Hello there, Firstly I would like to welcome myself to the forum, my name is Ben and I'm 21 and I'm from the Isle of Mull off the west coast of Scotland. I am studying mechanical engineering and this question has been giving me a massive headache. If I have 60m3 of water at 60oC in a tank which passes through a copper pipe in a room that is at 20 degrees C, how long would my pipe need to be to bring the water temperature down to 25oC. This question comes from my current internship. We have a rig that we need to cool with water and we are looking at heating the building with the energy and we are considering passing it through a long snaking pipe at the side of the shop floor. Help is much appreciated.