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All good points, Bernie
My impression is that Rusty 1st objective is he would like for the oil
temps to be lower. Assuming that the GM core, Rusty is using for an oil
cooler provides adequate air/metal contact area, then it would appear to me
that the problem at this time is getting more cooling effectiveness from the
airflow. If you have adequate mass flow through the core, you will cool.
However, if you have not adequately slowed the air down (diffusion) then
your cooling drag could be higher than necessary. But, it would appear to
me at this point that cooling is the crucial aspect rather than minimizing
cooling drag. Tight 90 deg turns right before the core does not promote
more flow through the core (in my opinion).
According to K&W (if I understood the math), the more parallel the flow is
to the core surface at entry to the core the greater the pressure loss is
and the less cooling effectiveness. They mention that in these cases the
use of guide vans to direct the airflow more directly into the core passages
can result in cooling effectiveness approaching the straight-in duct. They
also point out that staggering the core layers of the heat exchanger can
also help (not feasible in this case).
There appears to be two situations possible:
1. There is adequate air mass flow to cool - but the system is not
transferring the heat to the air with the best efficiency. In this case,
better diffusion offers improvement.
2. There is not have adequate air mass flow to cool - in this case, it does
not matter how effective you diffuser is, your system will not cool
adequately.
So either situation could apply in Rusty's case.
If the delta T of the cooling air across the core is in the vicinity of
40-50F then I would estimate that he has adequate diffusion but perhaps not
adequate air mass flow to cool. In other words, the system is transferring
the coolant heat to the air with high efficiency - but, simply not enough
air to carry away adequate heat.
If the Delta T is closer to 20F then he may have sufficient air mass flow
but inadequate diffusion (does not slow the air down enough for maximum heat
transfer)
Even with the best diffuser a system will not adequately cool if there is
inadequate mass flow through the core. So my focus would be 1st focused on
increasing the mass flow. Just my opinion, of course.
Ed Anderson
>
Rusty and Ed,
Ed, maybe you know more about his configuration than what I can glean from
his schetches. I think we need to know whether he is trying to almost
totally diffuse the air like mine (hopefully :>) ) to minimize the turning
pressure loss and allow the flow to accelerate thru the cooler or whether he
is trying to do the Lamar type min height and volume flow path.
Rusty, what is the x-cross maximum area perpendicular to the cooler
compared to the inlet area?
Boy the weather looks like it should be good on Wed for your flight down
Ed. Rusty, really sorry you aren't going to make it next weekend, I really
want to meet the guy behind all these emails.
Bernie
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