Designing the ultimate heated undersuit

[RedSeaDiver2]

- Heating panels on the wrists - I've been experimenting with active heated wrist warmers and I find excellent results with notably warmer hands when I pump 10W of heat into the area just inside my wrists.

OK that is really good information to have - we will try to either incorporate longer heating panels into the forearms so as they also cover the wrists, or else we will try to move the forearm panels lower so as they cover the wrists.

- Somewhat watertight connectors, so that they don't get corroded in the case of a suit flood.

I've set a goal to have everything including the connectors all IP68 standard - but no guarantees on just yet - that is going to be a time will tell thing.

I would also challenge the utility of heating panels on the thighs. That's one area that I find stays fairly warm, since those muscle groups are working during the dive.

I suspect that would depend on the type of diving you are doing - if you are using a scooter, or doing a two hour deco hang then maybe not so much.

 

[RedSeaDiver2]

Being that I have direct experience with coolshirts and built my own system for motorcycle application I'll coment on that side.
The only way you could effectively make that work is if you had a heated storage tank pre dive that could bring the liquid to full temp and injected to system right before dive. There's no battery in the world that you'd be able to carry on a dive that can go ambient to warm and then maintain for and hour in a water system. However if you had prewarmed the water you can use the calorie content as a heat sink and only have to add btu to maintain temp which should be a long lasting heat compared to heating pads with no thermal storage. Biggest problem is you need a pump and heater in the loop. This is the one case where I'd be curious if Peltier coolers could possibly be considered more efficient then strictly resistive depending on water temp your diving in. Convective they are horribly in efficient but full water conduction on both sides with temp throttling could be a use case

I'm happy to leave it to someone else to design a system like this - I think that it would take longer to get to market than I want.

 

[RedSeaDiver2]

SFTech already does this:

Heating Pads - SFTECH

The SF Tech heating system is based on a modular principle that makes it easy to remove or replace heating elements.

www.sftech.ch

I've looked at those on the internet, no doubt they are well built and do the job etc. but I think it is best to go with our own heating pad manufacturer as the SFTech pads are only available in one size/shape - and they look too big to use for forearms, wrists etc. I'm working with a company that specialises in heating pads, and what they have suggested is to have three different models of heating pads - each will have a different shape/length to width ratio - but the surface area will remain the same so as heating is equal across all pads.

 

[RedSeaDiver2]

Not the right standard for this application.
In reality 18ga thhn wire should be way more than adequate for any heating system off a dive battery. The standard ampacity rating is meant for conductors behind a wall that can never once be overheated thru use and compromise the insulation. In this application having the wire get warm but not hot is actually a benefit to an extent. Resistance goes up as it gets hot so self throttles to an extent.

Many thanks. Will run with that diameter.

 

[sinidive]

Personally I would avoid wires getting warm inside a dry suit.

That said 18ga wire *is* suitable for this heating solution (and also works with the table linked).

 

[RedSeaDiver2]

C

Personally I would avoid wires getting warm inside a dry suit.

That said 18ga wire *is* suitable for this heating solution (and also works with the table linked).

Cheers - will run with that.

 

[RedSeaDiver2]

Any specific type of wire to try to get that will hold up to continually being moved and bent in an undersuit?

 

[ChrisMBC]

Any specific type of wire to try to get that will hold up to continually being moved and bent in an undersuit?

Definitely needs to be stranded, I feel that goes without saying. I have been using silicone-insulated wire for my own heating wiring harness, which exhibits good flexibility (better than PVC) over a wide range of temperature.

 

[RedSeaDiver2]

Definitely needs to be stranded, I feel that goes without saying. I have been using silicone-insulated wire for my own heating wiring harness, which exhibits good flexibility (better than PVC) over a wide range of temperature.

Many thanks! I will try to get silicone insulated wire.

 

[broncobowsher]

Since you are in the research phase,,,I just wanted to suggest that "electric" is one possibility. But "water" is another possibility.

Many go-kart & race car drivers use 'Cool-Shirts' that pump tiny bits of temperature controlled water capillaries inside shirts, pants and socks. And astronauts also are using the same devices. This is just an example website, but there are hundreds more.

Motorsports – COOLSHIRT SYSTEMS

coolshirt.com

There are research problems with both Electric and Water systems, but cost advantages with both too.

I've had the same thought. Even have one of the shirts for racing.
An observation that is overlooked. It isn't just the heating (or cooling), it is the distribution. Even out the hot and cold spots.
This was developed by NASA for use in space suits. They have been running it pretty much exactly the same for 50 odd years now. One of the things I remember about it was the users were overall comfortable. No hot or cold spots.
I've also thought of it for cooling. Tend to overheat a bit on the surface and thought it would be nice to have that cool shirt (I have an ultra chiller version) to keep me cooled off while out of the water. Have not done the math, but I bet a small volume of water could be heated and circulated giving better results than heating elements against the skin. Going to say it won't be as efficient, but I bet more comfortable.

It is just dreaming at the moment. But with some solid background to it as well.