Most inert type of plastic?

[ReeferMac]

Hi Randy,

Quick question for you, I'm working on an idea for a type of heat-exchanger, and I want to use some inexpensive plastic tubing.... but there's about a million different kinds.

Which plastics are the most inert and suitable for use in SW? Are some better suited than others? The one supplier I looked at has Nylon, polyetheylene, tyhon, silicon, polyurathane, PVC, teflon, kynar, styrene, polyporopylene, and some medical grade crap that you're probably used to seeing! :confused:

Cheap is obviously a good thing, pliable is pretty important...
Thanks.

- Mac

[Randy Holmes-Farley]

Heat exchanger at what temperature?

Certainly polyethylene, propylene and polytetrafluoroethylene are totally nonreactive with water and seawater systems. Others are probably OK too, but some may slowly degrade.

I cool my tank system by passing tap water through a big coil of small diameter plastic tubing in my sump, then out to my yard. It is either polyethylene or polypropylene from Home Depot.

[ReeferMac]

Hmmm... he's onto me! :D I don't want to disclose too much.. (where is that tounge-in-cheek emoticon?)
Close, but cheaper, and closed circuit. Think about the sump in your in-laws basement.... ;) You prolly have one in your's too... for once, something good about being in the NorthEast!

Thank you much Randy! (as he trundles off to USPlastics) :)

- Mac

[ReeferMac]

OK Dumb question on the list number two... (I swear, and then I'll order).

5 bucks price difference, so you know I'm really being cheap here.. (actually, I just want to get the right one first..)

Polypropylene tubing, and Polyethylene tubing... Flexibility difference between the two? Where would a layman see something like this? It's all Ice-machine tubing to me, isn't it? What's the big difference in the chemicals used in it's manufacture then? Any thermal differences you can think of between the two types of tubing?
Thanks again!

- Mac

[Randy Holmes-Farley]

Polypropylene stands up to elevated temps better. The flexibility depends on thickness and diameter. I'd suggest looking at some at Home Depot to see what you like.

[Habib]

Originally posted by ReeferMac
Hmmm... he's onto me! :D I don't want to disclose too much.. (where is that tounge-in-cheek emoticon?)
Close, but cheaper, and closed circuit. Think about the sump in your in-laws basement.... ;) You prolly have one in your's too... for once, something good about being in the NorthEast!

Thank you much Randy! (as he trundles off to USPlastics) :)

- Mac

What some people also do is have the cooling coil in the cellar or they dig a hole in the ground about say 3 or 4 feet deep and put the cooling coil in there.

It helps. :)

[ReeferMac]

Damn habib! You got me!
Poor-man's chiller! I've got a 'floating slab' foundation, and there's this big cement crock that's constantly refilling w/60-degree water....
I found out the expensive way that 1" ID PVC is too thick for good heat exchange - stuff insulates way too well. Anyone need some 1" PVC? I'll have 50 feet of it in the near future... :rolleyes:
Thanks for the info Randy for a few bucks, I think I'll go w/ the better prouct....It's all 1/16th thick at the half inch size I'm looking at.

- Mac

[Randy Holmes-Farley]

FWIW, small diameter tubing has a lot more surface area to volume ratio than does half inch. So the exchange can be better for smaller tubing.

[ReeferMac]

Ahh... good to know! Thanks again.

- Mac

[Randy Holmes-Farley]

You're welcome.

Good luck! :)