SVX Engine cooling "Again & Again"

[McTaff]

My aplogies. While editing my post for formatting, I did indeed leave out a paragraph that was rather important. It directly addressed Tony's point of the fluid in the radiator having to "go the long way", and referenced the "average speed" issue. I haven't got the time to re-write it all out, suffice to say that my 'word-picture' was getting towards explaining that part (but I'm just going to drop it as I'm late for work!)

[Trevor]

Originally Posted by svxistentialist

It is interesting all right Tony.

I think the point to keep in mind is that the radiators are designed primarily as heat exchangers, and the rate of flow through the galleries is governed [by the cross-sectional area mostly] to flow through at a speed that will lose the most heat.

The 7500 rpm you mention is outside the design range of the SVX as delivered OEM. Because they were all auto the maximum rev limit is restricted by the gearbox computer to the upper shift limit, which I think is maybe 6800, but don't quote me on that.

Agreed.

You are correct in your assumption that the resistance to flow could make the standard radiator a restriction in the circuit for high revs cars. What will happen in practice is the higher speed pumping will exert a higher pressure on the top tank than the radiator cap can withstand and extra fluid will be pumped to the expansion bottle.

If this was happening a lot it would indicate that a larger radiator was called for, one with more passages to let the extra fluid through [and cool it better, hopefully ]. But the coolant will still be traveling through the passages at the same speed because it must do to effectively cool the liquid. It will just be traveling through more of them to keep the pressure down below the limit where the cap releases fluid to the expansion bottle. Joe

These various assumptions do not apply and are not correct or applicable.

Heat alone causes the overall standing gauge pressure (i.e. that above atmospheric) within a closed circuit cooling system. The pump with the assistance of a natural thermosyphon effect, does no more than circulate the coolant, against whatever internal restriction exists within the circuit.

Pressure differences exist within the cooling circuit due to restrictions. Only the differences between pressure points have significance and these must be considered one against the other, rather than directly compared with atmospheric pressure. The pump inlet and outlet is not in contact with the atmosphere, and the pump can only effect pressure differences, not the overall gauge pressure.

Pump speed directly governs the rate and speed of flow within the system, dependent on the overall degree of restriction/resistance which remains static once the thermostat is fully open. Pump speed is therefore a deciding factor.

The size of the radiator will affect the area of coolant presented to the air via the element, rather than the rate of through flow. This is dependent on the efficiency and speed of the pump, working against the normally fixed total restriction within the system.

The higher the rate of flow, the less time a given amount of coolant remains within the radiator to become cooled. However simultaneously, an increase in the rate of flow will reduce the time the similar amount of coolant is in contact with the engine surfaces requiring cooling, meaning that there will be less transfer of heat to the coolant. Importantly the heating area involved is considerably less than the cooling area presented by the radiator. As a result of this included ratio, the final outcome is a loss of cooling efficiency in the event that the flow rate is increased above the original as designed optimum.

Abnormal constant engine speed, high pump speed and an excessive rate of flow, has a negative effect on the efficiency of the cooling system. This is the exact essence ot the problem covered by this now ridiculously convoluted thread. QED.

[Dessertrunner]

This is the exact essence ot the problem covered by this now ridiculously convoluted thread. QED

Trevor debate is good, insults are bad. Before you throw rocks you need to remember what we have acheived. Just because every one doesn't agree with you doesn't mean you should mock us or the work.
You have an opinion and we lisen to it you need to do the same.

As the joke goes
"The only perfect person in the world was Jesus Christ and look what they did to him, so what hope have the rest of us got"

Tony

[Trevor]

Originally Posted by Dessertrunner

Trevor debate is good, insults are bad. Before you throw rocks you need to remember what we have acheived. Just because every one doesn't agree with you doesn't mean you should mock us or the work.
You have an opinion and we lisen to it you need to do the same.

As the joke goes
"The only perfect person in the world was Jesus Christ and look what they did to him, so what hope have the rest of us got"

Tony

Tony,

Please do not read that which is not written.

My words, "This is the exact essence ot the problem covered by this now ridiculously convoluted thread. QED" is in no way intended as personally derogatory and does not constitute an insult.

I have "listened" to opinion and have done no more than comment in an explicit manner. If my stated opinion, is taken as rock throwing, so be it.

It is an obvious fact, that this thread has become an absolutely stupid convoluted mess. In line with members suggestions within another current thread, it would be very helpful if at this point, you could summarise what is truly confirmed as having been an achievement.

[Dessertrunner]

Trevor.
When we run the last trial on the car hopefully today I will start a summary. have a great day in Kiwi land.
Tony

[oab_au]

Originally Posted by Trevor

, not the overall gauge pressure.

This is the exact essence ot the problem covered by this now ridiculously convoluted thread. QED.

