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本题添加时间：2023/7/16 8:20:00 |
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At given temperature and pressure, a fluid possesses a definite density, which in engineering practice is usually measured in kilograms per cubic meter. Although the density of all fluids depends on the temperature and pressure, the variation in density with changes in these variables may be small or large. If the density changes only slightly with moderate changes in temperature and pressure, the fluid is said to be incompressible; if the changes in density are significant, the fluid is said to be compressible. Liquids are generally considered to be incompressible and gases compressible. The terms are relative, however, and the density of a liquid can change appreciably if pressure and temperature are changed over wide limits. Also, gases subjected to small percentage changes in pressure and temperature act as incompressible fluids and density changes under such conditions may be neglected without serious error.
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答案是:在一定的温度和压力下,流体具有确定的密度,工程上用kg/m3表示。尽管流体的密度与温度和压力有关,但随温度和压力变化,密度的变化有大有小。如果温度和压力发生明显变化,但密度的变化很小,则该流体称之为不可压缩流体;相反,如果密度的变化非常明显,则该流体称之为可压缩流体。一般认为液体为不可压缩流体,气体为可压缩流体。不过,这种概念是相对的。如果压力和温度的变化范围非常宽,液体的密度也许会发生明显变化。有时,随温度和压力的变化气体的密度变化较小,此时气体可作为不可压缩流体对待，密度的变化可忽略不计,在工程上不会引起大的偏差。
出自
乐山师范学院专业英语 A卷 文鼎教育系统
乐山师范学院
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