A Review of Combined Heat Transfer Enhancement Methods Using Nanofluids and Inner Ribs

Heat transfer enhancement is a process of increasing the heat transfer rate and thermohydraulic performance of a system using various methods. These different methods are grouped mainly under two techniques, passive and active. The technique of application of inner ribs, such as twisted tapes, coiled or tangled wires, and nozzle turbulators, and nanofluids are among the passive heat transfer enhancement method that has been commonly studied in recent years. The methods of heat transfer enhancement are employed for developing the heat transfer without affecting the overall realization of the systems significantly, and it covers a wide range of areas where heat exchangers are used. Using of inner ribs in flow region increase both convective heat transfer and fluid friction because of inducing the turbulence and promoting the swirl flow. Additionally, nanoparticles enhance the thermal properties of base fluids that causes the increment of heat transfer rate without causing major frictional forces in thermal systems. To obtain the thermo-hydraulic performance of a thermal system, both heat transfer and fluid friction characteristics should be investigated. For this reason, the present study represents a comprehensive review that focused on combined heat transfer enhancement methods with nanofluid and inner ribs used in the flow region.