A tube in tube heat exchanger pipe is meshed using ICEM Hexa. This is a basic geometry and so the thickness of pipes has not been included. A more advanced geometry with thickness is tackled in Module 2.
The geometry is uploaded here:
https://drive.google.com/file/d/0Bzp_ezWs3z-GNk04NG5QTEVHT0k/view?usp=sharing
