Date:         Mon, 5 Feb 2007 11:34:30 -0800
Reply-To:     neil <musomuso@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         neil <musomuso@GMAIL.COM>
Subject:      Re: Air cooled heater idea/questions
Comments: To: Keith Hughes <keithahughes@qwest.net>
In-Reply-To:  <45C76CBC.1000104@qwest.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi Keith.

Yah late last night I had a vision of what a cross section of inside
of heater box looks like.

I was ignorantly under the impression that it was a straight tube in
there, which copper could be wound (although not easily) fairly close
to.

There's are fins in there right?

As you point out, that would kinda make it all pointless.




On 2/5/07, Keith Hughes <keithahughes@qwest.net> wrote:
> Hi Neil,
>
> Couple of problems with the idea.  First, you're starting with heat
> exchangers that are designed for heating air, and will not be very
> effective at heat transfer to a fluid filled tube.  Insulation of the
> heater boxes will not address the primary issue, which is heat
> *transfer*, and heat transfer *rate*.  Yes, if you had "perfect"
> insulation, all the heat in the box would end up raising the temp of the
> fluid tubes, but without proper surface contact, you are severly
> rate-limited in heat transfer rate.  You'd also have to bond the tubing
> to the surface (keeping in mind that by design, the *entire* surface of
> the heater 'box' is part of the metal->air transfer medium, thus using
> less surface area reduces effectiveness) of the heater box with some
> sort of thermal conductive material, minimize the cross-sectional area
> of the tubing (why radiator tubes are not round), and optimize the fluid
> flow rate.  Basically, you're creating a second heat exchange process
> that must, by definition, decrease the overall system effectiveness.
>
> Put a fan on the heater boxes, like VW did in the late '70s, to maximize
> the heating capability of the stock exchangers.
>
> Keith Hughes
> '86 Westy Tiico (Marvin)
>
> >Date:    Sun, 4 Feb 2007 18:22:36 -0800
> >From:    neil <musomuso@GMAIL.COM>
> >Subject: Air cooled heater idea/questions
> >
> >Hi all.
> >
> >BION (believe it or not) I have an actual Vanagon question.
> >
> >On a 2L AC engine. An idea that's been on my mind.
> >
> >How crazy is this:
> >
> >Open up heater boxes,
> >
> >wind 3/8" or 1/2" soft copper pipe around each exhaust pipe,
> >
> >assemble/install boxes, (plug hot air outlets)
> >
> >connect copper coils to create a circuit
> >
> >install pump, heater core, etc.,
> >
> >run coolant through to provide interior heat?
> >
> >Other parts would include an expansion tank, fan etc. Likely the
> >biggest cost would be the pump.
> >
> >Hard to answer, but would there be enough heated coolant present in
> >system to provide any appreciable amount of heat?
> >
> >Purely hypothetical, though i do have 2 spare heater boxes.......
> >
> >Likely someone has tried this before, but I am curious.
> >
> >
> >
> >Pax,
> >
> >
> >
> >
> >
>


--
Neil Nicholson. 1981 Air Cooled Westfalia.

http://web.mac.com/tubaneil