SVX Engine cooling "Again & Again"

[amber]

Originally Posted by Dessertrunner

With out try to baffle you with Bull____T the rule is,
"Greater the difference between the coolant and the block for a given flow the greater the transfer of heat from the block in a give time"

Hope that helps.
Tony

I have been reading this thread for some time in conjunction with Trevor because he has often asked me to give my opinion re what he has been posting.

He has tried to make it clear that "Time" is essential and part and parcel of any form of cooling. Would anyone expect too hot coffee to cool instantly? No, they leave it and give it time to cool. Those who have rubbished what he has posted should now read it all again and have another think.

[svxfiles]

Originally Posted by Boxersix

If people want I can fab a few of these 50mm pump inlets for those looking to do this. Will be a straight lip, you'll just have to modify your radiator to suit and use an appropriate 2" ID hose.

Sending a PM.

[Johnybeas]

Originally Posted by Boxersix

I have a 170F thermo in it. Normal temp while driving fully warmed is 168-175 pending vehicles speed. On the dyno it creeped to 186F after a minute of constant running, then held steady until I took my foot off the throttle some odd 60-80 seconds later

If people want I can fab a few of these 50mm pump inlets for those looking to do this. Will be a straight lip, you'll just have to modify your radiator to suit and use an appropriate 2" ID hose.

I'd be down, since I'm not quite sure what part needs to be modified, I can modify my PWR but the pump inlet?? not sure how I'd do it without pics, but I'd rather work on headers and CAI's and Turbo kits... so I'll let you do the pumps

[Dessertrunner]

Amber hate to disagree with you but I can cool a cup of coffee to freezing in less the 5 seconds. Its all about heat transfer rates and how cold the surrounding enviroment is.
I don't want to go down the slowing coolant flow direction again, a no time did Trevor provide me with the maths to prove what he was saying just abuse. Heat transfer rates are known & proviable with maths, we have left the dark ages so lets stay with the modern times.
Have a great day everyone.
Tony

[1986nate]

Originally Posted by amber

I have been reading this thread for some time in conjunction with Trevor because he has often asked me to give my opinion re what he has been posting.

He has tried to make it clear that "Time" is essential and part and parcel of any form of cooling. Would anyone expect too hot coffee to cool instantly? No, they leave it and give it time to cool. Those who have rubbished what he has posted should now read it all again and have another think.

As Tony said, you put the coffee in the fridge to cool down, and it takes less time... pretty simple concept. That's one thing in this thread I can easily understand

[amber]

Tony I see that even though you hate to, you have now agreed in two posts that heat transfer does take time and that it will take you time to even miraculously quickly freeze your cup of coffee. You also show that you know about heat transfer rates, and that there is a rate of heat transfer and must therefore understand that the word “rate” as used means the time involved for heat to transfer.

Mathematics are not required for Trevor or I to show that it takes time for the engine to heat the coolant and for the radiator to cool the coolant, and that the cooling area exceeds the heating area, so that a situation must arrive where the coolant can be moving too fast for optimum cooling.

If you require figures of any sort you must give us the exact contact areas and flow resistance for both engine and radiator and also the flow rate as is related to engine speed. You will no doubt understand that a variable fluid velocity at two points in the system is involved. On top of that airflow enters the picture. How is your maths?

The important negative factor of fluid turbulence particularly within the engine, as a result of speed of flow (velocity) also pointed out by Trevor we will stay clear of for the moment.

I can not find where Trevor has been “saying just abuse”, please show me where he has done this.

I leave you to have a great day with everyone.


1986nate mate.

Thank you very much for also pointing out that it is a “pretty simple concept” to understand that it takes time for something to heat or cool. Yes the transfer of heat takes time, just what Trevor has been saying to a brick wall on and on and on. How hard is it for you lot to conceive. Interesting word that. LOL.

Joe Foy

[Dessertrunner]

Good give me peace.
Tony

[amber]

I see that you are unable to show how and where Trevor has been “saying just abuse”. I leave you to untangle your piece of thread.LOL Hot air is sure to be cheap when running in the desert. I am off, it is a nice day here and my daughter needs a hand with her horses. Cool off peacefully. LOL again. Joe.

