I'm trying to find out the correct way to determine the heat flux at tube inner surface, where the resistance heating wire is wrapped around the outer surface of the tube. The resistance wire is heated up via a DC power supply. A refrigerant is flowing inside the tube and to be evaporated via heat input.
I'd be happy to hear your remarks or if you could redirect me to a document where I can find info on that.
I wish you a nice day
If you assume it is perfectly insulated, the inner heat flux should be the heating rate of the resistance heaters times the square of the ratio of the diameter of the resistance heaters to the diameter of the inner tube. If it is not perfectly insulated, subtract the amount of heat lost to the outside of the system from the first factor in this expression.
If the heat transfer is steady and there is no heat loss to ambient then the average heat flux is equal to Q/Ain, where Q is the heating rate of the heaters and Ain is the inner surface of the tube. The rate of heat transfer through a pipe is constant, but heat flux increases with decreasing radius.
You may possibly want to check also: https://www.researchgate.net/post/When_some_electrical_power_is_driven_through_a_wire_which_is_wrapped_around_a_metal_tube_how_to_know_the_temp_rise_of_the_tube_theoretically
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