Sumit Kr. Singh and Jahar Sarkar*
Both mono and hybrid nanofluids, the engineered colloidal mixture made of base fluid and nanoparticles, have shown many interesting properties and becoming a high potential next generation heat transfer fluid in various heat exchangers for engineering applications. The present review focuses on improving the performance of tubular heat exchangers by using nanofluids. For this, the present review briefly summarizes the preparation, characterization and thermophysical properties (thermal conductivity, viscosity, specific heat capacity and density) of mono and hybrid nanofluids. Researches on heat transfer and pressure drop characteristics of nanofluids in the double tube and shell-tube heat exchangers with both straight and coiled tubes, and various engineering applications (power generation, refrigeration and air-conditioning, renewable energy, domestic cooling or heating, etc.) are well-grouped and discussed. Physical mechanisms for the heat transfer enhancement using nanofluids are explored as well. Most of the studies reveal that there are significant enhancements of heat transfer and effectiveness for both straight and coiled tube heat exchangers with a slight increase in pressure drop using nanofluids. Hence, there is an excellent opportunity to use nanofluids in tubular heat exchangers; however, high cost (high payback period) and stability are the main challenges for practical implementation. Finally, some useful recommendations are provided.
Nanofluids, double-tube heat exchanger, shell-tube heat exchanger, thermal performance, pressure drop, energy application
Department of Mechanical Engineering, Indian Institute of Technology (B.H.U.), Varanasi, UP 221005, Department of Mechanical Engineering, Indian Institute of Technology (B.H.U.), Varanasi, UP 221005