45.某风管的断面尺寸为300mmx200mm,则该风管的当量直径是A 240mmB 250mmC 300mmD 200mm
45.某风管的断面尺寸为300mmx200mm,则该风管的当量直径是A 240mmB 250mmC 300mmD 200mm
发布时间:2025-06-05 04:53:07
45.某风管的断面尺寸为300mmx200mm,则该风管的当量直径是A 240mmB 250mmC 300mmD 200mm