Presents the energy saving principle of a frequency-controlled pump and points out the applicability of the law of similitude for centrifugal pumps and the conception of constant efficiency curves.

阐述了循环 水泵变频调速的节能原理，提出 离心 水泵相似定律的适用性和等效率曲线概念。

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For even greater efficiency consider buying a tankless water heater. Tankless water heaters only heat water when it is needed, instead of keeping a reserve of water at a constant temperature.

购买无水箱热水器（电热水器）是更加节能的做法，电热水器只在需要的时候对水进行加热，而不会对保存在水箱内的水加热保温。

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Slow efficiency at threshold is observed to be nearly constant over the wide range.

在广域范围内观测到的低效阈值近似为常数。

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The struggle to improve efficiency and cut costs is a constant irritant in labor- management relations.

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Not only did he fail to carry his weight, he was a constant and serious drain on the Army's efficiency.

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