Impact of microwave irradiation on the thermophysical and energy storage properties of MXene-Ag-Syzygium cumini dye nanofluids for solar distillation

Abstract

This investigation delves into the profound influence of microwave electromagnetic radiation on the thermophysical attributes and enthalpic energy storage (ΔH_es) capabilities of novel MXene (T) - silver (Ag) - Syzygium cumini dye (SC) (Ti₃C₂Tx/Ag/SC – TASC) nanofluids, specifically engineered for augmenting the performance of single slope basin solar stills (SBS). Nanofluids were meticulously formulated at various volumetric concentrations of with and without TASC (0% (without TASC), 10%, 20%, and 30%) and subsequently subjected to precisely calibrated microwave exposure. We rigorously characterized TASC nanofluid thermophysical properties (thermal conductivity (λ), specific heat (C_p), viscosity (µ), density (ρ)) before and after microwave treatment. This SC absorption foster is improved and charge separation is enabling efficient photocatalytic degradation of crystal violet (94% at 0.0199 min^-¹) and phenol (83.9% at 0.0121 min^-¹). Microwave irradiation significantly boosts TASC nanofluids energy storage is enhancing colloidal stability and surface morphology. This elevates thermal conductivity and specific heat capacity, crucial for maximizing solar absorption. SC acts as a photosensitizer, while TA interactions, particularly with Ag doping, provide superior thermal energy transduction and buffering. The 30% TASC concentration dramatically improved thermal conductivity by 7% to 9.83%, alongside a 29.2% increase in the Nusselt number, signaling superior convective heat transfer. While kinematic viscosity rose by 23%, an entropy generation analysis confirmed that reduced temperature gradient irreversibility outweighed increased viscous dissipation, leading to a net heat transfer efficiency of 196.63 W/m²⋅K. These optimized nanofluids boast enhanced photothermal conversion and thermal energy retention, directly boosting solar distillation performance. The daily productivity of the SBS, with a 1.5 cm water depth, peaked at 5.34 L/m² with 30% TASC, significantly outperforming other concentrations (1.70 L/m² without TASC). This enhanced yield stems from the TASC's amplified thermal energy flux, which accelerates evaporation. SBS distillate was collected hourly (07:00–18:00) and overnight (18:00–06:00) to maximize output. Long-term trials (Sept 2024-Jan 2025) confirmed substantial improvements in average thermal efficiency of 52% with 30% TASC, compared to 19% without TASC. This consistently high efficiency at 30% TASC underscores its immense potential for sustainable desalination and water purification. The synergistic effect of boosted photothermal conversion, thermal retention, and evaporation profoundly enhanced distillate yield and overall system performance, even extending to off-sunshine hours. This research offers crucial insights into precise nanofluid engineering through microwave processing for next-generation solar applications.