Technical New AC…and now SBC runs 30 degrees hotter

Thanks for the information, I've learned somethings I didn't know. Because of all this, I am reworking my '37 to gain air flow through the radiator instead of up over it !

 

I have a 1951 John Deere Model B that has a "thermosiphon" cooling system, (ie, no water pump) and I believe it works due to the fact that the system is designed with very large water jackets with low restriction to flow, the inlet and outlet to the radiator and the ***ociated plumbing is quite large, and the tubes in the radiator have significant internal capacity. So it's quite easy for the hot coolant to go up and the cool coolant to go down. And there is a lot of coolant in the system. 5 and a half gallons. So it takes a while to warm up the coolant in the engine, and it has plenty of time to move before it gets too hot. 27 Horsepower. 146 Cubic Inches. Pretty easy to cool using thermodynamics.

Oh, and it has no thermostat. The user is required to watch the temperature gauge, and once the system gets up to temp the user opens the shutters in front of the radiator via a lever mounted on the steering post.

In our internal combustion propelled toys there was a need to squeeze more power out of less iron, in a smaller space, and one of the areas that was targeted was those large water jackets and such. Since there was more restriction to flow through these smaller p***ages, a water pump is used to force the coolant to move.

 

Yes, we're extracting much more power from smaller engines, the demands placed on the cooling systems are far greater. It was an exaggerated example to point out the deficiency of his theory that changing the rate of coolant flow makes no difference in system efficiency.

 

Again, it's pretty simple stuff. A pump simply provides flow and guarantees movement.....but even with that there are places where air can become trapped in a system. A lot has to do with the placement of the components in relation to each other. Later model engines often have steam vents to allow air to purge at the top of a system. There are places where the water must rise up to flow as well as drop down.......it twists and turns its way thru your system. On my Cadillac build I have modified the block and the heads to provide better flow because of known problems with the flow at the rear of the motor. In my previous posts I have said that speed of flow does not matter as long as there is a reasonable amount of flow. You talk about "vintage equipment" where the water flows under its own accord......but you didn't say automobile.
An automobile is subjected to lots of other forces outside the coolant system that can affect flow. Things like acceleration and centrifugal forces on curves as well as gravity when going up and down hills....even mountains. All things that would not affect stationary or possibly slow moving equipment. Additionally the engine will have turns and corners and crevices and insuring the movement provides less chance for stagnant hot spots.
Your example above has nothing at all to do with changing a flow rate as apparently the equipment operated at a reasonably steady rate for long hours. Maybe the flow rate varied a little but basically you had a steady rate of work generating a constant level of heat........and a "radiator" in the form of a tank or whatever that had sufficient capacity to dispel that heat. Nothing about an increased flow rate that I can see.
Anyone who has ever done much welding knows that something hot will not transfer as much heat if you let go of it quickly!

Blues 4U said: "It was an exaggerated example to point out the deficiency of his theory that changing the rate of coolant flow makes no difference in efficiency".

Actually, your vintage example provides proof that heat can be cooled sufficiently without needing a high speed flow..............no pump needed. Its all about components being correctly sized for the job at hand..........and ratio of contact time between the heat source and the cooling air. Reread what Ebbspeed said in his post. Its not about speed, but properly sized components, and you can't do that in an automobile because of the size that would be needed as well as the other forces outside of the engine.

 

No matter what, all the rhetoric usually provides some help if you sift it enuff
Honest differences of opinion are a good thing because it produces information. Agreement seldom does.

 

A contributor here gives the impression the there is no circulation for in the cooling system when the thermostat is closed. That is not the case as engine cooling systems have a byp*** to keep the coolant moving in the engine block and head (s) by the water pump until the thermostat begins to open allowing the radiator to become part of the system.

A statement above saying they did not know anyone had “a cooling problem” today until reading about here on the HAMB was my feeling also until one became apparent in my mid 50’s car and engine. When previously owned new in the family by my parents and then by me one never occurred even living in warmed climates. The only major thing difference is the formulation of the fuel we use today.

 

You are absolutely correct. What I should have said is that the water in the engine circulates within the engine during warmup..........but does not circulate thru the radiator until the engine reaches the correct temperature. Circulation, but not thru the entire system. Good catch Jimmy. Here is a video. Notice the notation on the lower left of the video about the engine temp.

