Reversible air conditioning

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Reversible air conditioning

Tom Parker-12
On Sun, 2007-12-23 at 03:06 -0800, Metric Mind wrote:
> BTW, I'm negotiation distributorship with Masterflux to add their
> systems to the line of products I have. Later on their inverter
> will have to be replaced by simpler version but today it can be used as
> is. Preliminary page (unfinished):
>
> http://metricmind.com/ac.htm

Is this unit reversible? Can it be used for both heating and cooling?

Due to the wonders of British engineering, my car has completely
separate heating and cooling units. I'd like to drop the heater as it's
noisy and I can save some weight by integrating it with the air
conditioning.

If Victor's system isn't reversible, will the standard automotive system
work if you reverse the compressor? I'm guessing the compressor might
not like this treatment, and I haven't much clue about the
receiver/dryer and expansion valve.

Am I better just put a ceramic heater in the air conditioning duct?

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Re: Reversible air conditioning

(-Phil-)
You can't reverse the compressor to reverse the system.

You have to add some valving and such to convert an AC into a heat pump.
You will also have to improve the control system, such as the installation
of a outside coil temp sensor, otherwise you will experience evaporator
(outside) coil ice-up on cold days and the system will stop working.

There are some automotive heat-pump systems on some cars, but for DIY, the
expense and complexity compared to a ceramic system is not worth it IMHO.

Another option is to use a fuel-fired heater that provides hot water to the
existing heater core.  This is how my system works.  Only a few gallons per
winter fuel usage.

-Phil
http://evalbum.com/1413

----- Original Message -----
From: "Tom Parker" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Sunday, December 23, 2007 3:47 AM
Subject: [EVDL] Reversible air conditioning


> On Sun, 2007-12-23 at 03:06 -0800, Metric Mind wrote:
>> BTW, I'm negotiation distributorship with Masterflux to add their
>> systems to the line of products I have. Later on their inverter
>> will have to be replaced by simpler version but today it can be used as
>> is. Preliminary page (unfinished):
>>
>> http://metricmind.com/ac.htm
>
> Is this unit reversible? Can it be used for both heating and cooling?
>
> Due to the wonders of British engineering, my car has completely
> separate heating and cooling units. I'd like to drop the heater as it's
> noisy and I can save some weight by integrating it with the air
> conditioning.
>
> If Victor's system isn't reversible, will the standard automotive system
> work if you reverse the compressor? I'm guessing the compressor might
> not like this treatment, and I haven't much clue about the
> receiver/dryer and expansion valve.
>
> Am I better just put a ceramic heater in the air conditioning duct?
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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Re: Reversible air conditioning

Zeke Yewdall
On Dec 23, 2007 10:01 AM, ( Phil ) <[hidden email]> wrote:

> You will also have to improve the control system, such as the installation
> of a outside coil temp sensor, otherwise you will experience evaporator
> (outside) coil ice-up on cold days and the system will stop working.
>

Yup, heat pumps don't really work below about 40F or so, because they
start icing the evaporator coils.  Typical heat pumps for heating
houses switch on an electric heating element at lower temperatures.
Since most of the time that you want heat in a car is when it's below
freezing (to defrost the windows, etc), you'd be using the electric
resistance heating most of the time anyway.

Doesn't the prius have a heat pump system though?

Z

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Re: Reversible air conditioning

Jeff Shanab
In reply to this post by Tom Parker-12
A heating element is almost 100% efficient. One of the few things out
there that is. Why mess with that?

The vapor compression refrigeration cycle is more efficient that peltier
but less than the magnetic(which we have yet to see make it in a car.)

Absorption is more efficient than compression, It never made it into car
A/C, other than RV refrigerators. Ammonia is rather poisonous and the
vapor compression is much faster initially. There is a compression
absorption but it is complicated.

How about this idea. two tubes filled with calcium chloride there is a
valve and a heat exchanger to another vessel. this is charged with ammonia.
when charging, the ammonia is driven off the calcium chloride by the
heaters while a fan blows across the heat exchanger to liquefy the
ammonia into the second vessel.

When you are driving, the valve is opened and the fan is reversed and
the ammonia is allowed to go from pressurized liquid to gas and be
reabsorbed onto the calcium chloride. IT gets VERY cold when this
happens. In fact the valve will have to be modulated to prevent the air
coming out of the duct from being too cold.

Why two sets? well for longer drives in really hot areas, you can start
with two charged tubes and when you are on the second set, the first one
can be recharged off of pack or regen energy.

http://www.solarhaven.org/AmmoniaAbsorptionIcemaker.pdf


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Re: Reversible air conditioning

(-Phil-)
Sorry, but even though an electric heater is pretty efficient (not 100% but
close), it's almost always "cheaper" to move heat from somewhere else than
to make it.

