Essential cooling mods?

Florence_NC

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yes, I also notice since faster air is on top of the wing, the lines on top of wing should actually be depicted closer together, and thus the diagram is incorrect, but the caption is correct...and yes, per bernoulli's initial must equal final, thus all mass must be conserved. And yes, high pressure does want to move towards low pressure, just like higher electrical potential wants to move towards lower, and water wants to flow down hill.

the water hose analogy is to say that water should bounce off perpendicular to the windshield. yes, there are a rushing gush of water molecules trailing behind the initial once to case a "scatter" pattern, but by and large, much of the water should deflect perpendicular to the windshield; otherwise, we be all F-ed when we wash our cars correct??
The issue with the water hose is that a car sitting still or moving is in a continuum of air. Thus all the air in that continuum is subject to the properties of air, streamlines, flow regions, etc. When you spray water out of a jet, that water is not part of the continuum. It has a density, and thus momentum, that is orders of magnitude higher than the air in the continuum. So the much denser, higher specific energy water coming out of the jet defeats the properties of the continuum, simply pushes the air out of the way, and impacts the windshield.

Now put that car under water, where it is now existing in a continuum of water. Then stand 10 feet in front of the car and spray the water out of a jet towards the windshield. The water out of the jet is now part of the continuum of water, subject to the same laws and rules. So do you think, in the continuum of water, that the hose will impact the windshield and disperse the same way it did in air? What if you stood 10 feet in front of the car and sprayed a jet of air at the windshield, would that impact the windshield and disperse the same as the water in air?
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The issue with the water hose is that a car sitting still or moving is in a continuum of air. Thus all the air in that continuum is subject to the properties of air, streamlines, flow regions, etc. When you spray water out of a jet, that water is not part of the continuum. It has a density, and thus momentum, that is orders of magnitude higher than the air in the continuum. So the much denser, higher specific energy water coming out of the jet defeats the properties of the continuum, simply pushes the air out of the way, and impacts the windshield.

Now put that car under water, where it is now existing in a continuum of water. Then stand 10 feet in front of the car and spray the water out of a jet towards the windshield. The water out of the jet is now part of the continuum of water, subject to the same laws and rules. So do you think, in the continuum of water, that the hose will impact the windshield and disperse the same way it did in air? What if you stood 10 feet in front of the car and sprayed a jet of air at the windshield, would that impact the windshield and disperse the same as the water in air?
ok, point taken...however, air should still deflect off a passing windshield perpendicular to incoming angle?
 

charleswrivers

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Again, the system limit is Th.air as it passes over the radiator and heats up. Conductivity improvements are worth only a fraction. An improvement in Cp of the coolant will allow the coolant temp to remain slightly higher as it passes through the radiator, which slightly helps the dT issue. But only slightly. A bigger mdot.air is the only significant solution to this issue.
So far as conductivity... a way to know to determine whether to actually know what your Th.air is. It still should be something somewhat less than Tc.coolant… as it was still being a heat sink, albeit heated up from it's initial Tc.air temp. If there's still a substantial differential, then there's room to work to try and reject heat through a fluid that's more thermally conductive. It should be seen by seeing Th.air rising even further... and, like you said... if you pulled more heat off the engine, you could probably see Th.coolant initially go up. It's be an interesting experiment... but unless you are running hot with the thermostat wide open... you'd never see it... and with variables like your speed and engine load... I'm not sure how good of data you can collect other than just running back to back and watching your coolant temps. Again... it's a dollar to try (shrug). I also try cheap and easy first.

Improved convection by the grill mods/high flowing fans/better ducting just keeps chipping away at the problem. In the end... the end goal has got to be to get the cooling side heat transfer to air to exceed the heat input from the engine. The raise in heat capacity really would only serve to give you slightly more time until you hit limp mode. It's something... but not the end-all-be-all solution.

I'll have to look a bit and see if there's been some testing on initial vs final air temps across a radiator to see if there's anything out there... though every car is going to be somewhat different... and normal driving is certainly not going to be the same as driving on the track at 10/10ths. In the end, the current system just isn't rejecting the heat to air as fast as it's building. If we can't make the engine produce less heat... then we've got to get the heat into the air somehow.

Again, the water and overdrive pulley were brought up due to their lack of expense and them being used on vehicles in the past. I'm not sure how much ducting/shroud a CTR has between the fan(s) and radiator either. I've seen ducting mods being used to great effect on other forums for both radiators and intercoolers... with no change to the radiator/intercoolers themselves.

It's a neat problem to try and think about how to cure. Like you... I think swapping a radiator on a car without doing nothing things is taking money and throwing it at a part that just isn't going to be able to do much better than the stock one without some additional work... and that additional work might just make the stock radiator 'good enough'.
 

Florence_NC

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ok, point taken...however, air should still deflect off a passing windshield perpendicular to incoming angle?
So here is another angle to look at to make you think more about a continuum of fluid and what happens in it:

1) First, take the water hose in water (or air hose in air) example. These are operating in a continuum. When the air/water leaves the hose, the individual molecules in the jet impact the molecules in front of the jet, and transfer some or all of their momentum to those molecules. Then those hit the ones in front, then those hit the ones in front, etc. The effect of this is that the jet is diffused and damped by all of the impacts and mixing, so that what actually "hits" the windshield is not a bunch of molecules that originated from the jet, but a wave of pressure moving in front of the jet outlet. That wave is much more dispersed than the original jet, and there really is nothing that could be characterized as an "impact".

Also consider that the air/water molecules that actually make contact with the windshield contain almost none of the molecules that originally left the exit of the jet 10 feet earlier. There will be some molecules that were part of the original jet, but this is simply due to random mixing. The vast majority were not part of the original jet.

