Gas fired central heating boiler - has closed spiral tubular inserts coaxially mounted inside heat exchanger tubes

摘要

The gas-fired boiler has a heat exchanger with horizontal tubes and inlet and outlet headers in the top part of the firebox. Inside the parallel tubes (1) of the heat exchanger (2) are inserts extending right through and formed by tubes (4) twisted to produce coarse-pitch spiral outer surfaces. The interior of these tubes is sealed off, and they are held coaxially to the tubes in which they are mounted, typically by devices (6) inside the heat exchanger inlet and outlet headers (7, 8).