cooling the diesel?

[Benjamin]

maybe its a crazy idea,
what about cooling the diesel before it goes in the pump to make more power
we use IC for cooling the air down, why not cooling the diesel.
Would a oil or little intercooler be effiecient?
or do you think it wont make a difrence because the heat of the engine...

Greetz, Benjamin

[Tusker]

The coefficient of thermal expansion of gases is extremely high compared to that of liquids.  You get worthwhile gains condensing the air, but the liquid fuel would be a waste of time.

[jtanguay]

actually jake has posted somewhere here before on the fact that the newer TDI's have diesel fuel coolers on them.  my guess is that the gains would be a bit better than negligeable, considering the system needed to cool the fuel.  too hot of fuel = less power, too cold... gelling...  I tried to find some information on the optimum temperature for diesel to burn efficiently as possible, but can't find much info on that one.

i think its more of an attempt to lower emissions though... so yea probably a waste of time

[RabbitJockey]

i always thought the system on the tdis was to keep the fuel warm.  but i have heard of people with fuel filters mounted outside of the engine bay running better... but who knows how true all that is

[Slave2School]

My automatic comes with a fuel cooler too, on the return line to the tank.  I'm not sure on anything other than an electronic tdi if there is much benefit because it's aparently the computer pulls timing whenthe fuel get too hot for pollution reasons.  You really notice this when the tank gets low in the summer on a hot day.

[SMOKEYDUB]

remember that the fuel needs to get hot to ignite. maybe a cooler on the return line but i wouldnt go nuts. i probably wouldnt bother.

[QuickTD]

The cooler you make the fuel, the higher it's density and more fuel mass will be injected on each pump stroke, thats the primary reason that cold fuel runs better, everything else being equal. I don't think excessively cold fuel improves power much. I seem to recall some bosch research concluding that 30-40ºC is the about the optimum, lower and atomization suffers, higher and the pump wear increases and power drops.    

 It's easy enough to compensate for hot fuel, just turn the fuel screw in a bit more, but then you have to adjust it back if the fuel cools, or put up with the smoke... What I'd like to see (or build if these damn customers would go away...) is some sort of temperature control system to keep the fuel at a relatively constant 30ºC, summer, winter, stuck in traffic etc. some sort of pelteir heat/cool setup would likely be the best, though probably overkill. A simple thermostatic valve and a cooler would be a simpler solution. The stock thermostatic "T" on the filter could be used with a cooler, but it sucks, plastic crap. Maybe the guts could be transplanted into a decent housing?

[jtanguay]

hey quicktd i got some 350 watt peltier coolers.  I just need a slab of aluminum machined for the fuel to pass through and I can get started

peltier coolers are so precise... these things get REAL cold or REAL hot very quickly.  (and will burn out quickly if they dont have a heat sink on the hot side..)

[Mark(The Miser)UK]

hey quicktd i got some 350 watt peltier coolers.  I just need a slab of aluminum machined for the fuel to pass through and I can get started

peltier coolers are so precise... these things get REAL cold or REAL hot very quickly.  (and will burn out quickly if they dont have a heat sink on the hot side..)

[/size]

What kind of efficiency can these things achieve?

[QuickTD]

What kind of efficiency can these things achieve?

Not very good. The junction itself is a huge thermal short. They make far better heaters than they do coolers. A conventional compressor/condenser/evaporator system is much more efficient except at a very small scale.    

 On the upside they are compact, solid state, have no moving parts and make no noise. They are also very, very reliable.

[jtanguay]

yea their reliability is far greater than any a/c system out there.  I would have to say that their efficiency is directly related to the amount of heat taken from the hot side of the junction.  The more heat left on it, the more resistance, and therefore efficiency drops.  

There was a company that was creating a video card cooled by a junction that was in turn cooled by liquid metal being pumped using a magnetic pulsing system.  Very cool!   The liquid metal could transfer a whole lot of heat from one location to another due in part of its conductivity.  It never came on the market though...

I still want to do some testing on my peltier's and see how different cooling methods work.  Just need access to a lathe and some rather large pieces of aluminum.

[745 turbogreasel]

I have a funny feeling return line coolers are an emission part
A) to make fuel density more consistent
B) to reduce fuel evaporation emissions/smell

And maybe a kludge to get a little more life from crappy electronic pump control modules.

[jtanguay]

i would have to agree about the cooler being an emission control device.  obviously a diesel car/truck will smoke more in the summer, and that is due in part of the air quality, and temperature of the fuel/motor.  Even without a peltier cooling system, achieving 30-40C for the diesel fuel just by using air to cool it alone should be possible.

another thing I have not went over, is that the efficiency of a phase change system is directly related to the compressor, which basically 'traps' the heat from one location to another.  With the peltier junctions, the heat can soak through from side to side, making it much less efficient.  Imagine phase change + peltier? -80C!!!  for those emergency situations when your beer is too warm!!!

this is basically what my peltier junction looks like:
http://cgi.ebay.com/Gigantic-62mm-350-Watt-Thermoelectric-Peltier-Cooler_W0QQitemZ280038754246QQihZ018QQcategoryZ4660QQrdZ1QQcmdZViewItem

i guess temp range is -60 and not -80... oh well, it should still suffice to cool my beer in an emergency  :lol: