Thermodynamic hydraulic debate. (Trans fluid cooler)

[RacinDuallie]

I'm in this debate with the owner of local speed shop that I support.

Picked up bunch of AN fittings to hook up trans fluid cooler.

He questioned why I was jumping the size up to -10AN.

Then proceeded to tell me I'm wasting my time and asked why?

Told him bigger so it has more time in cooler to cool.

Said I am an idiot, that hydraulic pressure is hydraulic pressure. Said everything I'm doing by stepping up to -10 inlet/outlet plus -10 cooler, is waste.

Let's hear it from the more smarter peeps than me.

[jasonc]

The return hole size into the trans is the main factor, but I'm with y'all on the low pressure/high volume flow thru the cooler.

I run all #8 on my setup.

[thatguy69]

regardless using -8 vs -10 gives you more volume which is what your after. whether its worth it or not I don't think so.i used a b&m plate cooler in the factory location and a derale 15870 under the bed and it runs cool as a kitten,almost too cool. pulling a 14k this summer when it was 90+ out my temp never got over 180. without a trailer it never gets over 140 in the summer and its hard to hit that

[jasonc]

With 3/8" ID fittings?

[RacinDuallie]

Originally Posted by thatguy69

regardless using -8 vs -10 gives you more volume which is what your after. whether its worth it or not I don't think so.i used a b&m plate cooler in the factory location and a derale 15870 under the bed and it runs cool as a kitten,almost too cool. pulling a 14k this summer when it was 90+ out my temp never got over 180. without a trailer it never gets over 140 in the summer and its hard to hit that

My plan was to follow what my buddy has on his triple turbo drag truck. -10 lines to -10 cooler/fan/thermostat setup.

Although since I'm streeting this one I questioned running two cooler/fan setups??

Was told -6 is fine. But under the assumption that more is more better.

Then the Speed Shop owner was making it like I am stupid..... .

[RacinDuallie]

This is the concoction I have.

Fitting into trans, -6 AN fitting to -8, -8 to-10 fitting.

[Tobin]

The larger diameter line actually keeps pressure up at the cooler (less restriction) and slows down velocity of the fluid. Yes, the ports on the transmission are restrictive, so at some point you are hitting the point of diminishing returns.

I drilled out my NPT to AN adapters some, they neck down pretty good.

Stacked plate cooler is what you want.

I would definitely go at least a -8 line, -10 is even better.

[RacinDuallie]

So if I used a smaller diameter line/ cooler the fluid spends less time in the cooler, whereas the larger diameter lines /cooler has a larger volume of fluid therefore this larger amount of fluid stays in the cooler longer which means the inlet temp should be cooler......

[crackerman]

Not quite so much in the lines, the cooler, yes. The more time the fluid spends in the cooler, the more heat is exchanged.

The smaller the line,the faster the fluid gets to the cooler.

[jasonc]

What is the pressure thru the cooler lines on a 47/48 trans with 200psi line pressure?

[T-MAN]

I would say that depend on the line size you use from the trans, bigger the line the greater the pressure drop....

[12valve95]

Originally Posted by crackerman

Not quite so much in the lines, the cooler, yes. The more time the fluid spends in the cooler, the more heat is exchanged.

The smaller the line,the faster the fluid gets to the cooler.

So by this thinking, wouldn't you want a smaller line going to the cooler and a bigger line coming from to allow maximum time in the cooler?

[Chassisman]

A larger line flows more fluid. Unless there is a pressure drop it moves more not less. IE when you go from a 2 in water pipe to a 2.5 inch pipe the flow almost doubles!

[zstroken]

If you use a larger line to and from the cooler, the fluid will spend less time in the cooler.

[T-MAN]

Originally Posted by zstroken

If you use a larger line to and from the cooler, the fluid will spend less time in the cooler.

when you increase the line size from the trans you also have a pressure drop, this increases the volume and slows the velocity, it can only displace the fluid so fast with the bigger lines.... so it will spend more time in the cooler.

[Tate]

Originally Posted by T-MAN

when you increase the line size from the trans you also have a pressure drop, this increases the volume and slows the velocity, it can only displace the fluid so fast with the bigger lines.... so it will spend more time in the cooler.

