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RE: Temperature drop across a rad

To: Theo Smit <tsmit@isotel.com>,
Subject: RE: Temperature drop across a rad
From: Bob Palmer <rpalmer@ames.ucsd.edu>
Date: Fri, 05 Nov 1999 17:40:00
Tim,

As you probably know from my previous postings on this subject that I have
a three-pass radiator which I have pointed out has the problem of 9X the
flow restriction. (BTW, when I have back flushed this radiator with a
garden hose, the back pressure is very high!) I discussed this with the
builder, Ron Davis, at length. He believes a two-pass is optimal, but could
not be quantitative in comparing the two and three-pass designs. My
experience with this radiator is that as long as you are moving it works
terrific. However, and I attribute this to the 9X restriction, at idle it
doesn't work all that great - at least with a 50/50 coolant mixture. A few
months back I fixed a leak in the heater core and refilled with pure water
plus a can of water pump lubricant. This seems to work better at idle than
the 50/50 mixture did. Now, mind you, this is far from a controlled
experiment and there are possibly some other variables involved, but we
have had some pretty warm weather here in San Diego the past couple of
months and it really seems like the system stays noticeably cooler now that
I am running 100% water.

The gist of this is that, if you want to make the necessary modifications,
I would go with Ron Davis' suggestion to use a two-pass radiator. However,
if you get a three-pass, you should make sure you have a good water pump
(You can never pump too much water through your system!)and use near 100%
water - at least in the summer (I know it does get cold some places!) BTW,
I want to thank Tim for confirming experimentally what I have offered as
the explanation for why the multipass radiators work better - i.e., more
uniform coolant flow. (NOT, BTW, because the coolant spends more time spent
in the radiator!) Now, I realize the reason it works better probably
doesn't matter to most of you guys, so these "engineering" comments are
intended only for the confirmed "gear heads".

My apologies to those for whom this is repetitive,

Bob

At 04:11 PM 11/5/99 -0700, Theo Smit wrote:
>Hi Tim,
>
>How much did the presence of the plastic nose on the Camaro affect the 
>ability of the camera to 'read' the radiator? I think it's a great idea (I 
>remember seeing the van with the camera out at the track) but I think that 
>the Tiger's small nose opening and the fact that those are steel panels may 
>make it more difficult to get a good assessment of the rad efficiency using 
>the infrared camera.
>
>If you make a multipass rad then you increase the flow restriction 
>geometrically, i.e. if you convert a single pass rad to a two-pass, you get 
>four times the restriction (half the number of tubes, and twice the length) 
>and for a three pass, nine times the restriction. Since making the Tiger 
>rad a three-pass is not too hard, what's the general opinion on flow 
>restriction? Is this a limiting factor for a three or four-row HE rad?
>
>Theo
>On Friday, November 05, 1999 8:31 AM, Ronak, TP (Timothy) 
>[SMTP:Timothy.P.Ronak@akzo-nobel.com] wrote:
>> Theo and Rick you said,
>>
><Snip!>
>> In response to Rick's Question,
>> <How would one go about or What is the best way to measure the 
>temperature
>> drop across a radiator?>
>>
><rant snipped>
>> OK, Back when we used to race our "Camero" (OK, there it is.... those of 
>you
>> not reading can now open your eyes and begin reading again) in Calgary we
>> had an opportunity to have our Race Car read by some type of temperature
>> sensing camera. Theo, you may remember this guy out at Race City as he
>> offered to "scan" peoples cars to measure surface temperature. This was a
>> pretty cool thing as it had several levels of sensitivity ranges. What he
>> would do is use a video camera type device that "pictured" the car such 
>that
>> when viewed on a monitor you could see the different colour ranges that
>> represented different temperatures of different components.
>>
><snip>
>>
>>
>> Best regards all,
>> Tim Ronak
>> B382000680
>>
>
>
Bob Palmer
UCSD, AMES Dept.
rpalmer@ames.ucsd.edu

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