[shotgunslade]

The notion that a greater flow rate through the radiator reduces cooling because the "coolant" doesn't have time to cool is totally wrong.

The radiator can be considered a cross flow heat exchanger. Heat transfer between the water and the air is a function of time, the fixed heat transfer area of the radiator and the logarithmic mean temperature difference between the air and the water. For the sake of simplification, we can consider the temperature of the air fixed, because we aren't worried for the moment about varying air flow, although the same arguments will hold for varying air flow that hold for varying water flow.

The greater the velocity of water through the radiator, the lower the temperature drop of the water. However, if the change in the heat transfer coefficient between the water and the radiator tube walls is ignored, the heat transferred from the water out the radiator is the same, despite the increased velocity because the greater velocity results in a greater mass flow. The two offset one another.

Q = M * U *p * deltaT

where:
Q = heat flux
M = mass flow rate
U = heat transfer coefficient
p = specifc heat
deltaT = logarithmic mean temperature difference.

Greater fluid velocity through the radiator, however, increases the heat transfer coefficient between fluid and radiator tube wall because the greater velocity erodes the static boundary layer between tube wall and flowing fluid. It is exactly the same phenomenon as wind chill factor. Increased air velocity (wind) erodes the boundary layer around your body, increasing the heat transfer coefficient, thus increasing heat transfer between your body and the air. Nobody ever claims that increasing wind speed makes you feel warmer because the faster moving air doesn't have time to heat up as it blows past you.

It is true that, with a greater coolant velocity through the radiator each cubic inch of coolant going through the radiator loses less heat and thus has a lower temperature drop, but the greater velocity also moves more cubic inches through the radiator per unit of time, so there is a greater mass losing heat.

The increased heat transfer coefficient between the fluid and the radiator tube wall actually results in a slight increase in heat loss through the radiator with increasing fluid velocity

Trevor never got this, and was adamant and even abusive in his defense of his own ignorance. This is basic fluid mechanics. It is not a theory.

I believe that very likely cause of the high rpm overheating problem has to do with local boiling. In some cases it is caused by cavitation at the pump inlet, intermittent disruption of the water pump flow because it is momentarily vapor locked, then local boiling. It also might be due to unbalanced fluid flow across the two sides of the engine. I just know that between the improved cross-over tube, and moving the thermostat out of the water pump inlet, my problem was solved.

[SVXRide]

Another excellent lesson in fluid mechanics from Professor Dan! Thanks for another flashback to my junior year of engineering school!
-Bill

Originally Posted by shotgunslade

The notion that a greater flow rate through the radiator reduces cooling because the "coolant" doesn't have time to cool is totally wrong.

The radiator can be considered a cross flow heat exchanger. Heat transfer between the water and the air is a function of time, the fixed heat transfer area of the radiator and the logarithmic mean temperature difference between the air and the water. For the sake of simplification, we can consider the temperature of the air fixed, because we aren't worried for the moment about varying air flow, although the same arguments will hold for varying air flow that hold for varying water flow.

The greater the velocity of water through the radiator, the lower the temperature drop of the water. However, if the change in the heat transfer coefficient between the water and the radiator tube walls is ignored, the heat transferred from the water out the radiator is the same, despite the increased velocity because the greater velocity results in a greater mass flow. The two offset one another.

Q = M * U *p * deltaT

where:
Q = heat flux
M = mass flow rate
U = heat transfer coefficient
p = specifc heat
deltaT = logarithmic mean temperature difference.

Greater fluid velocity through the radiator, however, increases the heat transfer coefficient between fluid and radiator tube wall because the greater velocity erodes the static boundary layer between tube wall and flowing fluid. It is exactly the same phenomenon as wind chill factor. Increased air velocity (wind) erodes the boundary layer around your body, increasing the heat transfer coefficient, thus increasing heat transfer between your body and the air. Nobody ever claims that increasing wind speed makes you feel warmer because the faster moving air doesn't have time to heat up as it blows past you.

It is true that, with a greater coolant velocity through the radiator each cubic inch of coolant going through the radiator loses less heat and thus has a lower temperature drop, but the greater velocity also moves more cubic inches through the radiator per unit of time, so there is a greater mass losing heat.