 

Smart people

 

I've given you multiple opportunities to back off your claims but you hang on to them like a bulldog with a bone. Do you have anything to back up your ***ertion that rate of coolant flow has no affect on heat transfer efficiency? Got any links, any engineering or thermodynamics to back it up?

You might want to google Q = M x C x Delta T an engineering equation for heat transfer efficiency that says that Q (heat transfer efficiency) equals M (m*** flow rate) x C (specific heat of coolant) x Delta T (temperature difference). With that equation, if you increase M, C or Delta T you will also increase Q. It's basic thermodynamics. If all else remains constant, than increasing the flow rate will increase heat transfer efficiency.

"In other words, the rate of heat transfer is directly proportional to m*** flow rate. If you increase the flow rate, you will then increase the rate of heat transfer. Since you cannot mess with mother nature, it is very naive to think it works any other way."

That is science. Whatcha got?

 

If you increase the flow rate, I would ***ume you reduce delta T. With the coolant moving slow you may have it just about boiling when it leaves the engine, say 200 degrees for a nice even number, but after spending a long time in the radiator it's quite cool, say 100 degrees. Bump up the flow and the temperatures even out throughout the system, with perhaps 155 coming out of the engine and 145 degrees returning. The average would be 150 in both examples.
All numbers fictional as I'm not gonna bother figuring out what's sensible in farenheit just for an example.

I'm just thinking that you don't just change one thing when you alter the flow. With little flow the coolant will spend a lot of time both in the engine and radiator, and the temperature of the coolant will change a lot during that time. Too many details for getting any sense out of the formula without actual measured data to put into the equation.

 

If you increase M you also increase Q, which will result in a greater Delta T, not less.

But, you are correct in that it is impractical to change just one parameter, often in the process of changing one thing you end up changing something else, so everything does not remain constant. But the point I was addressing is that @ekimneirbo has repeatedly ***erted that changing the rate of flow does not affect heat transfer efficiency, which it should be clear now that it does. And this would affect both the rate at which the engine transfers heat to the coolant, and the rate at which the coolant transfers heat to the radiator.

 

To me ( uneducated in this field of study ) flow rate only changes the difference of out going and incoming coolant temperature of the engine. Just as our Sweden buddy pointed out, faster water has less time to heat up, but also less time to cool off. Coolant speed can not compensate for poor air flow, poor choice of radiator, or dirty or constricted coolant p***ages. The efficiency of the radiator or the engine does not change with flow rate, they can only absorb or disperse heat at set rate, and that rate can not change with out changing the size, shape, or materials used in constructing them.

 

And you base that on???? I gave you the information above, this is a basic law of thermodynamics, and you discount it based on what exactly?

 

It might seem counterintuitive to you, but this is how it works. Here's something that might help explain it. https://lambdageeks.com/m***-flow-rate-and-heat-transfer/

"The heat transfer rate ΔQ is proportional to the m*** flow rate m° in direct relation. It means heat transfer increases with an raising the m*** flow rate

The m*** flow rate m° or volume flow rate V° is the actual m*** (m) or volume (v) circulating through the system per unit of time. It is given in Kg/s or LPM (liter per min).

The equation of heat transfer in relationship with m*** flow rate is,

ΔQ = m° Cp ΔT

where,

• ΔQ = Rate of heat transfer (kW)
• m° = M*** flow rate (kg/s or LPM)
• ΔT = Temperature difference in Kelvin
• Cp = Specific heat at constant pressure (kJ/kg K)

This equation is elementary in thermodynamics to calculate heat transfer.

The heat transfer can be enhanced by increasing the m*** flow rate of the system."

 

So, if the rate of heat transfer is directly proportional to m*** flow rate, pumping water thru a radiator faster would make it cool better ? How does flowing faster thru the radiator cause more heat to dissipate? Coolant has m***.....doesn't it?

Now on the other hand, I can see how moving more air thru the radiator will cause more heat to dissipate........if the coolant is in there long enough.

The thing you are overlooking is the constraints imposed by the design of an automotive system do not allow for unlimited variation that other situations might have. How much can you actually increase water speed in a cars engine. I don't think its going to be very much....before all the limiting factors like turns and corners and crevices and changes of direction create problems?

