Evans Waterless coolant in V6/V8s?

Discussion in 'General Auto Conversion Discussion' started by pfarber, May 23, 2019.

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  1. Jul 21, 2019 #101

    Sockmonkey

    Sockmonkey

    Sockmonkey

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    There's an optimal range of flow rates for best heat transfer.
    What I think pictsidhe is getting at is that being outside that range on the high end is just as bad as being outside it on the low end.
    The coolant has to be in contact with the thing it's cooling for long enough to absorb heat from it, which won't happen if the coolant zips through too fast.
     
  2. Jul 22, 2019 #102

    poormansairforce

    poormansairforce

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    So your planning on more than 30-40 hp at idle?
     
    Last edited: Jul 22, 2019
  3. Jul 22, 2019 #103

    pictsidhe

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    At the ratio of engine to cooling air we need, flowing too much coolant is not a very big penalty, but it's one we don't want if we are already overheating...
     
  4. Jul 22, 2019 #104

    pictsidhe

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    No, increasing the coolant flow past the optimum rate does not increase cooling. It will actually reduce it. What I don't understand why you don't read the stuff I posted. If you check the maths, I guarantee that you will learn something.

    5gpm coolant flow will optimally cool an engine idling at somewhere around 5g/hr fuel flow with a 40K delta across the radiator air. How big is your engine? That's enough flow to cool an engine efficiently turning out around 70hp. You are flowing 140cfm through the radiator to take maximum advantage of the 5gpm coolant flow rate?

    22gpm is good for cooling north of 300hp. If you need that much coolant flow at idle, I can only assume that you will be running a Merlin?

    If you can't do the maths or the experiment, it's pretty pointless arguing with anyone who not only can, but has done both math and experiment and then applied the acquired knowledge. I wasted time making a spreadsheet so that you don't need to do the math or experiment. Maybe some of the smarter members can use or learn from it.

    Yes, I have designed and built a liquid coupled heat exchanger that worked as I predicted. Centrifugal pumps, too. I've even mitigated tuned car cooling problems using exact opposite techniques to what you propose. Hence my attempts at explaining why they won't be helpful. I therefore don't place much value in your hot-rod magazine article. I've found their information to be very inaccurate in the past. My favourite was the 'technical expert' article on how cooling induction air from 80C to 40C would double it's density...

    You'll find that Darwin has historically had an extremely low tolerance for aeronautical experimenters who didn't do the maths for one reason or another. You will ignore me, but others may listen.
     
    Last edited: Jul 22, 2019
  5. Jul 23, 2019 #105

    Winginitt

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    Here Here.....Point of Order

    If nothing else gets resolved in this thread, can everyone at least stop saying that the flow provided by the stock water pump is insufficient at any useful rpm. That is every rpm range from idle to say 5000 rpms. Stock from the factory the belt driven water pump routinely satisfies the needs of everything from large industrial trucks pulling heavy loads and trailers up steep grades in Arizona's 100+ degree temperatures to Corvettes cranking out over 500 HP as they burst on to the on ramp. My son was stationed in AZ for 10 years and pulled a camping trailer up steep grades on Hwy 10 with his extended cab 5.3 liter Chevy truck. He had his 4 family members, his dogs and a lot of other stuff, air conditioning running full tilt, and booking down the highway with his buddies in their trucks.
    The LS engines are installed in 3500 series industrial trucks, and I have a 2008 LY6 from one of those industrial trucks that I'm installing in a lighter 56 Chevy truck. None......I repeat....None of these engines ever overheats because there is insufficient water flow thru the internal passages of the engine when the factory engineered system is operating properly.
    When a problem occurs, it is because something has failed to disperse the heat on the air side of the system, or something like a hose or thermostat is impeding flow. I think everyone needs to accept the premise that flow
    "Thru the engine passages is sufficiently engineered and proven " by the factory in extreme conditions. Ponder that the next time you are sitting in traffic during this heat wave with your engine idling and the A/C cooling everyone inside......without overheating.

    It doesn't matter what the actual flow number is, it is sufficient. So can we agree on that one point?
    In stock form an LS engines factory water pump does provide sufficient flow........
     
