| abstract |
A method for the recovery of heat from exhaust gas discharging through the flue of a hot water boiler (e.g. in a central heating system, Figure 3) comprises circulating a fluid (e.g. the water passing to the boiler) through a heat exchange passage arranged in heat exchange relation with the flue gas. Said passage may comprise an annular space 6 in a concentric tube heat exchanger Figure 1 sealed at its ends into the flue. Or the passage may be formed in a box structure 21 attached alongside the flue, Figure 5. Fins 3, Figure 1 or 26, Figure 5, assist heat transfer. <IMAGE> |