Re: Insulation inside the sub

[Dick Morrisson <rmorrisson@unidial.com>]

Thanks Jon,
These are the sorts of things which can only be put in perspective by experience.
I'll have plenty more questions as design details for my dream sub take shape.
Dick

Jonathan Shawl wrote:

> Good solutions for a problem that is not really a big problem in my sub anyway. I
> find that the bare hull does a good job of condensing the excess humidity within
> a few minutes after diving. The viewports hardly ever fog up unless you breath
> right on them directly. The viewports are thick, 1.25 inches, and plastic is a
> pretty good insulator compared to the steel hull. This fact is why the moisture
> condenses on the hull first and not on the viewports. Even if you have the
> thinnest allowed 1/2 inch thick viewport or dome, I would think the steel will
> still cool off faster on the inside. even if you do have a fog problem a drop of
> dive mask anti fog will go a long way.
> I work on refrigeration and AC and there is one thing that is all ways true. They
> suck power big time!
> I have a cooler with a solid state cooling chip in it. As far as I know for the
> amount of heat removed per watt of power, they are not too efficient, but they
> are simple and do work well. If you live in the south, a built in AC that runs on
> surface power just before the dive would be a good idea I think. Right now I'm
> retrofitting a small window AC by adding a water cooled condenser for my brothers
> sail boat in Fla. I know I could fit one into a sub but you do need a lot of
> power. Now if you are diving in cool water in a insulated sub and you want to
> remove the excess heat and humidity there are ways to do that too. You can pump
> the outside cold water through a internal cooling coil that has a fan blowing the
> air through it. I cool my house this way with 45 deg water from the near by
> stream. Or if you don't want to pump the cold sea water through a coil you can
> use a sealed device called a heat pipe. It uses Freon and gravity to transfer
> heat from the inside fan coil to the water outside. It don't use any power other
> than the fan inside and you are probably running it already. It's not the same as
> an AC unit pumping heat up hill, so no it won't work to cool your house in the
> summer. But it could be used to keep your refrigerator cold for free in the
> winter by taking the heat from the refrigerator to the cooler outside.
> Jonathan Shawl
>
> Dick Morrisson wrote:
>
> > Insulation will help reduce condensation on the inside surfaces of the hull,
> > but the dome and/or view ports will still have condensation unless the air
> > inside is dried to the dew point of the water temperature they are exposed
> > to.  Is there a standard dehumidifier available and in general use for small
> > subs?  Can the air being circulated past the CO2 absorbers be run past a hull
> > surface at a slightly higher pressure to allow it to condense and dry it out
> > before scrubbing it?  Does the effectiveness of the scrubber vary with
> > relative humidity?  Perhaps even a small refrigeration unit could cool the
> > air being circulated to dry it then add the heat back in to bring it up to
> > normal temperature before scrubbing.  These units are very efficient and
> > reliable, some are even single chip electronic types.  Thoughts from the
> > group?
> > Dick Morrisson