'62 Overheating

[jeff]

Re: Kris: Water flow

Tom,

I noticed you've tried to start this debate a few times with no luck, so I'll bite. There is quite a lot to this but I'll just hit the high spot because I don't write eloquently or type quickly.

You are correct in thinking that your cooling system will not function optimally without a correctly calibrated restriction. But the main reason for the restrictor is to keep the water in the *block* longer, not to keep it in the radiator longer (although it, obviously, will do both).

That may seem a distinction without a difference but keeping the coolant in the block longer allows it to absorb more heat, increasing the temperature differential between the coolant and the ambient air surrounding the radiator conductors and results in more efficient and, therefore, greater heat transfer. This is where the greatest benefit is derived, with the longer radiator contact being a side benefit.

Heat transfer is a function of 3 things: 1) the thermal conductivites of the objects, 2) the temperature differential between the objects and 3) the time that the objects are in contact.

You can't do much about #1 if you are keeping your car original but by increasing the time the coolant spends in the block, you raise the coolant temperature and increase the amount of heat that can be transfered by the radiator per unit of time.

The key to an efficient cooling system is to write an equation which uses the temperature diffential to your maximum benefit on both ends, picking up maximium heat on each pass through the block and then shedding maximum heat on each pass through the radiator because the cooler the coolant is, the faster it will pick heat up (due to the greater temperature differential) as it goes back through the block.

I await dissenting opinions.

JP

[jeff]

Re: Kris: Water flow

Tom,

I noticed you've tried to start this debate a few times with no luck, so I'll bite. There is quite a lot to this but I'll just hit the high spot because I don't write eloquently or type quickly.

You are correct in thinking that your cooling system will not function optimally without a correctly calibrated restriction. But the main reason for the restrictor is to keep the water in the *block* longer, not to keep it in the radiator longer (although it, obviously, will do both).

That may seem a distinction without a difference but keeping the coolant in the block longer allows it to absorb more heat, increasing the temperature differential between the coolant and the ambient air surrounding the radiator conductors and results in more efficient and, therefore, greater heat transfer. This is where the greatest benefit is derived, with the longer radiator contact being a side benefit.

Heat transfer is a function of 3 things: 1) the thermal conductivites of the objects, 2) the temperature differential between the objects and 3) the time that the objects are in contact.

You can't do much about #1 if you are keeping your car original but by increasing the time the coolant spends in the block, you raise the coolant temperature and increase the amount of heat that can be transfered by the radiator per unit of time.

The key to an efficient cooling system is to write an equation which uses the temperature diffential to your maximum benefit on both ends, picking up maximium heat on each pass through the block and then shedding maximum heat on each pass through the radiator because the cooler the coolant is, the faster it will pick heat up (due to the greater temperature differential) as it goes back through the block.

I await dissenting opinions.

JP

[Tom B.]

Re: Jeff: Water flow

Jeff,

Thank you very much for responding. Believe me, I've tried to be diplomatic, even apologetic, about the way I've asked for this info and the way the search has developed. I was given this suggestion by an individual I believe to be knowledgable and have little reason to doubt. In coincidence, it came up twice here, two different ways from two different people. Now, either there is no interest, or people don't know, or nobody wants to touch this with a ten foot barge pole.

Your information appears to fill in some blanks. It also re-directs my focus to more than just what I was assuming was the goal: reducing the speed of the coolant through the radiator. From what I understand in your post, there is a different benefit (in a less obvious way) than I had percieved.

Also, there appears to be a connection to what you are saying about maximizing the efficiency of the coolant (in the block), the efficiency of the radiator that Jerry has mentioned (at the other post), as well as what I have been questioning, the reduction of the coolant speed. Thanks again, Jeff. Tom #24014

[Tom B.]

Re: Jeff: Water flow

Jeff,

Thank you very much for responding. Believe me, I've tried to be diplomatic, even apologetic, about the way I've asked for this info and the way the search has developed. I was given this suggestion by an individual I believe to be knowledgable and have little reason to doubt. In coincidence, it came up twice here, two different ways from two different people. Now, either there is no interest, or people don't know, or nobody wants to touch this with a ten foot barge pole.

