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NG pressure regulation to support Air Conditioning

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  • NG pressure regulation to support Air Conditioning

    Hello,

    Has anyone thought about utilizing the cooling effect of pressure regulation to assist the AC device? The passenger air heat exchanger could have some sort of inner circle with a control valve which would use either the hot coolant from engine temperature in winter times and in summer times it would circulate through the CNG pressure regulator. The pressure regulator of course should have it's own temperature controlling system, which would heat it above the "freezing range" with the engine coolant, if the passenger air heater does not heat it enough. Of course the separate AC device could be always used when driving with benzine, or if the cooling effect is not enough with CNG.

    This kind of "poor mans AC" could be enough for areas of mild summer temperatures (such as Finland), eliminating the need of traditional AC device. Although AC is not a big issue as a fuel consuming auxiliary device, some fuel (and power reserve) would be still saved when not using the AC compressor, nor carrying the extra load of the AC equipment. And there would be no costly AC fill-ups either no more.

  • #2
    Re: NG pressure regulation to support Air Conditioning

    Hi Hewey,

    A good friend and I kicked this around for 10 minutes about a dozen years ago. It would probably work better with LPG than with CNG because of the greater amount of laten heat of vaporiztion, from the change of state, that LP has and CNG doesn't have.

    We decided to pass because of the safety question. If a vehicle equipped with this type of "air conditioning" gets into an accident and the system is damaged there would be an extreamly high probability of fire because of the release of LP or NG and the many possible source of ignition.

    I still like the idea because of the reduction in parasitics on the engine.


    Larrycng

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    • #3
      Re: NG pressure regulation to support Air Conditioning

      Hi Larry,

      I guess very few ideas are actually totally new, but the more discussion, the more perspectives and possibilities to find solutions that someone actually benefits from. And whether or not new solutions are found, the discussion helps understanding the operation of the existing systems, helping everyone interested to maintain their equipment.

      You must be right that LPG offers more cooling due to the phase change. Maybe the CNG pressure drop is not such effective that it really could replace much of AC's job. However I'm still curious to find out, what kind of cooling effect would there be, maybe it would still aid AC just a littel, so AC would not have to kick in so often.

      I have to think a little more of the system setup and draw a rough plan for the piping. I see no risk in it, because you are anyway circulating the coolant in the pressure regulator, through a sealed heating chamber. So pretty much nothing changes in the CNG system, the coolant would just not come solely from the engine in summertimes, it would partially also come from the passenger air heat exchanger. It may (and propably will) be that the cooling effect is way too small to cover up the expenses and the complexity/malfunction risk increase of the system. Let alone to completely replace the AC.

      But anyway, thanks for the constructive feedback!

      EDIT: typos
      Last edited by Hewey; 02-20-2009, 02:57 AM.

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      • #4
        Re: NG pressure regulation to support Air Conditioning

        Here's a setup that possibly might work : ) I try to explain the intended operation of the new parts.

        Both valves should be operated with similar openings by the temperature controller (which would be a little different than a normal thermostat), which makes sure that the PRD recieves coolant at least at say 70 °F temperature, to ensure de-icing. The PRD hopefully cools the coolant down and the heater core then cools the incoming air down. (Pretty absurd to switch the heater adjuster to hot during a hot day, but now the heater core exhanges the heat into the opposite direction...)

        The "double pump mystery device" is just two pumps connected into each other with an axle. This way the engine water pump is used to circulate also the "PRD inner circle", when the valves separate the system into two different areas. The valves should not be able to shut absolutely totally, in order to maintain constant pressure through out the whole system.

        If the PRD does not operate properly near the 70 °F temperature range, the whole idea is useless : (
        Attached Files

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        • #5
          Re: NG pressure regulation to support Air Conditioning

          Hello,

          After considering the complicity of the setup versus the benefits of it, I think it's not worth trying in reality.

          But however I'm still wondering how to utilize the cooling effect of the pressure regulation. How about coupling the PRD with engine air intake with a water-air heat exchanger? In summertimes the air would be hot enough to keep the PRD out of ice, and any cooling effect would yield in denser air going to the engine -> more power. With turbocharged engines, the water-air heat exchanger would naturally be located after the air-air intercooler.

          The increase in horsepowers would not be much, but at least the cooling effect would be utilized into something beneficial. And this kind of setup would be easier to build too.

          I read from somewhere about a decent solution of boosting engine power with cooling intake air. It used the AC to cool down a liquid "battery", which had enough heat capacity to really cool down intake air for about 30 seconds.

          The PRD cooling effect is not easily suitable for such a system, because PRD temperature must not go below the dew point. Maybe an electric peltier-element between the cooling "battery" and PRD would suit though. But it would be kind of hassle to control the whole thing...

          My quest for more power out of CNG is somehow going further, this time with a conventional approach. A Simons sportsystem free flow exhaust system waits in the trunk for installation. Running the engine with CNG has a nice low roaring sound compared to gasoline already with the stock exhaust, and I'm pretty sure the sound will be even nicer with just an absorption muffler in the back.

          Regards, Hewey

          EDIT: typos
          Last edited by Hewey; 03-10-2009, 04:31 AM.

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          • #6
            Re: NG pressure regulation to support Air Conditioning

            You have some good ideas, however the PRD (Pressre relief device) is not really practical.

            The PRD is a safety device used in case of high temperatures in the area of the cylinder that would cause excessive pressure in the cylinder. When the temperature of the CNG tank gets over about 217 to around 235 deg F. (which would push the pressure in a full tank to around 5,000 psi) the PRD will vent the cylinder to the atmosphere. In that case the vehicle is probably on fire.

            Larrycng

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            • #7
              Re: NG pressure regulation to support Air Conditioning

              I think the amount of heat actually pulled from the coolant in the regulator is just not really enough to be of practical use anywhere. Well, I suppose you could set up a lop that could be used to keep an ice-chest in the boot cool... seriously though, the cooling effect is minimal, especially when just cruising. The reason it really NEEDS the warming is for under much higher demand moments, such as acceleration.. unfortunately, these are times when your AC is already switched off, and by the time the cooling would have any effect on the intake temperature, you're already cruising again, and the effect is wasted... personally, i don't want to add any unreliability to the fuel system unless there is significant energy returns.
              1997 Factory Crown Victoria w/ extended tanks ~~ Clunkerized!
              2000 Bi-Fuel Expedition --> ~~ Sold ~~ <--

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              • #8
                Re: NG pressure regulation to support Air Conditioning

                One aspect that I did not think of with the "heating system of CNG in the pressure regulator" is that it is there not only for the situations (WOT) in which ice could be formed, but it is particularly there to always maintain a constant temperature in the CNG. If the CNG temperature should vary a lot, the air/fuel ratio would vary too, because the gas density depends on the temperature.

                Such a cheapo AC would compromise the proper operation of the engine control system, and likely still not do much of what it was ment to do.

                Thanks though for the conversation, now I understand the system a little better again.

                Regards, Hewey

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