But it's not always about efficiency.  The complexity of an in-car heat pump
is probably out of reach of a DIY operation.

-Phil
----- Original Message -----
From: "Jeff Shanab" <[hidden email]>
To: <[hidden email]>
Sent: Sunday, December 23, 2007 12:46 PM
Subject: Re: [EVDL] Reversible air conditioning


>A heating element is almost 100% efficient. One of the few things out
> there that is. Why mess with that?
>
> The vapor compression refrigeration cycle is more efficient that peltier
> but less than the magnetic(which we have yet to see make it in a car.)
>
> Absorption is more efficient than compression, It never made it into car
> A/C, other than RV refrigerators. Ammonia is rather poisonous and the
> vapor compression is much faster initially. There is a compression
> absorption but it is complicated.
>
> How about this idea. two tubes filled with calcium chloride there is a
> valve and a heat exchanger to another vessel. this is charged with
> ammonia.
> when charging, the ammonia is driven off the calcium chloride by the
> heaters while a fan blows across the heat exchanger to liquefy the
> ammonia into the second vessel.
>
> When you are driving, the valve is opened and the fan is reversed and
> the ammonia is allowed to go from pressurized liquid to gas and be
> reabsorbed onto the calcium chloride. IT gets VERY cold when this
> happens. In fact the valve will have to be modulated to prevent the air
> coming out of the duct from being too cold.
>
> Why two sets? well for longer drives in really hot areas, you can start
> with two charged tubes and when you are on the second set, the first one
> can be recharged off of pack or regen energy.
>
> http://www.solarhaven.org/AmmoniaAbsorptionIcemaker.pdf
>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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Re: Reversible air conditioning

Dan Frederiksen-2
couldn't a refrigerator be used. a matter of selecting which end you
want fanned into the cabin and which out to the environment.
or why not use a car AC and supply whatever function is missing. seems
like the simplest way to get it right

Dan

( Phil ) wrote:
> But it's not always about efficiency.  The complexity of an in-car heat pump
> is probably out of reach of a DIY operation.
>  

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Re: Reversible air conditioning

Victor Tikhonov
In reply to this post by Jeff Shanab
Driving stock compressor (plumbed into already built A/C system in any
car) with external motor is simplest way to go. At minimum you need only
one DC motor running off the traction pack to do it. Not so slick
solution is pulley from the tail shaft of now idling traction motor,
this already been discussed on EVDL many times.

A heater, liquid or ceramic, IMO should be separate (and is indeed very
simple) sub-system.

Other advantage of separation - if one subsystem fails, the other
keep functioning. A heat pump is more suitable solution for OEM
ground up EV. Doable, but requires too specialized skills and machining.

Just an opinion.

Victor

Jeff Shanab wrote:

> A heating element is almost 100% efficient. One of the few things out
> there that is. Why mess with that?
>
> The vapor compression refrigeration cycle is more efficient that peltier
> but less than the magnetic(which we have yet to see make it in a car.)
>
> Absorption is more efficient than compression, It never made it into car
> A/C, other than RV refrigerators. Ammonia is rather poisonous and the
> vapor compression is much faster initially. There is a compression
> absorption but it is complicated.
...

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Re: Reversible air conditioning

Victor Tikhonov
In reply to this post by Tom Parker-12
Tom Parker wrote:
...
>> http://metricmind.com/ac.htm
>
> Is this unit reversible? Can it be used for both heating and cooling?

I'm not expert in this, but I don't believe this is reversible
without extensive re-engineering while thing.
>
> Due to the wonders of British engineering, my car has completely
> separate heating and cooling units. I'd like to drop the heater as it's
> noisy and I can save some weight by integrating it with the air
> conditioning.

Nothing wrong with separate systems - combined complexity of both
(and cost) is mo more than single heat pump serving both functions).

I can't imagine heating element being noisy :-)
(blower fans are out of discussion, you've got to have them regardless
of heating principle, they are part of the vehicle design and
too noisy fans have nothing to do with actual heat source.

> If Victor's system isn't reversible, will the standard automotive system
> work if you reverse the compressor? I'm guessing the compressor might
> not like this treatment, and I haven't much clue about the
> receiver/dryer and expansion valve.
>
> Am I better just put a ceramic heater in the air conditioning duct?

I don't believe there is a "duct" as in home where you can place
heating element, but you can sure scatter small ones just behind
each air exit grill in the cabin. Use spiral out of heat guns or
hair driers. It's a solution from the series of "fish tank pump
instead of a pump meant for the job", but technically it will work.

