[DeTomaso] Single or Dual Pass Radiators?

Tue Jun 14 11:54:52 EDT 2011

Someone mentioned more dwell time in a 2 pass radiator, but if the radiators are the same size (i.e., volume), the only way the dwell time increases is if the flow rate drops.  The increased restriction in a two pass would reduce flow rate (I have no idea how much) so dwell time would increase, but based on comments from Stewart Pumps and others, it's never good to drop flow rate, but there probably is a minimum flow speed where the slower coolant flow speed through a single pass is no longer turbulant, and heat transfer is reduced.

The 16 times the pressure number from Stewart doesn't make sense to me?  I can imagine that with turbulant flow and twice the path length, the pressure drop across the radiator might be a lot greater, and maybe 16 times, greater, but the overall effect would depend on the pressure drop in the radiator compared to the overall system.

The Stewart Tech article that Barry posted explains more of this:

http://www.stewartcomponents.com/tech_tips/Tech_Tips_5.htm

All in all, the scales are tipping towards single pass if it used modern tubes etc.

Ken

--- On Tue, 6/14/11, B. Seib <oldwheel at shaw.ca> wrote:

From: B. Seib <oldwheel at shaw.ca>
Subject: RE: [DeTomaso] Single or Dual Pass Radiators?
To: "Bill Gaino" <gaino at earthlink.net>, "Ken Green" <kenn_green at yahoo.com>, "Charles Engles" <cengles at cox.net>, "mark skwarek" <ehpantera at yahoo.com>
Cc: detomaso at realbig.com
Date: Tuesday, June 14, 2011, 6:16 AM

Theory aside, it does seem that either single pass or double pass types can be made to work acceptably in a Pantera as long as the rest of the system is in good shape and compliments the choice of radiator. I suspect the double pass system may reach its limitation sooner in racing situations and high HP at high temps. 
Barry

-----Original Message-----
From: mark skwarek [mailto:ehpantera at yahoo.com]
Sent: Monday, June 13, 2011 11:47 PM
To: 'B. Seib'; Charles Engles
Cc: detomaso at realbig.com
Subject: Re: [DeTomaso] Single or Dual Pass Radiators?

I have a Griffin radiator with two rows of 1.5" cores. 3" thick total. Griffin has this type of radiator rated for 600 to 1000HP. It is a single pass type and I have never had any problems with over heating.  I am using a 190 degree thermostat.

Mark

--- On Mon, 6/13/11, Charles Engles <cengles at cox.net> wrote:

From: Charles Engles <cengles at cox.net>
Subject: Re: [DeTomaso] Single or Dual Pass Radiators?
To: "'B. Seib'" <oldwheel at shaw.ca>
Cc: detomaso at realbig.com
Date: Monday, June 13, 2011, 11:31 PM

Dear Barry,

           Even after going through over 900 track photos, your succinct
summary of coolant basics makes sense and explains why the dual and triple
pass radiators don't seem to work in Panteras as well as they are expected.

                     Warmest regards,  Chuck Engles

-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
Behalf Of B. Seib
Sent: Monday, June 13, 2011 6:44 PM
To: DetomasoList; Ken Green
Subject: [DeTomaso] Single or Dual Pass Radiators?

Ken
This has been discussed to death several times before and agreement of all
parties was never achieved.
My opinion based on an analysis of The views I trusted most was that a dual
pass may have some small advantage in an idling/ traffic situation and the
single pass was better at high speed/load/HP. If you believe the "more flow
is better" theory, it's single pass. If you buy the theory that coolant
needs to spend a long time in the rad to shed more heat, maybe dual or
triple pass is for you.
Barry

Stewart Components and Evans Coolant are  "more flow is better" advocates:

http://www.stewartcomponents.com/tech_tips/Tech_Tips_5.htm

http://www.stewartcomponents.com/tech_tips/Tech_Tips_3.htm

quoting Stewart>>>>

Double pass radiators require 16x more pressure to flow the same volume of
coolant through them, as compared to a single pass radiator. Triple pass
radiators require 64x more pressure to maintain the same volume. Automotive
water pumps are a centrifugal design, not positive displacement, so with a
double pass radiator, the pressure is doubled and flow is reduced by
approximately 33%. Modern radiator designs, using wide/thin cross sections
tubes, seldom benefit from multiple pass configurations. The decrease in
flow caused by multiple passes offsets any benefits of a high-flow water
pump.

A common misconception is that if coolant flows too quickly through the
system, that it will not have time to cool properly. However the cooling
system is a closed loop, so if you are keeping the coolant in the radiator
longer to allow it to cool, you are also allowing it to stay in the engine
longer, which increases coolant temperatures. Coolant in the engine will
actually boil away from critical heat areas within the cooling system if not
forced through the cooling system at a sufficiently high velocity. This
situation is a common cause of so-called "hot spots", which can lead to
failures.

_______________________________________________

Detomaso Forum Managed by POCA

Archive Search Engine Now Available at http://www.realbig.com/detomaso/

DeTomaso mailing list
DeTomaso at list.realbig.com
http://list.realbig.com/mailman/listinfo/detomaso

_______________________________________________

Detomaso Forum Managed by POCA

Archive Search Engine Now Available at http://www.realbig.com/detomaso/

DeTomaso mailing list
DeTomaso at list.realbig.com
http://list.realbig.com/mailman/listinfo/detomaso