The increased heat transfer coefficient between the fluid and the radiator tube wall actually results in a slight increase in heat loss through the radiator with increasing fluid velocity

Trevor never got this, and was adamant and even abusive in his defense of his own ignorance. This is basic fluid mechanics. It is not a theory.

I believe that very likely cause of the high rpm overheating problem has to do with local boiling. In some cases it is caused by cavitation at the pump inlet, intermittent disruption of the water pump flow because it is momentarily vapor locked, then local boiling. It also might be due to unbalanced fluid flow across the two sides of the engine. I just know that between the improved cross-over tube, and moving the thermostat out of the water pump inlet, my problem was solved.

[SVXRide]

Originally Posted by Boxersix

I have a 170F thermo in it. Normal temp while driving fully warmed is 168-175 pending vehicles speed. On the dyno it creeped to 186F after a minute of constant running, then held steady until I took my foot off the throttle some odd 60-80 seconds later

If people want I can fab a few of these 50mm pump inlets for those looking to do this. Will be a straight lip, you'll just have to modify your radiator to suit and use an appropriate 2" ID hose.

Adam,
Put me down for one.
-Bill

[svxfiles]

Originally Posted by SVXRide

Adam,
Put me down.
-Bill

The raincoat picture was not enough for you, Wally?

[amber]

Originally Posted by shotgunslade

The notion that a greater flow rate through the radiator reduces cooling because the "coolant" doesn't have time to cool is totally wrong.

The radiator can be considered a cross flow heat exchanger. Heat transfer between the water and the air is a function of time, the fixed heat transfer area of the radiator and the logarithmic mean temperature difference between the air and the water. For the sake of simplification, we can consider the temperature of the air fixed, because we aren't worried for the moment about varying air flow, although the same arguments will hold for varying air flow that hold for varying water flow.

The greater the velocity of water through the radiator, the lower the temperature drop of the water. However, if the change in the heat transfer coefficient between the water and the radiator tube walls is ignored, the heat transferred from the water out the radiator is the same, despite the increased velocity because the greater velocity results in a greater mass flow. The two offset one another.

Q = M * U *p * deltaT

where:
Q = heat flux
M = mass flow rate
U = heat transfer coefficient
p = specifc heat
deltaT = logarithmic mean temperature difference.

Greater fluid velocity through the radiator, however, increases the heat transfer coefficient between fluid and radiator tube wall because the greater velocity erodes the static boundary layer between tube wall and flowing fluid. It is exactly the same phenomenon as wind chill factor. Increased air velocity (wind) erodes the boundary layer around your body, increasing the heat transfer coefficient, thus increasing heat transfer between your body and the air. Nobody ever claims that increasing wind speed makes you feel warmer because the faster moving air doesn't have time to heat up as it blows past you.

It is true that, with a greater coolant velocity through the radiator each cubic inch of coolant going through the radiator loses less heat and thus has a lower temperature drop, but the greater velocity also moves more cubic inches through the radiator per unit of time, so there is a greater mass losing heat.

The increased heat transfer coefficient between the fluid and the radiator tube wall actually results in a slight increase in heat loss through the radiator with increasing fluid velocity

Trevor never got this, and was adamant and even abusive in his defense of his own ignorance. This is basic fluid mechanics. It is not a theory.

I believe that very likely cause of the high rpm overheating problem has to do with local boiling. In some cases it is caused by cavitation at the pump inlet, intermittent disruption of the water pump flow because it is momentarily vapor locked, then local boiling. It also might be due to unbalanced fluid flow across the two sides of the engine. I just know that between the improved cross-over tube, and moving the thermostat out of the water pump inlet, my problem was solved.

I have have been sent two private messages regarding technical posts:-

1. “Trevor has been banned permanently from this forum. Please refrain from posting his comments for him. If you continue to do so you will be in violation of the rules for assisting in the circumvention of his banishment. In return, you too, shall be banned. Permanently. This subject is not up for debate, please comply.”

