Hi Gang,
I don't get to write in very often as I don't (as yet) have a Tiger, but in
the area of heat transfer, fluid mechanics, and heat exchangers I can
contribute!
The comment on the triple pass radiator that "I have never heard an
explanation" prompted me to write in. While I haven't actually seen one of
these rascals the comment that "it works very well but may require
excessive water pump pressure" and "a two-pass... leaves the outlet and
inlet on the same side" leads me to believe that the design concept would
be similar to "stacking" multiple single pass radiators and plumbing them
in serial with the hot fluid coming in the back most radiator and the
coolest fluid leaving out the front radiator.
The amount of heat transfered from a given heat exchanger (such as a
radiator) is proportional to the area available for contact between the hot
fluid and the cooling media. So, as the number of passes increases so does
the surface area and thus heat removal ability. In addition to surface
area, the heat transfered is also a function of the temperature difference
between the hot and cold fluids at the inlet and exit. This is not a simple
average temperature (as they are changing from the inlet to outlet) but a
"log-mean" temperature difference...suffice to say that a bigger
temperature difference will lead to increased heat transfer. Therefore the
design mandates that (hopefully) the hot fluid enters at the back most pass
where the air is now hot but the temperature differece remains large and
the coolest fluid leaves at the front where the air is the coolest thus,
again, giving the biggest temperature difference. The last variable in this
calculation is the velocity of the two fluids (in our case air and cooling
fluid). Higher velocity of each leads to increased heat transfer by several
mechanisms that I will spare you from hearing about (Lecture # 37!).
Hope the above rattle is helpful. If you have questions let me know. I love
this stuff!
Brian Farkas
Tiger owner someday! and
Assistant Professor, Process Engineering
NC State University
At 11:58 AM 8/30/98, Bob Palmer wrote:
>Armand, Lorie, et Listers,
>
>I couldn't access this site, but with regard to a triple-pass radiator,
>this is certainly not a new concept. I first saw this type of radiator in
>the mid '70s, and they probably weren't new even then. I have never heard
>an explanation I believed about why double or triple pass would be better.
>I had a long conversation with Ron Davis (aluminum racing radiator builder)
>about the multiple pass concept and he believes that two is better than
>one, but three is too much. This I am sure of, a three pass radiator has
>NINE TIMES ( that's 9X) the flow resistance of a single pass radiator. If
>you try using a garden hose to run water through a three-pass, you'll
>quickly see what I mean. I ended up getting a three-pass from Ron, but am
>not convinced I did the right thing; would have preferred a two-pass, but
>that leaves the outlet and inlet on the same side so it requires some
>modifications to the hoses and water pump. At the very least, a three-pass
>needs a good water pump that will provide enough pressure to ensure good
>flow, especially at low rpms. I got my water pump from Sunbeam Specialties
>and it seems to do a good job. In fact, I drilled a 1/8" hole in the
>thermostat and even this small hole allows enough flow to keep it running
>well below the thermostat regulation temp (195 F) most of the time.
>
>Bob
>
>At 10:35 AM 8/30/98 +0100, Armand & Lorie Ritchie wrote:
>>Hi all I just checked out a neat web site (www.usradiators.com) they have a
>>novel concept of radiator design. Triple flow which they claim is the most
>>efficient. the radiator is made with three separate chambers that the
>>coolant must travel through. They do customs and hotrods also sports cars.
>>You can submit a drawing and they will give you a quote on price.
>>Interesting site.
>>regards Armand Ritchie
>>
>>ritchie@mcn.org
>>Armand & Lorie Ritchie
>>
>Robert L. Palmer
>Dept. of AMES, Univ. of Calif., San Diego
>rpalmer@ames.ucsd.edu
>rpalmer@cts.com
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