The current research may well be carried out to dissect the efficacy of exothermic reaction on the thermal behavior of suspension of Nano-Encapsulated Phase Change Materials (NEPCMs) particles in a complex adiabatic enclosure which entails two differently heated circular cylinders. These cylinders have the potential to move horizontally and to rotate clockwise. The equations governed for thermal-natural convective flow considering exothermic reaction may be solved utilizing FEM. Results described the impact of Stefan and Rayleigh numbers (Ste, Ra), aspect ratio (AR), and non-dimensional fusion temperature (θf) on the thermo-hydrodynamic features of the suspension. The overall heat transmission was found to be reinforced by escalating Ra up to 144.74 % and be lessened by growing AR up to 49 %. Also, there is an optimum value of the latent heat of the PCM cores for a maximum heat transfer rate at a specific value of fusion temperature. Further, results reveal that making the fusion temperature near to the cylinders' temperatures diminishes the heat transfer.