You have to realize that while theories and formulas are great, engineers always have to test those things in real life situations to find out what things are causing their theories not to function as designed. Current practice is that coolant goes thru larger radiators, radiators with more cores, and even multi-p*** radiators. Add to that the technological advances in radiator fin designs and crossflow vs vertical flow along with clutch operated fans and electric fans............
Not a whole lot of research on water speeds though.

Maybe they are on to something..........

Now other than criticize what I have posted and try to dismiss it with a bunch of misapplied theory, I don't see where you have posted any real solutions. Why not start a new thread and explain to everyone how they can increase their coolant speeds and and solve all their overheating issues.

 

This is a basic issue that you have to get correct first. We've already slayed this dragon before. I hate that it keeps rearing it's ugly head and we have to slay it all over again. You are the one who just wants to keep posting the same ****, refuting known science with nothing to back it up. If we can just all accept that slowing the coolant down to give it more time in the radiator is not the right approach to addressing a coolant problem, than we never have to address this **** again. Stop being an impediment to that.

 

These kinds of questions are always head scratchers for someone even like myself who has an engineering degree and spent a good chuck of my career in HVAC and participated in a military vehicle engine cooling tests and design. In this type of situation, you are dealing with a “closed” system. You cannot look at it from a simple heat transfer equation, because the “system” has several variables, and changing the value of one, often influences the value(s), of other variables. So looking at only one variable and stating by increasing the m*** flow rate of the coolant one will increase the amount of heat transfer is not entirely correct, as the the amount of heat transferred is also dependent on the m*** flow rate and temperature of the air. As I mentioned previously, the amount of energy exchanged must always be equal.
While working at General Motors Diesel Division (now General Dynamics Land System), on the Light Armoured Vehicle we introduced AC into the vehicle and had to test the effects it had on the cooling system. At the same time the radiator fan was changed to save money, but it had inferior air flow and efficiency. The engine cooling tests are done in accordance with a military standard, which dictates the vehicle be loaded at max horsepower via a drawbar pull of a resistive load. At no time did we ever think of increasing coolant flow to increase heat transfer from the engine as that parameter was fixed as far as we were concerned. All our focus was increasing airflow since the space claim had to be the same for the engine/radiator etc. It was a $hit show for sure requiring the need to manufacture a 20’ duct mounted off the exit grill so we could measure the airflow with different configurations of fans, radiator “shroud”, etc. I think we even changed the angle of the ballistic slats on the intake and exhaust grills to help with airflow.

 

Some of you guys just need to learn chill out. Im not a fan of all this hot air, and we dont want things boil over. Can we just put a cap on this and cool it already...

 

^^^^^^^I agree

 

I think this is great discussion. Thanks to all for previous replies and thoughts.

One thing a thermostat also provides is a restriction that increases pressure behind it; generated by the water pump. This helps the localized steam pockets from forming in the engine. That's a good thing. It also helps heat transfer since liquid conducts heat much better than gas (steam). This is a benefit hard to model in theory, but is something we can inherently understand. A large washer can also provide the pressure just like a thermostat.

I do agree that if a radiator has enough capacity for heat removal, then speed of coolant flow should not matter. Too small or radiator just on the limit, is a different problem.

 

I agree with this, and I posted so above in response to G-son's post. Yes, the formula works, it is established fact; if you can just increase the speed of the coolant without introducing any other changes, it will result in an increase in heat transfer efficiency; but changing one parameter typically results in changing something else. So I agree it's not that simple. The point I was making was two-fold: 1 is to dispel the myth that slowing down the speed of coolant through the system to give it more time to transfer heat through the radiator is the wrong approach, and we should stop suggesting that around here. And 2 was in response to a guy that insisted on arguing about it and posting his own ideas as fact. I just wanted to challenge him to back up his claims with something, while I did back up my claims. This isn't my personal theory, I didn't make it up; this is established fact in the field of thermodynamics. Whether it seems intuitive or not, this is established fact. It is physics. To paraphrase a line Gimpyhotrod's signature, they are called the laws of physics, not the friendly suggestions. Q = M x C x Delta T. That is fact, like it or not; understand it or not.

