# Viability of Heat Pipe technology in Internal Combustion Engine Cooling

1. Dec 2, 2009

### gazza23

Hi there, my first post on this forum and I hope its in the right place !

My question is this, in an exisitng air-cooled motorcycle engine what is the viability of using heat pipe technology to cool exhaust gas temperature? Using heat pipes to remove heat from exhaust valve areas to external heat sinks in order to reduce exhaust gas temperature to improve both emissions levels and engine performance?

Are heat pipes able to remove engine heat fast enough to make this possible?

2. Dec 2, 2009

### Mech_Engineer

I'm not sure cooling the area around the exhaust valves would increase engine performance, but heat pipes are very effective at transferring heat and could theoretically be used for this function.

The problem would be that air is still be used to cool the engine, so to achieve a higher rate of cooling on the engine (heat pipes or no) you need to increase the number/surface area of the heatsinks being used. This increases the size and weight of the engine.

3. Dec 2, 2009

### gazza23

Have a look at this pic, the debate is if this heat pipe technology is being used on this concept motorcycle at all, I'd like to think yes - I'd love to hear from anyone who could either argue for or against it

Apologies for the size of the images but I cant seem to edit the size anywhere. What you see on both bikes are what appear to be heat sinks connected to the cylinder heads via a tube which I assume is a heat pipe. ???

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4. Dec 2, 2009

### Danger

I really can't say without taking the thing apart. Truth be told, that looks more like an electrical conduit to me.

5. Dec 2, 2009

### Mech_Engineer

It doesn't look like a heat pipe to me, nor does it seem to be attached to a radiator. Like Danger mentioned it looks more like an electrical conduit, perhaps holding the spark plug wire.

6. Dec 2, 2009

### Topher925

If that is a heat pipe (and I don't think it is), its a poorly designed one. Heat pipes, unlike heat sinks or cooling fins, do not conduct heat. Instead, they transport it using using a working fluid. When this fluid condenses at the condenser of the pipe, it must return to the evaporator via its self generator capillary pressure. Because of this, heat pipes can only be made in small lengths while still being effective. This makes them a good choice cooling things like microprocessors but bad for cooling larger things like engines.

The only exception to this is oscillating heat pipes which contain no porous material and work by the oscillation of the working fluid alone. However, these can only be made using micro-sized tubes and aren't very applicable to engines either.

7. Dec 2, 2009

### Staff: Mentor

....also useful in places where you have a height difference that enhances for natural convection, such as in a horizontally mounted air conditioning unit coil.

I could see a heat pipe being used on a boiler, to preheat incoming air while cooling exhaust. But usually, they use air-to-air heat exchangers.

8. Dec 3, 2009

### Ranger Mike

why would you want to cool the exhaust pipe ( header)..it will only HURT performance...you want the exhaust HOT to keep up velocity and better savange the spent fuel air mixture. in fact the trend in racing is to go to stainless steel tubing to do this..other options are powder coating and thermal tape wrapped around the exhaust pipe to hold in heat. The vavle seat should be just fine as long as you do not lean out the fuel to air ratio..

9. Dec 4, 2009

### gazza23

I am told that exhaust gas temperatures are linked to emissions. That by cooling exhaust gases that you can lower emissions (Please feel free to correct me if I'm wrong).With the latest tightening of EU legislation on emissions controls, this apparently limits engine horse power (so I am told and from what you have just posted above). The theory or rather thinking behind cooling the exhaust valve area is to lower emssions after increasing the engine's horse power and in the process finding a happy medium between the two.

So, by using flexible heat pipe tech to cool exhaust valve areas will lead to a drop in performance. However, if an existing engine design were to be "tuned" to push out a lot more HP, then cooling tech applied to drop the emissions(which have also increased along with HP) to within legal requirements but not to drop the HP to below the orginal "untuned" state of the same engine, is this all a bit far fetched or at all possible?

Here is a youtube video of one of these concept bikes, it will shows these "heatsinks" in more detail: http://www.youtube.com/watch?v=4WiNeOZXAqE"

Last edited by a moderator: Apr 24, 2017
10. Dec 4, 2009

### Ranger Mike

Will cooling exhaust gases lowers emissions. this goes counter to engine development since the EPA initiated emission standards in the 1970s. Engines before this ran at 180 degrees cooling system. after unleaded gasoline was introduced this went to 195 degrees. these " lean Burn" engines has a lot higher exhaust temperatures because air was added to the exhaust after it entered the exhaust pipe to further " burn" the remaining hydrocarbons. finally there was a catalytic converter added to further burn the spent mix.
what I think the current thinking is to cool the valve seat area to permit detonation when upping the compression ration with the crap gasoline we have to run these days. Nascar and trick engine builders do this now to get more HP. They drill passages into the cylinder head at the valve seat area to carry coolant to this area. I can see your question on exhaust tube cooling related to an air cooled motorcycle engine since it has no coolant.

