Mathematical modeling and experimental validation for square pyramid solar still

This study presents a detailed mathematical model of the pyramid solar still which is not performed in most of the previous studies. Computer programs (in Pascal language) are developed for both studying thermal performance of the square pyramid solar still and estimating the hourly variations of the solar intensity incident on the tilted still's covers. Comparisons between the obtained theoretical results and experimental results (from previous work) are performed to validate the proposed mathematical model. The daily productivity of the pyramid solar still (P_d) varies from 4.22 to 4.43 kg/m² day with values of the glass cover's tilt angle of 10°–60°. P_d decreases from 3.88 to 1.52 kg/m² day with increasing the depth of the still's water (d_w) from 0.01 to 0.30 m. Values of the top losses of the still decrease from 8.8064 to 8.2304 W/m² K with increasing glass cover surface area from 0.063 to 0.125 m², which correspond to values of tilt angles of the still covers changing from 10° to 60°, respectively.