知乎,中文互联网高质量的问答社区和创作者聚集的原创内容平台,于 2011 年 1 月正式上线,以「让人们更好的分享知识、经验和见解,找到自己的解答」为品牌使命。知乎凭借认真、专业. 管道标注dn、de、、φ、d、d区别: dn是指管道的 公称直径,注意:这既不是外径也不是内径,是外径与内径的 平均值,称平均内径。如:dn200~φ219×6 d一般指管道内径。 d 混凝土.
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