| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1993: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1992: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
The evacuated solar still, which consists of solar collector, evaporator, condenser and storage tank for distillled water, is the solar distilllation - system in which the pressures is always kept low at about 2-3 kPa. This enables to maintain the boiling temperature of the saline water at lower level, besides the heat loss from the solar still to the ambient air and for using sensible heat can be minimized at such the lower temperature level.
Since the present solar-distilllation-system requires small temperature difference between evaporator stages, the present system is applicable to multi-stage system in order to achieve higher productivity.
Firstly, the proposed still has been tested for several temperature differences between the 1st and 2nd evaporator stage by means of a simple experimental simulation using electric heaters. It was confirmed that the temperature difference was small enough at about 5 K by the heater input of 900 W, so the present distilllation-system, bring into p
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ractice to multiple-effect system, was ascertained realizable with high efficiency.
Secondly, the double-effect evacuated-solar-still was designed and constructed. And then it was combined with the flat-plate solar-collector which has the surface area of 1.61 m^2 with inclination 30ﾟ, and was tested under the actual outdoor condition. It has produced 7.35 kg/(m^2*d) under the solar radiation of 14.9 MJ/(m^2*d), and the distilllation efficiency was found being 120 %. The results showed that the present system is one of the highest productivity and efficiency systems under the actual solar radiation.
In addition, a method of computer simulation about the present solar-still has been established, and the experimental result under the actual outdoor-condition was compared and discussed with the result of computer simulation. It was found that the reduced distilllation-efficiency was caused by increasing temperature of cooling water. It was concluded that the major problem was the solar-collector efficiency which is about 64 % being smaller than the expected efficiency. The improvement of the solar collector is necessary for the further development. Less
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