If you're looking at it from a fixed displacement pump, then you would be correct about the higher velocity. But if you have a .5 sq.in. hose at 20 ft/sec, or a 1 sq.in. hose at 10 ft/sec, your flow rate is still the same. Flow is what you're concerned with through the cooler, not the velocity

If we're looking at it from a fixed pressure view (which I'm thinking is more likely the scenario, but autos are voodoo to me), the bigger line will have a similar velocity and more flow. If the cooler doesn't add any appreciable restriction to the system, then the oil will go through the cooler faster and come out hotter. It'll likely shed the same amount of thermal energy, but it'll be more oil cooled to a higher temperature.

Seems like to me that if you're smallest fittings are -6, going to a -10 won't change the flow rate much through the cooler, just the velocity in the lines.

[T-MAN]

Originally Posted by Tate

If you're looking at it from a fixed displacement pump, then you would be correct about the higher velocity. But if you have a .5 sq.in. hose at 20 ft/sec, or a 1 sq.in. hose at 10 ft/sec, your flow rate is still the same. Flow is what you're concerned with through the cooler, not the velocity

If we're looking at it from a fixed pressure view (which I'm thinking is more likely the scenario, but autos are voodoo to me), the bigger line will have a similar velocity and more flow. If the cooler doesn't add any appreciable restriction to the system, then the oil will go through the cooler faster and come out hotter. It'll likely shed the same amount of thermal energy, but it'll be more oil cooled to a higher temperature.

Seems like to me that if you're smallest fittings are -6, going to a -10 won't change the flow rate much through the cooler, just the velocity in the lines.

This is what Jeff is after....


If we start with a 3/8 outlet at the case of the transmission with lets say 70psi. we jump to a 5/8 diameter line we should have a pressure drop. the 5/8 line goes through a plate style cooler with 5/8 inlet and outlet and returns back to the transmission through a 3/8 fitting dumping into the pan. Ill add that before the original 3/8 fitting the passages in the trans are about 1/4 "


wouldn't the increased area of the bigger line plus the pressure drop slow the velocity and allow more time for the cooler to do its job? Also if we maintained the original pressure (restriction) this would build heat, so wouldn't replacing pressure with volume be a good thing? Nice reply by the way....T-MAN

[biggy238]

'More time in the cooler' is conjectural.

If there was no restriction of the fluid return, yeah, the interaction of the fluid to the cooler surface would potentially increase.

But that isn't the case here. You are only going to flow what the orifice back into the case will allow.

That doesn't make any mention of laminar flow. Interaction of the fluid in the cooler is determined by how many changes in direction it makes. This is where the suggestion of bar plate coolers comes from. On most tube and fin coolers, the path of least resistance dictates that only a percentage of the core handles the majority of the fluid flow. Some designs use a single path design on their tube and fin coolers to eliminate that. (typical trans cooler of PS cooler)

Why Laminar Flow is AWESOME - Smarter Every Day 208 - YouTube

Sent from my SM-G950U using Tapatalk

[T-MAN]

Jeff didn't put that it was with a bar and plate cooler. would they cool the same if ?

A- 3/8 fitting to 3/8 line, then 5/8 cooler inlet on bar style cooler to 5/8 outlet, back to 3/8 line to trans.
B- 3/8 fitting to 5/8 line all the way back to the trans with a 3/8 fitting on the trans.

[zstroken]

Originally Posted by T-MAN

when you increase the line size from the trans you also have a pressure drop, this increases the volume and slows the velocity, it can only displace the fluid so fast with the bigger lines.... so it will spend more time in the cooler.

When you increase the line size on the supply and return line, you will have less pressure drop on both of those lines. There for you will have less overall resistance in the circuit, which means you will flow faster. We are making the assumption that the cooler is the greatest restriction in that circuit(which is a good assumption).



The increased line size will slow the velocity only in the supply and return line. You still running through the same cooler.


If you really want to get technical when you do this type of thing you need to look at the pump curve. I am going to make an assumption that the supply pressure from the trans is constant.