Re: Science behind Mopar cooling??
[Re: Sniper]
#2902679
03/25/21 01:08 PM
03/25/21 01:08 PM
|
Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
If you can't dazzle em with diamonds..
|
If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
|
Can't give you a reason why the facotory did what they did, but the more/faster the water moves through the system the more heat transfer/cooling you get. The old wives tale of water going too fast is just that, a tale.
Of course, the University of Minnesota heat transfer lab could be wrong too, but since they have been at it since 1880, probably not. Doing some welding the other day and dunked the piece in the water tank, got me thinking of what you said. So used the torch to get a piece red hot, dipped it real fast and out, didn’t cool it much, got it red hot again dipped it for 15 seconds and it cooled down to touch. My thoughts are if the water is slow enough it’ll transfer the heat better, it needs time. After heating and dipping a few times that water got hot and it took much longer to cool to touch. Some welder in his garage has just proven the world's thermodynamic experts across all areas and centuries wrong. What's next? Gonna prove the theory of relativity is false? Maybe you ought to go read up on how it works and then you'll understand the reason high flow is the key, here's a hint it has little to do with time. In all fairness, that "time" consideration has been common misunderstanding on this site since day one. However, I have not seen and maybe missed the part mentioned here ( maybe earlier in the thread?) where rate does become a concern, when cavitation enters the picture, which is exacerbated by higher temps especially over boiling, but that is also mitigated by higher static operating pressures. All meaning, there are high flow rates where the coolant will absorb less heat intake as air bubbles form on the heated surfaces, and the coolant temp might actually start to show lower temps, as it loses liquid contact with the hot surfaces, and the surfaces create super hot spots of random boiling coolant. If I am just restating a topic already covered, sorry. "Cavitation is a phenomenon in which the static pressure of the liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, called "bubbles" or "voids", collapse and can generate shock waves that may damage machinery" Wiki
Last edited by jcc; 03/25/21 01:10 PM.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
|
|
|
Re: Science behind Mopar cooling??
[Re: Sniper]
#2902773
03/25/21 06:07 PM
03/25/21 06:07 PM
|
Joined: Jan 2004
Posts: 8,257 fredericksburg,va
cudaman1969
master
|
master
Joined: Jan 2004
Posts: 8,257
fredericksburg,va
|
Can't give you a reason why the facotory did what they did, but the more/faster the water moves through the system the more heat transfer/cooling you get. The old wives tale of water going too fast is just that, a tale.
Of course, the University of Minnesota heat transfer lab could be wrong too, but since they have been at it since 1880, probably not. Doing some welding the other day and dunked the piece in the water tank, got me thinking of what you said. So used the torch to get a piece red hot, dipped it real fast and out, didn’t cool it much, got it red hot again dipped it for 15 seconds and it cooled down to touch. My thoughts are if the water is slow enough it’ll transfer the heat better, it needs time. After heating and dipping a few times that water got hot and it took much longer to cool to touch. Some welder in his garage has just proven the world's thermodynamic experts across all areas and centuries wrong. What's next? Gonna prove the theory of relativity is false? Maybe you ought to go read up on how it works and then you'll understand the reason high flow is the key, here's a hint it has little to do with time. Exactly what I said dip sh!t TIME
|
|
|
Re: Science behind Mopar cooling??
[Re: cudaman1969]
#2902777
03/25/21 06:41 PM
03/25/21 06:41 PM
|
Joined: May 2019
Posts: 6,246 nowhere
Sniper
master
|
master
Joined: May 2019
Posts: 6,246
nowhere
|
Can't give you a reason why the facotory did what they did, but the more/faster the water moves through the system the more heat transfer/cooling you get. The old wives tale of water going too fast is just that, a tale.
Of course, the University of Minnesota heat transfer lab could be wrong too, but since they have been at it since 1880, probably not. Doing some welding the other day and dunked the piece in the water tank, got me thinking of what you said. So used the torch to get a piece red hot, dipped it real fast and out, didn’t cool it much, got it red hot again dipped it for 15 seconds and it cooled down to touch. My thoughts are if the water is slow enough it’ll transfer the heat better, it needs time. After heating and dipping a few times that water got hot and it took much longer to cool to touch. Some welder in his garage has just proven the world's thermodynamic experts across all areas and centuries wrong. What's next? Gonna prove the theory of relativity is false? Maybe you ought to go read up on how it works and then you'll understand the reason high flow is the key, here's a hint it has little to do with time. Exactly what I said dip sh!t TIME Reading comprehension isn't your forte.
|
|
|
Re: Science behind Mopar cooling??
