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  1. #41
    Contributing Member DaveW's Avatar
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    Quote Originally Posted by Marty Nygard View Post
    ...
    If you want specific instances of statements I believe to be wrong, "The faster the air flows through the radiator, the cooler it stays on its way through, enhancing heat transfer, and the thinner any boundary layers will be". Almost all air flow through the core will be fully turbulent (see definition of Reynolds number). This does not mean that all air flowing through the core will contact the fins to convect heat from them. Fin type, fin spacing and core depth also enter into the performance. That's why space velocity has such a large effect on the heat transfer coefficient.
    Marty
    Thanks, Marty. I'm sure you are correct in your assessment of my overstating my case.

    However, would you agree or disagree that in most cases, for general application, my statement in bold would be directionally correct more often than not?
    Dave Weitzenhof

  2. #42
    Contributing Member Jnovak's Avatar
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    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)

  3. #43
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    Quote Originally Posted by Neil_Roberts View Post
    A thought experiment for discussion:

    The performance of a series radiator configuration is (or is not) equal to a parallel configuration with the water flow through both cores changed to double pass.

    Which is correct, and why?

    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

  4. #44
    Contributing Member DaveW's Avatar
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    Quote Originally Posted by Marty Nygard View Post
    ...I suggest re-reading the three Carroll Smith books; especially Chapter 8 of Prepare to Win...
    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

  5. #45
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    Quote Originally Posted by LJennings View Post
    • And my math is correct after Christmas dinner

    Liquid or solid?

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