11. Dec 4, 2009

### Mech_Engineer

Exhaust gas temperature is related to engine emissions because it is related to the air/fuel ratio in the engine. A cooler EGT generally menas the engine is running richer, and there is more water in the exhaust (water is a major byproduct of the combustion of gasoline and diesel). Cooling the exhaust gases off after the combustion has taken place is useless. To change the exhaust gas composition after the combustion, you have to add another chemical process (like what a catalytic converter does).

12. Dec 11, 2009

### daveg360

Doesn't temperature have a direct impact on the formation of NOx?

13. Dec 11, 2009

### brewnog

NOx formation occurs under high peak cylinder temperatures. Exhaust temperatures are a poor indication of this.

14. Dec 13, 2009

### boostedHULK

i believe a properly set up cooling system would absolutely work. the colder exhaust should create a low pressure if the system worked as well as we'd like. low pressure would help a great deal in a naturally aspirated engine use a lot of valve overlap. i really doubt you'd lose scavenging or velocity. The velocity is really only gonna be limited by restrictions in the exhaust. If the exhaust is cool, i believe the velocity is still gonna remain at whatever the engine needs. now the lower pressure may cause a need for less velocity, so the velocity may drop, but not necessarily in a way that is gonna hinder performance. i say, someone test is.

15. Dec 13, 2009

### boostedHULK

NOx occurs above a very specific in cylinder combustion situation, during Lean conditions specifically. i believe the temperature that it takes to create NOx is 1800* or something like that. it's pretty high.

16. Dec 13, 2009

### brewnog

NO formation will occur under rich conditions too providing there's sufficient free oxygen and high enough peak cylinder temperatures.

17. Dec 14, 2009

### Ranger Mike

Exhaust Insulating Wrap

The original Exhaust Insulating Wrap was developed over 12 years ago by Thermo-Tec. Exhaust Insulating Wrap is an innovative way to create more horsepower and reduce under-hood temperatures.

Wrapping headers maintains hotter exhaust gases that exit the system faster through decreased density. Increased exhaust scavenging is produced, along with lower intake temperatures. Exhaust Insulating Wrap withstands continuous heat up to 2000°F, and contains no asbestos.

Thermo-Tec exhaust wrap will not over-insulate a system when properly installed due to a proprietary coating developed by Thermo-Tec - Thermal Conduction Technology (TCT) - that conducts heat across the wrap's surface. This coating controls heat build-up and dissipation.

these guys been doing it for years. Dynometer results varify the benefit of going stainless steel or wrapping the headers.

18. Dec 14, 2009

### dr dodge

it seems to me that if the exhaust port area were cooled to much, the resulting condensing gas could cause a reversion someplace in the exhaust system. and the wasted heat being removed needs to be recycled" some way to increase the efficiency of the engine. The header wraps are good products. Under hood temps would decrease drasticly if the better part of the OEM exhaust were covered in this stuff. cooled water condensation in the exhaust systen could also pose problems in the "northlands" I have seen cat converters frozen solid in north dakota after the car sat overnite. (we used to drill a single 1/8 in hole to get them to drain)

dr

19. Dec 17, 2009

### boostedHULK

companies have been building, advertising, and selling the crap out of short ram intakes and cold-air intakes too, but they don't add power. i've seen it, on the dyno with my own eyes. doesn't matter if it's a big block chev. or a 1.3liter suzuki swift...it doesn't add power. without the engine being capable of flowing more air through the entire engine, you don't get anything. The companies that design the engines in the first place, generally put a lot of effort, time and money into designing the engine to work at peak efficiency. A small number of engines use the intake as an intended restriction, and you could pick up a ton of power on an engine like that. But what if the company used the exhaust as the restriction?

20. Dec 18, 2009

### Ranger Mike

i disagree with you. cold air intakes do add HP and performance. but,,you will never see this in a dyno room. time after time our lap times were dramatically improved on chilly autumn evenings when the air was dense...why do you think they had carb chokes in the old days? had to richen the air / fuel mix. cold air more dense and more fule must be added to get back to the correct fuel/air mix. since you can not change the jets in a carb ..easily, the air volume is reduced via the choke mechanism...ram air is exactly that..you need to be moving for it to work...and motown engineers took advantage of this in 1963 with the Ramcharger Dodges and Plymouths , Ford Thunderbolts, 440 six pack big scoop hood, 454 chevy scoops. Pontiac GTO scoops,Ford cobra jet air scoop and many more..if it did NOT help HP why would they spend the 

Last edited: Dec 18, 2009