[Re: 83hurstguy]
#2902897
03/26/21 08:51 AM
03/26/21 08:51 AM
|
Joined: Jun 2014
Posts: 1,323 VA
dragon slayer
pro stock
|
pro stock
Joined: Jun 2014
Posts: 1,323
VA
|
Can't give you a reason why the facotory did what they did, but the more/faster the water moves through the system the more heat transfer/cooling you get. The old wives tale of water going too fast is just that, a tale.
Of course, the University of Minnesota heat transfer lab could be wrong too, but since they have been at it since 1880, probably not. Doing some welding the other day and dunked the piece in the water tank, got me thinking of what you said. So used the torch to get a piece red hot, dipped it real fast and out, didn’t cool it much, got it red hot again dipped it for 15 seconds and it cooled down to touch. My thoughts are if the water is slow enough it’ll transfer the heat better, it needs time. After heating and dipping a few times that water got hot and it took much longer to cool to touch. I have done several projects with industrial air to water heat exchangers that are copper/nickel material with a fan (e.g. a giant radiator), and the heat transfer continues to increase with water velocity up to the point the tubes actually start to erode from the turbulence. Turbulent water flow causes mixing and is good for heat transfer. There was a statement on a previous page that each system has an optimum flow point for heat transfer. That's incorrect - you can always increase cooling by increasing flow up to the point of material limitations, pumping cost (friction loss), or other physical limitations. There's no heat transfer coefficient that reverses at some flow condition and causes the heat transfer of the system to decrease. In the bucket analogy, the heat transfer RATE between the hot part and the water is actually greater when you first immersed it, and that heat transfer RATE between the part and the water decreases as the difference in temperature between them decreases. If you wanted to cool the part even faster, you would have turbulent mixing in the bucket or the water exchanging itself out so there was no temperature rise of the cooling fluid. It's not a comparable analogy to an automotive cooling system, because the hot part isn't continuously generating its own heat either. Was this a small closed loop system, or a large industrial set up with huge cooling tank? The turbulent flow that is generated will also result in turbulent flow at the pump which is part of the system on a car, followed by cavitation, air pockets, nucleate boiling, then reduced flow and steam pockets. The car system is different. Air flow is an open system and you have a constant temp cooling air. Increase air flow, increase cooling effect in the radiator. Increase area of water and air contact increase cooling effect. Increase water flow through heat source and cooling source with internal pump part of small closed water system and effect can vary. There is a point when the coefficient of heat transfer can change an reduce effective heat transfer. Heat transfer is different for straight plate and a curved plate of same material.
|
|
|
Re: Science behind Mopar cooling??
[Re: Sniper]
#2902903
03/26/21 09:15 AM
03/26/21 09:15 AM
|
Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
If you can't dazzle em with diamonds..
|
If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
|
High flow rates tend to "wash away" any bubble formations which might insulate the part needing cooling. there are lots of papers out there on the issue.
One analogy to make the point was using a garden hose to cool then using a fire hose to cool. Which do you think did a better job?
A simplistic but still slightly flawed analogy/example. In your "wash away" comment above, that is true, and its likely equally true in that higher flow rate causes the bubbles/voids in the first place. I hope we both understand coolant flow in our context is not thru a straight uniform pipe, but thru a likely very coarse multiple direction changing path with many abrupt changes in coolant flow path in the engine block, heads, all precipitating cavitation concerns as flow rate increases.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
|
|
|
Re: Science behind Mopar cooling??
[Re: dragon slayer]
#2902909
03/26/21 09:26 AM
03/26/21 09:26 AM
|
Joined: Jan 2003
Posts: 21,507 N.E. OHIO, USA
A12
Too Many Posts
|
Too Many Posts
Joined: Jan 2003
Posts: 21,507
N.E. OHIO, USA
|
I know little or nothing about cooling systems, flow speeds, etc., the only thing I ever learned about liquid cooled internal combustion engines was "the engine is not cooled by liquid, the liquid is only the medium for moving the heat to a point where it can be dissipated by air. If the radiator was not in the system the engine would never be cooled by the liquid. Okay I hope that doesn't more than what is being discussed.....................sure is a very interesting thread .........I guess I'm learning more and more with each post "Liquid assisted, air cooled" Oh I did learn something about cooling systems.....the best way to handle the cavitation, flow speed (at all engine RPMs) coolant contact time is to use an electric water pump and electric radiator fan(s)....solves a lot of issues.
|
|
|
Re: Science behind Mopar cooling??
