Thanks for the responses.
I've attached the working I've done so far, I am not sure if it is correct as the length calculate is quite small.https://files.engineering.com/getfile.aspx?folder=d512005a-beeb-4167-b5af-708eca146c36&file=IMG_20210412_170846.jpg
A pipe has outer diameter 0.142m and has ethanol vapour with mass flow rate 108kg/s entering. The temparature of the ethanol entering the pipe is 123celsius and the temperature of the furnace surrounding the pipe is 450celsius. The pipe is stainless steel 304 and thickness 0.2mm.
How do I work...