This thread has 799 posts, Tony has 254, Trevor has 134, Bill 66, I have 47.as can be seen here,
http://www.subaru-svx.net/forum/misc...posted&t=51702
If you read Trevor's posts here,
http://www.subaru-svx.net/forum/sear...earchid=625923
you will not find a lot of constructive help on this thread. If the thread is to be made readable, these 134 posts could be removed, and the thread would not lose any content.

Harvey.

[shotgunslade]

The higher the rate of flow, the less time a given amount of coolant remains within the radiator to become cooled. However simultaneously, an increase in the rate of flow will reduce the time the similar amount of coolant is in contact with the engine surfaces requiring cooling, meaning that there will be less transfer of heat to the coolant. Importantly the heating area involved is considerably less than the cooling area presented by the radiator. As a result of this included ratio, the final outcome is a loss of cooling efficiency in the event that the flow rate is increased above the original as designed optimum.

Abnormal constant engine speed, high pump speed and an excessive rate of flow, has a negative effect on the efficiency of the cooling system. This is the exact essence ot the problem covered by this now ridiculously convoluted thread. QED.

This is a factual error in basic fluid heat transfer. Increasing water flow rate through a radiator almost never decreases the rate of heat loss from the water to the passing air. Although the temperature drop of the water will decrease because of decreased residence time, the total heat loss will increase because of the greater mass flow of water losing heat and because of the increased logratihmic mean temperature differential between the water and the air. DO THE MATH.

Also, Trevor is right that the pump has no impact on the average pressure differential between the coolant loop and the air. This average pressure differential is affected by fluid vapor pressure, total height of the loop, imposed pressurization from an initial charge, and other factors. But, the local pressure differntial at any point is a function of that average pressure differential and the pump discharge pressure less the pressure drop between the pump outlet and that local position. Local pressure differential between coolant and atmosphere will be much greater at the pump outlet than at the pump inlet, because all of the pump head has been attenuated by system pressure drop by the time the coolant gets to the pump inlet.

Having said that, I would guess that the pressure drop through the engine at any given flow is likely greater than that through the radiator, so the local pressure at the radiator may be equal or less than the average pressure differential between coolant loop and atmosphere. The system is probably designed to pump through the engine rather than through the radiator, so that the local pressure variation above atmospheric at the radiator cap caused by flow variation (a function of pump, and thus engine rpm) is minimized.

An event such as local boiling, anywhere in the system will increase the average coolant system to atmosphere pressure diferential. That is why the radiator cap will pop, even though boiling may be remote from that point.

[SVXRide]

Originally Posted by shotgunslade

This is a factual error in basic fluid heat transfer. Increasing water flow rate through a radiator almost never decreases the rate of heat loss from the water to the passing air. Although the temperature drop of the water will decrease because of decreased residence time, the total heat loss will increase because of the greater mass flow of water losing heat and because of the increased logratihmic mean temperature differential between the water and the air. DO THE MATH.

Also, Trevor is right that the pump has no impact on the average pressure differential between the coolant loop and the air. This average pressure differential is affected by fluid vapor pressure, total height of the loop, imposed pressurization from an initial charge, and other factors. But, the local pressure differntial at any point is a function of that average pressure differential and the pump discharge pressure less the pressure drop between the pump outlet and that local position. Local pressure differential between coolant and atmosphere will be much greater at the pump outlet than at the pump inlet, because all of the pump head has been attenuated by system pressure drop by the time the coolant gets to the pump inlet.

Having said that, I would guess that the pressure drop through the engine at any given flow is likely greater than that through the radiator, so the local pressure at the radiator may be equal or less than the average pressure differential between coolant loop and atmosphere. The system is probably designed to pump through the engine rather than through the radiator, so that the local pressure variation above atmospheric at the radiator cap caused by flow variation (a function of pump, and thus engine rpm) is minimized.

An event such as local boiling, anywhere in the system will increase the average coolant system to atmosphere pressure diferential. That is why the radiator cap will pop, even though boiling may be remote from that point.

Whoa, serious flashback to junior year heat transfer and thermodynamics classes
-Bill
p.s. serious in this case means 28 years' worth

[shotgunslade]

Bill:

I assume you did the math, otherwise you wouldn't be a rocket scientist.

Dan

Gotcha - 34 years

[SVXRide]

Originally Posted by shotgunslade

Bill:

I assume you did the math, otherwise you wouldn't be a rocket scientist.

Dan

Gotcha - 34 years

Dan,
which is why you are the Professor and I am but a humble student

I have a request of everyone who has been participating in this thread. After flipping through the multitude of posts, I only found one figure that tried to lay out the coolant flow in the EG33 (Harvey's from very early in the thread). I've taken that figure and tweaked it a little to represent what I believe YT has done on Dan's engine. I know I'm missing at least one of the stock flow paths (off of the cross over pipe), but I'm fighting a head/chest cold right now and I'm too wimpy to walk down to the garage and trace the lines on RacerX
So, for your viewing pleasure and comments....


