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Automotive Automotive application for absorption cycle?

  1. Jun 15, 2011 #1
    Hi there, I joined specifically to ask for help in exploring the possibility of harvesting the waste heat from a cars engine and recycling this energy to improve the engines efficiency.
    I'm assuming most people know about thermo dynamics, internal combustion and volumetric efficiency I:tongue2: ...my own grasp of these things is weak so I'm hoping people can help me with this little "wine into water" idea I haveo:)

    A bit of background - I'm nearing the completion of a custom car build I first began 5 years ago. Part of the rebuild has been the conversion of the engine to forced induction with a turbocharger.
    The system includes a barrel type air to water/glycol chargecooler to take the heat out of the intake charge, a circulation pump and a heat exchanger where the coolant dumps the heat.

    Now, when I came to plan the turbos exhaust down pipe I had to solve a major problem - heat... these things get really, really hot, 900 C no problem and hotter in my state of tune...

    So I had the idea to cool the downpipe with a waterjacket, its own heat exchanger and circulating pump - pretty much like the charge cooler setup really but for cooling the turbines outlet rather than the compressors.
    As an aside, I speculated that cooling the exhaust immediately after the turbine could even cause a beneficial scavenging effect on flow but hey that another story.

    Thing got interesting when I was telling someone about my plans for heat management and my chargecooling system and they said they were working on something way more exciting using the cars aircon to cool the intake charge.
    I didn't take his plan seriously because if you know that a turbo flows around 300 CFM at 250 C, the cooling effect of an engine driven pump powered aircon system is going to unappreciable and a total waste of time. BUT it got me into the idea of using refrigeration

    So I looked at the different things that can power the various cycles that clever men have invented over the last hundered years or so and saw that the ABSORPTION CYCLE uses waste heat to produce a cooling effect!
    I looked at some diagrams and began to suspect that I already had several of the major components required - most important, a generator to heat the amonia dilute - the jacketed downpipe.
    Where I'm stuggleing is working out exactly how to do this - what other bits I need to buy or make and how to spec the other components. The generators capacity to heat determines the rest I supose but this is where I'm straying way outside my comfort zone but if folk can help me plan it, I'll build it and maybe we'll all learn something? Thanks for reading all anyway:smile:

    edit - I should also say that the absorption cycle could be used in any car to run the aircon without a power robbing compressor - all engines have hot exhausts.

    I also wnted to say that this type of refrigeration is well proven in mobile homes so envoironmental factors should't be an issue.
     
    Last edited: Jun 15, 2011
  2. jcsd
  3. Jun 16, 2011 #2
    I'm starting to understand the chemistry side of this whole thing and I think I know what major components need to be...

    1. The generator. This will be fired by the cars exhaust down-pipe - a design is emerging... its two pipes within a pipe, one of which is the down-pipe, the other runs weak ammonia dilute back to the absorber vessel at the start of the cycle.

    2. The condenser. This will be a liquid to air heat exchanger, most likely an automotive oil cooler where oncoming air will cool the ammonia vapour.

    3. The evaporator. This will be a plate type liquid to liquid heat exchanger where the ammonia removes heat from the charge-cooling water/glycol circuit. suitable items are widely available.

    4. The absorber. Another air/liquid exchanger rad like the condenser but with the addition of solution sprays in the end tanks to recombine the ammonia with the weak dilute and nitrogen.

    5. The absorber vessel. A sump tank basically with3 ins and outs - to the generator, to the absorber and back from the generator.

    6. Pump. to circulate. easily available

    7. Expansion valve to pressurise the generator and release the ammonia vapour to the condenser


    anyone know if I've got that right?
     
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