[Re: dragon slayer]
#2902952
03/26/21 10:50 AM
03/26/21 10:50 AM
|
Joined: Dec 2018
Posts: 88 IL
83hurstguy
member
|
member
Joined: Dec 2018
Posts: 88
IL
|
I have done several projects with industrial air to water heat exchangers that are copper/nickel material with a fan (e.g. a giant radiator), and the heat transfer continues to increase with water velocity up to the point the tubes actually start to erode from the turbulence. Turbulent water flow causes mixing and is good for heat transfer. There was a statement on a previous page that each system has an optimum flow point for heat transfer. That's incorrect - you can always increase cooling by increasing flow up to the point of material limitations, pumping cost (friction loss), or other physical limitations. There's no heat transfer coefficient that reverses at some flow condition and causes the heat transfer of the system to decrease.
In the bucket analogy, the heat transfer RATE between the hot part and the water is actually greater when you first immersed it, and that heat transfer RATE between the part and the water decreases as the difference in temperature between them decreases. If you wanted to cool the part even faster, you would have turbulent mixing in the bucket or the water exchanging itself out so there was no temperature rise of the cooling fluid. It's not a comparable analogy to an automotive cooling system, because the hot part isn't continuously generating its own heat either. Was this a small closed loop system, or a large industrial set up with huge cooling tank? The turbulent flow that is generated will also result in turbulent flow at the pump which is part of the system on a car, followed by cavitation, air pockets, nucleate boiling, then reduced flow and steam pockets. The car system is different. Air flow is an open system and you have a constant temp cooling air. Increase air flow, increase cooling effect in the radiator. Increase area of water and air contact increase cooling effect. Increase water flow through heat source and cooling source with internal pump part of small closed water system and effect can vary. There is a point when the coefficient of heat transfer can change an reduce effective heat transfer. Heat transfer is different for straight plate and a curved plate of same material. Turbulent flow in a localized area targeted for heat transfer doesn't necessarily equate to turbulent flow at the pump. You're going to need to explain your last two sentences, as they are far too general - What input(s) changes the coefficient of heat transfer to reduce the effective heat transfer and what drives that change? Also, using your postulated scenario, since air is assumed to be a constant temperature and unlimited heat sink, the faster you pump hot coolant to the radiator, the larger delta T you maintain between the radiator and atmospheric heat sink, therefore maximizing heat transfer rate between the two.
Last edited by 83hurstguy; 03/26/21 10:56 AM.
|
|
|
Re: Science behind Mopar cooling??
[Re: 83hurstguy]
#2902978
03/26/21 11:52 AM
03/26/21 11:52 AM
|
Joined: Jun 2014
Posts: 1,323 VA
dragon slayer
pro stock
|
pro stock
Joined: Jun 2014
Posts: 1,323
VA
|
It does cause cavitation at the pump for a car because the pump can generate extra heat, and pressure drop at the impeller. It is not an external pump with head tank to the pump input before flowing to the heat exchange such as in industrial set ups. That head prevents cavitation. The Pump is centered on the heat exchanger because the fan is connected to the pump. Heat exchanger outlet goes up to the pump, vice down like a head tank. Less input pressure, so as you increase water flow you increase risk for cavitation.
There are engineering studies that show how the heat transfer coefficient changes. It is not linear in all ranges with flow. Just like hp and torque curves fall off. It would be optimized in a system design. Heat transfer is a rate right? One molecule of water moving through the radiator at the speed of sound would cool less then one moving a 10mph. At higher speeds it is in the cool zone less. Of course the next molecule in would probably be hotter then the one in front because it is a closed loop. Obviously the goal is keeping the engine at the correct operating temp during various uncontrollable conditions like winter versus summer.
That 440 RV test had a lot of good info an unexpected results with many different impeller designs. Those that were larger did not always produce cooler engine temps. I think a lot of this is in the weeds if you get a good radiator and fan set up.
Last edited by dragon slayer; 03/26/21 11:53 AM.
|
|
|
Re: Science behind Mopar cooling??
[Re: dragon slayer]
#2903029
03/26/21 02:16 PM
03/26/21 02:16 PM
|
Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
If you can't dazzle em with diamonds..
|
If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
|
"One molecule of water moving through the radiator at the speed of sound would cool less then one moving a 10mph."
But we are not talking about one molecule, we are talking about is how many molecules over a period of time, ie rate, who cares what each molecule absorbs, its the overall result that is the issue I believe, and as noted, the more molecules the higher the T delta.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
|
|
|
Re: Science behind Mopar cooling??
