The utility model discloses an elbow and double -pipe heat exchanger relates to channel bend production, including the elbow main part, be provided with at least one breach on the segmental arc of elbow main part, each breach department forms the pipeline short circuit with elbow bulk phase intercommunication, and the pipeline short circuit is the same with the pipeline diameter of elbow main part, the free end of pipeline short circuit is provided with the sealing member. The utility model provides an elbow and double -pipe heat exchanger is provided with the pipeline short circuit in the elbow main part, in the elbow use, replace dismantling the elbow through the dismantlement sealing member and carry out observation and cleaning to the pipeline, has avoided the frequent dismantlement owing to the elbow, thereby the elbow easily produces the sealing performance after deformation influences elbow time dress, produces the problem of revealing, simultaneously, replace dismantling the elbow through the dismantlement sealing member and carry out observation and cleaning to the pipeline, reduced operating personnel's work load, shortened operating personnel's operating time, improved the work efficiency of operating personnel observation and washing pipeline.