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ICE radiator waste heat recovery system?

  1. Jul 29, 2011 #1
    Hello all... I am new to posting, but have followed posts on here for a while and finally got myself stumped, so I'm looking for advice and thoughts before I go over my project budget only to find I over/under estimated something.
    I am currently building a biomass fueled electrical generator and am trying to squeeze every last drop of efficiency I can out of it. Currently I have a small turbocharger feeding a pressurized gasifier which goes through an ejector picking up a specific ratio of air and force feeding a V-6 engine which drives a generator (20kw is my limit for residential grid connection, with the capacity to upgrade to 100kw). A huge portion of my fuel obviously goes right out the radiator and I expect my largest gains in overall efficiency will come from recovering some of this waste heat.
    I have looked at many waste heat recovery systems for process equipment and most seem to only be effective with >500*F temperatures. A radiator will never achieve these temperatures. Because the small turbocharger only has to supply half of the air that the engine is consuming (which becomes producer gas fuel, and picks up the required air downstream at ~1:1 ratio) as opposed to traditional forced induction where it supplies 100% of the air consumed, I have a lot of available energy in my exhaust stream to power a second parallel turbocharger.
    My thought, in order to avoid freon, etc. is to power a second turbocharger to suck air through a shroud and piping across the radiator, recovering the low quality heat, compress it as much as possible to increase the temperature and force it through a fire tube style boiler or other heat exchanger in order to power a steam (or gas) turbine and extract what would otherwise be wasted energy.
    Any thoughts or comments from related experience or design would be greatly appreciated. There are quite a few calculations in determining the energy output and I am afraid that if I am 5-10% off here or there and the results compound I will end up with high expectations for a concept that doesn't perform, or estimate that it is not worth it, and miss out on a 20% gain in overall efficiency. Thanks in advance!
  2. jcsd
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