Intimately connected with the length of day and night are our seasons, especially summer and winter; for together with the sun's light heat is also called forth.

与白昼和黑夜的时间长度密切相关的是一年中的四季变化，最明显的是夏季和冬季的差别。其原因是太阳的光照和温度在同时发生作用。

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In the case of constant pipe diameter, lengthening the length of vacuum tube is an effective way to increase the total heat of solar water heater!

在管径恒定的情况下，加长真空管的长度是增加太阳能热水器总得热量的有效途径和方向！

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Analyze the effective length of thimble practice heat transfer.

分析得到了套管实际可换热的最大有效长度。

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