Landracing Forum
Tech Information => Technical Discussion => Topic started by: donpearsall on January 06, 2009, 06:45:17 PM
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I thought there was a formula for sizing an engine cooling water tank on this site. I tried searching but can't find anything. Anybody know?
Thanks
Don
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Don,
Perhaps do a search for "BTU"
Use 2.5-3 gallons and you will be fine :-D
Good luck and post your findings..perhaps Dean can supply some info..
J
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I have one from Dr. mayf that he put together in a excel format.. Very detailed and you have to know alot about your motor and setup.
JonAmo
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Thanks John and Jon.
Jon can you send the one you have?
donpearsall@comcast.net
thanks
Don
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Howdy All, :-D
The calculation for water flow and volume of water required to carry away heat from any device or component is pretty straightforward stuff. In my examples we will not use the Calculus although that would allow much more precision. :roll:
GPM = (C x HP) / delta T Where GPM = gal/min, C = constant which is 1.00 for water, delta T = Temp at end - Temp at start with Temp in degrees F.
Time = (Mh20 / Hpbtu) x delta T Where M = wt of water in lbs, Hp in BTUs and 1Hp = 42.44BTU/min, delta T as in formula previous.
Hint: cooling system heat load is about 1/3 of engine power at the flywheel in BTUs 8-)
Hope that helps. :lol:
Regards to All, :cheers:
HB2 :-)
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Sorry.....I forgot to add that water is about 8.34 lbs/gal and the calculations are for just plain water. :oops:
Regards,
HB2 :-)
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Thanks much Harold. Looks like a pretty good formula for estimation I will try to plug this into Excel and see if I can get some results.
Don
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Harold (HB2),
I must have messed up somewhere.. The formula said I needed 28 gallons ??
(using only water, no additives)
600 HP SBC
Launch Temp 170 degrees
Desired max temp at end 210 degrees
Charles
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Harold (HB2),
I must have messed up somewhere.. The formula said I needed 28 gallons ??
(using only water, no additives)
600 HP SBC
Launch Temp 170 degrees
Desired max temp at end 210 degrees
Charles
try it with starting temp of 98....
there is no need to preheat all the water before you run... unless your team plans showers after the run
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What Harold posted is good for a starting point. But there is much, much more to it.
When you ignite the fuel/air mixture you produce heat. Heat produces power. In a perfect world we would insulate the engine and keep all of it. Heat also makes stuff melty. I know, the technical terms like “melty” are hard to follow.
Between melty and cold is a point that makes the most horsepower . . . without melting. To keep it at this temperature we have to transfer the excess heat out of the engine.
Temperatures in the combustion chamber of the engine can reach 4,500 F, so cooling the area around the cylinders is critical. Areas around the exhaust valves are especially crucial, and almost all of the space inside the cylinder head around the valves that is not needed for structure is filled with coolant. If the engine goes without cooling for very long, it can seize. When this happens, the metal has actually gotten hot enough for the piston to weld itself to the cylinder. This usually means the complete destruction of the engine.
The Volkswagen engine, and others, simply use air. Most use water.
The heat in the engine has to transfer through the water jacket to the water and from the water to the air.
It’s perfectly simple: q = m(DT)Cp
amount of heat transferred = mass x change in temperature x specific heat.
If your head didn’t explode looking at that formula, do a Google search on heat transfer to learn more. Way more than can be discussed here.
To transfer the heat from the engine to the water, we need to know how well different materials transfer heat.
Thermal Conductivity
Thermal Conductivity is the amount of heat a particular substance can carry through it in a unit of time.
Copper 401
Gold 318
Aluminum 237
Brass (37/15 Cu/Zn) 159
Iron, pure 80.4
Carbon Steel 54
Bronze 50
Lead 35.3
Titanium, pure 21.9
Stainless Steel 16.3
Glass 1.2 - 1.4
Concrete 1.1
It’s no wonder we don’t make blocks out of concrete! It makes a big difference whether your block and head are aluminum or cast iron when it comes to cooling. A copper radiator sheds heat better than an aluminum one, but you pay a weight penalty. Not to mention a copper radiator would be massively expensive.
Once we transfer the heat through the jacket, we have to carry that heat out of the system.
Specific Heat Capacity
Specific Heat Capacity is the amount of heat a particular substance can hold.
