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[report整理] SENEWS-2011-04-25

提高英语听力能力 找对方法很重要!

[Homework]SENEWS-2011-04-25

Soalar water heaters are used aroung the world and are not very difficult to buid. The system we are going to describe is based on the design developed some years ago in Afganistan. Since then it has been built and used in many countries. It can heat 70 litres of water to 60 degrees celcius. It can do this between sunrise and noon on a clear day with average air tempreture of 32 degrees celcius. There are two parts of the soalar water heater. One part is made of a sheet of metal painted black. Black surfaces become hotter in the sun than surfaces painted in the other color. This black metal plate is called a collector. The collector is placed in contact with the water. There are several times of metal sheets that can be used for the collector. Corigated metal will work very well. Corigated sheets are often used as roofs on housing. Once the water is heated, it is kept hot with insolation material. This allows the water to stay warm for a long time. The second part of the soalar water heater holds the water for the system. This storage tank can be a container that holds about 100 litres. Two rubber pipes are retach to the water storage tank. One pipe lets water flow into the system, the other lets water flow out. When the water heater is working correctly, water will flow from the storage tank to the collector and back again. You can use the hot water at the top of the tank for washing and cleaning. You can change the flow of water so that the tempreture is hot or warm as designed. This soalar water heater is easy to build and operate. It will last about 2 years before the rubber pipes need to be replaced. There is also something else you will need to make the soalar water heater work, the sun, as you might imagine, the heater will heat water only on sunny days. You can get more information about soalar water heaters and other projects from interprice works viter. This group works internationally to fight property. The web site is interprice works.org. Choose the link for news and resources then click on publications.
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