Heat transfer augmentation in a tube using nanofluids under constant heat flux boundary condition: A review

•Reviews heat transfer augmentation of nanofluids in a tube with constant heat flux.•Recent advances in hybrid nanofluids are reviewed.•Identifies and compares significant results.•Scope of future research in this area is discussed.

In the last few decades, research on nanofluids has increased rapidly. Traditional heat transfer fluids with order of nanometer sized particles (1–100 nm) suspended in them are termed as nanofluids. Nanofluids have been proved as better heat transfer fluids despite of various contradictions in results by different research groups. The aim of this article is to review and summarize the recent experimental and theoretical studies on convective heat transfer in heat exchangers using constant heat flux boundary condition. The use of different types of nanoparticles with different base fluids by different research groups has been presented and compared. Further an overview of experimental results about heat transfer abilities of hybrid nanofluids from available literature sources is also presented. Finally, the challenges and future directions in which research can be further progress are discussed.