题干

随着世界性能源危机的日益加剧,一向为人们所唾弃的垃圾也身价倍增,变成了能源再生的“宝库”.利用垃圾的一种方式就是将垃圾填埋后,通过厌氧发酵产生沼气,这些沼气燃烧,产生高温燃气,推动汽轮机转动,汽轮机驱动发电机来发电.

(1)根据上面的短文,请你将垃圾发电过程中的能量转化填写完整.

(2)若每吨填埋垃圾可产生沼气150m3,集中收集后可发电250kW•h.巳知沼气的主要成分是甲烷,其热值为2.0×107J/m3,则沼气发电的效率为多少?

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答案(点此获取答案解析)

解:(1)燃料的化学能通过燃烧转化为内能,又通过机器做功,把内能转化为机械能,然合带动发电机发电,使机械能转化为电能.

(2)η=可求出η=

同类题5

阅读下列短文,从每题所给的四个选项(A、B、C和D)中,选出最佳选项。

    It was a bad time for me. I was low emotionally and tired physically. Probably because of this I hadn't shaved for a few days. Also, because I had been doing some repairs at my daughter's house, I was dressed quite scruffily(不整洁地). Boarding the bus to go home I saw it was almost full so I found a rail(扶手) to lean against.

    That's when a young woman, sitting with her child, stood up and offered me her seat. ‘Wow!' I thought. Out loud I said, “Do I look that old and tired?” She replied, “You look like you've had a tough day.” I thanked her sincerely and stayed standing.

    A moment later a man rose from his seat at the back of the bus and made his way towards me, walking past several people on the way. Then he told me about his addiction(毒瘾) problems, asked my advice, and just chatted about life for a few minutes. Then he went back to his seat. Very random!

    Watching him go, I also looked at the bus-load of people between me and his seat. He hadn't chosen to talk to those strangers. He chose to talk to this stranger, for whatever it meant to him and whatever comfort it brought him. Why?

    That's when it occurred to me. I must have looked like I had been where he was. I probably looked like a man who would understand a difficult life. I was humbled(谦卑的) and encouraged at the same time by the realization that even when we are at our lowest we can still help others — if we look like we might be able to meet them where they live or walk a while in their world.