keep the dust bunnies out.

Also note that the whole question of 'blowing heated air from the rad through the case' is largely a non issue... The air coming off the rad is only going to be 2-3*C warmer than ambient, which isn't really going to make that much difference....

Gooserider