<p>In this study, an experimental study and numerical analysis of tunable heat transfer enhancement in compact heat exchangers have been carried out by using porous inserts containing magnetic spheres and subjected to external magnetic field. The proposed configuration is based on the use of magnetically responsive spheres which are introduced into a reconfigurable porous matrix to provide adaptive control of permeability and effective thermal conductivity, rather than the use of conventional porous inserts with fixed thermal-hydraulic characteristics. The Reynolds number (Re = 300–2500), porosity (0.2–0.6) and magnetic field intensity (B = 0-0.25 T) were systematically investigated for the heat transfer and flow characteristics. A three-dimensional numerical model was developed using Darcy–Brinkman–Lorentz model and an effective conductivity model based on Maxwell–Eucken was set up and validated with experimental measurements. It was found that the use of a magnetic field had a significant effect on the thermal performance of the porous insert. The optimum operating condition yielded up to a 30% rise in the average Nusselt number and a negligible pressure drop penalty, which is acceptable for engineering design. Moreover, favorable thermal-hydraulic performance factors of the proposed system were achieved under a wide range of operating conditions. The numerical predictions agreed well with the experimental measurements, with a mean absolute percentage error of 3.6% for the Nusselt-number validation dataset and a maximum individual deviation below 6%Further, the power requirements for pumping, uncertainty analysis and industrial applicability were also thoroughly examined. The proposed magnetic sphere-assisted porous insert is a promising and tunable thermal management solution in compact heat exchanger, battery cooling systems and advanced industrial thermal applications.</p>