Approaches for modelling of industrial energy systems: correlation of heat transfer characteristics between magnetohydrodynamics hybrid nanofluids and performance analysis of industrial length-scale heat exchanger

Numerical analysis is carried out on heat transfer performance of industrial-length double-tube heat exchanger, by using hybrid nanofluid as a coolant with the effect of external magnetic field. The double-tube heat exchanger contains two tubes, namely inner and outer, and has lengths of 1.39 m and 1.03 m, respectively. The hot oil passes into the outer tube, and the coolant (hybrid nanofluid) passes into the inner tube. Two types of hybrid nanofluids are used for this investigation: (a) CNT-Al2O3/water and (b) CNT-Fe3O4/water. Volume fraction and Reynolds number are considered as 0.1% to 0.5% and 800 to 2400, respectively. This study is carried out with mixture model wherein the equations are solved with control volume approach combined with second-order upwind scheme. Results indicate that Nusselt number is found higher for CNT-Fe3O4/water hybrid nanofluid in the presence of magnetic field. On using hybrid nanofluid, higher thermal efficiency and better performance index of heat exchanger are achieved. The effectiveness increased nearly similar to 30% at higher Reynolds number with Ha = 20. About 40% better performance index is achieved at lower Reynolds number for CNT-Fe3O4/water when compared with CNT-Al2O3/water hybrid nanofluid. Increment in thermal efficiency of heat exchanger is improved almost 30% by increasing the Reynolds number. Graphic abstract