This will prevent heat transfer between air within and outside the ducts and condensation on ducts carrying cold air. With regard to materials used for ducts, the interiors should be smooth to keep resistance to air flow small.

• 这会防止管道内外空气间的热传导并避免传送冷空气的管道上发生冷凝现象。至于风道所用的材料,里面应当光滑,这样对气流的阻力就