Acute shortage of drinking water has been on the rise owing to increasing population as well as shortage of drinkable water. Generation of potable water using passive solar stills is among the simplest and easier devices which make use of solar heat energy. However, the output of solar still is generally low owing to greater heat loss and needs improvement. In this paper, an experimental analysis is carried out to determine the performance of passive solar still with glass cover cooling using cold water generated using passive evaporative cooling process. The cold water required for cooling the glass cover is obtained using evaporative cooling process in the water tank which is wound with wet cotton cloth wick. The cold water thus obtained is sprayed onto the top surface of glass cover. The experiment is carried out in the outdoor conditions of Dubai from 10:00h to 14:00h and the temperature recordings of basin plate, glass cover, basin water, ambient air and cooling water are noted for every 30 minutes. The results reveal that the average increase in condensation heat transfer coefficient is found to be about 20.8% higher in the presence of glass cover cooling and the distillate output is found to increase by about 3.32 times. The average still efficiency is found to be relatively higher in the presence of cooling which is about 7.3% higher in the presence of cooling. The cold water temperature generated through evaporative cooling process is about 20.4% lower as compared to ambient temperature. Thus, the cooling of glass cover using cold water obtained through evaporative cooling process is found to be effective in enhancing the thermal performance of single basin solar still system.
A literature review carried out by the authors reveals that that a CFD analysis has not been the focus of attention to evaluate the efficacy of turbulators for improving the thermal performance of solar air heaters. A three dimensional CFD analysis is carried out in the present work to augment the performance of solar air heater. Arc shaped wire turbulators (with forward and reverse curvature aligned with flow direction), V-shaped wire turbulators (with forward and reverse geometry with respect to the flow direction) and Straight turbulators are used in this study to improve the flow turbulence and thereby enhance the convective heat transfer to air. The numerical results are validated with experimental results for model without turbulator to calibrate the numerical methodology. The numerical results show that turbulators whether curved or straight are useful in enhancing the heat transfer rates. The Arc shaped turbulators have been found to provide better heat transfer coefficient value compared to that of straight and V-shape turbulators. Also interestingly, Reverse arc turbulators seems to provide better heat transfer coefficient value compared to forward arc turbulators. Further, V-angle has no significant effect for both forward and reverse V-turbulator configurations.
Thermosyphon unglazed solar flat plate collectors have been widely used all over the world to harness solar energy for generating hot water for various applications. This is mainly due to the passive nature of the system besides being simple in design. However, flat plate collectors are associated with higher heat losses from the surface leading to lower thermal performance. Hence, there is a dire need to optimize the thermal design aspects of the flat plate collector in order to achieve higher thermal performance. In this paper, the results of a full three dimensional CFD simulation of thermosyphon flow in an unglazed solar flat plate collector are presented. It is observed from the parametric study that there are interesting trends for the temperature distribution of the absorber plate and loop water for various simulated solar heat flux inputs. This analysis also brings out the effect of various simulated heat fluxes on the mass flow rates in the collector loop. The results of this CFD simulation study provide an insight into the behavior of the thermosyphon solar flat plate collector under various operating conditions and hence will be further helpful to undertake optimization for enhanced thermal performance of the collector.
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