Efficient utilization of nanofluids in shell-and-tube heat exchangers for solar thermal energy systems requires a rigorous sensitivity analysis, enabling fine-tuning design parameters to achieve optimal heat transfer performance and overall system efficiency. Previous research has primarily focused on utilizing nanofluids to enhance heat transfer in solar thermal systems, emphasizing nanoparticle selection, optimization techniques, and sensitivity analysis. The central concern addressed by this study is the development of an optimal shell-and-tube heat exchanger (STHE) configuration employing nanofluids within a solar thermal energy framework. The research uses statistical modeling to analyze the interplay between heat transfer coefficients, pressure drops, and shell dimensions in nanoscale heat exchanger construction. Utilizing computational fluid dynamics (CFD) simulations, the study investigates flow patterns and temperature distributions within the heat exchanger, considering variations in hot water flow rates, initial dimensions, cold-water flow rates, and tube geometries for optimization. The findings underscore the positive impact of increased cold-water flow rates on efficiency and total heat transfer coefficients, while longer initial dimensions result in decreased efficiency. Regarding sustainability, corrugated tubes are superior to smooth tubes, shedding light on the relationship between energy efficiency and sustainability in this context.