I am sizing an electric heating element to produce a steady supply of heat. The heating element consists of a ceramic tube, coiled on the outside with resistance wire. This tube is encapsulated by another larger ceramic tube and the space between them is evacuated to help direct the heat to the air column in the tube wound with resistance wire. A fan then blows this heated air to where it is needed. What I know is: 1) The diameter of the resistance wire. 2) The wall thickness and inside diameter of the ceramic tube coiled with resistance wire. 3) The resistivity of the wire in Ohms/ft. 4) The voltage and current running through the resistance wire. What I don't know is: 1) How many feet of wire to wind around the ceramic tube to reach a desired temperature that remains constant. 2) Which CFM fan rating should be used to blow past the element to deliver the air at constant temperature. I need somebody to help me figure out what I don't know from the information I do know. Am I missing anything? Any and all help is appreciated.