[Re: dragon slayer]
#2903235
03/26/21 11:28 PM
03/26/21 11:28 PM
|
Joined: Dec 2018
Posts: 88 IL
83hurstguy
member
|
member
Joined: Dec 2018
Posts: 88
IL
|
There are engineering studies that show how the heat transfer coefficient changes. It is not linear in all ranges with flow. Just like hp and torque curves fall off. It would be optimized in a system design. Heat transfer is a rate right? One molecule of water moving through the radiator at the speed of sound would cool less then one moving a 10mph. At higher speeds it is in the cool zone less. Of course the next molecule in would probably be hotter then the one in front because it is a closed loop. Obviously the goal is keeping the engine at the correct operating temp during various uncontrollable conditions like winter versus summer. Just because something is non-linear, does not mean that it has an inflection point and decreases over a specific value. The rest of those analogies aren't even relevant. This is probably some of the best compiled cooling system information on the internet; Stewart did a ton of testing on stock car/NASCAR engines and posted some of their findings, unfortunately only the summaries are still available. https://www.stewartcomponents.com/index.php?route=information/information&information_id=14I never commented on the original post regarding why A/C cars are over-driven and non-A/C cars are under driven. It has everything to do with the fan speed. Due to the condenser being in front of the radiator (higher pressure drop through the stacked cores) and also the need to have airflow for the A/C to work at low car speeds (e.g., sitting in traffic), the water pump pulley was overdriven to spin the fan quicker. Now... for using a 22" radiator to cool the big block. Hopefully cleaning this one out works, but if not, find a radiator that has the widest tubes possible and most tube-to-fin contact area. Unfortunately, this is where expensive radiators earn their keep over the cheaper ones. The hotter you keep the radiator fins due to their contact with the coolant tubes, the more heat will get transferred to the air stream. Aluminum is stronger than copper, so the AL radiators can run larger tubes and get significantly more fin contact area. For example... three rows of 9/16" tubes = 1-11/16" of tube/fin contact length. A radiator with two rows of 1" aluminum tubes likely fits in the same core spot and gets 2" of tube/fin contact. Radiator core design can be a bit tricky, because if you just increase thickness, the pressure drop across the air side increases, which then decreases fan flow and is counter productive... most of the expensive units have figured this out.
|
|
|
Re: Science behind Mopar cooling??
[Re: PhillyRag]
#2903276
03/27/21 06:19 AM
03/27/21 06:19 AM
|
Joined: Dec 2014
Posts: 5,815 ohio
ruderunner
master
|
master
Joined: Dec 2014
Posts: 5,815
ohio
|
I don't get the constant claims of marginal cooling. Other than the wing cars, it's not like every Mopar was an unreliable overheating pile of junk. Most problems I've seen are leaks or clogs(usually from excessive stpp leak)
Make sure the system works correctly, clean and leak free. Correct fan and shroud.
Heck, I ran my roadrunner without a fan for one summer. I've seen Dodge trucks with no pump blades run without overheating.
Angry white pureblood male
|
|
|
Re: Science behind Mopar cooling??
[Re: SportF]
#2903292
03/27/21 08:01 AM
03/27/21 08:01 AM
|
Joined: Jan 2008
Posts: 1,212 Minn
SportF
pro stock
|
pro stock
Joined: Jan 2008
Posts: 1,212
Minn
|
Can't give you a reason why the facotory did what they did, but the more/faster the water moves through the system the more heat transfer/cooling you get. The old wives tale of water going too fast is just that, a tale.
Of course, the University of Minnesota heat transfer lab could be wrong too, but since they have been at it since 1880, probably not. It could be the physics in your radiator are different than the physics of other radiators in other parts of the universe. Not much chance, but if true, you should get a hold of the Mechanical lab at the U of M.
|
|
|
Re: Science behind Mopar cooling??
[Re: PhillyRag]
#2903301
03/27/21 08:56 AM
03/27/21 08:56 AM
|
Joined: Jun 2014
Posts: 1,323 VA
dragon slayer
pro stock
|
pro stock
Joined: Jun 2014
Posts: 1,323
VA
|
Who here believes Chrysler had a Thermodynamics Engineer/Scientist on staff during the late 60's, doing "Nucleate Boiling Analysis" before "finalizing" a coolant system. Or was it Trial&Error as with many of the racers of that era? They took it to an "acceptable" level & then rubber stamped it. After all it was Chrysler & not NASA. Guess that's why many of these cars are marginal at-best wrt cooling. Yes they did actually. Go read a few patent documents on any part of a car and come back and tell us that they were just trial and error like high school racers. There was engineering and science involved. They applied know thermodynamic principles/laws along with fluid mechanics taught at any mechanical engineering college. Go head take a closed car system with a 22 or 26" radiator and raise the water flow to the maximum you can and come back and tell us how much more it cooled the car. The water is either in the block and heads being heated or in the radiator being cooled. It comes to equilibrium based on the volume of the system, the heat source and the cooling source. Keep the open system airflow constant at let say 80degrees and constant flow. Just raise water flow rate
|
|
|
Re: Science behind Mopar cooling??
