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. 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.
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