Boiler surface may be defined as those parts of tubes, drums and shells which are part of the boiler circulatory system and which are in contact with the hot gases on one side and water or a mixture of water and staem on the other side.Although the term boiler may refer to the overall steam generating unit,the term "boiler surface" dose not include the economizer or any component other than the boiler itself.Boilers may be broadly classified as shell,fire-tube and water-tube types.

从外表看锅炉由连接一边是热气另一边是水与蒸气混合物的锅炉循环系统的管状，桶状设备和锅炉外壳组成的（蒸气应该是steam，而你写成了 staem，不认识）。虽然术语中锅炉是指整个蒸气生产装置，但是术语“锅炉表面”不包括节能装置或者除了锅炉本省以外的其他组件。人们一般把它分为锅壳型，烟管型和水冷管型等类型。(fire-tube是烟管或火管而不是导火管，water-tube是水冷管，不是导水管，classify应该是分类，而不是定义的意思)