Well one area that would help explain the differance in Sense87's first figures and the real world result is that the increased velocity in the system lines in the set up with the single pass would partly offset the reduction in headloss in the rad it's self. I don't know how long BillA's lines are in his test rid, but this would have to account for at least a small portion of the differance.
Also the change from 3/8" inlets/outlets to 5/8"+ would also cause some changes. And perhaps due to the higher flow rate through the rad's finned/tube area, this would also cause a increased headloss at the inlet/outlet area in the single pass.
As there is less than 1 cubic inch of differance between the two rads this couldn't have made much differance.
|