--
Victor
'91 ACRX - something different

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Re: Reversible air conditioning

carrott
On Sun, 2007-12-23 at 14:04 -0800, Metric Mind wrote:
> > Due to the wonders of British engineering, my car has completely
> > separate heating and cooling units. I'd like to drop the heater as it's
> > noisy and I can save some weight by integrating it with the air
> > conditioning.
>
> Nothing wrong with separate systems - combined complexity of both
> (and cost) is mo more than single heat pump serving both functions).

In my car the heater and air conditioning have separate controls, vents,
motors and ducts. The air conditioning has a nice quiet variable speed
fan, the heater has a single speed fan that sounds like a vacuum
cleaner.

> > Am I better just put a ceramic heater in the air conditioning duct?
>
> I don't believe there is a "duct" as in home where you can place
> heating element, but you can sure scatter small ones just behind
> each air exit grill in the cabin. Use spiral out of heat guns or
> hair driers. It's a solution from the series of "fish tank pump
> instead of a pump meant for the job", but technically it will work.

There is quite a big duct between the air conditioner evaporator and the
vent in the dashboard. I haven't yet taken the dash apart but I believe
I can insert a ceramic heater in this duct. I may have to fabricate a
metal duct to replace the plastic one in the interests of fire safety.

If I can't address the fire risk sufficiently, then I can certainly put
an air to water heat exchanger in the duct and use one of your heaters.
I think I would might come out ahead on weight as this would eliminate
the original heater enclosure, fan, controls and ducts.

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Re: Reversible air conditioning

Tom Parker-12
In reply to this post by Dan Frederiksen-2
On Sun, 2007-12-23 at 22:21 +0100, Dan Frederiksen wrote:
> couldn't a refrigerator be used. a matter of selecting which end you
> want fanned into the cabin and which out to the environment.
> or why not use a car AC and supply whatever function is missing. seems
> like the simplest way to get it right

Conceptually that is the simplist, "create a system of ducts, fans and
boxes to house the evaporator and condensor, with a door to select which
recirculates cabin air and which has outside air pass through it".

However when you want to pack it into a very small car and you want
something close to the original sized condenser you are asking for the
impossible. If you made everything quite small and you were clever, you
could probably make it all fit, but I would expect the cooling mode to
be seriously compromised by the small condenser.

If you had all the parts to make a reversible heat pump it would likely
be far superior.

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Re: Reversible air conditioning

Rick Beebe
In reply to this post by Jeff Shanab
> Driving stock compressor (plumbed into already built A/C system in any
> car) with external motor is simplest way to go. At minimum you need only
> one DC motor running off the traction pack to do it. Not so slick
> solution is pulley from the tail shaft of now idling traction motor,
> this already been discussed on EVDL many times.

Doesn't necessarily have to idle. On my Mariner hybrid the AC is powered
by the ICE and shuts off when the engine is off. At a long light the air
coming out gradually gets warmer but as soon as I start moving again and
the ICE kicks in the air gets cold again. There's a max setting which
keeps the ICE running but I rarely find it necessary.

I agree, though, that a separate DC motor is the better way to go.
Especially if you live somewhere hot where you really would want the AC
on all the time.

--Rick

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Re: Reversible air conditioning

martinwinlow
In reply to this post by Tom Parker-12
Tom,

I may have misunderstood but I got the impression that the Aptera has a
heating/cooling system that does what you want - it was referred to in the
Pop Mechanics' recent video as a 'heat pump' and 'reversible' (the relevant
bit of the clip is at 5m40sec). This might be an area you would want to
investigate further.

Regards, Martin Winlow

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of Tom Parker
Sent: 23 December 2007 11:48
To: Electric Vehicle Discussion List
Subject: [EVDL] Reversible air conditioning

On Sun, 2007-12-23 at 03:06 -0800, Metric Mind wrote:
> BTW, I'm negotiation distributorship with Masterflux to add their
> systems to the line of products I have. Later on their inverter will
> have to be replaced by simpler version but today it can be used as is.
> Preliminary page (unfinished):
>
> http://metricmind.com/ac.htm

Is this unit reversible? Can it be used for both heating and cooling?

Due to the wonders of British engineering, my car has completely separate
heating and cooling units. I'd like to drop the heater as it's noisy and I
can save some weight by integrating it with the air conditioning.

If Victor's system isn't reversible, will the standard automotive system
work if you reverse the compressor? I'm guessing the compressor might not
like this treatment, and I haven't much clue about the receiver/dryer and
expansion valve.

Am I better just put a ceramic heater in the air conditioning duct?

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Re: Reversible air conditioning

Geopilot
In reply to this post by Tom Parker-12
The aptera uses a heat pump for air conditioning.
>
> If you had all the parts to make a reversible heat pump it would likely
> be far superior.
>


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