Water 4.18
Methanol 2.55
Ethanol 2.48
Glycol, Antifreeze 2.38
Liquid Nitrogen 2.04
Steam (at 110°C) 1.97
Benzene 1.72
3M Flourinert FC-43 1.47
Air (at 100°C) 1.00
Freon 11 0.87
It’s no wonder we use water to move the heat out of the system. It by far carries the most heat. Note the difference between water, steam, and air. Air cooling requires a massive flow of air. If your system overheats and turns the water to steam you lose half of the cooling capacity instantly. Note that the antifreeze lowers the capacity of water to carry heat.
But it is more than just heat.
What we want from the cooling system liquid? Water and antifreeze does this:
1. Carry heat out of the engine
2. Lower the freezing point.
3. Raise the boiling point.
4. Resist corrosion.
Water alone will carry heat out of the system. Additives reduce the capacity of water to carry heat.
Antifreeze lowers the freezing point. Antifreeze also raises the boiling point. (Anti-boil would be a better term. Compounds that achieve both are called colligative agents.)
A 50/50 antifreeze mixture will lower the freezing point to -35F and raise the boiling point to 223F. A 70/30 mix will lower the freezing point -67F and raise the boiling point to 235F.
The boiling point of a liquid is not only the temperature, but the pressure of the liquid. Raising the pressure raises the boiling point. Water boils at 212ºF at atmospheric pressure. A steam boiler at 3,200 psi produces 705ºF steam. At slightly lower temperatures you could have 650ºF water.
The engine is producing temperatures far in excess of 212ºF. If the water is allowed to turn to steam all of the heat capacity goes away and the engine melts. Raising the boiling point in a pressurized system allows us to transfer more heat without boiling the water.
10 psi raises the boiling point to 240ºF. 20 psi raises the boiling point to 260ºF. 30 psi raises the boiling point to 275ºF. Automobile systems run from 9-15 psi. Racing radiator caps run as high as 28-32 psi. The radiator cap serves as a pressure relief valve in case the pressure exceeds the cap rating. Can you run higher pressures? Sure. You can design any system pressure you want, just keep it in mind that you are building a pressure vessel.
The highest point in the system must be a bleed valve. There must be no air in the system.
For racing, the antifreeze isn’t as necessary as you would think.
Corrosion isn’t a problem if you use distilled water. Distillation involves boiling the water and then condensing the steam. Distillation produces very pure water. You know that salt water corrodes everything. That’s because the salt with water allows a galvanic reaction between dissimilar metals. Pure water doesn’t have anything in it to allow a galvanic reaction, or minerals to cause buildup.
What about those freezing days at El Mirage and Bonneville. Antifreeze might have been useful here. You always wanted to heat that trailer, right? A block heater would also be an answer. Draining the system and refilling before racing is another option.
What temperature should the water be?
Wrong question. What temperature should the engine be? Easy! What temperature will it melt at? Because you have to solve for all of the equations in a heat system, it may be something the F1 guys do all the time with unlimited engineers and computers. Some of the high buck LSR guys may be doing it. Dr. Goggles posted: “No science is better than bad science” That’s great if you understand the science, have the tools and computers to analyze all of that and come to a conclusion. In between rocket science and “It ain’t melted so it must be good.” is where most of us are stuck.
The actual answer would be for the particular system you are running. The Hayabusa guys and the BBC guys have no doubt worked out solutions based on trial and error and the number of similar engines out there.
I would hazard a guess and say that there are as many running too cold as too hot. Should you heat the water before the run? Yes, yes, yes! The heat that it takes to warm up the water is power the engine will never see.
What if I can’t get rid of enough heat?
As you put more heat into the system, easy with a turbo or supercharger, you have to take a higher volume of heat out. If you are at the maximum temperature and pressure designed into the system you need to take more heat out with a larger radiator, or increase the flow rate so the water can carry more heat to the radiator.
What are the cooling media options? (Rules not considered.)
This is all I could find under any type of cooling. Industrial, aerospace, overclocked CPU’s, you name it. The reason for mentioning it, is there is no reasonable non-flammable substitute for water.
Air
Air will not freeze or boil, and is non-corrosive. However, it has a very low heat capacity.
