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Re: Temperature drop across a rad

To: Steve Laifman <laifman@flash.net>
Subject: Re: Temperature drop across a rad
From: Bob Palmer <rpalmer@ames.ucsd.edu>
Date: Sat, 06 Nov 1999 13:32:54 -0800
Steve,

You don't seem to be confused about the issue of odd versus even number of 
passes Steve. If you wanted a two-pass you could, for example, move the 
inlet to the same side as the outlet; i.e., the right hand side. This would 
be possible with an alternator if it is located as low as possible or even 
moved to the left hand side (but which I wouldn't recommend).

Regarding cap location vis-a-vis inlet and outlet, in my particular case I 
have the cap located on the right side of the radiator, which is after the 
first of the three passes. In this case, the maximum pressure at the inlet 
to the radiator can be greater than the nominal cap relief pressure. This 
is not the any standard production car I've seen. I run a 16 psig cap, so 
depending on the flow rate through the radiator, the inlet pressure might 
be 5 psig or perhaps even more higher than 16 psig. I believe it is common 
practice to run higher cap relief pressures in race cars - maybe 25 psig, 
so I think a good race type radiator like the one Ron Davis builds should 
take this much pressure.

I seem to have missed the contributions from the "many have argued that the 
Tiger inlet cap ought to be on the same side as the outlet pipe". And I'm 
confused by your next statement as well. I think there are good reasons to 
put the fill tube the same place as the inlet tube, since this is the 
standard configuration on production cars. On the other hand, it is 
certainly convenient on a Tiger to put it on the right hand side, and which 
is the only reason I did it that way.

Regarding running multiple passes one in front of the other versus 
serpentine top to bottom, that's an interesting idea. Run the first pass 
behind the second pass so the coolest air passes over the coolest water. 
However, it looks to me like this would be mechanically a lot harder to 
fabricate.

Well, TTFN,

Bob

At 09:46 AM 11/6/99 -0800, Steve Laifman wrote:
>Bob, et al,
>
>The "two-pass" vs "three-pass" discussion has me somewhat confused.  I did 
>talk to
>the Griffin Radiator people, who make aluminum radiators for most cars 
>(including
>Tiger), and their cut was a little more mundane.
>
>First, on a cross flow radiator, the driving design criteria on "number of 
>passes"
>depends upon which tank you flow in to, and which is your outlet.
>
>On a Tiger, with the input and output being on opposite ends, you must 
>either go
>with 1 pass or three pass.  Two pass would require the outlet to be on the 
>same
>side as the inlet.
>
>Now I do realize that many have argued that the Tiger inlet cap ought to 
>be on the
>same side as the outlet pipe.  I suppose this includes the inlet pipe, but 
>am not
>sure.  In that case you must have three pass, to get the water out of the
>radiator.
>
>In the standard Tiger arrangement, you are limited to one pass (standard with
>copper), or three pass to get the water out the other side.
>
>This makes the assumption that you have the conventional single row aluminum
>radiator.  If you are using multiple rows, and choose to use the passes 
>between
>front and rear rows, then you've got to take that, as well as your outlet
>position, into consideration.  Griffin does NOT recommend running the 
>coolant in
>this manner, but I don't know their reasons.
>
>Steve
>
>--
>Steve Laifman         < Find out what is most     >
>B9472289              < important in your life    >
>                       < and don't let it get away!>
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