Temperature control and transporting fluids within a pipeline

Methods and apparatus for transporting production fluid from a well are described, wherein production fluid can be pumped through a pipeline to generate friction heat to protect the fluid against hydrate formation and wax deposition, in particular embodiments. The fluid is preferably a hydrocarbon and the pipe a subsea pipe. There may be a circulation fluid circulating within an outer pipe whilst the production fluid flows within an inner pipe. Heat loss over a pipe section may be predicted and necessary heat inputs calculated accordingly.