Again, here is a link to an article discussing the subject, it's not some idea I came up with in my head, I found this by going out and looking for information on the subject, the same as anybody who is interested can do just as well as I can. https://lambdageeks.com/m***-flow-rate-and-heat-transfer/ Read the article, while it is not directly discussing engine cooling systems the ideas presented can be directly applied. This line here pretty much says it all: "In any heat exchanger, the heat transfer can be enhanced by increasing the m*** flow rate of the coolant or working fluid." In ANY heat exchanger; that would include an internal combustion engine cooling system.

And @Ziggster this isn't meant as an argument with you, I just wanted to hopefully clarify some of the things posted above. I think we're probably more in agreement than not.

 

Well, I'm not suggesting it, I'm flat out saying that the key to cooling the water in any radiator is how much time that coolant spends in contact with the surface area of the radiator/air.




The amount of time coolant spends in a radiator affects how much the coolant will be cooled. The amount of time coolant spends in a radiator will be controlled by its speed thru said radiator. Since the speed thru the engine is the same as the speed thru the radiator, the radiator must be sized to deal with that speed. Increasing speed does not change the % of time that each droplet is in contact with either surface during a timed interval.

Now thats exactly what I'm saying. ^^^^^^^Nuff Said, I'm done.

 

And you still don't have any source for this other than yourself. Dude, Q = M x C x Delta T. Deal with it.

 

These conversations always remind me of the scene from major league...

 

The ball was hit too high. “Doesn’t quite have the distance”.

 

You refuse to admit even the most basic fact that the longer anything is in contact with something that is a different temperature, more heat will continue to flow from the hotter one to the colder one. Instead you throw out a meaningless esoteric formula that has no actual quan***ies and works only in a controlled laboratory where all the unknowns of individual systems don't affect the outcome.
I live in the real world where you have to deal with all the variables and idiosyncracies that crop up when creating essentially a......" prototype" for some gr***roots builder.
I like to use the formula below. It usually works pretty well for me.............

 

…But that formula has no actual quan***ies in it.

Has anyone heard from @AGELE55 as to whether he’s made any progress on solving his problem?

 

All I know is when I sped up the water pump with a smaller pulley my overheating problems went away. That was after a radiator support to hood seal, 6 blade fan, shroud, hi-flow thermostat etc. All may have helped but none of them came close to alleviating the problem.
Kinda blows a hole in letting the coolant stay in the radiator longer.

 

LOL, you're funny! I'm sure somebody else has already posted this (Ebbspeed?) but while the bolded part above may be true, the rate of heat transfer does not remain constant over time. Go back and look at the formula again, Delta T refers to temperature differential. If you change the Delta T you change the efficiency. The greater the Delta T the greater the rate of heat transfer. Read that again and think about it for a minute, do you understand that basic principal? It's simple really, the greater the difference in temperature between 2 objects, the greater the rate of heat transfer between them. As the temperature of the coolant approaches the temperature of the atmosphere, i.e. the delta T decreases, the rate of heat transfer decreases. That means the efficiency decreases. Are you with me? Because of this, it is more efficient to send the coolant back to the engine to gather another load of heat and return back to the radiator to transfer it, than it is to leave the coolant in the radiator for a long period of time.

This is actually very simple if you just stop for a minute and think about it. Yes, you can leave two substances in contact for a long period of time, and the temperatures will continue to equalize, that is true (see, I am admitting it). But the rate of temperature equalization decreases the closer the temperature of the two substances get to being equal. OK? You still with me or did I lose you? Maybe read that again. If you're still with me, this means the efficiency decreases as the temperatures equalize. OK? Read that again. The efficiency decreases as the temperatures equalize. I'm repeating myself here, but you're missing this basic point, instead of leaving the coolant in the radiator to slowly transfer heat, it is more efficient to send it back to the engine to absorb more heat and return to the radiator to release it. The faster you can do this, the more efficient the system will be. The formula works. Instead of acting like a bulldog protecting a bone, why don't you just try to understand this basic fact. The formula works, because it's science, it's physics. Very smart people with very impressive credentials have already spent a lot of time and resources working this **** out. It's been crosschecked and double, triple, quadruple checked via the peer review process. An entire field of science accepts this as a scientific law. You are not smarter than all these people. You're intuitive gut feeling that goes counter to this law of physics is not correct. Give it up and accept that.