Water
Water is nontoxic and inexpensive. With a high specific heat, and a very low viscosity, it's easy to pump. Unfortunately, water has a relatively low boiling point and a high freezing point. It can also be corrosive if the pH (acidity/alkalinity level) is not maintained at a neutral level. Water with a high mineral content (i.e., "hard" water) can cause mineral deposits to form in system plumbing.
Glycol/water mixtures
Glycol/water mixtures have a 50/50 or 60/40 glycol-to-water ratio. Ethylene and propylene glycol are "antifreezes." Ethylene glycol is extremely toxic. Most glycols deteriorate at very high temperatures. You must check the pH value, freezing point, and concentration of inhibitors annually to determine whether the mixture needs any adjustments or replacements to maintain its stability and effectiveness.
Hydrocarbon oils
Hydrocarbon oils have a higher viscosity and lower specific heat than water. They require more energy to pump. These oils are relatively inexpensive and have a low freezing point. The basic categories of hydrocarbon oils are synthetic hydrocarbons, paraffin hydrocarbons, and aromatic refined mineral oils. Synthetic hydrocarbons are relatively nontoxic and require little maintenance. Paraffin hydrocarbons have a wider temperature range between freezing and boiling points than water, but they are toxic. Aromatic oils are the least viscous of the hydrocarbon oils.
Refrigerants/phase change fluids
These are commonly used as the heat transfer fluid in refrigerators, air conditioners, and heat pumps. They generally have a low boiling point and a high heat capacity. This enables a small amount of the refrigerant to transfer a large amount of heat very efficiently. Refrigerants respond quickly to solar heat, making them more effective on cloudy days than other transfer fluids. Heat absorption occurs when the refrigerant boils (changes phase from liquid to gas) in the solar collector. Release of the collected heat takes place when the now-gaseous refrigerant condenses to a liquid again in a heat exchanger or condenser.
Silicone oils
Silicones have a very low freezing point, and a very high boiling point. They are noncorrosive and long-lasting. Because silicones have a high viscosity and low heat capacities, they require more energy to pump. Silicones also leak easily, even through microscopic holes.
Fluorinert $770 for ¾ gallon. Nuff said.
Water pumps
Electric or mechanical driven pump? Mechanical pumps take horsepower to run. Electrical pumps generally don’t have as much flow. Does it have to be a racing pump? Not necessarily. There are tons of commercial pumps of every flow capacity out there. Racing pumps are usually lighter. Calculating the correct flow and the correct pump is another area that is very tough to calculate.
On an open system, like a pond, placing the pump at the lowest point is necessary to use all of the water. On a closed system in an engine, the liquid level never changes so it isn’t as important to have the pump at the absolute lowest point. Most automotive systems don’t. Once you fill and bleed the system the pump is going to have water in it and priming it isn’t a problem. The pump does need to be feed with a large enough line so that it doesn’t starve and start cavitating. Because of the pressure in the system from heat, cavitation isn’t as much as a problem. But you can still starve it.
How much “head” should I have? Head or discharge pressure, is the difference between the output pressure and the inlet pressure. That differential pressure exists no matter what the system pressurization from the radiator cap might be. The pump is attempting to push water (never pulled.) through the engine. The choke point in the system will determine what that pressure will be. If you change to a larger pump that pressure might go up without much increase in flow. The water is heated by the engine and then cooled by the radiator and that will create a small pressure differential by itself. Once the water is outside of the engine the system has to be large enough to not restrict flow to the inlet of the pump. Bigger is always better. The differential pressure doesn’t matter as much as having the correct flow.
Tank or radiator?
A tank isn’t really required if the system will remove enough heat. The tank would act as a thermal reservoir to delay overheating. If overheating isn’t a problem then you don’t need a tank.
Do you need a radiator? That depends on the cooling needs of your system. Some participants are running a tank with no radiator because they need ballast anyway. Aero factors come into play also. The air has to come into the radiator from a pressure point and that can cause drag. The air has to exit at a low pressure point, and that may not be easy. Can you run a radiator without putting outside air through it? Sure. The heat is going to build up in the engine bay, but on a short run that might be possible.
A radiator is a type of heat exchanger. It is designed to transfer heat from the hot coolant that flows through it to the air blown through it by the fan.
Most modern cars use aluminum radiators. These radiators are made by brazing thin aluminum fins to flattened aluminum tubes. The coolant flows from the inlet to the outlet through many tubes mounted in a parallel arrangement. The fins conduct the heat from the tubes and transfer it to the air flowing through the radiator.