2) Now look at the water jet in air, that is the garden hose in the driveway. Virtually EVERY molecule of water that contacts the windshield was part of the original jet, the complete opposite of what happened in the continuum.

If you grasp the difference in these two scenarios, then you grasp the importance of considering fluid flows in a continuum.

And to answer your question about incoming/outgoing angle, the answer is yes, sort of, maybe, if the geometry and flow are within a range for that to be the outcome. In a fluid continuum, you are dealing with boundary conditions, which are heavily controlled by viscosity-induced damping. The air never truly "deflects" in the same sense as water from a garden hose deflecting, but rather the streamlines move around the object while maintaining zero velocity at the skin surface.
 

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So here is another angle to look at to make you think more about a continuum of fluid and what happens in it:

1) First, take the water hose in water (or air hose in air) example. These are operating in a continuum. When the air/water leaves the hose, the individual molecules in the jet impact the molecules in front of the jet, and transfer some or all of their momentum to those molecules. Then those hit the ones in front, then those hit the ones in front, etc. The effect of this is that the jet is diffused and damped by all of the impacts and mixing, so that what actually "hits" the windshield is not a bunch of molecules that originated from the jet, but a wave of pressure moving in front of the jet outlet. That wave is much more dispersed than the original jet, and there really is nothing that could be characterized as an "impact".

Also consider that the air/water molecules that actually make contact with the windshield contain almost none of the molecules that originally left the exit of the jet 10 feet earlier. There will be some molecules that were part of the original jet, but this is simply due to random mixing. The vast majority were not part of the original jet.

2) Now look at the water jet in air, that is the garden hose in the driveway. Virtually EVERY molecule of water that contacts the windshield was part of the original jet, the complete opposite of what happened in the continuum.

If you grasp the difference in these two scenarios, then you grasp the importance of considering fluid flows in a continuum.

And to answer your question about incoming/outgoing angle, the answer is yes, sort of, maybe, if the geometry and flow are within a range for that to be the outcome. In a fluid continuum, you are dealing with boundary conditions, which are heavily controlled by viscosity-induced damping. The air never truly "deflects" in the same sense as water from a garden hose deflecting, but rather the streamlines move around the object while maintaining zero velocity at the skin surface.
so in essence, the water hose inside water will not be a "projectile" (for lack of better term), but in free air, the water is a shooting stream...
 


Florence_NC

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so in essence, the water hose inside water will not be a "projectile" (for lack of better term), but in free air, the water is a shooting stream...
Projectile is not an improper word, just a bit of a layman's term. As long as you understand that it is a projectile because it is a non-continuum material, therefore it can't freely mix and exchange positions with the particles within the continuum.
 

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Projectile is not an improper word, just a bit of a layman's term. As long as you understand that it is a projectile because it is a non-continuum material, therefore it can't freely mix and exchange positions with the particles within the continuum.
the word "mixing" is key...
 

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86salmon

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Hood venting and cowl induction also work based on venturi and coanda principles. Placement and size is key to effectiveness
 


Florence_NC

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Hood venting and cowl induction also work based on venturi and coanda principles. Placement and size is key to effectiveness
Hood venting, depending on placement and design, could have some Coanada element to the flow.

Cowl pressure is strictly a function of Bernoulli. The cross sectional area of the flow increases, which decreases velocity and increases pressure. If significant Coanda was present at the cowl, then the pressure above the cowl would be lower, not higher.

I don't think you can really characterize either of these as being venturi. Venturi effect is a specific application of Bernoulli where flow is moving through a closed flow region, such as a pipe or duct, with varying cross-sections to produce pressure differentials. Air moving over a car is a single-sided flow region, with the vehicle acting as the closed surface on one side, and the free air being the open side.
 

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the word "mixing" is key...
Yes, mixing is a critical part of this, assuming we are talking about fluids.

Air is a mix of different molecules, each with different characteristics. When 2 nitrogens hit each other, they act differently than 2 oxygens. And a C02 hitting an argon acts way different. But taken at volumes large enough for the individual differences to be filtered out, it acts like a continuous homogeneous fluid.

If you were to inject something radically different from the jet, like maybe helium, then it gets a bit nuanced. Helium is much lighter, and has very different inter-molecular properties. But it does still mix readily with air. So initially out of the jet, it may not act purely as a continuum. But after sufficient time/distance from the jet, the mixing becomes thorough enough to now act as a continuum.

Keep in mind that a continuum can also be a solid, so mixing is not a consideration here. A set of molecules is bound into a continuous solid, and those bonds maintain (more or less) the same attachment to the same adjacent molecules. They can move in distance, stretching and compressing the bonds, but the bonds stay intact. This is clearly not mixing.

A tire is a continuum of rubber, if you press something into the tread, the molecules in contact will deflect, which deflects the ones next to it, etc, etc. Once you get sufficiently far away from the initial point of deflection all of the deflection has been damped and dissipated, molecule by molecule, until no effect is seen.

A brick is a continuum, and acts just like the rubber, only the distance of deflection is many orders of magnitude smaller.
 

86salmon

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I don't think you can really characterize either of these as being venturi. Venturi effect is a specific application of Bernoulli where flow is moving through a closed flow region, such as a pipe or duct, with varying cross-sections to produce pressure differentials. Air moving over a car is a single-sided flow region, with the vehicle acting as the closed surface on one side, and the free air being the open side.
Fair enough. I was thinking along the lines of introducing air entrainment
 

86salmon

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Air entrainment is a different thing. Entrainment is part of the Coanda effect, which would not exist without viscosity.
Venturi devices specifically entrain air. I use them on a daily basis for blending oxygen...
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