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Anatomy
of a various chargecooler designs
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The reason
why our tubular cooler is so efficient is it follows the basic simple
physics that all air/water heat exchangers should follow. All chargecoolers
should be of a 'countercurrent'
design, which means that cold water from the pre-rad should be fed
into the 'cold (outlet)' end of the chargecooler and the hot water
that has absorbed all the charge heat comes out of the 'turbo
(inlet) end of the unit. The reason for this is that the coldest
water is keeping the coolest end of the CC cool, and the slightly
warmed water at the hot end will not actually increase the temps
at the 'hot end'. If the water flow is changed to a 'concurrent'
design, so the cold water cools the hot end, then like wise, the
water temps will heat up, and thus the 'cold' end of the charge cooler
can not be any colder than the temperature of the '
heated ' water. Confused? For more information view the Wikipedia
on heat exchanging.
Right, so now the
basic physics are sorted, now you have to look at the physical
design of the cooler. If you look at the top right pic of the
internal core, you will see it looks very different to a
traditional intercooler core. The core is a ONE PIECE aluminium
extrusion, which means no welds, braized bars or ends, and thus is
burst proof as there is no weak point to break on boost, or leak
water into the core. Our CC cores have been tested to over 60psi
in drag race use with zero failures.
You
will also
notice the core is 'segmented'. This is too allow the coolant to
flow around the outside circumference of the core, down the middle
of the fins and across the fins, so basically coolant can flow in
all directions. This also means that air locks are less likely as
they can not get stuck in a particular channel - Air lock problems
are also relieved by having the coolant inlet and outlets at the
very top of the core..
Flow wise, our
cores are very efficient. The internal channels are very unrestrictive, and they have internal 'fingered' fins which add to
the cooling capacity. The cores have a variety of inlet and outlet
neck diameters from 2.5" right up to 4" for up to
2000bhp applications, but please note that the internal area of
all the channels inside the core is always larger than the
inlet/outlet diameters, to provide next to no pressure drops -
Pressure drops figures are hard to take any proper data from as
some cheap intercoolers have have very low figures simply down to
the fact that they have very large internal channel areas but
hence don't cool as well (a 3" diameter tube has zero
pressure drop - doesn't make a very good intercooler though), but
our cores are recording only 1-1.5 psi pressure drop at over 20psi
of boost and over 400cfm of flow, whilst still maintaining
excellent cooling ability, and superb recovery speed. Circa
10-25 degrees above
ambient in all conditions, with instant recovery time even
under extended WOT periods when combined with our specific AVT/Bosch
pump and rad/fan/tank...and of course, the quality of your
installation. |
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You will find that 99% of
all other 'chargecoolers' on the market are just traditional 'intercooler'
cores surrounded by a 'water jacket'. The problem with this (as you can
see in the left picture) is that they are made in 'reverse'. If you look,
the charge from your turbo is being blown through what is used in a normal
intercooler to grab to cool ambient air, and the water is channels through
the tiny bars which normally take the boosted charge. The main problem
with this is inefficiency. The bars on intercoolers are designed to be efficient
for the boost, but all the tiny fins are not as they do not need
to be (as its just moving air from outside the car going through it) So
the main problem is, you are now trying to push say, 20psi of boost
through tiny fins which are not designed for air flow as hence you get a
very large pressure drop across the core. The other problem is as the
water flows through the small bars, there is hardly any coolant volume
flowing so it heats up very quickly. On top of that, many of these CC
designs use multiple cores stacked together - As they are not aligned
perfectly, the air flow is hindered more by turbulence and more pressure
drops occur. On a bar of boost, figures of up to 7psi have been lost
through restriction at high engine CFM levels.
Another main flaw, is as
these are just intercooler cores, there is numerous points of attachment,
such has braized bar ends, fins and welding. These are all weak points
which can cause serious engine damage if they fail under boost, hence why
many of these designs are only warranted to around 1 bar of boost maximum
by their respective manufacturers.
The two lower pictures
are of another popular design of CC unit, but is still basically an
intercooler core with a water jacket surrounding it, still with the flaws
of the boosted charge being blown through the restrictive fins. These cores
have a very short distance from inlet to outlet, so the air passing though
the core does not have a long time to cool. There have been some very low
pressure drop figures recorded for these units, but that is due to there
is hardly any length of core being used. Often you see this type of design
being used with very large coolant header tanks (rear mounted) in order to
gain efficiency, but this is not required if the core is designed
properly.
But THE main flaw is the
water flow direction inside the core. If you look, the water inlet outlets
are not on either end of the core (following the direction of the charge),
but they are on the SIDE of the core.......? The flow is neither
countercurrent or concurrent...
So, the boost is not
being cooled as it goes 'through' the core, infact, only one 'side' of the
core has cool water on it, and the other side of the core has the warm
water outlet! A completely illogical design of heat transfer, and hence
the need for massive coolant tanks and very high output pumps in order to
'flood' the core in a hope to improve its cooling ability.
Another problem with side
mounting the inlet/outlets is air lock problems. If the core is not
perfectly level, then air bubbles can rise back to the end of the core with
the lower fitting, and get trapped in the top corners. Adding to the fact
that being an intercooler core inside, and that the water cannot flow
between the channels, then air can be trapped inside a certain channel and
difficult to eliminate.
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