The tubes sometimes have a type of fin inserted into them called a turbulator, which increases the turbulence of the fluid flowing through the tubes. If the fluid flowed very smoothly through the tubes, only the fluid actually touching the tubes would be cooled directly. The amount of heat transferred to the tubes from the fluid running through them depends on the difference in temperature between the tube and the fluid touching it. So if the fluid that is in contact with the tube cools down quickly, less heat will be transferred. By creating turbulence inside the tube, all of the fluid mixes together, keeping the temperature of the fluid touching the tubes up so that more heat can be extracted, and all of the fluid inside the tube is used effectively.
Top fuel engines do not have coolant. The entire cooling is provided by the incoming fuel charge.
If you really need more here's a class:
Engine Cooling Design: A System Engineering Approach
Provider: Society of Automotive Engineers – $725
Prerequisites
Prior exposure to thermal sciences at the undergraduate level is recommended.
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Harold (HB2),
I must have messed up somewhere.. The formula said I needed 28 gallons ??
(using only water, no additives)
600 HP SBC
Launch Temp 170 degrees
Desired max temp at end 210 degrees
Charles
If you can put that much in the car I'd do it for future HP, and don't forget it can help with ballast if you need that. We ran about 16-18 gal until last year and I estimate we were making 750 HP and it worked until 07 when we upped the boost a little and had some other problems and the water temp gauge was pegged at 240 at the end of the run. Last year a new tank took the water capacity to around 31 gal. and we had no problems with even more boost and I feel we were making about 850 HP.
Now this is on a worst case engine, one running blown gas where you are building the most heat. We have been running the Snow water injection and I credit it for a lot of our success with this combination.
I'm running 16 gal of cooling water and 16 gal for intercooler ice water in the lakester. Probably more than I'll need, but if I ever get the chance to run a really good 'busa on blown gas I might be glad I have it at the 5 mile.
c ya,
Sum
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I have a radiator (with a 28# cap) in a enclosed 11 gallon tank---on warm up I warm just the radiator and block. On the start line I warm up to operating temp---shut down---then pump the tank full---when I get back to operating temp---then turn the BIG Mezier pump that circulates water from the rear 25 gallon storage tank so far it will stay about what ever we turn the pump on.---When I forgot to turn the pump back on ---it hit 240 in the last mile----going to install an auto 190 deg back up switch.---cooling around 900+ hp
11/21/2010 Update
We went back to a mechanical switch---the last thing the guy closing the canopy does--- before closing the canopy is turn on the BBC Mezier pump!
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Cool information guys. I like SPARKY's approach. 8-)
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Dean,
Great post! Some really good info there. Just to add a little more I would like to also mention a property of water called "the heat of transformation" which is what happens with fluids when they change from one state to another, i.e. liquid to steam in the case of water. When water changes from liquid to steam at 212 deg F at STP (Standard Temperature and Pressure) it adsorbs about 7 times the amount of energy that it adsorbs by a 1 degree temperature increase when it is liquid. This is a pretty valueable property of water in that if you have a hot spot in your engine, typically in the exhaust valve area, if it is hot enough to make the water into steam the amount of heat adsorbed will be increase by 7 times. Now to take advantage of this you need a very high volume water pump, again using Stu Van Dynes rule of 10 gpm/100 hps. The high volume pump will not allow the water that is transforming to steam to stay at the hot spot because of the high velocity that it is traveling thru the cooling system.
We are all pretty much limited as far as materials go for what ever engine we choose and it is obvious from Deans post that water is the very best fluid for heat transfer and the only variables that we have available to us are the volume of water in the tank,the flow rate of the water pump and the pressure that we run the system at. Lots of advantages for going to a high pressure system but the water tank design can become more of a challenge. Using a round tank like Hooley does in his 974 car is certainly the easiest as this design with formed ends is a very good pressure vessel, large flat sided tanks want to become round at almost any pressure over 15-20 psi unless they are fabed from heavy material and internally braced.
Rex
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"water wetter" what do we know about this stuff? (redline, engine ice, enc.)
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perhaps Dean can supply some info..
J
Thanks Dean.. :cheers:
Also thanks to the other folks as well.
