simple lpg aircon.
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  1. #1
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    Default simple lpg aircon.

    When I first had my DS converted to lpg the installer had the coolant lines doubling back from rhetoric heater unit to the vaporizer, this meant that with the heater off coolant would take the path of least resistance and bypass the vaporizer. .. which would turn it to a solid block of ice...
    what I realised driving long hrs up to Qld was that I had cool air comming through my vents as the vaporizer was right next to the fresh air duct. got me thinking.
    if copper pipe was used to T off from the Lpg and coiled in the fresh air vent would it create the same effect? does it need to be plumbed back into the lpg circuit and should the T be before or after the vaporizer?

    clearly tampering with lpg systems is dangerous and voids insurance etc. but would it work?

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    Harley

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    1000+ Posts robmac's Avatar
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    Quote Originally Posted by Pastinha View Post
    When I first had my DS converted to lpg the installer had the coolant lines doubling back from rhetoric heater unit to the vaporizer, this meant that with the heater off coolant would take the path of least resistance and bypass the vaporizer. .. which would turn it to a solid block of ice...
    what I realised driving long hrs up to Qld was that I had cool air comming through my vents as the vaporizer was right next to the fresh air duct. got me thinking.
    if copper pipe was used to T off from the Lpg and coiled in the fresh air vent would it create the same effect? does it need to be plumbed back into the lpg circuit and should the T be before or after the vaporizer?

    clearly tampering with lpg systems is dangerous and voids insurance etc. but would it work?

    Harley
    LPG is a very good refrigerant. After all the basic principal of refrigeration is to harness the heat absorbing effect of phase change (ie change from liquid to gas states).

    In aircon systems the phase change from liquid to gas is accurately controlled by either a orifice tube or TX (thermal expansion valve). The "gas" is used for a single purpose - air con.

    On the other hand in LPG systems the "cooling" is byproduct of turning the LPG from liquid to gas. It must be a gas to be combustible. To try and control the phase change to recover the "cooling" would not be easy and the change takes place in the converter, not a convenient place to harness the cooling.

    So , from a practical point of view it's possibly not feasible.

    Having said that some Daikin Air Conditioning use a process called heat (cool is the absence of heat) recovery. The basic principle is that if a system is on cool the outside coil get hot and the inside coil get cold. if a system is on heat the opposite is true of the coils (heat pump/reverse cycle).

    Daikin VRV recovery systems recover the "cool energy" from systems running on heat pump and direct into systems running on cooling, thus using waste energy to improve efficiency .

    This is similar in concept to your proposal
    Last edited by robmac; 8th January 2013 at 02:41 PM.

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    Quote Originally Posted by Pastinha View Post
    When I first had my DS converted to lpg the installer had the coolant lines doubling back from rhetoric heater unit to the vaporizer, this meant that with the heater off coolant would take the path of least resistance and bypass the vaporizer. .. which would turn it to a solid block of ice...
    what I realised driving long hrs up to Qld was that I had cool air comming through my vents as the vaporizer was right next to the fresh air duct. got me thinking.
    if copper pipe was used to T off from the Lpg and coiled in the fresh air vent would it create the same effect? does it need to be plumbed back into the lpg circuit and should the T be before or after the vaporizer?
    clearly tampering with lpg systems is dangerous and voids insurance etc. but would it work?
    Harley
    Hi
    LPG is as effective as other refrigerants. However the heat absorbing is needed immediately after the pressure reduction to enable the change of state from liquid to gas. That takes place in the vaporiser and so it freezes up if the heat is not supplied. However if the gas was removed immediately to an alternative heat source it could work. Would require a bit of trial and error. Not a good idea probably

    Perhaps another method would be to have a sub system on the water side. A small pump to circulate the coolant through the vapouriser then through the interior heater core and back to the vapouriser. Two heater valves to cut off the circuit on both hoses to the engine circuit. The heat for vapourisation would then come from the air passing over the interior heater core which would then cool the air coming in the normal ventilation system. If the system cools too low then you could crack the heater valve a bit for some heat. I might even patent this

    Some cars have a small pump in the coolant to circulate it for a while, when the engine stops to prevent heat build up. R19 autos and VW transporter T4 autos spring to mind. Be cheap at the wreckers.
    jaahn

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    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by jaahn View Post
    Some cars have a small pump in the coolant to circulate it for a while, when the engine stops to prevent heat build up. R19 autos and VW transporter T4 autos spring to mind. Be cheap at the wreckers.
    jaahn
    add r19 manuals to that list too. Mine has that pump.

    Jo

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    Quote Originally Posted by jaahn View Post
    Hi
    Perhaps another method would be to have a sub system on the water side. A small pump to circulate the coolant through the vapouriser then through the interior heater core and back to the vapouriser. Two heater valves to cut off the circuit on both hoses to the engine circuit. The heat for vapourisation would then come from the air passing over the interior heater core which would then cool the air coming in the normal ventilation system. If the system cools too low then you could crack the heater valve a bit for some heat. I might even patent this
    jaahn
    Hi Jaahn, that would assume that the vaporizer would cool the glycol close to freezing, which given the heat from the engine i doubt. the simple way to test would be to rig the outlet from the vaporizer to the heater core > engine to see if it would work. am I understanding the idea correctly?
    I my mind it would only make real world differences if the heater core would start to have ice crystals appearing on the outside...
    So I would need a separate 'vaporizer' without a heat source to create a freezing gas which would run through a coil of copper inside the air duct, but then I would need to return that gas back into the system... before the idle valve on the vaporizer otherwise my air/fuel ration could be all over the place...

