Hydro-thermal performance evaluation of nanofluids flow in double pipe heat exchanger: Effects of inner pipe cross section, circular or cam-shaped

This study investigates numerically the hydro-thermal behavior of nanofluids in double-pipe heat exchangers with two different cross-sections using four different nanofluids. Two types of different circular and cam-shaped cross-sections, four types of different nanofluid of various concentrations are assessed. The results show that cam-shaped cross-section has reduced the heat transfer rate and the pressure drop compared to the circular cross-section. The heat transfer rate has been increased in both types of heat exchanger by increasing the concentration of nanoparticles, but the pressure drop and friction coefficient has been increased compared to pure water. The results of investigating energy ratio show that the highest performance evaluation criterion (PEC) is related to the silver nanoparticles and the energy ratio (PR) increases by increasing the percentage of nanoparticle concentration. But the energy ratio has been decreased for other nanoparticles by increasing the volume percentage of nanoparticles. The results of thermal and hydraulic studies show that the highest PR value is related to water/TiO2 nanofluid and cam pipes have a higher energy loss. Maximum heat transfer improvement for circular pipes is 26.74% related to Ag nanoparticles while this value is 21.15% for cam-shaped pipes.