John
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Wow, I didn't realize that I was lighting a brush fire! :-D :evil:
Please consider the following points for sensible design goals on a cooling system for Bonneville:
The boiling point of water at Bonneville will be about 200F (at atmospheric pressure there). The system (unpressureized) proposed was a volume of water, so the temp of the reservoir at the end of a run should be less than 200F (probable target about 175-190F). That is why I listed the formula for a reservoir.
The flow of water across the heat generator (engine) should be in general much more than those little water puppy type units. The water flow carries away heat from the backside of the combustion chamber and the exhaust valves so that the chamber is less prone to encourage incipient detonation. That is why I listed the simple formula for water flow in gallons per minute (GPM). It is a pretty good rule of bruised thumb to use at least 10GPM/100Hp for heat dissipation. 8-)
It was well stated when it was said that there is much more to an accurate study of the thermodynamics of a water system, but I wanted to try and make it both understandable and usable without complex mathematics. :roll:
As to the question by the Cajun Kid: One would need a pump supplying about 106GPM with a reservoir of about 38 gallons (316lbs) to dissipate the heat from a 600Hp engine that would increase the temp from 100F to 180F in about 3minutes. That considers no cooling other than the mass of the water and with atmospheric pressure on the reservoir. :wink: Things change appreciably when pressurizing the system and dissipation of some of the heat to atmosphere via forced or natural convection.
Hope that hasn't muddied up the cooling water issue too much. :? It makes one appreciate how much heat a radiator actually dissipates in the cooling system and how nice the additional airflow across the radiator works at speed a;beit with some considerable drag involved.
Regards to All,
HB2 :-)
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I for got 2 things:
1. aways use distilled NON MINERALIZED water---you do not want the minerals forming ceramics or deposits in you block and heads.
2. in my opinion you need the PRESSURE from a mechanical water pump---step it down where it doesn't turnnover 5500 at max rpm---my Alt and water pump are geared to turn 5200 at 8000.
Thanks to Mr. Mack, Mr. Jones, and Stewart water pumps for the education and desigh help.
I will be adding a feature this year thanks to Dave D.: I will be runing water that normaly would be going to the heater in a car through my dry sump tank to help in heating the oil at warm up and cooling the eng. at WOT.---trying to get the systems ready for:
ARTIFICAL Density Altitude---Tom B's term---lol :cheers:
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Specific Heat Capacity
Specific Heat Capacity is the amount of heat a particular substance can hold.
Water 4.18
3M Flourinert FC-43 1.47
Fluorinert $770 for ¾ gallon. Nuff said.
At a previous job we used to buy the 3M Flourinert by the gallon jug. There are different versions with different temperature ranges, and I wondered at the time if it couldn't be useful to make engine cooling in two tanks, one that is heat soaked to keep the engine at operating temp, and a second containing really cold Flourinert and a flat plate heat exchanger. Would require two water pumps, but that would be a plus as you could keep the engine water at constant temperature by controlling the water pump to the heat exchanger.
You can't go lower than 32 on the ice bath, but with the Flourinert you could go colder than you could achieve with dry ice. Liquid nitrogen would be to cold unless carefully applied. Lower specific heat capacity only matters if you can't go really cold.
Dean's comment about Nuff said says it all for my budget though!
I guess the idea of two tanks would still be valid, but more plumbing and more stuff to go wrong.
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Thanks to Harold and others. Like Rex said “good information”. :wink:
I would like to reinforce what Harold said because it was not part of his formula and was a byline whose importance may be missed. 2/3 of the heat goes out the exhaust pipe! You don’t need to build in cooling capacity for it. You only need to cool 1/3 of crank HP. So consider using 0.3HP in his formula. When boosting with a turbo remember; most of the heat is used to drive the turbine and then is exhausted. You don’t need to add 100% of the added boost HP. Don't minimize what Rex said. The phase change from a liquid to a gas (i.e., making steam) is endothermic. It requires a tremendous amount of additional heat and is sometimes quite useful as Rex indicated.
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Hey Saltfever, that is a good point about the heat out of the exhaust. I imagine there are other heat dissipation factors too, like radiation of the block.
Thanks to everyone who is contributing to this. I am learning a lot.
Don
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Harold, I am not understanding how you got the solutions to Cajun Kid's parameters.
Horsepower - 600
Delta Temp - 80
You said his GPM should be 106, however using the formula given was GPM = (C x HP) / delta T (or GPM = (1*600)/80 in this case), the GPM is 7.5
Please explain. Should I go back to 7th grade?