2. Post technical comments of your own to your heart's content. What we ask is that you not post comments in Trevor's stead. Perhaps you will get along better here by not prefacing every comment you post with, "I have just been on the phone with Trevor." In short: Your words = Allowed. Trevor's words = Not allowed.

Chris SVX World Network Administrator”

Therefore I now carefully comply absolutely with the above by replying personally in my own words to what has been in said by Shotgun when he was sure his statement could not be challenged. Yes I have talked to my friend Trevor, but this is my own personally instigated post and I have had the notion to put things right for some time.

I have been checking this cooling discussion for what seems like ages as I have often been asked by Trev to give an opinion on things and am therefore not new to the various arguments. Everyone siding with shotgun should examine all of what was said by Trevor rather than what shotgun claims was said.

Start with post number 1137 :-

“Kia ora Tony, Sadly we are at cross purposes here, but not to worry as the concept is very difficult to explain and comprehend. The surface temperature of a radiator or calculations for working out the temperature of the radiator is not really involved in what I have in mind.

The efficiency of the radiator and how well it actually works, will depend on the rate of air flow (how much air can get through it) and the conductive area presented to the air flow (the area/surface size of the core). This must be related to (considered together with) coolant flow capacity (how much coolant it can flow).

Each radiator will have optimum (correct as designed) air and coolant flow rates. If these are not complied with radiator will not work correctly.

The actual cooling rate (the amount that it cools the coolant passing through it) depends on the rate/speed of the coolant flow. (If the coolant passes through too quickly, or too slowly, the coolant will not be cooled as much.)

Fill a radiator with boiling water, wait one minute, tip out some water and measure the temperature. Repeat but wait five minutes and measure the temperature. Surely it is obvious that time and speed of coolant flow, i.e. flow rate, is a deciding factor, regardless of and quite independent from air flow.

How much heat is transferred within the engine to the coolant (How hot the coolant will get) also depends on the amount of time the coolant remains within the engine. (If the coolant passes through more quickly, the coolant will not be heated as much.)

Much earlier in this thread, in spite of nastily expressed opposition typical of the member involved, I have referred to a ratio of heat transfer between the radiator and engine which makes up the deciding equation.

If the coolant is flowing too fast. ----

a. Radiator. An increased flow/volume of coolant will pass through, but overall the radiator will become less effective (will not cool the increased amount coolant as well as the previous smaller amount was cooled). The temperature of the coolant exiting (coming out of the radiator), will be increased. (It will be hotter as it has not been cooled as well.)

a. Therefore records a definite negative factor, in respect of the cooling achieved as direct result of a flow increased beyond the designed optimum.

b. With an increased flow, there will be less transfer of heat within the engine. (The coolant will not heat up as much.)

b. Therefore records a marginal positive factor, in respect of the amount of heat to be later dissipated. (cooling required).

(*N.B. There is an associated important consideration, in that the engine temperature will rise. Hot spots and boiling pockets are also likely to occur due to any increase in pressure beyond the designed optimum, thus increasing temperature even further.)

Conclusion --- The conductive area within the radiator far exceeds that within the engine. Therefore if flow is excessive (there is too much flow), there may be slightly less heating of the coolant within the engine, but at the same time cooling via the radiator will be reduced very considerably. Result, an overheating system if the pump speed exceeds the optimum due to above normal engine RPM.

Expressed as factor, a. will be greater than b. and therefore there will be an increase in coolant temperature during the cooling process, when optimum flow is exceeded.

*N.B. At the same time engine heat will increase, thus accelerating the problem. The mugwump bird is in free flight.

It may seem strange that increased pressure and therefore flow, does not improve cooling, but when the pressure and flow exceeds the designed limit(optimum), the above scenario applies. The key is to prevent the optimum level being exceeded, e.g. by reducing the efficiency of the existing pump, a method proven in respect of other engines. Granted, cooling at lower RPM could be effected, but for others this has not created a problem. In any event, we are talking about a special application here and the fans should prove adequate to take care of the situation.

The above scenario may or may not represent the problem wrangled about here for so long, but should definitely receive full consideration and testing, especially as all else has failed.”



Also post number 1140 by Jersey Girl :-

“Don't want to muddy the waters or the coolant but the points Trevor made in his lengthy post are correct imo.

