Sorry, I didn't mention that the pipe is vertical. It is a short-length pipe (2.5 ft) and the needed increase in temperature is high: the inside pipe wall temperature normally is at ambient temperature (25ºC = 77ºF) and it must be kept at 105ºC (221ºF).
We have 4.4 bar (155 ºC) steam available...
Does anyone know how to design a spiraled steam tracing for a pipe (number of spirals, spacing between spirals, tracing diameter)?
I can't find any good reference on the subject...