Don
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Harold what does the subscript h20 stand for in the time formula? (Mh20)
H2O is Water
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Please note that the portion of engine power at the flywheel that is considered a cooling system load is approximately 1/3 or .33 x Hp at flywheel. Then it must be converted to BTUs. 42.44BTU/min = 1 Hp. :-D
So, 600 / 3 = 200. 200 x 42.44 = 8488. 8488 / 80 = 106.1GPM :-o
Listed previously is correct that Mh2o is Mass in pounds of water. :lol:
Hope that helps stuff be more clear. :wink:
Yeah, I know that many folks are getting by with less water flow and less volume, but I would often be at odds with the way that things are commonly done. :-P
When you calculate something based on many assumptions, you are apt to get varied results. Such as how long will you be needing to dissipate 1/3 of the power to the cooling system and other variables. Hopefully this stuff will help and not hinder your efforts on the salt. :cheers:
Regards to All,
HB2 :-)
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OK, thanks. I did not realize that the HP should be in BTU in GPM formula.
Don
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Don, thanks for the question.
Harold, Thanks for the answer walk through.
Everyone, thanks for the info share.
Geo javascript:void(0);
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Just to elaborate on a single point. In WWll, The Heinkel 100 used an evaporative cooling system and completely did away with radiators, using the wings instead. The thing went 394.6 MPH in 1938.
http://en.wikipedia.org/wiki/Heinkel_He_100
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Just to elaborate on a single point. In WWll, The Heinkel 100 used an evaporative cooling system and completely did away with radiators, using the wings instead. The thing went 394.6 MPH in 1938.
http://en.wikipedia.org/wiki/Heinkel_He_100
Interesting read.......EXPLOSIVE RIVETS? !!!! Had to google that one. Jerry
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"EXPLOSIVE RIVETS? !!!! Had to google that one. Jerry"
Jerry;
Expolsive rivets weren't that uncommon in the US aircraft industry years ago-- you could even find them on the surplus market until a few years ago. They were an adaptation of the standard solid aluminum rivet except that the end of the shank was hollow and filled with a mild explosive compound. To set them they were inserted into a hole and then a heater looking like a big soldering iron was placed on the head and the heat detonated the explosive, flaring out the rivet and setting it in the hole.
These were used in "blind" applications (there was no access to the backside) where a rivet could be bucked. The development of modern blind rivets and pulling tools made explosive rivets obsolete.
Regards, Neil Tucson, AZ
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The memory goes when you get old but IIRC GM used some explosive rivets on the grills of some models. You had to go to the dealer for them if you needed to change the part. Keep in mind I have been wrong before. LOL
Ron Gibson, Omaha NE
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Re: Water Wetter...
We used it in the Arrow MC Streamliner both in the pressurized system, 24psi cap (engine and heat exchanger) .4gal.
And in the open (unpressurized) reserve coolant tank, 7.5gal.
(1) to inhibit corrosion, stainless tank, alloy heat exchanger & engine, steel clamps, etc.
(2) it raises the boiling point of water a few degrees.
We warmed the engine to approx 170deg prior to a run using a bypass thermostat system (credit to Rick Byrnes).
At the end of a 5 mile run the engine coolant temp was usualy around 220deg. and the reserve tank was too hot to touch, but the coolant was not boiling.
This with 200hp.
Good stuff in my opinion
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You don't see on the instruction?
_________________
Scum suckin bot
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Fiddle-sticks!!!!! darn instruction ,!!!! of course! I no see on......how silly of me ............
Now,is it just me or do I smell a web crawler program that found "COOLING" , and came up with this?..........
a pox on your refrigerated water cooler I say :evil: :evil: :evil: :evil: :evil:
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In reviewing some of the foregoing calculations that followed from the information provided by Harold Bettes, there appears to be confusion arising from a slight misstatement of one of the formulas and the units of measurement required. In hopes of clarifying this, they are restated below with a little more explanation of what they represent and the units required.
The first formula basically calculates the flow rate required to achieve a given temperature rise given a stated energy input. That is, what flow rate is needed to keep the water temperature within desired bounds while going through an engine that is rejecting heat to the coolant at a particular rate.
