Heat transfer studies on solar still assisted with and without latent heat storage material

The main objective of this work is to enhance the yield of solar still using the latent heat storage capacity of the phase change material (PCM) and to compare the distillate yield of PCM-assisted solar stills with that of the conventional solar still (Type A). In this regard, three solar stills of equal dimensions were designed, constructed and tested under identical weather conditions. In one of the solar still, 16 numbers of tubes having a diameter of 25.4 mm (Type B) were incorporated at basin, to accommodate the paraffin PCM, whereas in another solar still, PCM was embodied in between the annulus of the outer tube of diameter 31.75 mm and the inner tube of diameter 6.35 mm (Type C). The conventional solar still (Type A) was exclusively used for the comparison of the yield of the other two modified solar stills embodied with PCM. The daily freshwater productivity was 2.832 L/m(2)/d for Type C still, while the productivity of Type B and Type A still were 2.592 and 2.228 L/m(2)/d, respectively. This yield of Type C still corresponds to 6% and 27% higher than Type B and Type A stills, respectively. The higher yield in Type C still is due to the enhanced heat transfer surface and reduced thickness of the encapsulated PCM which offers less resistance compared with Type B solar still. Thus, it is construed that the geometry with PCM encapsulated in the annulus is the best option among the configuration considered.