In the
present study, effect of different geometries of inner and outer tube surfaces on heat transfer of a double
pipe heat exchanger is studied. Water CuO nanofluid, that is assumed to be a single phase, flows in the outer tube.
Two equation standard κ ε turbulence model is used to model the turbulent flow. Simulations are done for different
cases include convex, concave and smooth surfaces for inner and outer tubes at different Reynolds numbers. Results
show that the maximum heat transfer corresponds to the convex concave case in comparison with the smooth smooth
one. Heat transfer rate increases with the Reynolds number, but the slope of the increase for nanofluid is lesser than
that for the pure fluid. It is demonstrated that the friction factor decreas es with the Reynolds number, so the pressure
drop decreases as the Reynolds number increases. Also, the simulations are done for two other nanofluids, water ZnO
oxide and water SiSiO2 dioxide with a volume fraction of 3%. It is found that water CuO nanofluid flow leads to more
heat transfer rate in a double pipe heat exchanger in comparison with the other nanofluids