GPM = 5.089*(Hp)/((c)*(To - Ti)) where:
GPM = gallons per minute
5.089 = (42.44 Btu/min)/(8.34 lb/gal (for water)) conversion factor for units
Hp = horsepower put into the coolant, about 1/3 of the engine’s flywheel horsepower
c = specific heat of the coolant (Btu/lb-F) = 1.0 for water
To = temperature of outflow (degrees F)
Ti = temperature of the inflow (degrees F)
Using this to recalculate the example situation from before, (HP = 200, To=180, Ti=100) it is found that the flowrate is 12.72 GPM. This is much more reasonable than the 106 result from before, as the 106 was not gpm, but lb/minute of water.
The second formula determines what volume of fluid is needed to keep its temperature rise within the desired limits given exposure to a heat input for a period of time. How big does the reservoir need to be?
V = 5.089*(Hp)*t/((c)* (To - Ti)) where variables are as identified above and t is the time of exposure in minutes and V is volume in gallons.
-or, if the variable quantities remain the same as the first formula, (and rather intuitively):
V = GPM*t
Again, using the example with t = 3 minutes, the volume is found to be 38.16 gallons, which agrees with the previously determined result. Interestingly, this method effectively assumes that the reservoir volume is only circulated through the engine once, that no mixing occurs in the reservoir, and that no heat is lost out of the system piping or tank.
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I have run my water tank (no radiator) on my bike for two seasons now. I am pleased with how well it works and does not overheat even when running the full 5 mile course using about 300 hp. My tank is about 9 gallons and has a pressurized cap. When the run starts, the thermostat is probably just beginning to open due to idling and at the end of the run (about 3 minutes) the temp at the top of the tank is about 200 and 180 at the bottom (where it flows back to the engine).
There is a lot of air cooling going on, I am sure, so the formulas do not apply verbatim. Just thought I would chime in with some real world results.
Don
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I knew this was a mistake, and did it anyway.
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The use of absolute temperatures to the fourth power pertains only to radiant heat transfer, not conductive.
Panic’s points 4,5, and 6 are generally correct and as Harold stated in the beginning, the method he proposed is an easy to use approximation of the actual heat transfer problem, intended to get into the right ballpark on water volume, and is not a definitive analysis. However, it does a pretty good job, as witness the correlation with actual as-used results of a number of lsr practitioners.
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Running loaded on the chassis dyno and putting out 2300 rear wheel hp it doesnt take the long to boil water in our 28 gal tank [ not full ] but at Bville where we can't apply full throttle untll in high gear and our last run that
ended after 3 miles at 294 mph we had no overheating problem and never have had a heating problem.
Blown gas is the worse for heat, roots blowers more than others [centrifugal for us] and alcohol runs much cooler.
Using 880 hp and 1.5 min in the volume equation, the # is 84 gal, that might be right for the dyno but overkill for Bville. We use about 20 gals.
JL222
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We did a test to see how much water would flow through the engine with our water pump in the time that the engine would run during a pass at Bonneville. I made the water tank so that it would hold more water than we could pump through the engine in one pass on the course. We kept a supply of water in our pits and we changed out the water if we wanted to make another pass. I think it was a little over 30 gallons of water. 400 cubic inch, 871 blown engine on gasoline. Actually I over estimated the amount needed as in the test we did not allow for the thermostat opening and closing. I thought it was best to error on the safe side and the extra water was just ballast anyway.
John
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The use of absolute temperatures to the fourth power pertains only to radiant heat transfer, not conductive.
Panic’s points 4,5, and 6 are generally correct and as Harold stated in the beginning, the method he proposed is an easy to use approximation of the actual heat transfer problem, intended to get into the right ballpark on water volume, and is not a definitive analysis. However, it does a pretty good job, as witness the correlation with actual as-used results of a number of lsr practitioners.
Well I'll never know what his points of view were because he erased them faster than a speeding bullet. This is a good thread. I wish he wouldn't do that. :x Why not give us the benefit of all points of view? :-(
IO thanks for spelling out the values of the constant. It is rare that anyone will be so considerate, or perhaps they don't know how the constant was derived. Anyway, it is great to spell out the argument because sometimes curious minds want to know more than the quick result.
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To assuage Saltfever’s sense of loss....