Your information appears to fill in some blanks. It also re-directs my focus to more than just what I was assuming was the goal: reducing the speed of the coolant through the radiator. From what I understand in your post, there is a different benefit (in a less obvious way) than I had percieved.

Also, there appears to be a connection to what you are saying about maximizing the efficiency of the coolant (in the block), the efficiency of the radiator that Jerry has mentioned (at the other post), as well as what I have been questioning, the reduction of the coolant speed. Thanks again, Jeff. Tom #24014

[G B.]

Re: Water flow

Jeff -

You're right about the total heat movement being a function of time, but I believe you are double-counting the surface area available for heat transfer by using volumetric flow as the measure of time. I think you will agree with me if you check the units in a sample calculation.

Heat transfer formulas are like a "snapshot" of the heat transfer process. They calculate the BTUs per second going from, say, the block to the water in an instant of time. You must multiply that result by the amount of time the heat transfer is taking place to get the total in BTUs. Actually, integral calculus must be used rather than simple multiplication because the parameters change with time, but you can see my point. There is always water up against the block to receive the heat coming from the metal. Whether it is moving fast or slow, some water still gets the BTUs. The lower the temperature of the water next to the metal, the more BTU's will be transfered because of the higher temperature differential. If the water was not flowing at all, the heat transfer rate would decline over time as the temperature of the water approached that of the block.

The basic function of the radiator is to provide more surface area for heat transfer to cool air than the block can provide by itself. The water moves the heat from the block internal surface areas to the exposed fins of the radiator. The faster the water circulates to get the BTUs from the block to the radiator, the better.

[G B.]

Re: Water flow

Jeff -

You're right about the total heat movement being a function of time, but I believe you are double-counting the surface area available for heat transfer by using volumetric flow as the measure of time. I think you will agree with me if you check the units in a sample calculation.

Heat transfer formulas are like a "snapshot" of the heat transfer process. They calculate the BTUs per second going from, say, the block to the water in an instant of time. You must multiply that result by the amount of time the heat transfer is taking place to get the total in BTUs. Actually, integral calculus must be used rather than simple multiplication because the parameters change with time, but you can see my point. There is always water up against the block to receive the heat coming from the metal. Whether it is moving fast or slow, some water still gets the BTUs. The lower the temperature of the water next to the metal, the more BTU's will be transfered because of the higher temperature differential. If the water was not flowing at all, the heat transfer rate would decline over time as the temperature of the water approached that of the block.

The basic function of the radiator is to provide more surface area for heat transfer to cool air than the block can provide by itself. The water moves the heat from the block internal surface areas to the exposed fins of the radiator. The faster the water circulates to get the BTUs from the block to the radiator, the better.

[jeff]

Re: Water flow

Well, Jerry, it appears no good deed goes unpunished. I had only wanted to kick off Tom's discussion and now I am being asked to defend my 'thermal honor'.

So, regretfully, I'll take time out from my usual pursuits (bigger boats, faster cars, younger women) to post my thermal platform as soon as time allows.

But in the meantime, let me leave you with the New England version of this question which is eternally debated here... "When you get in a car on a cold winter morning, do you get warm sooner if you put the heat on immediately or if you leave the heat off and wait for the engine to warm up?"

Regards,

JP

[jeff]

Re: Water flow

Well, Jerry, it appears no good deed goes unpunished. I had only wanted to kick off Tom's discussion and now I am being asked to defend my 'thermal honor'.

So, regretfully, I'll take time out from my usual pursuits (bigger boats, faster cars, younger women) to post my thermal platform as soon as time allows.

But in the meantime, let me leave you with the New England version of this question which is eternally debated here... "When you get in a car on a cold winter morning, do you get warm sooner if you put the heat on immediately or if you leave the heat off and wait for the engine to warm up?"

