Ed Anderson wrote:
> Q = m cp DeltaT. Clearly shows that heat removal is proportional to BOTH mass flow AND deltaT (as well as the specific heat but that is fixed by nature). Yet, for some reason that I still don't understand, you skeptics seem to fixate on the mass flow factor {:>) and ignore DeltaT as if it were a factor you can do nothing about.
>
Ernest wrote:
I think that is because you're reducing mass flow for the thick rad.
You could do the same for the thin rad, and end with the same deltaT.
To fairly compare the radiators, you have to fix the airflow at the
inlet and decide which option you can get to dump the most heat into the
air while offering the least drag.
Of course, out here in the real world it doesn't work that way.
Everything affects everything else, and we have to design the whole
system. We rely on generalities and ROTs, and hope that we wind up with
something that has a passing aquaintence with "optimized". Most of us
will settle for a not to distant relative of "it works".
Good point Ernest but there are factors at work which make it difficult if not impossible to build the thin rad version with the same delta T as the thick rad version. The turbulent flow factor (that has already been pointed out) is one, but the problem of matching the impedance of the high velocity inlet flow to the very low velocity of the radiator flow is the close to impossible one. That's one of the 'real world' factors that favors a thick rad. The term 'impedance' is an electrical term substituted for the aerodynamic term which I can't recall. This whole argument started from this very point in the report that Ed posted where it showed how diffuser performance was better with a higher pressure drop across the rad. THIS is the point that the true thin rad advocates (not that I know of any on this list) need to disprove to win the argument .
Al G's point about the practical range of Delta Ts is his best argument against the thick rad advantage and I freely admit that taking maximum advantage of the thick rad requires pressing the design point toward the upper end of the Delta T range which is more challenging. But again I have to point out that Al is using the thickest off the shelf rad available! It is about
3.5 times thicker than the one in my car. We need to define the terms thick & thin I guess.
Tracy
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