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Old 01-16-2012, 08:44 AM   #50 (permalink)
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Originally Posted by Piwoslaw View Post
Just dumping the heat into the fuel tank half the problem. You need a way to move that heat back to the engine just before starting, but not too much as your fuel will get too cold.
Plus your heat capacity will vary with the amount of fuel onboard.
Plus diesel shouldn't get too warm, I think 55C (130F) is the limit. That's why turbodiesels have a radiator on the fuel line returning to the tank.

I'll quote the last couple posts I made for clarification:

For the guys with the diesel engines, one could insulate the fuel tank, use a heat pipe setup to add heat to the fuel tank from the coolant system and store the heat there. A heat pipe setup with a clever working fluid displacer could be used to essentially turn off the export of thermal energy from the tank when the engine is turned off. Gasoline wouldn't work since it would vaporize much more than diesel, so this would naturally be a big issue.

I won't say it's the best idea, just an idea! Extra heat in the fuel tank could potentially degrade plastic/rubber fuel tank components and of course the heat increases fuel volume. In tank fuel lift pumps may also be effected too. Thermal storage capacity will eb and flow with fuel quantity. I believe this all could be managed though, and enable thermal storage on board without any additional liquid or thermal storage volume added.

Additionally, I will have to look into the maximum storage temperature of diesel and what consequences occur if it's heated to around 205 Deg F. Most diesels have a radiator on the return line to help cool the fuel before it reaches the tank to help with thermal expansion/pressurization, and to prevent thermal gain in a sytem that isn't designed for it. Fuel to fuel heat pipe based heat exchangers can be used to essentially keep heat in the tank where it belongs while allowing fuel to enter and exit at minimal temperatures. They use this type of technology in buildings for air to air heat exchangers.

2002 VW Jetta TDI 5-speed(completed 01M-5-speed swap at 155K miles) 45 MPG City with the 01M, 5-speed 60+ MPG City. Nokian Entyre Low RR Tires. Experimenting with the "Hybrid" 205 Deg F T-stat:


Last edited by Josh8loop; 01-16-2012 at 08:56 AM..
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