Regards,

JP

[G B.]

Re: Water flow

I'm really trying to settle this, Jeff. While you've been making jokes, I've been experimenting.

I've run twenty laps around the house buck-naked at different speeds. As I expected, I am cooler when I run fast if I slowly pour water on my head.

I've got to go now; the police are here.

[G B.]

Re: Water flow

I'm really trying to settle this, Jeff. While you've been making jokes, I've been experimenting.

I've run twenty laps around the house buck-naked at different speeds. As I expected, I am cooler when I run fast if I slowly pour water on my head.

I've got to go now; the police are here.

[jeff]

Re: Water flow

LOL, Geez, Jerry, you didn't even have on a pair of bellbottoms left over from heat transfer class? I hate to think of you running around simulating the restriction. ;)

Actually, I was serious about the question, though. I believe it is closely, maybe exactly, analagous to the cooling issue.

My belief is that you turn on the heat immediately. (Although I don't do it because I'd rather be cold than think of the pistons banging around in the holes any longer than necessary.) Even if delta T is only 1 degree, you're still pulling heat and the sooner you start, the better. I think this is a bit simpler than the cooling equation and I might even remember enough to prove this one if I took enough time to think about it and try to remember. (That's why I hate getting involved in this type of discussion. It's so much easier to just wait for you or Joe to post all the answers.)

JP

[jeff]

Re: Water flow

LOL, Geez, Jerry, you didn't even have on a pair of bellbottoms left over from heat transfer class? I hate to think of you running around simulating the restriction. ;)

Actually, I was serious about the question, though. I believe it is closely, maybe exactly, analagous to the cooling issue.

My belief is that you turn on the heat immediately. (Although I don't do it because I'd rather be cold than think of the pistons banging around in the holes any longer than necessary.) Even if delta T is only 1 degree, you're still pulling heat and the sooner you start, the better. I think this is a bit simpler than the cooling equation and I might even remember enough to prove this one if I took enough time to think about it and try to remember. (That's why I hate getting involved in this type of discussion. It's so much easier to just wait for you or Joe to post all the answers.)

JP

[G B.]

You're right.

At least about the heater. Turn it on right away, just don't let it blow directly on your skin until the discharge air gets above body temnperature. Otherwise the ol' wind chill convection loss will offset any conducted heat.

But you're wrong about the pants. I wore flowered "jams", and now I can only dream of wearing anything with a 32" waist.

[G B.]

You're right.

At least about the heater. Turn it on right away, just don't let it blow directly on your skin until the discharge air gets above body temnperature. Otherwise the ol' wind chill convection loss will offset any conducted heat.

But you're wrong about the pants. I wore flowered "jams", and now I can only dream of wearing anything with a 32" waist.

[Jeff]

Re: Damn, Jerry, that's no fun....

I was hoping you'd disagree because it's very close to the flip side of the radiator deal so I was hoping to catch you playing both sides of the equation.

Everett, who apparently types much faster or has much more free time than I do, has put forth a coherent view of our side. I am still unmoved by your, "don't worry about catching that Btu now, the coolant shall pass this way again" argument. I can't endorse the idea that because the the coolant recirculates you have found a way around heat transfer being a function of time. If you stuck a hose in the radiator neck, yeah okay, I'm on your bus but since the coolant is captive, even though recirculating, I think you have to take the most advantage of every second you have to cool the block and the coolant and I think the max diffential gives max efficiency.

Think of the 2 extremes, no flow it overheats, no time in contact it overheats. So the answer lies somewhere between the 2 and my belief is that it leans toward the less flow/greater temp differential side (in theory, not necessarily in reality for ever single weather condition, design, driving style, age, use and abuse of equipment). I wish I could summon the ambition to try to prove this thing out but I'm way too old and lazy for that.

JP

P.S. If it turns out that we, who retain water, do eventually prevail, I expect to see you at the National Convention, in your 'running suit', installing a thermostat in your car. ;)