am inclined to make an analogy with the tuned stacks on race engines
in a certain velocity range the pressure pulses are 'in phase' (wrt the manifold vacuum) and their throughput increases
- but will be worse above and below this range
with the fluid changing direction, there will be an entrance effect and the flow will not become uniform for some distance (depending also on the velocity and diameter)
the same factors that promote a turbulent flow regime can also serve to inhibit it
note that the 'bump' occurs at different velocities for the different sized round tube rads
(disregard the very small rad data, high variation due to the small temp/flow rates)
I am quite sure myv65 can describe this with the correct terminology
(I'll ask another fellow also, but this is not a good forum for the uninitiated)
I just found out yesterday that the Serck is an oil cooler with pleated turbulators in the flat tubes
(as are Mocal rads, also from the UK)
the BeCooling 'dual' rad is a very exceptional performer (not in the original article) which also has fluted turbulators in the straight sections
turbulators are excellent devices, but make the rad atypical
|