�~�� 發問時間: 科學其他:科學 · 9 年前

請問鋁罐降溫的原理+洞(看報導就會瞭)

http://www.worldpeoplenews.com/news/10/2011-07/150...

這是資料 洞要打在哪裡?? 打幾個?? +原理 謝謝了 幫幫忙

1 個解答

評分
  • 9 年前
    最佳解答

    The principle is 2 of the 3 heater transfer methods:

    (1)conduction

    (2)convection

    (3)radiation.

    It uses both conduction and convection. Let me explain as follows:

    When sun hit the roof, roof will absorb the heat, so the surface of the roof is warmer than the surrounding air. By placing the aluminum cans on the roof, they can conduct heat from the roof to the cans (thermodynamics principle says: heat will flow from high to low). Now, how can these cans reduce its heat. this is why they punch holes on the cans. These hoes allow air to flow through and remove (by convection) the heat transferred from the roof (by conduction). As the heat from the roof got removed, it cools down the roof. However, it can only cool down to the same temperature as the surrounding air.

    Now, where to punch the holes? These holes have TWO purposes: (1)to allow air flow, (2)to let rain water leave (otherwise it will cumulate too much rain and cause problem). Basically, you only need to punch one hole on the top and the bottom, and no more than 4 holes on the side of the can. The size of the hole shall be at least half inches (about 2.5 cm). If you like, you can make the hole faced upward bigger to increase the air flow (for better convection).

    I am not able to type in Chinese, hopefully, you can understand my English. If you don't like English answer, please let me know, I will remove it !

    參考資料: self
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