Hi,everybody

Can anybody give me some guidance about the analysis of jacket pipe?During my analysis,I do not know how to define the temperature of the core pipe and jacket pipe.The temperature of mediums in core pipe and jacket pipe is different,and there must exist heat transmission between these two pipes.But we don't know how many the temperature changed.
Of course,maybe we only regard the medium temperature as the pipe metal temperature,and it is not necessary to consider the heat transmission,right?
Any guidance and advice are greatly appreciated!