Self-regulating packed-powder resistive heater

A method for heating comprising the steps of:

• providing concentric inner and outer tubes having different thermal expansion coefficients;
• packing a space between the inner and outer tubes with a conductive powder;
• providing two electrodes in electrical contact with the conductive powder;
• introducing a potential across the electrodes such that the conductive powder functions as a resistive heater whose resistance changes with temperature based on different degrees of thermal expansion of the inner and outer tubes.

A resistive heater comprising:

• an outer tube having an inner surface and a first thermal expansion coefficient;
• an inner tube having an outer surface a second thermal expansion coefficient that is less than the first thermal expansion coefficient, wherein the inner tube is disposed concentrically with the outer tube such that there is a space between the outer surface of the inner tube and the inner surface of the outer tube;
• carbon black powder disposed within the space between the inner and outer tubes and packed sufficiently such that the carbon black powder is conductive;
• and
• two electrodes in electrical contact with the carbon black powder such that when a potential is introduced between the electrodes, the carbon black powder functions as a resistive heater whose resistance changes with temperature based on the different degrees of thermal expansion of the inner and outer tubes.