Nichrome heater - Heat transfer through conductors?

[jerbo]

I am working to build a device that includes an air pump and heater. The pump will push air through a tube at the end of which will be a heater element. After doing some research, it seems that Nichrome is the standard heating wire for hobbies. I'm planning to have the heater in a glass-section of the tube.

My concern lies in the nichrome's connection to the circuit -- first, solder I assume is a bad idea since the heater's temperature could be over 400 C, so I will use crimp-terminals. Still, isn't there a problem with heat conducting beyond the heater and through the connecting wires, and how much of a problem is it?

My plan is to use high gauge nichrome, 28AWG or higher, on a 12V circuit. It is likely that the heater will be on for an extended period of time.

Any and all help is appreciated.

 

[vk6kro]

This sounds like some commercial devices. Hair dryers and fan room heaters do this.

Although a lot of heat is generated, the actual temperature isn't usually enough to cause the wire to glow red. This is because the heat is carried away in the air stream.

So, the problem may not be all that bad.
If you have wire with suitable high temperature insulation, the wire will get hot but not hot enough to cause a problem, provided there is a reasonable distance between the heater and anything likely to be damaged by heat.

You can probably still get ceramic terminal blocks, so you could use these instead of cheap plastic ones. These are electrical insulators, but reasonable conductors of heat so they might bypass some of the heat to whatever metal surface they are mounted on.

 

[sophiecentaur]

It is easy to obtain a short length of high temperature connecting lead to put between the element and the actual supply lead. It exists either with silicone sleeving or, for higher temperatures, a kind of woven insulation (you find it in fan ovens, for connecting the elements, for instance).
A 400 degree thermal fuse might also be a good idea. These are also available from places like Maplin and could save your house from going up in flames!