so I've got this vapouriser, which has to be heated to stop it freezing, and
it's in a parallel water circuit with the car's heater, connected to the
source of heat, viz. the engine. If I put a valve in to interrupt one of
the pipes from the engine, I should be able to get the cold to go into the
heater element in the heater, there to exchange it with warmth from the
atmosphere, making the air coming into the car cooler while at the same time
supplying heat to the vapouriser. I guess it'll probably want a circulating
pump to get the water to flow around the smaller circuit of heater element
and vapouriser.

The valve, of course, will be remotely operated, and can then be used to
adjust the temperature. Provided the vapouriser is maintained above
freezing point, I don't see it needs to be as hot as it normally runs.

so much for the theory.

Has anyone done it? does the vapouriser make enough coldness to be worth
the effort?

I tried putting a valve on the outlet from the engine this evening, but I
suspect it's faulty and doesn't shut properly, it's a very old one, and the
vapouriser still got hot, implying that water was still circulating.

The system of using a single valve to shut off the heater used to allow of
unheated air, on vehicles so fitted, so it ought to work to isolate the
vapouriser/heater combo, and also allow of regulating the heat in the cabin
and the vapouriser, by allowing more or less hot water around from the
engine.

any thoughts?
--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
In Touch: Get in touch with yourself by touching yourself.
If somebody is watching, stop touching yourself.
from the Little Book of Complete B***ocks by Alistair Beaton.

Austin Shackles wrote in
:


so I've got this vapouriser, which has to be heated to stop it
freezing, and it's in a parallel water circuit with the car's heater,
connected to the source of heat, viz. the engine. If I put a valve in
to interrupt one of the pipes from the engine, I should be able to get
the cold to go into the heater element in the heater, there to
.....

Hi Austin,
I have pondered this also but as my Land Rover is still being rebuilt I
have not been able to try it. It is possible that if you get the plumbing
right the water may circulate by convection and not need pumping.

The other problem you will have will be condensation in the heater matrix.
Good luck and let us know if it works.

Terry

On or around Wed, 16 Jul 2003 10:52:42 +0000 (UTC), Terry Lyne
enlightened us thusly:

Austin Shackles wrote in
:


so I've got this vapouriser, which has to be heated to stop it
freezing, and it's in a parallel water circuit with the car's heater,
connected to the source of heat, viz. the engine. If I put a valve in
to interrupt one of the pipes from the engine, I should be able to get
the cold to go into the heater element in the heater, there to
....

Hi Austin,
I have pondered this also but as my Land Rover is still being rebuilt I
have not been able to try it. It is possible that if you get the plumbing
right the water may circulate by convection and not need pumping.

The other problem you will have will be condensation in the heater matrix.
Good luck and let us know if it works.

new S3 heater water valve on order, as the one I put on isn't stopping the
hot flow. I reckon one of those little drill-powered pumps would do
circulation, attached to a suitable motor, if it needs it. In theory it'll
work by convection, but that might not keep the stuff circulating enough to
stop the vap. freezing.

vapouriser with no water circulation freezes PDQ, especially with the engine
under load, IME, so I reckon there's a fair bit of cold there.

It'd be possible to build a conventional AC system using propane as the
working fluid, and pumping it back into the fuel tank, I expect, but this
system has the benefit of being much easier to implement, if it works. Not
that bothered if it only produces a relatively limited cooling effect,
either - anything would be better than nothing, style of fing, bloody heater
won't go off in mine - the airmixing thing doesn't shut off the hot air
completely (foam seals gone west, I spect), so you can't even blow ambient
temperature air into the footwells.

--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"There is plenty of time to win this game, and to thrash the Spaniards
too" Sir Francis Drake (1540? - 1596) Attr. saying when the Armarda was
sighted, 20th July 1588

On or around 16 Jul 2003 23:21:51 -0700, (Dave Griffs)
enlightened us thusly:

I,ve done a bit of browsing, and come up with these figures, don't
know if they're correct.

