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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

Solar water heaters are used around the world and not very difficult to built.The system we are going to describe is base on the design some years ago.Since then it has been built in many countries.It can heat 70 liters of water to 60 degree (Celsius).It can do this between sunrise on the noon, on the clear day on average temperatur--temperature of 32 degrees Celsius.
There are two parts of solar water heater. One part is made by a sheet of metal paint black.Black surface became hotter in the sun than paint other color.This black metal plate is called collector.The collector is placed in contact with the water.There are several kind of metal heater can be used for the collector.Corrugated metal works very well. Corugate sheet metal are offen used as group on housing.Once the water is heated, it keep hot with ins--insulation  material.This allow water to stay warm for a long time.
The second part of the heater hold water for the system.This storage tank could be a container hold about 100 liters of water.Two (rubber) pipes are attached the storage tank. One pipe let water flow into the system.The other let water flow out.When water heater is working correctly,water will flow from storage to collector and back again. you can use the hot water on the top of the tank for washing and cleaning.You can change the flow of water so that the temperature could be hot or warm as desired.This water heater is easy to built and upgraded. It will last about two years before rubber pipes need to be replaced.There is also something else you will need to make solar water heater work. The sun as you might image that the heater will only heat water in sunny day.You can get more information about solar water heaters and other projects from enterprise works. this group internationally to fight poverty.The website is enterpriseworks.org. Choose the link for News & Resources, then click on Publications.

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