Water preheater for small central heating boiler - has U=shaped finned heating tube located by flow baffles in flue duct section

摘要

The pre-heater assembly comprises a finned (1) water tube (2) contained within a flue duct section (6) and baffle plates (5) which are arranged in the space between the tube and the duct wall such that the flue gas follows a zig-zag path. The water tube consists of two parallel tube portions whose upper ends are connected (4) via a U-bend (3) whilst their lower ends connect to the heating return line (8) and the boiler respectively. Each baffle is shaped to cover half of the duct cross-section and has semi-circular cut-outs to accommodate the tubes (2) when placed between two adjoining tube fins (1) thus locating the tubes in the duct.