In any cooling system, a very important consideration is the temperature differential between the hot water and the cooling air. This is a key factor in the heat transfer equation.
In a serial flow system with 2 radiators the hot water temps in radiator 1 will be significantly higher than in radiator 2 as the water is cooled in rad 1 before going to rad 2. This significantly reduces the effectiveness of rad 2.
I have built and tested both types of systems on several different cars and have found that both types can be effective with the parallel system having a very decent edge IF and ONLY IF the flows in both systems are equal and the flow velocites are adequate. Equalizing the flows Is easily measured and can provide an optimum parallel rad system.
The BIG downside of a parallel system is the complexity of the plumbing with a serial system winning out every time for this factor.
If you want the maximum cooling capacity, say for a 2 stroke engine, then a properly done parallel system will provide lower inlet temps but the system will be more complex.
Thanks ... Jay Novak
313-445-4047
On my 54th year as an SCCA member
with a special thanks to every SCCA worker (NONE OF US WOULD RACE WITHOUT THE WORKERS)
A few assumption first.
- Both radiators have the same fluid flow area (A)
- Both radiators are manufactured the same
- The flow of the water pump does not change (Q)
- A very simplistic view of the "system" - NO FRICTION!
- And my math is correct after Christmas dinner
Based upon the Continuity equation Qin = Qout, therefore Q=AV or Q1 = Q2 OR A1V1=A2V2, and based on physics V=d/t
So for a series system the Qin is the same as Qout, the area is the same, so the Vin and Vout must be the same.
For the Parallel system assume only 1/2 Qin for each radiator, and since A is the same, therefore V = 1/2.
Now with the double pass = twice the distance so V= 1/4
So the Parallel double pass system is not the same as the Single pass series system.
Last edited by LJennings; 12.26.13 at 12:41 PM. Reason: Spelling typos
I have read all of this series, some of it several times. While it is mostly very good, I have found some areas where the advice is not totally correct (a long time ago, so I don't remember where specifically).
So, like anything (including, of course, things that I post ), the Carroll Smith books need to be read with an open and critical mind, and not followed by rote.
Dave Weitzenhof
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