Propane latent heat at boiling point 773 btu/gallon.
Say you use about 4 gallons per hour (50 miles at 12.5 mpg)
773*4 = 3092 btu/hour - any inefficencies
I beleive a typical car air conditioner to be at least 5000 btu's/hr,
so it just might provide enough to make a noticable difference if my
figures are correct.

well, I've got the water valve now. I still reckon it's going to need a
pump to circulate water through the vapouriser and heater matrix.

will experiment this weekend.

--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
Too Busy: Your mind is like a motorway. Sometimes it can be jammed by
too much traffic. Avoid the jams by never using your mind on a
Bank Holiday weekend.
from the Little Book of Complete B***ocks by Alistair Beaton.

On or around Thu, 17 Jul 2003 18:44:26 +0100, Peter Hill
enlightened us thusly:

AC requires a lot more heat to be put in to the vapour. If you return
more warm vapour than makeup volume due to draw off there is no chance
of vaporisation taking place in the tank, so no tank cooling.
Re-condensation is dependant on extraction of heat from or increase in
pressure in the tank. The pressure rise will stop when the blow off
valve vents gas. Otherwise you need a compressor and a condensor to
return liquid.

I'm going to try using the cold in the vapouriser first. I had in mind
using a compressor anyway, if I was gonna borrow propane from the fuel tank
to run a conventional AC system.

I like the idea of using all that cold which is otherwise wasted when
running the engine. Whether it's enough, I dunno, a recent posting seems to
indicate that it might be. I'm not, after all, trying to refrigerate the
inside of the motor, only cool it down a few degrees.

--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"For millions of years, mankind lived just like the animals. Then
something happened which unleashed the power of our imagination -
we learned to talk." Pink Floyd (1994)

On Thu, 17 Jul 2003 19:49:33 +0100, Austin Shackles
wrote:


I'm going to try using the cold in the vapouriser first. I had in mind
using a compressor anyway, if I was gonna borrow propane from the fuel tank
to run a conventional AC system.

When there was a discussion about the possibility of using an ac
compressor pump to transfer propane from bottles to tanks it was
pointed out that there was a lubricant in the ac pump which was
somehow recycled in the pump. Without this the pump soon fails,
allegedly.

AJH

On Thu, 17 Jul 2003 22:29:44 +0100, Stewart
wrote:

From a point at sea, to the circles of your mind, this is Austin
Shackles:


I like the idea of using all that cold which is otherwise wasted when
running the engine.

Actually, you are (normally) using the heat which is otherwise wasted.
In this respect I suppose you are adding to nett efficiency.

If your plan will end up drawing the same amount of heat out of the
air, into which all waste heat from the engine is lost anyway, then
the overall system efficiency will not be affected. But if the
vapourised gas being drawn into the engine ends up being colder than
usual, then I guess you are going to be running your engine less
efficiently.

I would also guess that the quantities will be small, but just thought
I'd add some extra factors for you to calculate on the back of that
envelope.

It's a double edge sword.
The higher the inlet temp, the higher the peak temp the greater the
possible theoretical efficiency. Higher temps lead to engine damage
and melt down, good job the water has some additional cooling. But
the lower the inlet temp the denser the charge the greater the
volumetric efficiency. This is usually the winner, it's why even
injection LPG loses efficiency and uses more BTU/mile or KJ/Km
compared to petrol. Petrol vaporises in the inlet giving a slightly
better VE.

The best place to vaporise LPG is in the ENGINE! But so many people
only see LPG as a means to save money on slow gas guzzling
agricultural vehicles. They are quite happy with (nay their meaness
demands) low cost solutions comparable to the surface carburetor used
in Veteran cars. They don't demand the proper application of the fuel,
making use of it's greater inlet cooling and high octane rating to
allow use of High compression and/or HP turbo's with reduced/no need
for a flow restricting intercooler.