    Last edited: Jul 23, 2019
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  6. Jul 23, 2019 #106

    AdrianS

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    Assuming you're running a belt-driven alternator, running the water pump off that belt has the fewest failure modes.
    Yes, belt-driven pumps are slightly less efficient than speed-controlled pumps, but they last 20,000 km or more in automotive service, tend to fail progressively, and are cheap enough to replace as a service item.

    That is true regardless of cooling fluid .
     
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  7. Jul 27, 2019 #107

    pfarber

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    Yes, but we ARE NOT USING THE SAME RADIATOR. So no, I don't care what your cousin/uncle/sister ran in her 350. That engine radiator is to big to push through the air.

    For my 200hp (derated from 285hp) LV3 engine its calculated that a 20x20x1 (400cu/in) radiator should work. The STOCK 4.3 Silverado radiator is 34 x 17 x .87 (502 cu/in). So this is why comparing car engines to aviation needs DOES NOT WORK. The car install has 20%+ more size. Why? Because cooling at idle/low speed is a big part of a car engine's life. And having that extra weight is not a huge issue. Try to push that extra 20% volume at 200kts and tell me how it works out for you. Y

    So we need to OPTIMIZE the cooling system for worst case. Worst case is NOT cruise. Worst case is taxi and then climb out. At idle during taxi the need to move coolant from the engine to the radiator is critical. No matter what any spreadsheet says, unless you get the heat to the exchanger, you cannot get rid of it. In a car, dual radiator fans, shrouds and oversize radiators are not a big deal. In an aircraft all that weight and drag IS A BIG DEAL. Dwell time of the coolant in the radiator is not a critical factor. Ambient temps and mass of airflow is.

    I'll leave this here (yes, its about cars, but the basics are still applicable).

    http://www.superchevy.com/how-to/project-cars/sucp-1204-cooling-system-basics

    Water Flow
    Coolant flow is usually the last aspect of the cooling system to be addressed. Ironically, it's also the usual cause for overheating problems. A typical stock water pump has excessive clearance and straight impeller blades, usually open front and back. With the engine running at low rpm, this produces little coolant flow and is typically responsible for cars overheating in traffic at idle speed. At high rpm, this design will cause cavitation and aeration, which can also cause the coolant flow to be reduced to the point of engine overheat. A common Band-Aid fix for this problem is to run underdrive pulleys, which slows down the revolutions of the water pump/impeller. While the high-rpm cavitation problem is solved, this solution usually contributes to a low-rpm overheat problem because the water pump isn't turning fast enough. With an engine-driven water pump, the only remedy is an aftermarket race-style pump with tight clearances and a swept-blade, closed-impeller design

    Electric water pumps are a highly effective solution to these problems with multiple benefits. The constant speed of an electric pump eliminates high-rpm cavitation problems and low-rpm insufficient flow issues. An added bonus is being able to run the pump when the engine is shut off, especially useful racing applications. (my edit - additional benefit is NO THERMOSTAT IS POSSIBLE)

    The third benefit is the elimination of parasitic horsepower loss from the engine having to turn the water pump off the crankshaft.

    So again, all things equal, with the OPTIMUM sized radiator, well designed ducting, the last part of the puzzle is the movement of coolant.

    Synthetic coolant is not the best for pure heat transfer, but the trade off is that I can ELIMINATE the t-stat and run an unpressurized system with a significantly higher boiling point (eliminate steam pockets).

    This has all been done before. Nothing is new except that 'airplane' replaces 'car' in the description.

    EDIT: There is also the fact that heat exchanger efficiency goes UP with a large temp differential between the coolant and the air. Slow moving coolant defeats this. First, the BTUs simply never gets to the radiator. Second, the longer the coolant stays in the radiator, the less the temp delta is. So there is an optimum coolant flow rate for taxi. With a radiator size reduced for use in an airframe, moving more coolant through the radiator keeps the temp differential high an therefore transferring more BTUs from the engine to the radiator and into the air. An electric water pump give you the variable GPM (not to mention just flat out higher GPM) than a mechanical pump tied to engine RPM.
     
    Last edited: Jul 27, 2019

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