A numerical simulation has been performed for the fluid flow and heat transfer in a flow passage consisting of a series of 180° bends connected by straight sections. The basic passage cross-section geometry is that of a flat rectangular duct. The simulation problem encompassed three-dimensional flows of both fluid and heat and involved the conjugate interaction of thermal phenomena in the fluid and in its bounding wall. The implementation of the numerical model was performed using FLUENT 5.0. Several results of practical interest were deduced from the simulation. With regard to the motivating application, the heating of biofluids prior to their introduction into the human body, local hotspots were found to occur whose presence could be injurious to living cells. The heating of the flowing fluid (a liquid to properly model the biofluid application) was found to be highly nonuniform at low values of the volumetric flowrate of the fluid despite the fact that the bounding walls of the flow passage were uniformly heated. Local-averaged heat transfer coefficients were evaluated at numerous locations along the length of the flow passage. Except for the regions of the bends of the passage, the local-averaged heat transfer coefficient was nearly constant and closely coincided with the fully developed heat transfer coefficient for flow in a flat rectangular duct.