Then Toyota (New Prius) and others (Ford are on the bandwagon for gas
guzzling SUV's stateside) go and throw induction VE away by holding
the inlet valve open to half stroke so they only compress half the
full cylinder volume (at whatever pressure the throttle allows) into
an under sized combustion chamber giving 13.5:1 compression from BDC
to TDC. Appears high but moderate in geometric terms from inlet valve
closed point. As it has a high expansion ratio like a high comprssion
Diesel it gives Diesel like efficiency at part load. The downside is
that flat out they only fill the cyclinders to half volume so a 1500cc
Prius works like a poor 750 - 57bhp (+40bhp electric is 5bhp more than
the normal Paseo 1500's 92bhp). The Atkinson or Miller cycle. Now
all we need is someone to feed them LPG for low diesel fuel consumpion
rates on half price fuel!
http://www.pressroom.com.au/pressroo...s/priuskit.htm
If they where really green minded it would be LPG only to start with.

--
Peter Hill
Spamtrap reply domain as per NNTP-Posting-Host in header
Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!

On or around Thu, 17 Jul 2003 22:29:44 +0100, Stewart
enlightened us thusly:

From a point at sea, to the circles of your mind, this is Austin
Shackles:


I like the idea of using all that cold which is otherwise wasted when
running the engine.

Actually, you are (normally) using the heat which is otherwise wasted.
In this respect I suppose you are adding to nett efficiency.

In a way. You use the (mostly unwanted) heat from the engine to get rid of
the unwanted cold in the vapouriser. What I plan to do is to use unwanted
heat in the air entering the cabin to do the same trick.

If your plan will end up drawing the same amount of heat out of the
air, into which all waste heat from the engine is lost anyway, then
the overall system efficiency will not be affected. But if the
vapourised gas being drawn into the engine ends up being colder than
usual, then I guess you are going to be running your engine less
efficiently.

cooling the incoming air in the engine actually adds efficiency, hence
intercoolers on diesels. But what I'm trying to do is to cool the air
coming into the cabin. Mind, I suppose the gas going into the engine will
be cooler as well, as you say, but that should help engine running, not
hinder it - ever noticed how things run better on cold frosty mornings?

I would also guess that the quantities will be small, but just thought
I'd add some extra factors for you to calculate on the back of that
envelope.

I'm more of a "suck it and see" type engineer :-)


--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"Nessun maggior dolore che ricordarsi del tempo felice nella miseria"
- Dante Alighieri (1265 - 1321) from Divina Commedia 'Inferno'

On or around Thu, 17 Jul 2003 21:58:49 +0100, Peter Hill
enlightened us thusly:

Use an electric pump like Volvo use to stop turbo heat soaking after
engine has been switched off. Downside is poor operation at town
speeds and in traffic queues when fuel demand is low. You may do
about 10mpg in town but you only average 15mph so you use 1.5g/h - not
enough to do much more than cool a few cans in a mini fridge. Older
air-con without devices to increase engine idle speed and fans on the
condenser can be defeated in these conditions on hot days. Efficiency
will not be very good either as the vapour/water and the water/air
heat exchangers will be less efficient than a direct vapour/air one.

hmmm. any idea which volvo? would be a good source of a second-hand (i.e.
cheap) pump.

I realise the cooling effect of the whole thing won't be as impressive as a
full-blown aircon thing that takes about 5hp from the engine to run it's
compressor. But it will, hopefully, not detract at all from the fuel
efficiency. In fact, cooling the inlet gas may possibly improve the
efficiency as you suggest - certainly, the vapouriser at the moment runs
quite hot - near enough engine temperature, so I assume the gas emerging
from it is pretty warm too.

--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"The great masses of the people ... will more easily fall victims to
a great lie than to a small one" Adolf Hitler (1889 - 1945)
from Mein Kampf, Ch 10

"Austin Shackles" wrote in message
...
On or around Thu, 17 Jul 2003 21:58:49 +0100, Peter Hill
enlightened us thusly:

hmmm. any idea which volvo? would be a good source of a second-hand
(i.e.
cheap) pump.

Yes, any of the 400 series turbo's, and on some of the carb equiped ones
too, to lessen fuel vapourization. Renault used one on the 21 turbo also.

Tim..


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