-Bill

[Trevor]

Originally Posted by oab_au

This thread has 799 posts, Tony has 254, Trevor has 134, Bill 66, I have 47.as can be seen here,
http://www.subaru-svx.net/forum/misc...posted&t=51702
If you read Trevor's posts here,
http://www.subaru-svx.net/forum/sear...earchid=625923
you will not find a lot of constructive help on this thread. If the thread is to be made readable, these 134 posts could be removed, and the thread would not lose any content.

Harvey.

Harvey,

Your obnoxious comments confirm your worth. You confirm that you have been doing no more than sitting on the sideline loading your gun, in the patient but agitated anticipation, of firing a slanderous broadside. Better that you had loaded shot with powder.

Those with intellect will have observed that every post I have contributed, has constituted accurate constructive comment. Each sincerely thought through, with the sole object of preventing incorrect evidence from deflecting the thread from its true objective. Prove otherwise.

Trevor.

[oab_au]

Yes I think your reply would summarize your technical contribution to this thread.
Harvey.

[oab_au]

Originally Posted by SVXRide

Dan,
which is why you are the Professor and I am but a humble student

I have a request of everyone who has been participating in this thread. After flipping through the multitude of posts, I only found one figure that tried to lay out the coolant flow in the EG33 (Harvey's from very early in the thread). I've taken that figure and tweaked it a little to represent what I believe YT has done on Dan's engine. I know I'm missing at least one of the stock flow paths (off of the cross over pipe), but I'm fighting a head/chest cold right now and I'm too wimpy to walk down to the garage and trace the lines on RacerX
So, for your viewing pleasure and comments....


-Bill

Wow big pic Bill. The two pipes that you have added to the top, are normally bleed holes that are incorporated in the original crossover pipe, so Tom has added pipes to do that job.
I do think that the pipe that runs from the left hand side of the crossover pipe back to the pump, should still be left there, as it allows the temp sensor to warm up quickly. Without a thermostat it would take a much longer time to do it.
The heater circuit runs from the right hand side of the crossover pipe, back to the pump.
Harvey.

[Trevor]

Originally Posted by shotgunslade

This is a factual error in basic fluid heat transfer. Increasing water flow rate through a radiator almost never decreases the rate of heat loss from the water to the passing air. Although the temperature drop of the water will decrease because of decreased residence time, the total heat loss will increase because of the greater mass flow of water losing heat and because of the increased logratihmic mean temperature differential between the water and the air. DO THE MATH.

The same situation with regard to heat transfer applies in regard to the heating of the water within the engine galleries. My concluding and operative statement and overall point --- ”As a result of this included ratio, the final outcome is a loss of cooling efficiency in the event that the flow rate is increased above the original as designed optimum.”
I agree that mathematics are involved.

Also, Trevor is right that the pump has no impact on the average pressure differential between the coolant loop and the air. This average pressure differential is affected by fluid vapor pressure, total height of the loop, imposed pressurization from an initial charge, and other factors. But, the local pressure differntial at any point is a function of that average pressure differential and the pump discharge pressure less the pressure drop between the pump outlet and that local position. Local pressure differential between coolant and atmosphere will be much greater at the pump outlet than at the pump inlet, because all of the pump head has been attenuated by system pressure drop by the time the coolant gets to the pump inlet.

Having said that, I would guess that the pressure drop through the engine at any given flow is likely greater than that through the radiator, so the local pressure at the radiator may be equal or less than the average pressure differential between coolant loop and atmosphere. The system is probably designed to pump through the engine rather than through the radiator, so that the local pressure variation above atmospheric at the radiator cap caused by flow variation (a function of pump, and thus engine rpm) is minimized.

An event such as local boiling, anywhere in the system will increase the average coolant system to atmosphere pressure diferential. That is why the radiator cap will pop, even though boiling may be remote from that point.

Special thanks for adding confirmation and for your efforts towards retaining accuracy within this thread. Your intuitive post illustrates considerable concentrated effort, this in vast contrast to an adjacent destructive effort authored by Harvey. Readers must wish that all posts within this tedious thread were as well constructed and intended as yours.

[Trevor]

Originally Posted by oab_au

Wow big pic Bill. The two pipes that you have added to the top, are normally bleed holes that are incorporated in the original crossover pipe, so Tom has added pipes to do that job.
I do think that the pipe that runs from the left hand side of the crossover pipe back to the pump, should still be left there, as it allows the temp sensor to warm up quickly. Without a thermostat it would take a much longer time to do it.
The heater circuit runs from the right hand side of the crossover pipe, back to the pump.
Harvey.
Harvey.

Harvey,

The above text as no real value and a your self serving second publication of your image, does no more than clutter the thread.

Those dwelling in glass houses ----.