Propane EFI - part duece

[Greg Hermann]

>espen hilde wrote:
>>
>> Great thinking Greg!
>> im  thinking of how long it will take to heat the propane up after start.
>> Espen
>>
>> Greg Hermann [SMTP:bearbvd at cmn.net] skrev 3. juli 2000 03:18:
>> > >In the current spirit of KISS, I want to keep this butt simple.
>> > >
>> > >Propane in a tank boils at -43f - but will remain liquid as the pressure
>> > >builds up.  Therefore, liquid propane's pressure varies wildly as to
>>temp -
>> > >requiring a liquid pump, cooler and return system.
>> > >
>> > It is entirely possible to do liquid propane butt simple!
>> >
>> > Use a tank with a liquid feed line--which is what all automotive propane
>> > fuel tanks have anyway, and use engine coolant to (indirectly) warm the
>> > propane TANK to a controlled temperature (which will also be a controlled
>> > pressure).Then run the liquid line through a liquid to ambient air cooler.
>> > THEN (after the cooler) regulate the pressure of the liquid line to
>> > whatever level you want. Be a good idea to include (fixed orifice, very
>> > small will do) return bleeds at any high points in the plumbing to return
>> > any vapor bubbles to the top of the tank.
>
>	Er, has anybody seen what happens to a tank of propane when it is
>heated to around (I believe) 100 deg. Celsius? The idea of actually
>_heating_
>the stuff doesn't appeal to me, or indeed to any firefighter I know!
>OK, you
>could control the temperature to lower than that, but even the
>extremes of
>ambient start to get a bit hair-raising, especially in an enclosed
>space under a
>hot vehicle. I suspect some kind of cryogenic cooling might instead be
>in order.
>Does the word 'expensive' now come to mind? Also, I think the
>pressure/
>temperature curve is extremely non-linear (almost exponential), which
>will
>make it very difficult to control.
>
>	(I believe 100 deg C is what is called the 'critical temperature' for
>propane, above which it will _not_ remain liquid under any
>circumstances, and
>fairly suddenly begins to obey the ideal gas laws, resulting in a
>_huge_ rise
>in pressure - enough to rupture the tank if it's not _very_ well
>protected

You are right that there is a "critical" pressure, and about right about
where it is for propane--BUT-- at the critical pressure, it simply turns to
gas. NO huge pressure rise once it is there. Not even any change in volume.

Nor is there any latent heat of vaporization at the critical point.

The thing that breaks tanks is the thermal expansion of the liquid in tanks
that are filled too full of liquid.

Greg (worked with design of propane and ammonia refrigeration systems)


>with release valves. I may have the details wrong here, but I have
>seen film
>of the resulting fireball, which can fry everyone for several hundred
>metres
>around!)
>
>	Just my little contribution!
>
>	Best regards,
>		Franc.
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