This research focuses on evaluating the thermal performance of a combined sensible and latent heat storage unit using a packed bed design integrated with a constant heat source. The Thermal Energy Storage (TES) system features a cylindrical, insulated storage tank filled with spherical capsules containing phase change materials (PCMs) - specifically, paraffin wax and stearic acid. PCMs offer significant benefits in thermal management by enabling isothermal operation and higher thermal storage capacity, contributing to a reduction in system size and cost. To enhance the thermal conductivity of the heat transfer fluid (HTF), nanoparticles are introduced into water, creating nanofluids that improve the efficiency of heat transfer. These water-based nanofluids facilitate heat transfer between the constant heat source and the storage tank, serving as a sensible heat storage medium. The study examines different HTF configurations, starting with water alone and extending to nanofluids with Al₂O₃ and MgO nanoparticles at three volume concentrations (0.2%, 0.5%, and 0.8%). Experiments were conducted at varied flow rates of 2, 4, and 6 liters per minute to analyze the effect of these parameters on heat transfer and PCM melting time. Performance parameters, including charging time, instantaneous stored heat, cumulative stored heat, and system efficiency, were evaluated for each HTF-PCM combination. Additionally, batch-wise discharging experiments were conducted to assess the system's heat recovery capability. The results offer insight into the comparative advantages of different HTF materials and configurations, highlighting the thermal performance enhancements achieved by using nanoparticle-enhanced HTFs.