THE next true street car build
07-24-2014, 06:52 PM
#45
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David, from what i've learned over the years, its the length AND size of the restriction WITH REGARDS to water flow that make the largest difference.
When im calculating flow AND ft/hd (restriction) in a hydrulic/water system, i dont simply calculate the "smallest" single point. Obviously, the fittings are normally the smallest, but they are a tiny part in the overall flow restrection... Like in my line of work, the math we use suggest that every X amount of fittings equals Z amount of pressure drop/restriction.
I have 1" piping on BOTH inlet and outlet of my radiator and NEVER have problems with the plumbing.
TO reference, i do Geothermal design calculations for a living, i have to calculate flow and pressure needed to achieve a certain goal and ALL of my calculations are based on distance and not a SINGLE or 1" long small restriction.
I Know that a very short restriction would make a larger difference in a shorter overall distance, but with my overall mathematical findings, the length of the restriction makes a larger difference.
I have not cut open a water pump, but i bet that the flow path isnt all that impressive.
Which leads me to believe that the OEM using larger tubing is to NOT add to the overall pressure drop.
Now lets add some thermodynamics to this.
The faster you can move fluid through a heat exchanger, the more heat you can scrub.
This is a balancing game too
When im calculating flow AND ft/hd (restriction) in a hydrulic/water system, i dont simply calculate the "smallest" single point. Obviously, the fittings are normally the smallest, but they are a tiny part in the overall flow restrection... Like in my line of work, the math we use suggest that every X amount of fittings equals Z amount of pressure drop/restriction.
I have 1" piping on BOTH inlet and outlet of my radiator and NEVER have problems with the plumbing.
TO reference, i do Geothermal design calculations for a living, i have to calculate flow and pressure needed to achieve a certain goal and ALL of my calculations are based on distance and not a SINGLE or 1" long small restriction.
I Know that a very short restriction would make a larger difference in a shorter overall distance, but with my overall mathematical findings, the length of the restriction makes a larger difference.
I have not cut open a water pump, but i bet that the flow path isnt all that impressive.
Which leads me to believe that the OEM using larger tubing is to NOT add to the overall pressure drop.
Now lets add some thermodynamics to this.
The faster you can move fluid through a heat exchanger, the more heat you can scrub.
This is a balancing game too
07-25-2014, 09:27 AM
#46
great info jax. i appreciate the professional input, tho i am not sure where it takes me hmm..
in my reading the hoses are large so that speed is slow and cavitation is kept to a minimum.
that jives considering how close to the boiling point things already are
interesting fluid flow calculator here
http://www.gates.com/catalogs-and-re.../pressure-drop
in my reading the hoses are large so that speed is slow and cavitation is kept to a minimum.
that jives considering how close to the boiling point things already are
interesting fluid flow calculator here
http://www.gates.com/catalogs-and-re.../pressure-drop
07-25-2014, 08:43 PM
#47
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Cavitation would only happen if there was air in the system, i suppose if it all vaporized and turned to steam, but thats unlikely to happen
We all try to rid the systems of air, as that causes pockets and expansion(Pressure).
If your rad is in the standard place, i woulndt get hung up on tubing size. Just use the largest you can fit or use or have or can afford, whatever.
For fun, i'd love to see the actual curve of the GM pump. I could probably rig one up with a pressure gauge and flow meter and make a curve. Would be fun.
A valve, and then a guage, and then a flow meter would tell you what that pump could move for water at what pressure. Use the valve to simulate restriction and measure the output in GPM. I may have to try it.
We all try to rid the systems of air, as that causes pockets and expansion(Pressure).
If your rad is in the standard place, i woulndt get hung up on tubing size. Just use the largest you can fit or use or have or can afford, whatever.
For fun, i'd love to see the actual curve of the GM pump. I could probably rig one up with a pressure gauge and flow meter and make a curve. Would be fun.
A valve, and then a guage, and then a flow meter would tell you what that pump could move for water at what pressure. Use the valve to simulate restriction and measure the output in GPM. I may have to try it.
Last edited by JAX04; 07-26-2014 at 09:45 AM.
07-28-2014, 01:17 PM
#54
Cavitation would only happen if there was air in the system, i suppose if it all vaporized and turned to steam, but thats unlikely to happen
We all try to rid the systems of air, as that causes pockets and expansion(Pressure).
We all try to rid the systems of air, as that causes pockets and expansion(Pressure).
Essentially the water in the cooling system is so hot that when the pressure at the inlet of the pump drops due to the suction of the pump, the boiling point is reduced to the point where a phase change happens and the fluid flashes to vapor. Then when the vapor bubbles reach the vanes of the water pump the pressure starts to increase due to the transfer of kinetic energy from velocity to pressure which causes the vapor bubble to collapse and pit the impeller. This also drastically reduces the efficiency of the pump.
It is prevented by ensuring adequate pump head to the suction of the pump to maintain the suction pressure higher than the saturation pressure.
Sorry to interrupt the thread.
BADASS car. Will be watching this one for sure.
07-29-2014, 12:54 AM
#55
Air has nothing to do with cavitation. Cavitation is the formation and subsequent collapse of vapor bubbles, caused by a drop in the pressure of the fluid below saturation pressure and a subsequent rise in pressure back above saturation pressure.
Essentially the water in the cooling system is so hot that when the pressure at the inlet of the pump drops due to the suction of the pump, the boiling point is reduced to the point where a phase change happens and the fluid flashes to vapor. Then when the vapor bubbles reach the vanes of the water pump the pressure starts to increase due to the transfer of kinetic energy from velocity to pressure which causes the vapor bubble to collapse and pit the impeller. This also drastically reduces the efficiency of the pump.
It is prevented by ensuring adequate pump head to the suction of the pump to maintain the suction pressure higher than the saturation pressure.
Sorry to interrupt the thread.
BADASS car. Will be watching this one for sure.
Essentially the water in the cooling system is so hot that when the pressure at the inlet of the pump drops due to the suction of the pump, the boiling point is reduced to the point where a phase change happens and the fluid flashes to vapor. Then when the vapor bubbles reach the vanes of the water pump the pressure starts to increase due to the transfer of kinetic energy from velocity to pressure which causes the vapor bubble to collapse and pit the impeller. This also drastically reduces the efficiency of the pump.
It is prevented by ensuring adequate pump head to the suction of the pump to maintain the suction pressure higher than the saturation pressure.
Sorry to interrupt the thread.
BADASS car. Will be watching this one for sure.
07-29-2014, 01:03 PM
#57
thanks guys.
we still have NOT ruled out some form of a/c
to be conservative i will be moving forward with -20 for both ends of the water pump/rad since that is oem size(ish)
i am planning to have it running in some form this year, competition incredibly unlikely
gcg the car will definitely need painting but i am still leaning toward wrap at the moment due to cost and maintenance.
we still have NOT ruled out some form of a/c
to be conservative i will be moving forward with -20 for both ends of the water pump/rad since that is oem size(ish)
i am planning to have it running in some form this year, competition incredibly unlikely
gcg the car will definitely need painting but i am still leaning toward wrap at the moment due to cost and maintenance.
I can do the labor just need a hook up on the product. 