Panic’s points dealt with a more detailed description of the cooling system operation. One was that a given coolant flowrate would probably only be “correct” at one point during a run. It would likely be excessive during the early part-throttle operation and then later somewhat deficient for extended full-throttle running. Secondly, the mixing of hot returns in the reservoir could raise the reservoir water temperature some, making the absorbtion of heat from the engine less efficient. And thirdly, made a case for using ice in the reservoir due not only to its low temperature but the latent heat of formation of ice which adds to the heat capacity available.
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For anyone who's interested, there is an interesting article in the latest Air Classics magazine Vol 46 number 12 pages 44,45 by Bruce Lockwood on cooling related to Reno air race unlimited aircraft.
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I.O.: Thank you for sharing what was erased by Panic. All good points and worth considering during the "design phase".
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I have run my water tank (no radiator) on my bike for two seasons now. I am pleased with how well it works and does not overheat even when running the full 5 mile course using about 300 hp. My tank is about 9 gallons and has a pressurized cap. When the run starts, the thermostat is probably just beginning to open due to idling and at the end of the run (about 3 minutes) the temp at the top of the tank is about 200 and 180 at the bottom (where it flows back to the engine).
There is a lot of air cooling going on, I am sure, so the formulas do not apply verbatim. Just thought I would chime in with some real world results.
Don
9 gal?!
Where does the tank FIT? Under the motor? or is it shaped like an amoeba?
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Caveman, the tank is shaped kind of like an inverted foot and fits over and in front of the rear tire. A lot of credit goes to Fred Vance as he gave me the idea for mine. I think he runs about the same setup and had no overheating either. Besides, it adds about 90 pounds of tire ballast which does not hurt either.
Don
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I read with interest this whole thread.... we have been using thermostats in our various systems over the years.... this allows the engine to be brought up to operating temperature while not to any extent raising the temperature in the resevoir..... we also have a screw on cap that covers a 4.5 inch diameter filler spout into which we add several bags of ice..... effectively increasing the temperature differental by A LOT.... At Speedweek, during summer heat, we found that 80 lbs of ice would leave the water in the reservoir at about 140F after a 5 mile run.... the thermostat was actually still cycling!.... that was with a 670 HP small block Chevy.... we never got our new engine combo shaken down at Speedweek 2010 though.... but at the World Finals, when it was much cooler, we were using about 50 lbs of ice with treservoir temperatures in the 150F range.... the humorous part of this is that it costs us more for ice every run than it costs us for fuel!
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Fastman
How many gallons is your water tank and what class is your engine .
John
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Fastman
How many gallons is your water tank and what class is your engine .
John
John,
The car is a C/GL 355 to 370 cu. in. Chevy or Dodge.... The tank is about 32 US Gallons we run with a bit of air space too.... I went looking on this computer to see if I had any pics but I don't and, since I am 3000 miles from home, I can't take any pics... The tank is 16"Long X 18"Wide X 24" Tall... we had a hose barb on the bottom that connected to the water pump intake..... on the top of the tank, we had a plenum made of 2" square aluminum billet about 6" long into which 4 lines from the four corners of the heads flowed. There was a 1/8" NPT hole on one end of the plenum for a temperature probe and on the opposite end, a 5th port that had a bypass line going down to the bottom of the tank. The features of this plenum block are that it was bored to 1.50" diameter and at one end bored 90 degrees to the main hole is the return to tank porting with a 4 hole mounting flange and a shallow counterbore to locate a stock thermostat.. We added a 1/2" thick flange to the tank with a threaded 4 hole flange pattern to which the plenum gets bolted. It works really well unless you put the thermostat in backwards (ask me how I know that one ;-)...)
If you want a sketch, P/M me with your email address and I will whip something up and send it to you.
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By the way, we don't run the setup this way on the Dodge engine.... we made things way more complicated by adding a heat exchanger into which the engine coolant is close looped.... we have an electric thermostatically controlled motor/transfer pump that pumps the iced cooling water from the tank to the heat exchanger .... we were of the mindset that controlling the engine temperaturewithin +/- 3degrees is better....because that's what they do in NASCAR.... and to further complicate things, we added a 3rd transfer pump, a small ball valve and a check valve so that, after the engine is shut off, we can leave the electric pumps moving water through the engine and the heat exchanger to keep the cylinder head temperatures from spiking too high....
We also run a similar system on our Vega with a 432 cu. in Big Chief Chevy....but without the after run transfer pump the water tank on the Vega is mounted flatter and is baffled.... it holds 30 Gal of water/ice....and works quite well too.