    Harley

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    Quote Originally Posted by Pastinha View Post
    Hi Jaahn, that would assume that the vaporizer would cool the glycol close to freezing, which given the heat from the engine i doubt. the simple way to test would be to rig the outlet from the vaporizer to the heater core > engine to see if it would work. am I understanding the idea correctly?
    I my mind it would only make real world differences if the heater core would start to have ice crystals appearing on the outside...
    So I would need a separate 'vaporizer' without a heat source to create a freezing gas which would run through a coil of copper inside the air duct, but then I would need to return that gas back into the system... before the idle valve on the vaporizer otherwise my air/fuel ration could be all over the place...

    Harley
    I did a fair bit of research into a similar setup. I was intending on using the lpg vaporiser to cool a non engine water supply for a water to air intercooler system.
    There are a few things to consider. The boiling point of LPG (at atmospheric pressure) is -80c iirc so as long as the water flowing through the converter is kept above water freezing point, it should still easily vaporise the LPG.

    If you were going to make a system work as an a/c system, I would run a small radiator pre vaporiser to get the water back to ambient. I would run a 5 liter tank to add balast to the system and i would insulate the converter and the outlet (cool) hose from engine heat. You could run a glycol solution to lower the freezing point as an added safety margin.

    The electric booster pump made by Davies Craig should do the job as its designed with a high duty cycle and high flow

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    Quote Originally Posted by Pastinha View Post
    Hi Jaahn, that would assume that the vaporizer would cool the glycol close to freezing, which given the heat from the engine i doubt.

    It does not have to be close to freezing but that would be nice. "The gycol" was just your normal coolant which should have gycol in it. Insulate the vapouriser from the engine heat, as mistareno said.

    the simple way to test would be to rig the outlet from the vaporizer to the heater core > engine to see if it would work. am I understanding the idea correctly?

    I am not sure if we are on the same idea ! I was using the coolant only to transfer the cool not the gas direct. That's a bit risky. The coolant sub system is isolated from the engine by two heater taps, one on each hose.
    I guess if I was doing it I would measure the temperature drop of the coolant through the vapouriser in real time driving with a couple of thermocouples and a meter to get a measure of the cooling available. Then measure the heat drop over the heater core to give a set temperature rise of say 20 deg for the air coming in, at a similar driving condition. See how the two reading compare. If the two are somewhat close then its worth looking into, if the readings are worlds apart then!!
    ;
    I my mind it would only make real world differences if the heater core would start to have ice crystals appearing on the outside...

    An aircon does not run that cold or it freezes up and stops working. You would be happy with that problem and could apply some of mistarenos ideas to solve it.

    So I would need a separate 'vaporizer' without a heat source to create a freezing gas which would run through a coil of copper inside the air duct, but then I would need to return that gas back into the system... before the idle valve on the vaporizer otherwise my air/fuel ration could be all over the place...

    That is a different system, like you initially talked about. Would work, yes. The gas would need to go back into the system before the idle AND the main system. How well it works would be determined by measuring the heat available just the same as I have said above or some similar method.
    Of course you could get a refrigeration technician to calculate some figures to see if there is any correlation between the heat /cooling loads. Sorry I have forgotton all that now. Basic calcs though. The cooling is provided by a ?Kg of LPG per hr.

    Harley
    Jaahn

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    Quite a few years ago, I did some work with the NZ defence department. The head of procurement had just bought an import Mazda 6, top of the line thing with everthing that opens and closed. Import regs in NZ required the refrigerant to be drained prior to import (I think they were still using CFC in Japan). While I was there, he found out that his A/C system had been re-charged with LPG. Worked great, but i wouldn't want to be involved in a frontal collision with a highly flamable pressurised fluid in the heat exchanger tucked behind the front bumper...
    racing 405
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    Quote Originally Posted by racing405 View Post
    Quite a few years ago, I did some work with the NZ defence department. The head of procurement had just bought an import Mazda 6, top of the line thing with everthing that opens and closed. Import regs in NZ required the refrigerant to be drained prior to import (I think they were still using CFC in Japan). While I was there, he found out that his A/C system had been re-charged with LPG. Worked great, but i wouldn't want to be involved in a frontal collision with a highly flamable pressurised fluid in the heat exchanger tucked behind the front bumper...
    What fuel are you using in your car? Diesel? BTW, how much LPG was in that A/C? 300g or so?
    "The enemy of knowledge is not ignorance, it's the illusion of knowledge"
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    Quote Originally Posted by JoBo View Post
    What fuel are you using in your car? Diesel? BTW, how much LPG was in that A/C? 300g or so?
    And... both R13A and R12 are flammable to degree. They both produce toxic byproducts.

    Hychill is propane butane mix essentially LPG. Have you ever been poisoned by fumes from the barby or blown up cooking on the barby?
    And there is normally up to 9KG available, so the 300gm of Hychil / LPG is not likely to be too dangerous.

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