S. Kalaivani, S. Rugmini Radhakrishnan
Abstract: In this communication, an attempt has been made to find out the heat transfer coefficients such as internal and external heat transfer modes and thermophysical properties such as dynamic viscosity, density, thermal conductivity, latent heat of evaporation and saturated vapor pressure for active solar distillation system. It is observed that water temperature plays a vital role in the distillate output (the yield) since it increases significantly with the rise of basin water temperature. Double slope step type solar still of area 1 m2 is constructed using a glass pieces. Top Glass cover with 10 slope ensures a very good transmission of solar radiation inside the still. The distillate water productivity is in the range of 2.758 litres to 2.805 liters per day for still performance study. Similarly the instantaneous efficiency for still performance study is in the range of 17.84 % to18.25 %. Dimensionless numbers such as the Nusselt number (Nu), the Grashof number (Gr), the Reynolds number (Re) and the Prandtl number (Pr) were also estimated. Heat transfer coefficient were estimated for the present system since the system overall efficiency depend on heat transfer modes. Internal (convection, evaporation and radiation) and external (convection, conduction and radiation) heat transfer modes were calculated for the present system and it is found that because of rise in water temperature, evaporative heat transfer coefficient value rises significantly.
Keywords: Solar Still, Heat Transfer Modes, Radiation, Acrylic, Distillate Yield, Efficiency