题干

小聪家购买了一台“太阳帆”牌太阳能热水器,他看到这款热水器的参数如下:

真空管直径×长度(mm)

70×1800

规格(支管)

15

外形尺寸(mm)

1840×1597×1765

保温层(mm)

60

水箱容量(L)

150

采光面积(m2

2.1

(1)假设太阳光的日照强度为3×l06J/( m2•h)(日照强度表示每平方米面积上1h得到的太阳光的能量).若每天接收太阳能的时间以8h计算,热水器能把接收到的太阳能的50%转变成水的内能.请问:正常光照下一天内该热水器能让初温为20℃的一箱水温度升高多少摄氏度?(水的比热容为c=4.2×l03J/(kg•℃))

(2)如果换用一台标有“220V 1500W”的电热水器在额定电压下工作,把同样的一箱水加热升高相同的温度需要5h,则电热水器的加热效率多大?

(3)如果换用煤气灶烧水,把同样的一箱水加热升高到相同的温度需要多少煤气?(已知煤气的热值q=4.2×l07J/kg)

上一题 下一题 0.0难度 选择题 更新时间:2018-06-08 10:10:29

答案(点此获取答案解析)

解:(1)太阳能热水器8h接受的太阳能为E=P0St=3×l06J/( m2•h)×2.1m2×8h=5.04×107J

水箱中水的质量为:m=ρV=1×l03kg/m3×150×10﹣3m3=150kg

又效率为50%,则水吸收的热量为:Q=Eη=5.04

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