Experimental investigation of the effect of using water and ethanol as working fluid on the performance of pyramid-shaped solar still integrated with heat pipe solar collector

In this paper, a modified pyramid-shaped solar still (MPSS) including a conventional pyramid-shaped solar still (CPSS) integrated with a heat pipe solar collector (HPSC) was fabricated and experimentally assessed in the outdoor conditions of Mashhad, Iran (latitude of 36 degrees 18', longitude of 59 degrees 34'). Two different working fluids (water and ethanol) were used at three different filling ratios (FRs). Results showed that using the HPSC increased the temperature difference between the glass cover and the basin water. Therefore, using the HPSC augmented the hourly and accumulated yield. The accumulated yield was escalated to 6970 and 3300 ml/m(2) for the MPSS (with water as the working fluid at the FR of 40%) and the CPSS, respectively. Moreover, the HPSC increased exergy, although the instantaneous efficiency was rather invariant. Based on the experimental data the values of the total internal heat transfer coefficient have been calculated. Furthermore, the best performance of the MPSS was obtained with water as the working fluid at the FR of 40% whereas ethanol at the FR of 40% also showed a very good performance. Finally, the economic analysis revealed that the MPSS was economically reasonable and an estimated cost for 1 L of distillate was 0.0137 $ for the proposed MPSS.