| 摘要 |
A cascaded fluid heating for electrically heating to fluid, such as a gaseous fluid in a flameless torch, to a high temperature includes a pump to pump a relative constant stream of fluid through a pair of heating chambers arranged in series. A first electric heating element formed of a nickel-iron alloy having a substantially linear positive temperature coefficient of resistance up to 1100 DEG F. is disposed in the first chamber and heats the fluid stream to a first temperature. A second heating chamber receives the heated fluid from the first chamber and contains a second electric heating element of a material, such as Kanthal A, which does not oxide at temperature up to 2000 DEG F. for heating the fluid to a higher temperature. The first electric heating element acts as a sensor for a temperature controller for the first heating element whereby the current supplied by the controller to the first heating element responsive to the changes in resistance of thereof. Interface circuitry connected to the power supply circuit of the first heating element is provided for supplying electric current to the second heating element in direct response with the amount of electric current delivered to the first heating element by the temperature controller. The second heating element is thus connected to "track" the first heating element and is not subjected to high current densities should the fluid flow be reduced drastically or stopped.
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