DESIGN FABRICATION AND ANALYSIS OF A BASIN TYPE SOLAR WATER STILL
Team: Ajo Thomas
Anil N Sahodaran
Neeraj Nair Padmakumar
Guide: Mr. Pradeepmon.T.G, lecturer, Mechanical department,
AIM OF THE PROJECT
The project aims at evolving a simple and economic
design for the basin type water still. Special attention is paid
towards its functional and economic viability. A thorough
analysis of the design has been carried out.
Â¢ Evaporation is the slow vaporization of a liquid and the reverse of condensation. A type of phase transition, it is the process by which molecules in a liquid state (e.g. water) spontaneously become gaseous (e.g. water vapor). Generally, evaporation can be seen by the gradual disappearance of a liquid from a substance when exposed to a significant volume of gas.
FACTORS INFLUENCING THE RATE OF EVAPORATION:
Â¢ Concentration of the substance evaporating in the air
Â¢ Concentration of other substances in the air
Â¢ Concentration of other substances in the liquid (impurities)
Â¢ Flow rate of air
Â¢ Inter-molecular forces
Â¢ Surface area
Â¢ Temperature of the substance
Â¢ To purify:
1. Brackish water
2. Sea water
3. Pond water, murky water from wells etc.
Â¢ Ease of installation, maintenance and use.
Â¢ Economy is an equally important criterion.
DESIGN OBJECTIVES FOR AN EFFICIENT SOLAR STILL
Â¢ For high efficiency the solar still should maintain:
â€œ A high feed (undistilled) water temperature.
â€œ A large temperature difference between feed water and condensing surface.
â€œ Low vapour leakage.
Â¢ A high feed water temperature can be achieved if:
â€œ A high proportion of incoming radiation is absorbed by the feed water as heat.
â€œ Heat losses are kept low
â€œ The water is shallow so there is not so much to heat.
Â¢ A large temperature difference can be achieved if:
â€œ The condensing surface absorbs least radiation
â€œ Condensing water dissipates heat rapidly.
Â¢ The entire apparatus is made of glass having a transmissivity of 70%.
Â¢ Black limestone (Kadappa stone) as a heat absorber.
Â¢ Coir as insulator.
Â¢ Collectors: Two sheets of thin glass of 135cm x 75cm arranged symmetrically over the side walls like a roof act as the collectors cum condensing surfaces.
Â¢ Aluminium fittings.
Â¢ Special silicone-based glue is used for sticking glass.
SOLAR RADIATION ON TILTED SURFACES USING EMPIRICAL RELATIONS
Â¢ The ratio of the radiation flux falling on a tilted surface to that falling on a horizontal surface is called the tilt factor ®
Â¢ Tilt factors for each kind of the following radiations exist:
â€œ Beam Radiation
â€œ Diffuse Radiation
â€œ Reflected Radiation
Â¢ The market for the product includes whole of rural Indian population and some of the water scarce urban areas like Chennai.
Â¢ This comprises around 70% of Indiaâ„¢s population; the exact number being 70 cores.
Â¢ Assuming around 10 % of them will actually be interested in buying this product the demand for the product is 70 x 0.1 = 1.4 crore units.
Â¢ This makes the market size to come up to around Rs 140 crore.