[PSUBS-MAILIST] Thermoelectric air conditioning

Thu Mar 6 15:30:18 EST 2014

I did some research on the Thermocouples. You can PWM them quite nicely if your PWM frequency is high. The problem is that slow PWM frequencies allow slow temperature changes which tends to degrade the Thermocouple.

Most switchers operate at high frequencies at 50 kHz and higher which eliminates the temperature fluctuations.

Good luck with whatever you do,

Ken Martindale

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Alan
Sent: Thursday, March 06, 2014 2:59 PM
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] Thermoelectric air conditioning

Hi Keith,

someone else suggested PWM but I read that they don't like being

switched on & off frequently. There will need to be a thermostat in the

loop with I imagine long dwell times between on & off once the temperature

gets close to target temperature. Most modules I've seen work well off 12V,

so that will make things easy.

Yes I intend using the lower part of the hull as a heat sink.

Have you recently joined the Psub email blog or have you been out there for

a while. 

Regards Alan

Sent from my iPad

On 7/03/2014, at 7:50 am, keith tollett <k6fee at yahoo.com> wrote:

Alan,

Forgot to mention that those thermoelectric modules can be pulse width modulated to make their current drain much more manageable and still accomplish climate and humidity control. There would be a fan needed on the air side, and the other could be directly attached to the steel hull with thermal grease. That would make a very efficent heat/cold sink, and eliminate another fan. There are comercial pic controlers on Evil-Bay for under $50, or if your handy with a soldering iron, you can make your own.

Keith

On Wednesday, March 5, 2014 8:05 PM, Joe Perkel <josephperkel at yahoo.com> wrote:

Yes, very interesting. I also have a more than passing interest in climate control.

Joe

On Mar 5, 2014, at 10:50 PM, Alan James <alanlindsayjames at yahoo.com> wrote:

Thanks Keith,

that's an encouragement to know that they operate them on a large scale

like that.

Alan

  _____  

From: keith tollett <k6fee at yahoo.com>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: 
Subject: Re: [PSUBS-MAILIST] Thermoelectric air conditioning

Alan,

U.S. Military subs use this for climate control. Don't want any noxious refrigerants loose in a closed environment. No moving parts, though they do eat a lot of power (not an issue on nuke boats).

Keith

On Wednesday, March 5, 2014 6:22 PM, Marc de Piolenc <piolenc at archivale.com> wrote:

There's an active discussion of Peltier devices ongoing on the other 
personal submersibles mailing list 
(international_psubs_minisubs at yahoogroups.com). You might want to join it.

Quick points: you still need some way to dump heat outside the boat, 
otherwise you're just moving heat from one point you want to cool, to 
another that can't afford to get any hotter. And of course the Peltier 
device produces heat of its own.
Which leads to the second key point, namely that there is an optimum 
current for heat pumping, and for some reason the manufacturers 
routinely rate their modules for a voltage that gives a higher current, 
and thus poor heat pumping efficiency. You have to learn certain key 
characteristics of your unit and come up with your own rating. The unit 
I fooled with back in the States was rated at 12 volts, but worked much 
better with an 8-ohm resistor in series.

Marc de Piolenc

On 3/6/2014 9:08 AM, Alan James wrote:
> Hi Psubbers,
> Has anyone looked at thermoelectric coolers (peltier devices) for air
> conditioning / dehumidifying & heating.
> I'm hopeful someone might be able to save me a bit of research.
> http://en.wikipedia.org/wiki/Thermoelectric_cooling
> For those who aren't familiar, they are normally used to cool small
> units like computers, electrical cabinets & chili bins.
> They are about 1&1/2" square & 1/8"  thick with two wires coming off them.
> The unit I have is 60W & operates off 12-15V. When powered up, one side
> gets hot & the other cold.
> The cooling effectiveness is regulated by how well you can dissipate the
> heat from the hot side.
> In the submersible application the hull can act as the heat sink. By
> switching polarity you have a heater.
> The down side is that you use about 3 times more power for cooling than
> traditional refrigeration units,
> however an air conditioning unit is bulky, & it would be a trade off
> between the additional battery size & expense
> to run the peltier cooler as apposed to the bulk & expense of an air
> conditioning unit & it's associated through
> hull heat exchange unit .
> The heating faze is more economical.
> G.L. require air conditioning & humidity control in submersibles.
> Thanks
> Alan
>
>
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