A free-er flowing and highly efficient radiator will only be able to dump extra engine generated heat if the coolant is being forced through it at the optimum rate for the whole system.

Too slow and the excess heat from the engine will not be pumped [transferred if you will] fast enough to the highly efficient rad.

Too fast, and the rate of heat transfer in BTUs as Tony notes will not be optimised.

What seems to be happening in our [generalised] case is that high pump speeds are causing higher than acceptable pressures in the system. These high pressures are a direct result of flow restrictions that are more likely to be in the engine block than in the radiator complex, though I have run no tests to prove that. It is just my opinion based on current reports.

Trevor I think is advocating reducing the coolant flow to match what the engine normally runs at, rather than the very high speeds of coolant flow that consistent speeds over 4500 rpm might generate. I see great merit in this approach.

However I will admit I would be happier to see tests identify where the restrictions are in the block, and if possible relieve them to allow a faster flow. Building up pressures so that the rad cap loses coolant is bad news.

I'm not offering answers here, just saying I think Trevor's thinking on the problem is correct as I see it. Joe.”

Also refer Harvey’s post page 77 no. 1145 and reply 1148.

Below is what shotgun in a very confrontational manner, incorrectly said in his thread quoted above. (His first effort was actually altered, edited with no reason given. I have the earlier unabridged version recorded.)

Shotgun:- “The notion that a greater flow rate through the radiator reduces cooling because the "coolant" doesn't have time to cool is totally wrong.

Trevor never got this, and was adamant and even abusive in his defence of his own ignorance. This is basic fluid mechanics. It is not a theory.”

In my opinion Trevor has never shown ignorance, or has in any way been abusive within this discussion. Perhaps some one can post the evidence of abuse for me.

I personally agree with all of what Trevor has stated. Actually shotgun shoots himself in the foot with his words; “The greater the velocity of water through the radiator, the lower the temperature drop of the water. It is agreed that as it passes through the radiator the coolant takes tim e to cool."

Shotgun then claims that as a result of mass flow, a term he obviously researched between his first and second posting efforts; “The two offset one another.” He conveniently ignores the fact that fluid simultaneously flowing at greater velocity within the engine is heated in the same way as it is cooled within the radiator. Therefore there is an increase in the ratio of heat transfer from the engine, and this offsets the effect related to mass flow. (Meaning the way the heat is transported rather than the rate of flow.)

Not something which can be shown by means of a pseudo equation included in place of plain language for dramatic effect. I see that one reader was taken in. Yes this is basic fluid mechanics and not theory as a Google will probably explain; try mass flow.

(Q * M * E) - (Q * M * R) = p LOL

On top of this we have a situation where a near logarithmic increase in pressure differential at many specific points of flow resistances will occur causing turbulence and local boiling. As has been clearly pointed out by more than one person in the posts already detailed. Readers should also note where Trevor has several times used the word "Optimum."

p = P * A

Where P = Pressure, A = area of passage openings. LOL

Seriously the point is that those looking for answers should not ignore a valid proposal to experiment with reduced flow at high RPM.

I have said my piece and done my bit take it or leave it. I am gone.

Joe Foy.

[oab_au]

Originally Posted by amber

I have have been sent two private messages regarding technical posts:-

1. “Trevor has been banned permanently from this forum. Please refrain from posting his comments for him. If you continue to do so you will be in violation of the rules for assisting in the circumvention of his banishment. In return, you too, shall be banned. Permanently. This subject is not up for debate, please comply.”

2. Post technical comments of your own to your heart's content. What we ask is that you not post comments in Trevor's stead. Perhaps you will get along better here by not prefacing every comment you post with, "I have just been on the phone with Trevor." In short: Your words = Allowed. Trevor's words = Not allowed.

Chris SVX World Network Administrator”

I have said my piece and done my bit take it or leave it. I am gone.

Joe Foy.

You have been told.

[Johnybeas]

ok so back on topic, my question is: With the modified exit to the radiator better aluminum radiator moved thermostat and enlarged pump inlet, would the modified y pipe on the engine be over kill or would it still be a good idea in light of future power increases and potential increased torque/power output later on?