Thermophysical analysis of acrylic pyramid solar still with and without Zn²⁺ substituted Cr₂O₃ nanoparticles had been analysed. Synthesised pure and Zn²⁺ doped Cr₂O₃ nanoparticle with different dopant concentrations is used along with the black absorber paint as an additional source in enhancing the heat transfer in the solar still. Heat transfer modes, efficiency (instantaneous and overall) and thermophysical properties are predicted for solar still with and without Zn2⁺ substituted Cr₂O₃ nanoparticles.

XRD confirms the rhombohedral phase with average particle size of pure and Zn doped Cr₂O₃ around ± 14 nm and ± 12 nm respectively. Surface morphology showed nearly spherical shape with loosely agglomerated and the presence of Cr and Zn was confirmed by EDAX analysis. Dielectric measurements showed enhanced dielectric constant and electrical conductivity as the function of temperature at different frequency range. Performance ratio observed during the study is in the range of 2.11 to 10.125 for solar still alone, 2.38 to 11.9 % for solar still with pure Cr₂O₃ nanomaterial, 2.38 % to 12.87 % for solar still with 2.5 mol.% Zn²⁺ doped Cr₂O₃ nanomaterial, 2.46 % to 13.22 % for solar still with 5 mol.% Zn²⁺ doped Cr₂O₃ nanomaterial and 2.54 % to 13.67 % for solar still combined with 7.5 mol.% Zn²⁺ doped Cr₂O₃ nanomaterial.

Average daily output of solar still was found to be 2.366 L/day, 3.147 L/day, 3.299 L/day, 3.3761 L/day and 3.628 L/day for pyramid solar still under five modes of study. Efficiency of the still was calculated as 18.29%, 21.15%, 21.88%, 22.32% and 23.48% for pyramid solar still under five modes of study. It is found that the productivity yield of solar still with 7.5 mol.% Zn²⁺ doped Cr₂O₃ nanomaterial is increased to higher level due to the increased absorption of solar radiation when compared to other modes of study.