[Re: dragon slayer]
#2903311
03/27/21 09:20 AM
03/27/21 09:20 AM
|
Joined: Dec 2018
Posts: 88 IL
83hurstguy
member
|
member
Joined: Dec 2018
Posts: 88
IL
|
"Just because something is non-linear, does not mean that it has an inflection point and decreases over a specific value. The rest of those analogies aren't even relevant."
Of course not, but with nucleate boiling it does occur. Aaaaand nucleate boiling occurs at lower flow rates because of increased coolant temperature rise, which decreases heat transfer coefficient. From the EMP Stewart link: “Higher coolant flow will ALWAYS result in higher heat transfer. Coolant cannot absorb heat after it reaches it's pressure corrected vapor point. Furthermore, coolant absorbs heat at a progressively slower rate as it approaches this point.” Thanks for proving my point, my work here is done.
|
|
|
Re: Science behind Mopar cooling??
[Re: 83hurstguy]
#2903320
03/27/21 09:58 AM
03/27/21 09:58 AM
|
Joined: Sep 2014
Posts: 4,457 Washington
madscientist
master
|
master
Joined: Sep 2014
Posts: 4,457
Washington
|
There are engineering studies that show how the heat transfer coefficient changes. It is not linear in all ranges with flow. Just like hp and torque curves fall off. It would be optimized in a system design. Heat transfer is a rate right? One molecule of water moving through the radiator at the speed of sound would cool less then one moving a 10mph. At higher speeds it is in the cool zone less. Of course the next molecule in would probably be hotter then the one in front because it is a closed loop. Obviously the goal is keeping the engine at the correct operating temp during various uncontrollable conditions like winter versus summer. Just because something is non-linear, does not mean that it has an inflection point and decreases over a specific value. The rest of those analogies aren't even relevant. This is probably some of the best compiled cooling system information on the internet; Stewart did a ton of testing on stock car/NASCAR engines and posted some of their findings, unfortunately only the summaries are still available. https://www.stewartcomponents.com/index.php?route=information/information&information_id=14I never commented on the original post regarding why A/C cars are over-driven and non-A/C cars are under driven. It has everything to do with the fan speed. Due to the condenser being in front of the radiator (higher pressure drop through the stacked cores) and also the need to have airflow for the A/C to work at low car speeds (e.g., sitting in traffic), the water pump pulley was overdriven to spin the fan quicker. Now... for using a 22" radiator to cool the big block. Hopefully cleaning this one out works, but if not, find a radiator that has the widest tubes possible and most tube-to-fin contact area. Unfortunately, this is where expensive radiators earn their keep over the cheaper ones. The hotter you keep the radiator fins due to their contact with the coolant tubes, the more heat will get transferred to the air stream. Aluminum is stronger than copper, so the AL radiators can run larger tubes and get significantly more fin contact area. For example... three rows of 9/16" tubes = 1-11/16" of tube/fin contact length. A radiator with two rows of 1" aluminum tubes likely fits in the same core spot and gets 2" of tube/fin contact. Radiator core design can be a bit tricky, because if you just increase thickness, the pressure drop across the air side increases, which then decreases fan flow and is counter productive... most of the expensive units have figured this out. Thanks for the link. That was great to read.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
|
|
|
Re: Science behind Mopar cooling??
[Re: madscientist]
#2903381
03/27/21 02:16 PM
03/27/21 02:16 PM
|
Joined: Sep 2003
Posts: 19,402 north of coder
moparx
"Butt Crack Bob"
|
"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,402
north of coder
|
an informative link, and i thank you for the posting ! and now the everlasting debate, what exactly is "hot" ? many moons ago, i was of the opinion that 180 degrees was getting "too hot". now, i like to see running temperatures of 195-205, and somewhat get concerned when seeing 220-230 in stop and go traffic on a 100 degree day. am i way off base crazy ? [i have been told i am more than "nutz" quite a few times. ]
|
|
|
|
|