Low voltage, low temperature heating element - help needed

[daled7]

Looking for help in acquiring or building:

a low temperature (~ 72-74 degrees F), thermostatically controlled rod-shaped heating element, which I can use to heat a roughly 2 ft. silver tube, slid over the heating element. I need it to be slightly less than 3/4 in. diameter, and roughly 12 - 18 inches in length. I'm hoping to be able to power such a device with a lithium ion 6 or 12 V battery.

If someone is manufacturing such a device, I'd be happy to purchase it...if I need to build it, then:

I'm assuming it could be an insulated wire wrapped around an insulated rod (?ceramic), and then encased in copper (graphene?) for better heat transfer.

Suggestions for a thermostatic switch? Length and/or type of wire?

Could I use a battery designed to run power tools?

Any help is much appreciated...

 

[MikeMl]

What is the inside diameter of the 2' silver tube? (to the nearest 1/1000 inch or equivalent metric measurement).

Can the silver tube be used as the electrical ground path for a heating element?

Where would you put the thermostat? end, middle?

What is cooling (heat loss) the outside of the tube? A liquid, still air, moving air? Ambient temperature?

How rapidly does the tube have to heat?

 

[daled7]

Hi Mike,
the silver tube needs to be removed from the heating element periodically. The wall of the tube is roughly 1-2mm thick. The internal diameter is roughly 0.75 inches. Heating is to correct for ambient air, when room temperatures are less than 72-74 deg.F. most commonly, when needed, the room temperature would be greater than 60 deg.F.
The tube cannot be used as an electrical ground. I imagine the best place for the thermostat would be at the insertion end of the element. The entire unit is designed to stand upright, so heat rising through the tube could escape through a series of holes drilled in the tube. This creates the option for a tiny fan blowing heated air up through the tube...

 

[MikeMl]

Does the power source and electronics have to be contained inside the tube? i.e., can there be a cable coming out one end of the tube? Or does the tube protrude from a larger base (box)?

 

[alec_t]

The entire unit is designed to stand upright, so heat rising through the tube could escape through a series of holes drilled in the tube.

In that situation the tube is likely to be hotter at the top than at the bottom. To even out the heat distribution IMO you would need a non-linear heat source. My suggestion would be a series of a dozen or so 1-3 Watt rated wire-wound resistors (they have individual insulation) of graduated values such that the lowest one produced the greatest heat. Judicious placement of a temperature sensor would be necessary.
How long does the heater have to run for on one battery charge?